diff --git a/doc/draft/draft-baba-dnsext-acl-reqts-01.txt b/doc/draft/draft-baba-dnsext-acl-reqts-01.txt deleted file mode 100644 index 1030e5782e..0000000000 --- a/doc/draft/draft-baba-dnsext-acl-reqts-01.txt +++ /dev/null @@ -1,336 +0,0 @@ - - - - -Internet-Draft T. Baba -Expires: March 11, 2004 NTT Data - September 11, 2003 - - - Requirements for Access Control in Domain Name Systems - draft-baba-dnsext-acl-reqts-01.txt - -Status of this Memo - - This document is an Internet-Draft and is subject to all provisions - of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/1id-abstracts.html - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html - - Distribution of this memo is unlimited. - - This Internet-Draft will expire on March 11, 2004. - -Abstract - - This document describes the requirements for access control - mechanisms in the Domain Name System (DNS), which authenticate - clients and then allow or deny access to resource records in the - zone according to the access control list (ACL). - -1. Introduction - - The Domain Name System (DNS) is a hierarchical, distributed, highly - available database used for bi-directional mapping between domain - names and IP addresses, for email routing, and for other information - [RFC1034, 1035]. DNS security extensions (DNSSEC) have been defined - to authenticate the data in DNS and provide key distribution services - using SIG, KEY, and NXT resource records (RRs) [RFC2535]. - - - -Baba Expires March 11, 2004 [Page 1] - -Internet-Draft DNS Access Control Requirements September 2003 - - - At the 28th IETF Meeting in Houston in 1993, DNS security design team - started a discussion about DNSSEC and agreed to accept the assumption - that "DNS data is public". Accordingly, confidentiality for queries - or responses is not provided by DNSSEC, nor are any sort of access - control lists or other means to differentiate inquirers. However, - about ten years has passed, access control in DNS has been more - important than before. Currently, new RRs are proposed to add new - functionality to DNS such as ENUM [RFC2916]. Such new RRs may - contain private information. Thus, DNS access control will be - needed. - - Furthermore, with DNS access control mechanism, access from - unauthorized clients can be blocked when they perform DNS name - resolution. Thus, for example, Denial of Service (DoS) attacks - against a server used by a closed user group can be prevented using - this mechanism if IP address of the server is not revealed by other - sources. - - This document describes the requirements for access control - mechanisms in DNS. - -2. Terminology - - AC-aware client - This is the client that understands the DNS access control - extensions. This client may be an end host which has a stub - resolver, or a cashing/recursive name server which has a - full-service resolver. - - AC-aware server - This is the authoritative name server that understands the DNS - access control extensions. - - ACE - An Access Control Entry. This is the smallest unit of access - control policy. It grants or denies a given set of access - rights to a set of principals. An ACE is a component of an ACL, - which is associated with a resource. - - ACL - An Access Control List. This contains all of the access control - policies which are directly associated with a particular - resource. These policies are expressed as ACEs. - - Client - A program or host which issues DNS requests and accepts its - responses. A client may be an end host or a cashing/recursive name - server. - - - -Baba Expires March 11, 2004 [Page 2] - -Internet-Draft DNS Access Control Requirements September 2003 - - - RRset - All resource records (RRs) having the same NAME, CLASS and TYPE - are called a Resource Record Set (RRset). - -3. Requirements - - This section describes the requirements for access control in DNS. - -3.1 Authentication - -3.1.1 Client Authentication Mechanism - - The AC-aware server must identify AC-aware clients based on IP - address and/or domain name (user ID or host name), and must - authenticate them using strong authentication mechanism such as - digital signature or message authentication code (MAC). - - SIG(0) RR [RFC2931] contains a domain name associated with sender's - public key in its signer's name field, and TSIG RR [RFC2845] also - contains a domain name associated with shared secret key in its key - name field. Each of these domain names can be a host name or a user - name, and can be used as a sender's identifier for access control. - Furthermore, SIG(0) uses digital signatures, and TSIG uses MACs for - message authentication. These mechanisms can be used to authenticate - AC-aware clients. - - Server authentication may be also provided. - -3.1.2 End-to-End Authentication - - In current DNS model, caching/recursive name servers are deployed - between end hosts and authoritative name servers. Although - authoritative servers can authenticate caching/recursive name servers - using SIG(0) or TSIG, they cannot authenticate end hosts behind them. - For end-to-end authentication, the mechanism for an end host to - discover the target authoritative name server and directly access to - it bypassing caching/recursive name servers is needed. For example, - an end host can get the IP addresses of the authoritative name - servers by retrieving NS RRs for the zone via local caching/recursive - name server. - - In many enterprise networks, however, there are firewalls that block - all DNS packets other than those going to/from the particular - caching/recursive servers. To deal with this problem, one can - implement packet forwarding function on the caching/recursive servers - and enable end-to-end authentication via the caching/recursive - servers. - - - - -Baba Expires March 11, 2004 [Page 3] - -Internet-Draft DNS Access Control Requirements September 2003 - - -3.1.3 Authentication Key Retrieval - - Keys which are used to authenticate clients should be able to be - automatically retrieved. The KEY RR is used to store a public key - for a zone or a host that is associated with a domain name. SIG(0) - RR uses a public key in KEY RR for verifying the signature. If - DNSSEC is available, the KEY RR would be protected by the SIG RR. - KEY RR or newly defined RR can be used to automatic key retrieval. - -3.2 Confidentiality - -3.2.1 Data Encryption - - To avoid disclosure to eavesdroppers, the response containing the - RRsets which are restricted to access from particular users should be - encrypted. Currently, no encryption mechanism is specified in DNS. - Therefore, new RRs should be defined for DNS message encryption. - Instead, IPsec [RFC2401] can be used to provide confidentiality if - name server and resolver can set up security associations dynamically - using IPsec API [IPSECAPI] when encryption is required. - - In case encryption is applied, entire DNS message including DNS - header should be encrypted to hide information including error code. - - Query encryption may be also provided for hiding query information. - -3.2.2 Key Exchange - - If DNS message encryption is provided, automatic key exchange - mechanism should be also provided. [RFC2930] specifies a TKEY RR - that can be used to establish and delete shared secret keys used by - TSIG between a client and a server. With minor extensions, TKEY can - be used to establish shared secret keys used for message encryption. - -3.2.3 Caching - - The RRset that is restricted to access from particular users must not - be cached. To avoid caching, the TTL of the RR that is restricted to - access should be set to zero during transit. - -3.3 Access Control - -3.3.1 Granularity of Access Control - - Control of access on a per-user/per-host granularity must be - supported. Control of access to individual RRset (not just the - entire zone) must be also supported. However, SOA, NS, SIG, NXT, - KEY, and DS RRs must be publicly accessible to avoid unexpected - results. - - -Baba Expires March 11, 2004 [Page 4] - -Internet-Draft DNS Access Control Requirements September 2003 - - -3.3.2 ACL Representation - - Access Control List (ACL) format must be standardized so that both - the primary and secondary AC-aware servers can recognize the same - ACL. Although ACL may appear in or out of zone data, it must be - transferred to the secondary AC-aware server with associated zone - data. It is a good idea to contain ACL in zone data, because ACL can - be transferred with zone data using existing zone transfer mechanisms - automatically. However, ACL must not be published except for - authorized secondary master servers. - - In zone data master files, ACL should be specified using TXT RRs or - newly defined RRs. In each access control entry (ACE), authorized - entities (host or user) must be described using domain name (host - name, user name, or IP address in in-addr.arpa/ip6.arpa format). - There may be other access control attributes such as access time. - - It must be possible to create publicly readable entries, which may be - read even by unauthenticated clients. - -3.3.3 Zone/ACL Transfer - - As mentioned above, ACL should be transferred from a primary AC-aware - server to a secondary AC-aware server with associated zone data. - When an AC-aware server receives a zone/ACL transfer request, the - server must authenticate the client, and should encrypt the zone - data and associated ACL during transfer. - -3.4 Backward/co-existence Compatibility - - Any new protocols to be defined for access control in DNS must be - backward compatible with existing DNS protocol. AC-aware servers - must be able to process normal DNS query without authentication, and - must respond if retrieving RRset is publicly accessible. - - Modifications to root/gTLD/ccTLD name servers are not allowed. - -4. Security Considerations - - This document discusses the requirements for access control - mechanisms in DNS. - -5. Acknowledgements - - This work is funded by the Telecommunications Advancement - Organization of Japan (TAO). - - The author would like to thank the members of the NTT DATA network - security team for their important contribution to this work. - - -Baba Expires March 11, 2004 [Page 5] - -Internet-Draft DNS Access Control Requirements September 2003 - - -6. References - - [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", - STD 13, RFC 1034, November 1987. - - [RFC1035] Mockapetris, P., "Domain names - implementation and - specification", STD 13, RFC 1035, November 1987. - - [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the - Internet Protocol", RFC 2401, November 1998. - - [RFC2535] Eastlake, D., "Domain Name System Security Extensions", - RFC 2535, March 1999. - - [RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington, - "Secret Key Transaction Authentication for DNS (TSIG)", - RFC 2845, May 2000. - - [RFC2916] Faltstrom, P., "E.164 number and DNS", RFC 2916, - September 2000. - - [RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY RR)", - RFC 2930, September 2000. - - [RFC2931] Eastlake, D., "DNS Request and Transaction Signatures - (SIG(0)s)", RFC 2931, September 2000. - - [IPSECAPI] Sommerfeld, W., "Requirements for an IPsec API", - draft-ietf-ipsp-ipsec-apireq-00.txt, June 2003, Work in - Progress. - - -Author's Address - - Tatsuya Baba - NTT Data Corporation - Research and Development Headquarters - Kayabacho Tower, 1-21-2, Shinkawa, Chuo-ku, - Tokyo 104-0033, Japan - - Tel: +81 3 3523 8081 - Fax: +81 3 3523 8090 - Email: babatt@nttdata.co.jp - - - - - - - - -Baba Expires March 11, 2004 [Page 6] diff --git a/doc/draft/draft-daigle-napstr-04.txt b/doc/draft/draft-daigle-napstr-04.txt deleted file mode 100644 index fffa8a5f20..0000000000 --- a/doc/draft/draft-daigle-napstr-04.txt +++ /dev/null @@ -1,1232 +0,0 @@ - - -Network Working Group L. Daigle -Internet-Draft A. Newton -Expires: August 15, 2004 VeriSign, Inc. - February 15, 2004 - - - Domain-based Application Service Location Using SRV RRs and the - Dynamic Delegation Discovery Service (DDDS) - draft-daigle-napstr-04.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on August 15, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2004). All Rights Reserved. - -Abstract - - This memo defines a generalized mechanism for application service - naming that allows service location without relying on rigid domain - naming conventions (so-called name hacks). The proposal defines a - Dynamic Delegation Discovery System (DDDS) Application to map domain - name, application service name, and application protocol to target - server and port, dynamically. - - - - - - - -Daigle & Newton Expires August 15, 2004 [Page 1] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2. Straightforward-NAPTR (S-NAPTR) Specification . . . . . . . 4 - 2.1 Key Terms . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2.2 S-NAPTR DDDS Application Usage . . . . . . . . . . . . . . . 5 - 2.2.1 Ordering and Preference . . . . . . . . . . . . . . . . . . 5 - 2.2.2 Matching and non-Matching NAPTR Records . . . . . . . . . . 5 - 2.2.3 Terminal and Non-Terminal NAPTR Records . . . . . . . . . . 5 - 2.2.4 S-NAPTR and Successive Resolution . . . . . . . . . . . . . 6 - 2.2.5 Clients Supporting Multiple Protocols . . . . . . . . . . . 6 - 3. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 3.1 Guidelines for Application Protocol Developers . . . . . . . 7 - 3.1.1 Registration of application service and protocol tags . . . 7 - 3.1.2 Definition of conditions for retry/failure . . . . . . . . . 8 - 3.1.3 Server identification and handshake . . . . . . . . . . . . 8 - 3.2 Guidelines for Domain Administrators . . . . . . . . . . . . 8 - 3.3 Guidelines for Client Software Writers . . . . . . . . . . . 9 - 4. Illustrations . . . . . . . . . . . . . . . . . . . . . . . 9 - 4.1 Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 4.2 Service Discovery within a Domain . . . . . . . . . . . . . 10 - 4.3 Multiple Protocols . . . . . . . . . . . . . . . . . . . . . 10 - 4.4 Remote Hosting . . . . . . . . . . . . . . . . . . . . . . . 11 - 4.5 Sets of NAPTR RRs . . . . . . . . . . . . . . . . . . . . . 12 - 4.6 Sample sequence diagram . . . . . . . . . . . . . . . . . . 12 - 5. Motivation and Discussion . . . . . . . . . . . . . . . . . 14 - 5.1 So, why not just SRV records? . . . . . . . . . . . . . . . 15 - 5.2 So, why not just NAPTR records? . . . . . . . . . . . . . . 15 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16 - 7. Security Considerations . . . . . . . . . . . . . . . . . . 16 - 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 - References . . . . . . . . . . . . . . . . . . . . . . . . . 17 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 18 - A. Application Service Location Application of DDDS . . . . . . 18 - A.1 Application Unique String . . . . . . . . . . . . . . . . . 18 - A.2 First Well Known Rule . . . . . . . . . . . . . . . . . . . 18 - A.3 Expected Output . . . . . . . . . . . . . . . . . . . . . . 18 - A.4 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 - A.5 Service Parameters . . . . . . . . . . . . . . . . . . . . . 19 - A.5.1 Application Services . . . . . . . . . . . . . . . . . . . . 19 - A.5.2 Application Protocols . . . . . . . . . . . . . . . . . . . 20 - A.6 Valid Rules . . . . . . . . . . . . . . . . . . . . . . . . 20 - A.7 Valid Databases . . . . . . . . . . . . . . . . . . . . . . 20 - B. Pseudo pseudocode for S-NAPTR . . . . . . . . . . . . . . . 20 - B.1 Finding the first (best) target . . . . . . . . . . . . . . 20 - B.2 Finding subsequent targets . . . . . . . . . . . . . . . . . 21 - Full Copyright Statement . . . . . . . . . . . . . . . . . . 23 - - - - -Daigle & Newton Expires August 15, 2004 [Page 2] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -1. Introduction - - This memo defines a generalized mechanism for application service - naming that allows service location without relying on rigid domain - naming conventions (so-called name hacks). The proposal defines a - Dynamic Delegation Discovery System (DDDS -- see [6]) Application to - map domain name, application service name, and application protocol - to target server and port, dynamically. - - As discussed in Section 5, existing approaches to using DNS records - to dynamically determining the current host for a given application - service are limited in terms of the use cases supported. To address - some of the limitations, this document defines a DDDS Application to - map service+protocol+domain to specific server addresses using both - NAPTR [7] and SRV ([5]) DNS resource records. This can be viewed as - a more general version of the use of SRV and/or a very restricted - application of the use of NAPTR resource records. - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in RFC2119 ([2]). - -2. Straightforward-NAPTR (S-NAPTR) Specification - - The precise details of the specification of this DDDS application are - given in Appendix A. This section defines the usage of the DDDS - application. - -2.1 Key Terms - - An "application service" is a generic term for some type of - application, indpendent of the protocol that may be used to offer it. - Each application service will be associated with an IANA-registered - tag. For example, instant messaging is a type of application - service, which can be implemented by many different application-layer - protocols, and the tag "IM" (used as an illustration here) could be - registered for it. - - An "application protocol" is used to implement the application - service. These are also associated with IANA-registered tags. In - the case where multiple transports are available for the application, - separate tags should be defined for each transport. - - The intention is that the combination of application service and - protocol tags should be specific enough that finding a known pair - (e.g., "IM:ProtC") is sufficient for a client to identify a server - with which it can communicate. - - - - -Daigle & Newton Expires August 15, 2004 [Page 3] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - Some protocols support multiple application services. For example, - LDAP is an application protocol, and can be found supporting various - services (e.g., "whitepages", "directory enabled networking", etc). - -2.2 S-NAPTR DDDS Application Usage - - As outlined in Appendix A, NAPTR records are used to store - application service+protocol information for a given domain. - Following the DDDS standard, these records are looked up, and the - rewrite rules (contained in the NAPTR records) are used to determine - the successive DNS lookups, until a desirable target is found. - - For the rest of this section, refer to the set of NAPTR resource - records for example.com shown in the figure below. - - example.com. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "" "WP:whois++" "" bunyip.example. - IN NAPTR 100 20 "s" "WP:ldap" "" _ldap._tcp.myldap.example.com. - IN NAPTR 200 10 "" "IM:protA" "" someisp.example. - IN NAPTR 200 30 "a" "IM:protB" "" myprotB.example.com. - - -2.2.1 Ordering and Preference - - A client retrieves all of the NAPTR records associated with the - target domain name (example.com, above). These are to be sorted in - terms of increasing ORDER, and increasing PREF within each ORDER. - -2.2.2 Matching and non-Matching NAPTR Records - - Starting with the first sorted NAPTR record, the client examines the - SERVICE field to find a match. In the case of the S-NAPTR DDDS - application, that means a SERVICE field that includes the tags for - the desired application service and a supported application protocol. - - If more than one NAPTR record matches, they are processed in - increasing sort order. - -2.2.3 Terminal and Non-Terminal NAPTR Records - - A NAPTR record with an empty FLAG field is "non-terminal". That is, - more NAPTR RR lookups are to be performed. Thus, to process a NAPTR - record with an empty FLAG field in S-NAPTR, the REPLACEMENT field is - used as the target of the next DNS lookup -- for NAPTR RRs. - - In S-NAPTR, the only terminal flags are "S" and "A". These are - called "terminal" NAPTR lookups because they denote the end of the - - - -Daigle & Newton Expires August 15, 2004 [Page 4] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - DDDS/NAPTR processing rules. In the case of an "S" flag, the - REPLACEMENT field is used as the target of a DNS query for SRV RRs, - and normal SRV processing is applied. In the case of an "A" flag, an - address record is sought for the REPLACEMENT field target (and the - default protocol port is assumed). - -2.2.4 S-NAPTR and Successive Resolution - - As shown in the example NAPTR RR set above, it is possible to have - multiple possible targets for a single application service+protocol - pair. These are to be pursued in order until a server is - successfully contacted or all possible matching NAPTR records have - been successively pursued to terminal lookups and servers contacted. - That is, a client must backtrack and attempt other resolution paths - in the case of failure. - - "Failure" is declared, and backtracking must be used when - - o the designated remote server (host and port) fail to provide - appropriate security credentials for the *originating* domain - - o connection to the designated remote server otherwise fails -- the - specifics terms of which are defined when an application protocol - is registered - - o the S-NAPTR-designated DNS lookup fails to yield expected results - -- e.g., no A RR for an "A" target, no SRV record for an "S" - target, or no NAPTR record with appropriate application service - and protocol for a NAPTR lookup. Except in the case of the very - first NAPTR lookup, this last is a configuration error: the fact - that example.com has a NAPTR record pointing to "bunyip.example" - for the "WP:Whois++" service and protocol means the administrator - of example.com believes that service exists. If bunyip.example - has no "WP:Whois++" NAPTR record, the application client MUST - backtrack and try the next available "WP:Whois++" option from - example.com. As there is none, the whole resolution fails. - - An application client first queries for the NAPTR RRs for the domain - of a named application service. The application client MUST select - one protocol to choose The PREF field of the NAPTR RRs may be used by - the domain administrator to The first DNS query is for the NAPTR RRs - in the original target domain (example.com, above). - -2.2.5 Clients Supporting Multiple Protocols - - In the case of an application client that supports more than one - protocol for a given application service, it MUST pursue S-NAPTR - resolution completely for one protocol before trying another.j It MAY - - - -Daigle & Newton Expires August 15, 2004 [Page 5] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - choose which protocol to try first based on its own preference, or - from the PREF ranking in the first set of NAPTR records (i.e., those - for the target named domain). However, the chosen protocol MUST be - listed in that first NAPTR RR set. - - That is, what the client MUST NOT do is start looking for one - protocol, observe that a successive NAPTR RR set supports another of - its preferred protocols, and continue the S-NAPTR resolution based on - that protocol. For example, even if someisp.example offers the "IM" - service with protocol "ProtB", there is no reason to believe it does - so on behalf of example.com (since there is no such pointer in - example.com's NAPTR RR set). - -3. Guidelines - -3.1 Guidelines for Application Protocol Developers - - The purpose of S-NAPTR is to provide application standards developers - with a more powerful framework (than SRV RRs alone) for naming - service targets, without requiring each application protocol (or - service) standard to define a separate DDDS application. - - Note that this approach is intended specifically for use when it - makes sense to associate services with particular domain names (e.g., - e-mail addresses, SIP addresses, etc). A non-goal is having all - manner of label mapped into domain names in order to use this. - - Specifically not addressed in this document is how to select the - domain for which the service+protocol is being sought. It is up to - other conventions to define how that might be used (e.g., instant - messaging standards can define what domain to use from IM URIs, how - to step down from foobar.example.com to example.com, and so on, if - that is applicable). - - Although this document proposes a DDDS application that does not use - all the features of NAPTR resource records, it does not mean to imply - that DNS resolvers should fail to implement all aspects of the NAPTR - RR standard. A DDDS application is a client use convention. - - The rest of this section outlines the specific elements that protocol - developers must determine and document in order to make use of S- - NAPTR. - -3.1.1 Registration of application service and protocol tags - - Application protocol developers that wish to make use of S-NAPTR must - make provision to register any relevant application service and - application protocol tags, as described in Section 6. - - - -Daigle & Newton Expires August 15, 2004 [Page 6] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -3.1.2 Definition of conditions for retry/failure - - One other important aspect that must be defined is the expected - behaviour for interacting with the servers that are reached via S- - NAPTR. Specifically, under what circumstances should the client - retry a target that was found via S-NAPTR? What should it consider a - failure that causes it to return to the S-NAPTR process to determine - the next serviceable target (a less preferred target)? - - For example, if the client gets a "connection refused" from a server, - should it retry for some (protocol-dependent) period of time? Or, - should it try the next-preferred target in the S-NAPTR chain of - resolution? Should it only try the next-preferred target if it - receives a protocol-specific permanent error message? - - The most important thing is to select one expected behaviour and - document it as part of the use of S-NAPTR. - - As noted earlier, failure to provide appropriate credentials to - identify the server as being authoritative for the original taret - domain is always considered a failure condition. - -3.1.3 Server identification and handshake - - As noted in Section 7, use of the DNS for server location increases - the importance of using protocol-specific handshakes to determine and - confirm the identity of the server that is eventually reached. - - Therefore, application protocol developers using S-NAPTR should - identify the mechanics of the expected identification handshake when - the client connects to a server found through S-NAPTR. - -3.2 Guidelines for Domain Administrators - - Although S-NAPTR aims to provide a "straightforward" application of - DDDS and use of NAPTR records, it is still possible to create very - complex chains and dependencies with the NAPTR and SRV records. - - Therefore, domain administrators are called upon to use S-NAPTR with - as much restraint as possible, while still achieving their service - design goals. - - The complete set of NAPTR, SRV and A RRs that are "reachable" through - the S-NAPTR process for a particular application service can be - thought of as a "tree". Each NAPTR RR retrieved points to more NAPTR - or SRV records; each SRV record points to several A record lookups. - Even though a particular client can "prune" the tree to use only - those records referring to application protocols supported by the - - - -Daigle & Newton Expires August 15, 2004 [Page 7] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - client, the tree could be quite deep, and retracing the tree to retry - other targets can become expensive if the tree has many branches. - - Therefore, - - o Fewer branches is better: for both NAPTR and SRV records, provide - different targets with varying preferences where appropriate - (e.g., to provide backup services, etc), but don't look for - reasons to provide more. - - o Shallower is better: avoid using NAPTR records to "rename" - services within a zone. Use NAPTR records to identify services - hosted elsewhere (i.e., where you cannot reasonably provide the - SRV records in your own zone). - - -3.3 Guidelines for Client Software Writers - - To properly understand DDDS/NAPTR, an implementor must read [6]. - However, the most important aspect to keep in mind is that, if one - target fails to work for the application, it is expected that the - application will continue through the S-NAPTR tree to try the (less - preferred) alternatives. - -4. Illustrations - -4.1 Use Cases - - The basic intended use cases for which S-NAPTR has been developed - are: - - o Service discovery within a domain. For example, this can be used - to find the "authoritative" server for some type of service within - a domain (see the specific example in Section 4.2). - - o Multiple protocols. This is increasingly common as new - application services are defined. This includes the case of - instant messaging (a service) which can be offered with multiple - protocols (see Section 4.3). - - o Remote hosting. Each of the above use cases applies within the - administration of a single domain. However, one domain operator - may elect to engage another organization to provide an application - service. See Section 4.4 for an example that cannot be served by - SRV records alone. - - - - - - -Daigle & Newton Expires August 15, 2004 [Page 8] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -4.2 Service Discovery within a Domain - - There are occasions when it is useful to be able to determine the - "authoritative" server for a given application service within a - domain. This is "discovery", because there is no a priori knowledge - as to whether or where the service is offered; it is therefore - important to determine the location and characteristics of the - offered service. - - For example, there is growing discussion of having a generic - mechanism for locating the keys or certificates associated with - particular application (servers) operated in (or for) a particular - domain. Here's a hypothetical case for storing application key or - certificate data for a given domain. The premise is that some - credentials registry (CredReg) service has been defined to be a leaf - node service holding the keys/certs for the servers operated by (or - for) the domain. Furthermore, it is assumed that more than one - protocol is available to provide the service for a particular domain. - This DDDS-based approach is used to find the CredReg server that - holds the information. - - Thus, the set of NAPTR records for thinkingcat.example might look - like this: - - thinkingcat.example. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "" "CREDREG:ldap:iris-beep" "" theserver.thinkingcat.example. - - Note that another domain, offering the same application service, - might offer it using a different set of application protocols: - - anotherdomain.example. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "" "CREDREG:iris-lw:iris-beep" "" foo.anotherdomain.example. - - -4.3 Multiple Protocols - - As it stands, there are several different protocols proposed for - offering "instant message" services. Assuming that "IM" was - registered as an application service, this DDDS application could be - used to determine the available services for delivering to a target. - - Two particular features of instant messaging should be noted: - - 1. gatewaying is expected to bridge communications across protocols - - 2. instant messaging servers are likely to be operated out of a - - - -Daigle & Newton Expires August 15, 2004 [Page 9] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - different domain than the instant messaging address, and servers - of different protocols may be offered by independent - organizations - - For example, "thinkingcat.example" may support its own servers for - the "ProtA" instant messaging protocol, but rely on outsourcing from - "example.com" for "ProtC" and "ProtB" servers. - - Using this DDDS-based approach, thinkingcat.example can indicate a - preference ranking for the different types of servers for the instant - messaging service, and yet the out-sourcer can independently rank the - preference and ordering of servers. This independence is not - achievable through the use of SRV records alone. - - Thus, to find the IM services for thinkingcat.example, the NAPTR - records for thinkingcat.example are retrieved: - - thinkingcat.example. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "s" "IM:ProtA" "" _ProtA._tcp.thinkingcat.example. - IN NAPTR 100 20 "s" "IM:ProtB" "" _ProtB._tcp.example.com. - IN NAPTR 100 30 "s" "IM:ProtC" "" _ProtC._tcp.example.com. - - and then the administrators at example.com can manage the preference - rankings of the servers they use to support the ProtB service: - - _ProtB._tcp.example.com. - ;; Pref Weight Port Target - IN SRV 10 0 10001 bigiron.example.com - IN SRV 20 0 10001 backup.im.example.com - IN SRV 30 0 10001 nuclearfallout.australia-isp.example - - -4.4 Remote Hosting - - In the Instant Message hosting example in Section 4.3, the service - owner (thinkingcat.example) had to host pointers to the hosting - service's SRV records in the thinkingcat.example domain. - - A better way to approach this is to have one NAPTR RR in the - thinkingcat.example domain pointing to all the hosted services, and - the hosting domain has NAPTR records for each service to map them to - whatever local hosts it chooses (and may change from time to time). - - - - - - - - -Daigle & Newton Expires August 15, 2004 [Page 10] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - thinkingcat.example. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "s" "IM:ProtA" "" _ProtA._tcp.thinkingcat.example. - IN NAPTR 100 20 "" "IM:ProtB:ProtC" "" thinkingcat.example.com. - - - and then the administrators at example.com can break out the - individual application protocols and manage the preference rankings - of the servers they use to support the ProtB service (as before): - - thinkingcat.example.com. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "s" "IM:ProtC" "" _ProtC._tcp.example.com. - IN NAPTR 100 20 "s" "IM:ProtB" "" _ProtB._tcp.example.com. - - - - _ProtC._tcp.example.com. - ;; Pref Weight Port Target - IN SRV 10 0 10001 bigiron.example.com - IN SRV 20 0 10001 backup.im.example.com - IN SRV 30 0 10001 nuclearfallout.australia-isp.example - - -4.5 Sets of NAPTR RRs - - Note that the above sections assumed that there was one service - available (via S-NAPTR) per domain. Often, that will not be the - case. Assuming thinkingcat.example had the CredReg service set up as - described in Section 4.2 and the instant messaging service set up as - described in Section 4.4, then a client querying for the NAPTR RR set - from thinkingcat.com would get the following answer: - - thinkingcat.example. - ;; order pref flags service regexp replacement - IN NAPTR 100 10 "s" "IM:ProtA" "" _ProtA._tcp.thinkingcat.example. - IN NAPTR 100 20 "" "IM:ProtB:ProtC:" "" thinkingcat.example.com. - IN NAPTR 200 10 "" "CREDREG:ldap:iris-beep" "" bouncer.thinkingcat.example. - - Sorting them by increasing "ORDER", the client would look through the - SERVICE strings to determine if there was a NAPTR RR that matched the - application service it was looking for, with an application protocol - it could use. The first (lowest PREF) record that so matched is the - one the client would use to continue. - -4.6 Sample sequence diagram - - Consider the example in Section 4.3. Visually, the sequence of steps - - - -Daigle & Newton Expires August 15, 2004 [Page 11] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - required for the client to reach the final server for a "ProtB" - service for IM for the thinkingcat.example domain is as follows: - - - Client NS for NS for - thinkingcat.example example.com backup.im.example.com - | | | - 1 -------->| | | - 2 <--------| | | - 3 ------------------------------>| | - 4 <------------------------------| | - 5 ------------------------------>| | - 6 <------------------------------| | - 7 ------------------------------>| | - 8 <------------------------------| | - 9 ------------------------------------------------->| - 10 <-------------------------------------------------| - 11 ------------------------------------------------->| - 12 <-------------------------------------------------| - (...) - - - - 1. the name server (NS) for thinkingcat.example is reached with a - request for all NAPTR records - - 2. the server responds with the NAPTR records shown in Section 4.3. - - 3. the second NAPTR record matches the desired criteria; that has an - "s" flag and a replacement fields of "_ProtB._tcp.example.com". - So, the client looks up SRV records for that target, ultimately - making the request of the NS for example.com. - - 4. the response includes the SRV records listed in Section 4.3. - - 5. the client attempts to reach the server with the lowest PREF in - the SRV list -- looking up the A record for the SRV record's - target (bigiron.example.com). - - 6. the example.com NS responds with an error message -- no such - machine! - - 7. the client attempts to reach the second server in the SRV list, - and looks up the A record for backup.im.example.com - - 8. the client gets the A record with the IP address for - backup.im.example.com from example.com's NS. - - - - -Daigle & Newton Expires August 15, 2004 [Page 12] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - 9. the client connects to that IP address, on port 10001 (from the - SRV record), using ProtB over tcp. - - 10. the server responds with an "OK" message. - - 11. the client uses ProtB to challenge that this server has - credentials to operate the service for the original domain - (thinkingcat.example) - - 12. the server responds, and the rest is IM. - - -5. Motivation and Discussion - - Increasingly, application protocol standards are using domain names - to identify server targets, and stipulating that clients should look - up SRV resource records to determine the host and port providing the - server. This enables a distinction between naming an application - service target and actually hosting the server. It also increases - flexibility in hosting the target service: - - o the server may be operated by a completely different organization - without having to list the details of that organization's DNS - setup (SRVs) - - o multiple instances can be set up (e.g., for load balancing or - secondaries) - - o it can be moved from time to time without disrupting clients' - access, etc. - - This is quite useful, but Section 5.1 outlines some of the - limitations inherent in the approach. - - That is, while SRV records can be used to map from a specific service - name and protocol for a specific domain to a specific server, SRV - records are limited to one layer of indirection, and are focused on - server administration rather than on application naming. And, while - the DDDS specification and use of NAPTR allows multiple levels of - redirection before locating the target server machine with an SRV - record, this proposal requires only a subset of NAPTR strictly bound - to domain names, without making use of the REGEXP field of NAPTR. - These restrictions make the client's resolution process much more - predictable and efficient than with some potential uses of NAPTR - records. This is dubbed "S-NAPTR" -- a "S"traightforward use of - NAPTR records. - - - - - -Daigle & Newton Expires August 15, 2004 [Page 13] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -5.1 So, why not just SRV records? - - An expected question at this point is: this is so similar in - structure to SRV records, why are we doing this with DDDS/NAPTR? - - Limitations of SRV include: - - o SRV provides a single layer of indirection -- the outcome of an - SRV lookup is a new domain name for which the A RR is to be found. - - o the purpose of SRV is focused on individual server administration, - not application naming: as stated in [5] "The SRV RR allows - administrators to use several servers for a single domain, to move - services from host to host with little fuss, and to designate some - hosts as primary servers for a service and others as backups." - - o target servers by "service" (e.g., "ldap") and "protocol" (e.g., - "tcp") in a given domain. The definition of these terms implies - specific things (e.g., that protocol should be one of UDP or TCP) - without being precise. Restriction to UDP and TCP is insufficient - for the uses described here. - - The basic answer is that SRV records provide mappings from protocol - names to host and port. The use cases described herein require an - additional layer -- from some service label to servers that may in - fact be hosted within different administrative domains. We could - tweak SRV to say that the next lookup could be something other than - an address record, but that is more complex than is necessary for - most applications of SRV. - -5.2 So, why not just NAPTR records? - - That's a trick question. NAPTR records cannot appear in the wild -- - see [6]. They must be part of a DDDS application. - - The purpose here is to define a single, common mechanism (the DDDS - application) to use NAPTR when all that is desired is simple DNS- - based location of services. This should be easy for applications to - use -- some simple IANA registrations and it's done. - - Also, NAPTR has very powerful tools for expressing "rewrite" rules. - That power (==complexity) makes some protocol designers and service - administrators nervous. The concern is that it can translate into - unintelligible, noodle-like rule sets that are difficult to test and - administer. - - This proposed DDDS application specifically uses a subset of NAPTR's - abilities. Only "replacement" expressions are allowed, not "regular - - - -Daigle & Newton Expires August 15, 2004 [Page 14] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - expressions". - -6. IANA Considerations - - This document calls for 2 IANA registries: one for application - service tags, and one for application protocol tags. - - Application service and protocol tags should be defined in an RFC - (unless the "x-" experimental form is used, in which case they are - unregistered). There are no restrictions placed on the tags other - than that they must conform with the syntax defined below (Appendix - A.5). The IANA registries should list the tags and the RFC that - defines their use. - -7. Security Considerations - - The security of this approach to application service location is only - as good as the security of the DNS servers along the way. If any of - them is compromised, bogus NAPTR and SRV records could be inserted to - redirect clients to unintended destinations. This problem is hardly - unique to S-NAPTR (or NAPTR in general). - - To protect against DNS-vectored attacks, applications should define - some form of end-to-end authentication to ensure that the correct - destination has been reached. Many application protocols such as - HTTPS, BEEP, IMAP, etc... define the necessary handshake mechansims - to accomplish this task. - - The basic mechanism works in the following way: - - 1. During some portion of the protocol handshake, the client sends - to the server the original name of the desired destination (i.e. - no transformations that may have resulted from NAPTR - replacements, SRV targets, or CNAME changes). In certain cases - where the application protocol does not have such a feature but - TLS may be used, it is possible to use the "server_name" TLS - extension. - - 2. The server sends back to the client a credential with the - appropriate name. For X.509 certificates, the name would either - be in the subjectDN or subjectAltName fields. For Kerberos, the - name would be a service principle name. - - 3. Using the matching semantics defined by the application protocol, - the client compares the name in the credential with the name sent - to the server. - - 4. If the names match, there is reasonable assurance that the - - - -Daigle & Newton Expires August 15, 2004 [Page 15] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - correct end point has been reached. - - It is important to note that this document does not define either the - handshake mechanism, the specific credenential naming fields, nor the - name matching semantics. Definitions of S-NAPTR for particular - application protocols MUST define these. - -8. Acknowledgements - - Many thanks to Dave Blacka, Patrik Faltstrom, Sally Floyd for - discussion and input that has (hopefully!) provoked clarifying - revisions of this document. - -References - - [1] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource - Identifiers (URI): Generic Syntax", RFC 2396, August 1998. - - [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement - Levels", BCP 14, RFC 2119, March 1997. - - [3] Crocker, D. and P. Overell, "Augmented BNF for Syntax - Specifications: ABNF", RFC 2234, November 1997. - - [4] Eastlake, D., "Domain Name System Security Extensions", RFC - 2535, March 1999. - - [5] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for - specifying the location of services (DNS SRV)", RFC 2782, - February 2000. - - [6] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part - One: The Comprehensive DDDS", RFC 3401, October 2002. - - [7] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part - Three: The Domain Name System (DNS) Database", RFC 3403, October - 2002. - - [8] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part - Four: The Uniform Resource Identifiers (URI)", RFC 3404, October - 2002. - - - - - - - - - - -Daigle & Newton Expires August 15, 2004 [Page 16] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -Authors' Addresses - - Leslie Daigle - VeriSign, Inc. - 21355 Ridgetop Circle - Dulles, VA 20166 - US - - EMail: leslie@verisignlabs.com; leslie@thinkingcat.com - - - Andrew Newton - VeriSign, Inc. - 21355 Ridgetop Circle - Dulles, VA 20166 - US - - EMail: anewton@verisignlabs.com - -Appendix A. Application Service Location Application of DDDS - - This section defines the DDDS application, as described in [6]. - -A.1 Application Unique String - - The Application Unique String is domain label for which an - authoritative server for a particular service is sought. - -A.2 First Well Known Rule - - The "First Well Known Rule" is identity -- that is, the output of the - rule is the Application Unique String, the domain label for which the - authoritative server for a particular service is sought. - -A.3 Expected Output - - The expected output of this Application is the information necessary - to connect to authoritative server(s) (host, port, protocol) for an - application service within a given a given domain. - -A.4 Flags - - This DDDS Application uses only 2 of the Flags defined for the - URI/URN Resolution Application ([8]): "S" and "A". No other Flags - are valid. - - Both are for terminal lookups. This means that the Rule is the last - one and that the flag determines what the next stage should be. The - - - -Daigle & Newton Expires August 15, 2004 [Page 17] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - "S" flag means that the output of this Rule is a domain label for - which one or more SRV [5] records exist. "A" means that the output - of the Rule is a domain name and should be used to lookup address - records for that domain. - - Consistent with the DDDS algorithm, if the Flag string is empty the - next lookup is for another NAPTR record (for the replacement target). - -A.5 Service Parameters - - Service Parameters for this Application take the form of a string of - characters that follow this ABNF ([3]): - - service-parms = [ [app-service] *(":" app-protocol)] - app-service = experimental-service / iana-registered-service - app-protocol = experimental-protocol / iana-registered-protocol - experimental-service = "x-" 1*30ALPHANUMSYM - experimental-protocol = "x-" 1*30ALPHANUMSYM - iana-registered-service = ALPHA *31ALPHANUMSYM - iana-registered-protocol = ALPHA *31ALPHANUM - ALPHA = %x41-5A / %x61-7A ; A-Z / a-z - DIGIT = %x30-39 ; 0-9 - SYM = %x2B / %x2D / %x2E ; "+" / "-" / "." - ALPHANUMSYM = ALPHA / DIGIT / SYM - ; The app-service and app-protocol tags are limited to 32 - ; characters and must start with an alphabetic character. - ; The service-parms are considered case-insensitive. - - Thus, the Service Parameters may consist of an empty string, just an - app-service, or an app-service with one or more app-protocol - specifications separated by the ":" symbol. - - Note that this is similar to, but not the same as the syntax used in - the URI DDDS application ([8]). The DDDS DNS database requires each - DDDS application to define the syntax of allowable service strings. - The syntax here is expanded to allow the characters that are valid in - any URI scheme name (see [1]). Since "+" (the separator used in the - RFC3404 service parameter string) is an allowed character for URI - scheme names, ":" is chosen as the separator here. - -A.5.1 Application Services - - The "app-service" must be a registered service [this will be an IANA - registry; this is not the IANA port registry, because we want to - define services for which there is no single protocol, and we don't - want to use up port space for nothing]. - - - - - -Daigle & Newton Expires August 15, 2004 [Page 18] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -A.5.2 Application Protocols - - The protocol identifiers that are valid for the "app-protocol" - production are any standard, registered protocols [IANA registry - again -- is this the list of well known/registered ports?]. - -A.6 Valid Rules - - Only substitution Rules are permitted for this application. That is, - no regular expressions are allowed. - -A.7 Valid Databases - - At present only one DDDS Database is specified for this Application. - [7] specifies a DDDS Database that uses the NAPTR DNS resource record - to contain the rewrite rules. The Keys for this database are encoded - as domain-names. - - The First Well Known Rule produces a domain name, and this is the Key - that is used for the first lookup -- the NAPTR records for that - domain are requested. - - DNS servers MAY interpret Flag values and use that information to - include appropriate NAPTR, SRV or A records in the Additional - Information portion of the DNS packet. Clients are encouraged to - check for additional information but are not required to do so. See - the Additional Information Processing section of [7] for more - information on NAPTR records and the Additional Information section - of a DNS response packet. - -Appendix B. Pseudo pseudocode for S-NAPTR - -B.1 Finding the first (best) target - - Assuming the client supports 1 protocol for a particular application - service, the following pseudocode outlines the expected process to - find the first (best) target for the client, using S-NAPTR. - - - target = [initial domain] - naptr-done = false - - while (not naptr-done) - { - NAPTR-RRset = [DNSlookup of NAPTR RRs for target] - [sort NAPTR-RRset by ORDER, and PREF within each ORDER] - rr-done = false - cur-rr = [first NAPTR RR] - - - -Daigle & Newton Expires August 15, 2004 [Page 19] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - while (not rr-done) - if ([SERVICE field of cur-rr contains desired application - service and application protocol]) - rr-done = true - target= [REPLACEMENT target of NAPTR RR] - else - cur-rr = [next rr in list] - - if (not empty [FLAG in cur-rr]) - naptr-done = true - } - - port = -1 - - if ([FLAG in cur-rr is "S"]) - { - SRV-RRset = [DNSlookup of SRV RRs for target] - [sort SRV-RRset based on PREF] - target = [target of first RR of SRV-RRset] - port = [port in first RR of SRV-RRset] - } - - ; now, whether it was an "S" or an "A" in the NAPTR, we - ; have the target for an A record lookup - - host = [DNSlookup of target] - - return (host, port) - - - -B.2 Finding subsequent targets - - The pseudocode in Appendix B is crafted to find the first, most - preferred, host-port pair for a particular application service an - protocol. If, for any reason, that host-port pair did not work - (connection refused, application-level error), the client is expected - to try the next host-port in the S-NAPTR tree. - - The pseudocode above does not permit retries -- once complete, it - sheds all context of where in the S-NAPTR tree it finished. - Therefore, client software writers could - - o entwine the application-specific protocol with the DNS lookup and - RRset processing described in the pseudocode and continue the S- - NAPTR processing if the application code fails to connect to a - located host-port pair; - - - - -Daigle & Newton Expires August 15, 2004 [Page 20] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - - o use callbacks for the S-NAPTR processing; - - o use an S-NAPTR resolution routine that finds *all* valid servers - for the required application service and protocol from the - originating domain, and provides them in sorted order for the - application to try in order. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Daigle & Newton Expires August 15, 2004 [Page 21] - -Internet-Draft draft-daigle-napstr-04 February 2004 - - -Full Copyright Statement - - Copyright (C) The Internet Society (2004). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assigns. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - -Daigle & Newton Expires August 15, 2004 [Page 22] - diff --git a/doc/draft/draft-danisch-dns-rr-smtp-03.txt b/doc/draft/draft-danisch-dns-rr-smtp-03.txt deleted file mode 100644 index 4a01d91b9a..0000000000 --- a/doc/draft/draft-danisch-dns-rr-smtp-03.txt +++ /dev/null @@ -1,1960 +0,0 @@ - - - -INTERNET-DRAFT Hadmut Danisch -Category: Experimental Oct 2003 -Expires: Apr 1, 2004 - - The RMX DNS RR and method for lightweight SMTP sender authorization - draft-danisch-dns-rr-smtp-03.txt - -Status of this Memo - - This document is an Internet-Draft and is subject to all provisions - of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six - months and may be updated, replaced, or obsoleted by other - documents at any time. It is inappropriate to use Internet-Drafts - as reference material or to cite them other than as "work in - progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/1id-abstracts.html - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html - -Abstract - - This memo introduces a new authorization scheme for SMTP e-mail - transport. It is designed to be a simple and robust protection - against e-mail fraud, spam and worms. It is based solely on - organisational security mechanisms and does not require but still - allow use of cryptography. This memo also focuses on security and - privacy problems and requirements in context of spam defense. In - contrast to prior versions of the draft a new RR type is not - required anymore. - - - - - - - - - - - - -Hadmut Danisch Experimental [Page 1] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - Table of Contents - - -1. General Issues . . . . . . . . . . . . . . . . . . . . . . . . . 4 -2. Problem and threat description . . . . . . . . . . . . . . . . . 4 - 2.1. Mail sender forgery . . . . . . . . . . . . . . . . . . . 4 - 2.1.1 Definition of sender forgery . . . . . . . . . . . 4 - 2.1.2 Spam . . . . . . . . . . . . . . . . . . . . . . . 5 - 2.1.3 E-Mail Worms . . . . . . . . . . . . . . . . . . . 5 - 2.1.4 E-Mail spoofing and fraud . . . . . . . . . . . . . 5 - 2.2. Indirect damage caused by forgery . . . . . . . . . . . . 6 - 2.3. Technical problem analysis . . . . . . . . . . . . . . . . 6 - 2.4. Shortcomings of cryptographical approaches . . . . . . . . 7 -3. A DNS based sender address verification . . . . . . . . . . . . 7 - 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 3.2. Envelope vs. header sender address . . . . . . . . . . . . 9 - 3.3. Domain part vs. full sender address . . . . . . . . . . . 9 -4. Mapping of E-Mail addresses to DNS names . . . . . . . . . . . . 10 - 4.1. Domain part only . . . . . . . . . . . . . . . . . . . . . 10 - 4.2. Full address . . . . . . . . . . . . . . . . . . . . . . . 11 - 4.3. Empty address . . . . . . . . . . . . . . . . . . . . . . 11 -5. Mandatory entry types and their syntax . . . . . . . . . . . . . 11 - 5.1. Overall structure . . . . . . . . . . . . . . . . . . . . 11 - 5.2. Unused . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 5.3. IPv4 and IPv6 address ranges . . . . . . . . . . . . . . . 12 - 5.4. DNS Hostname . . . . . . . . . . . . . . . . . . . . . . . 13 - 5.4.1 Road warriors and DynDNS entries . . . . . . . . . 13 - 5.5. APL Reference . . . . . . . . . . . . . . . . . . . . . . 14 - 5.6. Domain Member . . . . . . . . . . . . . . . . . . . . . . 14 - 5.7. Full Address Query . . . . . . . . . . . . . . . . . . . . 15 - 5.8. DNS mapped authorization . . . . . . . . . . . . . . . . . 15 - 5.9. RMX reference . . . . . . . . . . . . . . . . . . . . . . 16 -6. Optional and experimental entry types . . . . . . . . . . . . . 16 - 6.1. TLS fingerprint . . . . . . . . . . . . . . . . . . . . . 16 - 6.2. TLS and LDAP . . . . . . . . . . . . . . . . . . . . . . . 16 - 6.3. PGP or S/MIME signature . . . . . . . . . . . . . . . . . 16 - 6.4. Transparent Challenge/Response . . . . . . . . . . . . . . 17 - 6.5. SASL Challenge/Response . . . . . . . . . . . . . . . . . 17 -7. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.1. Alternative encoding as TXT records . . . . . . . . . . . 17 - 7.2. RMX Records . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.2.1 Overall structure . . . . . . . . . . . . . . . . . 18 - 7.2.2 Record encoding . . . . . . . . . . . . . . . . . . 18 - 7.2.3 Encoding of IPv4 and IPv6 address ranges . . . . . 18 - 7.2.4 Encoding of DNS . . . . . . . . . . . . . . . . . . 18 - 7.2.5 Encoding of unused and full query . . . . . . . . . 19 - 7.2.6 Additional Records . . . . . . . . . . . . . . . . 19 -8. Message Headers . . . . . . . . . . . . . . . . . . . . . . . . 19 - - - -Hadmut Danisch Experimental [Page 2] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - -9. SMTP error messages . . . . . . . . . . . . . . . . . . . . . . 20 -10. Message relaying and forwarding . . . . . . . . . . . . . . . . 20 - 10.1. Problem description . . . . . . . . . . . . . . . . . . . 20 - 10.2. Trusted relaying/forwarding . . . . . . . . . . . . . . . 21 - 10.3. Untrusted relaying/forwarding . . . . . . . . . . . . . . 21 -11. Security Considerations . . . . . . . . . . . . . . . . . . . . 22 - 11.1. Draft specific considerations . . . . . . . . . . . . . . 22 - 11.1.1 Authentication strength . . . . . . . . . . . . . 22 - 11.1.2 Where Authentication and Authorization end . . . . 22 - 11.1.3 Vulnerability of DNS . . . . . . . . . . . . . . . 23 - 11.1.4 Sneaking RMX attack? . . . . . . . . . . . . . . 25 - 11.1.5 Open SMTP relays . . . . . . . . . . . . . . . . . 25 - 11.1.6 Unforged Spam . . . . . . . . . . . . . . . . . . 25 - 11.1.7 Reliability of Whois Entries . . . . . . . . . . . 26 - 11.1.8 Hazards for Freedom of Speech . . . . . . . . . . 26 - 11.2. General Considerations about spam defense . . . . . . . . 27 - 11.2.1 Action vs. reaction . . . . . . . . . . . . . . . 27 - 11.2.2 Content based Denial of Service attacks . . . . . 27 -12. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 28 - 12.1. Draft specific considerations . . . . . . . . . . . . . . 28 - 12.1.1 No content leaking . . . . . . . . . . . . . . . . 28 - 12.1.2 Message reception and sender domain . . . . . . . 28 - 12.1.3 Network structure . . . . . . . . . . . . . . . . 29 - 12.1.4 Owner information distribution . . . . . . . . . . 29 - 12.2. General Considerations about spam defense . . . . . . . . 29 - 12.2.1 Content leaking of content filters . . . . . . . . 29 - 12.2.2 Black- and Whitelists . . . . . . . . . . . . . . 30 -13. Deployment Considerations . . . . . . . . . . . . . . . . . . . 30 - 13.1. Compatibility . . . . . . . . . . . . . . . . . . . . . . 30 - 13.1.1 Compatibility with old mail receivers . . . . . . 30 - 13.1.2 Compatibility with old mail senders . . . . . . . 30 - 13.1.3 Compatibility with old DNS clients . . . . . . . . 30 - 13.1.4 Compatibility with old DNS servers . . . . . . . . 30 - 13.2. Enforcement policy . . . . . . . . . . . . . . . . . . . 31 -14. General considerations about fighting spam . . . . . . . . . . 31 - 14.1. The economical problem . . . . . . . . . . . . . . . . . 31 - 14.2. The POP problem . . . . . . . . . . . . . . . . . . . . . 32 - 14.3. The network structure problem . . . . . . . . . . . . . . 33 - 14.4. The mentality problem . . . . . . . . . . . . . . . . . . 33 - 14.5. The identity problem . . . . . . . . . . . . . . . . . . 33 - 14.6. The multi-legislation problem . . . . . . . . . . . . . . 34 -Implementation and further Information . . . . . . . . . . . . . . . 34 -References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 -Draft History . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 -Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . . 35 - - - - - - -Hadmut Danisch Experimental [Page 3] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - -1. General Issues - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in - this document are to be interpreted as described in RFC 2119 [1]. - -2. Problem and threat description - -2.1. Mail sender forgery - - The amount of e-mails with forged sender addresses has dramatically - increased. As a consequence, damages and annoyances caused by such - e-mails increased as well. In the majority of examined e-mails the - domain name of the envelope sender address was forged, and the e- - mail was sent from an IP address which does not belong to a network - used by the actual owner of the domain. - -2.1.1. Definition of sender forgery - - As discussions, comments to prior versions of this draft, and - different approaches to stop forgery showed, different perceptions - of "mail forgery" exist. For example, there are mechanisms to - verify e-mail addresses for mailing lists, web servers, or to stop - spam, which do send a message with a random number to the given - address and expect the user to send a reply. Here, someone is - considered to be allowed to use a particular e-mail address, if and - only if he is able to receive informations sent to this address, - and is able to reply to such a message. While this definition - appears to be quite plausible and natural, it can't be used for a - simple technical solution. Sending back a challenge and expecting a - reply is simply too much overhead and time delay, and not every - authorized sender is able or willing to reply (e.g. because he went - offline or is not a human). - - Within the scope of this memo, sender forgery means that the - initiator of an e-mail transfer (which is the original sender in - contrast to relays) uses a sender address which he was not - authorized to use. Being authorized to use an address means that - the owner (administrator) of the internet domain has given - permission, i.e. agrees with the use of the address by that - particular sender. This memo will cover both the permission of the - full e-mail address and the domain part only for simplicity. - - Within context of Internet and SMTP, the sender address usually - occurs twice, once as the envelope sender address in SMTP, and once - as the address given in the RFC822 mail header. While the following - considerations apply to both addresses in principle, it is - important to stress that both addresses have distinct semantics and - - - -Hadmut Danisch Experimental [Page 4] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - are not neccessarily the same. The envelope address identifies the - initiator of the transport, while the header identifies the author - of the message content. Since this memo deals with the message - transport only and completely ignores the message content, the - method should naturally be applied to the envelope sender address. - -2.1.2. Spam - - A common and well known problem is the dramatic increase of - unsolicited e-mail, commonly called "spam". Again, the majority of - examined e-mails had forged sender addresses. The abused domains - were mainly those of common webmailers as hotmail or yahoo, or - well-known companies. - - Unfortunately, there is no accurate definition of spam availabe - yet, and neither are the concise technical criterions to filter or - block spam with technical mechanisms. There are efforts to design - content based filters, but these filters are expensive in - calculation time (and sometimes money), and they do not reliably - provide predictable results. Usually they give false positives - and/or require user interaction. Content filters in general suffer - from a design problem described later in this memo. Therefore, - this proposal does not use the content based approach to block - spam. - - As analysis of spam messages showed, most of spam messages were - sent with forged envelope sender addresses. This has mainly three - reasons. The first reason is, that spam senders usually do not - want to be contacted by e-mail. The second reason is, that they do - not want to be blacklisted easily. The third reason is, that spam - is or is going to be unlawful in many countries, and the sender - does not want to reveal his identity. Therefore, spam is considered - to be a special case of sender forgery. - -2.1.3. E-Mail Worms - - Another example of sender forgery is the reproduction of e-mail - worms. Most worms do choose random sender addresses, e.g. using - the addresses found in mailboxes on the infected system. In most - cases analyzed by the author, the e-mails sent by the reproduction - process can also be categorized as forged, since the infected - system would under normal circumstances not be authorized to send - e-mails with such e-mail addresses. So forgery does not require a - malicious human to be directly involved. This memo covers any kind - of e-mail sender address forgery, included those generated by - malicious software. - -2.1.4. E-Mail spoofing and fraud - - - -Hadmut Danisch Experimental [Page 5] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - Forging e-mail sender addresses for fraud or other kinds of - deception ("human engineering") has also dramatically increased. - There are many known cases where single or mass e-mails were sent - with wrong sender addresses, pretending to come from service - provider, software manufacturers etc., and asking the receiver to - install any software or patches, or to reply with any confidential - information. The Internet is becoming more and more a scene of - crime, and so are it's services, including e-mail. It is obvious - that crime based on e-mail is eased by the fact that SMTP allows - arbitrary sender address spoofing. - -2.2. Indirect damage caused by forgery - - As observed by the author, mass mails and worms with forged sender - addresses can cause a severe damage for the real owner of the - abused sender addresses. If a sender A is sending an e-mail to the - receiver B, pretending to be C by using a sender address of C's - domain, then C has currently no chance to prevent this, since C's - machines and software are not involved in any way in the delivery - process between A and B. B will nevertheless send any error - messages (virus/spam alert, "no such user", etc.) to C, erroneously - assuming that the message was sent by C. The author found several - cases where this flood of error messages caused a severe denial of - service or a dramatic increase of costs, e.g. when C was - downloading the e-mail through expensive or low bandwidth - connections (e.g. modem or mobile phones), or where disk space was - limited. The author examined mass mailings, where several tens or - hundreds of thousands of messages were sent to several addresses - around the world, where these messages caused only annoyance. But - since several thousands of these addresses were invalid or didn't - accept the message, the owner of the DNS domain which was abused by - the spammer to forge sender addresses was flooded for several - months with thousands of error messages, jamming the e-mail system - and causing severe costs and damages. - - As a consequence, when A sends a message to B, pretending to be C, - there must be any mechanism to allow C to inform B about the fact, - that A is not authorized to use C as a sender address. This is what - this memo is about. - -2.3. Technical problem analysis - - Why does e-mail forgery actually exist? Because of the lack of the - Simple Mail Transfer Protocol SMTP[2] to provide any kind of sender - authentication, authorisation, or verification. This protocol was - designed at a time where security was not an issue. Efforts have - been made to block forged e-mails by requiring the sender address - domain part to be resolvable. This method provides protection from - - - -Hadmut Danisch Experimental [Page 6] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - e-mails with non-existing sender domains, and indeed, for some time - it blocked most spam e-mails. However, since attackers and spam - senders began to abuse existing domain names, this method was - rendered ineffective. - -2.4. Shortcomings of cryptographical approaches - - At a first glance, the problem of sender address forgery might - appear to be solvable with cryptographic methods such as challenge - response authentications or digital signatures. A deeper analysis - shows that only a small, closed user group could be covered with - cryptographical methods. Any method used to stop spam forgery must - be suitable to detect forgery not only for a small number of - particular addresses, but for all addresses on the world. An - attacker does not need to know the secrets belonging to a - particular address. It is sufficient to be able to forge any - address and thus to know any secret key. Since there are several - hundreds of millions of users, there will always be a large amount - of compromised keys, thus spoiling any common cryptographic method. - Furthermore, cryptography has proven to be far too complicated and - error prone to be commonly administered and reliably implemented. - Many e-mail and DNS administrators do not have the knowledge - required to deal with cryptographic mechanisms. Many legislations - do not allow the general deployment of cryptography and a directory - service with public keys. For these reasons, cryptography is - applicable only to a small and closed group of users, but not to - all participants of the e-mail service. - -3. A DNS based sender address verification - -3.1. Overview - - To gain improvement in e-mail authenticity while keeping as much - SMTP compatibility as possible, a method is suggested which doesn't - change SMTP at all. - - The idea is to store informations about how to verify who is - authorized to transmit e-mails through SMTP with a particular - sender address (either full address or - for simplicity - only the - domain part of the address) in a directory service, which is - currently the DNS. To be precise, the verification consists of two - steps, the classical pair of authentication and authorization: - - The first step is the authentication. While several methods are - possible to perform authentication (see below), the most important - and robust method is the verification of the sender's IP address. - This is done implicitely by TCP/IP and the TCP sequence number. The - authenticated identity is the IP address. It has to be stressed - - - -Hadmut Danisch Experimental [Page 7] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - that this TCP/IP "authentication" is a weak authentication and - vulnerable to several attacks. It is nevertheless sufficient for - this purpose, especially for blocking spam. It doesn't take any - implementation and it doesn't cost: It is already there, it is a - functionality of TCP/IP. An incoming SMTP connection based on - TCP/IP already carries the sender's IP address without any - modification of SMTP. See below (section Entry types) for more - details about authentication methods. - - The second step is the authorization. It is based on the identity - given by the previous authentication step, e.g. the IP address of - the originator of the incoming SMTP connection, and on the - envelope sender address. The mechanism proposed in this memo - answers the question "Is that particular sender (IP address,...) - allowed to send with that sender address" by querying and - processing informations stored in a directory service, which is - DNS. - - When the sender has issued the "MAIL FROM:" SMTP command, the - receiving mail transfer agent (MTA) can - and modern MTAs do - - perform some authorization checks, e.g. run a local rule database - or check whether the sender domain is resolvable. - - The suggested method is to let the DNS server for the sender domain - provide informations about who - this means for example which IP - address - is authorized to use an address or a domain as a part of - it. After receiving the "MAIL FROM:" SMTP command, the receiving - MTA can verify, whether e. g. the IP address of the sending MTA is - authorized to send mails with this domain name. Therefore, a list - of entries with authorized IP addresses or other informations is - provided by the authoritative DNS server of that domain. The entry - types are described in the subsequent chapters. Some of these - methods are - - - An IPv4 or IPv6 network address and mask - - A fully qualified domain name referring to an A record - - A fully qualified domain name referring to an APL record - - RMX records of these types would look like this: - - somedomain.de. IN RMX ipv4:10.0.0.0/8 - rmxtest.de. IN RMX host:relay.provider.com - danisch.de. IN RMX apl:relays.rackland.de - relays.rackland.de. IN APL 1:213.133.101.23/32 1:1.2.3.0/24 - - where the machine with the example address 213.133.101.23 and the - machines in the example subnet 1.2.3.0/24 are the only machines - allowed to send e-mails with an envelope sender address of domain - - - -Hadmut Danisch Experimental [Page 8] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - danisch.de. Since the APL records do not necessarily belong to the - same domain or zone table as the RMX records, this easily allows to - refer to APL records defined by someone else, e.g. the internet - access or server hosting provider, thus reducing administrative - overhead to a minimum. In the example given above, the domain - danisch.de and several other domains are hosted by the service - provider Rackland. So if the relay structure of Rackland is - modified, only the zone of rackland.de needs to be modified. The - domain owners don't need to care about such details. - -3.2. Envelope vs. header sender address - - Questions were raised why the proposed mechanism is based on the - envelope sender address, and not on the sender address given in the - message header. Technically, both can be used. Actually, it makes - sense to use the envelope address. - - In common, the header sender address identifies the author of the - content, while the envelope sender tells who caused the - transmission. The approach proposed in this memo is transmission - based, not content based. We can not authorize the author of a - message if we don't have contact with him, if the message does not - already contain a signature. In contrast, the sending MTA is linked - to an IP address which can be used for authentication. This - mechanism might not be very strong, but it is available and - sufficient to solve today's e-mail security problems. - - Some people argued that it is the header address and not the sender - address, which is displayed in common mail readers (MUAs), and - where the receiver believes the mail comes from. That's true, but - it doesn't help. There are many cases where the header sender - differs from the envelope sender for good reasons (see below in the - consequences chapter for the discussion about relaying). Relaying, - mailing lists etc. require to replace the sender address used for - RMX. If this were the header address, the message header would have - to be modified. This is undesirable. - -3.3. Domain part vs. full sender address - - Former versions of this draft were limited to the domain part of - the sender address. The first reason is that it is common and MX- - like, to lookup only the domain part of an e-mail address in DNS. - The second reason is, that it was left to the private business of - the domain administration to handle details of user verification. - The idea was that the domain administration takes care to verify - the left part of an e-mail address with an arbitrary method of - their individual taste. RMX was originally designed to ignore the - left part of the address and to expect the domain administration to - - - -Hadmut Danisch Experimental [Page 9] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - take over responsibility for enforcing their policy. If, e.g., a - spam message arrived and passed the RMX mechanism, it is known to - be authorized by the domain administration and they can be blamed, - no matter what is on the left side of the sender address - it's - their private problem what happens on the left side of the @. By - far the most of the comments to prior versions of this draft agreed - with that. A few comments asked for a finer granularity. - - And indeed, there is no technical reason against a finer - granularity. All it takes is a mapping from a given envelope - sender address to a DNS name, and the RMX lookup for that - particular e-mail address could be done instead of a lookup for the - domain part only. However, to my knowledge, most domain - administrators would not like to provide an RMX entry for every - single e-mail address. In many cases, this would also overload DNS - servers. - - It is to be discussed how to cover both views. One method could be - to query the full address, and if no RMX records were found to - query the domain part only. A different approach would be to query - the domain part only, and if it's RMX record contain a special - entry, then a new query for the full address is triggered. A third - way would be to always query the full address and to leave the - problem to the wildcard mechanism of DNS. This still has to be - discussed and will be described in future versions of this draft. - - - - - - - - - - - -4. Mapping of E-Mail addresses to DNS names - - To perform the RMX query, a mapping is needed from E-Mail addresses - to DNS fully qualified domain names. - - This chapter is under development and just a first approach. - -4.1. Domain part only - - Mapping of the domain part is trivial, since the domain part of an - e-mail address itself is a valid DNS name and does not need - translation. It might be nevertheless desirable to distinguish the - - - -Hadmut Danisch Experimental [Page 10] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - RMX entries from other entries, depending of the encoding of the - records. If the RMX entries are encoded in TXT record types, they - might collide with other uses of TXT records. It might be - necessary to prepend the domain part with a special prefix, e.g. - _rmx. So the e-mail address some.user@example.com could be mapped - to example.com or _rmx.example.com. - -4.2. Full address - - Mapping a full address is slightly more difficult. The @ sign must - be unambiguously translated, and therefore can not be simply - translated into a dot. The e-mail addresses some.user@example.com - and some@user.example.com must have different mappings. Therefore, - the @ sign could be translated into _rmx, implicitely assuming that - this is not an allowed domain name component of normal domain - names. Then the rightmost _rmx in the mapped DNS name always - corresponds to the @ sign. some.user@example.com would e translated - into some.user._rmx.example.com and can be covered by a wildcard - entry like *._rmx.example.com. - - Character encoding and character sets are still to be discussed. - -4.3. Empty address - - Unfortunately, SMTP allows empty envelope sender addresses to be - used for error messages. Empty sender addresses can therefore not - be prohibited. As observed, a significant amount of spam was sent - with such an empty sender address. To solve this problem, the host - name given in the HELO or EHLO command is taken to lookup the RMX - records instead. This makes sense, since such messages were - generated by the machine, not a human. - - - - -5. Mandatory entry types and their syntax - - The entry types described in this section MUST be supported by any - implementation of this draft. - -5.1. Overall structure - - Similar to APL, an RMX record is just a concatenation of zero or - more RMX entries. The entries within one record form an ordered - rule base as commonly usual in packet filtes and firewall rulesets, - i. e. they are processed one ofter another until the first entry - matches. This entry determines the result of the query. Once a - matching entry is found, the RMX processing is finished. - - - -Hadmut Danisch Experimental [Page 11] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - For any domain name there should not exist more than a single RMX - record. Due to the structure of DNS, it is nevertheless possible to - have more than a single RMX record. Multiple RMX records are - treated as a single record consisting of the concatenation of all - records. While the entries in a record are ordered, the records are - not ordered and may be processed in arbitrary order. If the order - of the entries matters, it is the zone maintainer's responsibility - to keep those entries in a single record. For example, there are - negative entries, which exclude IP addresses from authorization. - It is important that these entries are processed before positive - entries giving permission to a wider address range. Since order is - guaranteed only within a record, corresponding negative and - positive entries must be put in the same record. - - An RMX record may consist of one or more entries, where the entries - are separated by whitespace. An entry must not contain white space. - Each entry consists of an optional exclamation sign, a tag, a - colon, and the entry data: - - [!] TAG : ENTRY-SPECIFIC-DATA - - If the entry starts with an exclamation sign, the entry is negated. - See the entry type description below for details. - - The TAG is the mnemonic type identifier or the decimal number of - the entry. The TAG is case-insensitive. It is immediately followed - by a colon. - - The syntax and semantics of ENTRY-SPECIFIC-DATA depends of the the - entry type. See description below. - - Example: - - danisch.de. IN RMX apl:relays.rackland.de !ipv4:1.2.3.5 - ipv4:1.2.3.0/24 - -5.2. Unused - - This is a primitive entry which just says that this sender address - will never be used as a sender address under any circumstances. - Example: - - testdomain.danisch.de IN RMX unused: - -5.3. IPv4 and IPv6 address ranges - - These entry types contain a bit sequence representing a CIDR - address part. If that bit sequence matches the given IP address, - - - -Hadmut Danisch Experimental [Page 12] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - authorization is granted or denied, depending on the negation flag. - - The entry is prepended with the tag "IPv4" or "IPv6". The colon is - followed with an IPv4 or IPv6 address in standard notation, - optionally followed by a slash and a mask length. If the negation - flag is set, then the given address range is excluded. Examples: - - danisch.de IN RMX ipv4:213.133.101.23 ipv6:fe00::0 - IN RMX ipv4:10.0.0.0/8 ipv6:fec0::0/16 - IN RMX !ipv4:1.2.3.4 - - (Please note that it does not make much sense to use - RFC1918-Addresses in RMX records, this is just to give a syntax - example.) - - -5.4. DNS Hostname - - This entry type simply contains a regular DNS name, which is to be - resolved as a host name (fetch the A record or IPv6 equivalent). If - the given IP address matches the result, authorization is granted - or denied, depending on the negation flag. It is still to be - defined how to treat unresolvable entries. - - The entry is prepended with the tag "host", followed by a colon and - the hostname. Examples: - - danisch.de IN RMX host:relay.provider.de - IN RMX !host:badmachine.domain.de apl:relays.domain.de - -5.4.1. Road warriors and DynDNS entries - - Several people argued against RMX that it would break their - existing installation which delivers e-mail from dynamically - assigned IP addresses, because their IP providers didn't assign a - static address, or because they are a road warrior, plugging their - notebook in any hotel room on the world. - - RMX provides a simple solution. If such a machine has a dynamically - updated DNS entry (e.g. DynDNS), all it takes is an RMX entry of - the hostname type pointing to this dynamic DNS entry. - - The cleaner solution would be to deliver mail the same way as it is - received: If downloaded by POP from a central relay with a static - address, where the MX points to, then it would be a good idea to - deliver e-mail the same way in reverse direction. Unfortunately, - plain POP does not support uploading yet. - - - - -Hadmut Danisch Experimental [Page 13] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - -5.5. APL Reference - - This entry type simply contains a regular DNS name, which is to be - resolved as an APL record index (fetch the APL record). If the - given IP address positively matches the APL, authorization is - granted. Details of the semantic (espially when the negation bit is - set) are still to be defined. It is still to be defined how to - treat unresolvable entries. - - The entry is prepended with the tag "host", followed by a colon and - the hostname. Example: - - danisch.de IN RMX apl:relays.rackland.de - -5.6. Domain Member - - In many cases it is desirable to cover all hosts of a given domain - with an RMX record without the need to duplicate the list of these - hosts. This entry type does it (thanks to Eric A. Hall for pointing - out this entry type). It contains a regular DNS name. - - If this entry type is given, a reverse DNS query for the IP address - of the sending MTA is performed to find its official fully - qualified domain name. To prevent spoofing, this domain name is - accepted only if a subsequent address query to the given domain - name points to exactly the IP address of the sending MTA (the usual - procedure to verify PTR records). - - The entry matches if the fully qualified domain name of the sending - MTA ends in the given domain. The negation flag works as usual. - - The tag for this entry type is "domain". After the colon the domain - name is given, but might be empty, thus pointing to itself. - Example: - - somedomain.org IN RMX domain:somedomain.org domain:provider.com - - would authorize all machines which's hostname can be verified - through an PTR and A query, and which ends in "somedomain.org" or - "provider.com". - - With such an entry, large companies with different networks can - easily be covered with just a single and simple RMX entry. - Obviously, it requires proper PTR records. - - As a special shortcut, the DNS name may be empty. In this case the - domain name of the zone itself is taken. Thus, with a very simple - entry of the type - - - -Hadmut Danisch Experimental [Page 14] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - somecompany.com IN RMX domain: - - a company could authorize all machines which's IP addresses map to - DNS names end in somecompany.com, which applies in the majority of - companies. - - - - -5.7. Full Address Query - - As described above, RMX records will in most cases apply to the - domain part of the sender address. In special cases it might be - desirable to query the RMX record for a particular address. An RMX - entry of the Full Address Query type may occur in a domain RMX - record only. It signals that the RMX record for the full address is - to be fetched and processed. - - This entry type does not take arguments. The negation flag is not - supported. The tag is "full". - - If such a full address query is to be performed, the mail address - must be mapped to a valid and non-ambiguos DNS name. This mapping - is still to be defined. It is not sufficient to simply replace the - @ with a dot, because of case sensitivity, character sets, etc. The - e-mail addresses - - john.doe@example.org - John.Doe@example.org - john@doe.example.org - - must all be mapped to different DNS entries. This entry type might - vanish in future versions of the draft, depending on the discussion - about whether to query the domain name part only or the full - address. - -5.8. DNS mapped authorization - - As I learned from comments to prior versions of the draft and from - alternative proposals, many users wish to have a DNS mapped - authorization table, i. e. the client queries a DNS entry of the - form a.b.c.d.domain, where a.b.c.d is the sender's IP address. - Since people wish to have this, RMX will now include such a mapping - entry. The entry has a parameter giving the DNS domain name where - to look at. If the parameter is empty, then the same domain is - taken as for the RMX lookup. - - As this is currently under construction and discussion in an IETF - - - -Hadmut Danisch Experimental [Page 15] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - group, details will be published in future versions of this draft. - -5.9. RMX reference - - This entry type has no parameters. It means that all those machines - are authorized, which are pointed to by an MX record. - -6. Optional and experimental entry types - - The following subsections roughly describe further entry types - which might not be supported by all implementations and might not - be allowed in all legislations. These methods might vanish in - future versions of the draft and are just considerations about what - to include in RMX and what to not include. The main purpose of this - section is to start discussion about such entry types. - - The disadvantage of the following methods is that they violate the - basic idea of RMX, i. e. to be simple, robust, easy to implement - and easy to administer. I personally do not believe that it is a - good idea or even feasible to implement cryptography for a world - wide e-mail transfer network. Keep in mind that cryptographic keys - can be copied. If only <0.1% of cryptographic keys were revealed, - this completely compromises and spoils RMX. Cryptography is simply - the wrong tool for the problem RMX is intended to solve. I - nevertheless like to discuss these methods. - -6.1. TLS fingerprint - - The sender is considered to be authorized if the message was - transmitted through SMTP and TLS, and the sender used a certificate - matching the fingerprint given in the RMX record. - -6.2. TLS and LDAP - - This means that the receiver should perform an LDAP query for the - sender address (through the LDAP SRV record or given in the RMX - record), fetch the X.509 certificate for the sender. The sender is - considered to be authorized when the message was transmitted - through SMTP and TLS using this certificate. - -6.3. PGP or S/MIME signature - - It would be possible to accept a message only if it was signed with - PGP or S/MIME with a key which's fingerprint is given in the RMX - record or to be fetched from LDAP or any PGP database. This is - just for discussion, since it violates the idea of RMX to focus on - the transport, not on the content. It would also allow replay - attacks and not cover the envelope sender address or message - - - -Hadmut Danisch Experimental [Page 16] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - header. - -6.4. Transparent Challenge/Response - - It would also be possible to implement a challenge-response - mechanism without modifying the syntax of SMTP. For example, the - receiving MTA could issue a challenge with it's very first greeting - message, the sending MTA could hide the response in the HELO - parameter and when the receiving MTA later learns the sender - envelope address, it could verify the response based on - informations in the RMX record. - -6.5. SASL Challenge/Response - - Modern SMTP implementations already include a SASL mechanisms, - which easily allows to plugin new authentication mechanisms. While - common SASL mechanisms require to use a previously shared password, - a new mechanism could perform a challenge response authentication - as a SASL method. - - - - - - -7. Encoding - -7.1. Alternative encoding as TXT records - - The main objection against the prior versions of this draft was - that it requires a new RR entry type and upgrading all DNS servers. - - Therefore and alternative encoding is proposed. Instead of using a - new RR type, the TXT record type is used to contain the RMX record. - The records would simply look as described in the entry type - chapters above, e.g. - - _rmx.danisch.de. IN TXT "apl:relays.rackland.de" - - To allow smooth introduction of RMX without the need to immediately - upgrade all DNS servers, all clients (which have to be newly - installed anyway) MUST support both the TXT and the RMX records. A - client has to perform an ANY or a TXT and a RMX query. Servers/zone - tables may currently use TXT entries but SHOULD use RMX entries in - future. - -7.2. RMX Records - - - - -Hadmut Danisch Experimental [Page 17] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - -7.2.1. Overall structure - - Each entry starts with an octet containting the entry type and the - negation flag: - - +---+---+---+---+---+---+---+---+------ - | N | Entry Type Code | Parameters... - +---+---+---+---+---+---+---+---+------ - - N If this bit (MSB) is set, an IP address - matching this entry is not authorized, - but explicitely rejected. See entry - type descriptions for details. - - Entry Type A 7bit number simply determining the entry - type. - - - Currently, entries do not have an explicit length field, the entry - length is determined implicitely by the entry type. Applications - are required to abort if an unknown entry type is found, instead of - skipping unknown entries. - -7.2.2. Record encoding - - A RMX record is simply a concatenation of RMX entries. - -7.2.3. Encoding of IPv4 and IPv6 address ranges - - After the entry type tag as described above, one octet follows - giving the length L of the bit sequence. Then a sequence of exactly - as many octets follows as needed to carry L bits of information (= - trunc((L+7)/8) ). - - +---+---+---+---+---+---+---+---+ - | N | Entry Type Code (1 or 2) | - +---+---+---+---+---+---+---+---+ - | Length Field L | - +---+---+---+---+---+---+---+---+ - | Bit Field | - / ((L+7)/8) Octets / - +---+---+---+---+---+---+---+---+ - - -7.2.4. Encoding of DNS - - After the entry type tag immediately follows a DNS encoded and - compressed [3] domain name. - - - -Hadmut Danisch Experimental [Page 18] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - +---+---+---+---+---+---+---+---+ - | N | Entry Type Code (3..5) | - +---+---+---+---+---+---+---+---+ - | Length Field L | - +---+---+---+---+---+---+---+---+ - | Encoded DNS | - / Name as described in RFC1035 / - +---+---+---+---+---+---+---+---+ - - In contrast to earlier versions of this draft, the DNS name cannot - be compressed, since this would cause decompression errors when a - DNS server is part of the query chain which does not know this - particular RR type. - -7.2.5. Encoding of unused and full query - - These entries do not contain parameters and does not allow the - negation flag. So the encoding is quite simple: - - +---+---+---+---+---+---+---+---+ - | 0 | Entry Type Code (6 or 7)| - +---+---+---+---+---+---+---+---+ - - - -7.2.6. Additional Records - - In order to avoid the need of a second query to resolve the given - host name, a DNS server should enclose the A record for that domain - name in the additional section of the additional section of the DNS - reply, if the server happens to be authoritative. - - In order to avoid the need of a second query to resolve the given - host name, a DNS server should enclose the APL record for that - domain name in the additional section of the additional section of - the DNS reply, if the server happens to be authoritative. - - - -8. Message Headers - - An RMX query must be followed by any kind of action depending on - the RMX result. One action might be to reject the message. Another - action might be to add a header line to the message body, thus - allowing MUAs and delivery programs to filter or sort messages. - - In future, the RMX result might be melted into the Received: header - line. - - - -Hadmut Danisch Experimental [Page 19] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - The details of such entries are to be discussed. As a proposal the - following form is suggested: - - X-RMX: RESULT addr ADDRESS by HOST on DATE mechanism MECHANISM - - where - - RESULT is one of "Granted", "Denied", "NotInRMX", "NoRMX", - "TempFail", "BadData", "Trusted". - - ADDRESS is the IP address of the sending machine - - HOST is the name of the machine performing the RMX query. - - DATE is the date of the query. - - MECHANISM is the RMX method used to authorize the sender. - - - -9. SMTP error messages - - If a message is rejected because of RMX records, an error message - should be issued which explains the details. It is to be discussed - whether new SMTP error codes are to be defined. - - -10. Message relaying and forwarding - -10.1. Problem description - - Message forwarding and relaying means that an MTA which received an - e-mail by SMTP does not deliver it locally, but resends the message - - usually unchanged except for an additional Received header line - and maybe the recipient's address rewritten - to the next SMTP MTA. - Message forwarding is an essential functionality of e-mail - transport services, for example: - - - Message transport from outer MX relay to the intranet - - Message forwarding and Cc-ing by .forward or .procmail-alike - mechanisms - - Mailing list processing - - Message reception by mail relays with low MX priority, - usually provided by third parties as a stand-by service - in case of relay failure or maintenance - - "Forwarding" and "Bouncing" as a MUA functionality - - In all these cases a message is sent by SMTP from a host which is - - - -Hadmut Danisch Experimental [Page 20] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - not covered by the original sender domain's RMX records. While the - RMX records would forbid accepting this message, it still must be - accepted. The following subsections explain how to cope with - relaying. - -10.2. Trusted relaying/forwarding - - In some cases the receiving MTA trusts the sending MTA to not fake - messages and to already have checked the RMX records at message - reception. As a typical example, a company might have an outer mail - relay which receives messages from the Internet and checks the RMX - records. This relay then forwards the messages to the different - department's mail servers. It does not make sense for these - department mail servers to check the RMX record, since the RMX - records have already been checked and - since the message was - relayed by the outer relay - always would deny the message. In this - case there is a trust relationship between the department relays - and the outer relay. So RMX checking is turned off for trusted - relays. In this example, the department relays would not check - messages from the outer relay (but for intranet security, they - could still check RMX records of the other departments sub-domains - to avoid internal forgery between departments). - - Another common example are the low-priority MX relays, which - receive and cache e-mails when the high-priority relays are down. - In this case, the high-priority relay would trust the low-priority - relay to have verified the sender authorization and would not - perform another RMX verification (which would obviously fail). - - When a relay forwards a message to a trusting machine, the envelope - sender address should remain unchanged. - -10.3. Untrusted relaying/forwarding - - If the receiving MTA does not trust the forwarding MTA, then there - is no chance to leave the sender envelope address unchanged. At a - first glance this might appear impracticable, but this is - absolutely necessary. If an untrusted MTA could claim to have - forwarded a message from a foreign sender address, it could have - forged the message as well. Spammers and forgers would just have to - act as such a relay. - - Therefore, it is required that, when performing untrusted - forwarding, the envelope sender address has to be replaced by the - sender address of someone responsible for the relaying mechanism, - e.g. the owner of the mailing list or the mail address of the user - who's .forward caused the transmission. It is important to stress - that untrusted relaying/forwarding means taking over responsibility - - - -Hadmut Danisch Experimental [Page 21] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - for the message. It is the idea of RMX records to tie - responsibility to message transmission. Untrusted relaying without - replacing the sender address would mean to transmit without taking - responsibility. - - The disadvantage is that the original sender address is lost. - Therefore, whenever a sender address replacement happens, the - Received-Line must contain the old address. Many of today's MTAs - already insert the envelope recipient address, but not the sender - address into the Received header line. It seems reasonable to - require every Received line to include both the sender and - recipient address of the incoming SMTP connection. - - -11. Security Considerations - -11.1. Draft specific considerations - -11.1.1. Authentication strength - - It is important to stress, that the suggested method does not - provide high level security and does not completely prevent forged - e-mails or spam under any circumstances. It is a robust, but not - highly reliable and completely secure security mechanism. Keep in - mind that it is based on DNS, and DNS is not secure today. - Authorization is based on the IP address. The very same machine - with the very same IP address could be authorized to send e-mail - with a given sender address and sending spam at the same time. - Maybe because several users are logged in. Or because several - customers use the same relay of the same ISP, where one customer - could use the sender address of a different customer. It is up to - the ISP to prevent this or not. Machines can still be hijacked. - Spammers are also domain owners. They can simply use their own - domain and authorize themselves. You will always find people on the - world who do not care about security and open their relays and RMX - records for others to abuse them. RMX is to be considered as a - very cheap and simple light weight mechanism, which can - nevertheless provide a significant improvement in mail security - against a certain class of attacks, until a successor of SMTP has - been defined and commonly accepted. - -11.1.2. Where Authentication and Authorization end - - Previous versions of RMX records did not cover the local part of - the e-mail address, i.e. what's on the left side of the @ sign. - This is still to be discussed. Authentication and authorization are - limited to the sending MTA's IP address. The authentication is - limited to the TCP functionality, which is sufficient for light - - - -Hadmut Danisch Experimental [Page 22] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - weight authentication. The RMX records authorize the IP address of - the sending host only, not the particular sender of the message. So - if a machine is authorized to use sender addresses of more than a - single domain, the authentication scheme does not prevent that any - user on this machine can send with any of these domains. RMX is not - a substitute for the host security of the involved machines. - - The proposed authentication scheme can be seen as a "half way - authentication": It does not track back an e-mail to the effective - sender. It tracks only half of the way, i. e. it tracks back to the - domain and it's DNS administrators who authorized that particular - sender IP address to use it for sending e-mail. How the party - responsible for that domain performs user authentication, whom it - grants access to, how it helds people responsible for abuse, is - completely left as the private business of those who are in charge - of that domain. So this draft does not interfere with the domain's - individual security policy or any legislation about such policies. - On the other hand, the proposed authentication scheme does not give - any statement about the nature and quality of the domain's security - policy. This is an essential feature of the proposal: E-mail - authentication must be deployed world wide, otherwise it won't do - the job. Any security scheme interfering with the local - legislations or the domain's security policy will not be accepted - and can't effectively deployed. Therefore, the security policy must - remain the domain's private business, no matter how lousy the - policy might be. - - In order to achieve this and to make use of the only existing world - wide Internet directory scheme (DNS), the approach of this proposal - is to just ignore the local part of the sender address (i.e. what's - left of the @ part) and limit view to the domain part. After all, - that's what we do anyway when delivering to a given address with - SMTP. - -11.1.3. Vulnerability of DNS - - DNS is an essential part of the proposed authentication scheme, - since it requires any directory service, and DNS is currently the - only one available. Unfortunately, DNS is vulnerable and can be - spoofed and poisoned. This flaw is commonly known and weakens many - network services, but for reasons beyond that draft DNS has not - been significantly improved yet. After the first version of this - draft, I received several comments who asked me not to use DNS - because of its lack of security. I took this into consideration, - but came to the conclusion that this is unfeasible: Any - authentication scheme linked to some kind of symbolic identity (in - this case the domain name) needs some kind of infrastructure and - trusted assignment. There are basically two ways to do it: Do it - - - -Hadmut Danisch Experimental [Page 23] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - yourself and trust nobody else, or let someone else do it. There - are methods to do it the former way, e.g. to give someone some kind - of authentication information after a first successful e-mail - exchange, e.g. some kind of cookie or special e-mail address. This - is certainly interesting and powerful, but it does not solve the - problem on a world wide scale and is far to complicated and error - prone for the average user, i. e. 99% of the users. - - The latter method to let someone else do the symbolic name - assignment and create the authentication framework is well known. - It context of public key cryptography, this is called a Public Key - Infrastructure (PKI). On of the best known facts about PKIs is - that, until now, we don't have any covering a significant part of - the Internet. And we won't have any in near future. The complexity - is far too high, it is too expensive, and it involves cooperation - of every single user, which is simply unrealistic and extremely - error prone. So what do we have we can use? All we have is the DNS - and the Whois database. And we have countries who don't allow - cryptography. So the proposal was designed to use DNS without - cryptography. It does not avoid DNS because of its vulnerability, - it asks for a better DNS, but accepts the DNS as it is for the - moment. Currently there are two main threats caused by the DNS - weakness: - - - A spammer/forger could spoof DNS in order to gain false - authorization to send fake e-mails. - - - An attacker could spoof DNS in order to block delivery from - authorized machines, i. e. perform a Denial of Service attack. - - The first one is rather unrealistic, because it would require an - average spammer to poison a significant part of the DNS servers of - its victims. A spammer sending messages to one million receipients - would need to poison at least 1-10% which is 10,000 to 100,000 - receipient's DNS servers. This should be unfeasible in most cases. - - In contrast, the second threat is a severe one. If an attacker - wanted to block messages from one company to another, he just needs - to poison the recipients DNS server with a wrong RMX record in - order to make the recipient's SMTP machine reject all messages. And - this is feasible since the attacker needs to poison only a single - DNS server. But does this make SMTP more vulnerable? No. Because - the attacker can already do even more without RMX. By poisoning the - sender's DNS server with wrong MX records, the attacker can also - block message delivery or even redirect the messages to the - attacker's machine, thus preventing any delivery error messages and - furthermore getting access to the messages. - - - - -Hadmut Danisch Experimental [Page 24] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - As a consequence, e-mail delivery by SMTP requires a better DNS - anyway. The requirements are not significantly expanded by RMX. - -11.1.4. Sneaking RMX attack? - - While writing a test implementation, a certain kind of attack came - into my mind. I'm still not sure, whether this attack is possible - on any DNS server, but I believe it should be mentioned: - - Imagine an unauthorized sender is sending a forged mail (e.g. - spam). At connection time, before querying the RMX record, the - receiving MTA usually performs a PTR query for the IP address of - the sending MTA. If the sender has control over the authoritative - name server for that particular IP address, the sender could give a - normal PTR answer, but could append a wrong RMX, APL, or A record - in the additional section of the query. A subsequent RMX query - could receive wrong DNS data if the DNS server used by the - receiving MTA accepted those forged records. - -11.1.5. Open SMTP relays - - Open SMTP relays (i.e. machines who accept any e-mail message from - anyone and deliver to the world) abused by spammers are a one of - the main problems of spam defense and sender backtracking. In most - cases this problem just vanishes because foreign open relay - machines will not be covered by the RMX records of the forged - sender address. But there are two special cases: - - If the spammer knows about a domain which authorizes this - particular machine, that domain can be used for forgery. But in - this case, the IP address of the relay machine and the RMX records - of the domain track back to the persons responsible. Both can be - demanded to fix the relay or remove the RMX record for this - machine. An open relay is a security flaw like leaving the machine - open for everybody to login and send random mails from inside. Once - the administrative persons refuse to solve the problem, they can be - identified as spammers and held responsible. - - The second special case is when a domain authorizes all IP - addresses by having the network 0.0.0.0/0 in the RMX/APL record. In - this case, open relays don't make things worse. It's up to the - recipient's MTA to reject mails from domains with loose security - policies. - -11.1.6. Unforged Spam - - This proposal does not prevent spam (which is, by the way, not yet - exactly defined), it prevents forgery. Since spam is against law - - - -Hadmut Danisch Experimental [Page 25] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - and violates the recipients rights, spam depends on untracability - of the sender. In practice the sender forges the sender address - (other cases see below). This proposal is designed to detect such - forgeries. - - However, the RMX approach is rendered ineffective, if the sender - doesn't forge. If the sender uses just a normal address of it's own - domain, this is just a plain, normal e-mail, which needs to be let - through. Since it is up to the human's taste whether this is spam - or not, there's no technical way to reliably identify this as spam. - But since the sender domain is known, this domain can be - blacklisted or legal steps can be gone into. - -11.1.7. Reliability of Whois Entries - - Once the RMX infrastructure gets deployed, what's the security - gain? It allows to determine the domain which's DNS zone - authorized the sending machine. What's that good for? There are - some immediate uses of the domain name, e.g. in black- and - whitelisting. But in most cases this is just the starting point of - further investigations, either performed automatically before - message acceptance, or manually after spam has been received and - complainted about. - - The next step after determining the domain is determining the - people responsible for this domain. This can sometimes be achieved - by querying the Whois databases. Unfortunately, many whois entries - are useless because they are incomplete, wrong, obsolete, or in - uncommon languages. Furthermore, there are several formats of - address informations which make it difficult to automatically - extract the address. Sometimes the whois entry identifies the - provider and not the owner of the domain. Whois servers are not - built for high availability and sometimes unreachable. - - Therefore, a mandatory standard is required about the contents and - the format of whois entries, and the availability of the servers. - After receiving the MAIL FROM SMTP command with the sender envelope - address, the receiving MTA could check the RMX record and Whois - entry. If it doesn't point to a real human, the message could be - rejected and an error message like "Ask your provider to fix your - Whois entry" could be issued. Obviously, domain providers must be - held responsible for wrong entries. It might still be acceptable to - allow anonymous domains, i. e. domains which don't point to a - responsible human. But it is the receivers choice to accept e-mails - from such domains or not. - -11.1.8. Hazards for Freedom of Speech - - - - -Hadmut Danisch Experimental [Page 26] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - Currently, some governments try to enforce limitations of internet - traffic in order to cut unwanted content providers from the - network. Some of these governments try to hide a whole country - behind firewalls, others try to force Internet providers to poison - DNS servers with wrong A records for web servers, e.g. one county - administration in Germany tries to do so. If message reception - depends on DNS entries, the same governments will try to block not - only HTTP, but SMTP also. - - However, since most MTAs already reject messages from unresolvable - domain names this is not a new threat. - -11.2. General Considerations about spam defense - - After discussing security requirements of the proposal, now the - security advantages of the RMX approach over content based filters - will be explained. Basically, there are three kinds of content - filters: - - - Those who upload the message or some digest to an external - third party and ask "Is this spam"? - - - Those who download a set of patterns and rules from a third - party and apply this set to incoming messages in order to - determine whether it is spam. - - - Those who are independent and don't contact any third party, - but try to learn themselves what is spam and what isn't. - - - The message filters provided by some e-mail service providers are - usually not a kind of their own, but a combination of the first two - kinds. - -11.2.1. Action vs. reaction - - Content filters suffer from a fundamental design problem: They are - late. They need to see some content of the same kind before in - order to learn and to block further distribution. - - This works for viruses and worms, which redistribute. This doesn't - work for spam, since spam is usually not redistributed after the - first delivery. When the filters have learned or downloaded new - pattern sets, it's too late. - - This proposal does not have this problem. - -11.2.2. Content based Denial of Service attacks - - - -Hadmut Danisch Experimental [Page 27] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - All three kinds of content filters, but especially the second and - the third kind are vulnerable to content based Denial of Service - attacks. - - If some kind of third party (e.g. non-democratic government, - intellectual property warriors, religious groups, military, secret - services, patriots, public relation agents, etc.) wants certain - contents not to be distributed, they could either poison the - pattern/rule databases or feed wrong sets to particular receivers. - - Such pattern/rule sets are the perfect tool for censoring e-mail - traffic and denial of service attacks by governments and other - parties, and a similar threat are virus filters. E. g. the content - industry could demand to teach all virus and spam filters to delete - all e-mails containing the URL of an MP3 web server outside the - legislations. Software manufacturers could try to block all e-mails - containing software license keys, thus trying to make unallowed - distribution more difficult. Governments could try to block - distribution of unwanted informations. - - This proposal does not have this problem. - - -12. Privacy Considerations - - (It was proposed on the 56th IETF meeting to have a privacy section - in drafts and RFCs.) - -12.1. Draft specific considerations - -12.1.1. No content leaking - - Since the RMX approach doesn't touch the contents of a message in - any way, there is obviously no way of leaking out any information - about the content of the message. RMX is based solely on the - envelope recipient address. However, methods to fix problems not - covered by RMX might allow content leaking, e.g. if the acceptance - of a message with an empty sender address requires the reference to - the message id of an e-mail recently sent, this allows an attacker - to verify whether a certain message was delivered from there. - -12.1.2. Message reception and sender domain - - Message delivery triggers RMX and APL requests by the recipient. - Thus, the admin of the DNS server or an eavesdropper could learn - that the given machine has just received a message with a sender - from this address, even if the SMTP traffic itself had been - encrypted. - - - -Hadmut Danisch Experimental [Page 28] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - However, most of today's MTAs do query the MX and A records of the - domain after the MAIL FROM command, so this is not a real new - threat. - -12.1.3. Network structure - - Since RMX and its associated APL records provide a complete list of - all IP addresses of hosts authorized to send messages from this - address, they do reveal informations about the network structure - and maybe the lifestyle of the domain owner, since a growing number - of domains are owned by single persons or families. E.g. the RMX - records could reveal where someone has his job or spends his time - at weekends. - - If such informations are to be kept secret, it is the user's job to - not sent e-mails from there and to relay them from non-compromising - IP addresses. - -12.1.4. Owner information distribution - - As described above, RMX depends partly on the reliability of the - whois database entries. It does not make anonymous domains - impossible, but it requires to keep the database entries "true", i. - e. if a whois entry does not contain informations about the - responsible person, this must be unambigously labeled as anonymous. - It must not contain fake names and addresses to pretend a non- - existing person. However, since most Internet users on the world - feel extremely annoyed by spam, they will urge their MTA admin to - reject messages from anonymous domains. The domain owner will have - the choice to either remain anonymous but be not able to send e- - mail to everyone in the world, or to be able but to reveal his - identity to everyone on the world. - - It would be possible to provide whois-like services only to - recipients of recent messages, but this would make things too - complicated to be commonly adopted. - -12.2. General Considerations about spam defense - -12.2.1. Content leaking of content filters - - As described above in the Security chapter, there are spam filters - which inherently allow leakage of the message body. Those filters - upload either the message body, or in most cases just some kind of - checksum to a third party, which replies whether this is to be seen - as spam or not. The idea is to keep a databases of all digests of - all messages. If a message is sent more often than some threshold, - it is to be considered as a mass mail and therefore tagged as spam. - - - -Hadmut Danisch Experimental [Page 29] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - While the digest itself does not reveal the content of the message, - it perfectly reveals where a particular message has been delivered - to. If a government finds just a single unwanted message, if a - software manufacturer finds a single message with a stolen product - license key, if someone finds a message with unpatriotic content, - it takes just a single database lookup to get a list of all people - who received this particular message. Content filters with digest - upload are the perfect "Big Brother". - -12.2.2. Black- and Whitelists - - Some proposals against spam are based on a central database of - white- or blacklisted IP addresses, Sender names, Message IDs or - whatever. Again, there is a central database which learns who has - received which e-mail or from which sender with every query. This - allows tracking relations between persons, which is also a breach - of privacy. - - - -13. Deployment Considerations - -13.1. Compatibility - -13.1.1. Compatibility with old mail receivers - - Since the suggested extension doesn't change the SMTP protocol at - all, it is fully compatible with old mail receivers. They simply - don't ask for the RMX records and don't perform the check. - -13.1.2. Compatibility with old mail senders - - Since the SMTP protocol is unchanged and the SMTP sender is not - involved in the check, the method is fully compatible with old mail - senders. - -13.1.3. Compatibility with old DNS clients - - Since the RMX is a new RR, the existing DNS protocol and zone - informations remain completely untouched. - - If RMX is provided as a TXT record instead, it must be ensured that - no other software is misinterpreting this entry. - -13.1.4. Compatibility with old DNS servers - - Full compatibility: If the server does not support RMX records, RMX - in TXT records can be used. - - - -Hadmut Danisch Experimental [Page 30] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - -13.2. Enforcement policy - - Obviously, for reasons of backward compatibility and smooth - introduction of this scheme, RMX records can't be required - immediately. Domains without RMX records must temporarily be - treated the same way as they are treated right now, i.e. e-mail - must be accepted from anywhere. But once the scheme becomes - sufficiently widespread, mail relays can start to refuse e-mails - with sender addresses from domains without RMX records, thus - forcing the owner of the domain to include a statement of - authorization into the domain's zone table. Domain owners will - still be free to have an RMX record with a network and mask - 0.0.0.0/0, i.e. to allow e-mails with that domain from everywhere. - On the other hand, mail receivers will be free to refuse mails from - domains without RMX records or RMX records which are too loose. - Advanced MTAs might have a configuration option to set the maximum - number of IP addresses authorized to use a domain. E-mails from a - domain, which's RMX records exceed this limit, would be rejected. - For example, a relay could reject e-mails from domains which - authorize more than 8 IP addresses. That allows to accept e-mails - only from domains with a reasonable security policy. - - - -14. General considerations about fighting spam - - Is there a concise technical solution against spam? Yes. - - Will it be deployed? Certainly not. - - Why not? Because of the strong non-technical interests of several - parties against a solution to the problem, as described below. - Since these are non-technical reasons, they might be beyond the - scope of such a draft. But since they are the main problems that - prevent fighting spam, it is unavoidable to address them. This - chapter exists temporarily only and should support the discussion - of solutions. It is not supposed to be included in a later RFC. - -14.1. The economical problem - - As has been recently illustrated in the initial session of the - IRTF's Anti Spam Research Group (ASRG) on the 56th IETF meeting, - sending spam is a business with significant revenues. - - But a much bigger business is selling Anti-Spam software. This is a - billion dollar market, and it is rapidly growing. Any simple and - effective solution against spam would defeat revenues and drive - several companies into bankrupt, would make consultants jobless. - - - -Hadmut Danisch Experimental [Page 31] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - Therefore, spam is essential for the Anti-Spam business. If there - is no spam, then no Anti-Spam software can be sold, similar to the - Anti-Virus business. There are extremely strong efforts to keep - this market growing. Viruses, Worms, and now spam are just perfect - to keep this market alive: It is not sufficient to just buy a - software. Databases need to be updated continuously, thus making - the cash flow continuously. Have a single, simple, and permanent - solution to the problem and - boom - this billion dollar market is - dead. - - That's one of the reasons why people are expected to live with - spam. They have to live with it to make them buy Anti-Spam - software. Content filters are perfect products to keep this market - alive. - -14.2. The POP problem - - Another problem is the history of mail delivery. Once upon a time, - there used to be very few SMTP relays which handled the e-mail - traffic of all the world, and everybody was happy with that. Then - odd things like Personal Computers, which are sometimes switched - off, portable computers, dynamicly assigned IP addresses, IP access - from hotel rooms, etc. was invented, and people became unhappy, - because SMTP does not support delivery to such machines. To make - them happy again, the Post Office Protocol[4] was invented, which - turned the last part of message delivery from SMTP's push style - into a pull style, thus making virtually every computer on the - world with any random IP address a potential receiver of mails for - random domains. Unfortunately, only receiving e-mail was covered, - but sending e-mail was left to SMTP. - - The result is that today we have only very few SMTP relays pointed - to by MX records, but an extreme number of hosts sending e-mail - with SMTP from any IP address with sender addresses from any - domain. Mail delivery has become very asymmetric. Insecurity, - especially forgeability, has become an essential part of mail - transport. - - That problem could easily be fixed: Use protocols which allow - uploading of messages to be delivered. If a host doesn't receive - messages by SMTP, it shouldn't deliver by SMTP. Mail delivery - should go the same way back that incoming mail went in. This is - not a limitation to those people on the road who plug their - portable computer in any hotel room's phone plug and use any - provider. If there is a POP server granting download access from - anywhere, then the same server should be ready to accept uploading - of outgoing messages. - - - - -Hadmut Danisch Experimental [Page 32] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - But as I saw from the comments on the first version of this draft, - people religiously insist on sending e-mail with their domain from - any computer with any IP address in the world, e.g. when visiting a - friend using her computer. It appears to be impossible to convince - people that stopping mail forgery requires every one of them to - give up forging. - -14.3. The network structure problem - - A subsequent problem is that many organisations failed to implement - a proper mail delivery structure and heavily based their network on - this asymmetry. I received harsh comments from Universities who - were unable to give their network a good structure. While they do - have a central mail relay for incoming mail to the universities - domain, they developed a structure where every member of the - University randomly sends e-mails with that University's domain as - a sender address from home or everywhere in the world with any - dynamically assigned IP address from any provider. So this domain - is to be used from every possible IP address on earth, and they are - unable to operate any authentication scheme. Furthermore, they were - unable to understand that such a policy heavily supports spam and - that they have to expect that people don't accept such e-mails - anymore once they become blacklisted. - - As long as organisations insist on having such policies, spammers - will have a perfect playground. - -14.4. The mentality problem - - Another problem is the mentality of many internet users of certain - countries. I received harsh comments from people who strongly - insisted on the freedom to send any e-mail with any sender address - from anywhere, and who heavily refused any kind of authentication - step or any limitation, because they claimed that this would - infringe their constitutional "Freedom of speech". They are - undeviatingly convinced that "Freedom of speech" guarantees their - right to talk to everybody with any sender address, and that is has - to be kept the recipient's own problem to sort out what he doesn't - want to read - on the recipient's expense. - - It requires a clear statement that the constitutional "Freedom of - Speech" does not cover molesting people with unsolicited e-mail - with forged sender address. - -14.5. The identity problem - - How does one fight against mail forgery? With authentication. What - is authentication? In simple words: Making sure that the sender's - - - -Hadmut Danisch Experimental [Page 33] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - - real identity meets the recipients idea of who is the sender, based - on the sender address which came with the message. - - What is identity? It is the main problem. Several countries have - different ideas of "identity", which turn out to be somehow - incompatible. In some countries people have identity cards and - never change their name and birthday. Identities are created by - human birth, not by identity changes. Other countries do not have - such a tight idea about identity. People's temporary identity is - based on nothing more than a driving license and a social security - number. With this background, it is virtually impossible to create - a trustworthy PKI covering all Internet users. I learned that it is - extremely difficult to convince some people to give up random e- - mail sending. - -14.6. The multi-legislation problem - - Many proposals about fighting spam are feasible under certain - legislations only, and are inacceptable under some of the - legislations. But a world wide applicable method is required. - That's why the approach to ask everone on the world to sign - messages with cryptographic keys is not feasible. - - -Implementation and further Information - - Further informations and a test implementation are available at - - http://www.danisch.de/work/security/antispam.html - http://www.danisch.de/software/rmx/ - - - Additional informations and a technology overview are also - available at - - http://www.mikerubel.org/computers/rmx_records/ - - -References - - - -1. S. Bradner, "Key words for use in RFCs to Indicate Requirement Lev- - els," RFC 2119 (March 1997). - -2. J. Klensin, "Simple Mail Transfer Protocol," RFC 2821 (April 2001). - - - - - -Hadmut Danisch Experimental [Page 34] - -INTERNET-DRAFT DNS RMX RR Oct 2003 - - -3. P. Mockapetris, "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION," - RFC 1035 (November 1987). - -4. J. Myers, M. Rose, "Post Office Protocol - Version 3," RFC 1939 - (May 1996). - - -Draft History - - 00 Dec 2002 - 01 Apr 2003 - 02 Jun 2003 - 03 Oct 2003 - -Author's Address - - Hadmut Danisch - - Tennesseeallee 58 - 76149 Karlsruhe - Germany - - Phone: ++49-721-843004 or ++49-351-4850477 - E-Mail: rfc@danisch.de - -Comments - - Please send comments to rfc@danisch.de. - -Expiry - - This drafts expires on Apr 1, 2004. - - - - - - - - - - - - - - - - - - - -Hadmut Danisch Experimental [Page 35] - diff --git a/doc/draft/draft-dnsext-opcode-discover-02.txt b/doc/draft/draft-dnsext-opcode-discover-02.txt deleted file mode 100644 index 7b5e8cc445..0000000000 --- a/doc/draft/draft-dnsext-opcode-discover-02.txt +++ /dev/null @@ -1,241 +0,0 @@ - -IETF DNSEXT WG Bill Manning -draft-dnsext-opcode-discover-02.txt ep.net - Paul Vixie - ISC - 13 Oct 2003 - - - The DISCOVER opcode - -This document is an Internet-Draft and is subject to all provisions of -Section 10 of RFC2026. - -Comments may be submitted to the group mailing list at "mdns@zocalo.net" -or the authors. - -Distribution of this memo is unlimited. - -Internet-Drafts are working documents of the Internet Engineering Task -Force (IETF), its areas, and its working groups. Note that other groups -may also distribute working documents as Internet-Drafts. - -Internet-Drafts are draft documents valid for a maximum of six months and -may be updated, replaced, or obsoleted by other documents at any time. It -is inappropriate to use Internet-Drafts as reference material or to cite -them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - -The capitalized keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", -"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this -document are to be interpreted as described in RFC 2119 - -0. Abstract: - - The QUERY opcode in the DNS is designed for unicast. With the - development of multicast capabilities in the DNS, it is desireable - to have a more robust opcode for server interactions since a single - request may generate replies from multiple responders. So DISCOVER - is defined to deal with replies from multiple responders. - - As such, this document extends the core DNS specifications to allow - clients to have a method for coping with replies from multiple - responders. Use of this new opcode may facilitate DNS operations in - modern networking topologies. A prototype of the DISCOVER opcode - was developed during the TBDS project (1999-2000), funded under DARPA - grant F30602-99-1-0523. - -1. Introduction: - - This document describes an experimental extension to the DNS to receive - multiple responses which is the likely result when using DNS that has - enabled multicast queries. This approach was developed as part of the - TBDS research project, funded under DARPA grant F30602-99-1-0523. The - full processing rules used by TBDS are documented here for possible - incorporation in a future revision of the DNS specification." - -2. Method: - - DISCOVER works like QUERY except: - - 1. it can be sent to a broadcast or multicast destination. QUERY - isn't defined for non-unicast, and arguably shouldn't be. - - 2. the Question section, if present, has - tuples. TBDS tried to augment this structure as follows: - . While this worked for our purposes in - TBDS, it is cleaner to place the SRV question in a separate pass. - - 3. if QDCOUNT equals 0 then only servers willing to do recursion should - answer. Other servers must silently discard the DISCOVER request. - - 4. if QDCOUNT is not equal to 0 then only servers who are authoritative - for the zones named by some QNAME should answer. - - 5. responses may echo the request's Question section or leave it blank, - just like QUERY. - - 6. responses have standard Answer, Authority, and Additional sections. - e.g. the response is the same as that to a QUERY. It is desireable - that zero content answers not be sent to avoid badly formed or - unfulfilled requests. Responses should be sent to the unicast - address of the requester and the source address should reflect - the unicast address of the responder. - - Example usage for gethostby{name,addr}-style requestors: - - Compute the zone name of the enclosing in-addr.arpa, ip6.int, or - ip6.arpa domain. - - DISCOVER whether anyone in-scope is authoritative for this zone. - - If so, query these authoritative servers for local - in-addr/ip6 names. - - If not, DISCOVER whether there are recursive servers available. - - If so, query these recursive servers for local - in-addr/ip6 names. - - So, a node will issue a multicast request with the DISCOVER opcode at - some particular multicast scope. Then determine, from the replies, - whether there are any DNS servers which are authoritative (or support - recursion) for the zone. Replies to DISCOVER requests MUST set the - Recursion Available (RA) flag in the DNS message header. - - It is important to recognize that a requester must be prepared to - receive multiple replies from multiple responders. We expect that - there will be a single response per responder. - - Once one learns a host's FQDN by the above means, repeat the process - for discovering the closest enclosing authoritative server of such - local name. - - Cache all NS and A data learned in this process, respecting TTL's. - - TBDS usage for SRV requestors: - - Do the gethostbyaddr() and gethostbyname() on one's own link-local - address, using the above process. - - Assume that the closest enclosing zone for which an authority server - answers an in-scope DISCOVER packet is "this host's parent domain". - - Compute the SRV name as _service._transport.*.parentdomain. - - This is a change to the definition as defined in RFC 1034. - A wildcard label ("*") in the QNAME used in a DNS message with - opcode DISCOVER SHOULD be evaluated with special rules. The - wildcard matches any label for which the DNS server data is - authoritative. For example 'x.*.example.com.' would match - 'x.y.example.com.' and 'x.yy.example.com.' provided that the - server was authoritative for 'example.com.' In this particular - case, we suggest the follwing considerations be made: - - getservbyname() can be satisfied by issuing a request with - this computed SRV name. This structure can be - populated by values returned from a request as follows: - - s_name The name of the service, "_service" without the - preceding underscore. - s_aliases The names returned in the SRV RRs in replies - to the query. - s_port The port number in the SRV RRs replies to the - query. If these port numbers disagree - one - of the port numbers is chosen, and only those - names which correspond are returned. - s_proto The transport protocol from named by the - "_transport" label, without the preceding - underscore. - - Send SRV query for this name to discovered local authoritative servers. - - Usage for disconnected networks with no authoritative servers: - - Hosts should run a "stub server" which acts as though its FQDN is a - zone name. Computed SOA gives the host's FQDN as MNAME, "." as the - ANAME, seconds-since-1Jan2000 as the SERIAL, low constants for EXPIRE - and the other timers. Compute NS as the host's FQDN. Compute the - glue as the host's link-local address. Or Hosts may run a - "DNS stub server" which acts as though its FQDN is a zone name. The - rules governing the behavior of this stub server are given elsewhere - [1] [2]. - - Such stub servers should answer DISCOVER packets for its zone, and - will be found by the iterative "discover closest enclosing authority - server" by DISCOVER clients, either in the gethostbyname() or SRV - cases described above. Note that stub servers only answer with - zone names which exactly match QNAME's, not with zone names which - are owned by QNAME's. - - The main deviation from the DNS[3][4] model is that a host (like, say, a - printer offering LPD services) has a DNS server which answers authoritatively - for something which hasn't been delegated to it. However, the only way that - such DNS servers can be discovered is with a new opcode, DISCOVER, which - is explicitly defined to discover undelegated zones for tightly scoped - purposes. Therefore this isn't officially a violation of DNS's coherency - principles. In some cases a responder to DISCOVER may not be traditional - DNS software, it could be special purpose software. - -3. IANA Considerations - - As a new opcode, the IANA will need to assign a numeric value - for the memnonic. The last OPCODE assigned was "5", for UPDATE. - Test implementations have used OPCODE "6". - -4. Security Considerations - - No new security considerations are known to be introduced with any new - opcode, however using multicast for service discovery has the potential - for denial of service, primarly from flooding attacks. It may also be - possible to enable deliberate misconfiguration of clients simply by - running a malicious DNS resolver that claims to be authoritative for - things that it is not. One possible way to mitigate this effect is by - use of credentials, such as CERT resource records within an RR set. - The TBDS project took this approach. - -5. Attribution: - - This material was generated in discussions on the mdns mailing list -hosted by Zocalo in March 2000. Updated by discussion in September/October -2003. David Lawrence, Scott Rose, Stuart Cheshire, Bill Woodcock, -Erik Guttman, Bill Manning and Paul Vixie were active contributors. - -6. Author's Address - - Bill Manning - PO 12317 - Marina del Rey, CA. 90295 - +1.310.322.8102 - bmanning@karoshi.com - - Paul Vixie - Internet Software Consortium - 950 Charter Street - Redwood City, CA 94063 - +1 650 779 7001 - - -7. References - -Informational References: - -[1] Esibov, L., Aboba, B., Thaler, D., "Multicast DNS", - draft-ietf-dnsext-mdns-00.txt, November 2000. Expired - -[2] Woodcock, B., Manning, B., "Multicast Domain Name Service", - draft-manning-dnsext-mdns-00.txt, August 2000. Expired. - -Normative References: -[3] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES", - RFC 1034, November 1987. -[4] Mockapetris, P., "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION", - RFC 1035, November 1987 - - ----------------------------EOL----------------------- - diff --git a/doc/draft/draft-dolmatov-dnsext-dnssec-gost-00.txt b/doc/draft/draft-dolmatov-dnsext-dnssec-gost-00.txt deleted file mode 100644 index 3e08247f69..0000000000 --- a/doc/draft/draft-dolmatov-dnsext-dnssec-gost-00.txt +++ /dev/null @@ -1,370 +0,0 @@ -DNS Extensions working group V.Dolmatov, Ed. -Internet-Draft Cryptocom Ltd. -Intended status: Standards Track April 8, 2009 -Expires: December 31, 2009 - - - Use of GOST signature algorithms in DNSKEY and RRSIG Resource Records - for DNSSEC - draft-dolmatov-dnsext-dnssec-gost-00 - -Status of this Memo - - This Internet-Draft is submitted to IETF in full conformance with the - provisions of BCP 78 and BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on 31 December 2009. - -Copyright Notice - - Copyright (c) 2009 IETF Trust and the persons identified as the - document authors. All rights reserved. - - This document is subject to BCP 78 and the IETF Trust's Legal - Provisions Relating to IETF Documents in effect on the date of - publication of this document (http://trustee.ietf.org/license-info). - Please review these documents carefully, as they describe your rights - and restrictions with respect to this document. - -Abstract - - This document describes how to produce GOST signature and hash algorithms - DNSKEY and RRSIG resource records for use in the Domain Name System - Security Extensions (DNSSEC, RFC 4033, RFC 4034, and RFC 4035). - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . - 2. DNSKEY Resource Records . . . . . . . . . . . . . . . . . . . . - 2.1. Using a public key with existing cryptographic libraries. . - 2.2. GOST DNSKEY RR Example . . . . . . . . . . . . . . . . . . - 3. RRSIG Resource Records . . . . . . . . . . . . . . . . . . . . - 4. DS Resource Records . . . . . . . . . . . . . . . . . . . . . . - 5. NSEC3 Resource Records . . . . . . . . . . . . . . . . . . . . - 6. Deployment Considerations . . . . . . . . . . . . . . . . . . . - 6.1. Key Sizes . . . . . . . . . . . . . . . . . . . . . . . . . - 6.2. Signature Sizes . . . . . . . . . . . . . . . . . . . . . . - 6.3. Digest Sizes . . . . . . . . . . . . . . . . . . . . . . . - 7. Implementation Considerations . . . . . . . . . . . . . . . . . - 7.1. Support for GOST signatures . . . . . . . . . . . . . . . . - 7.2. Support for NSEC3 Denial of Existence . . . . . . . . . . . - 7.2.1. NSEC3 in Authoritative servers . . . . . . . . . . . . - 7.2.2. NSEC3 in Validators . . . . . . . . . . . . . . . . . . - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . - 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . - 10.1. Normative References . . . . . . . . . . . . . . . . . . . - 10.2. Informative References . . . . . . . . . . . . . . . . . . - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . - - -1. Introduction - - The Domain Name System (DNS) is the global hierarchical distributed - database for Internet Naming. The DNS has been extended to use - cryptographic keys and digital signatures for the verification of the - authenticity and integrity of its data. RFC 4033 [RFC4033], RFC 4034 - [RFC4034], and RFC 4035 [RFC4035] describe these DNS Security - Extensions, called DNSSEC. - - RFC 4034 describes how to store DNSKEY and RRSIG resource records, - and specifies a list of cryptographic algorithms to use. This - document extends that list with the signature and hash algorithms - GOST [GOST3410, GOST3411], - and specifies how to store DNSKEY data and how to produce - RRSIG resource records with these hash algorithms. - - Familiarity with DNSSEC and GOST signature and hash - algorithms is assumed in this document. - - The term "GOST" is not officially defined, but is usually used to - refer to the collection of the Russian cryptographic algorithms - GOST R 34.10-2001, GOST R 34.11-94, GOST 28147-89. Since GOST 28147-89 - is not used in DNSSEC, GOST will only refer to GOST R 34.10-2001 - (signatire algorithm) and GOST R 34.11-94 (hash algorithm) in this - document. - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in [RFC2119]. - - -2. DNSKEY Resource Records - - The format of the DNSKEY RR can be found in RFC 4034 [RFC4034]. - - GOST R 34.10-2001 public keys are stored with the algorithm number {TBA1}. - - The public key parameters are those identified by - id-GostR3410-2001-CryptoPro-A-ParamSet (1.2.643.2.2.35.1) [RFC4357]. - The digest parameters for signature are those identified by - id-GostR3411-94-CryptoProParamSet (1.2.643.2.2.30.1) [RFC4357]. - - The wire format of the public key is compatible with RFC 4491 [RFC4491]: - - According to [GOSTR341001], a public key is a point on the elliptic - curve Q = (x,y). - - The wire representation of a public key MUST contain 64 octets, where the - first 32 octets contain the little-endian representation of x and the - second 32 octets contain the little-endian representation of y. This - corresponds to the binary representation of (256||256) from - [GOSTR341001], ch. 5.3. - -2.1. Using a public key with existing cryptographic libraries - - Existing GOST-aware cryptographic libraries at time of this document - writing are capable to read GOST public keys via generic X509 API if the - key is encoded according to RFC 4491 [RFC4491], section 2.3.2. - - To make this encoding from the wire format of a GOST public key, prepend - a key data with the following 37-byte sequence: - - 0x30 0x63 0x30 0x1c 0x06 0x06 0x2a 0x85 0x03 0x02 0x02 0x13 0x30 0x12 - 0x06 0x07 0x2a 0x85 0x03 0x02 0x02 0x23 0x01 0x06 0x07 0x2a 0x85 0x03 - 0x02 0x02 0x1e 0x01 0x03 0x43 0x00 0x04 0x40 - -2.2. GOST DNSKEY RR Example - - The following DNSKEY RR stores a DNS zone key for example.com - - example.com. 86400 IN DNSKEY 256 3 {TBA1} ( RamuUwTG1r4RUqsgXu/xF6B+Y - tJLzZEykiZ4C2Fa1gV1pI/8GA - el2Wm69Cz5h1T9eYAQKFAGwzW - m4Lke0E26aw== ) - -3. RRSIG Resource Records - - The value of the signature field in the RRSIG RR follows the RFC 4490 - [RFC4490] and is calculated as follows. The values for the RDATA fields - that precede the signature data are specified in RFC 4034 [RFC4034]. - - hash = GOSTR3411(data) - - where "data" is the wire format data of the resource record set that is - signed, as specified in RFC 4034 [RFC4034]. Hash MUST be calculated with - GOST R 34.11-94 parameters identified by - id-GostR3411-94-CryptoProParamSet [RFC4357]. - - Signature is calculated from the hash according to the GOST R 34.10-2001 - standard and its wire format is compatible with RFC 4490 [RFC4490]. - Quoting RFC 4490: - - "The signature algorithm GOST R 34.10-2001 generates a digital - signature in the form of two 256-bit numbers, r and s. Its octet - string representation consists of 64 octets, where the first 32 - octets contain the big-endian representation of s and the second 32 - octets contain the big-endian representation of r." - -4. DS Resource Records - - GOST R 34.11-94 digest algorithm is denoted in DS RR by the digest type - {TBA2}. The wire format of a digest value is compatible with RFC 4490 - [RFC4490]. Quoting RFC 4490: - - "A 32-byte digest in little-endian representation." - - The digest MUST always be calculated with GOST R 34.11-94 parameters - identified by id-GostR3411-94-CryptoProParamSet [RFC4357]. - -5. NSEC3 Resource Records - - GOST R 34.11-94 digest algorithm is denoted in NSEC3 RR by the digest type - {TBA2}. The wire format of a digest value is compatible with RFC 4490 - [RFC4490]. Quoting RFC 4490: - - "A 32-byte digest in little-endian representation." - - The digest MUST always be calculated with GOST R 34.11-94 parameters - identified by id-GostR3411-94-CryptoProParamSet [RFC4357]. - -6. Deployment Considerations - -6.1. Key Sizes - - According to RFC4357 [RFC4357] key size of GOST public keys MUST - be 512 bits. - -6.2. Signature Sizes - - According to GOST signature algorithm [GOST3410] size of GOST signature - is 512 bit. - -6.3. Digest Sizes - - According to GOST R 34.11-94 [GOST3411] size of GOST digest is 256 bit. - -7. Implementation Considerations - -7.1. Support for GOST signatures - - DNSSEC aware implementations SHOULD be able to support RRSIG and - DNSKEY resource records created with the GOST algorithms as - defined in this document. - -7.2. Support for NSEC3 Denial of Existence - - RFC5155 [RFC5155] defines new algorithm identifiers for existing - signing algorithms, to indicate that zones signed with these - algorithm identifiers use NSEC3 instead of NSEC records to provide - denial of existence. That mechanism was chosen to protect - implementations predating RFC5155 from encountering resource records - they could not know about. This document does not define such - algorithm aliases, and support for NSEC3 denial of existence is - implicitly signaled with support for one of the algorithms defined in - this document. - -7.2.1. NSEC3 in Authoritative servers - - An authoritative server that does not implement NSEC3 MAY still serve - zones that use GOST with NSEC denial of existence. - -7.2.2. NSEC3 in Validators - - A DNSSEC validator that implements GOST MUST be able to handle - both NSEC and NSEC3 [RFC5155] negative answers. If this is not the - case, the validator MUST treat a zone signed with GOST - as signed with an unknown algorithm, and thus as insecure. - - -8. IANA Considerations - - This document updates the IANA registry "DNS SECURITY ALGORITHM - NUMBERS -- per [RFC4035] " - (http://www.iana.org/assignments/dns-sec-alg-numbers). The following - entries are added to the registry: - Zone Trans. - Value Algorithm Mnemonic Signing Sec. References Status - {TBA1} GOST R 34.10-2001 GOST Y * (this memo) OPTIONAL - - This document updates the RFC 4034 [RFC4034] Digest Types assignment - (RFC 4034, section A.2): - - Value Algorithm Status - {TBA2} GOST R 34.11-94 OPTIONAL - -9. Acknowledgments - - This document is a minor extension to RFC 4034 [RFC4034]. Also, we - try to follow the documents RFC 3110 [RFC3110], RFC 4509 [RFC4509] - and RFC 4357 [RFC4357] for consistency. The authors of and - contributors to these documents are gratefully acknowledged for - their hard work. - - The following people provided additional feedback and text: Dmitry - Burkov, Jaap Akkerhuis, Jelte Jansen and Wouter Wijngaards. - - -10. References - -10.1. Normative References - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", RFC 2119, March 1997. - - [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain - Name System (DNS)", RFC 3110, May 2001. - - [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "DNS Security Introduction and Requirements", - RFC 4033, March 2005. - - [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Resource Records for the DNS Security Extensions", - RFC 4034, March 2005. - - [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Protocol Modifications for the DNS Security - Extensions", RFC 4035, March 2005. - - [GOST3410] "Information technology. Cryptographic data security. - Signature and verification processes of [electronic] - digital signature.", GOST R 34.10-2001, Gosudarstvennyi - Standard of Russian Federation, Government Committee of - the Russia for Standards, 2001. (In Russian) - - [GOST3411] "Information technology. Cryptographic Data Security. - Hashing function.", GOST R 34.11-94, Gosudarstvennyi - Standard of Russian Federation, Government Committee of - the Russia for Standards, 1994. (In Russian) - - [RFC4357] Popov, V., Kurepkin, I., and S. Leontiev, "Additional - Cryptographic Algorithms for Use with GOST 28147-89, - GOST R 34.10-94, GOST R 34.10-2001, and GOST R 34.11-94 - Algorithms", RFC 4357, January 2006. - - [RFC4490] S. Leontiev and G. Chudov, "Using the GOST 28147-89, - GOST R 34.11-94, GOST R 34.10-94, and GOST R 34.10-2001 - Algorithms with Cryptographic Message Syntax (CMS)", - RFC 4490, May 2006. - - [RFC4491] S. Leontiev and D. Shefanovski, "Using the GOST - R 34.10-94, GOST R 34.10-2001, and GOST R 34.11-94 - Algorithms with the Internet X.509 Public Key - Infrastructure Certificate and CRL Profile", RFC 4491, - May 2006. - - - -10.2. Informative References - - [NIST800-57] - Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid, - "Recommendations for Key Management", NIST SP 800-57, - March 2007. - - [RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography - Standards (PKCS) #1: RSA Cryptography Specifications - Version 2.1", RFC 3447, February 2003. - - [RFC4509] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer - (DS) Resource Records (RRs)", RFC 4509, May 2006. - - [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS - Security (DNSSEC) Hashed Authenticated Denial of - Existence", RFC 5155, March 2008. - -Authors' Addresses - - -Vasily Dolmatov, Ed. -Cryptocom Ltd. -Bolotnikovskaya, 23 -Moscow, 117303, Russian Federation - -EMail: dol@cryptocom.ru - -Artem Chuprina -Cryptocom Ltd. -Bolotnikovskaya, 23 -Moscow, 117303, Russian Federation - -EMail: ran@cryptocom.ru - -Igor Ustinov -Cryptocom Ltd. -Bolotnikovskaya, 23 -Moscow, 117303, Russian Federation - -EMail: igus@cryptocom.ru - - Expires December 31, 2009 [Page ] - - diff --git a/doc/draft/draft-durand-dnsop-dynreverse-00.txt b/doc/draft/draft-durand-dnsop-dynreverse-00.txt deleted file mode 100644 index 224e7ad169..0000000000 --- a/doc/draft/draft-durand-dnsop-dynreverse-00.txt +++ /dev/null @@ -1,240 +0,0 @@ -Internet Engineering Task Force Alain Durand -INTERNET-DRAFT SUN Microsystems -Feb 21, 2003 -Expires Aug 2, 2003 - - - - Dynamic reverse DNS for IPv6 - - - - -Status of this memo - - - This memo provides information to the Internet community. It does - not specify an Internet standard of any kind. This memo is in full - conformance with all provisions of Section 10 of RFC2026 [RFC2026]. - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - - -Abstract - - This document describes a method to dynamically generate PTR records - and corresponding A or AAAA records when the reverse path DNS tree is - not populated. - - A special domain dynrev.arpa. is reserved for that purpose. - - -1. Introduction - - In IPv4, the reverse path tree of the DNS under in-addr.arpa. - although not perfectly maintained, is still mostly usable and its - existence is important for a number of applications that relies on - its existence and decent status. Some applications performs some - (very) weak security checks based on it. Mail relays relies on it for - some anti-spams checks an some FTP server will not let you in unless - your IP address resolve properly with a PTR record. - - IPv6 addresses being much longer (and cumbersome) than IPv4 - addresses, it is to fear that the reverse path tree under ip6.arpa. - would not be as well maintained. Also, tools like 6to4, Isatap and - others have made creative use of the 128 bits of an IPv6 address to - automatically embed an IPv4 address to enable seamless connection to - the IPv6 Internet. However, no provision has been made to make sure - the reverse path tree gets automatically updated as well for those - new IPv6 addresses. One step furter, RFC3041 describes a mechanism - to basically use random bits in the bottom part of an IPv6 address to - preserver anonymity. If those addresses are to resolve in the reverse - path tree, it obviously has to be with anonymous data as well. - Another point to note is that home customer ISPs in IPv4 have a - current practice to pre-populate the reverse path tree with names - automatically derived from the IP addresses. This practice is no - longer possible in IPv6, where IP address allocation is not dense as - it is the case in IPv4. The mere size of typical customer allocation - (2^48 according to the recommendation of RFC3177) makes it - impossible. - - Applications that check the existence of PTR records usually follow - this by checking if the name pointed by the PTR resolve in a A (or - AAAA for IPv6) that match the original IP address. Thus the forward - path tree must also include the corresponding data. - - One simple approach of this problem is to simply declare the usage of - the reverse path DNS as described above obsolete. The author believe - this is too strong an approach for now. - - Similarly, a completely different approach would be to deprecate the - usage of DNS for the reverse tree altogether and replace it by - something inspired from ICMP name-info messages. The author believes - that this approached is an important departure from the current - practise and thus not very realistic. Also, there are some concerns - about the the security implications of this method as any node could - easily impersonate any name. This approach would fundamentally change - the underlying assumption of "I trust what has been put in the DNS by - the local administrators" to "I trust what has been configured on - each machine I query directly". - - - -2. Dynamic record generation - - If static pre-population of the tree is not possible anymore and data - still need to be returned to applications using getnameinfo(), the - alternative is dynamic record generation. This can be done is two - places: in the DNS servers responsible for the allocated space (/64 - or /48) in the ip6.arpa. domain. or in the DNS resolvers (either the - sub resolver library or the recursive DNS server). - - 2.1. On the resolver side. - - The resolver, either in the recursive DNS server or in the stub - library could theoretically generate this data. - - In case DNSsec is in place, the recursive DNS server would have to - pretend these records are authentic. - - If the synthesis is done in the stub-resolver library, no record - needs to be actually generated, only the right information needs to - be passed to getnameinfo() and getaddrinfo(). If the synthesis is - done in the recursive DNS server, no modification is required to - existing stub resolvers. - - -2.2. On the server side. - - PTR records could be generated automatically by the server - responsible for the reverse path tree of an IPv6 prefix (a /64 or /48 - prefixes or basically anything in between) when static data is not - available. - - There could be impact on DNSsec as the zone or some parts of the zone - may need to be resigned each time a DNS query is made for an - unpopulated address. This can be seen as a DOS attack on a DNSsec - zone, so server side synthesis is not recommended if DNSsec is - deployed. - - - -3. Synthesis - - The algorithm is simple: Do the normal queries. If the query returns - No such domain, replace this answer by the synthetized one if - possible. - -3.1. PTR synthesis - - The synthetized PTR for a DNS string [X] is simply [X].dynrev.arpa. - where [X] is any valid DNS name. - - The fact that the synthetized PTR points to the dynrev.arpa. domain - is an indication to the applications that this record has been - dynamically generated. - - -3.2. A synthesis - - If [X] is in the form a.b.c.d.in-addr.arpa, one can synthetized an A - record for the string [X].dynrev.arpa. which value is d.c.b.a. with - a,b,c & d being integer [0..255] - - -3.3. AAAA synthesis - - If [X] is in the form - a.b.c.d.e.f.g.h.i.j.k.l.m.n.o.p.q.s.t.u.v.w.x.y.z.A.B.C.D.E.F.in- - addr.arpa, one can synthetized a AAAA record for the string - [X].dynrev.arpa. which value is - FEDC:BAzy:xwvu:tsrq:ponm:lkji:hgfe:dcba with - a,b,c....x,y,z,A,B,C,D,E,F being hexadecimal digits. - - -3.4. Server side synthesis - - If synthesis is done on the server side, PTR could be set not to use - the dynrev.arpa domain but the local domain name instead. It culd be - for instance dynrev.mydomain.com. - - Note also that server side synthesis is not incompatible with - resolver side synthesis. - - - -4. IANA considerations - - The dynrev.arpa. domain is reserved for the purpose of this document. - - - -5. Security considerations - - Section 2. discusses the the interactions with DNSsec. - - - -6. Authors addresses - - Alain Durand - SUN Microsystems, Inc - 17, Network Circle - UMPK17-202 - Menlo Park, CA 94025 - USA - Mail: Alain.Durand@sun.com - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - diff --git a/doc/draft/draft-ietf-dnsext-2929bis-01.txt b/doc/draft/draft-ietf-dnsext-2929bis-01.txt deleted file mode 100644 index fa41e7635e..0000000000 --- a/doc/draft/draft-ietf-dnsext-2929bis-01.txt +++ /dev/null @@ -1,928 +0,0 @@ - -INTERNET-DRAFT Donald E. Eastlake 3rd -Obsoletes RFC 2929, Updates RFC 1183 Motorola Laboratories -Expires: February 2006 August 2005 - - - - Domain Name System (DNS) IANA Considerations - ------ ---- ------ ----- ---- -------------- - - - - -Status of This Document - - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - - Distribution of this draft is unlimited. It is intended to become - the new BCP 42 obsoleting RFC 2929. Comments should be sent to the - DNS Working Group mailing list . - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than a "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/1id-abstracts.html - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html - - - -Abstract - - Internet Assigned Number Authority (IANA) parameter assignment - considerations are given for the allocation of Domain Name System - (DNS) classes, RR types, operation codes, error codes, RR header - bits, and AFSDB subtypes. - - - - - - - - -D. Eastlake 3rd [Page 1] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -Table of Contents - - Status of This Document....................................1 - Abstract...................................................1 - - Table of Contents..........................................2 - - 1. Introduction............................................3 - 2. DNS Query/Response Headers..............................3 - 2.1 One Spare Bit?.........................................4 - 2.2 Opcode Assignment......................................4 - 2.3 RCODE Assignment.......................................5 - 3. DNS Resource Records....................................6 - 3.1 RR TYPE IANA Considerations............................7 - 3.1.1 DNS TYPE Allocation Policy...........................8 - 3.1.2 Special Note on the OPT RR...........................9 - 3.1.3 The AFSDB RR Subtype Field...........................9 - 3.2 RR CLASS IANA Considerations...........................9 - 3.3 RR NAME Considerations................................11 - 4. Security Considerations................................11 - - Appendix: Changes from RFC 2929...........................12 - - Copyright and Disclaimer..................................13 - Normative References......................................13 - Informative References....................................14 - - Authors Addresses.........................................16 - Expiration and File Name..................................16 - - - - - - - - - - - - - - - - - - - - - - - -D. Eastlake 3rd [Page 2] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -1. Introduction - - The Domain Name System (DNS) provides replicated distributed secure - hierarchical databases which hierarchically store "resource records" - (RRs) under domain names. DNS data is structured into CLASSes and - zones which can be independently maintained. See [RFC 1034, 1035, - 2136, 2181, 4033] familiarity with which is assumed. - - This document provides, either directly or by reference, general IANA - parameter assignment considerations applying across DNS query and - response headers and all RRs. There may be additional IANA - considerations that apply to only a particular RR type or - query/response opcode. See the specific RFC defining that RR type or - query/response opcode for such considerations if they have been - defined, except for AFSDB RR considerations [RFC 1183] which are - included herein. This RFC obsoletes [RFC 2929]. - - IANA currently maintains a web page of DNS parameters. See - . - - "IETF Standards Action", "IETF Consensus", "Specification Required", - and "Private Use" are as defined in [RFC 2434]. - - - -2. DNS Query/Response Headers - - The header for DNS queries and responses contains field/bits in the - following diagram taken from [RFC 2136, 2929]: - - 1 1 1 1 1 1 - 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | ID | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - |QR| Opcode |AA|TC|RD|RA| Z|AD|CD| RCODE | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | QDCOUNT/ZOCOUNT | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | ANCOUNT/PRCOUNT | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | NSCOUNT/UPCOUNT | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | ARCOUNT | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - - The ID field identifies the query and is echoed in the response so - they can be matched. - - The QR bit indicates whether the header is for a query or a response. - - -D. Eastlake 3rd [Page 3] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - The AA, TC, RD, RA, AD, and CD bits are each theoretically meaningful - only in queries or only in responses, depending on the bit. However, - many DNS implementations copy the query header as the initial value - of the response header without clearing bits. Thus any attempt to - use a "query" bit with a different meaning in a response or to define - a query meaning for a "response" bit is dangerous given existing - implementation. Such meanings may only be assigned by an IETF - Standards Action. - - The unsigned fields query count (QDCOUNT), answer count (ANCOUNT), - authority count (NSCOUNT), and additional information count (ARCOUNT) - express the number of records in each section for all opcodes except - Update. These fields have the same structure and data type for - Update but are instead the counts for the zone (ZOCOUNT), - prerequisite (PRCOUNT), update (UPCOUNT), and additional information - (ARCOUNT) sections. - - - -2.1 One Spare Bit? - - There have been ancient DNS implementations for which the Z bit being - on in a query meant that only a response from the primary server for - a zone is acceptable. It is believed that current DNS - implementations ignore this bit. - - Assigning a meaning to the Z bit requires an IETF Standards Action. - - - -2.2 Opcode Assignment - - Currently DNS OpCodes are assigned as follows: - - OpCode Name Reference - - 0 Query [RFC 1035] - 1 IQuery (Inverse Query, Obsolete) [RFC 3425] - 2 Status [RFC 1035] - 3 available for assignment - 4 Notify [RFC 1996] - 5 Update [RFC 2136] - 6-15 available for assignment - - New OpCode assignments require an IETF Standards Action as modified - by [RFC 4020]. - - - - - - -D. Eastlake 3rd [Page 4] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -2.3 RCODE Assignment - - It would appear from the DNS header above that only four bits of - RCODE, or response/error code are available. However, RCODEs can - appear not only at the top level of a DNS response but also inside - OPT RRs [RFC 2671], TSIG RRs [RFC 2845], and TKEY RRs [RFC 2930]. - The OPT RR provides an eight bit extension resulting in a 12 bit - RCODE field and the TSIG and TKEY RRs have a 16 bit RCODE field. - - Error codes appearing in the DNS header and in these three RR types - all refer to the same error code space with the single exception of - error code 16 which has a different meaning in the OPT RR from its - meaning in other contexts. See table below. - - RCODE Name Description Reference - Decimal - Hexadecimal - 0 NoError No Error [RFC 1035] - 1 FormErr Format Error [RFC 1035] - 2 ServFail Server Failure [RFC 1035] - 3 NXDomain Non-Existent Domain [RFC 1035] - 4 NotImp Not Implemented [RFC 1035] - 5 Refused Query Refused [RFC 1035] - 6 YXDomain Name Exists when it should not [RFC 2136] - 7 YXRRSet RR Set Exists when it should not [RFC 2136] - 8 NXRRSet RR Set that should exist does not [RFC 2136] - 9 NotAuth Server Not Authoritative for zone [RFC 2136] - 10 NotZone Name not contained in zone [RFC 2136] - 11 - 15 Available for assignment - 16 BADVERS Bad OPT Version [RFC 2671] - 16 BADSIG TSIG Signature Failure [RFC 2845] - 17 BADKEY Key not recognized [RFC 2845] - 18 BADTIME Signature out of time window [RFC 2845] - 19 BADMODE Bad TKEY Mode [RPC 2930] - 20 BADNAME Duplicate key name [RPF 2930] - 21 BADALG Algorithm not supported [RPF 2930] - - 22 - 3,840 - 0x0016 - 0x0F00 Available for assignment - - 3,841 - 4,095 - 0x0F01 - 0x0FFF Private Use - - 4,096 - 65,534 - 0x1000 - 0xFFFE Available for assignment - - 65,535 - 0xFFFF Reserved, can only be allocated by an IETF - Standards Action. - - - -D. Eastlake 3rd [Page 5] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - Since it is important that RCODEs be understood for interoperability, - assignment of new RCODE listed above as "available for assignment" - requires an IETF Consensus. - - - -3. DNS Resource Records - - All RRs have the same top level format shown in the figure below - taken from [RFC 1035]: - - 1 1 1 1 1 1 - 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | | - / / - / NAME / - | | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | TYPE | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | CLASS | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | TTL | - | | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - | RDLENGTH | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--| - / RDATA / - / / - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ - - NAME is an owner name, i.e., the name of the node to which this - resource record pertains. NAMEs are specific to a CLASS as described - in section 3.2. NAMEs consist of an ordered sequence of one or more - labels each of which has a label type [RFC 1035, 2671]. - - TYPE is a two octet unsigned integer containing one of the RR TYPE - codes. See section 3.1. - - CLASS is a two octet unsigned integer containing one of the RR CLASS - codes. See section 3.2. - - TTL is a four octet (32 bit) bit unsigned integer that specifies the - number of seconds that the resource record may be cached before the - source of the information should again be consulted. Zero is - interpreted to mean that the RR can only be used for the transaction - in progress. - - RDLENGTH is an unsigned 16 bit integer that specifies the length in - - -D. Eastlake 3rd [Page 6] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - octets of the RDATA field. - - RDATA is a variable length string of octets that constitutes the - resource. The format of this information varies according to the TYPE - and in some cases the CLASS of the resource record. - - - -3.1 RR TYPE IANA Considerations - - There are three subcategories of RR TYPE numbers: data TYPEs, QTYPEs, - and MetaTYPEs. - - Data TYPEs are the primary means of storing data. QTYPES can only be - used in queries. Meta-TYPEs designate transient data associated with - an particular DNS message and in some cases can also be used in - queries. Thus far, data TYPEs have been assigned from 1 upwards plus - the block from 100 through 103 while Q and Meta Types have been - assigned from 255 downwards except for the OPT Meta-RR which is - assigned TYPE 41. There have been DNS implementations which made - caching decisions based on the top bit of the bottom byte of the RR - TYPE. - - There are currently three Meta-TYPEs assigned: OPT [RFC 2671], TSIG - [RFC 2845], and TKEY [RFC 2930]. - - There are currently five QTYPEs assigned: * (all), MAILA, MAILB, - AXFR, and IXFR. - - Considerations for the allocation of new RR TYPEs are as follows: - - Decimal - Hexadecimal - - 0 - 0x0000 - TYPE zero is used as a special indicator for the SIG RR [RFC - 2535] and in other circumstances and must never be allocated - for ordinary use. - - 1 - 127 - 0x0001 - 0x007F - remaining TYPEs in this range are assigned for data - TYPEs by the DNS TYPE Allocation Policy as specified in - section 3.1.1. - - 128 - 255 - 0x0080 - 0x00FF - remaining TYPEs in this rage are assigned for Q and - Meta TYPEs by the DNS TYPE Allocation Policy as specified in - section 3.1.1. - - - - -D. Eastlake 3rd [Page 7] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - 256 - 32,767 - 0x0100 - 0x7FFF - assigned for data, Q, or Meta TYPE use by the DNS - TYPE Allocation Policy as specified in section 3.1.1. - - 32,768 - 65,279 - 0x8000 - 0xFEFF - Specification Required as defined in [RFC 2434]. - - 65,280 - 65534 - 0xFF00 - 0xFFFE - Private Use. - - 65,535 - 0xFFFF - Reserved, can only be assigned by an IETF Standards Action. - - - -3.1.1 DNS TYPE Allocation Policy - - Parameter values specified above as assigned based on DNS TYPE - Allocation Policy. That is, Expert Review with the additional - requirement that the review be based on a complete template as - specified below which has been posted for three weeks to the - namedroppers@ops.ietf.org mailing list. - - Partial or draft templates may be posted with the intend of - soliciting feedback. - - - DNS RR TYPE PARAMETER ALLOCATION TEMPLATE - - Date: - - Name and email of originator: - - Pointer to internet-draft or other document giving a detailed - description of the protocol use of the new RR Type: - - What need is the new RR TYPE intended to fix? - - What existing RR TYPE(s) come closest to filling that need and why are - they unsatisfactory? - - Does the proposed RR TYPR require special handling within the DNS - different from an Unknown RR TYPE? - - Comments: - - - - - - - -D. Eastlake 3rd [Page 8] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -3.1.2 Special Note on the OPT RR - - The OPT (OPTion) RR, number 41, is specified in [RFC 2671]. Its - primary purpose is to extend the effective field size of various DNS - fields including RCODE, label type, OpCode, flag bits, and RDATA - size. In particular, for resolvers and servers that recognize it, it - extends the RCODE field from 4 to 12 bits. - - - -3.1.3 The AFSDB RR Subtype Field - - The AFSDB RR [RFC 1183] is a CLASS insensitive RR that has the same - RDATA field structure as the MX RR but the 16 bit unsigned integer - field at the beginning of the RDATA is interpreted as a subtype as - follows: - - Decimal - Hexadecimal - - 0 - 0x0000 - Allocation requires IETF Standards Action. - - 1 - 0x0001 - Andrews File Service v3.0 Location Service [RFC 1183]. - - 2 - 0x0002 - DCE/NCA root cell directory node [RFC 1183]. - - 3 - 65,279 - 0x0003 - 0xFEFF - Allocation by IETF Consensus. - - 65,280 - 65,534 - 0xFF00 - 0xFFFE - Private Use. - - 65,535 - 0xFFFF - Reserved, allocation requires IETF Standards Action. - - - -3.2 RR CLASS IANA Considerations - - DNS CLASSes have been little used but constitute another dimension of - the DNS distributed database. In particular, there is no necessary - relationship between the name space or root servers for one CLASS and - those for another CLASS. The same name can have completely different - meanings in different CLASSes; however, the label types are the same - and the null label is usable only as root in every CLASS. However, - as global networking and DNS have evolved, the IN, or Internet, CLASS - has dominated DNS use. - - -D. Eastlake 3rd [Page 9] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - There are two subcategories of DNS CLASSes: normal data containing - classes and QCLASSes that are only meaningful in queries or updates. - - The current CLASS assignments and considerations for future - assignments are as follows: - - Decimal - Hexadecimal - - 0 - 0x0000 - Reserved, assignment requires an IETF Standards Action. - - 1 - 0x0001 - Internet (IN). - - 2 - 0x0002 - Available for assignment by IETF Consensus as a data CLASS. - - 3 - 0x0003 - Chaos (CH) [Moon 1981]. - - 4 - 0x0004 - Hesiod (HS) [Dyer 1987]. - - 5 - 127 - 0x0005 - 0x007F - available for assignment by IETF Consensus for data - CLASSes only. - - 128 - 253 - 0x0080 - 0x00FD - available for assignment by IETF Consensus for - QCLASSes only. - - 254 - 0x00FE - QCLASS None [RFC 2136]. - - 255 - 0x00FF - QCLASS Any [RFC 1035]. - - 256 - 32,767 - 0x0100 - 0x7FFF - Assigned by IETF Consensus. - - 32,768 - 65,279 - 0x8000 - 0xFEFF - Assigned based on Specification Required as defined - in [RFC 2434]. - - 65,280 - 65,534 - 0xFF00 - 0xFFFE - Private Use. - - 65,535 - 0xFFFF - Reserved, can only be assigned by an IETF Standards Action. - - -D. Eastlake 3rd [Page 10] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -3.3 RR NAME Considerations - - DNS NAMEs are sequences of labels [RFC 1035]. The last label in each - NAME is "ROOT" which is the zero length label. By definition, the - null or ROOT label can not be used for any other NAME purpose. - - At the present time, there are two categories of label types, data - labels and compression labels. Compression labels are pointers to - data labels elsewhere within an RR or DNS message and are intended to - shorten the wire encoding of NAMEs. The two existing data label - types are sometimes referred to as Text and Binary. Text labels can, - in fact, include any octet value including zero value octets but most - current uses involve only [US-ASCII]. For retrieval, Text labels are - defined to treat ASCII upper and lower case letter codes as matching - [insensitive]. Binary labels are bit sequences [RFC 2673]. The - Binary label type is Experimental [RFC 3363]. - - IANA considerations for label types are given in [RFC 2671]. - - NAMEs are local to a CLASS. The Hesiod [Dyer 1987] and Chaos [Moon - 1981] CLASSes are essentially for local use. The IN or Internet - CLASS is thus the only DNS CLASS in global use on the Internet at - this time. - - A somewhat out-of-date description of name allocation in the IN Class - is given in [RFC 1591]. Some information on reserved top level - domain names is in BCP 32 [RFC 2606]. - - - -4. Security Considerations - - This document addresses IANA considerations in the allocation of - general DNS parameters, not security. See [RFC 4033, 4034, 4035] for - secure DNS considerations. - - - - - - - - - - - - - - - - - -D. Eastlake 3rd [Page 11] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -Appendix: Changes from RFC 2929 - - RFC Editor: This Appendix should be deleted for publication. - - Changes from RFC 2929 to this draft: - - 1. Changed many "IETF Consensus" for RR TYPEs to be "DNS TYPE - Allocation Policy" and add the specification of that policy. Change - some remaining "IETF Standards Action" allocation requirements to say - "as modified by [RFC 4020]". - - 2. Updated various RFC references. - - 3. Mentioned that the Binary label type is now Experimental and - IQuery is Obsolete. - - 4. Changed allocation status of RR Type 0xFFFF and RCODE 0xFFFF to be - IETF Standards Action required. - - 5. Add an IANA allocation policy for the AFSDB RR Subtype field. - - 6. Addition of reference to case insensitive draft. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -D. Eastlake 3rd [Page 12] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -Copyright and Disclaimer - - Copyright (C) The Internet Society (2005). This document is subject to - the rights, licenses and restrictions contained in BCP 78, and except - as set forth therein, the authors retain all their rights. - - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - - -Normative References - - [RFC 1034] - Mockapetris, P., "Domain Names - Concepts and - Facilities", STD 13, RFC 1034, November 1987. - - [RFC 1035] - Mockapetris, P., "Domain Names - Implementation and - Specifications", STD 13, RFC 1035, November 1987. - - [RFC 1183] - Everhart, C., Mamakos, L., Ullmann, R., and P. - Mockapetris, "New DNS RR Definitions", RFC 1183, October 1990. - - [RFC 1996] - Vixie, P., "A Mechanism for Prompt Notification of Zone - Changes (DNS NOTIFY)", RFC 1996, August 1996. - - [RFC 2136] - Vixie, P., Thomson, S., Rekhter, Y. and J. Bound, - "Dynamic Updates in the Domain Name System (DNS UPDATE)", RFC 2136, - April 1997. - - [RFC 2181] - Elz, R. and R. Bush, "Clarifications to the DNS - Specification", RFC 2181, July 1997. - - [RFC 2434] - Narten, T. and H. Alvestrand, "Guidelines for Writing an - IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. - - [RFC 2671] - Vixie, P., "Extension mechanisms for DNS (EDNS0)", RFC - 2671, August 1999. - - [RFC 2673] - Crawford, M., "Binary Labels in the Domain Name System", - RFC 2673, August 1999. - - [RFC 2845] - Vixie, P., Gudmundsson, O., Eastlake, D. and B. - Wellington, "Secret Key Transaction Authentication for DNS (TSIG)", - RFC 2845, May 2000. - - -D. Eastlake 3rd [Page 13] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - [RFC 2930] - Eastlake, D., "Secret Key Establishment for DNS (TKEY - RR)", September 2000. - - [RFC 3363] - Bush, R., Durand, A., Fink, B., Gudmundsson, O., and T. - Hain, "Representing Internet Protocol version 6 (IPv6) Addresses in - the Domain Name System (DNS)", RFC 3363, August 2002. - - [RFC 3425] - Lawrence, D., "Obsoleting IQUERY", RFC 3425, November - 2002. - - [RFC 4020] - Kompella, K. and A. Zinin, "Early IANA Allocation of - Standards Track Code Points", BCP 100, RFC 4020, February 2005. - - [RFC 4033] - Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "DNS Security Introduction and Requirements", RFC 4033, March - 2005. - - [RFC 4034] - Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Resource Records for the DNS Security Extensions", RFC 4034, - March 2005. - - [RFC 4044] - Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Protocol Modifications for the DNS Security Extensions", RFC - 4035, March 2005. - - [US-ASCII] - ANSI, "USA Standard Code for Information Interchange", - X3.4, American National Standards Institute: New York, 1968. - - - -Informative References - - [Dyer 1987] - Dyer, S., and F. Hsu, "Hesiod", Project Athena - Technical Plan - Name Service, April 1987, - - [Moon 1981] - D. Moon, "Chaosnet", A.I. Memo 628, Massachusetts - Institute of Technology Artificial Intelligence Laboratory, June - 1981. - - [RFC 1591] - Postel, J., "Domain Name System Structure and - Delegation", RFC 1591, March 1994. - - [RFC 2929] - Eastlake 3rd, D., Brunner-Williams, E., and B. Manning, - "Domain Name System (DNS) IANA Considerations", BCP 42, RFC 2929, - September 2000. - - [RFC 2606] - Eastlake, D. and A. Panitz, "Reserved Top Level DNS - Names", RFC 2606, June 1999. - - [insensitive] - Eastlake, D., "Domain Name System (DNS) Case - - -D. Eastlake 3rd [Page 14] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - - Insensitivity Clarification", draft-ietf-dnsext-insensitive-*.txt, - work in progress. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -D. Eastlake 3rd [Page 15] - - -INTERNET-DRAFT DNS IANA Considerations August 2005 - - -Authors Addresses - - Donald E. Eastlake 3rd - Motorola Laboratories - 155 Beaver Street - Milford, MA 01757 USA - - Telephone: +1-508-786-7554 (w) - email: Donald.Eastlake@motorola.com - - - -Expiration and File Name - - This draft expires February 2006. - - Its file name is draft-ietf-dnsext-2929bis-01.txt. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -D. Eastlake 3rd [Page 16] - diff --git a/doc/draft/draft-ietf-dnsext-dnssec-2535typecode-change-06.txt b/doc/draft/draft-ietf-dnsext-dnssec-2535typecode-change-06.txt deleted file mode 100644 index bcc2b4ec51..0000000000 --- a/doc/draft/draft-ietf-dnsext-dnssec-2535typecode-change-06.txt +++ /dev/null @@ -1,442 +0,0 @@ - - -INTERNET-DRAFT Samuel Weiler -Expires: June 2004 December 15, 2003 -Updates: RFC 2535, [DS] - - Legacy Resolver Compatibility for Delegation Signer - draft-ietf-dnsext-dnssec-2535typecode-change-06.txt - -Status of this Memo - - This document is an Internet-Draft and is subject to all provisions - of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as - Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six - months and may be updated, replaced, or obsoleted by other - documents at any time. It is inappropriate to use Internet-Drafts - as reference material or to cite them other than as "work in - progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/1id-abstracts.html - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html - - Comments should be sent to the author or to the DNSEXT WG mailing - list: namedroppers@ops.ietf.org - -Abstract - - As the DNS Security (DNSSEC) specifications have evolved, the - syntax and semantics of the DNSSEC resource records (RRs) have - changed. Many deployed nameservers understand variants of these - semantics. Dangerous interactions can occur when a resolver that - understands an earlier version of these semantics queries an - authoritative server that understands the new delegation signer - semantics, including at least one failure scenario that will cause - an unsecured zone to be unresolvable. This document changes the - type codes and mnemonics of the DNSSEC RRs (SIG, KEY, and NXT) to - avoid those interactions. - -Changes between 05 and 06: - - Signifigantly reworked the IANA section -- went back to one - algorithm registry. - - Removed Diffie-Hellman from the list of zone-signing algorithms - (leaving only DSA, RSA/SHA-1, and private algorithms). - - Added a DNSKEY flags field registry. - -Changes between 04 and 05: - - IESG approved publication. - - Cleaned up an internal reference in the acknowledgements section. - - Retained KEY and SIG for TKEY, too. Added TKEY (2930) reference. - - Changed the names of both new registries. Added algorithm - mnemonics to the new zone signing algorithm registry. Minor - rewording in the IANA section for clarity. - - Cleaned up formatting of references. Replaced unknown-rr draft - references with RFC3597. Bumped DS version number. - -Changes between 03 and 04: - - Clarified that RRSIG(0) may be defined by standards action. - - Created a new algorithm registry and renamed the old algorithm - registry for SIG(0) only. Added references to the appropriate - crypto algorithm and format specifications. - - Several minor rephrasings. - -Changes between 02 and 03: - - KEY (as well as SIG) retained for SIG(0) use only. - -Changes between 01 and 02: - - SIG(0) still uses SIG, not RRSIG. Added 2931 reference. - - Domain names embedded in NSECs and RRSIGs are not compressible and - are not downcased. Added unknown-rrs reference (as informative). - - Simplified the last paragraph of section 3 (NSEC doesn't always - signal a negative answer). - - Changed the suggested type code assignments. - - Added 2119 reference. - - Added definitions of "unsecure delegation" and "unsecure referral", - since they're not clearly defined elsewhere. - - Moved 2065 to informative references, not normative. - -1. Introduction - - The DNSSEC protocol has been through many iterations whose syntax - and semantics are not completely compatible. This has occurred as - part of the ordinary process of proposing a protocol, implementing - it, testing it in the increasingly complex and diverse environment - of the Internet, and refining the definitions of the initial - Proposed Standard. In the case of DNSSEC, the process has been - complicated by DNS's criticality and wide deployment and the need - to add security while minimizing daily operational complexity. - - A weak area for previous DNS specifications has been lack of detail - in specifying resolver behavior, leaving implementors largely on - their own to determine many details of resolver function. This, - combined with the number of iterations the DNSSEC spec has been - through, has resulted in fielded code with a wide variety of - behaviors. This variety makes it difficult to predict how a - protocol change will be handled by all deployed resolvers. The - risk that a change will cause unacceptable or even catastrophic - failures makes it difficult to design and deploy a protocol change. - One strategy for managing that risk is to structure protocol - changes so that existing resolvers can completely ignore input that - might confuse them or trigger undesirable failure modes. - - This document addresses a specific problem caused by Delegation - Signer's [DS] introduction of new semantics for the NXT RR that are - incompatible with the semantics in RFC 2535 [RFC2535]. Answers - provided by DS-aware servers can trigger an unacceptable failure - mode in some resolvers that implement RFC 2535, which provides a - great disincentive to sign zones with DS. The changes defined in - this document allow for the incremental deployment of DS. - -1.1 Terminology - - In this document, the term "unsecure delegation" means any - delegation for which no DS record appears at the parent. An - "unsecure referral" is an answer from the parent containing an NS - RRset and a proof that no DS record exists for that name. - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in [RFC2119]. - -1.2 The Problem - - Delegation Signer introduces new semantics for the NXT RR that are - incompatible with the semantics in RFC 2535. In RFC 2535, NXT - records were only required to be returned as part of a - non-existence proof. With DS, an unsecure referral returns, in - addition to the NS, a proof of non-existence of a DS RR in the form - of an NXT and SIG(NXT). RFC 2535 didn't specify how a resolver was - to interpret a response with both an NS and an NXT in the authority - section, RCODE=0, and AA=0. Some widely deployed 2535-aware - resolvers interpret any answer with an NXT as a proof of - non-existence of the requested record. This results in unsecure - delegations being invisible to 2535-aware resolvers and violates - the basic architectural principle that DNSSEC must do no harm -- - the signing of zones must not prevent the resolution of unsecured - delegations. - -2. Possible Solutions - - This section presents several solutions that were considered. - Section 3 describes the one selected. - -2.1. Change SIG, KEY, and NXT type codes - - To avoid the problem described above, legacy (RFC2535-aware) - resolvers need to be kept from seeing unsecure referrals that - include NXT records in the authority section. The simplest way to - do that is to change the type codes for SIG, KEY, and NXT. - - The obvious drawback to this is that new resolvers will not be able - to validate zones signed with the old RRs. This problem already - exists, however, because of the changes made by DS, and resolvers - that understand the old RRs (and have compatibility issues with DS) - are far more prevalent than 2535-signed zones. - -2.2. Change a subset of type codes - - The observed problem with unsecure referrals could be addressed by - changing only the NXT type code or another subset of the type codes - that includes NXT. This has the virtue of apparent simplicity, but - it risks introducing new problems or not going far enough. It's - quite possible that more incompatibilities exist between DS and - earlier semantics. Legacy resolvers may also be confused by seeing - records they recognize (SIG and KEY) while being unable to find - NXTs. Although it may seem unnecessary to fix that which is not - obviously broken, it's far cleaner to change all of the type codes - at once. This will leave legacy resolvers and tools completely - blinded to DNSSEC -- they will see only unknown RRs. - -2.3. Replace the DO bit - - Another way to keep legacy resolvers from ever seeing DNSSEC - records with DS semantics is to have authoritative servers only - send that data to DS-aware resolvers. It's been proposed that - assigning a new EDNS0 flag bit to signal DS-awareness (tentatively - called "DA"), and having authoritative servers send DNSSEC data - only in response to queries with the DA bit set, would accomplish - this. This bit would presumably supplant the DO bit described in - RFC 3225. - - This solution is sufficient only if all 2535-aware resolvers zero - out EDNS0 flags that they don't understand. If one passed through - the DA bit unchanged, it would still see the new semantics, and it - would probably fail to see unsecure delegations. Since it's - impractical to know how every DNS implementation handles unknown - EDNS0 flags, this is not a universal solution. It could, though, - be considered in addition to changing the RR type codes. - -2.4. Increment the EDNS version - - Another possible solution is to increment the EDNS version number - as defined in RFC 2671 [RFC2671], on the assumption that all - existing implementations will reject higher versions than they - support, and retain the DO bit as the signal for DNSSEC awareness. - This approach has not been tested. - -2.5. Do nothing - - There is a large deployed base of DNS resolvers that understand - DNSSEC as defined by the standards track RFC 2535 and RFC 2065 - and, due to under specification in those documents, interpret any - answer with an NXT as a non-existence proof. So long as that is - the case, zone owners will have a strong incentive to not sign any - zones that contain unsecure delegations, lest those delegations be - invisible to such a large installed base. This will dramatically - slow DNSSEC adoption. - - Unfortunately, without signed zones there's no clear incentive for - operators of resolvers to upgrade their software to support the new - version of DNSSEC, as defined in [DS]. Historical data suggests - that resolvers are rarely upgraded, and that old nameserver code - never dies. - - Rather than wait years for resolvers to be upgraded through natural - processes before signing zones with unsecure delegations, - addressing this problem with a protocol change will immediately - remove the disincentive for signing zones and allow widespread - deployment of DNSSEC. - -3. Protocol changes - - This document changes the type codes of SIG, KEY, and NXT. This - approach is the cleanest and safest of those discussed above, - largely because the behavior of resolvers that receive unknown type - codes is well understood. This approach has also received the most - testing. - - To avoid operational confusion, it's also necessary to change the - mnemonics for these RRs. DNSKEY will be the replacement for KEY, - with the mnemonic indicating that these keys are not for - application use, per [RFC3445]. RRSIG (Resource Record SIGnature) - will replace SIG, and NSEC (Next SECure) will replace NXT. These - new types completely replace the old types, except that SIG(0) - [RFC2931] and TKEY [RFC2930] will continue to use SIG and KEY. - - The new types will have exactly the same syntax and semantics as - specified for SIG, KEY, and NXT in RFC 2535 and [DS] except for - the following: - - 1) Consistent with [RFC3597], domain names embedded in - RRSIG and NSEC RRs MUST NOT be compressed, - - 2) Embedded domain names in RRSIG and NSEC RRs are not downcased - for purposes of DNSSEC canonical form and ordering nor for - equality comparison, and - - 3) An RRSIG with a type-covered field of zero has undefined - semantics. The meaning of such a resource record may only be - defined by IETF Standards Action. - - If a resolver receives the old types, it SHOULD treat them as - unknown RRs and SHOULD NOT assign any special meaning to them or - give them any special treatment. It MUST NOT use them for DNSSEC - validations or other DNS operational decision making. For example, - a resolver MUST NOT use DNSKEYs to validate SIGs or use KEYs to - validate RRSIGs. If SIG, KEY, or NXT RRs are included in a zone, - they MUST NOT receive special treatment. As an example, if a SIG - is included in a signed zone, there MUST be an RRSIG for it. - Authoritative servers may wish to give error messages when loading - zones containing SIG or NXT records (KEY records may be included - for SIG(0) or TKEY). - - As a clarification to previous documents, some positive responses, - particularly wildcard proofs and unsecure referrals, will contain - NSEC RRs. Resolvers MUST NOT treat answers with NSEC RRs as - negative answers merely because they contain an NSEC. - -4. IANA Considerations - -4.1 DNS Resource Record Types - - This document updates the IANA registry for DNS Resource Record - Types by assigning types 46, 47, and 48 to the RRSIG, NSEC, and - DNSKEY RRs, respectively. - - Types 24 and 25 (SIG and KEY) are retained for SIG(0) [RFC2931] and - TKEY [RFC2930] use only. - - Type 30 (NXT) should be marked as Obsolete. - -4.2 DNS Security Algorithm Numbers - - To allow zone signing (DNSSEC) and transaction security mechanisms - (SIG(0) and TKEY) to use different sets of algorithms, the existing - "DNS Security Algorithm Numbers" registry is modified to include - the applicability of each algorithm. Specifically, two new columns - are added to the registry, showing whether each algorithm may be - used for zone signing, transaction security mechanisms, or both. - Only algorithms usable for zone signing may be used in DNSKEY, - RRSIG, and DS RRs. Only algorithms usable for SIG(0) and/or TSIG - may be used in SIG and KEY RRs. - - All currently defined algorithms remain usable for transaction - security mechanisms. Only RSA/SHA-1, DSA/SHA-1, and private - algorithms (types 253 and 254) may be used for zone signing. Note - that the registry does not contain the requirement level of each - algorithm, only whether or not an algorithm may be used for the - given purposes. For example, RSA/MD5, while allowed for - transaction security mechanisms, is NOT RECOMMENDED, per RFC3110. - - Additionally, the presentation format algorithm mnemonics from - RFC2535 Section 7 are added to the registry. This document assigns - RSA/SHA-1 the mnemonic RSASHA1. - - As before, assignment of new algorithms in this registry requires - IETF Standards Action. Additionally, modification of algorithm - mnemonics or applicability requires IETF Standards Action. - Documents defining a new algorithm must address the applicability - of the algorithm and should assign a presentation mnemonic to the - algorithm. - -4.3 DNSKEY Flags - - Like the KEY resource record, DNSKEY contains a 16-bit flags field. - This document creates a new registry for the DNSKEY flags field. - - Initially, this registry only contains an assignment for bit 7 (the - ZONE bit). Bits 0-6 and 8-15 are available for assignment by IETF - Standards Action. - -4.4 DNSKEY Protocol Octet - - Like the KEY resource record, DNSKEY contains an eight bit protocol - field. The only defined value for this field is 3 (DNSSEC). No - other values are allowed, hence no IANA registry is needed for this - field. - -5. Security Considerations - - The changes introduced here do not materially affect security. - The implications of trying to use both new and legacy types - together are not well understood, and attempts to do so would - probably lead to unintended and dangerous results. - - Changing type codes will leave code paths in legacy resolvers that - are never exercised. Unexercised code paths are a frequent source - of security holes, largely because those code paths do not get - frequent scrutiny. - - Doing nothing, as described in section 2.5, will slow DNSSEC - deployment. While this does not decrease security, it also fails - to increase it. - -6. Normative references - - [RFC2535] Eastlake, D., "Domain Name System Security Extensions", - RFC 2535, March 1999. - - [DS] Gudmundsson, O., "Delegation Signer Resource Record", - draft-ietf-dnsext-delegation-signer-15.txt, work in - progress, June 2003. - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - - [RFC2931] Eastlake, D., "DNS Request and Transaction Signatures - (SIG(0)s)", RFC 2931, September 2000. - - [RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY - RR)", RFC 2930, September 2000. - - [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the Domain Name - System (DNS)", RFC 2436, March 1999. - - [RFC2539] Eastlake, D., "Storage of Diffie-Hellman Keys in the - Domain Name System (DNS)", RFC 2539, March 1999. - - [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the - Domain Name System (DNS)", RFC 3110, May 2001. - -7. Informative References - - [RFC2065] Eastlake, D. and C. Kaufman, "Domain Name System Security - Extensions", RFC 2065, January 1997. - - [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC - 2671, August 1999. - - [RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC", RFC - 3225, December 2001. - - [RFC2929] Eastlake, D., E. Brunner-Williams, and B. Manning, - "Domain Name System (DNS) IANA Considerations", BCP 42, - RFC 2929, September 2000. - - [RFC3445] Massey, D., and S. Rose, "Limiting the Scope of the KEY - Resource Record (RR)", RFC 3445, December 2002. - - [RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource - Record (RR) Types", RFC 3597, September 2003. - -8. Acknowledgments - - The changes introduced here and the analysis of alternatives had - many contributors. With apologies to anyone overlooked, those - include: Micheal Graff, John Ihren, Olaf Kolkman, Mark Kosters, Ed - Lewis, Bill Manning, and Suzanne Woolf. - - Thanks to Jakob Schlyter and Mark Andrews for identifying the - incompatibility described in section 1.2. - - In addition to the above, the author would like to thank Scott - Rose, Olafur Gudmundsson, and Sandra Murphy for their substantive - comments. - -9. Author's Address - - Samuel Weiler - SPARTA, Inc. - 7075 Samuel Morse Drive - Columbia, MD 21046 - USA - weiler@tislabs.com - diff --git a/doc/draft/draft-ietf-dnsext-dnssec-online-signing-02.txt b/doc/draft/draft-ietf-dnsext-dnssec-online-signing-02.txt deleted file mode 100644 index 7503c66ab3..0000000000 --- a/doc/draft/draft-ietf-dnsext-dnssec-online-signing-02.txt +++ /dev/null @@ -1,616 +0,0 @@ - - - -Network Working Group S. Weiler -Internet-Draft SPARTA, Inc -Updates: 4034, 4035 (if approved) J. Ihren -Expires: July 24, 2006 Autonomica AB - January 20, 2006 - - - Minimally Covering NSEC Records and DNSSEC On-line Signing - draft-ietf-dnsext-dnssec-online-signing-02 - -Status of this Memo - - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on July 24, 2006. - -Copyright Notice - - Copyright (C) The Internet Society (2006). - -Abstract - - This document describes how to construct DNSSEC NSEC resource records - that cover a smaller range of names than called for by RFC4034. By - generating and signing these records on demand, authoritative name - servers can effectively stop the disclosure of zone contents - otherwise made possible by walking the chain of NSEC records in a - signed zone. - - - - -Weiler & Ihren Expires July 24, 2006 [Page 1] - -Internet-Draft NSEC Epsilon January 2006 - - -Changes from ietf-01 to ietf-02 - - Clarified that a generated NSEC RR's type bitmap MUST have the RRSIG - and NSEC bits set, to be consistent with DNSSECbis -- previous text - said SHOULD. - - Made the applicability statement a little less oppressive. - -Changes from ietf-00 to ietf-01 - - Added an applicability statement, making reference to ongoing work on - NSEC3. - - Added the phrase "epsilon functions", which has been commonly used to - describe the technique and already appeared in the header of each - page, in place of "increment and decrement functions". Also added an - explanatory sentence. - - Corrected references from 4034 section 6.2 to section 6.1. - - Fixed an out-of-date reference to [-bis] and other typos. - - Replaced IANA Considerations text. - - Escaped close parentheses in examples. - - Added some more acknowledgements. - -Changes from weiler-01 to ietf-00 - - Inserted RFC numbers for 4033, 4034, and 4035. - - Specified contents of bitmap field in synthesized NSEC RR's, pointing - out that this relaxes a constraint in 4035. Added 4035 to the - Updates header. - -Changes from weiler-00 to weiler-01 - - Clarified that this updates RFC4034 by relaxing requirements on the - next name field. - - Added examples covering wildcard names. - - In the 'better functions' section, reiterated that perfect functions - aren't needed. - - Added a reference to RFC 2119. - - - - -Weiler & Ihren Expires July 24, 2006 [Page 2] - -Internet-Draft NSEC Epsilon January 2006 - - -Table of Contents - - 1. Introduction and Terminology . . . . . . . . . . . . . . . . . 4 - 2. Applicability of This Technique . . . . . . . . . . . . . . . 4 - 3. Minimally Covering NSEC Records . . . . . . . . . . . . . . . 5 - 4. Better Epsilon Functions . . . . . . . . . . . . . . . . . . . 6 - 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 - 7. Normative References . . . . . . . . . . . . . . . . . . . . . 8 - Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 8 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 - Intellectual Property and Copyright Statements . . . . . . . . . . 11 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Weiler & Ihren Expires July 24, 2006 [Page 3] - -Internet-Draft NSEC Epsilon January 2006 - - -1. Introduction and Terminology - - With DNSSEC [1], an NSEC record lists the next instantiated name in - its zone, proving that no names exist in the "span" between the - NSEC's owner name and the name in the "next name" field. In this - document, an NSEC record is said to "cover" the names between its - owner name and next name. - - Through repeated queries that return NSEC records, it is possible to - retrieve all of the names in the zone, a process commonly called - "walking" the zone. Some zone owners have policies forbidding zone - transfers by arbitrary clients; this side-effect of the NSEC - architecture subverts those policies. - - This document presents a way to prevent zone walking by constructing - NSEC records that cover fewer names. These records can make zone - walking take approximately as many queries as simply asking for all - possible names in a zone, making zone walking impractical. Some of - these records must be created and signed on demand, which requires - on-line private keys. Anyone contemplating use of this technique is - strongly encouraged to review the discussion of the risks of on-line - signing in Section 6. - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in RFC 2119 [4]. - - -2. Applicability of This Technique - - The technique presented here may be useful to a zone owner that wants - to use DNSSEC, is concerned about exposure of its zone contents via - zone walking, and is willing to bear the costs of on-line signing. - - As discussed in Section 6, on-line signing has several security - risks, including an increased likelihood of private keys being - disclosed and an increased risk of denial of service attack. Anyone - contemplating use of this technique is strongly encouraged to review - the discussion of the risks of on-line signing in Section 6. - - Furthermore, at the time this document was published, the DNSEXT - working group was actively working on a mechanism to prevent zone - walking that does not require on-line signing (tentatively called - NSEC3). The new mechanism is likely to expose slightly more - information about the zone than this technique (e.g. the number of - instantiated names), but it may be preferable to this technique. - - - - - -Weiler & Ihren Expires July 24, 2006 [Page 4] - -Internet-Draft NSEC Epsilon January 2006 - - -3. Minimally Covering NSEC Records - - This mechanism involves changes to NSEC records for instantiated - names, which can still be generated and signed in advance, as well as - the on-demand generation and signing of new NSEC records whenever a - name must be proven not to exist. - - In the 'next name' field of instantiated names' NSEC records, rather - than list the next instantiated name in the zone, list any name that - falls lexically after the NSEC's owner name and before the next - instantiated name in the zone, according to the ordering function in - RFC4034 [2] section 6.1. This relaxes the requirement in section - 4.1.1 of RFC4034 that the 'next name' field contains the next owner - name in the zone. This change is expected to be fully compatible - with all existing DNSSEC validators. These NSEC records are returned - whenever proving something specifically about the owner name (e.g. - that no resource records of a given type appear at that name). - - Whenever an NSEC record is needed to prove the non-existence of a - name, a new NSEC record is dynamically produced and signed. The new - NSEC record has an owner name lexically before the QNAME but - lexically following any existing name and a 'next name' lexically - following the QNAME but before any existing name. - - The generated NSEC record's type bitmap MUST have the RRSIG and NSEC - bits set and SHOULD NOT have any other bits set. This relaxes the - requirement in Section 2.3 of RFC4035 that NSEC RRs not appear at - names that did not exist before the zone was signed. - - The functions to generate the lexically following and proceeding - names need not be perfect nor consistent, but the generated NSEC - records must not cover any existing names. Furthermore, this - technique works best when the generated NSEC records cover as few - names as possible. In this document, the functions that generate the - nearby names are called 'epsilon' functions, a reference to the - mathematical convention of using the greek letter epsilon to - represent small deviations. - - An NSEC record denying the existence of a wildcard may be generated - in the same way. Since the NSEC record covering a non-existent - wildcard is likely to be used in response to many queries, - authoritative name servers using the techniques described here may - want to pregenerate or cache that record and its corresponding RRSIG. - - For example, a query for an A record at the non-instantiated name - example.com might produce the following two NSEC records, the first - denying the existence of the name example.com and the second denying - the existence of a wildcard: - - - -Weiler & Ihren Expires July 24, 2006 [Page 5] - -Internet-Draft NSEC Epsilon January 2006 - - - exampld.com 3600 IN NSEC example-.com ( RRSIG NSEC ) - - \).com 3600 IN NSEC +.com ( RRSIG NSEC ) - - Before answering a query with these records, an authoritative server - must test for the existence of names between these endpoints. If the - generated NSEC would cover existing names (e.g. exampldd.com or - *bizarre.example.com), a better epsilon function may be used or the - covered name closest to the QNAME could be used as the NSEC owner - name or next name, as appropriate. If an existing name is used as - the NSEC owner name, that name's real NSEC record MUST be returned. - Using the same example, assuming an exampldd.com delegation exists, - this record might be returned from the parent: - - exampldd.com 3600 IN NSEC example-.com ( NS DS RRSIG NSEC ) - - Like every authoritative record in the zone, each generated NSEC - record MUST have corresponding RRSIGs generated using each algorithm - (but not necessarily each DNSKEY) in the zone's DNSKEY RRset, as - described in RFC4035 [3] section 2.2. To minimize the number of - signatures that must be generated, a zone may wish to limit the - number of algorithms in its DNSKEY RRset. - - -4. Better Epsilon Functions - - Section 6.1 of RFC4034 defines a strict ordering of DNS names. - Working backwards from that definition, it should be possible to - define epsilon functions that generate the immediately following and - preceding names, respectively. This document does not define such - functions. Instead, this section presents functions that come - reasonably close to the perfect ones. As described above, an - authoritative server should still ensure than no generated NSEC - covers any existing name. - - To increment a name, add a leading label with a single null (zero- - value) octet. - - To decrement a name, decrement the last character of the leftmost - label, then fill that label to a length of 63 octets with octets of - value 255. To decrement a null (zero-value) octet, remove the octet - -- if an empty label is left, remove the label. Defining this - function numerically: fill the left-most label to its maximum length - with zeros (numeric, not ASCII zeros) and subtract one. - - In response to a query for the non-existent name foo.example.com, - these functions produce NSEC records of: - - - - -Weiler & Ihren Expires July 24, 2006 [Page 6] - -Internet-Draft NSEC Epsilon January 2006 - - - fon\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255.example.com 3600 IN NSEC \000.foo.example.com ( NSEC RRSIG ) - - \)\255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255\255\255\255\255\255\255\255\255\255\255\255\255\255 - \255\255.example.com 3600 IN NSEC \000.*.example.com ( NSEC RRSIG ) - - The first of these NSEC RRs proves that no exact match for - foo.example.com exists, and the second proves that there is no - wildcard in example.com. - - Both of these functions are imperfect: they don't take into account - constraints on number of labels in a name nor total length of a name. - As noted in the previous section, though, this technique does not - depend on the use of perfect epsilon functions: it is sufficient to - test whether any instantiated names fall into the span covered by the - generated NSEC and, if so, substitute those instantiated owner names - for the NSEC owner name or next name, as appropriate. - - -5. IANA Considerations - - This document specifies no IANA Actions. - - -6. Security Considerations - - This approach requires on-demand generation of RRSIG records. This - creates several new vulnerabilities. - - First, on-demand signing requires that a zone's authoritative servers - have access to its private keys. Storing private keys on well-known - internet-accessible servers may make them more vulnerable to - unintended disclosure. - - Second, since generation of digital signatures tends to be - computationally demanding, the requirement for on-demand signing - makes authoritative servers vulnerable to a denial of service attack. - - Lastly, if the epsilon functions are predictable, on-demand signing - may enable a chosen-plaintext attack on a zone's private keys. Zones - using this approach should attempt to use cryptographic algorithms - that are resistant to chosen-plaintext attacks. It's worth noting - - - -Weiler & Ihren Expires July 24, 2006 [Page 7] - -Internet-Draft NSEC Epsilon January 2006 - - - that while DNSSEC has a "mandatory to implement" algorithm, that is a - requirement on resolvers and validators -- there is no requirement - that a zone be signed with any given algorithm. - - The success of using minimally covering NSEC record to prevent zone - walking depends greatly on the quality of the epsilon functions - chosen. An increment function that chooses a name obviously derived - from the next instantiated name may be easily reverse engineered, - destroying the value of this technique. An increment function that - always returns a name close to the next instantiated name is likewise - a poor choice. Good choices of epsilon functions are the ones that - produce the immediately following and preceding names, respectively, - though zone administrators may wish to use less perfect functions - that return more human-friendly names than the functions described in - Section 4 above. - - Another obvious but misguided concern is the danger from synthesized - NSEC records being replayed. It's possible for an attacker to replay - an old but still validly signed NSEC record after a new name has been - added in the span covered by that NSEC, incorrectly proving that - there is no record at that name. This danger exists with DNSSEC as - defined in [3]. The techniques described here actually decrease the - danger, since the span covered by any NSEC record is smaller than - before. Choosing better epsilon functions will further reduce this - danger. - -7. Normative References - - [1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, - "DNS Security Introduction and Requirements", RFC 4033, - March 2005. - - [2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, - "Resource Records for the DNS Security Extensions", RFC 4034, - March 2005. - - [3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, - "Protocol Modifications for the DNS Security Extensions", - RFC 4035, March 2005. - - [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement - Levels", BCP 14, RFC 2119, March 1997. - - -Appendix A. Acknowledgments - - Many individuals contributed to this design. They include, in - addition to the authors of this document, Olaf Kolkman, Ed Lewis, - - - -Weiler & Ihren Expires July 24, 2006 [Page 8] - -Internet-Draft NSEC Epsilon January 2006 - - - Peter Koch, Matt Larson, David Blacka, Suzanne Woolf, Jaap Akkerhuis, - Jakob Schlyter, Bill Manning, and Joao Damas. - - In addition, the editors would like to thank Ed Lewis, Scott Rose, - and David Blacka for their careful review of the document. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Weiler & Ihren Expires July 24, 2006 [Page 9] - -Internet-Draft NSEC Epsilon January 2006 - - -Authors' Addresses - - Samuel Weiler - SPARTA, Inc - 7075 Samuel Morse Drive - Columbia, Maryland 21046 - US - - Email: weiler@tislabs.com - - - Johan Ihren - Autonomica AB - Bellmansgatan 30 - Stockholm SE-118 47 - Sweden - - Email: johani@autonomica.se - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Weiler & Ihren Expires July 24, 2006 [Page 10] - -Internet-Draft NSEC Epsilon January 2006 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - Intellectual Property Rights or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; nor does it represent that it has - made any independent effort to identify any such rights. Information - on the procedures with respect to rights in RFC documents can be - found in BCP 78 and BCP 79. - - Copies of IPR disclosures made to the IETF Secretariat and any - assurances of licenses to be made available, or the result of an - attempt made to obtain a general license or permission for the use of - such proprietary rights by implementers or users of this - specification can be obtained from the IETF on-line IPR repository at - http://www.ietf.org/ipr. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights that may cover technology that may be required to implement - this standard. Please address the information to the IETF at - ietf-ipr@ietf.org. - - -Disclaimer of Validity - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Copyright Statement - - Copyright (C) The Internet Society (2006). This document is subject - to the rights, licenses and restrictions contained in BCP 78, and - except as set forth therein, the authors retain all their rights. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - -Weiler & Ihren Expires July 24, 2006 [Page 11] - diff --git a/doc/draft/draft-ietf-dnsext-dnssec-trans-02.txt b/doc/draft/draft-ietf-dnsext-dnssec-trans-02.txt deleted file mode 100644 index dd8cbf0682..0000000000 --- a/doc/draft/draft-ietf-dnsext-dnssec-trans-02.txt +++ /dev/null @@ -1,839 +0,0 @@ - -DNS Extensions Working Group R. Arends -Internet-Draft Telematica Instituut -Expires: August 25, 2005 P. Koch - DENIC eG - J. Schlyter - NIC-SE - February 21, 2005 - - - Evaluating DNSSEC Transition Mechanisms - draft-ietf-dnsext-dnssec-trans-02.txt - -Status of this Memo - - This document is an Internet-Draft and is subject to all provisions - of Section 3 of RFC 3667. By submitting this Internet-Draft, each - author represents that any applicable patent or other IPR claims of - which he or she is aware have been or will be disclosed, and any of - which he or she become aware will be disclosed, in accordance with - RFC 3668. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as - Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on August 25, 2005. - -Copyright Notice - - Copyright (C) The Internet Society (2005). - -Abstract - - This document collects and summarizes different proposals for - alternative and additional strategies for authenticated denial in DNS - responses, evaluates these proposals and gives a recommendation for a - - - -Arends, et al. Expires August 25, 2005 [Page 1] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - way forward. - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Transition Mechanisms . . . . . . . . . . . . . . . . . . . . 3 - 2.1 Mechanisms With Need of Updating DNSSEC-bis . . . . . . . 4 - 2.1.1 Dynamic NSEC Synthesis . . . . . . . . . . . . . . . . 4 - 2.1.2 Add Versioning/Subtyping to Current NSEC . . . . . . . 5 - 2.1.3 Type Bit Map NSEC Indicator . . . . . . . . . . . . . 6 - 2.1.4 New Apex Type . . . . . . . . . . . . . . . . . . . . 6 - 2.1.5 NSEC White Lies . . . . . . . . . . . . . . . . . . . 7 - 2.1.6 NSEC Optional via DNSSKEY Flag . . . . . . . . . . . . 8 - 2.1.7 New Answer Pseudo RR Type . . . . . . . . . . . . . . 9 - 2.1.8 SIG(0) Based Authenticated Denial . . . . . . . . . . 9 - 2.2 Mechanisms Without Need of Updating DNSSEC-bis . . . . . . 10 - 2.2.1 Partial Type-code and Signal Rollover . . . . . . . . 10 - 2.2.2 A Complete Type-code and Signal Rollover . . . . . . . 11 - 2.2.3 Unknown Algorithm in RRSIG . . . . . . . . . . . . . . 11 - 3. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 12 - 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 - 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 5.1 Normative References . . . . . . . . . . . . . . . . . . . 13 - 5.2 Informative References . . . . . . . . . . . . . . . . . . 13 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14 - Intellectual Property and Copyright Statements . . . . . . . . 15 - - - - - - - - - - - - - - - - - - - - - - - - - -Arends, et al. Expires August 25, 2005 [Page 2] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -1. Introduction - - This report shall document the process of dealing with the NSEC - walking problem late in the Last Call for - [I-D.ietf-dnsext-dnssec-intro, I-D.ietf-dnsext-dnssec-protocol, - I-D.ietf-dnsext-dnssec-records]. It preserves some of the discussion - that took place in the DNSEXT WG during the first half of June 2004 - as well as some additional ideas that came up subsequently. - - This is an edited excerpt of the chairs' mail to the WG: - The working group consents on not including NSEC-alt in the - DNSSEC-bis documents. The working group considers to take up - "prevention of zone enumeration" as a work item. - There may be multiple mechanisms to allow for co-existence with - DNSSEC-bis. The chairs allow the working group a little over a - week (up to June 12, 2004) to come to consensus on a possible - modification to the document to enable gentle rollover. If that - consensus cannot be reached the DNSSEC-bis documents will go out - as-is. - - To ease the process of getting consensus, a summary of the proposed - solutions and analysis of the pros and cons were written during the - weekend. - - This summary includes: - - An inventory of the proposed mechanisms to make a transition to - future work on authenticated denial of existence. - List the known Pros and Cons, possibly provide new arguments, and - possible security considerations of these mechanisms. - Provide a recommendation on a way forward that is least disruptive - to the DNSSEC-bis specifications as they stand and keep an open - path to other methods for authenticated denial of existence. - - The descriptions of the proposals in this document are coarse and do - not cover every detail necessary for implementation. In any case, - documentation and further study is needed before implementaion and/or - deployment, including those which seem to be solely operational in - nature. - -2. Transition Mechanisms - - In the light of recent discussions and past proposals, we have found - several ways to allow for transition to future expansion of - authenticated denial. We tried to illuminate the paths and pitfalls - in these ways forward. Some proposals lead to a versioning of - DNSSEC, where DNSSEC-bis may co-exist with DNSSEC-ter, other - proposals are 'clean' but may cause delay, while again others may be - - - -Arends, et al. Expires August 25, 2005 [Page 3] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - plain hacks. - - Some paths do not introduce versioning, and might require the current - DNSSEC-bis documents to be fully updated to allow for extensions to - authenticated denial mechanisms. Other paths introduce versioning - and do not (or minimally) require DNSSEC-bis documents to be updated, - allowing DNSSEC-bis to be deployed, while future versions can be - drafted independent from or partially depending on DNSSEC-bis. - -2.1 Mechanisms With Need of Updating DNSSEC-bis - - Mechanisms in this category demand updates to the DNSSEC-bis document - set. - -2.1.1 Dynamic NSEC Synthesis - - This proposal assumes that NSEC RRs and the authenticating RRSIG will - be generated dynamically to just cover the (non existent) query name. - The owner name is (the) one preceding the name queried for, the Next - Owner Name Field has the value of the Query Name Field + 1 (first - successor in canonical ordering). A separate key (the normal ZSK or - a separate ZSK per authoritative server) would be used for RRSIGs on - NSEC RRs. This is a defense against enumeration, though it has the - presumption of online signing. - -2.1.1.1 Coexistence and Migration - - There is no change in interpretation other then that the next owner - name might or might not exist. - -2.1.1.2 Limitations - - This introduces an unbalanced cost between query and response - generation due to dynamic generation of signatures. - -2.1.1.3 Amendments to DNSSEC-bis - - The current DNSSEC-bis documents might need to be updated to indicate - that the next owner name might not be an existing name in the zone. - This is not a real change to the spec since implementers have been - warned not to synthesize with previously cached NSEC records. A - specific bit to identify the dynamic signature generating key might - be useful as well, to prevent it from being used to fake positive - data. - -2.1.1.4 Cons - - Unbalanced cost is a ground for DDoS. Though this protects against - - - -Arends, et al. Expires August 25, 2005 [Page 4] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - enumeration, it is not really a path for versioning. - -2.1.1.5 Pros - - Hardly any amendments to DNSSEC-bis. - -2.1.2 Add Versioning/Subtyping to Current NSEC - - This proposal introduces versioning for the NSEC RR type (a.k.a. - subtyping) by adding a (one octet) version field to the NSEC RDATA. - Version number 0 is assigned to the current (DNSSEC-bis) meaning, - making this an 'Must Be Zero' (MBZ) for the to be published docset. - -2.1.2.1 Coexistence and Migration - - Since the versioning is done inside the NSEC RR, different versions - may coexist. However, depending on future methods, that may or may - not be useful inside a single zone. Resolvers cannot ask for - specific NSEC versions but may be able to indicate version support by - means of a to be defined EDNS option bit. - -2.1.2.2 Limitations - - There are no technical limitations, though it will cause delay to - allow testing of the (currently unknown) new NSEC interpretation. - - Since the versioning and signaling is done inside the NSEC RR, future - methods will likely be restricted to a single RR type authenticated - denial (as opposed to e.g. NSEC-alt, which currently proposes three - RR types). - -2.1.2.3 Amendments to DNSSEC-bis - - Full Update of the current DNSSEC-bis documents to provide for new - fields in NSEC, while specifying behavior in case of unknown field - values. - -2.1.2.4 Cons - - Though this is a clean and clear path without versioning DNSSEC, it - takes some time to design, gain consensus, update the current - dnssec-bis document, test and implement a new authenticated denial - record. - -2.1.2.5 Pros - - Does not introduce an iteration to DNSSEC while providing a clear and - clean migration strategy. - - - -Arends, et al. Expires August 25, 2005 [Page 5] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -2.1.3 Type Bit Map NSEC Indicator - - Bits in the type-bit-map are reused or allocated to signify the - interpretation of NSEC. - - This proposal assumes that future extensions make use of the existing - NSEC RDATA syntax, while it may need to change the interpretation of - the RDATA or introduce an alternative denial mechanism, invoked by - the specific type-bit-map-bits. - -2.1.3.1 Coexistence and migration - - Old and new NSEC meaning could coexist, depending how the signaling - would be defined. The bits for NXT, NSEC, RRSIG or other outdated RR - types are available as well as those covering meta/query types or - types to be specifically allocated. - -2.1.3.2 Limitations - - This mechanism uses an NSEC field that was not designed for that - purpose. Similar methods were discussed during the Opt-In discussion - and the Silly-State discussion. - -2.1.3.3 Amendments to DNSSEC-bis - - The specific type-bit-map-bits must be allocated and they need to be - specified as 'Must Be Zero' (MBZ) when used for standard (dnssec-bis) - interpretation. Also, behaviour of the resolver and validator must - be documented in case unknown values are encountered for the MBZ - field. Currently the protocol document specifies that the validator - MUST ignore the setting of the NSEC and the RRSIG bits, while other - bits are only used for the specific purpose of the type-bit-map field - -2.1.3.4 Cons - - The type-bit-map was not designed for this purpose. It is a - straightforward hack. Text in protocol section 5.4 was put in - specially to defend against this usage. - -2.1.3.5 Pros - - No change needed to the on-the-wire protocol as specified in the - current docset. - -2.1.4 New Apex Type - - This introduces a new Apex type (parallel to the zone's SOA) - indicating the DNSSEC version (or authenticated denial) used in or - - - -Arends, et al. Expires August 25, 2005 [Page 6] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - for this zone. - -2.1.4.1 Coexistence and Migration - - Depending on the design of this new RR type multiple denial - mechanisms may coexist in a zone. Old validators will not understand - and thus ignore the new type, so interpretation of the new NSEC - scheme may fail, negative responses may appear 'bogus'. - -2.1.4.2 Limitations - - A record of this kind is likely to carry additional - feature/versioning indications unrelated to the current question of - authenticated denial. - -2.1.4.3 Amendments to DNSSEC-bis - - The current DNSSEC-bis documents need to be updated to indicate that - the absence of this type indicates dnssec-bis, and that the (mere) - presence of this type indicated unknown versions. - -2.1.4.4 Cons - - The only other 'zone' or 'apex' record is the SOA record. Though - this proposal is not new, it is yet unknown how it might fulfill - authenticated denial extensions. This new RR type would only provide - for a generalized signaling mechanism, not the new authenticated - denial scheme. Since it is likely to be general in nature, due to - this generality consensus is not to be reached soon. - -2.1.4.5 Pros - - This approach would allow for a lot of other per zone information to - be transported or signaled to both (slave) servers and resolvers. - -2.1.5 NSEC White Lies - - This proposal disables one part of NSEC (the pointer part) by means - of a special target (root, apex, owner, ...), leaving intact only the - ability to authenticate denial of existence of RR sets, not denial of - existence of domain names (NXDOMAIN). It may be necessary to have - one working NSEC to prove the absence of a wildcard. - -2.1.5.1 Coexistence and Migration - - The NSEC target can be specified per RR, so standard NSEC and 'white - lie' NSEC can coexist in a zone. There is no need for migration - because no versioning is introduced or intended. - - - -Arends, et al. Expires August 25, 2005 [Page 7] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -2.1.5.2 Limitations - - This proposal breaks the protocol and is applicable to certain types - of zones only (no wildcard, no deep names, delegation only). Most of - the burden is put on the resolver side and operational consequences - are yet to be studied. - -2.1.5.3 Amendments to DNSSEC-bis - - The current DNSSEC-bis documents need to be updated to indicate that - the NXDOMAIN responses may be insecure. - -2.1.5.4 Cons - - Strictly speaking this breaks the protocol and doesn't fully fulfill - the requirements for authenticated denial of existence. Security - implications need to be carefully documented: search path problems - (forged denial of existence may lead to wrong expansion of non-FQDNs - [RFC1535]) and replay attacks to deny existence of records. - -2.1.5.5 Pros - - Hardly any amendments to DNSSEC-bis. Operational "trick" that is - available anyway. - -2.1.6 NSEC Optional via DNSSKEY Flag - - A new DNSKEY may be defined to declare NSEC optional per zone. - -2.1.6.1 Coexistence and Migration - - Current resolvers/validators will not understand the Flag bit and - will have to treat negative responses as bogus. Otherwise, no - migration path is needed since NSEC is simply turned off. - -2.1.6.2 Limitations - - NSEC can only be made completely optional at the cost of being unable - to prove unsecure delegations (absence of a DS RR [RFC3658]). A next - to this approach would just disable authenticated denial for - non-existence of nodes. - -2.1.6.3 Amendments to DNSSEC-bis - - New DNSKEY Flag to be defined. Resolver/Validator behaviour needs to - be specified in the light of absence of authenticated denial. - - - - - -Arends, et al. Expires August 25, 2005 [Page 8] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -2.1.6.4 Cons - - Doesn't fully meet requirements. Operational consequences to be - studied. - -2.1.6.5 Pros - - Official version of the "trick" presented in (8). Operational - problems can be addressed during future work on validators. - -2.1.7 New Answer Pseudo RR Type - - A new pseudo RR type may be defined that will be dynamically created - (and signed) by the responding authoritative server. The RR in the - response will cover the QNAME, QCLASS and QTYPE and will authenticate - both denial of existence of name (NXDOMAIN) or RRset. - -2.1.7.1 Coexistence and Migration - - Current resolvers/validators will not understand the pseudo RR and - will thus not be able to process negative responses so testified. A - signaling or solicitation method would have to be specified. - -2.1.7.2 Limitations - - This method can only be used with online keys and online signing - capacity. - -2.1.7.3 Amendments to DNSSEC-bis - - Signaling method needs to be defined. - -2.1.7.4 Cons - - Keys have to be held and processed online with all security - implications. An additional flag for those keys identifying them as - online or negative answer only keys should be considered. - -2.1.7.5 Pros - - Expands DNSSEC authentication to the RCODE. - -2.1.8 SIG(0) Based Authenticated Denial - - -2.1.8.1 Coexistence and Migration - - - - - -Arends, et al. Expires August 25, 2005 [Page 9] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -2.1.8.2 Limitations - - -2.1.8.3 Amendments to DNSSEC-bis - - -2.1.8.4 Cons - - -2.1.8.5 Pros - - -2.2 Mechanisms Without Need of Updating DNSSEC-bis - -2.2.1 Partial Type-code and Signal Rollover - - Carefully crafted type code/signal rollover to define a new - authenticated denial space that extends/replaces DNSSEC-bis - authenticated denial space. This particular path is illuminated by - Paul Vixie in a Message-Id <20040602070859.0F50913951@sa.vix.com> - posted to 2004-06-02. - -2.2.1.1 Coexistence and Migration - - To protect the current resolver for future versions, a new DNSSEC-OK - bit must be allocated to make clear it does or does not understand - the future version. Also, a new DS type needs to be allocated to - allow differentiation between a current signed delegation and a - 'future' signed delegation. Also, current NSEC needs to be rolled - into a new authenticated denial type. - -2.2.1.2 Limitations - - None. - -2.2.1.3 Amendments to DNSSEC-bis - - None. - -2.2.1.4 Cons - - It is cumbersome to carefully craft an TCR that 'just fits'. The - DNSSEC-bis protocol has many 'borderline' cases that needs special - consideration. It might be easier to do a full TCR, since a few of - the types and signals need upgrading anyway. - - - - - - -Arends, et al. Expires August 25, 2005 [Page 10] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -2.2.1.5 Pros - - Graceful adoption of future versions of NSEC, while there are no - amendments to DNSSEC-bis. - -2.2.2 A Complete Type-code and Signal Rollover - - A new DNSSEC space is defined which can exist independent of current - DNSSEC-bis space. - - This proposal assumes that all current DNSSEC type-codes - (RRSIG/DNSKEY/NSEC/DS) and signals (DNSSEC-OK) are not used in any - future versions of DNSSEC. Any future version of DNSSEC has its own - types to allow for keys, signatures, authenticated denial, etcetera. - -2.2.2.1 Coexistence and Migration - - Both spaces can co-exist. They can be made completely orthogonal. - -2.2.2.2 Limitations - - None. - -2.2.2.3 Amendments to DNSSEC-bis - - None. - -2.2.2.4 Cons - - With this path we abandon the current DNSSEC-bis. Though it is easy - to role specific well-known and well-tested parts into the re-write, - once deployment has started this path is very expensive for - implementers, registries, registrars and registrants as well as - resolvers/users. A TCR is not to be expected to occur frequently, so - while a next generation authenticated denial may be enabled by a TCR, - it is likely that that TCR will only be agreed upon if it serves a - whole basket of changes or additions. A quick introduction of - NSEC-ng should not be expected from this path. - -2.2.2.5 Pros - - No amendments/changes to current DNSSEC-bis docset needed. It is - always there as last resort. - -2.2.3 Unknown Algorithm in RRSIG - - This proposal assumes that future extensions make use of the existing - NSEC RDATA syntax, while it may need to change the interpretation of - - - -Arends, et al. Expires August 25, 2005 [Page 11] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - the RDATA or introduce an alternative denial mechanism, invoked by - the specific unknown signing algorithm. The different interpretation - would be signaled by use of different signature algorithms in the - RRSIG records covering the NSEC RRs. - - When an entire zone is signed with a single unknown algorithm, it - will cause implementations that follow current dnssec-bis documents - to treat individual RRsets as unsigned. - -2.2.3.1 Coexistence and migration - - Old and new NSEC RDATA interpretation or known and unknown Signatures - can NOT coexist in a zone since signatures cover complete (NSEC) - RRSets. - -2.2.3.2 Limitations - - Validating resolvers agnostic of new interpretation will treat the - NSEC RRset as "not signed". This affects wildcard and non-existence - proof, as well as proof for (un)secured delegations. Also, all - positive signatures (RRSIGs on RRSets other than DS, NSEC) appear - insecure/bogus to an old validator. - - The algorithm version space is split for each future version of - DNSSEC. Violation of the 'modular components' concept. We use the - 'validator' to protect the 'resolver' from unknown interpretations. - -2.2.3.3 Amendments to DNSSEC-bis - - None. - -2.2.3.4 Cons - - The algorithm field was not designed for this purpose. This is a - straightforward hack. - -2.2.3.5 Pros - - No amendments/changes to current DNSSEC-bis docset needed. - -3. Recommendation - - The authors recommend that the working group commits to and starts - work on a partial TCR, allowing graceful transition towards a future - version of NSEC. Meanwhile, to accomodate the need for an - immediately, temporary, solution against zone-traversal, we recommend - On-Demand NSEC synthesis. - - - - -Arends, et al. Expires August 25, 2005 [Page 12] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - This approach does not require any mandatory changes to DNSSEC-bis, - does not violate the protocol and fulfills the requirements. As a - side effect, it moves the cost of implementation and deployment to - the users (zone owners) of this mechanism. - -4. Acknowledgements - - The authors would like to thank Sam Weiler and Mark Andrews for their - input and constructive comments. - -5. References - -5.1 Normative References - - [I-D.ietf-dnsext-dnssec-intro] - Arends, R., Austein, R., Massey, D., Larson, M. and S. - Rose, "DNS Security Introduction and Requirements", - Internet-Draft draft-ietf-dnsext-dnssec-intro-13, October - 2004. - - [I-D.ietf-dnsext-dnssec-protocol] - Arends, R., "Protocol Modifications for the DNS Security - Extensions", - Internet-Draft draft-ietf-dnsext-dnssec-protocol-09, - October 2004. - - [I-D.ietf-dnsext-dnssec-records] - Arends, R., "Resource Records for the DNS Security - Extensions", - Internet-Draft draft-ietf-dnsext-dnssec-records-11, - October 2004. - - [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", - STD 13, RFC 1034, November 1987. - - [RFC1035] Mockapetris, P., "Domain names - implementation and - specification", STD 13, RFC 1035, November 1987. - - [RFC2931] Eastlake, D., "DNS Request and Transaction Signatures ( - SIG(0)s)", RFC 2931, September 2000. - -5.2 Informative References - - [RFC1535] Gavron, E., "A Security Problem and Proposed Correction - With Widely Deployed DNS Software", RFC 1535, October - 1993. - - [RFC2535] Eastlake, D., "Domain Name System Security Extensions", - - - -Arends, et al. Expires August 25, 2005 [Page 13] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - - RFC 2535, March 1999. - - [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, - June 1999. - - [RFC3658] Gudmundsson, O., "Delegation Signer (DS) Resource Record - (RR)", RFC 3658, December 2003. - - -Authors' Addresses - - Roy Arends - Telematica Instituut - Brouwerijstraat 1 - Enschede 7523 XC - The Netherlands - - Phone: +31 53 4850485 - Email: roy.arends@telin.nl - - - Peter Koch - DENIC eG - Wiesenh"uttenplatz 26 - Frankfurt 60329 - Germany - - Phone: +49 69 27235 0 - Email: pk@DENIC.DE - - - Jakob Schlyter - NIC-SE - Box 5774 - Stockholm SE-114 87 - Sweden - - Email: jakob@nic.se - URI: http://www.nic.se/ - - - - - - - - - - - - -Arends, et al. Expires August 25, 2005 [Page 14] - -Internet-Draft Evaluating DNSSEC Transition Mechanisms February 2005 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - Intellectual Property Rights or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; nor does it represent that it has - made any independent effort to identify any such rights. 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Please address the information to the IETF at - ietf-ipr@ietf.org. - - -Disclaimer of Validity - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Copyright Statement - - Copyright (C) The Internet Society (2005). This document is subject - to the rights, licenses and restrictions contained in BCP 78, and - except as set forth therein, the authors retain all their rights. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - -Arends, et al. Expires August 25, 2005 [Page 15] - - diff --git a/doc/draft/draft-ietf-dnsext-ds-sha256-05.txt b/doc/draft/draft-ietf-dnsext-ds-sha256-05.txt deleted file mode 100644 index 2460cb619b..0000000000 --- a/doc/draft/draft-ietf-dnsext-ds-sha256-05.txt +++ /dev/null @@ -1,504 +0,0 @@ - - - -Network Working Group W. Hardaker -Internet-Draft Sparta -Expires: August 25, 2006 February 21, 2006 - - - Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs) - draft-ietf-dnsext-ds-sha256-05.txt - -Status of this Memo - - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on August 25, 2006. - -Copyright Notice - - Copyright (C) The Internet Society (2006). - -Abstract - - This document specifies how to use the SHA-256 digest type in DNS - Delegation Signer (DS) Resource Records (RRs). DS records, when - stored in a parent zone, point to key signing DNSKEY key(s) in a - child zone. - - - - - - - - -Hardaker Expires August 25, 2006 [Page 1] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Implementing the SHA-256 algorithm for DS record support . . . 3 - 2.1. DS record field values . . . . . . . . . . . . . . . . . . 3 - 2.2. DS Record with SHA-256 Wire Format . . . . . . . . . . . . 3 - 2.3. Example DS Record Using SHA-256 . . . . . . . . . . . . . . 4 - 3. Implementation Requirements . . . . . . . . . . . . . . . . . . 4 - 4. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 - 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 - 6.1. Potential Digest Type Downgrade Attacks . . . . . . . . . . 5 - 6.2. SHA-1 vs SHA-256 Considerations for DS Records . . . . . . 6 - 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 - 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 - Intellectual Property and Copyright Statements . . . . . . . . . . 9 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Hardaker Expires August 25, 2006 [Page 2] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - -1. Introduction - - The DNSSEC [RFC4033] [RFC4034] [RFC4035] DS RR is published in parent - zones to distribute a cryptographic digest of a child's Key Signing - Key (KSK) DNSKEY RR. The DS RRset is signed by at least one of the - parent zone's private zone data signing keys for each algorithm in - use by the parent. Each signature is published in an RRSIG resource - record, owned by the same domain as the DS RRset and with a type - covered of DS. - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in [RFC2119]. - - -2. Implementing the SHA-256 algorithm for DS record support - - This document specifies that the digest type code [XXX: To be - assigned by IANA; likely 2] is to be assigned to SHA-256 [SHA256] - [SHA256CODE] for use within DS records. The results of the digest - algorithm MUST NOT be truncated and the entire 32 byte digest result - is to be published in the DS record. - -2.1. DS record field values - - Using the SHA-256 digest algorithm within a DS record will make use - of the following DS-record fields: - - Digest type: [XXX: To be assigned by IANA; likely 2] - - Digest: A SHA-256 bit digest value calculated by using the following - formula ("|" denotes concatenation). The resulting value is not - truncated and the entire 32 byte result is to used in the - resulting DS record and related calculations. - - digest = SHA_256(DNSKEY owner name | DNSKEY RDATA) - - where DNSKEY RDATA is defined by [RFC4034] as: - - DNSKEY RDATA = Flags | Protocol | Algorithm | Public Key - - The Key Tag field and Algorithm fields remain unchanged by this - document and are specified in the [RFC4034] specification. - -2.2. DS Record with SHA-256 Wire Format - - The resulting on-the-wire format for the resulting DS record will be - [XXX: IANA assignment should replace the 2 below]: - - - -Hardaker Expires August 25, 2006 [Page 3] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - - 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 - 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Key Tag | Algorithm | DigestType=2 | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - / / - / Digest (length for SHA-256 is 32 bytes) / - / / - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| - -2.3. Example DS Record Using SHA-256 - - The following is an example DNSKEY and matching DS record. This - DNSKEY record comes from the example DNSKEY/DS records found in - section 5.4 of [RFC4034]. - - The DNSKEY record: - - dskey.example.com. 86400 IN DNSKEY 256 3 5 ( AQOeiiR0GOMYkDshWoSKz9Xz - fwJr1AYtsmx3TGkJaNXVbfi/ - 2pHm822aJ5iI9BMzNXxeYCmZ - DRD99WYwYqUSdjMmmAphXdvx - egXd/M5+X7OrzKBaMbCVdFLU - Uh6DhweJBjEVv5f2wwjM9Xzc - nOf+EPbtG9DMBmADjFDc2w/r - ljwvFw== - ) ; key id = 60485 - - The resulting DS record covering the above DNSKEY record using a SHA- - 256 digest: [RFC Editor: please replace XXX with the assigned digest - type (likely 2):] - - dskey.example.com. 86400 IN DS 60485 5 XXX ( D4B7D520E7BB5F0F67674A0C - CEB1E3E0614B93C4F9E99B83 - 83F6A1E4469DA50A ) - - -3. Implementation Requirements - - Implementations MUST support the use of the SHA-256 algorithm in DS - RRs. Validator implementations SHOULD ignore DS RRs containing SHA-1 - digests if DS RRs with SHA-256 digests are present in the DS RRset. - - -4. Deployment Considerations - - If a validator does not support the SHA-256 digest type and no other - DS RR exists in a zone's DS RRset with a supported digest type, then - - - -Hardaker Expires August 25, 2006 [Page 4] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - - the validator has no supported authentication path leading from the - parent to the child. The resolver should treat this case as it would - the case of an authenticated NSEC RRset proving that no DS RRset - exists, as described in [RFC4035], section 5.2. - - Because zone administrators can not control the deployment speed of - support for SHA-256 in validators that may be referencing any of - their zones, zone operators should consider deploying both SHA-1 and - SHA-256 based DS records. This should be done for every DNSKEY for - which DS records are being generated. Whether to make use of both - digest types and for how long is a policy decision that extends - beyond the scope of this document. - - -5. IANA Considerations - - Only one IANA action is required by this document: - - The Digest Type to be used for supporting SHA-256 within DS records - needs to be assigned by IANA. This document requests that the Digest - Type value of 2 be assigned to the SHA-256 digest algorithm. - - At the time of this writing, the current digest types assigned for - use in DS records are as follows: - - VALUE Digest Type Status - 0 Reserved - - 1 SHA-1 MANDATORY - 2 SHA-256 MANDATORY - 3-255 Unassigned - - - -6. Security Considerations - -6.1. Potential Digest Type Downgrade Attacks - - A downgrade attack from a stronger digest type to a weaker one is - possible if all of the following are true: - - o A zone includes multiple DS records for a given child's DNSKEY, - each of which use a different digest type. - - o A validator accepts a weaker digest even if a stronger one is - present but invalid. - - For example, if the following conditions are all true: - - - - - -Hardaker Expires August 25, 2006 [Page 5] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - - o Both SHA-1 and SHA-256 based digests are published in DS records - within a parent zone for a given child zone's DNSKEY. - - o The DS record with the SHA-1 digest matches the digest computed - using the child zone's DNSKEY. - - o The DS record with the SHA-256 digest fails to match the digest - computed using the child zone's DNSKEY. - - Then if the validator accepts the above situation as secure then this - can be used as a downgrade attack since the stronger SHA-256 digest - is ignored. - -6.2. SHA-1 vs SHA-256 Considerations for DS Records - - Users of DNSSEC are encouraged to deploy SHA-256 as soon as software - implementations allow for it. SHA-256 is widely believed to be more - resilient to attack than SHA-1, and confidence in SHA-1's strength is - being eroded by recently-announced attacks. Regardless of whether or - not the attacks on SHA-1 will affect DNSSEC, it is believed (at the - time of this writing) that SHA-256 is the better choice for use in DS - records. - - At the time of this publication, the SHA-256 digest algorithm is - considered sufficiently strong for the immediate future. It is also - considered sufficient for use in DNSSEC DS RRs for the immediate - future. However, future published attacks may weaken the usability - of this algorithm within the DS RRs. It is beyond the scope of this - document to speculate extensively on the cryptographic strength of - the SHA-256 digest algorithm. - - Likewise, it is also beyond the scope of this document to specify - whether or for how long SHA-1 based DS records should be - simultaneously published alongside SHA-256 based DS records. - - -7. Acknowledgments - - This document is a minor extension to the existing DNSSEC documents - and those authors are gratefully appreciated for the hard work that - went into the base documents. - - The following people contributed to portions of this document in some - fashion: Mark Andrews, Roy Arends, Olafur Gudmundsson, Paul Hoffman, - Olaf M. Kolkman, Edward Lewis, Scott Rose, Stuart E. Schechter, Sam - Weiler. - - - - - -Hardaker Expires August 25, 2006 [Page 6] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - -8. References - -8.1. Normative References - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - - [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "DNS Security Introduction and Requirements", - RFC 4033, March 2005. - - [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Resource Records for the DNS Security Extensions", - RFC 4034, March 2005. - - [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Protocol Modifications for the DNS Security - Extensions", RFC 4035, March 2005. - - [SHA256] National Institute of Standards and Technology, "Secure - Hash Algorithm. NIST FIPS 180-2", August 2002. - -8.2. Informative References - - [SHA256CODE] - Eastlake, D., "US Secure Hash Algorithms (SHA)", - June 2005. - - - - - - - - - - - - - - - - - - - - - - - - -Hardaker Expires August 25, 2006 [Page 7] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - -Author's Address - - Wes Hardaker - Sparta - P.O. Box 382 - Davis, CA 95617 - US - - Email: hardaker@tislabs.com - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Hardaker Expires August 25, 2006 [Page 8] - -Internet-Draft Use of SHA-256 in DNSSEC DS RRs February 2006 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - Intellectual Property Rights or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; nor does it represent that it has - made any independent effort to identify any such rights. Information - on the procedures with respect to rights in RFC documents can be - found in BCP 78 and BCP 79. - - Copies of IPR disclosures made to the IETF Secretariat and any - assurances of licenses to be made available, or the result of an - attempt made to obtain a general license or permission for the use of - such proprietary rights by implementers or users of this - specification can be obtained from the IETF on-line IPR repository at - http://www.ietf.org/ipr. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights that may cover technology that may be required to implement - this standard. Please address the information to the IETF at - ietf-ipr@ietf.org. - - -Disclaimer of Validity - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Copyright Statement - - Copyright (C) The Internet Society (2006). This document is subject - to the rights, licenses and restrictions contained in BCP 78, and - except as set forth therein, the authors retain all their rights. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - -Hardaker Expires August 25, 2006 [Page 9] - diff --git a/doc/draft/draft-ietf-dnsext-forgery-resilience-02.txt b/doc/draft/draft-ietf-dnsext-forgery-resilience-02.txt deleted file mode 100644 index 87bce00b5c..0000000000 --- a/doc/draft/draft-ietf-dnsext-forgery-resilience-02.txt +++ /dev/null @@ -1,17 +0,0 @@ - -This Internet-Draft, draft-ietf-dnsext-forgery-resilience-01.txt, has expired, and has been deleted -from the Internet-Drafts directory. An Internet-Draft expires 185 days from -the date that it is posted unless it is replaced by an updated version, or the -Secretariat has been notified that the document is under official review by the -IESG or has been passed to the RFC Editor for review and/or publication as an -RFC. This Internet-Draft was not published as an RFC. - -Internet-Drafts are not archival documents, and copies of Internet-Drafts that have -been deleted from the directory are not available. The Secretariat does not have -any information regarding the future plans of the author(s) or working group, if -applicable, with respect to this deleted Internet-Draft. For more information, or -to request a copy of the document, please contact the author(s) directly. - -Draft Author(s): -Remco van Mook , -Bert Hubert diff --git a/doc/draft/draft-ietf-dnsext-keyrr-key-signing-flag-12.txt b/doc/draft/draft-ietf-dnsext-keyrr-key-signing-flag-12.txt deleted file mode 100644 index 6bffb70423..0000000000 --- a/doc/draft/draft-ietf-dnsext-keyrr-key-signing-flag-12.txt +++ /dev/null @@ -1,560 +0,0 @@ - -DNS Extensions O. Kolkman -Internet-Draft RIPE NCC -Expires: June 17, 2004 J. Schlyter - - E. Lewis - ARIN - December 18, 2003 - - - DNSKEY RR Secure Entry Point Flag - draft-ietf-dnsext-keyrr-key-signing-flag-12 - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on June 17, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2003). All Rights Reserved. - -Abstract - - With the Delegation Signer (DS) resource record the concept of a - public key acting as a secure entry point has been introduced. During - exchanges of public keys with the parent there is a need to - differentiate secure entry point keys from other public keys in the - DNSKEY resource record (RR) set. A flag bit in the DNSKEY RR is - defined to indicate that DNSKEY is to be used as a secure entry - point. The flag bit is intended to assist in operational procedures - to correctly generate DS resource records, or to indicate what - DNSKEYs are intended for static configuration. The flag bit is not to - - - -Kolkman, et al. Expires June 17, 2004 [Page 1] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - be used in the DNS verification protocol. This document updates RFC - 2535 and RFC 3445. - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. The Secure Entry Point (SEP) Flag . . . . . . . . . . . . . . . 4 - 3. DNSSEC Protocol Changes . . . . . . . . . . . . . . . . . . . . 5 - 4. Operational Guidelines . . . . . . . . . . . . . . . . . . . . . 5 - 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 - 7. Internationalization Considerations . . . . . . . . . . . . . . 6 - 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 - Normative References . . . . . . . . . . . . . . . . . . . . . . 7 - Informative References . . . . . . . . . . . . . . . . . . . . . 7 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 - Intellectual Property and Copyright Statements . . . . . . . . . 9 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Kolkman, et al. Expires June 17, 2004 [Page 2] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - -1. Introduction - - "All keys are equal but some keys are more equal than others" [6] - - With the definition of the Delegation Signer Resource Record (DS RR) - [5] it has become important to differentiate between the keys in the - DNSKEY RR set that are (to be) pointed to by parental DS RRs and the - other keys in the DNSKEY RR set. We refer to these public keys as - Secure Entry Point (SEP) keys. A SEP key either used to generate a - DS RR or is distributed to resolvers that use the key as the root of - a trusted subtree[3]. - - In early deployment tests, the use of two (kinds of) key pairs for - each zone has been prevalent. For one kind of key pair the private - key is used to sign just the zone's DNSKEY resource record (RR) set. - Its public key is intended to be referenced by a DS RR at the parent - or configured statically in a resolver. The private key of the other - kind of key pair is used to sign the rest of the zone's data sets. - The former key pair is called a key-signing key (KSK) and the latter - is called a zone-signing key (ZSK). In practice there have been - usually one of each kind of key pair, but there will be multiples of - each at times. - - It should be noted that division of keys pairs into KSK's and ZSK's - is not mandatory in any definition of DNSSEC, not even with the - introduction of the DS RR. But, in testing, this distinction has - been helpful when designing key roll over (key super-cession) - schemes. Given that the distinction has proven helpful, the labels - KSK and ZSK have begun to stick. - - There is a need to differentiate the public keys for the key pairs - that are used for key signing from keys that are not used key signing - (KSKs vs ZSKs). This need is driven by knowing which DNSKEYs are to - be sent for generating DS RRs, which DNSKEYs are to be distributed to - resolvers, and which keys are fed to the signer application at the - appropriate time. - - In other words, the SEP bit provides an in-band method to communicate - a DNSKEY RR's intended use to third parties. As an example we present - 3 use cases in which the bit is useful: - - The parent is a registry, the parent and the child use secured DNS - queries and responses, with a preexisting trust-relation, or plain - DNS over a secured channel to exchange the child's DNSKEY RR - sets. Since a DNSKEY RR set will contain a complete DNSKEY RRset - the SEP bit can be used to isolate the DNSKEYs for which a DS RR - needs to be created. - - - - -Kolkman, et al. Expires June 17, 2004 [Page 3] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - An administrator has configured a DNSKEY as root for a trusted - subtree into security aware resolver. Using a special purpose tool - that queries for the KEY RRs from that domain's apex, the - administrator will be able to notice the roll over of the trusted - anchor by a change of the subset of KEY RRs with the DS flag set. - - A signer might use the SEP bit on the public key to determine - which private key to use to exclusively sign the DNSKEY RRset and - which private key to use to sign the other RRsets in the zone. - - As demonstrated in the above examples it is important to be able to - differentiate the SEP keys from the other keys in a DNSKEY RR set in - the flow between signer and (parental) key-collector and in the flow - between the signer and the resolver configuration. The SEP flag is to - be of no interest to the flow between the verifier and the - authoritative data store. - - The reason for the term "SEP" is a result of the observation that the - distinction between KSK and ZSK key pairs is made by the signer, a - key pair could be used as both a KSK and a ZSK at the same time. To - be clear, the term SEP was coined to lessen the confusion caused by - the overlap. ( Once this label was applied, it had the side effect of - removing the temptation to have both a KSK flag bit and a ZSK flag - bit.) - - The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED", - "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be - interpreted as described in RFC2119 [1]. - -2. The Secure Entry Point (SEP) Flag - - - 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 - 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | flags |S| protocol | algorithm | - | |E| | | - | |P| | | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | / - / public key / - / / - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - - DNSKEY RR Format - - - - - - -Kolkman, et al. Expires June 17, 2004 [Page 4] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - This document assigns the 15'th bit in the flags field as the secure - entry point (SEP) bit. If the the bit is set to 1 the key is - intended to be used as secure entry point key. One SHOULD NOT assign - special meaning to the key if the bit is set to 0. Operators can - recognize the secure entry point key by the even or odd-ness of the - decimal representation of the flag field. - -3. DNSSEC Protocol Changes - - The bit MUST NOT be used during the resolving and verification - process. The SEP flag is only used to provide a hint about the - different administrative properties of the key and therefore the use - of the SEP flag does not change the DNS resolution protocol or the - resolution process. - -4. Operational Guidelines - - The SEP bit is set by the key-pair-generator and MAY be used by the - zone signer to decide whether the public part of the key pair is to - be prepared for input to a DS RR generation function. The SEP bit is - recommended to be set (to 1) whenever the public key of the key pair - will be distributed to the parent zone to build the authentication - chain or if the public key is to be distributed for static - configuration in verifiers. - - When a key pair is created, the operator needs to indicate whether - the SEP bit is to be set in the DNSKEY RR. As the SEP bit is within - the data that is used to compute the 'key tag field' in the SIG RR, - changing the SEP bit will change the identity of the key within DNS. - In other words, once a key is used to generate signatures, the - setting of the SEP bit is to remain constant. If not, a verifier will - not be able to find the relevant KEY RR. - - When signing a zone, it is intended that the key(s) with the SEP bit - set (if such keys exist) are used to sign the KEY RR set of the zone. - The same key can be used to sign the rest of the zone data too. It - is conceivable that not all keys with a SEP bit set will sign the - DNSKEY RR set, such keys might be pending retirement or not yet in - use. - - When verifying a RR set, the SEP bit is not intended to play a role. - How the key is used by the verifier is not intended to be a - consideration at key creation time. - - Although the SEP flag provides a hint on which public key is to be - used as trusted root, administrators can choose to ignore the fact - that a DNSKEY has its SEP bit set or not when configuring a trusted - root for their resolvers. - - - -Kolkman, et al. Expires June 17, 2004 [Page 5] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - Using the SEP flag a key roll over can be automated. The parent can - use an existing trust relation to verify DNSKEY RR sets in which a - new DNSKEY RR with the SEP flag appears. - -5. Security Considerations - - As stated in Section 3 the flag is not to be used in the resolution - protocol or to determine the security status of a key. The flag is to - be used for administrative purposes only. - - No trust in a key should be inferred from this flag - trust MUST be - inferred from an existing chain of trust or an out-of-band exchange. - - Since this flag might be used for automating public key exchanges, we - think the following consideration is in place. - - Automated mechanisms for roll over of the DS RR might be vulnerable - to a class of replay attacks. This might happen after a public key - exchange where a DNSKEY RR set, containing two DNSKEY RRs with the - SEP flag set, is sent to the parent. The parent verifies the DNSKEY - RR set with the existing trust relation and creates the new DS RR - from the DNSKEY RR that the current DS RR is not pointing to. This - key exchange might be replayed. Parents are encouraged to implement a - replay defense. A simple defense can be based on a registry of keys - that have been used to generate DS RRs during the most recent roll - over. These same considerations apply to entities that configure keys - in resolvers. - -6. IANA Considerations - - The flag bits in the DNSKEY RR are assigned by IETF consensus and - registered in the DNSKEY Flags registry (created by [4]). This - document assigns the 15th bit in the DNSKEY RR as the Secure Entry - Point (SEP) bit. - -7. Internationalization Considerations - - Although SEP is a popular acronym in many different languages, there - are no internationalization considerations. - -8. Acknowledgments - - The ideas documented in this document are inspired by communications - we had with numerous people and ideas published by other folk. Among - others Mark Andrews, Rob Austein, Miek Gieben, Olafur Gudmundsson, - Daniel Karrenberg, Dan Massey, Scott Rose, Marcos Sanz and Sam Weiler - have contributed ideas and provided feedback. - - - - -Kolkman, et al. Expires June 17, 2004 [Page 6] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - This document saw the light during a workshop on DNSSEC operations - hosted by USC/ISI in August 2002. - -Normative References - - [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement - Levels", BCP 14, RFC 2119, March 1997. - - [2] Eastlake, D., "Domain Name System Security Extensions", RFC - 2535, March 1999. - - [3] Lewis, E., "DNS Security Extension Clarification on Zone - Status", RFC 3090, March 2001. - - [4] Weiler, S., "Legacy Resolver Compatibility for Delegation - Signer", draft-ietf-dnsext-dnssec-2535typecode-change-05 (work - in progress), October 2003. - -Informative References - - [5] Gudmundsson, O., "Delegation Signer Resource Record", - draft-ietf-dnsext-delegation-signer-15 (work in progress), June - 2003. - - [6] Orwell, G. and R. Steadman (illustrator), "Animal Farm; a Fairy - Story", ISBN 0151002177 (50th anniversary edition), April 1996. - - -Authors' Addresses - - Olaf M. Kolkman - RIPE NCC - Singel 256 - Amsterdam 1016 AB - NL - - Phone: +31 20 535 4444 - EMail: olaf@ripe.net - URI: http://www.ripe.net/ - - - Jakob Schlyter - Karl Gustavsgatan 15 - Goteborg SE-411 25 - Sweden - - EMail: jakob@schlyter.se - - - - -Kolkman, et al. Expires June 17, 2004 [Page 7] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - Edward P. Lewis - ARIN - 3635 Concorde Parkway Suite 200 - Chantilly, VA 20151 - US - - Phone: +1 703 227 9854 - EMail: edlewis@arin.net - URI: http://www.arin.net/ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Kolkman, et al. Expires June 17, 2004 [Page 8] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementors or users of this specification can - be obtained from the IETF Secretariat. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights which may cover technology that may be required to practice - this standard. Please address the information to the IETF Executive - Director. - - -Full Copyright Statement - - Copyright (C) The Internet Society (2003). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - - - -Kolkman, et al. Expires June 17, 2004 [Page 9] - -Internet-Draft DNSKEY RR Secure Entry Point Flag December 2003 - - - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Kolkman, et al. Expires June 17, 2004 [Page 10] - - diff --git a/doc/rfc/index b/doc/rfc/index index 83ae404410..2858658729 100644 --- a/doc/rfc/index +++ b/doc/rfc/index @@ -92,6 +92,7 @@ Secret Key Transaction Authentication for DNS (GSS-TSIG) 3655: Redefinition of DNS Authenticated Data (AD) bit 3658: Delegation Signer (DS) Resource Record (RR) +3755: Legacy Resolver Compatibility for Delegation Signer (DS) 3757: Domain Name System KEY (DNSKEY) Resource Record (RR) Secure Entry Point (SEP) Flag 3833: Threat Analysis of the Domain Name System (DNS) @@ -112,6 +113,7 @@ 4408: Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1 4470: Minimally Covering NSEC Records and DNSSEC On-line Signing +4471: Derivation of DNS Name Predecessor and Successor 4509: Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs) 4634: US Secure Hash Algorithms (SHA and HMAC-SHA) 4635: HMAC SHA TSIG Algorithm Identifiers @@ -120,9 +122,15 @@ 4701: A DNS Resource Record (RR) for Encoding Dynamic Host Configuration Protocol (DHCP) Information (DHCID RR) 4892: Requirements for a Mechanism Identifying a Name Server Instance +4955: DNS Security (DNSSEC) Experiments +4956: DNS Security (DNSSEC) Opt-In +5001: DNS Name Server Identifier (NSID) Option 5011: Automated Updates of DNS Security (DNSSEC) Trust Anchors 5155: DNS Security (DNSSEC) Hashed Authenticated Denial of Existence 5205: Host Identity Protocol (HIP) Domain Name System (DNS) Extension +5395: Domain Name System (DNS) IANA Considerations +5452: Measures for Making DNS More Resilient against Forged Answers 5507: Design Choices When Expanding the DNS +5625: DNS Proxy Implementation Guidelines 5702: Use of SHA-2 Algorithms with RSA in DNSKEY and RRSIG Resource Records for DNSSEC diff --git a/doc/rfc/rfc3755.txt b/doc/rfc/rfc3755.txt new file mode 100644 index 0000000000..a9a7cf2692 --- /dev/null +++ b/doc/rfc/rfc3755.txt @@ -0,0 +1,507 @@ + + + + + + +Network Working Group S. Weiler +Request for Comments: 3755 SPARTA, Inc. +Updates: 3658, 2535 May 2004 +Category: Standards Track + + + Legacy Resolver Compatibility for Delegation Signer (DS) + +Status of this Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (2004). All Rights Reserved. + +Abstract + + As the DNS Security (DNSSEC) specifications have evolved, the syntax + and semantics of the DNSSEC resource records (RRs) have changed. + Many deployed nameservers understand variants of these semantics. + Dangerous interactions can occur when a resolver that understands an + earlier version of these semantics queries an authoritative server + that understands the new delegation signer semantics, including at + least one failure scenario that will cause an unsecured zone to be + unresolvable. This document changes the type codes and mnemonics of + the DNSSEC RRs (SIG, KEY, and NXT) to avoid those interactions. + +1. Introduction + + The DNSSEC protocol has been through many iterations whose syntax and + semantics are not completely compatible. This has occurred as part + of the ordinary process of proposing a protocol, implementing it, + testing it in the increasingly complex and diverse environment of the + Internet, and refining the definitions of the initial Proposed + Standard. In the case of DNSSEC, the process has been complicated by + DNS's criticality and wide deployment and the need to add security + while minimizing daily operational complexity. + + A weak area for previous DNS specifications has been lack of detail + in specifying resolver behavior, leaving implementors largely on + their own to determine many details of resolver function. This, + combined with the number of iterations the DNSSEC specifications have + been through, has resulted in fielded code with a wide variety of + + + +Weiler Standards Track [Page 1] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + + behaviors. This variety makes it difficult to predict how a protocol + change will be handled by all deployed resolvers. The risk that a + change will cause unacceptable or even catastrophic failures makes it + difficult to design and deploy a protocol change. One strategy for + managing that risk is to structure protocol changes so that existing + resolvers can completely ignore input that might confuse them or + trigger undesirable failure modes. + + This document addresses a specific problem caused by Delegation + Signer's (DS) [RFC3658] introduction of new semantics for the NXT RR + that are incompatible with the semantics in [RFC2535]. Answers + provided by DS-aware servers can trigger an unacceptable failure mode + in some resolvers that implement RFC 2535, which provides a great + disincentive to sign zones with DS. The changes defined in this + document allow for the incremental deployment of DS. + +1.1. Terminology + + In this document, the term "unsecure delegation" means any delegation + for which no DS record appears at the parent. An "unsecure referral" + is an answer from the parent containing an NS RRset and a proof that + no DS record exists for that name. + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in [RFC2119]. + +1.2. The Problem + + Delegation Signer (DS) introduces new semantics for the NXT RR that + are incompatible with the semantics in RFC 2535. In RFC 2535, NXT + records were only required to be returned as part of a non-existence + proof. With DS, an unsecure referral returns, in addition to the NS, + a proof of non-existence of a DS RR in the form of an NXT and + SIG(NXT). RFC 2535 didn't specify how a resolver was to interpret a + response with RCODE=0, AA=0, and both an NS and an NXT in the + authority section. Some widely deployed 2535-aware resolvers + interpret any answer with an NXT as a proof of non-existence of the + requested record. This results in unsecure delegations being + invisible to 2535-aware resolvers and violates the basic + architectural principle that DNSSEC must do no harm -- the signing of + zones must not prevent the resolution of unsecured delegations. + +2. Possible Solutions + + This section presents several solutions that were considered. + Section 3 describes the one selected. + + + + +Weiler Standards Track [Page 2] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + +2.1. Change SIG, KEY, and NXT type codes + + To avoid the problem described above, legacy (RFC2535-aware) + resolvers need to be kept from seeing unsecure referrals that include + NXT records in the authority section. The simplest way to do that is + to change the type codes for SIG, KEY, and NXT. + + The obvious drawback to this is that new resolvers will not be able + to validate zones signed with the old RRs. This problem already + exists, however, because of the changes made by DS, and resolvers + that understand the old RRs (and have compatibility issues with DS) + are far more prevalent than 2535-signed zones. + +2.2. Change a subset of type codes + + The observed problem with unsecure referrals could be addressed by + changing only the NXT type code or another subset of the type codes + that includes NXT. This has the virtue of apparent simplicity, but + it risks introducing new problems or not going far enough. It's + quite possible that more incompatibilities exist between DS and + earlier semantics. Legacy resolvers may also be confused by seeing + records they recognize (SIG and KEY) while being unable to find NXTs. + Although it may seem unnecessary to fix that which is not obviously + broken, it's far cleaner to change all of the type codes at once. + This will leave legacy resolvers and tools completely blinded to + DNSSEC -- they will see only unknown RRs. + +2.3. Replace the DO bit + + Another way to keep legacy resolvers from ever seeing DNSSEC records + with DS semantics is to have authoritative servers only send that + data to DS-aware resolvers. It's been proposed that assigning a new + EDNS0 flag bit to signal DS-awareness (tentatively called "DA"), and + having authoritative servers send DNSSEC data only in response to + queries with the DA bit set, would accomplish this. This bit would + presumably supplant the DO bit described in [RFC3225]. + + This solution is sufficient only if all 2535-aware resolvers zero out + EDNS0 flags that they don't understand. If one passed through the DA + bit unchanged, it would still see the new semantics, and it would + probably fail to see unsecure delegations. Since it's impractical to + know how every DNS implementation handles unknown EDNS0 flags, this + is not a universal solution. It could, though, be considered in + addition to changing the RR type codes. + + + + + + + +Weiler Standards Track [Page 3] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + +2.4. Increment the EDNS version + + Another possible solution is to increment the EDNS version number as + defined in [RFC2671], on the assumption that all existing + implementations will reject higher versions than they support, and + retain the DO bit as the signal for DNSSEC awareness. This approach + has not been tested. + +2.5. Do nothing + + There is a large deployed base of DNS resolvers that understand + DNSSEC as defined by the standards track RFC 2535 and [RFC2065] and, + due to under specification in those documents, interpret any answer + with an NXT as a non-existence proof. So long as that is the case, + zone owners will have a strong incentive to not sign any zones that + contain unsecure delegations, lest those delegations be invisible to + such a large installed base. This will dramatically slow DNSSEC + adoption. + + Unfortunately, without signed zones there's no clear incentive for + operators of resolvers to upgrade their software to support the new + version of DNSSEC, as defined in RFC 3658. Historical data suggests + that resolvers are rarely upgraded, and that old nameserver code + never dies. + + Rather than wait years for resolvers to be upgraded through natural + processes before signing zones with unsecure delegations, addressing + this problem with a protocol change will immediately remove the + disincentive for signing zones and allow widespread deployment of + DNSSEC. + +3. Protocol changes + + This document changes the type codes of SIG, KEY, and NXT. This + approach is the cleanest and safest of those discussed above, largely + because the behavior of resolvers that receive unknown type codes is + well understood. This approach has also received the most testing. + + To avoid operational confusion, it's also necessary to change the + mnemonics for these RRs. DNSKEY will be the replacement for KEY, + with the mnemonic indicating that these keys are not for application + use, per [RFC3445]. RRSIG (Resource Record SIGnature) will replace + SIG, and NSEC (Next SECure) will replace NXT. These new types + completely replace the old types, except that SIG(0) [RFC2931] and + TKEY [RFC2930] will continue to use SIG and KEY. + + + + + + +Weiler Standards Track [Page 4] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + + The new types will have exactly the same syntax and semantics as + specified for SIG, KEY, and NXT in RFC 2535 and RFC 3658 except for + the following: + + 1) Consistent with [RFC3597], domain names embedded in RRSIG and NSEC + RRs MUST NOT be compressed, + + 2) Embedded domain names in RRSIG and NSEC RRs are not downcased for + purposes of DNSSEC canonical form and ordering nor for equality + comparison, and + + 3) An RRSIG with a type-covered field of zero has undefined + semantics. The meaning of such a resource record may only be + defined by IETF Standards Action. + + If a resolver receives the old types, it SHOULD treat them as unknown + RRs and SHOULD NOT assign any special meaning to them or give them + any special treatment. It MUST NOT use them for DNSSEC validations + or other DNS operational decision making. For example, a resolver + MUST NOT use DNSKEYs to validate SIGs or use KEYs to validate RRSIGs. + If SIG, KEY, or NXT RRs are included in a zone, they MUST NOT receive + special treatment. As an example, if a SIG is included in a signed + zone, there MUST be an RRSIG for it. Authoritative servers may wish + to give error messages when loading zones containing SIG or NXT + records (KEY records may be included for SIG(0) or TKEY). + + As a clarification to previous documents, some positive responses, + particularly wildcard proofs and unsecure referrals, will contain + NSEC RRs. Resolvers MUST NOT treat answers with NSEC RRs as negative + answers merely because they contain an NSEC. + +4. IANA Considerations + +4.1. DNS Resource Record Types + + This document updates the IANA registry for DNS Resource Record Types + by assigning types 46, 47, and 48 to the RRSIG, NSEC, and DNSKEY RRs, + respectively. + + Types 24 and 25 (SIG and KEY) are retained for SIG(0) [RFC2931] and + TKEY [RFC2930] use only. + + Type 30 (NXT) should be marked as Obsolete. + + + + + + + + +Weiler Standards Track [Page 5] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + +4.2. DNS Security Algorithm Numbers + + To allow zone signing (DNSSEC) and transaction security mechanisms + (SIG(0) and TKEY) to use different sets of algorithms, the existing + "DNS Security Algorithm Numbers" registry is modified to include the + applicability of each algorithm. Specifically, two new columns are + added to the registry, showing whether each algorithm may be used for + zone signing, transaction security mechanisms, or both. Only + algorithms usable for zone signing may be used in DNSKEY, RRSIG, and + DS RRs. Only algorithms usable for SIG(0) and/or TSIG may be used in + SIG and KEY RRs. + + All currently defined algorithms except for Indirect (algorithm 252) + remain usable for transaction security mechanisms. Only RSA/SHA-1 + [RFC3110], DSA/SHA-1 [RFC2536], and private algorithms (types 253 and + 254) may be used for zone signing. Note that the registry does not + contain the requirement level of each algorithm, only whether or not + an algorithm may be used for the given purposes. For example, + RSA/MD5, while allowed for transaction security mechanisms, is NOT + RECOMMENDED, per [RFC3110]. + + Additionally, the presentation format algorithm mnemonics from + [RFC2535] Section 7 are added to the registry. This document assigns + RSA/SHA-1 the mnemonic RSASHA1. + + As before, assignment of new algorithms in this registry requires + IETF Standards Action. Additionally, modification of algorithm + mnemonics or applicability requires IETF Standards Action. Documents + defining a new algorithm must address the applicability of the + algorithm and should assign a presentation mnemonic to the algorithm. + +4.3. DNSKEY Flags + + Like the KEY resource record, DNSKEY contains a 16-bit flags field. + This document creates a new registry for the DNSKEY flags field. + + Initially, this registry only contains an assignment for bit 7 (the + ZONE bit). Bits 0-6 and 8-15 are available for assignment by IETF + Standards Action. + +4.4. DNSKEY Protocol Octet + + Like the KEY resource record, DNSKEY contains an eight bit protocol + field. The only defined value for this field is 3 (DNSSEC). No + other values are allowed, hence no IANA registry is needed for this + field. + + + + + +Weiler Standards Track [Page 6] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + +5. Security Considerations + + The changes introduced here do not materially affect security. The + implications of trying to use both new and legacy types together are + not well understood, and attempts to do so would probably lead to + unintended and dangerous results. + + Changing type codes will leave code paths in legacy resolvers that + are never exercised. Unexercised code paths are a frequent source of + security holes, largely because those code paths do not get frequent + scrutiny. + + Doing nothing, as described in section 2.5, will slow DNSSEC + deployment. While this does not decrease security, it also fails to + increase it. + +6. References + +6.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC2535] Eastlake, D., "Domain Name System Security Extensions", RFC + 2535, March 1999. + + [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System + (DNS)", RFC 2536, March 1999. + + [RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY RR)", + RFC 2930, September 2000. + + [RFC2931] Eastlake, D., "DNS Request and Transaction Signatures + (SIG(0)s)", RFC 2931, September 2000. + + [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain + Name System (DNS)", RFC 3110, May 2001. + + [RFC3658] Gudmundsson, O., "Delegation Signer (DS) Resource Record + (RR)", RFC 3658, December 2003. + + + + + + + + + + + +Weiler Standards Track [Page 7] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + +6.2. Informative References + + [RFC2065] Eastlake, 3rd, D. and C. Kaufman, "Domain Name System + Security Extensions", RFC 2065, January 1997. + + [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC + 2671, August 1999. + + [RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC", RFC + 3225, December 2001. + + [RFC3445] Massey, D., and S. Rose, "Limiting the Scope of the KEY + Resource Record (RR)", RFC 3445, December 2002. + + [RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record + (RR) Types", RFC 3597, September 2003. + +7. Acknowledgments + + The changes introduced here and the analysis of alternatives had many + contributors. With apologies to anyone overlooked, those include: + Michael Graff, Johan Ihren, Olaf Kolkman, Mark Kosters, Ed Lewis, + Bill Manning, Paul Vixie, and Suzanne Woolf. + + Thanks to Jakob Schlyter and Mark Andrews for identifying the + incompatibility described in section 1.2. + + In addition to the above, the author would like to thank Scott Rose, + Olafur Gudmundsson, and Sandra Murphy for their substantive comments. + +8. Author's Address + + Samuel Weiler + SPARTA, Inc. + 7075 Samuel Morse Drive + Columbia, MD 21046 + USA + + EMail: weiler@tislabs.com + + + + + + + + + + + + +Weiler Standards Track [Page 8] + +RFC 3755 Legacy Resolver Compatibility for DS May 2004 + + +9. Full Copyright Statement + + Copyright (C) The Internet Society (2004). This document is subject + to the rights, licenses and restrictions contained in BCP 78, and + except as set forth therein, the authors retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the procedures with respect to rights in RFC documents can be + found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at ietf- + ipr@ietf.org. + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + + + + +Weiler Standards Track [Page 9] + diff --git a/doc/draft/draft-ietf-dnsext-dns-name-p-s-00.txt b/doc/rfc/rfc4471.txt similarity index 60% rename from doc/draft/draft-ietf-dnsext-dns-name-p-s-00.txt rename to doc/rfc/rfc4471.txt index 438e8008a4..eb338e6b5e 100644 --- a/doc/draft/draft-ietf-dnsext-dns-name-p-s-00.txt +++ b/doc/rfc/rfc4471.txt @@ -1,40 +1,28 @@ -DNS Extensions Working Group G. Sisson -Internet-Draft B. Laurie -Expires: January 11, 2006 Nominet - July 10, 2005 + + + + + + +Network Working Group G. Sisson +Request for Comments: 4471 B. Laurie +Category: Experimental Nominet + September 2006 Derivation of DNS Name Predecessor and Successor - draft-ietf-dnsext-dns-name-p-s-00 -Status of this Memo - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. +Status of This Memo - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on January 11, 2006. + This memo defines an Experimental Protocol for the Internet + community. It does not specify an Internet standard of any kind. + Discussion and suggestions for improvement are requested. + Distribution of this memo is unlimited. Copyright Notice - Copyright (C) The Internet Society (2005). + Copyright (C) The Internet Society (2006). Abstract @@ -42,105 +30,90 @@ Abstract ordered predecessor and successor of a DNS name. These methods may be used for dynamic NSEC resource record synthesis, enabling security-aware name servers to provide authenticated denial of - existence without disclosing other owner names in a DNSSEC-secured + existence without disclosing other owner names in a DNSSEC secured zone. - - - - -Sisson & Laurie Expires January 11, 2006 [Page 1] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 - 3. Absolute Method . . . . . . . . . . . . . . . . . . . . . . . 4 - 3.1. Derivation of DNS Name Predecessor . . . . . . . . . . . . 4 - 3.2. Derivation of DNS Name Successor . . . . . . . . . . . . . 4 - 4. Modified Method . . . . . . . . . . . . . . . . . . . . . . . 5 - 4.1. Derivation of DNS Name Predecessor . . . . . . . . . . . . 6 - 4.2. Derivation of DNS Name Successor . . . . . . . . . . . . . 6 - 5. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 5.1. Case Considerations . . . . . . . . . . . . . . . . . . . 7 - 5.2. Choice of Range . . . . . . . . . . . . . . . . . . . . . 7 - 5.3. Wild Card Considerations . . . . . . . . . . . . . . . . . 8 - 5.4. Possible Modifications . . . . . . . . . . . . . . . . . . 8 - 5.4.1. Restriction of Effective Maximum DNS Name Length . . . 8 - 5.4.2. Use of Modified Method With Zones Containing - SRV RRs . . . . . . . . . . . . . . . . . . . . . . . 9 - 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 6.1. Examples of Immediate Predecessors Using Absolute - Method . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 6.2. Examples of Immediate Successors Using Absolute Method . . 13 - 6.3. Examples of Predecessors Using Modified Method . . . . . . 19 - 6.4. Examples of Successors Using Modified Method . . . . . . . 20 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 21 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 - 10.1. Normative References . . . . . . . . . . . . . . . . . . . 22 - 10.2. Informative References . . . . . . . . . . . . . . . . . . 22 - 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 - Appendix A. Change History . . . . . . . . . . . . . . . . . . . 22 - A.1. Changes from sisson-02 to ietf-00 . . . . . . . . . . . . 22 - A.2. Changes from sisson-01 to sisson-02 . . . . . . . . . . . 23 - A.3. Changes from sisson-00 to sisson-01 . . . . . . . . . . . 23 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 - Intellectual Property and Copyright Statements . . . . . . . . . . 25 + 1. Introduction ....................................................2 + 2. Notational Conventions ..........................................3 + 3. Derivations .....................................................3 + 3.1. Absolute Method ............................................3 + 3.1.1. Derivation of DNS Name Predecessor ..................3 + 3.1.2. Derivation of DNS Name Successor ....................4 + 3.2. Modified Method ............................................4 + 3.2.1. Derivation of DNS Name Predecessor ..................5 + 3.2.2. Derivation of DNS Name Successor ....................6 + 4. Notes ...........................................................6 + 4.1. Test for Existence .........................................6 + 4.2. Case Considerations ........................................7 + 4.3. Choice of Range ............................................7 + 4.4. Wild Card Considerations ...................................8 + 4.5. Possible Modifications .....................................8 + 4.5.1. Restriction of Effective Maximum DNS Name Length ....8 + 4.5.2. Use of Modified Method with Zones Containing - - - - - - - - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 2] +Sisson & Laurie Experimental [Page 1] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 + SRV RRs .............................................8 + 5. Examples ........................................................9 + 5.1. Examples of Immediate Predecessors Using Absolute Method ..10 + 5.2. Examples of Immediate Successors Using Absolute Method ....14 + 5.3. Examples of Predecessors Using Modified Method ............19 + 5.4. Examples of Successors Using Modified Method ..............20 + 6. Security Considerations ........................................21 + 7. Acknowledgements ...............................................21 + 8. References .....................................................21 + 8.1. Normative References ......................................21 + 8.2. Informative References ....................................22 + 1. Introduction One of the proposals for avoiding the exposure of zone information during the deployment DNSSEC is dynamic NSEC resource record (RR) - synthesis. This technique is described in [I-D.ietf-dnsext-dnssec- - trans] and [I-D.ietf-dnsext-dnssec-online-signing], and involves the - generation of NSEC RRs that just span the query name for non-existent - owner names. In order to do this, the DNS names which would occur - just prior to and just following a given query name must be - calculated in real time, as maintaining a list of all possible owner - names that might occur in a zone would be impracticable. + synthesis. This technique is described in [DNSSEC-TRANS] and + [RFC4470], and involves the generation of NSEC RRs that just span the + query name for non-existent owner names. In order to do this, the + DNS names that would occur just prior to and just following a given + query name must be calculated in real time, as maintaining a list of + all possible owner names that might occur in a zone would be + impracticable. Section 6.1 of [RFC4034] defines canonical DNS name order. This document does not amend or modify this definition. However, the - derivation of immediate predecessor and successor, while trivial, is - non-obvious. Accordingly, several methods are described here as an - aid to implementors and a reference to other interested parties. + derivation of immediate predecessor and successor, although trivial, + is non-obvious. Accordingly, several methods are described here as + an aid to implementors and a reference to other interested parties. This document describes two methods: - 1. An ``absolute method'', which returns the immediate predecessor - or successor of a domain name such that no valid DNS name could + 1. An "absolute method", which returns the immediate predecessor or + successor of a domain name such that no valid DNS name could exist between that DNS name and the predecessor or successor. - 2. A ``modified method'', which returns a predecessor and successor - which are more economical in size and computation. This method - is restricted to use with zones consisting only of single-label - owner names where a maximum-length owner name would not result in - a DNS name exceeding the maximum DNS name length. This is, - however, the type of zone for which the technique of online- - signing is most likely to be used. + 2. A "modified method", which returns a predecessor and successor + that are more economical in size and computation. This method is + restricted to use with zones consisting exclusively of owner + names that contain no more than one label more than the owner + name of the apex, where the longest possible owner name (i.e., + one with a maximum length left-most label) would not exceed the + maximum DNS name length. This is, however, the type of zone for + which the technique of online signing is most likely to be used. + + + + + + + +Sisson & Laurie Experimental [Page 2] + +RFC 4471 DNS Name Predecessor and Successor September 2006 2. Notational Conventions @@ -156,104 +129,106 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 P'(N): Predecessor to N (modified method). - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 3] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - S'(N): Successor to N (modified method). - -3. Absolute Method +3. Derivations These derivations assume that all uppercase US-ASCII letters in N have already been replaced by their corresponding lowercase equivalents. Unless otherwise specified, processing stops after the first step in which a condition is met. -3.1. Derivation of DNS Name Predecessor + The derivations make reference to maximum label length and maximum + DNS name length; these are defined in Section 3.1 of [RFC1034] to be + 63 and 255 octets, respectively. + +3.1. Absolute Method + +3.1.1. Derivation of DNS Name Predecessor To derive P(N): 1. If N is the same as the owner name of the zone apex, prepend N repeatedly with labels of the maximum length possible consisting - of octets of the maximum sort value (e.g. 0xff) until N is the - maximum length possible; otherwise continue to the next step. + of octets of the maximum sort value (e.g., 0xff) until N is the + maximum length possible; otherwise proceed to the next step. 2. If the least significant (left-most) label of N consists of a - single octet of the minimum sort value (e.g. 0x00), remove that - label; otherwise continue to the next step. + single octet of the minimum sort value (e.g., 0x00), remove that + label; otherwise proceed to the next step. 3. If the least significant (right-most) octet in the least significant (left-most) label of N is the minimum sort value, - remove the least significant octet and continue with step 5. + remove the least significant octet and proceed to step 5. - 4. Decrement the value of the least significant (right-most) octet, - skipping any values that correspond to uppercase US-ASCII - letters, and then append the label with as many octets as - possible of the maximum sort value. Continue to the next step. + 4. Decrement the value of the least significant (right-most) octet + of the least significant (left-most) label, skipping any values + that correspond to uppercase US-ASCII letters, and then append + + + +Sisson & Laurie Experimental [Page 3] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + + the least significant (left-most) label with as many octets as + possible of the maximum sort value. Proceed to the next step. 5. Prepend N repeatedly with labels of as long a length as possible consisting of octets of the maximum sort value until N is the maximum length possible. -3.2. Derivation of DNS Name Successor +3.1.2. Derivation of DNS Name Successor To derive S(N): 1. If N is two or more octets shorter than the maximum DNS name length, prepend N with a label containing a single octet of the - minimum sort value (e.g. 0x00); otherwise continue to the next + minimum sort value (e.g., 0x00); otherwise proceed to the next step. - 2. If N is one or more octets shorter than the maximum DNS name - length and the least significant (left-most) label is one or more - octets shorter than the maximum label length, append an octet of - - - -Sisson & Laurie Expires January 11, 2006 [Page 4] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - - the minimum sort value to the least significant label; otherwise - continue to the next step. + 2. If N is one octet shorter than the maximum DNS name length and + the least significant (left-most) label is one or more octets + shorter than the maximum label length, append an octet of the + minimum sort value to the least significant label; otherwise + proceed to the next step. 3. Increment the value of the least significant (right-most) octet in the least significant (left-most) label that is less than the - maximum sort value (e.g. 0xff), skipping any values that + maximum sort value (e.g., 0xff), skipping any values that correspond to uppercase US-ASCII letters, and then remove any octets to the right of that one. If all octets in the label are - the maximum sort value, then continue to the next step. + the maximum sort value, then proceed to the next step. - 4. Remove the least significant (left-most) label. If N is now the - same as the owner name of the zone apex, do nothing. (This will - occur only if N is the maximum possible name in canonical DNS - name order, and thus has wrapped to the owner name of zone apex.) - Otherwise repeat starting at step 2. + 4. Remove the least significant (left-most) label. Unless N is now + the same as the owner name of the zone apex (this will occur only + if N was the maximum possible name in canonical DNS name order, + and thus has wrapped to the owner name of zone apex), repeat + starting at step 2. - -4. Modified Method +3.2. Modified Method This method is for use with zones consisting only of single-label owner names where an owner name consisting of label of maximum length - would not result in a DNS name which exceeded the maximum DNS name + would not result in a DNS name that exceeded the maximum DNS name length. This method is computationally simpler and returns values - which are more economical in size than the absolute method. It + that are more economical in size than the absolute method. It differs from the absolute method detailed above in the following ways: 1. Step 1 of the derivation P(N) has been omitted as the existence of the owner name of the zone apex never requires denial. - 2. A new step 1 has been introduced which removes unnecessary - labels. + + + +Sisson & Laurie Experimental [Page 4] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + + 2. A new step 1 has been introduced that removes unnecessary labels. 3. Step 4 of the derivation P(N) has been omitted as it is only necessary for zones containing owner names consisting of more @@ -271,87 +246,110 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 assumption of this method that no DNS name in the zone can exceed the maximum DNS name length. - - -Sisson & Laurie Expires January 11, 2006 [Page 5] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - - These derivations assume that all uppercase US-ASCII letters in N - have already been replaced by their corresponding lowercase - equivalents. Unless otherwise specified, processing stops after the - first step in which a condition is met. - -4.1. Derivation of DNS Name Predecessor +3.2.1. Derivation of DNS Name Predecessor To derive P'(N): - 1. If N has more labels than the number of labels in the owner name - of the apex + 1, repeatedly remove the least significant (left- - most) label until N has no more labels than the number of labels - in the owner name of the apex + 1; otherwise continue to next - step. + 1. If N is two or more labels longer than the owner name of the + apex, repeatedly remove the least significant (left-most) label + until N is only one label longer than the owner name of the apex; + otherwise proceed to the next step. 2. If the least significant (left-most) label of N consists of a - single octet of the minimum sort value (e.g. 0x00), remove that - label; otherwise continue to the next step. + single octet of the minimum sort value (e.g., 0x00), remove that + label; otherwise proceed to the next step. (If this condition is + met, P'(N) is the owner name of the apex.) 3. If the least significant (right-most) octet in the least significant (left-most) label of N is the minimum sort value, remove the least significant octet. 4. Decrement the value of the least significant (right-most) octet, - skipping any values which correspond to uppercase US-ASCII + skipping any values that correspond to uppercase US-ASCII letters, and then append the label with as many octets as possible of the maximum sort value. -4.2. Derivation of DNS Name Successor + + + + + + + + + + +Sisson & Laurie Experimental [Page 5] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + +3.2.2. Derivation of DNS Name Successor To derive S'(N): - 1. If N has more labels than the number of labels in the owner name - of the apex + 1, repeatedly remove the least significant (left- - most) label until N has no more labels than the number of labels - in the owner name of the apex + 1. Continue to next step. + 1. If N is two or more labels longer than the owner name of the + apex, repeatedly remove the least significant (left-most) label + until N is only one label longer than the owner name of the apex. + Proceed to the next step. 2. If the least significant (left-most) label of N is one or more octets shorter than the maximum label length, append an octet of the minimum sort value to the least significant label; otherwise - continue to the next step. + proceed to the next step. 3. Increment the value of the least significant (right-most) octet in the least significant (left-most) label that is less than the - maximum sort value (e.g. 0xff), skipping any values which + maximum sort value (e.g., 0xff), skipping any values that correspond to uppercase US-ASCII letters, and then remove any octets to the right of that one. If all octets in the label are - the maximum sort value, then continue to the next step. - - - -Sisson & Laurie Expires January 11, 2006 [Page 6] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - + the maximum sort value, then proceed to the next step. 4. Remove the least significant (left-most) label. (This will occur only if the least significant label is the maximum label length and consists entirely of octets of the maximum sort value, and thus has wrapped to the owner name of the zone apex.) +4. Notes -5. Notes +4.1. Test for Existence -5.1. Case Considerations + Before using the result of P(N) or P'(N) as the owner name of an NSEC + RR in a DNS response, a name server should test to see whether the + name exists. If it does, either a standard non-synthesised NSEC RR + should be used, or the synthesised NSEC RR should reflect the RRset + types that exist at the NSEC RR's owner name in the Type Bit Map + field as specified by Section 4.1.2 of [RFC4034]. Implementors will + likely find it simpler to use a non-synthesised NSEC RR. For further + details, see Section 2 of [RFC4470]. + + + + + + + + + + + + + +Sisson & Laurie Experimental [Page 6] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + +4.2. Case Considerations Section 3.5 of [RFC1034] specifies that "while upper and lower case - letters are allowed in [DNS] names, no significance is attached to - the case". Additionally, Section 6.1 of [RFC4034] states that when + letters are allowed in names, no significance is attached to the + case". Additionally, Section 6.1 of [RFC4034] states that when determining canonical DNS name order, "uppercase US-ASCII letters are treated as if they were lowercase US-ASCII letters". Consequently, values corresponding to US-ASCII uppercase letters must be skipped when decrementing and incrementing octets in the derivations - described in Section 3.1 and Section 3.2. + described in Section 3. The following pseudo-code is illustrative: @@ -369,98 +367,100 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 else octet++; -5.2. Choice of Range +4.3. Choice of Range [RFC2181] makes the clarification that "any binary string whatever - can be used as the label of any resource record". Consequently the + can be used as the label of any resource record". Consequently, the minimum sort value may be set as 0x00 and the maximum sort value as - 0xff, and the range of possible values will be any DNS name which + 0xff, and the range of possible values will be any DNS name that contains octets of any value other than those corresponding to uppercase US-ASCII letters. However, if all owner names in a zone are in the letter-digit-hyphen, or LDH, format specified in [RFC1034], it may be desirable to restrict the range of possible values to DNS names containing only - LDH values. This has the effect of: - - - -Sisson & Laurie Expires January 11, 2006 [Page 7] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - + LDH values. This has the effect of 1. making the output of tools such as `dig' and `nslookup' less - subject to confusion; + subject to confusion, 2. minimising the impact that NSEC RRs containing DNS names with non-LDH values (or non-printable values) might have on faulty DNS - resolver implementations; and + resolver implementations, and - 3. preventing the possibility of results which are wildcard DNS - names (see Section 5.3). + + + +Sisson & Laurie Experimental [Page 7] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + + 3. preventing the possibility of results that are wildcard DNS names + (see Section 4.4). This may be accomplished by using a minimum sort value of 0x1f (US- ASCII character `-') and a maximum sort value of 0x7a (US-ASCII character lowercase `z'), and then skipping non-LDH, non-lowercase values when incrementing or decrementing octets. -5.3. Wild Card Considerations +4.4. Wild Card Considerations Neither derivation avoids the possibility that the result may be a - DNS name containing a wildcard label, i.e. a label containing a + DNS name containing a wildcard label, i.e., a label containing a single octet with the value 0x2a (US-ASCII character `*'). With additional tests, wildcard DNS names may be explicitly avoided; alternatively, if the range of octet values can be restricted to those corresponding to letter-digit-hyphen, or LDH, characters (see - Section 5.2), such DNS names will not occur. + Section 4.3), such DNS names will not occur. - Note that it is improbable that a result which is a wildcard DNS name + Note that it is improbable that a result that is a wildcard DNS name will occur unintentionally; even if one does occur either as the owner name of, or in the RDATA of an NSEC RR, it is treated as a literal DNS name with no special meaning. -5.4. Possible Modifications +4.5. Possible Modifications -5.4.1. Restriction of Effective Maximum DNS Name Length +4.5.1. Restriction of Effective Maximum DNS Name Length [RFC1034] specifies that "the total number of octets that represent a - [DNS] name (i.e., the sum of all label octets and label lengths) is - limited to 255", including the null (zero-length) label which - represents the root. For the purpose of deriving predecessors and - successors during NSEC RR synthesis, the maximum DNS name length may - be effectively restricted to the length of the longest DNS name in - the zone. This will minimise the size of responses containing - synthesised NSEC RRs but, especially in the case of the modified - method, may result in some additional computational complexity. + name (i.e., the sum of all label octets and label lengths) is limited + to 255", including the null (zero-length) label that represents the + root. For the purpose of deriving predecessors and successors during + NSEC RR synthesis, the maximum DNS name length may be effectively + restricted to the length of the longest DNS name in the zone. This + will minimise the size of responses containing synthesised NSEC RRs + but, especially in the case of the modified method, may result in + some additional computational complexity. Note that this modification will have the effect of revealing information about the longest name in the zone. Moreover, when the - contents of the zone changes, e.g. during dynamic updates and zone + contents of the zone changes, e.g., during dynamic updates and zone transfers, care must be taken to ensure that the effective maximum - - - -Sisson & Laurie Expires January 11, 2006 [Page 8] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - DNS name length agrees with the new contents. -5.4.2. Use of Modified Method With Zones Containing SRV RRs +4.5.2. Use of Modified Method with Zones Containing SRV RRs - Normally the modified method cannot be used in zones that contain - SRV RRs [RFC2782], as SRV RRs have owner names which contain multiple - labels. However the use of SRV RRs can be accommodated by various - techniques. There are at least four possible ways to do this: + Normally, the modified method cannot be used in zones that contain + Service Record (SRV) RRs [RFC2782], as SRV RRs have owner names that + contain multiple labels. However, the use of SRV RRs can be + + + +Sisson & Laurie Experimental [Page 8] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + + accommodated by various techniques. There are at least four possible + ways to do this: 1. Use conventional NSEC RRs for the region of the zone that contains first-level labels beginning with the underscore (`_') character. For the purposes of generating these NSEC RRs, the existence of (possibly fictional) ownernames `9{63}' and `a' could be assumed, providing a lower and upper bound for this - region. Then all queries where the QNAME doesn't exist but + region. Then all queries where the QNAME does not exist but contains a first-level label beginning with an underscore could be handled using the normal DNSSEC protocol. @@ -473,7 +473,7 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 2. The absolute method could be used for synthesising NSEC RRs for all queries where the QNAME contains a leading underscore. - However this re-introduces the susceptibility of the absolute + However, this re-introduces the susceptibility of the absolute method to denial of service activity, as an attacker could send queries for an effectively inexhaustible supply of domain names beginning with a leading underscore. @@ -482,42 +482,42 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 NSEC RRs for all queries where the QNAME contains a leading underscore. This variant would assume that all predecessors and successors to queries where the QNAME contains a leading - underscore may consist of two lablels rather than only one. This + underscore may consist of two labels rather than only one. This introduces a little additional complexity without incurring the full increase in response size and computational complexity as the absolute method. - 4. Finally, a variant the modified method which assumes that all + 4. Finally, a variant of the modified method that assumes that all owner names in the zone consist of one or two labels could be - used. However this negates much of the reduction in response + used. However, this negates much of the reduction in response size of the modified method and may be nearly as computationally complex as the absolute method. +5. Examples + + In the following examples, + + the owner name of the zone apex is "example.com.", -Sisson & Laurie Expires January 11, 2006 [Page 9] + +Sisson & Laurie Experimental [Page 9] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 -6. Examples - - In the following examples: - - the owner name of the zone apex is "example.com."; - the range of octet values is 0x00 - 0xff excluding values - corresponding to uppercase US-ASCII letters; and + corresponding to uppercase US-ASCII letters, and non-printable octet values are expressed as three-digit decimal numbers preceded by a backslash (as specified in Section 5.1 of [RFC1035]). -6.1. Examples of Immediate Predecessors Using Absolute Method +5.1. Examples of Immediate Predecessors Using Absolute Method - Example of typical case: + Example of a typical case: P(foo.example.com.) = @@ -548,21 +548,22 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 where {n} represents the number of repetitions of an octet. - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 10] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - Example where least significant (left-most) label of DNS name consists of a single octet of the minimum sort value: P(\000.foo.example.com.) = foo.example.com. + + + + + + +Sisson & Laurie Experimental [Page 10] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + Example where least significant (right-most) octet of least significant (left-most) label has the minimum sort value: @@ -609,12 +610,17 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 11] + + + + + +Sisson & Laurie Experimental [Page 11] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 - Example where DNS name contains an octet which must be decremented by + Example where DNS name contains an octet that must be decremented by skipping values corresponding to US-ASCII uppercase letters: P(fo\[.example.com.) = @@ -665,9 +671,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 12] +Sisson & Laurie Experimental [Page 12] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name is the owner name of the zone apex, and @@ -702,30 +708,36 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 \255{49}.\255{63}.\255{63}.\255{63}.example.com. -6.2. Examples of Immediate Successors Using Absolute Method + + + + + + + + + + + + + + + + + + + +Sisson & Laurie Experimental [Page 13] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + +5.2. Examples of Immediate Successors Using Absolute Method Example of typical case: S(foo.example.com.) = \000.foo.example.com. - - - - - - - - - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 13] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - Example where DNS name is one octet short of the maximum DNS name length: @@ -771,15 +783,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 - - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 14] +Sisson & Laurie Experimental [Page 14] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name is the maximum DNS name length: @@ -833,9 +839,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 15] +Sisson & Laurie Experimental [Page 15] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name is the maximum DNS name length and the least @@ -889,14 +895,14 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 16] +Sisson & Laurie Experimental [Page 16] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name is the maximum DNS name length and the eight - least significant (right-most) octets of the least significant (left- - most) label have the maximum sort value: + least significant (right-most) octets of the least significant + (left-most) label have the maximum sort value: N = foooooooooooooooooooooooooooooooooooooooo\255 \255\255\255\255\255\255\255.ooooooooooooooooooo @@ -945,13 +951,13 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 17] +Sisson & Laurie Experimental [Page 17] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name is the maximum DNS name length and contains an - octet which must be incremented by skipping values corresponding to + octet that must be incremented by skipping values corresponding to US-ASCII uppercase letters: N = fooooooooooooooooooooooooooooooooooooooooooooooo @@ -1001,9 +1007,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 18] +Sisson & Laurie Experimental [Page 18] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name has the maximum possible sort order in the @@ -1037,9 +1043,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 S(N) = example.com. -6.3. Examples of Predecessors Using Modified Method +5.3. Examples of Predecessors Using Modified Method - Example of typical case: + Example of a typical case: P'(foo.example.com.) = @@ -1057,9 +1063,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 -Sisson & Laurie Expires January 11, 2006 [Page 19] +Sisson & Laurie Experimental [Page 19] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 Example where DNS name contains more labels than DNS names in the @@ -1094,9 +1100,9 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 \255{63}.example.com. -6.4. Examples of Successors Using Modified Method +5.4. Examples of Successors Using Modified Method - Example of typical case: + Example of a typical case: S'(foo.example.com.) = foo\000.example.com. @@ -1106,22 +1112,18 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 S'(bar.foo.example.com.) = foo\000.example.com. - - - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 20] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - Example where least significant (left-most) label has the maximum sort value, and consequently wraps to the owner name of the zone apex: + + + +Sisson & Laurie Experimental [Page 20] + +RFC 4471 DNS Name Predecessor and Successor September 2006 + + N = \255\255\255\255\255\255\255\255\255\255\255\255 \255\255\255\255\255\255\255\255\255\255\255\255 \255\255\255\255\255\255\255\255\255\255\255\255 @@ -1135,156 +1137,58 @@ Internet-Draft DNS Name Predecessor and Successor July 2005 S'(N) = example.com. - -7. Security Considerations +6. Security Considerations The derivation of some predecessors/successors requires the testing - of more conditions than others. Consequently the effectiveness of a + of more conditions than others. Consequently, the effectiveness of a denial-of-service attack may be enhanced by sending queries that require more conditions to be tested. The modified method involves the testing of fewer conditions than the absolute method and consequently is somewhat less susceptible to this exposure. +7. Acknowledgements -8. IANA Considerations + The authors would like to thank Sam Weiler, Olaf Kolkman, Olafur + Gudmundsson, and Niall O'Reilly for their review and input. - This document has no IANA actions. +8. References - Note to RFC Editor: This section is included to make it clear during - pre-publication review that this document has no IANA actions. It - may therefore be removed should it be published as an RFC. +8.1. Normative References + [RFC1034] Mockapetris, P., "Domain names - concepts and + facilities", STD 13, RFC 1034, November 1987. -9. Acknowledgments + [RFC1035] Mockapetris, P., "Domain names - implementation and + specification", STD 13, RFC 1035, November 1987. - The authors would like to thank Olaf Kolkman, Olafur Gudmundsson and - Niall O'Reilly for their review and input. + [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS + Specification", RFC 2181, July 1997. + [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR + for specifying the location of services (DNS SRV)", + RFC 2782, February 2000. -10. References + [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and + S. Rose, "Resource Records for the DNS Security + Extensions", RFC 4034, March 2005. - - - -Sisson & Laurie Expires January 11, 2006 [Page 21] +Sisson & Laurie Experimental [Page 21] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 -10.1 Normative References +8.2. Informative References - [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", - STD 13, RFC 1034, November 1987. - - [RFC1035] Mockapetris, P., "Domain names - implementation and - specification", STD 13, RFC 1035, November 1987. - - [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS - Specification", RFC 2181, July 1997. - - [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for - specifying the location of services (DNS SRV)", RFC 2782, - February 2000. - - [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. - Rose, "Resource Records for the DNS Security Extensions", - RFC 4034, March 2005. - -10.2 Informative References - - [I-D.ietf-dnsext-dnssec-online-signing] - Ihren, J. and S. Weiler, "Minimally Covering NSEC Records - and DNSSEC On-line Signing", - draft-ietf-dnsext-dnssec-online-signing-00 (work in - progress), May 2005. - - [I-D.ietf-dnsext-dnssec-trans] - Arends, R., Koch, P., and J. Schlyter, "Evaluating DNSSEC - Transition Mechanisms", - draft-ietf-dnsext-dnssec-trans-02 (work in progress), - February 2005. - - -Appendix A. Change History - -A.1. Changes from sisson-02 to ietf-00 - - o Added notes on use of SRV RRs with modified method. - - o Changed reference from weiler-dnssec-online-signing to ietf- - dnsext-dnssec-online-signing. - - o Changed reference from ietf-dnsext-dnssec-records to RFC 4034. - - o Miscellaneous minor changes to text. - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 22] - -Internet-Draft DNS Name Predecessor and Successor July 2005 - - -A.2. Changes from sisson-01 to sisson-02 - - o Added modified version of derivation (with supporting examples). - - o Introduced notational conventions N, P(N), S(N), P'(N) and S'(N). - - o Added clarification to derivations about when processing stops. - - o Miscellaneous minor changes to text. - -A.3. Changes from sisson-00 to sisson-01 - - o Split step 3 of derivation of DNS name predecessor into two - distinct steps for clarity. - - o Added clarifying text and examples related to the requirement to - avoid uppercase characters when decrementing or incrementing - octets. - - o Added optimisation using restriction of effective maximum DNS name - length. - - o Changed examples to use decimal rather than octal notation as per - [RFC1035]. - - o Corrected DNS name length of some examples. - - o Added reference to weiler-dnssec-online-signing. - - o Miscellaneous minor changes to text. - - - - - - - - - - - - - - - - - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 23] - -Internet-Draft DNS Name Predecessor and Successor July 2005 + [RFC4470] Weiler, S. and J. Ihren, "Minimally Covering NSEC + Records and DNSSEC On-line Signing", RFC 4470, April + 2006. + [DNSSEC-TRANS] Arends, R., Koch, P., and J. Schlyter, "Evaluating + DNSSEC Transition Mechanisms", Work in Progress, + February 2005. Authors' Addresses @@ -1296,8 +1200,8 @@ Authors' Addresses OX4 6LB GB - Phone: +44 1865 332339 - Email: geoff@nominet.org.uk + Phone: +44 1865 332211 + EMail: geoff@nominet.org.uk Ben Laurie @@ -1308,7 +1212,7 @@ Authors' Addresses GB Phone: +44 20 8735 0686 - Email: ben@algroup.co.uk + EMail: ben@algroup.co.uk @@ -1327,22 +1231,28 @@ Authors' Addresses - - - - - - - - - - -Sisson & Laurie Expires January 11, 2006 [Page 24] +Sisson & Laurie Experimental [Page 22] -Internet-Draft DNS Name Predecessor and Successor July 2005 +RFC 4471 DNS Name Predecessor and Successor September 2006 -Intellectual Property Statement +Full Copyright Statement + + Copyright (C) The Internet Society (2006). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to @@ -1366,32 +1276,16 @@ Intellectual Property Statement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. +Acknowledgement -Disclaimer of Validity - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Copyright Statement - - Copyright (C) The Internet Society (2005). This document is subject - to the rights, licenses and restrictions contained in BCP 78, and - except as set forth therein, the authors retain all their rights. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. + Funding for the RFC Editor function is provided by the IETF + Administrative Support Activity (IASA). -Sisson & Laurie Expires January 11, 2006 [Page 25] + + + +Sisson & Laurie Experimental [Page 23] diff --git a/doc/draft/draft-ietf-dnsext-dnssec-experiments-03.txt b/doc/rfc/rfc4955.txt similarity index 54% rename from doc/draft/draft-ietf-dnsext-dnssec-experiments-03.txt rename to doc/rfc/rfc4955.txt index c8db70916f..2d2eb84e0f 100644 --- a/doc/draft/draft-ietf-dnsext-dnssec-experiments-03.txt +++ b/doc/rfc/rfc4955.txt @@ -1,85 +1,48 @@ -DNSEXT D. Blacka -Internet-Draft VeriSign, Inc. -Intended status: Standards Track April 7, 2006 -Expires: October 9, 2006 - DNSSEC Experiments - draft-ietf-dnsext-dnssec-experiments-03 -Status of this Memo +Network Working Group D. Blacka +Request for Comments: 4955 VeriSign, Inc. +Category: Standards Track July 2007 - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. + DNS Security (DNSSEC) Experiments - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." +Status of This Memo - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on October 9, 2006. + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. Copyright Notice - Copyright (C) The Internet Society (2006). - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 1] - -Internet-Draft DNSSEC Experiments April 2006 - + Copyright (C) The IETF Trust (2007). Abstract This document describes a methodology for deploying alternate, non- - backwards-compatible, DNSSEC methodologies in an experimental fashion - without disrupting the deployment of standard DNSSEC. - + backwards-compatible, DNS Security (DNSSEC) methodologies in an + experimental fashion without disrupting the deployment of standard + DNSSEC. Table of Contents - 1. Definitions and Terminology . . . . . . . . . . . . . . . . . 3 - 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3. Experiments . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 4. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 5. Defining an Experiment . . . . . . . . . . . . . . . . . . . . 8 - 6. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7. Use in Non-Experiments . . . . . . . . . . . . . . . . . . . . 10 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 13 - 10.2. Informative References . . . . . . . . . . . . . . . . . 13 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14 - Intellectual Property and Copyright Statements . . . . . . . . . . 15 + 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 + 2. Definitions and Terminology . . . . . . . . . . . . . . . . . . 2 + 3. Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . 2 + 4. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 5. Defining an Experiment . . . . . . . . . . . . . . . . . . . . 4 + 6. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 5 + 7. Use in Non-Experiments . . . . . . . . . . . . . . . . . . . . 5 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 + 9.2. Informative References . . . . . . . . . . . . . . . . . . 6 @@ -92,84 +55,12 @@ Table of Contents - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 2] +Blacka Standards Track [Page 1] -Internet-Draft DNSSEC Experiments April 2006 +RFC 4955 DNS Security (DNSSEC) Experiments July 2007 -1. Definitions and Terminology - - Throughout this document, familiarity with the DNS system (RFC 1035 - [5]) and the DNS security extensions ([2], [3], and [4] is assumed. - - The key words "MUST, "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY, and "OPTIONAL" in this - document are to be interpreted as described in RFC 2119 [1]. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 3] - -Internet-Draft DNSSEC Experiments April 2006 - - -2. Overview +1. Overview Historically, experimentation with DNSSEC alternatives has been a problematic endeavor. There has typically been a desire to both @@ -180,50 +71,20 @@ Internet-Draft DNSSEC Experiments April 2006 aware resolvers. This document describes a standard methodology for setting up DNSSEC - experiments. This methodology addresses the issue of co-existence + experiments. This methodology addresses the issue of coexistence with standard DNSSEC and DNS by using unknown algorithm identifiers to hide the experimental DNSSEC protocol modifications from standard security-aware resolvers. +2. Definitions and Terminology + Throughout this document, familiarity with the DNS system (RFC 1035 + [5]) and the DNS security extensions (RFC 4033 [2], RFC 4034 [3], and + RFC 4035 [4]) is assumed. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 4] - -Internet-Draft DNSSEC Experiments April 2006 - + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in RFC 2119 [1]. 3. Experiments @@ -250,35 +111,9 @@ Internet-Draft DNSSEC Experiments April 2006 - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 5] +Blacka Standards Track [Page 2] -Internet-Draft DNSSEC Experiments April 2006 +RFC 4955 DNS Security (DNSSEC) Experiments July 2007 4. Method @@ -290,7 +125,7 @@ Internet-Draft DNSSEC Experiments April 2006 This technique works because of the way DNSSEC-compliant validators are expected to work in the presence of a DS set with only unknown - algorithm identifiers. From [4], Section 5.2: + algorithm identifiers. From RFC 4035 [4], Section 5.2: If the validator does not support any of the algorithms listed in an authenticated DS RRset, then the resolver has no supported @@ -306,21 +141,36 @@ Internet-Draft DNSSEC Experiments April 2006 verify the authentication path to the child zone. In this case, the resolver SHOULD treat the child zone as if it were unsigned. - While this behavior isn't strictly mandatory (as marked by MUST), it - is likely that a validator would implement this behavior, or, more to - the point, it would handle this situation in a safe way (see below - (Section 6).) + Although this behavior isn't strictly mandatory (as marked by MUST), + it is unlikely for a validator to implement a substantially different + behavior. Essentially, if the validator does not have a usable chain + of trust to a child zone, then it can only do one of two things: + treat responses from the zone as insecure (the recommended behavior), + or treat the responses as bogus. If the validator chooses the + latter, this will both violate the expectation of the zone owner and + defeat the purpose of the above rule. However, with local policy, it + is within the right of a validator to refuse to trust certain zones + based on any criteria, including the use of unknown signing + algorithms. Because we are talking about experiments, it is RECOMMENDED that - private algorithm numbers be used (see [3], appendix A.1.1. Note - that secure handling of private algorithms requires special handing - by the validator logic. See [6] for further details.) Normally, - instead of actually inventing new signing algorithms, the recommended - path is to create alternate algorithm identifiers that are aliases - for the existing, known algorithms. While, strictly speaking, it is - only necessary to create an alternate identifier for the mandatory - algorithms, it is suggested that all optional defined algorithms be - aliased as well. + private algorithm numbers be used (see RFC 4034 [3], Appendix A.1.1. + Note that secure handling of private algorithms requires special + handing by the validator logic. See "Clarifications and + Implementation Notes for DNSSECbis" [6] for further details.) + Normally, instead of actually inventing new signing algorithms, the + recommended path is to create alternate algorithm identifiers that + are aliases for the existing, known algorithms. While, strictly + speaking, it is only necessary to create an alternate identifier for + the mandatory algorithms, it is suggested that all optional defined + algorithms be aliased as well. + + + +Blacka Standards Track [Page 3] + +RFC 4955 DNS Security (DNSSEC) Experiments July 2007 + It is RECOMMENDED that for a particular DNSSEC experiment, a particular domain name base is chosen for all new algorithms, then @@ -329,14 +179,6 @@ Internet-Draft DNSSEC Experiments April 2006 chosen. Then, aliases for algorithms 3 (DSA) and 5 (RSASHA1) are defined to be "3.dnssec-experiment-a.example.com" and "5.dnssec-experiment-a.example.com". However, any unique identifier - - - -Blacka Expires October 9, 2006 [Page 6] - -Internet-Draft DNSSEC Experiments April 2006 - - will suffice. Using this method, resolvers (or, more specifically, DNSSEC @@ -352,51 +194,13 @@ Internet-Draft DNSSEC Experiments April 2006 This method also precludes any zone from being both in an experiment and in a classic DNSSEC island of security. That is, a zone is - either in an experiment and only experimentally validatable, or it is - not. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 7] - -Internet-Draft DNSSEC Experiments April 2006 - + either in an experiment and only possible to validate experimentally, + or it is not. 5. Defining an Experiment The DNSSEC experiment MUST define the particular set of (previously - unknown) algorithm identifiers that identify the experiment, and + unknown) algorithm identifiers that identify the experiment and define what each unknown algorithm identifier means. Typically, unless the experiment is actually experimenting with a new DNSSEC algorithm, this will be a mapping of private algorithm identifiers to @@ -407,9 +211,9 @@ Internet-Draft DNSSEC Experiments April 2006 authors of the experiment. Then the experiment will define a mapping between known mandatory and optional algorithms into this private algorithm identifier space. Alternately, the experiment MAY use the - OID private algorithm space instead (using algorithm number 254), or - MAY choose non-private algorithm numbers, although this would require - an IANA allocation. + Object Identifier (OID) private algorithm space instead (using + algorithm number 254), or MAY choose non-private algorithm numbers, + although this would require an IANA allocation. For example, an experiment might specify in its description the DNS name "dnssec-experiment-a.example.com" as the base name, and declare @@ -417,6 +221,13 @@ Internet-Draft DNSSEC Experiments April 2006 algorithm 3 (DSA), and that "5.dnssec-experiment-a.example.com" is an alias of DNSSEC algorithm 5 (RSASHA1). + + +Blacka Standards Track [Page 4] + +RFC 4955 DNS Security (DNSSEC) Experiments July 2007 + + Resolvers MUST only recognize the experiment's semantics when present in a zone signed by one or more of these algorithm identifiers. This is necessary to isolate the semantics of one experiment from any @@ -426,85 +237,21 @@ Internet-Draft DNSSEC Experiments April 2006 understand both standard DNSSEC and the defined experimental DNSSEC protocol, although this isn't required. - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 8] - -Internet-Draft DNSSEC Experiments April 2006 - - 6. Considerations There are a number of considerations with using this methodology. - 1. Under some circumstances, it may be that the experiment will not - be sufficiently masked by this technique and may cause resolution - problem for resolvers not aware of the experiment. For instance, - the resolver may look at a non-validatable response and conclude - that the response is bogus, either due to local policy or - implementation details. This is not expected to be a common - case, however. + 1. If an unaware validator does not correctly follow the rules laid + out in RFC 4035 (e.g., the validator interprets a DNSSEC record + prior to validating it), or if the experiment is broader in scope + that just modifying the DNSSEC semantics, the experiment may not + be sufficiently masked by this technique. This may cause + unintended resolution failures. 2. It will not be possible for security-aware resolvers unaware of the experiment to build a chain of trust through an experimental zone. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 9] - -Internet-Draft DNSSEC Experiments April 2006 - - 7. Use in Non-Experiments This general methodology MAY be used for non-backwards compatible @@ -519,48 +266,6 @@ Internet-Draft DNSSEC Experiments April 2006 o Resolvers MAY recognize the protocol change in zones not signed (or not solely signed) using the new algorithm identifiers. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 10] - -Internet-Draft DNSSEC Experiments April 2006 - - 8. Security Considerations Zones using this methodology will be considered insecure by all @@ -568,114 +273,24 @@ Internet-Draft DNSSEC Experiments April 2006 possible to create a secure delegation from an experimental zone that will be followed by resolvers unaware of the experiment. + Implementers should take into account any security issues that may + result from environments being configured to trust both experimental + and non-experimental zones. If the experimental zone is more - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 11] +Blacka Standards Track [Page 5] -Internet-Draft DNSSEC Experiments April 2006 +RFC 4955 DNS Security (DNSSEC) Experiments July 2007 -9. IANA Considerations + vulnerable to attacks, it could, for example, be used to promote + trust in zones not part of the experiment, possibly under the control + of an attacker. - This document has no IANA actions. +9. References - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 12] - -Internet-Draft DNSSEC Experiments April 2006 - - -10. References - -10.1. Normative References +9.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. @@ -692,42 +307,13 @@ Internet-Draft DNSSEC Experiments April 2006 "Protocol Modifications for the DNS Security Extensions", RFC 4035, March 2005. -10.2. Informative References +9.2. Informative References [5] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. - [6] Austein, R. and S. Weiler, "Clarifications and Implementation - Notes for DNSSECbis", draft-ietf-dnsext-dnssec-bis-updates-02 - (work in progress), January 2006. - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 13] - -Internet-Draft DNSSEC Experiments April 2006 - + [6] Weiler, S. and R. Austein, "Clarifications and Implementation + Notes for DNSSECbis", Work in Progress, March 2007. Author's Address @@ -738,7 +324,7 @@ Author's Address US Phone: +1 703 948 3200 - Email: davidb@verisign.com + EMail: davidb@verisign.com URI: http://www.verisignlabs.com @@ -749,45 +335,14 @@ Author's Address - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Blacka Expires October 9, 2006 [Page 14] +Blacka Standards Track [Page 6] -Internet-Draft DNSSEC Experiments April 2006 +RFC 4955 DNS Security (DNSSEC) Experiments July 2007 Full Copyright Statement - Copyright (C) The Internet Society (2006). + Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors @@ -795,13 +350,12 @@ Full Copyright Statement This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND + THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS + OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF + THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - Intellectual Property The IETF takes no position regarding the validity or scope of any @@ -826,15 +380,16 @@ Intellectual Property this standard. Please address the information to the IETF at ietf-ipr@ietf.org. +Acknowledgement -Acknowledgment - - Funding for the RFC Editor function is provided by the IETF - Administrative Support Activity (IASA). + Funding for the RFC Editor function is currently provided by the + Internet Society. -Blacka Expires October 9, 2006 [Page 15] + + +Blacka Standards Track [Page 7] diff --git a/doc/draft/draft-ietf-dnsext-dnssec-opt-in-07.txt b/doc/rfc/rfc4956.txt similarity index 59% rename from doc/draft/draft-ietf-dnsext-dnssec-opt-in-07.txt rename to doc/rfc/rfc4956.txt index 17e28e8286..536c680cba 100644 --- a/doc/draft/draft-ietf-dnsext-dnssec-opt-in-07.txt +++ b/doc/rfc/rfc4956.txt @@ -1,90 +1,89 @@ -DNSEXT R. Arends -Internet-Draft Telematica Instituut -Expires: January 19, 2006 M. Kosters + + + +Network Working Group R. Arends +Request for Comments: 4956 Nominet +Category: Experimental M. Kosters D. Blacka - Verisign, Inc. - July 18, 2005 + VeriSign, Inc. + July 2007 - DNSSEC Opt-In - draft-ietf-dnsext-dnssec-opt-in-07 + DNS Security (DNSSEC) Opt-In -Status of this Memo +Status of This Memo - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on January 19, 2006. + This memo defines an Experimental Protocol for the Internet + community. It does not specify an Internet standard of any kind. + Discussion and suggestions for improvement are requested. + Distribution of this memo is unlimited. Copyright Notice - Copyright (C) The Internet Society (2005). + Copyright (C) The IETF Trust (2007). Abstract - In the DNS security extensions (DNSSEC, defined in RFC 4033 [3], RFC - 4034 [4], and RFC 4035 [5]), delegations to unsigned subzones are - cryptographically secured. Maintaining this cryptography is not - practical or necessary. This document describes an experimental - "Opt-In" model that allows administrators to omit this cryptography - and manage the cost of adopting DNSSEC with large zones. + In the DNS security (DNSSEC) extensions, delegations to unsigned + subzones are cryptographically secured. Maintaining this + cryptography is not always practical or necessary. This document + describes an experimental "Opt-In" model that allows administrators + to omit this cryptography and manage the cost of adopting DNSSEC with + large zones. -Arends, et al. Expires January 19, 2006 [Page 1] + + + + + + + + + + + + + + + + + + + +Arends, et al. Experimental [Page 1] -Internet-Draft DNSSEC Opt-In July 2005 +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 Table of Contents - 1. Definitions and Terminology . . . . . . . . . . . . . . . . . 3 - 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Definitions and Terminology . . . . . . . . . . . . . . . . . 3 3. Experimental Status . . . . . . . . . . . . . . . . . . . . . 4 - 4. Protocol Additions . . . . . . . . . . . . . . . . . . . . . . 4 - 4.1 Server Considerations . . . . . . . . . . . . . . . . . . 5 - 4.1.1 Delegations Only . . . . . . . . . . . . . . . . . . . 5 - 4.1.2 Insecure Delegation Responses . . . . . . . . . . . . 6 - 4.1.3 Wildcards and Opt-In . . . . . . . . . . . . . . . . . 6 - 4.1.4 Dynamic Update . . . . . . . . . . . . . . . . . . . . 7 - 4.2 Client Considerations . . . . . . . . . . . . . . . . . . 7 - 4.2.1 Delegations Only . . . . . . . . . . . . . . . . . . . 7 - 4.2.2 Validation Process Changes . . . . . . . . . . . . . . 7 - 4.2.3 NSEC Record Caching . . . . . . . . . . . . . . . . . 8 - 4.2.4 Use of the AD bit . . . . . . . . . . . . . . . . . . 8 + 4. Protocol Additions . . . . . . . . . . . . . . . . . . . . . . 5 + 4.1. Server Considerations . . . . . . . . . . . . . . . . . . 6 + 4.1.1. Delegations Only . . . . . . . . . . . . . . . . . . . 6 + 4.1.2. Insecure Delegation Responses . . . . . . . . . . . . 6 + 4.1.3. Dynamic Update . . . . . . . . . . . . . . . . . . . . 6 + 4.2. Client Considerations . . . . . . . . . . . . . . . . . . 7 + 4.2.1. Delegations Only . . . . . . . . . . . . . . . . . . . 7 + 4.2.2. Validation Process Changes . . . . . . . . . . . . . . 7 + 4.2.3. NSEC Record Caching . . . . . . . . . . . . . . . . . 8 + 4.2.4. Use of the AD bit . . . . . . . . . . . . . . . . . . 8 5. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7. Transition Issues . . . . . . . . . . . . . . . . . . . . . . 10 + 7. Transition Issues . . . . . . . . . . . . . . . . . . . . . . 11 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 - 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 12 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 11.1 Normative References . . . . . . . . . . . . . . . . . . . 13 - 11.2 Informative References . . . . . . . . . . . . . . . . . . 13 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14 - A. Implementing Opt-In using "Views" . . . . . . . . . . . . . . 14 - Intellectual Property and Copyright Statements . . . . . . . . 16 + 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 + 10.2. Informative References . . . . . . . . . . . . . . . . . . 13 + Appendix A. Implementing Opt-In Using "Views" . . . . . . . . . . 15 @@ -108,100 +107,131 @@ Table of Contents -Arends, et al. Expires January 19, 2006 [Page 2] + + + + +Arends, et al. Experimental [Page 2] -Internet-Draft DNSSEC Opt-In July 2005 +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 -1. Definitions and Terminology - - Throughout this document, familiarity with the DNS system (RFC 1035 - [1]), DNS security extensions ([3], [4], and [5], referred to in this - document as "standard DNSSEC"), and DNSSEC terminology (RFC 3090 - [10]) is assumed. - - The following abbreviations and terms are used in this document: - - RR: is used to refer to a DNS resource record. - RRset: refers to a Resource Record Set, as defined by [8]. In this - document, the RRset is also defined to include the covering RRSIG - records, if any exist. - signed name: refers to a DNS name that has, at minimum, a (signed) - NSEC record. - unsigned name: refers to a DNS name that does not (at least) have a - NSEC record. - covering NSEC record/RRset: is the NSEC record used to prove - (non)existence of a particular name or RRset. This means that for - a RRset or name 'N', the covering NSEC record has the name 'N', or - has an owner name less than 'N' and "next" name greater than 'N'. - delegation: refers to a NS RRset with a name different from the - current zone apex (non-zone-apex), signifying a delegation to a - subzone. - secure delegation: refers to a signed name containing a delegation - (NS RRset), and a signed DS RRset, signifying a delegation to a - signed subzone. - insecure delegation: refers to a signed name containing a delegation - (NS RRset), but lacking a DS RRset, signifying a delegation to an - unsigned subzone. - Opt-In insecure delegation: refers to an unsigned name containing - only a delegation NS RRset. The covering NSEC record uses the - Opt-In methodology described in this document. - - The key words "MUST, "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY, and "OPTIONAL" in this - document are to be interpreted as described in RFC 2119 [7]. - -2. Overview +1. Overview The cost to cryptographically secure delegations to unsigned zones is high for large delegation-centric zones and zones where insecure delegations will be updated rapidly. For these zones, the costs of - maintaining the NSEC record chain may be extremely high relative to - the gain of cryptographically authenticating existence of unsecured - zones. + maintaining the NextSECure (NSEC) record chain may be extremely high + relative to the gain of cryptographically authenticating existence of + unsecured zones. This document describes an experimental method of eliminating the - - - -Arends, et al. Expires January 19, 2006 [Page 3] - -Internet-Draft DNSSEC Opt-In July 2005 - - superfluous cryptography present in secure delegations to unsigned zones. Using "Opt-In", a zone administrator can choose to remove insecure delegations from the NSEC chain. This is accomplished by extending the semantics of the NSEC record by using a redundant bit in the type map. +2. Definitions and Terminology + + Throughout this document, familiarity with the DNS system (RFC 1035 + [1]), DNS security extensions ([4], [5], and [6], referred to in this + document as "standard DNSSEC"), and DNSSEC terminology (RFC 3090 + [10]) is assumed. + + The following abbreviations and terms are used in this document: + + RR: is used to refer to a DNS resource record. + + RRset: refers to a Resource Record Set, as defined by [8]. In this + document, the RRset is also defined to include the covering RRSIG + records, if any exist. + + signed name: refers to a DNS name that has, at minimum, a (signed) + NSEC record. + + unsigned name: refers to a DNS name that does not (at least) have an + NSEC record. + + covering NSEC record/RRset: is the NSEC record used to prove + (non)existence of a particular name or RRset. This means that for + a RRset or name 'N', the covering NSEC record has the name 'N', or + has an owner name less than 'N' and "next" name greater than 'N'. + + delegation: refers to an NS RRset with a name different from the + current zone apex (non-zone-apex), signifying a delegation to a + subzone. + + + + + + +Arends, et al. Experimental [Page 3] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + + secure delegation: refers to a signed name containing a delegation + (NS RRset), and a signed DS RRset, signifying a delegation to a + signed subzone. + + insecure delegation: refers to a signed name containing a delegation + (NS RRset), but lacking a DS RRset, signifying a delegation to an + unsigned subzone. + + Opt-In insecure delegation: refers to an unsigned name containing + only a delegation NS RRset. The covering NSEC record uses the + Opt-In methodology described in this document. + + The key words "MUST, "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY, and "OPTIONAL" in this + document are to be interpreted as described in RFC 2119 [2]. + 3. Experimental Status This document describes an EXPERIMENTAL extension to DNSSEC. It interoperates with non-experimental DNSSEC using the technique - described in [6]. This experiment is identified with the following + described in [7]. This experiment is identified with the following private algorithms (using algorithm 253): - "3.optin.verisignlabs.com": is an alias for DNSSEC algorithm 3, DSA, + "3.optin.verisignlabs.com": is an alias for DNSSEC algorithm 3, DSA, and - "5.optin.verisignlabs.com": is an alias for DNSSEC algorithm 5, + + "5.optin.verisignlabs.com": is an alias for DNSSEC algorithm 5, RSASHA1. Servers wishing to sign and serve zones that utilize Opt-In MUST sign - the zone with only one or more of these private algorithms. This - requires the signing tools and servers to support private algorithms, - as well as Opt-In. + the zone with only one or more of these private algorithms and MUST + NOT use any other algorithms. - Resolvers wishing to validate Opt-In zones MUST only do so when the - zone is only signed using one or more of these private algorithms. + Resolvers MUST NOT apply the Opt-In validation rules described in + this document unless a zone is signed using one or more of these + private algorithms. + + This experimental protocol relaxes the restriction that validators + MUST ignore the setting of the NSEC bit in the type map as specified + in RFC 4035 [6] Section 5.4. The remainder of this document assumes that the servers and resolvers involved are aware of and are involved in this experiment. + + + + + + + +Arends, et al. Experimental [Page 4] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + 4. Protocol Additions In DNSSEC, delegation NS RRsets are not signed, but are instead - accompanied by a NSEC RRset of the same name and (possibly) a DS + accompanied by an NSEC RRset of the same name and (possibly) a DS record. The security status of the subzone is determined by the presence or absence of the DS RRset, cryptographically proven by the NSEC record. Opt-In expands this definition by allowing insecure @@ -217,14 +247,6 @@ Internet-Draft DNSSEC Opt-In July 2005 delegation nodes. This tag is indicated by the absence of the NSEC bit in the type map. Since the NSEC bit in the type map merely indicates the existence of the record itself, this bit is redundant - - - -Arends, et al. Expires January 19, 2006 [Page 4] - -Internet-Draft DNSSEC Opt-In July 2005 - - and safe for use as a tag. An Opt-In tagged NSEC record does not assert the (non)existence of @@ -236,11 +258,11 @@ Internet-Draft DNSSEC Opt-In July 2005 An Opt-In NSEC record MAY have the same name as an insecure delegation. In this case, the delegation is proven insecure by the - lack of a DS bit in type map and the signed NSEC record does assert - the existence of the delegation. + lack of a DS bit in the type map, and the signed NSEC record does + assert the existence of the delegation. Zones using Opt-In MAY contain a mixture of Opt-In tagged NSEC - records and standard DNSSEC NSEC records. If a NSEC record is not + records and standard DNSSEC NSEC records. If an NSEC record is not Opt-In, there MUST NOT be any insecure delegations (or any other records) between it and the RRsets indicated by the 'next domain name' in the NSEC RDATA. If it is Opt-In, there MUST only be @@ -251,39 +273,43 @@ Internet-Draft DNSSEC Opt-In July 2005 o An Opt-In NSEC type is identified by a zero-valued (or not- specified) NSEC bit in the type bit map of the NSEC record. - o A RFC2535bis NSEC type is identified by a one-valued NSEC bit in - the type bit map of the NSEC record. - and, + + + + + +Arends, et al. Experimental [Page 5] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + + o A standard DNSSEC NSEC type is identified by a one-valued NSEC bit + in the type bit map of the NSEC record. + + and o An Opt-In NSEC record does not assert the non-existence of a name between its owner name and "next" name, although it does assert that any name in this span MUST be an insecure delegation. + o An Opt-In NSEC record does assert the (non)existence of RRsets with the same owner name. -4.1 Server Considerations +4.1. Server Considerations Opt-In imposes some new requirements on authoritative DNS servers. -4.1.1 Delegations Only +4.1.1. Delegations Only This specification dictates that only insecure delegations may exist between the owner and "next" names of an Opt-In tagged NSEC record. - Signing tools SHOULD NOT generate signed zones that violate this - restriction. Servers SHOULD refuse to load and/or serve zones that - violate this restriction. Servers also SHOULD reject AXFR or IXFR - - - -Arends, et al. Expires January 19, 2006 [Page 5] - -Internet-Draft DNSSEC Opt-In July 2005 - - + Signing tools MUST NOT generate signed zones that violate this + restriction. Servers MUST refuse to load and/or serve zones that + violate this restriction. Servers also MUST reject AXFR or IXFR responses that violate this restriction. -4.1.2 Insecure Delegation Responses +4.1.2. Insecure Delegation Responses When returning an Opt-In insecure delegation, the server MUST return the covering NSEC RRset in the Authority section. @@ -294,54 +320,7 @@ Internet-Draft DNSSEC Opt-In July 2005 different owner name from the delegation RRset. This may require implementations to search for the covering NSEC RRset. -4.1.3 Wildcards and Opt-In - - Standard DNSSEC describes the practice of returning NSEC records to - prove the non-existence of an applicable wildcard in non-existent - name responses. This NSEC record can be described as a "negative - wildcard proof". The use of Opt-In NSEC records changes the - necessity for this practice. For non-existent name responses when - the query name (qname) is covered by an Opt-In tagged NSEC record, - servers MAY choose to omit the wildcard proof record, and clients - MUST NOT treat the absence of this NSEC record as a validation error. - - The intent of the standard DNSSEC negative wildcard proof requirement - is to prevent malicious users from undetectably removing valid - wildcard responses. In order for this cryptographic proof to work, - the resolver must be able to prove: - - 1. The exact qname does not exist. This is done by the "normal" - NSEC record. - 2. No applicable wildcard exists. This is done by returning a NSEC - record proving that the wildcard does not exist (this is the - negative wildcard proof). - - However, if the NSEC record covering the exact qname is an Opt-In - NSEC record, the resolver will not be able to prove the first part of - this equation, as the qname might exist as an insecure delegation. - Thus, since the total proof cannot be completed, the negative - wildcard proof NSEC record is not useful. - - The negative wildcard proof is also not useful when returned as part - of an Opt-In insecure delegation response for a similar reason: the - resolver cannot prove that the qname does or does not exist, and - therefore cannot prove that a wildcard expansion is valid. - - The presence of an Opt-In tagged NSEC record does not change the - practice of returning a NSEC along with a wildcard expansion. Even - - - -Arends, et al. Expires January 19, 2006 [Page 6] - -Internet-Draft DNSSEC Opt-In July 2005 - - - though the Opt-In NSEC will not be able to prove that the wildcard - expansion is valid, it will prove that the wildcard expansion is not - masking any signed records. - -4.1.4 Dynamic Update +4.1.3. Dynamic Update Opt-In changes the semantics of Secure DNS Dynamic Update [9]. In particular, it introduces the need for rules that describe when to @@ -351,23 +330,36 @@ Internet-Draft DNSSEC Opt-In July 2005 zones that use Opt-In NSEC records. Servers SHOULD return responses to update requests with RCODE=REFUSED. -4.2 Client Considerations + + + + + +Arends, et al. Experimental [Page 6] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + +4.2. Client Considerations Opt-In imposes some new requirements on security-aware resolvers (caching or otherwise). -4.2.1 Delegations Only +4.2.1. Delegations Only - As stated in the "Server Considerations" section above, this - specification restricts the namespace covered by Opt-In tagged NSEC - records to insecure delegations only. Thus, resolvers MUST reject as - invalid any records that fall within an Opt-In NSEC record's span - that are not NS records or corresponding glue records. + As stated in Section 4.1 above, this specification restricts the + namespace covered by Opt-In tagged NSEC records to insecure + delegations only. Clients are not expected to take any special + measures to enforce this restriction; instead, it forms an underlying + assumption that clients may rely on. -4.2.2 Validation Process Changes +4.2.2. Validation Process Changes This specification does not change the resolver's resolution algorithm. However, it does change the DNSSEC validation process. + +4.2.2.1. Referrals + Resolvers MUST be able to use Opt-In tagged NSEC records to cryptographically prove the validity and security status (as insecure) of a referral. Resolvers determine the security status of @@ -379,31 +371,39 @@ Internet-Draft DNSSEC Opt-In July 2005 signed. The absence of the DS RRset is proven using a verified NSEC record of the same name that does not have the DS bit set in the type map. This NSEC record MAY also be tagged as Opt-In. + o Using Opt-In, the security status is proven by the existence of a DS record (for signed) or the presence of a verified Opt-In tagged NSEC record that covers the delegation name. That is, the NSEC record does not have the NSEC bit set in the type map, and the delegation name falls between the NSEC's owner and "next" name. - - - -Arends, et al. Expires January 19, 2006 [Page 7] - -Internet-Draft DNSSEC Opt-In July 2005 - - Using Opt-In does not substantially change the nature of following referrals within DNSSEC. At every delegation point, the resolver will have cryptographic proof that the referred-to subzone is signed or unsigned. - When receiving either an Opt-In insecure delegation response or a - non-existent name response where that name is covered by an Opt-In - tagged NSEC record, the resolver MUST NOT require proof (in the form - of a NSEC record) that a wildcard did not exist. +4.2.2.2. Queries for DS Resource Records -4.2.3 NSEC Record Caching + Since queries for DS records are directed to the parent side of a + zone cut (see [5], Section 5), negative responses to these queries + may be covered by an Opt-In flagged NSEC record. + + + +Arends, et al. Experimental [Page 7] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + + Resolvers MUST be able to use Opt-In tagged NSEC records to + cryptographically prove the validity and security status of negative + responses to queries for DS records. In particular, a NOERROR/NODATA + (i.e., RCODE=3, but the answer section is empty) response to a DS + query may be proven by an Opt-In flagged covering NSEC record, rather + than an NSEC record matching the query name. + +4.2.3. NSEC Record Caching Caching resolvers MUST be able to retrieve the appropriate covering Opt-In NSEC record when returning referrals that need them. This @@ -412,16 +412,21 @@ Internet-Draft DNSSEC Opt-In July 2005 implementations may have to use new methods for finding these NSEC records. -4.2.4 Use of the AD bit +4.2.4. Use of the AD bit - The AD bit, as defined by [2] and [5], MUST NOT be set when: + The AD bit, as defined by [3] and [6], MUST NOT be set when: o sending a Name Error (RCODE=3) response where the covering NSEC is tagged as Opt-In. + o sending an Opt-In insecure delegation response, unless the covering (Opt-In) NSEC record's owner name equals the delegation name. + o sending a NOERROR/NODATA response when query type is DS and the + covering NSEC is tagged as Opt-In, unless NSEC record's owner name + matches the query name. + This rule is based on what the Opt-In NSEC record actually proves: for names that exist between the Opt-In NSEC record's owner and "next" names, the Opt-In NSEC record cannot prove the non-existence @@ -439,21 +444,22 @@ Internet-Draft DNSSEC Opt-In July 2005 delegations to unsigned subzones, can lead to substantial space savings (both in memory and on disk). Additionally, Opt-In allows for the addition or removal of insecure delegations without modifying - the NSEC record chain. Zones that are frequently updating insecure - delegations (e.g., TLDs) can avoid the substantial overhead of -Arends, et al. Expires January 19, 2006 [Page 8] +Arends, et al. Experimental [Page 8] -Internet-Draft DNSSEC Opt-In July 2005 +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 - modifying and resigning the affected NSEC records. + the NSEC record chain. Zones that are frequently updating insecure + delegations (e.g., Top-Level Domains (TLDs)) can avoid the + substantial overhead of modifying and resigning the affected NSEC + records. 6. Example - Consider the zone EXAMPLE, shown below. This is a zone where all of + Consider the zone EXAMPLE shown below. This is a zone where all of the NSEC records are tagged as Opt-In. Example A: Fully Opt-In Zone. @@ -490,22 +496,27 @@ Internet-Draft DNSSEC Opt-In July 2005 NS.UNSIGNED.EXAMPLE. A ... + Example A. + + + + + + +Arends, et al. Experimental [Page 9] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + In this example, a query for a signed RRset (e.g., "FIRST- - SECURE.EXAMPLE A"), or a secure delegation ("WWW.SECOND- - SECURE.EXAMPLE A") will result in a standard DNSSEC response. + SECURE.EXAMPLE A") or a secure delegation ("WWW.SECOND-SECURE.EXAMPLE + A") will result in a standard DNSSEC response. A query for a nonexistent RRset will result in a response that - differs from standard DNSSEC by: the NSEC record will be tagged as - Opt-In, there may be no NSEC record proving the non-existence of a - - - -Arends, et al. Expires January 19, 2006 [Page 9] - -Internet-Draft DNSSEC Opt-In July 2005 - - - matching wildcard record, and the AD bit will not be set. + differs from standard DNSSEC by the following: the NSEC record will + be tagged as Opt-In, there may be no NSEC record proving the non- + existence of a matching wildcard record, and the AD bit will not be + set. A query for an insecure delegation RRset (or a referral) will return both the answer (in the Authority section) and the corresponding @@ -526,6 +537,8 @@ Internet-Draft DNSSEC Opt-In July 2005 Additional Section: NS.UNSIGNED.EXAMPLE. A ... + Example A.1 + In the Example A.1 zone, the EXAMPLE. node MAY use either style of NSEC record, because there are no insecure delegations that occur between it and the next node, FIRST-SECURE.EXAMPLE. In other words, @@ -543,6 +556,14 @@ Internet-Draft DNSSEC Opt-In July 2005 NOT-SECURE-2.EXAMPLE. is an example of an insecure delegation that is part of the NSEC chain and also covered by an Opt-In tagged NSEC record. Because NOT-SECURE-2.EXAMPLE. is a signed name, it cannot be + + + +Arends, et al. Experimental [Page 10] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + removed from the zone without modifying and resigning the prior NSEC record. Delegations with names that fall between NOT-SECURE- 2.EXAMPLE. and SECOND-SECURE.EXAMPLE. may be added or removed without @@ -551,16 +572,8 @@ Internet-Draft DNSSEC Opt-In July 2005 7. Transition Issues Opt-In is not backwards compatible with standard DNSSEC and is - considered experimental. Standard DNSSEC compliant implementations + considered experimental. Standard DNSSEC-compliant implementations would not recognize Opt-In tagged NSEC records as different from - - - -Arends, et al. Expires January 19, 2006 [Page 10] - -Internet-Draft DNSSEC Opt-In July 2005 - - standard NSEC records. Because of this, standard DNSSEC implementations, if they were to validate Opt-In style responses, would reject all Opt-In insecure delegations within a zone as @@ -579,15 +592,16 @@ Internet-Draft DNSSEC Opt-In July 2005 Opt-In allows for unsigned names, in the form of delegations to unsigned subzones, to exist within an otherwise signed zone. All unsigned names are, by definition, insecure, and their validity or - existence cannot by cryptographically proven. + existence cannot be cryptographically proven. In general: - o Records with unsigned names (whether existing or not) suffer from + o Records with unsigned names (whether or not existing) suffer from the same vulnerabilities as records in an unsigned zone. These vulnerabilities are described in more detail in [12] (note in - particular sections 2.3, "Name Games" and 2.6, "Authenticated + particular Sections 2.3, "Name Games" and 2.6, "Authenticated Denial"). + o Records with signed names have the same security whether or not Opt-In is used. @@ -597,26 +611,25 @@ Internet-Draft DNSSEC Opt-In July 2005 the ability to prove the existence or nonexistence of an insecure delegation within the span of an Opt-In NSEC record. + + + + +Arends, et al. Experimental [Page 11] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + In particular, this means that a malicious entity may be able to insert or delete records with unsigned names. These records are normally NS records, but this also includes signed wildcard expansions (while the wildcard record itself is signed, its expanded - name is an unsigned name). + name is an unsigned name), which can be undetectably removed or used + to replace an existing unsigned delegation. For example, if a resolver received the following response from the example zone above: - - - - - - -Arends, et al. Expires January 19, 2006 [Page 11] - -Internet-Draft DNSSEC Opt-In July 2005 - - Example S.1: Response to query for WWW.DOES-NOT-EXIST.EXAMPLE. A RCODE=NOERROR @@ -632,6 +645,8 @@ Internet-Draft DNSSEC Opt-In July 2005 Additional Section: + Attacker has forged a name + The resolver would have no choice but to believe that the referral to NS.FORGED. is valid. If a wildcard existed that would have been expanded to cover "WWW.DOES-NOT-EXIST.EXAMPLE.", an attacker could @@ -640,77 +655,83 @@ Internet-Draft DNSSEC Opt-In July 2005 Note that being able to add a delegation is functionally equivalent to being able to add any record type: an attacker merely has to forge - a delegation to nameserver under his/her control and place whatever - records needed at the subzone apex. + a delegation to the nameserver under his/her control and place + whatever records are needed at the subzone apex. While in particular cases, this issue may not present a significant security problem, in general it should not be lightly dismissed. Therefore, it is strongly RECOMMENDED that Opt-In be used sparingly. In particular, zone signing tools SHOULD NOT default to Opt-In, and - MAY choose to not support Opt-In at all. - -9. IANA Considerations - - None. - -10. Acknowledgments - - The contributions, suggestions and remarks of the following persons - (in alphabetic order) to this draft are acknowledged: - - Mats Dufberg, Miek Gieben, Olafur Gudmundsson, Bob Halley, Olaf - Kolkman, Edward Lewis, Ted Lindgreen, Rip Loomis, Bill Manning, - Dan Massey, Scott Rose, Mike Schiraldi, Jakob Schlyter, Brian - Wellington. - -11. References + MAY choose not to support Opt-In at all. -Arends, et al. Expires January 19, 2006 [Page 12] + + + + +Arends, et al. Experimental [Page 12] -Internet-Draft DNSSEC Opt-In July 2005 +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 -11.1 Normative References +9. Acknowledgments - [1] Mockapetris, P., "Domain names - implementation and - specification", STD 13, RFC 1035, November 1987. + The contributions, suggestions, and remarks of the following persons + (in alphabetic order) to this document are acknowledged: - [2] Wellington, B. and O. Gudmundsson, "Redefinition of DNS - Authenticated Data (AD) bit", RFC 3655, November 2003. + Mats Kolkman, Edward Lewis, Ted Lindgreen, Rip Loomis, Bill + Manning, Dan Massey, Scott Rose, Mike Schiraldi, Jakob Schlyter, + Brian Wellington. - [3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, - "DNS Security Introduction and Requirements", RFC 4033, - March 2005. +10. References - [4] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, - "Resource Records for the DNS Security Extensions", RFC 4034, - March 2005. +10.1. Normative References - [5] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, - "Protocol Modifications for the DNS Security Extensions", - RFC 4035, March 2005. + [1] Mockapetris, P., "Domain names - implementation and + specification", STD 13, RFC 1035, November 1987. - [6] Blacka, D., "DNSSEC Experiments", - draft-ietf-dnsext-dnssec-experiments-01 (work in progress), - July 2005. - -11.2 Informative References - - [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement + [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. + [3] Wellington, B. and O. Gudmundsson, "Redefinition of DNS + Authenticated Data (AD) bit", RFC 3655, November 2003. + + [4] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, + "DNS Security Introduction and Requirements", RFC 4033, + March 2005. + + [5] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, + "Resource Records for the DNS Security Extensions", RFC 4034, + March 2005. + + [6] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, + "Protocol Modifications for the DNS Security Extensions", + RFC 4035, March 2005. + + [7] Blacka, D., "DNSSEC Experiments", RFC 4955, July 2007. + +10.2. Informative References + [8] Elz, R. and R. Bush, "Clarifications to the DNS Specification", RFC 2181, July 1997. - [9] Eastlake, D., "Secure Domain Name System Dynamic Update", - RFC 2137, April 1997. + [9] Wellington, B., "Secure Domain Name System (DNS) Dynamic + Update", RFC 3007, November 2000. [10] Lewis, E., "DNS Security Extension Clarification on Zone Status", RFC 3090, March 2001. + + + + +Arends, et al. Experimental [Page 13] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + [11] Conrad, D., "Indicating Resolver Support of DNSSEC", RFC 3225, December 2001. @@ -724,44 +745,50 @@ Internet-Draft DNSSEC Opt-In July 2005 -Arends, et al. Expires January 19, 2006 [Page 13] + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Arends, et al. Experimental [Page 14] -Internet-Draft DNSSEC Opt-In July 2005 +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 -Authors' Addresses - - Roy Arends - Telematica Instituut - Drienerlolaan 5 - 7522 NB Enschede - NL - - Email: roy.arends@telin.nl - - - Mark Kosters - Verisign, Inc. - 21355 Ridgetop Circle - Dulles, VA 20166 - US - - Phone: +1 703 948 3200 - Email: markk@verisign.com - URI: http://www.verisignlabs.com - - - David Blacka - Verisign, Inc. - 21355 Ridgetop Circle - Dulles, VA 20166 - US - - Phone: +1 703 948 3200 - Email: davidb@verisign.com - URI: http://www.verisignlabs.com - -Appendix A. Implementing Opt-In using "Views" +Appendix A. Implementing Opt-In Using "Views" In many cases, it may be convenient to implement an Opt-In zone by combining two separately maintained "views" of a zone at request @@ -777,41 +804,87 @@ Appendix A. Implementing Opt-In using "Views" In addition, the only RRsets that may solely exist in the insecure view are non-zone-apex NS RRsets. That is, all non-NS RRsets (and - - - -Arends, et al. Expires January 19, 2006 [Page 14] - -Internet-Draft DNSSEC Opt-In July 2005 - - the zone apex NS RRset) MUST be signed and in the secure view. These two views may be combined at request time to provide a virtual, single Opt-In zone. The following algorithm is used when responding to each query: + V_A is the secure view as described above. + V_B is the insecure view as described above. - R_A is a response generated from V_A, following RFC 2535bis. + + R_A is a response generated from V_A, following standard DNSSEC. + R_B is a response generated from V_B, following DNS resolution as per RFC 1035 [1]. + R_C is the response generated by combining R_A with R_B, as described below. - A query is DNSSEC-aware if it either has the DO bit [11] turned - on, or is for a DNSSEC-specific record type. - + A query is DNSSEC-aware if it either has the DO bit [11] turned on + or is for a DNSSEC-specific record type. 1. If V_A is a subset of V_B and the query is not DNSSEC-aware, generate and return R_B, otherwise + 2. Generate R_A. + 3. If R_A's RCODE != NXDOMAIN, return R_A, otherwise + + + + + + + + +Arends, et al. Experimental [Page 15] + +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 + + 4. Generate R_B and combine it with R_A to form R_C: + For each section (ANSWER, AUTHORITY, ADDITIONAL), copy the records from R_A into R_B, EXCEPT the AUTHORITY section SOA record, if R_B's RCODE = NOERROR. + 5. Return R_C. +Authors' Addresses + + Roy Arends + Nominet + Sandford Gate + Sandy Lane West + Oxford OX4 6LB + UNITED KINGDOM + + Phone: +44 1865 332211 + EMail: roy@nominet.org.uk + + + Mark Kosters + VeriSign, Inc. + 21355 Ridgetop Circle + Dulles, VA 20166 + US + + Phone: +1 703 948 3200 + EMail: mkosters@verisign.com + URI: http://www.verisignlabs.com + + + David Blacka + VeriSign, Inc. + 21355 Ridgetop Circle + Dulles, VA 20166 + US + + Phone: +1 703 948 3200 + EMail: davidb@verisign.com + URI: http://www.verisignlabs.com @@ -822,26 +895,28 @@ Internet-Draft DNSSEC Opt-In July 2005 - - - - - - - - - - - - - - -Arends, et al. Expires January 19, 2006 [Page 15] +Arends, et al. Experimental [Page 16] -Internet-Draft DNSSEC Opt-In July 2005 +RFC 4956 DNS Security (DNSSEC) Opt-In July 2007 -Intellectual Property Statement +Full Copyright Statement + + Copyright (C) The IETF Trust (2007). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND + THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS + OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF + THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to @@ -865,26 +940,7 @@ Intellectual Property Statement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. - -Disclaimer of Validity - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Copyright Statement - - Copyright (C) The Internet Society (2005). This document is subject - to the rights, licenses and restrictions contained in BCP 78, and - except as set forth therein, the authors retain all their rights. - - -Acknowledgment +Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. @@ -892,5 +948,8 @@ Acknowledgment -Arends, et al. Expires January 19, 2006 [Page 16] + + + +Arends, et al. Experimental [Page 17] diff --git a/doc/draft/draft-ietf-dnsext-nsid-01.txt b/doc/rfc/rfc5001.txt similarity index 68% rename from doc/draft/draft-ietf-dnsext-nsid-01.txt rename to doc/rfc/rfc5001.txt index 90d1a0609d..fe15339369 100644 --- a/doc/draft/draft-ietf-dnsext-nsid-01.txt +++ b/doc/rfc/rfc5001.txt @@ -1,42 +1,27 @@ + + + Network Working Group R. Austein -Internet-Draft ISC -Expires: July 15, 2006 January 11, 2006 +Request for Comments: 5001 ISC +Category: Standards Track August 2007 - DNS Name Server Identifier Option (NSID) - draft-ietf-dnsext-nsid-01 + DNS Name Server Identifier (NSID) Option -Status of this Memo +Status of This Memo - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on July 15, 2006. + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. Copyright Notice - Copyright (C) The Internet Society (2006). + Copyright (C) The IETF Trust (2007). Abstract @@ -44,74 +29,57 @@ Abstract mechanisms allowing more than one DNS name server to share a single IP address, it is sometimes difficult to tell which of a pool of name servers has answered a particular query. While existing ad-hoc - mechanism allow an operator to send follow-up queries when it is + mechanisms allow an operator to send follow-up queries when it is necessary to debug such a configuration, the only completely reliable - way to obtain the identity of the name server which responded is to + way to obtain the identity of the name server that responded is to have the name server include this information in the response itself. This note defines a protocol extension to support this functionality. -Austein Expires July 15, 2006 [Page 1] + + + + + + + + + + + + + + + + + + +Austein Standards Track [Page 1] -Internet-Draft DNS NSID January 2006 +RFC 5001 DNS NSID August 2007 Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Reserved Words . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2.1. Resolver Behavior . . . . . . . . . . . . . . . . . . . . 4 - 2.2. Name Server Behavior . . . . . . . . . . . . . . . . . . . 4 + 2. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2.1. Resolver Behavior . . . . . . . . . . . . . . . . . . . . 3 + 2.2. Name Server Behavior . . . . . . . . . . . . . . . . . . . 3 2.3. The NSID Option . . . . . . . . . . . . . . . . . . . . . 4 - 2.4. Presentation Format . . . . . . . . . . . . . . . . . . . 5 - 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 3.1. The NSID Payload . . . . . . . . . . . . . . . . . . . . . 6 - 3.2. NSID Is Not Transitive . . . . . . . . . . . . . . . . . . 8 - 3.3. User Interface Issues . . . . . . . . . . . . . . . . . . 8 - 3.4. Truncation . . . . . . . . . . . . . . . . . . . . . . . . 9 - 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 - 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 - 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 - 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 7.1. Normative References . . . . . . . . . . . . . . . . . . . 13 - 7.2. Informative References . . . . . . . . . . . . . . . . . . 13 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14 - Intellectual Property and Copyright Statements . . . . . . . . . . 15 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 2] - -Internet-Draft DNS NSID January 2006 - + 2.4. Presentation Format . . . . . . . . . . . . . . . . . . . 4 + 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3.1. The NSID Payload . . . . . . . . . . . . . . . . . . . . . 4 + 3.2. NSID Is Not Transitive . . . . . . . . . . . . . . . . . . 7 + 3.3. User Interface Issues . . . . . . . . . . . . . . . . . . 7 + 3.4. Truncation . . . . . . . . . . . . . . . . . . . . . . . . 8 + 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 + 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 + 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 + 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 + 7.2. Informative References . . . . . . . . . . . . . . . . . . 10 1. Introduction @@ -131,10 +99,22 @@ Internet-Draft DNS NSID January 2006 Given that a DNS query is an idempotent operation with no retained state, it would appear that the only completely reliable way to - obtain the identity of the name server which responded to a - particular query is to have that name server include identifying - information in the response itself. This note defines a protocol - enhancement to achieve this. + obtain the identity of the name server that responded to a particular + query is to have that name server include identifying information in + the response itself. This note defines a protocol enhancement to + achieve this. + + + + + + + + +Austein Standards Track [Page 2] + +RFC 5001 DNS NSID August 2007 + 1.1. Reserved Words @@ -142,33 +122,6 @@ Internet-Draft DNS NSID January 2006 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 3] - -Internet-Draft DNS NSID January 2006 - - 2. Protocol This note uses an EDNS [RFC2671] option to signal the resolver's @@ -195,10 +148,10 @@ Internet-Draft DNS NSID January 2006 2.2. Name Server Behavior - A name server which understands the NSID option and chooses to honor - a particular NSID request responds by including identifying - information in a NSID option (Section 2.3) in an EDNS OPT pseudo-RR - in the response message. + A name server that understands the NSID option and chooses to honor a + particular NSID request responds by including identifying information + in a NSID option (Section 2.3) in an EDNS OPT pseudo-RR in the + response message. The name server MUST ignore any NSID payload data that might be present in the query message. @@ -210,29 +163,31 @@ Internet-Draft DNS NSID January 2006 absence of the NSID option in the recursive name server's response to the original client. + + + + +Austein Standards Track [Page 3] + +RFC 5001 DNS NSID August 2007 + + As stated in Section 2.1, this mechanism is not restricted to authoritative name servers; the semantics are intended to be equally applicable to recursive name servers. 2.3. The NSID Option - The OPTION-CODE for the NSID option is [TBD]. + The OPTION-CODE for the NSID option is 3. - - -Austein Expires July 15, 2006 [Page 4] - -Internet-Draft DNS NSID January 2006 - - - The OPTION-DATA for the NSID option is an opaque byte string the + The OPTION-DATA for the NSID option is an opaque byte string, the semantics of which are deliberately left outside the protocol. See Section 3.1 for discussion. 2.4. Presentation Format - User interfaces MUST read and write the content of the NSID option as - a sequence of hexadecimal digits, two digits per payload octet. + User interfaces MUST read and write the contents of the NSID option + as a sequence of hexadecimal digits, two digits per payload octet. The NSID payload is binary data. Any comparison between NSID payloads MUST be a comparison of the raw binary data. Copy @@ -243,44 +198,6 @@ Internet-Draft DNS NSID January 2006 See Section 3.3 for discussion. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 5] - -Internet-Draft DNS NSID January 2006 - - 3. Discussion This section discusses certain aspects of the protocol and explains @@ -288,11 +205,28 @@ Internet-Draft DNS NSID January 2006 3.1. The NSID Payload - The syntax and semantics of the content of the NSID option is - deliberately left outside the scope of this specification. This - section describe some of the kinds of data that server administrators - might choose to provide as the content of the NSID option, and - explains the reasoning behind choosing a simple opaque byte string. + The syntax and semantics of the content of the NSID option are + deliberately left outside the scope of this specification. + + Choosing the NSID content is a prerogative of the server + administrator. The server administrator might choose to encode the + NSID content in such a way that the server operator (or clients + authorized by the server operator) can decode the NSID content to + obtain more information than other clients can. Alternatively, the + server operator might choose unencoded NSID content that is equally + meaningful to any client. + + This section describes some of the kinds of data that server + administrators might choose to provide as the content of the NSID + option, and explains the reasoning behind specifying a simple opaque + byte string in Section 2.3. + + + +Austein Standards Track [Page 4] + +RFC 5001 DNS NSID August 2007 + There are several possibilities for the payload of the NSID option: @@ -306,11 +240,11 @@ Internet-Draft DNS NSID January 2006 predictable fashion somehow using the server's IP address or name as a seed value. - o It could be some sort of probabilisticly unique identifier + o It could be some sort of probabilistically unique identifier initially derived from some sort of random number generator then preserved across reboots of the name server. - o It could be some sort of dynamicly generated identifier so that + o It could be some sort of dynamically generated identifier so that only the name server operator could tell whether or not any two queries had been answered by the same server. @@ -329,14 +263,6 @@ Internet-Draft DNS NSID January 2006 o Using the "real" name is simple, but the name server may not have a "real" name. - - - -Austein Expires July 15, 2006 [Page 6] - -Internet-Draft DNS NSID January 2006 - - o Using the "real" address is also simple, and the name server almost certainly does have at least one non-anycast IP address for maintenance operations, but the operator of the name server may @@ -350,6 +276,14 @@ Internet-Draft DNS NSID January 2006 o Using a hash or pseudo-random number can provide a fixed length value that the resolver can use to tell two name servers apart + + + +Austein Standards Track [Page 5] + +RFC 5001 DNS NSID August 2007 + + without necessarily being able to tell where either one of them "really" is, but makes debugging more difficult if one happens to be in a friendly open environment. Furthermore, hashing might not @@ -358,43 +292,59 @@ Internet-Draft DNS NSID January 2006 that operators might have to debug at 4am tend not to be very random. - o Probabilisticly unique identifiers have similar properties to + o Probabilistically unique identifiers have properties similar to hashed identifiers, but (given a sufficiently good random number generator) are immune to the search space issues. However, the strength of this approach is also its weakness: there is no algorithmic transformation by which even the server operator can associate name server instances with identifiers while debugging, which might be annoying. This approach also requires the name - server instance to preserve the probabilisticly unique identifier - across reboots, but this does not appear to be a serious - restriction, since authoritative nameservers almost always have - some form of nonvolatile storage in any case, and in the rare case - of a name server that does not have any way to store such an - identifier, nothing terrible will happen if the name server just + server instance to preserve the probabilistically unique + identifier across reboots, but this does not appear to be a + serious restriction, since authoritative nameservers almost always + have some form of non-volatile storage. In the rare case of a + name server that does not have any way to store such an + identifier, nothing terrible will happen if the name server generates a new identifier every time it reboots. o Using an arbitrary octet string gives name server operators yet - another thing to configure, or mis-configure, or forget to + another setting to configure, or mis-configure, or forget to configure. Having all the nodes in an anycast name server constellation identify themselves as "My Name Server" would not be particularly useful. + o A signed blob is not particularly useful as an NSID payload unless + the signed data is dynamic and includes some kind of replay + protection, such as a timestamp or some kind of data identifying + the requestor. Signed blobs that meet these criteria could + conceivably be useful in some situations but would require + detailed security analysis beyond the scope of this document. + + o A static encrypted blob would not be particularly useful, as it + would be subject to replay attacks and would, in effect, just be a + random number to any party that does not possess the decryption + key. Dynamic encrypted blobs could conceivably be useful in some + situations but, as with signed blobs, dynamic encrypted blobs + would require detailed security analysis beyond the scope of this + document. + Given all of the issues listed above, there does not appear to be a single solution that will meet all needs. Section 2.3 therefore defines the NSID payload to be an opaque byte string and leaves the - choice up to the implementor and name server operator. The following - guidelines may be useful to implementors and server operators: + choice of payload up to the implementor and name server operator. - -Austein Expires July 15, 2006 [Page 7] +Austein Standards Track [Page 6] -Internet-Draft DNS NSID January 2006 +RFC 5001 DNS NSID August 2007 + The following guidelines may be useful to implementors and server + operators: + o Operators for whom divulging the unicast address is an issue could - use the raw binary representation of a probabilisticly unique + use the raw binary representation of a probabilistically unique random number. This should probably be the default implementation behavior. @@ -438,17 +388,17 @@ Internet-Draft DNS NSID January 2006 Given the range of possible payload contents described in Section 3.1, it is not possible to define a single presentation format for the NSID payload that is efficient, convenient, + + + +Austein Standards Track [Page 7] + +RFC 5001 DNS NSID August 2007 + + unambiguous, and aesthetically pleasing. In particular, while it is tempting to use a presentation format that uses some form of textual strings, attempting to support this would significantly complicate - - - -Austein Expires July 15, 2006 [Page 8] - -Internet-Draft DNS NSID January 2006 - - what's intended to be a very simple debugging mechanism. In some cases the content of the NSID payload may be binary data @@ -468,7 +418,7 @@ Internet-Draft DNS NSID January 2006 It is much more important for the NSID payload data to be passed unambiguously from server administrator to user and back again than - it is for the payload data data to be pretty while in transit. In + it is for the payload data to be pretty while in transit. In particular, it's critical that it be straightforward for a user to cut and paste an exact copy of the NSID payload output by a debugging tool into other formats such as email messages or web forms without @@ -490,82 +440,23 @@ Internet-Draft DNS NSID January 2006 "sender's UDP payload size" field of the OPT pseudo-RR to signal a receive buffer size large enough to make truncation unlikely. - - - - - - - - - - -Austein Expires July 15, 2006 [Page 9] - -Internet-Draft DNS NSID January 2006 - - 4. IANA Considerations - This mechanism requires allocation of one ENDS option code for the - NSID option (Section 2.3). + IANA has allocated EDNS option code 3 for the NSID option + (Section 2.3). - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 10] +Austein Standards Track [Page 8] -Internet-Draft DNS NSID January 2006 +RFC 5001 DNS NSID August 2007 5. Security Considerations - This document describes a channel signaling mechanism, intended + This document describes a channel signaling mechanism intended primarily for debugging. Channel signaling mechanisms are outside - the scope of DNSSEC per se. Applications that require integrity + the scope of DNSSEC, per se. Applications that require integrity protection for the data being signaled will need to use a channel security mechanism such as TSIG [RFC2845]. @@ -576,102 +467,26 @@ Internet-Draft DNS NSID January 2006 leaves the syntax and semantics of the NSID option content up to the implementation and the name server operator. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 11] - -Internet-Draft DNS NSID January 2006 - + Two of the possible kinds of payload data discussed in Section 3.1 + involve a digital signature and encryption, respectively. While this + specification discusses some of the pitfalls that might lurk for + careless users of these kinds of payload data, full analysis of the + issues that would be involved in these kinds of payload data would + require knowledge of the content to be signed or encrypted, + algorithms to be used, and so forth, which is beyond the scope of + this document. Implementors should seek competent advice before + attempting to use these kinds of NSID payloads. 6. Acknowledgements - Joe Abley, Harald Alvestrand, Mark Andrews, Roy Arends, Steve - Bellovin, Randy Bush, David Conrad, Johan Ihren, Daniel Karrenberg, - Peter Koch, Mike Patton, Mike StJohns, Paul Vixie, Sam Weiler, and - Suzanne Woolf. Apologies to anyone inadvertently omitted from the - above list. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 12] - -Internet-Draft DNS NSID January 2006 - + Thanks to: Joe Abley, Harald Alvestrand, Dean Anderson, Mark Andrews, + Roy Arends, Steve Bellovin, Alex Bligh, Randy Bush, David Conrad, + John Dickinson, Alfred Hoenes, Johan Ihren, Daniel Karrenberg, Peter + Koch, William Leibzon, Ed Lewis, Thomas Narten, Mike Patton, Geoffrey + Sisson, Andrew Sullivan, Mike StJohns, Tom Taylor, Paul Vixie, Sam + Weiler, and Suzanne Woolf, none of whom are responsible for what the + author did with their comments and suggestions. Apologies to anyone + inadvertently omitted from the above list. 7. References @@ -683,6 +498,16 @@ Internet-Draft DNS NSID January 2006 [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, August 1999. + + + + + +Austein Standards Track [Page 9] + +RFC 5001 DNS NSID August 2007 + + [RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B. Wellington, "Secret Key Transaction Authentication for DNS (TSIG)", RFC 2845, May 2000. @@ -692,43 +517,6 @@ Internet-Draft DNS NSID January 2006 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and Languages", RFC 2277, BCP 18, January 1998. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Austein Expires July 15, 2006 [Page 13] - -Internet-Draft DNS NSID January 2006 - - Author's Address Rob Austein @@ -737,7 +525,7 @@ Author's Address Redwood City, CA 94063 USA - Email: sra@isc.org + EMail: sra@isc.org @@ -771,21 +559,28 @@ Author's Address - - - - - - - - - -Austein Expires July 15, 2006 [Page 14] +Austein Standards Track [Page 10] -Internet-Draft DNS NSID January 2006 +RFC 5001 DNS NSID August 2007 -Intellectual Property Statement +Full Copyright Statement + + Copyright (C) The IETF Trust (2007). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND + THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS + OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF + THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to @@ -809,26 +604,7 @@ Intellectual Property Statement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. - -Disclaimer of Validity - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Copyright Statement - - Copyright (C) The Internet Society (2006). This document is subject - to the rights, licenses and restrictions contained in BCP 78, and - except as set forth therein, the authors retain all their rights. - - -Acknowledgment +Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. @@ -836,5 +612,8 @@ Acknowledgment -Austein Expires July 15, 2006 [Page 15] + + + +Austein Standards Track [Page 11] diff --git a/doc/rfc/rfc5452.txt b/doc/rfc/rfc5452.txt new file mode 100644 index 0000000000..6f59bf57ac --- /dev/null +++ b/doc/rfc/rfc5452.txt @@ -0,0 +1,1011 @@ + + + + + + +Network Working Group A. Hubert +Request for Comments: 5452 Netherlabs Computer Consulting BV. +Updates: 2181 R. van Mook +Category: Standards Track Equinix + January 2009 + + + Measures for Making DNS More Resilient against Forged Answers + +Status of This Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (c) 2009 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents (http://trustee.ietf.org/ + license-info) in effect on the date of publication of this document. + Please review these documents carefully, as they describe your rights + and restrictions with respect to this document. + +Abstract + + The current Internet climate poses serious threats to the Domain Name + System. In the interim period before the DNS protocol can be secured + more fully, measures can already be taken to harden the DNS to make + 'spoofing' a recursing nameserver many orders of magnitude harder. + + Even a cryptographically secured DNS benefits from having the ability + to discard bogus responses quickly, as this potentially saves large + amounts of computation. + + By describing certain behavior that has previously not been + standardized, this document sets out how to make the DNS more + resilient against accepting incorrect responses. This document + updates RFC 2181. + + + + + + + + +Hubert & van Mook Standards Track [Page 1] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Requirements and Definitions . . . . . . . . . . . . . . . . . 4 + 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4 + 2.2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 5 + 3. Description of DNS Spoofing . . . . . . . . . . . . . . . . . 5 + 4. Detailed Description of Spoofing Scenarios . . . . . . . . . . 6 + 4.1. Forcing a Query . . . . . . . . . . . . . . . . . . . . . 6 + 4.2. Matching the Question Section . . . . . . . . . . . . . . 7 + 4.3. Matching the ID Field . . . . . . . . . . . . . . . . . . 7 + 4.4. Matching the Source Address of the Authentic Response . . 7 + 4.5. Matching the Destination Address and Port of the + Authentic Response . . . . . . . . . . . . . . . . . . . . 8 + 4.6. Have the Response Arrive before the Authentic Response . . 8 + 5. Birthday Attacks . . . . . . . . . . . . . . . . . . . . . . . 9 + 6. Accepting Only In-Domain Records . . . . . . . . . . . . . . . 9 + 7. Combined Difficulty . . . . . . . . . . . . . . . . . . . . . 10 + 7.1. Symbols Used in Calculation . . . . . . . . . . . . . . . 10 + 7.2. Calculation . . . . . . . . . . . . . . . . . . . . . . . 11 + 8. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 8.1. Repetitive Spoofing Attempts for a Single Domain Name . . 13 + 9. Forgery Countermeasures . . . . . . . . . . . . . . . . . . . 13 + 9.1. Query Matching Rules . . . . . . . . . . . . . . . . . . . 13 + 9.2. Extending the Q-ID Space by Using Ports and Addresses . . 14 + 9.2.1. Justification and Discussion . . . . . . . . . . . . . 14 + 9.3. Spoof Detection and Countermeasure . . . . . . . . . . . . 15 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 + 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 12.1. Normative References . . . . . . . . . . . . . . . . . . . 16 + 12.2. Informative References . . . . . . . . . . . . . . . . . . 17 + + + + + + + + + + + + + + + + + + + +Hubert & van Mook Standards Track [Page 2] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + +1. Introduction + + This document describes several common problems in DNS + implementations, which, although previously recognized, remain + largely unsolved. Besides briefly recapping these problems, this + document contains rules that, if implemented, make complying + resolvers vastly more resistant to the attacks described. The goal + is to make the existing DNS as secure as possible within the current + protocol boundaries. + + The words below are aimed at authors of resolvers: it is up to + operators to decide which nameserver implementation to use, or which + options to enable. Operational constraints may override the security + concerns described below. However, implementations are expected to + allow an operator to enable functionality described in this document. + + Almost every transaction on the Internet involves the Domain Name + System, which is described in [RFC1034], [RFC1035], and beyond. + + Additionally, it has recently become possible to acquire Secure + Socket Layer/Transport Layer Security (SSL/TLS) certificates with no + other confirmation of identity than the ability to respond to a + verification email sent via SMTP ([RFC5321]) -- which generally uses + DNS for its routing. + + In other words, any party that (temporarily) controls the Domain Name + System is in a position to reroute most kinds of Internet + transactions, including the verification steps in acquiring an SSL/ + TLS certificate for a domain. This in turn means that even + transactions protected by SSL/TLS could be diverted. + + It is entirely conceivable that such rerouted traffic could be used + to the disadvantage of Internet users. + + These and other developments have made the security and + trustworthiness of DNS of renewed importance. Although the DNS + community is working hard on finalizing and implementing a + cryptographically enhanced DNS protocol, steps should be taken to + make sure that the existing use of DNS is as secure as possible + within the bounds of the relevant standards. + + It should be noted that the most commonly used resolvers currently do + not perform as well as possible in this respect, making this document + of urgent importance. + + A thorough analysis of risks facing DNS can be found in [RFC3833]. + + + + + +Hubert & van Mook Standards Track [Page 3] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + This document expands on some of the risks mentioned in RFC 3833, + especially those outlined in the sections on "ID Guessing and Query + Prediction" and "Name Chaining". Furthermore, it emphasizes a number + of existing rules and guidelines embodied in the relevant DNS + protocol specifications. The following also specifies new + requirements to make sure the Domain Name System can be relied upon + until a more secure protocol has been standardized and deployed. + + It should be noted that even when all measures suggested below are + implemented, protocol users are not protected against third parties + with the ability to observe, modify, or inject packets in the traffic + of a resolver. + + For protocol extensions that offer protection against these + scenarios, see [RFC4033] and beyond. + +2. Requirements and Definitions + +2.1. Definitions + + This document uses the following definitions: + + Client: typically a 'stub-resolver' on an end-user's computer. + + Resolver: a nameserver performing recursive service for clients, + also known as a caching server, or a full service resolver + ([RFC1123], Section 6.1.3.1). + + Stub resolver: a very limited resolver on a client computer, that + leaves the recursing work to a full resolver. + + Query: a question sent out by a resolver, typically in a UDP + packet + + Response: the answer sent back by an authoritative nameserver, + typically in a UDP packet. + + Third party: any entity other than the resolver or the intended + recipient of a question. The third party may have access to an + arbitrary authoritative nameserver, but has no access to packets + transmitted by the resolver or authoritative server. + + Attacker: malicious third party. + + Spoof: the activity of attempting to subvert the DNS process by + getting a chosen answer accepted. + + + + + +Hubert & van Mook Standards Track [Page 4] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + Authentic response: the correct answer that comes from the right + authoritative server. + + Target domain name: domain for which the attacker wishes to spoof + in an answer + + Fake data: response chosen by the attacker. + +2.2. Key Words + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in [RFC2119]. + +3. Description of DNS Spoofing + + When certain steps are taken, it is feasible to "spoof" the current + deployed majority of resolvers with carefully crafted and timed DNS + packets. Once spoofed, a caching server will repeat the data it + wrongfully accepted, and make its clients contact the wrong, and + possibly malicious, servers. + + To understand how this process works it is important to know what + makes a resolver accept a response. + + The following sentence in Section 5.3.3 of [RFC1034] presaged the + present problem: + + The resolver should be highly paranoid in its parsing of responses. + It should also check that the response matches the query it sent + using the ID field in the response. + + DNS data is to be accepted by a resolver if and only if: + + 1. The question section of the reply packet is equivalent to that of + a question packet currently waiting for a response. + + 2. The ID field of the reply packet matches that of the question + packet. + + 3. The response comes from the same network address to which the + question was sent. + + 4. The response comes in on the same network address, including port + number, from which the question was sent. + + In general, the first response matching these four conditions is + accepted. + + + +Hubert & van Mook Standards Track [Page 5] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + If a third party succeeds in meeting the four conditions before the + response from the authentic nameserver does so, it is in a position + to feed a resolver fabricated data. When it does so, we dub it an + "attacker", attempting to spoof in fake data. + + All conditions mentioned above can theoretically be met by a third + party, with the difficulty being a function of the resolver + implementation and zone configuration. + +4. Detailed Description of Spoofing Scenarios + + The previous paragraph discussed a number of requirements an attacker + must match in order to spoof in manipulated (or fake) data. This + section discusses the relative difficulties and how implementation- + defined choices impact the amount of work an attacker has to perform + to meet said difficulties. + + Some more details can be found in Section 2.2 of [RFC3833]. + +4.1. Forcing a Query + + Formally, there is no need for a nameserver to perform service except + for its operator, its customers, or more generally its users. + Recently, open recursing nameservers have been used to amplify + denial-of-service attacks. + + Providing full service enables the third party to send the target + resolver a query for the domain name it intends to spoof. On + receiving this query, and not finding the answer in its cache, the + resolver will transmit queries to relevant authoritative nameservers. + This opens up a window of opportunity for getting fake answer data + accepted. + + Queries may however be forced indirectly, for example, by inducing a + mail server to perform DNS lookups. + + Some operators restrict access by not recursing for unauthorized IP + addresses, but only respond with data from the cache. This makes + spoofing harder for a third party as it cannot then force the exact + moment a question will be asked. It is still possible however to + determine a time range when this will happen, because nameservers + helpfully publish the decreasing time to live (TTL) of entries in the + cache, which indicate from which absolute time onwards a new query + could be sent to refresh the expired entry. + + The time to live of the target domain name's RRSets determines how + often a window of opportunity is available, which implies that a + short TTL makes spoofing far more viable. + + + +Hubert & van Mook Standards Track [Page 6] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + Note that the attacker might very well have authorized access to the + target resolver by virtue of being a customer or employee of its + operator. In addition, access may be enabled through the use of + reflectors as outlined in [RFC5358]. + +4.2. Matching the Question Section + + DNS packets, both queries and responses, contain a question section. + Incoming responses should be verified to have a question section that + is equivalent to that of the outgoing query. + +4.3. Matching the ID Field + + The DNS ID field is 16 bits wide, meaning that if full use is made of + all these bits, and if their contents are truly random, it will + require on average 32768 attempts to guess. Anecdotal evidence + suggests there are implementations utilizing only 14 bits, meaning on + average 8192 attempts will suffice. + + Additionally, if the target nameserver can be forced into having + multiple identical queries outstanding, the "Birthday Attack" + phenomenon means that any fake data sent by the attacker is matched + against multiple outstanding queries, significantly raising the + chance of success. Further details in Section 5. + +4.4. Matching the Source Address of the Authentic Response + + It should be noted that meeting this condition entails being able to + transmit packets on behalf of the address of the authoritative + nameserver. While two Best Current Practice documents ([RFC2827] and + [RFC3013] specifically) direct Internet access providers to prevent + their customers from assuming IP addresses that are not assigned to + them, these recommendations are not universally (nor even widely) + implemented. + + Many zones have two or three authoritative nameservers, which make + matching the source address of the authentic response very likely + with even a naive choice having a double digit success rate. + + Most recursing nameservers store relative performance indications of + authoritative nameservers, which may make it easier to predict which + nameserver would originally be queried -- the one most likely to + respond the quickest. + + Generally, this condition requires at most two or three attempts + before it is matched. + + + + + +Hubert & van Mook Standards Track [Page 7] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + +4.5. Matching the Destination Address and Port of the Authentic + Response + + Note that the destination address of the authentic response is the + source address of the original query. + + The actual address of a recursing nameserver is generally known; the + port used for asking questions is harder to determine. Most current + resolvers pick an arbitrary port at startup (possibly at random) and + use this for all outgoing queries. In quite a number of cases, the + source port of outgoing questions is fixed at the traditional DNS + assigned server port number of 53. + + If the source port of the original query is random, but static, any + authoritative nameserver under observation by the attacker can be + used to determine this port. This means that matching this + conditions often requires no guess work. + + If multiple ports are used for sending queries, this enlarges the + effective ID space by a factor equal to the number of ports used. + + Less common resolving servers choose a random port per outgoing + query. If this strategy is followed, this port number can be + regarded as an additional ID field, again containing up to 16 bits. + + If the maximum ports range is utilized, on average, around 32256 + source ports would have to be tried before matching the source port + of the original query, as ports below 1024 may be unavailable for + use, leaving 64512 options. + + It is in general safe for DNS to use ports in the range 1024-49152 + even though some of these ports are allocated to other protocols. + DNS resolvers will not be able to use any ports that are already in + use. If a DNS resolver uses a port, it will release that port after + a short time and migrate to a different port. Only in the case of a + high-volume resolver is it possible that an application wanting a + particular UDP port suffers a long term block-out. + + It should be noted that a firewall will not prevent the matching of + this address, as it will accept answers that (appear to) come from + the correct address, offering no additional security. + +4.6. Have the Response Arrive before the Authentic Response + + Once any packet has matched the previous four conditions (plus + possible additional conditions), no further responses are generally + accepted. + + + + +Hubert & van Mook Standards Track [Page 8] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + This means that the third party has a limited time in which to inject + its spoofed response. For calculations, we will assume a window in + order of at most 100 ms (depending on the network distance to the + authentic authoritative nameserver). + + This time period can be far longer if the authentic authoritative + nameservers are (briefly) overloaded by queries, perhaps by the + attacker. + +5. Birthday Attacks + + The so-called "birthday paradox" implies that a group of 23 people + suffices to have a more than even chance of having two or more + members of the group share a birthday. + + An attacker can benefit from this exact phenomenon if it can force + the target resolver to have multiple equivalent (identical QNAME, + QTYPE, and QCLASS) outstanding queries at any one time to the same + authoritative server. + + Any packet the attacker sends then has a much higher chance of being + accepted because it only has to match any of the outstanding queries + for that single domain. Compared to the birthday analogy above, of + the group composed of queries and responses, the chance of having any + of these share an ID rises quickly. + + As long as small numbers of queries are sent out, the chance of + successfully spoofing a response rises linearly with the number of + outstanding queries for the exact domain and nameserver. + + For larger numbers, this effect is less pronounced. + + More details are available in US-CERT [vu-457875]. + +6. Accepting Only In-Domain Records + + Responses from authoritative nameservers often contain information + that is not part of the zone for which we deem it authoritative. As + an example, a query for the MX record of a domain might get as its + responses a mail exchanger in another domain, and additionally the IP + address of this mail exchanger. + + If accepted uncritically, the resolver stands the chance of accepting + data from an untrusted source. Care must be taken to only accept + data if it is known that the originator is authoritative for the + QNAME or a parent of the QNAME. + + + + + +Hubert & van Mook Standards Track [Page 9] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + One very simple way to achieve this is to only accept data if it is + part of the domain for which the query was intended. + +7. Combined Difficulty + + Given a known or static destination port, matching ID field, the + source and destination address requires on average in the order of 2 + * 2^15 = 65000 packets, assuming a zone has 2 authoritative + nameservers. + + If the window of opportunity available is around 100 ms, as assumed + above, an attacker would need to be able to briefly transmit 650000 + packets/s to have a 50% chance to get spoofed data accepted on the + first attempt. + + A realistic minimal DNS response consists of around 80 bytes, + including IP headers, making the packet rate above correspond to a + respectable burst of 416 Mbit/s. + + As of mid-2006, this kind of bandwidth was not common but not scarce + either, especially among those in a position to control many servers. + + These numbers change when a window of a full second is assumed, + possibly because the arrival of the authentic response can be + prevented by overloading the bona fide authoritative hosts with decoy + queries. This reduces the needed bandwidth to 42 Mbit/s. + + If, in addition, the attacker is granted more than a single chance + and allowed up to 60 minutes of work on a domain with a time to live + of 300 seconds, a meager 4 Mbit/s suffices for a 50% chance at + getting fake data accepted. Once equipped with a longer time, + matching condition 1 mentioned above is straightforward -- any + popular domain will have been queried a number of times within this + hour, and given the short TTL, this would lead to queries to + authoritative nameservers, opening windows of opportunity. + +7.1. Symbols Used in Calculation + + Assume the following symbols are used: + + I: Number distinct IDs available (maximum 65536) + + P: Number of ports used (maximum around 64000 as ports under 1024 are + not always available, but often 1) + + N: Number of authoritative nameservers for a domain (averages around + 2.5) + + + + +Hubert & van Mook Standards Track [Page 10] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + F: Number of "fake" packets sent by the attacker + + R: Number of packets sent per second by the attacker + + W: Window of opportunity, in seconds. Bounded by the response time + of the authoritative servers (often 0.1s) + + D: Average number of identical outstanding queries of a resolver + (typically 1, see Section 5) + + A: Number of attempts, one for each window of opportunity + +7.2. Calculation + + The probability of spoofing a resolver is equal to the amount of fake + packets that arrive within the window of opportunity, divided by the + size of the problem space. + + When the resolver has 'D' multiple identical outstanding queries, + each fake packet has a proportionally higher chance of matching any + of these queries. This assumption only holds for small values of + 'D'. + + In symbols, if the probability of being spoofed is denoted as P_s: + + D * F + P_s = --------- + N * P * I + + It is more useful to reason not in terms of aggregate packets but to + convert to packet rate, which can easily be converted to bandwidth if + needed. + + If the window of opportunity length is 'W' and the attacker can send + 'R' packets per second, the number of fake packets 'F' that are + candidates to be accepted is: + + D * R * W + F = R * W -> P_s = --------- + N * P * I + + Finally, to calculate the combined chance 'P_cs' of spoofing over a + chosen time period 'T', it should be realized that the attacker has a + new window of opportunity each time the TTL 'TTL' of the target + domain expires. This means that the number of attempts 'A' is equal + to 'T / TTL'. + + + + + +Hubert & van Mook Standards Track [Page 11] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + To calculate the combined chance of at least one success, the + following formula holds: + + (T / TTL) + A ( D * R * W ) + P_cs = 1 - ( 1 - P_s ) = 1 - ( 1 - --------- ) + ( N * P * I ) + + When common numbers (as listed above) for D, W, N, P, and I are + inserted, this formula reduces to: + + (T / TTL) + ( R ) + P_cs = 1 - ( 1 - ------- ) + ( 1638400 ) + + From this formula, it can be seen that, if the nameserver + implementation is unchanged, only raising the TTL offers protection. + Raising N, the number of authoritative nameservers, is not feasible + beyond a small number. + + For the degenerate case of a zero-second TTL, a window of opportunity + opens for each query sent, making the effective TTL equal to 'W' + above, the response time of the authoritative server. + + This last case also holds for spoofing techniques that do not rely on + TTL expiry, but use repeated and changing queries. + +8. Discussion + + The calculations above indicate the relative ease with which DNS data + can be spoofed. For example, using the formula derived earlier on an + RRSet with a 3600 second TTL, an attacker sending 7000 fake response + packets/s (a rate of 4.5 Mbit/s), stands a 10% chance of spoofing a + record in the first 24 hours, which rises to 50% after a week. + + For an RRSet with a TTL of 60 seconds, the 10% level is hit after 24 + minutes, 50% after less than 3 hours, 90% after around 9 hours. + + For some classes of attacks, the effective TTL is near zero, as noted + above. + + Note that the attacks mentioned above can be detected by watchful + server operators - an unexpected incoming stream of 4.5 Mbit/s of + packets might be noticed. + + An important assumption however in these calculations is a known or + static destination port of the authentic response. + + + +Hubert & van Mook Standards Track [Page 12] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + If that port number is unknown and needs to be guessed as well, the + problem space expands by a factor of 64000, leading the attacker to + need in excess of 285Gb/s to achieve similar success rates. + + Such bandwidth is not generally available, nor is it expected to be + so in the foreseeable future. + + Note that some firewalls may need reconfiguring if they are currently + set up to only allow outgoing queries from a single DNS source port. + +8.1. Repetitive Spoofing Attempts for a Single Domain Name + + Techniques are available to use an effectively infinite number of + queries to achieve a desired spoofing goal. In the math above, this + reduces the effective TTL to 0. + + If such techniques are employed, using the same 7000 packets/s rate + mentioned above, and using 1 source port, the spoofing chance rises + to 50% within 7 seconds. + + If 64000 ports are used, as recommended in this document, using the + same query rate, the 50% level is reached after around 116 hours. + +9. Forgery Countermeasures + +9.1. Query Matching Rules + + A resolver implementation MUST match responses to all of the + following attributes of the query: + + o Source address against query destination address + + o Destination address against query source address + + o Destination port against query source port + + o Query ID + + o Query name + + o Query class and type + + before applying DNS trustworthiness rules (see Section 5.4.1 of + [RFC2181]). + + A mismatch and the response MUST be considered invalid. + + + + + +Hubert & van Mook Standards Track [Page 13] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + +9.2. Extending the Q-ID Space by Using Ports and Addresses + + Resolver implementations MUST: + + o Use an unpredictable source port for outgoing queries from the + range of available ports (53, or 1024 and above) that is as large + as possible and practicable; + + o Use multiple different source ports simultaneously in case of + multiple outstanding queries; + + o Use an unpredictable query ID for outgoing queries, utilizing the + full range available (0-65535). + + Resolvers that have multiple IP addresses SHOULD use them in an + unpredictable manner for outgoing queries. + + Resolver implementations SHOULD provide means to avoid usage of + certain ports. + + Resolvers SHOULD favor authoritative nameservers with which a trust + relation has been established; stub-resolvers SHOULD be able to use + Transaction Signature (TSIG) ([RFC2845]) or IPsec ([RFC4301]) when + communicating with their recursive resolver. + + In case a cryptographic verification of response validity is + available (TSIG, SIG(0)), resolver implementations MAY waive above + rules, and rely on this guarantee instead. + + Proper unpredictability can be achieved by employing a high quality + (pseudo-)random generator, as described in [RFC4086]. + +9.2.1. Justification and Discussion + + Since an attacker can force a full DNS resolver to send queries to + the attacker's own nameservers, any constant or sequential state held + by such a resolver can be measured, and it must not be trivially easy + to reverse engineer the resolver's internal state in a way that + allows low-cost, high-accuracy prediction of future state. + + A full DNS resolver with only one or a small number of upstream- + facing endpoints is effectively using constants for IP source address + and UDP port number, and these are very predictable by potential + attackers, and must therefore be avoided. + + A full DNS resolver that uses a simple increment to get its next DNS + query ID is likewise very predictable and so very spoofable. + + + + +Hubert & van Mook Standards Track [Page 14] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + Finally, weak random number generators have been shown to expose + their internal state, such that an attacker who witnesses several + sequential "random" values can easily predict the next ones. A + crypto-strength random number generator is one whose output cannot be + predicted no matter how many successive values are witnessed. + +9.3. Spoof Detection and Countermeasure + + If a resolver detects that an attempt is being made to spoof it, + perhaps by discovering that many packets fail the criteria as + outlined above, it MAY abandon the UDP query and re-issue it over + TCP. TCP, by the nature of its use of sequence numbers, is far more + resilient against forgery by third parties. + +10. Security Considerations + + This document provides clarification of the DNS specification to + decrease the probability that DNS responses can be successfully + forged. Recommendations found above should be considered + complementary to possible cryptographical enhancements of the domain + name system, which protect against a larger class of attacks. + + This document recommends the use of UDP source port number + randomization to extend the effective DNS transaction ID beyond the + available 16 bits. + + A resolver that does not implement the recommendations outlined above + can easily be forced to accept spoofed responses, which in turn are + passed on to client computers -- misdirecting (user) traffic to + possibly malicious entities. + + This document directly impacts the security of the Domain Name + System, implementers are urged to follow its recommendations. + + Most security considerations can be found in Sections 4 and 5, while + proposed countermeasures are described in Section 9. + + For brevity's sake, in lieu of repeating the security considerations + references, the reader is referred to these sections. + + Nothing in this document specifies specific algorithms for operators + to use; it does specify algorithms implementations SHOULD or MUST + support. + + It should be noted that the effects of source port randomization may + be dramatically reduced by NAT devices that either serialize or limit + in volume the UDP source ports used by the querying resolver. + + + + +Hubert & van Mook Standards Track [Page 15] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + DNS recursive servers sitting behind at NAT or a statefull firewall + may consume all available NAT translation entries/ports when + operating under high query load. Port randomization will cause + translation entries to be consumed faster than with fixed query port. + + To avoid this, NAT boxes and statefull firewalls can/should purge + outgoing DNS query translation entries 10-17 seconds after the last + outgoing query on that mapping was sent. [RFC4787]-compliant devices + need to treat UDP messages with port 53 differently than most other + UDP protocols. + + To minimize the potential that port/state exhaustion attacks can be + staged from the outside, it is recommended that services that + generate a number of DNS queries for each connection should be rate + limited. This applies in particular to email servers. + +11. Acknowledgments + + Source port randomization in DNS was first implemented and possibly + invented by Dan J. Bernstein. + + Although any mistakes remain our own, the authors gratefully + acknowledge the help and contributions of: + Stephane Bortzmeyer + Alfred Hoenes + Peter Koch + Sean Leach + Norbert Sendetzky + Paul Vixie + Florian Weimer + Wouter Wijngaards + Dan Wing + +12. References + +12.1. Normative References + + [RFC1034] Mockapetris, P., "Domain names - concepts and + facilities", STD 13, RFC 1034, November 1987. + + [RFC1035] Mockapetris, P., "Domain names - implementation and + specification", STD 13, RFC 1035, November 1987. + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS + Specification", RFC 2181, July 1997. + + + +Hubert & van Mook Standards Track [Page 16] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + + [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: + Defeating Denial of Service Attacks which employ IP + Source Address Spoofing", BCP 38, RFC 2827, May 2000. + + [RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D., and B. + Wellington, "Secret Key Transaction Authentication for + DNS (TSIG)", RFC 2845, May 2000. + + [RFC3013] Killalea, T., "Recommended Internet Service Provider + Security Services and Procedures", BCP 46, RFC 3013, + November 2000. + + [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. + Rose, "DNS Security Introduction and Requirements", + RFC 4033, March 2005. + + [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness + Requirements for Security", BCP 106, RFC 4086, + June 2005. + + [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, + October 2008. + +12.2. Informative References + + [RFC1123] Braden, R., "Requirements for Internet Hosts - + Application and Support", STD 3, RFC 1123, October 1989. + + [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the + Domain Name System (DNS)", RFC 3833, August 2004. + + [RFC4301] Kent, S. and K. Seo, "Security Architecture for the + Internet Protocol", RFC 4301, December 2005. + + [RFC4787] Audet, F. and C. Jennings, "Network Address Translation + (NAT) Behavioral Requirements for Unicast UDP", BCP 127, + RFC 4787, January 2007. + + [RFC5358] Damas, J. and F. Neves, "Preventing Use of Recursive + Nameservers in Reflector Attacks", BCP 140, RFC 5358, + October 2008. + + [vu-457875] United States CERT, "Various DNS service implementations + generate multiple simultaneous queries for the same + resource record", VU 457875, November 2002. + + + + + + +Hubert & van Mook Standards Track [Page 17] + +RFC 5452 DNS Resilience against Forged Answers January 2009 + + +Authors' Addresses + + Bert Hubert + Netherlabs Computer Consulting BV. + Braillelaan 10 + Rijswijk (ZH) 2289 CM + The Netherlands + + EMail: bert.hubert@netherlabs.nl + + + Remco van Mook + Equinix + Auke Vleerstraat 1 + Enschede 7521 PE + The Netherlands + + EMail: remco@eu.equinix.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Hubert & van Mook Standards Track [Page 18] + diff --git a/doc/draft/draft-ietf-dnsext-dnsproxy-05.txt b/doc/rfc/rfc5625.txt similarity index 55% rename from doc/draft/draft-ietf-dnsext-dnsproxy-05.txt rename to doc/rfc/rfc5625.txt index c5858c00ad..102d7e8770 100644 --- a/doc/draft/draft-ietf-dnsext-dnsproxy-05.txt +++ b/doc/rfc/rfc5625.txt @@ -1,37 +1,28 @@ -DNSEXT R. Bellis -Internet-Draft Nominet UK -Intended status: BCP April 23, 2009 -Expires: October 25, 2009 + + + +Network Working Group R. Bellis +Request for Comments: 5625 Nominet UK +BCP: 152 August 2009 +Category: Best Current Practice DNS Proxy Implementation Guidelines - draft-ietf-dnsext-dnsproxy-05 -Status of this Memo +Abstract - This Internet-Draft is submitted to IETF in full conformance with the - provisions of BCP 78 and BCP 79. + This document provides guidelines for the implementation of DNS + proxies, as found in broadband gateways and other similar network + devices. - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. +Status of This Memo - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on October 25, 2009. + This document specifies an Internet Best Current Practices for the + Internet Community, and requests discussion and suggestions for + improvements. Distribution of this memo is unlimited. Copyright Notice @@ -44,89 +35,72 @@ Copyright Notice Please review these documents carefully, as they describe your rights and restrictions with respect to this document. -Abstract - - This document provides guidelines for the implementation of DNS - proxies, as found in broadband gateways and other similar network - devices. -Bellis Expires October 25, 2009 [Page 1] + + + + + + + + + + + + + + + + + +Bellis Best Current Practice [Page 1] -Internet-Draft DNS Proxy Implementation Guidelines April 2009 +RFC 5625 DNS Proxy Implementation Guidelines August 2009 Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - - 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 - - 3. The Transparency Principle . . . . . . . . . . . . . . . . . . 3 - - 4. Protocol Conformance . . . . . . . . . . . . . . . . . . . . . 4 - 4.1. Unexpected Flags and Data . . . . . . . . . . . . . . . . 4 - 4.2. Label Compression . . . . . . . . . . . . . . . . . . . . 4 - 4.3. Unknown Resource Record Types . . . . . . . . . . . . . . 5 - 4.4. Packet Size Limits . . . . . . . . . . . . . . . . . . . . 5 - 4.4.1. TCP Transport . . . . . . . . . . . . . . . . . . . . 6 - 4.4.2. Extension Mechanisms for DNS (EDNS0) . . . . . . . . . 6 - 4.4.3. IP Fragmentation . . . . . . . . . . . . . . . . . . . 6 - 4.5. Secret Key Transaction Authentication for DNS (TSIG) . . . 7 - - 5. DHCP's Interaction with DNS . . . . . . . . . . . . . . . . . 7 - 5.1. Domain Name Server (DHCP Option 6) . . . . . . . . . . . . 8 - 5.2. Domain Name (DHCP Option 15) . . . . . . . . . . . . . . . 8 - 5.3. DHCP Leases . . . . . . . . . . . . . . . . . . . . . . . 8 - - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 - 6.1. Forgery Resilience . . . . . . . . . . . . . . . . . . . . 9 - 6.2. Interface Binding . . . . . . . . . . . . . . . . . . . . 10 - 6.3. Packet Filtering . . . . . . . . . . . . . . . . . . . . . 10 - - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 - - 8. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - - 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 - - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 10.1. Normative References . . . . . . . . . . . . . . . . . . . 12 - 10.2. Informative References . . . . . . . . . . . . . . . . . . 13 - - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 - - - - - - - - - - - - -Bellis Expires October 25, 2009 [Page 2] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - + 1. Introduction ....................................................2 + 2. Terminology .....................................................3 + 3. The Transparency Principle ......................................3 + 4. Protocol Conformance ............................................4 + 4.1. Unexpected Flags and Data ..................................4 + 4.2. Label Compression ..........................................4 + 4.3. Unknown Resource Record Types ..............................4 + 4.4. Packet Size Limits .........................................4 + 4.4.1. TCP Transport .......................................5 + 4.4.2. Extension Mechanisms for DNS (EDNS0) ................6 + 4.4.3. IP Fragmentation ....................................6 + 4.5. Secret Key Transaction Authentication for DNS (TSIG) .......7 + 5. DHCP's Interaction with DNS .....................................7 + 5.1. Domain Name Server (DHCP Option 6) .........................7 + 5.2. Domain Name (DHCP Option 15) ...............................8 + 5.3. DHCP Leases ................................................8 + 6. Security Considerations .........................................9 + 6.1. Forgery Resilience .........................................9 + 6.2. Interface Binding .........................................10 + 6.3. Packet Filtering ..........................................10 + 7. Acknowledgements ...............................................10 + 8. References .....................................................11 + 8.1. Normative References ......................................11 + 8.2. Informative References ....................................12 1. Introduction - Research has found ([SAC035], [DOTSE]) that many commonly-used - broadband gateways (and similar devices) contain DNS proxies which - are incompatible in various ways with current DNS standards. + Research has found ([SAC035], [DOTSE]) that many commonly used + broadband gateways (and similar devices) contain DNS proxies that are + incompatible in various ways with current DNS standards. These proxies are usually simple DNS forwarders, but typically do not have any caching capabilities. The proxy serves as a convenient default DNS resolver for clients on the LAN, but relies on an - upstream resolver (e.g. at an ISP) to perform recursive DNS lookups. + upstream resolver (e.g., at an ISP) to perform recursive DNS lookups. Note that to ensure full DNS protocol interoperability it is preferred that client stub resolvers should communicate directly with - full-feature upstream recursive resolvers wherever possible. + full-feature, upstream recursive resolvers wherever possible. That notwithstanding, this document describes the incompatibilities that have been discovered and offers guidelines to implementors on @@ -134,13 +108,20 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 client must use the broadband gateway's DNS proxy. + + + +Bellis Best Current Practice [Page 2] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. - 3. The Transparency Principle It is not considered practical for a simple DNS proxy to implement @@ -148,30 +129,26 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 There are several reasons why this is the case: - o broadband gateways usually have limited hardware resources - o firmware upgrade cycles are long, and many users do not routinely - apply upgrades when they become available - o no-one knows what those future DNS features will be, nor how they - might be implemented - o it would substantially complicate the configuration UI of the - device + o Broadband gateways usually have limited hardware resources. - Furthermore some modern DNS protocol extensions (see e.g. EDNS0, + o Firmware upgrade cycles are long, and many users do not routinely + apply upgrades when they become available. + + o No one knows what those future DNS features will be or how they + might be implemented. + + o Doing so would substantially complicate the configuration user + interface (UI) of the device. + + Furthermore, some modern DNS protocol extensions (see, e.g., EDNS0 below) are intended to be used as "hop-by-hop" mechanisms. If the DNS proxy is considered to be such a "hop" in the resolution chain, then for it to function correctly, it would need to be fully compliant with all such mechanisms. - - -Bellis Expires October 25, 2009 [Page 3] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - [SAC035] shows that the more actively a proxy participates in the DNS - protocol then the more likely it is that it will somehow interfere - with the flow of messages between the DNS client and the upstream + protocol, the more likely it is that it will somehow interfere with + the flow of messages between the DNS client and the upstream recursive resolvers. The role of the proxy should therefore be no more and no less than to @@ -187,11 +164,18 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 Except when required to enforce an active security or network policy (such as maintaining a pre-authentication "walled garden"), end-users SHOULD be able to send their DNS queries to specified upstream + + + +Bellis Best Current Practice [Page 3] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + resolvers, thereby bypassing the proxy altogether. In this case, the gateway SHOULD NOT modify the DNS request or response packets in any way. - 4. Protocol Conformance 4.1. Unexpected Flags and Data @@ -205,26 +189,18 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 containing either the "Authentic Data" (AD) or "Checking Disabled" (CD) bits from DNSSEC [RFC4035]. This may be because [RFC1035] originally specified that these unused "Z" flag bits "MUST" be zero. - However these flag bits were always intended to be reserved for + However, these flag bits were always intended to be reserved for future use, so refusing to proxy any packet containing these flags (now that uses for those flags have indeed been defined) is not appropriate. - Therefore it is RECOMMENDED that proxies SHOULD ignore any unknown - DNS flags and proxy those packets as usual. + Therefore, proxies MUST ignore any unknown DNS flags and proxy those + packets as usual. 4.2. Label Compression Compression of labels as per Section 4.1.4 of [RFC1035] is optional. - - - -Bellis Expires October 25, 2009 [Page 4] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - Proxies MUST forward packets regardless of the presence or absence of compressed labels therein. @@ -236,28 +212,36 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 All requests and responses MUST be proxied regardless of the values of the QTYPE and QCLASS fields. - Similarly all responses MUST be proxied regardless of the values of + Similarly, all responses MUST be proxied regardless of the values of the TYPE and CLASS fields of any Resource Record therein. 4.4. Packet Size Limits [RFC1035] specifies that the maximum size of the DNS payload in a UDP packet is 512 octets. Where the required portions of a response - would not fit inside that limit the DNS server MUST set the + would not fit inside that limit, the DNS server MUST set the + + + +Bellis Best Current Practice [Page 4] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + "TrunCation" (TC) bit in the DNS response header to indicate that truncation has occurred. There are however two standard mechanisms - (described in Section 4.4.1 and Section 4.4.2) for transporting - responses larger than 512 octets. + (described in Sections 4.4.1 and 4.4.2) for transporting responses + larger than 512 octets. Many proxies have been observed to truncate all responses at 512 octets, and others at a packet size related to the WAN MTU, in either case doing so without correctly setting the TC bit. Other proxies have been observed to remove the TC bit in server - responses which correctly had the TC bit set by the server. + responses that correctly had the TC bit set by the server. - If a DNS response is truncated but the TC bit is not set then client - failures may result. In particular a naive DNS client library might + If a DNS response is truncated but the TC bit is not set, then client + failures may result. In particular, a naive DNS client library might suffer crashes due to reading beyond the end of the data actually received. @@ -266,29 +250,22 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 size. See Section 4.4.3 for recommendations for packet sizes exceeding the WAN MTU. - If a proxy must unilaterally truncate a response then the proxy MUST + If a proxy must unilaterally truncate a response, then the proxy MUST set the TC bit. Similarly, proxies MUST NOT remove the TC bit from responses. - - - - - - -Bellis Expires October 25, 2009 [Page 5] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - 4.4.1. TCP Transport Should a UDP query fail because of truncation, the standard fail-over - mechanism is to retry the query using TCP, as described in section + mechanism is to retry the query using TCP, as described in Section 6.1.3.2 of [RFC1123]. - DNS proxies SHOULD therefore be prepared to receive and forward - queries over TCP. + Whilst TCP transport is not strictly mandatory, it is supported by + the vast majority of stub resolvers and recursive servers. Lack of + support in the proxy prevents this fail-over mechanism from working. + + DNS proxies MUST therefore be prepared to receive and forward queries + over TCP. Note that it is unlikely that a client would send a request over TCP unless it had already received a truncated UDP response. Some @@ -298,14 +275,23 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 behaviour increases network traffic and causes delay in DNS resolution since the initial UDP request is doomed to fail. - Therefore whenever a proxy receives a request over TCP, the proxy + + + + +Bellis Best Current Practice [Page 5] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + + Therefore, whenever a proxy receives a request over TCP, the proxy SHOULD forward the query over TCP and SHOULD NOT attempt the same query over UDP first. 4.4.2. Extension Mechanisms for DNS (EDNS0) - The Extension Mechanism for DNS [RFC2671] was introduced to allow the - transport of larger DNS packets over UDP and also to allow for + The "Extension Mechanism for DNS" [RFC2671] was introduced to allow + the transport of larger DNS packets over UDP and also to allow for additional request and response flags. A client may send an OPT Resource Record (OPT RR) in the Additional @@ -314,9 +300,9 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 by DNSSEC to indicate that DNSSEC-related RRs should be returned to the client. - However some proxies have been observed to either reject (with a + However, some proxies have been observed to either reject (with a FORMERR response code) or black-hole any packet containing an OPT RR. - As per Section 4.1 proxies SHOULD NOT refuse to proxy such packets. + As per Section 4.1, proxies MUST NOT refuse to proxy such packets. 4.4.3. IP Fragmentation @@ -324,18 +310,12 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 gateway's algorithm for handling fragmented IP packets. Several methods are possible: - 1. fragments are dropped - 2. fragments are forwarded individually as they're received - 3. complete packets are reassembled on the gateway, and then re- - fragmented (if necessary) as they're forwarded to the client + 1. Fragments are dropped. + 2. Fragments are forwarded individually as they're received. - - -Bellis Expires October 25, 2009 [Page 6] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - + 3. Complete packets are reassembled on the gateway and then re- + fragmented (if necessary) as they're forwarded to the client. Method 1 above will cause compatibility problems with EDNS0 unless the DNS client is configured to advertise an EDNS0 buffer size @@ -347,11 +327,20 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 to 65535 octets, most common DNS server implementations do not support a buffer size above 4096 octets. - Therefore (irrespective of which of the methods above is in use) + Therefore (irrespective of which of the above methods is in use), proxies SHOULD be capable of forwarding UDP packets up to a payload size of at least 4096 octets. - NB: in theory IP fragmentation may also occur if the LAN MTU is + + + + +Bellis Best Current Practice [Page 6] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + + NB: in theory, IP fragmentation may also occur if the LAN MTU is smaller than the WAN MTU, although the author has not observed such a configuration in use on any residential broadband service. @@ -372,55 +361,58 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 containing TKEY [RFC2930] Resource Records. NB: any DNS proxy (such as those commonly found in WiFi hotspot - "walled gardens") which transparently intercepts all DNS queries, and - which returns unsigned responses to signed queries, will also cause + "walled gardens") that transparently intercepts all DNS queries and + that returns unsigned responses to signed queries, will also cause TSIG authentication failures. - 5. DHCP's Interaction with DNS Whilst this document is primarily about DNS proxies, most consumers rely on DHCP [RFC2131] to obtain network configuration settings. - Such settings include the client machine's IP address, subnet mask - and default gateway, but also include DNS related settings. + Such settings include the client machine's IP address, subnet mask, + and default gateway, but also include DNS-related settings. It is therefore appropriate to examine how DHCP affects client DNS - - - -Bellis Expires October 25, 2009 [Page 7] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - configuration. 5.1. Domain Name Server (DHCP Option 6) Most gateways default to supplying their own IP address in the DHCP "Domain Name Server" option [RFC2132]. The net result is that - without explicit re-configuration many DNS clients will by default + without explicit re-configuration many DNS clients will, by default, send queries to the gateway's DNS proxy. This is understandable behaviour given that the correct upstream settings are not usually known at boot time. + + + + + + + +Bellis Best Current Practice [Page 7] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + Most gateways learn their own DNS settings via values supplied by an - ISP via DHCP or PPP over the WAN interface. However whilst many + ISP via DHCP or PPP over the WAN interface. However, whilst many gateways do allow the device administrator to override those values, some gateways only use those supplied values to affect the proxy's own forwarding function, and do not offer these values via DHCP. - When using such a device the only way to avoid using the DNS proxy is - to hard-code the required values in the client operating system. + When using such a device, the only way to avoid using the DNS proxy + is to hard-code the required values in the client operating system. This may be acceptable for a desktop system but it is inappropriate - for mobile devices which are regularly used on many different + for mobile devices that are regularly used on many different networks. As per Section 3, end-users SHOULD be able to send their DNS queries directly to specified upstream resolvers, ideally without hard-coding those settings in their stub resolver. - It is therefore RECOMMENDED that gateways SHOULD support device + It is therefore RECOMMENDED that gateways SHOULD support device- administrator configuration of values for the "Domain Name Server" DHCP option. @@ -431,80 +423,72 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 attributed to particular equipment vendors whose firmware defaults this DHCP option to specific values. - Since no standard exists for a "local" scoped domain name suffix it + Since no standard exists for a "local" scoped domain name suffix, it is RECOMMENDED that the default value for this option SHOULD be empty, and that this option MUST NOT be sent to clients when no value is configured. 5.3. DHCP Leases - It is noted that some DHCP servers in broadband gateways by default - offer their own IP address for the "Domain Name Server" option (as + It is noted that some DHCP servers in broadband gateways offer, by + default, their own IP address for the "Domain Name Server" option (as described above) but then automatically start offering the upstream - - - -Bellis Expires October 25, 2009 [Page 8] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - servers' addresses once they've been learnt over the WAN interface. - In general this behaviour is highly desirable, but the effect for the - end-user is that the settings used depend on whether the DHCP lease - was obtained before or after the WAN link was established. + In general, this behaviour is highly desirable, but the effect for + the end-user is that the settings used depend on whether the DHCP + lease was obtained before or after the WAN link was established. - If the DHCP lease is obtained whilst the WAN link is down then the + If the DHCP lease is obtained whilst the WAN link is down, then the DHCP client (and hence the DNS client) will not receive the correct values until the DHCP lease is renewed. + + + + +Bellis Best Current Practice [Page 8] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + Whilst no specific recommendations are given here, vendors may wish - to give consideration to the length of DHCP leases, and whether some - mechanism for forcing a DHCP lease renewal might be appropriate. + to give consideration to the length of DHCP leases and to whether + some mechanism for forcing a DHCP lease renewal might be appropriate. Another possibility is that the learnt upstream values might be persisted in non-volatile memory such that on reboot the same values - can be automatically offered via DHCP. However this does run the + can be automatically offered via DHCP. However, this does run the risk that incorrect values are initially offered if the device is moved or connected to another ISP. - Alternatively, the DHCP server might only issue very short (i.e. 60 + Alternatively, the DHCP server might only issue very short (i.e., 60 second) leases while the WAN link is down, only reverting to more typical lease lengths once the WAN link is up and the upstream DNS - servers are known. Indeed with such a configuration it may be + servers are known. Indeed, with such a configuration it may be possible to avoid the need to implement a DNS proxy function in the broadband gateway at all. - 6. Security Considerations - This document introduces no new protocols. However there are some - security related recommendations for vendors that are listed here. + This document introduces no new protocols. However, there are some + security-related recommendations for vendors that are listed here. 6.1. Forgery Resilience - Whilst DNS proxies are not usually full-feature resolvers they + Whilst DNS proxies are not usually full-feature resolvers, they nevertheless share some characteristics with them. - Notwithstanding the recommendations above about transparency many DNS - proxies are observed to pick a new Query ID for outbound requests to - ensure that responses are directed to the correct client. + Notwithstanding the recommendations above about transparency, many + DNS proxies are observed to pick a new Query ID for outbound requests + to ensure that responses are directed to the correct client. - NB: Changing the Query ID is acceptable and compatible with proxying + NB: changing the Query ID is acceptable and compatible with proxying TSIG-signed packets since the TSIG signature calculation is based on - the original message ID which is carried in the TSIG RR. + the original message ID, which is carried in the TSIG RR. It has been standard guidance for many years that each DNS query - should use a randomly generated Query ID. However many proxies have - - - -Bellis Expires October 25, 2009 [Page 9] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - + should use a randomly generated Query ID. However, many proxies have been observed picking sequential Query IDs for successive requests. It is strongly RECOMMENDED that DNS proxies follow the relevant @@ -513,126 +497,76 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 applies to source port selection within any NAT function. If a DNS proxy is running on a broadband gateway with NAT that is - compliant with [RFC4787] then it SHOULD also follow the + compliant with [RFC4787], then it SHOULD also follow the recommendations in Section 10 of [RFC5452] concerning how long DNS state is kept. + + +Bellis Best Current Practice [Page 9] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + 6.2. Interface Binding Some gateways have been observed to have their DNS proxy listening on both internal (LAN) and external (WAN) interfaces. In this - configuration it is possible for the proxy to be used to mount + configuration, it is possible for the proxy to be used to mount reflector attacks as described in [RFC5358]. - The DNS proxy in a gateway SHOULD NOT by default be accessible from + The DNS proxy in a gateway SHOULD NOT, by default, be accessible from the WAN interfaces of the device. 6.3. Packet Filtering The Transparency and Robustness Principles are not entirely - compatible with the deep packet inspection features of security - appliances such as firewalls which are intended to protect systems on - the inside of a network from rogue traffic. + compatible with the deep packet-inspection features of security + appliances such as firewalls, which are intended to protect systems + on the inside of a network from rogue traffic. - However a clear distinction may be made between traffic that is + However, a clear distinction may be made between traffic that is intrinsically malformed and that which merely contains unexpected data. - Examples of malformed packets which MAY be dropped include: + Examples of malformed packets that MAY be dropped include: - o invalid compression pointers (i.e. those that point outside of the - current packet, or which might cause a parsing loop). - o incorrect counts for the Question, Answer, Authority and + o invalid compression pointers (i.e., those that point outside of + the current packet or that might cause a parsing loop) + + o incorrect counts for the Question, Answer, Authority, and Additional Sections (although care should be taken where - truncation is a possibility). + truncation is a possibility) - Since dropped packets will cause the client to repeatedly retransmit - the original request, it is RECOMMENDED that proxies SHOULD instead - return a suitable DNS error response to the client (i.e. SERVFAIL) - instead of dropping the packet completely. + Dropped packets will cause the client to repeatedly retransmit the + original request, with the client only detecting the error after + several retransmit intervals. + In these circumstances, proxies SHOULD synthesise a suitable DNS + error response to the client (i.e., SERVFAIL) instead of dropping the + packet completely. This will allow the client to detect the error + immediately. - - - - -Bellis Expires October 25, 2009 [Page 10] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - -7. IANA Considerations - - This document requests no IANA actions. - - -8. Change Log - - NB: to be removed by the RFC Editor before publication. - - draft-ietf-dnsproxy-05 - Removed specific reference to 28 byte IP headers (from Mark - Andrews) - - draft-ietf-dnsproxy-04 - post WGLC - Introduction expanded - Section 5.2 - changed SHOULD to MUST - Section 4.5 - changed SHOULD to MUST (Alex Bligh) - Editorial nits (from Andrew Sullivan, Alfred Hones) - Clarificaton on end-user vs device administrator (Alan Barrett, - Paul Selkirk) - - draft-ietf-dnsproxy-03 - Editorial nits and mention of LAN MTU (from Alex Bligh) - - draft-ietf-dnsproxy-02 - Changed "router" to "gateway" throughout (David Oran) - Updated forgery resilience reference - Elaboration on bypassability (from Nicholas W.) - Elaboration on NAT source port randomisation (from Nicholas W.) - Mention of using short DHCP leases while the WAN link is down - (from Ralph Droms) - Further clarification on permissibility of altering QID when using - TSIG - - draft-ietf-dnsproxy-01 - Strengthened recommendations about truncation (from Shane Kerr) - New TSIG text (with help from Olafur) - Additional forgery resilience text (from Olafur) - Compression support (from Olafur) - Correction of text re: QID changes and compatibility with TSIG - - draft-ietf-dnsproxy-00 - Changed recommended DPI error to SERVFAIL (from Jelte) - Changed example for invalid compression pointers (from Wouter). - Note about TSIG implications of changing Query ID (from Wouter). - Clarified TC-bit text (from Wouter) - - - - - -Bellis Expires October 25, 2009 [Page 11] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - - Extra text about proxy bypass (Nicholas W.) - - draft-bellis-dnsproxy-00 - Initial draft - - -9. Acknowledgements +7. Acknowledgements The author would particularly like to acknowledge the assistance of - Lisa Phifer of Core Competence. In addition the author is grateful + Lisa Phifer of Core Competence. In addition, the author is grateful for the feedback from the members of the DNSEXT Working Group. -10. References -10.1. Normative References + + + + +Bellis Best Current Practice [Page 10] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + +8. References + +8.1. Normative References [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. @@ -665,14 +599,6 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 [RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record (RR) Types", RFC 3597, September 2003. - - - -Bellis Expires October 25, 2009 [Page 12] - -Internet-Draft DNS Proxy Implementation Guidelines April 2009 - - [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Protocol Modifications for the DNS Security Extensions", RFC 4035, March 2005. @@ -685,10 +611,19 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 Nameservers in Reflector Attacks", BCP 140, RFC 5358, October 2008. + + + + +Bellis Best Current Practice [Page 11] + +RFC 5625 DNS Proxy Implementation Guidelines August 2009 + + [RFC5452] Hubert, A. and R. van Mook, "Measures for Making DNS More Resilient against Forged Answers", RFC 5452, January 2009. -10.2. Informative References +8.2. Informative References [DOTSE] Ahlund and Wallstrom, "DNSSEC Tests of Consumer Broadband Routers", February 2008, @@ -698,7 +633,6 @@ Internet-Draft DNS Proxy Implementation Guidelines April 2009 Broadband Routers and Firewalls", September 2008, . - Author's Address Ray Bellis @@ -708,7 +642,7 @@ Author's Address United Kingdom Phone: +44 1865 332211 - Email: ray.bellis@nominet.org.uk + EMail: ray.bellis@nominet.org.uk URI: http://www.nominet.org.uk/ @@ -724,5 +658,18 @@ Author's Address -Bellis Expires October 25, 2009 [Page 13] + + + + + + + + + + + + + +Bellis Best Current Practice [Page 12]