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doc/draft/draft-ietf-dnsext-dnssec-bis-updates-18.txt → doc/draft/draft-ietf-dnsext-dnssec-bis-updates-19.txt
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@ -5,22 +5,22 @@ Network Working Group S. Weiler
Internet-Draft SPARTA, Inc.
Updates: 4033, 4034, 4035, 5155 D. Blacka
(if approved) Verisign, Inc.
Intended status: Standards Track April 30, 2012
Expires: November 1, 2012
Intended status: Standards Track July 13, 2012
Expires: January 14, 2013
Clarifications and Implementation Notes for DNSSECbis
draft-ietf-dnsext-dnssec-bis-updates-18
Clarifications and Implementation Notes for DNSSEC
draft-ietf-dnsext-dnssec-bis-updates-19
Abstract
This document is a collection of technical clarifications to the
DNSSECbis document set. It is meant to serve as a resource to
implementors as well as a repository of DNSSECbis errata.
DNSSEC document set. It is meant to serve as a resource to
implementors as well as a repository of DNSSEC errata.
This document updates the core DNSSECbis documents (RFC4033, RFC4034,
This document updates the core DNSSEC documents (RFC4033, RFC4034,
and RFC4035) as well as the NSEC3 specification (RFC5155). It also
defines NSEC3 and SHA-2 as core parts of the DNSSECbis specification.
defines NSEC3 and SHA-2 as core parts of the DNSSEC specification.
Status of this Memo
@ -37,7 +37,7 @@ Status of this Memo
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 1, 2012.
This Internet-Draft will expire on January 14, 2013.
Copyright Notice
@ -52,9 +52,9 @@ Copyright Notice
Weiler & Blacka Expires November 1, 2012 [Page 1]
Weiler & Blacka Expires January 14, 2013 [Page 1]
Internet-Draft DNSSECbis Implementation Notes April 2012
Internet-Draft DNSSEC Implementation Notes July 2012
to this document. Code Components extracted from this document must
@ -108,9 +108,9 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
Weiler & Blacka Expires November 1, 2012 [Page 2]
Weiler & Blacka Expires January 14, 2013 [Page 2]
Internet-Draft DNSSECbis Implementation Notes April 2012
Internet-Draft DNSSEC Implementation Notes July 2012
Table of Contents
@ -118,7 +118,7 @@ Table of Contents
1. Introduction and Terminology . . . . . . . . . . . . . . . . . 4
1.1. Structure of this Document . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Important Additions to DNSSSECbis . . . . . . . . . . . . . . 4
2. Important Additions to DNSSEC . . . . . . . . . . . . . . . . 4
2.1. NSEC3 Support . . . . . . . . . . . . . . . . . . . . . . 4
2.2. SHA-2 Support . . . . . . . . . . . . . . . . . . . . . . 5
3. Scaling Concerns . . . . . . . . . . . . . . . . . . . . . . . 5
@ -127,63 +127,63 @@ Table of Contents
4.1. Clarifications on Non-Existence Proofs . . . . . . . . . . 5
4.2. Validating Responses to an ANY Query . . . . . . . . . . . 6
4.3. Check for CNAME . . . . . . . . . . . . . . . . . . . . . 6
4.4. Insecure Delegation Proofs . . . . . . . . . . . . . . . . 6
4.4. Insecure Delegation Proofs . . . . . . . . . . . . . . . . 7
5. Interoperability Concerns . . . . . . . . . . . . . . . . . . 7
5.1. Errors in Canonical Form Type Code List . . . . . . . . . 7
5.2. Unknown DS Message Digest Algorithms . . . . . . . . . . . 7
5.3. Private Algorithms . . . . . . . . . . . . . . . . . . . . 8
5.4. Caution About Local Policy and Multiple RRSIGs . . . . . . 8
5.4. Caution About Local Policy and Multiple RRSIGs . . . . . . 9
5.5. Key Tag Calculation . . . . . . . . . . . . . . . . . . . 9
5.6. Setting the DO Bit on Replies . . . . . . . . . . . . . . 9
5.7. Setting the AD Bit on Queries . . . . . . . . . . . . . . 9
5.8. Setting the AD Bit on Replies . . . . . . . . . . . . . . 9
5.8. Setting the AD Bit on Replies . . . . . . . . . . . . . . 10
5.9. Always set the CD bit on Queries . . . . . . . . . . . . . 10
5.10. Nested Trust Anchors . . . . . . . . . . . . . . . . . . . 10
5.11. Mandatory Algorithm Rules . . . . . . . . . . . . . . . . 11
5.12. Ignore Extra Signatures From Unknown Keys . . . . . . . . 11
5.12. Ignore Extra Signatures From Unknown Keys . . . . . . . . 12
6. Minor Corrections and Clarifications . . . . . . . . . . . . . 12
6.1. Finding Zone Cuts . . . . . . . . . . . . . . . . . . . . 12
6.2. Clarifications on DNSKEY Usage . . . . . . . . . . . . . . 12
6.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 12
6.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 13
6.4. Errors in RFC 5155 . . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 15
Appendix B. Discussion of Setting the CD Bit . . . . . . . . . . 15
Appendix C. Discussion of Trust Anchor Preference Options . . . . 18
C.1. Closest Encloser . . . . . . . . . . . . . . . . . . . . . 18
C.2. Accept Any Success . . . . . . . . . . . . . . . . . . . . 19
C.3. Preference Based on Source . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix B. Discussion of Setting the CD Bit . . . . . . . . . . 16
Appendix C. Discussion of Trust Anchor Preference Options . . . . 19
C.1. Closest Encloser . . . . . . . . . . . . . . . . . . . . . 19
C.2. Accept Any Success . . . . . . . . . . . . . . . . . . . . 20
C.3. Preference Based on Source . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Weiler & Blacka Expires November 1, 2012 [Page 3]
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Internet-Draft DNSSECbis Implementation Notes April 2012
Internet-Draft DNSSEC Implementation Notes July 2012
1. Introduction and Terminology
This document lists some additions, clarifications and corrections to
the core DNSSECbis specification, as originally described in
[RFC4033], [RFC4034], and [RFC4035], and later amended by [RFC5155].
(See section Section 2 for more recent additions to that core
document set.)
the core DNSSEC specification, as originally described in [RFC4033],
[RFC4034], and [RFC4035], and later amended by [RFC5155]. (See
section Section 2 for more recent additions to that core document
set.)
It is intended to serve as a resource for implementors and as a
repository of items that need to be addressed when advancing the
DNSSECbis documents from Proposed Standard to Draft Standard.
DNSSEC documents along the Standards Track.
1.1. Structure of this Document
The clarifications and changes to DNSSECbis are sorted according to
The clarifications and changes to DNSSEC are sorted according to
their importance, starting with ones which could, if ignored, lead to
security problems and progressing down to clarifications that are
expected to have little operational impact.
@ -196,11 +196,11 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
[RFC2119].
2. Important Additions to DNSSSECbis
2. Important Additions to DNSSEC
This section lists some documents that should be considered core
DNSSEC protocol documents in addition to those originally specified
in Section 10 of [RFC4033].
This section lists some documents that are now considered core DNSSEC
protocol documents in addition to those originally specified in
Section 10 of [RFC4033].
2.1. NSEC3 Support
@ -211,21 +211,21 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
validation of responses using NSEC3 will be hampered in validating
large portions of the DNS space.
[RFC5155] should be considered part of the DNS Security Document
Family as described by [RFC4033], Section 10.
[RFC5155] is now considered part of the DNS Security Document Family
as described by [RFC4033], Section 10.
Note that the algorithm identifiers defined in RFC5155 (DSA-NSEC3-
SHA1 and RSASHA1-NSEC3-SHA1) and RFC5702 (RSASHA256 and RSASHA512)
signal that a zone MAY be using NSEC3, rather than NSEC. The zone
signal that a zone might be using NSEC3, rather than NSEC. The zone
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MAY be using either and validators supporting these algorithms MUST
may be using either and validators supporting these algorithms MUST
support both NSEC3 and NSEC responses.
2.2. SHA-2 Support
@ -236,8 +236,8 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
Validator implementations are strongly encouraged to include support
for these algorithms for DS, DNSKEY, and RRSIG records.
Both [RFC4509] and [RFC5702] should also be considered part of the
DNS Security Document Family as described by [RFC4033], Section 10.
Both [RFC4509] and [RFC5702] are now considered part of the DNS
Security Document Family as described by [RFC4033], Section 10.
3. Scaling Concerns
@ -245,9 +245,14 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
3.1. Implement a BAD cache
Section 4.7 of RFC4035 permits security-aware resolvers to implement
a BAD cache. Because of scaling concerns not discussed in this
document, that guidance has changed: security-aware resolvers SHOULD
implement a BAD cache as described in RFC4035.
a BAD cache. That guidance has changed: security-aware resolvers
SHOULD implement a BAD cache as described in RFC4035.
This change in guidance is based on operational experience with
DNSSEC administrative errors leading to significant increases in DNS
traffic, with an accompanying realization that such events are more
likely and more damaging than originally supposed. An example of one
such event is documented in "Roll Over and Die" [Huston].
4. Security Concerns
@ -266,6 +271,16 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
o the NS bit set,
o the SOA bit clear, and
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o a signer field that is shorter than the owner name of the NSEC RR,
or the original owner name for the NSEC3 RR.
@ -274,13 +289,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
that (original) owner name other than DS RRs, and all RRs below that
owner name regardless of type.
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Similarly, the algorithm would also allow an NSEC RR at the same
owner name as a DNAME RR, or an NSEC3 RR at the same original owner
name as a DNAME, to prove the non-existence of names beneath that
@ -306,11 +314,11 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
4.3. Check for CNAME
Section 5 of [RFC4035] says little about validating responses based
on (or that should be based on) CNAMEs. When validating a NOERROR/
NODATA response, validators MUST check the CNAME bit in the matching
NSEC or NSEC3 RR's type bitmap in addition to the bit for the query
type.
Section 5 of [RFC4035] says nothing explicit about validating
responses based on (or that should be based on) CNAMEs. When
validating a NOERROR/NODATA response, validators MUST check the CNAME
bit in the matching NSEC or NSEC3 RR's type bitmap in addition to the
bit for the query type.
Without this check, an attacker could successfully transform a
positive CNAME response into a NOERROR/NODATA response by (e.g.)
@ -320,6 +328,15 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
set, and thus the response should have been a positive CNAME
response.
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4.4. Insecure Delegation Proofs
[RFC4035] Section 5.2 specifies that a validator, when proving a
@ -330,13 +347,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
alternately make sure that the delegation is covered by an NSEC3 RR
with the Opt-Out flag set.
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Without this check, an attacker could reuse an NSEC or NSEC3 RR
matching a non-delegation name to spoof an unsigned delegation at
that name. This would claim that an existing signed RRset (or set of
@ -376,6 +386,13 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
The existing text says:
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If the validator does not support any of the algorithms listed in
an authenticated DS RRset, then the resolver has no supported
authentication path leading from the parent to the child. The
@ -385,14 +402,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
In other words, when determining the security status of a zone, a
validator disregards any authenticated DS records that specify
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unknown or unsupported DNSKEY algorithms. If none are left, the zone
is treated as if it were unsigned.
@ -418,20 +427,28 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
In the remaining cases, the security status of the zone depends on
whether or not the resolver supports any of the private algorithms in
use (provided that these DS records use supported hash functions, as
discussed in Section 5.2). In these cases, the resolver MUST
retrieve the corresponding DNSKEY for each private algorithm DS
record and examine the public key field to determine the algorithm in
use. The security-aware resolver MUST ensure that the hash of the
DNSKEY RR's owner name and RDATA matches the digest in the DS RR as
described in Section 5.2 of [RFC4035], authenticating the DNSKEY. If
all of the retrieved and authenticated DNSKEY RRs use unknown or
unsupported private algorithms, then the zone is treated as if it
were unsigned.
use (provided that these DS records use supported message digest
algorithms, as discussed in Section 5.2 of this document). In these
cases, the resolver MUST retrieve the corresponding DNSKEY for each
private algorithm DS record and examine the public key field to
determine the algorithm in use. The security-aware resolver MUST
ensure that the hash of the DNSKEY RR's owner name and RDATA matches
the digest in the DS RR as described in Section 5.2 of [RFC4035],
authenticating the DNSKEY. If all of the retrieved and authenticated
DNSKEY RRs use unknown or unsupported private algorithms, then the
zone is treated as if it were unsigned.
Note that if none of the private algorithm DS RRs can be securely
matched to DNSKEY RRs and no other DS establishes that the zone is
secure, the referral should be considered Bogus data as discussed in
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[RFC4035].
This clarification facilitates the broader use of private algorithms,
@ -441,14 +458,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
When multiple RRSIGs cover a given RRset, [RFC4035] Section 5.3.3
suggests that "the local resolver security policy determines whether
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the resolver also has to test these RRSIG RRs and how to resolve
conflicts if these RRSIG RRs lead to differing results."
@ -475,18 +484,30 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
5.6. Setting the DO Bit on Replies
As stated in [RFC3225], the DO bit of the query MUST be copied in the
response. However, in order to interoperate with implementations
that ignore this rule on sending, resolvers MUST ignore the DO bit in
responses.
As stated in Section 3 of [RFC3225], the DO bit of the query MUST be
copied in the response. However, in order to interoperate with
implementations that ignore this rule on sending, resolvers MUST
ignore the DO bit in responses.
5.7. Setting the AD Bit on Queries
The use of the AD bit in the query was previously undefined. This
document defines it as a signal indicating that the requester
understands and is interested in the value of the AD bit in the
response. This allows a requestor to indicate that it understands
the AD bit without also requesting DNSSEC data via the DO bit.
The semantics of the AD bit in the query were previously undefined.
Section 4.6 of [RFC4035] instructed resolvers to always clear the AD
bit when composing queries.
This document defines setting the AD bit in a query as a signal
indicating that the requester understands and is interested in the
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value of the AD bit in the response. This allows a requestor to
indicate that it understands the AD bit without also requesting
DNSSEC data via the DO bit.
5.8. Setting the AD Bit on Replies
@ -498,13 +519,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
in RFC 4035, section 3.2.3, and the request contained either a set DO
bit or a set AD bit.
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5.9. Always set the CD bit on Queries
When processing a request with the CD bit set, a resolver SHOULD
@ -525,7 +539,7 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
does the cache need to track the state of the CD bit used to make a
given query. The problem arises when the cached response is a server
failure (RCODE 2), which may indicate that the requested data failed
DNSSEC validation at an upstream validating resolver. (RFC2308
DNSSEC validation at an upstream validating resolver. ([RFC2308]
permits caching of server failures for up to five minutes.) In these
cases, a new query with the CD bit set is required.
@ -539,6 +553,14 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
trust to the response zone. For example, imagine a validator
configured with trust anchors for "example." and "zone.example."
When the validator is asked to validate a response to
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"www.sub.zone.example.", either trust anchor could apply.
When presented with this situation, DNSSEC validators have a choice
@ -553,14 +575,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
The "Accept Any Success" policy is to try all applicable trust
anchors until one gives a validation result of Secure, in which case
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the final validation result is Secure. If and only if all applicable
trust anchors give a result of Insecure, the final validation result
is Insecure. If one or more trust anchors lead to a Bogus result and
@ -590,12 +604,20 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
Likewise, if there are DS records for multiple keys of the same
algorithm, any subset of those may appear in the DNSKEY RRset.
Lastly, note that this a requirement at the server side, not the
client side. Validators SHOULD accept any single valid path. They
SHOULD NOT insist that all algorithms signaled in the DS RRset work,
and they MUST NOT insist that all algorithms signaled in the DNSKEY
RRset work. A validator MAY have a configuration option to perform a
signature completeness test to support troubleshooting.
This requirement applies to servers, not validators. Validators
SHOULD accept any single valid path. They SHOULD NOT insist that all
algorithms signaled in the DS RRset work, and they MUST NOT insist
that all algorithms signaled in the DNSKEY RRset work. A validator
MAY have a configuration option to perform a signature completeness
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test to support troubleshooting.
5.12. Ignore Extra Signatures From Unknown Keys
@ -610,27 +632,13 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
zone.
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6. Minor Corrections and Clarifications
6.1. Finding Zone Cuts
Appendix C.8 of [RFC4035] discusses sending DS queries to the servers
for a parent zone. To do that, a resolver may first need to apply
special rules to discover what those servers are.
As explained in Section 3.1.4.1 of [RFC4035], security-aware name
servers need to apply special processing rules to handle the DS RR,
and in some situations the resolver may also need to apply special
rules to locate the name servers for the parent zone if the resolver
does not already have the parent's NS RRset. Section 4.2 of
[RFC4035] specifies a mechanism for doing that.
for a parent zone but does not state how to find those servers.
Specific instructions can be found in Section 4.2 of [RFC4035].
6.2. Clarifications on DNSKEY Usage
@ -655,6 +663,16 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
also possible to use a single DNSKEY, with or without the SEP bit
set, to sign the entire zone, including the DNSKEY RRset itself.
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6.3. Errors in Examples
The text in [RFC4035] Section C.1 refers to the examples in B.1 as
@ -666,13 +684,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
(antithetically, a label count of 3 would imply the answer was the
result of a wildcard expansion).
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The first paragraph of [RFC4035] Section C.6 also has a minor error:
the reference to "a.z.w.w.example" should instead be "a.z.w.example",
as in the previous line.
@ -710,6 +721,14 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
in the documents defining them. Additionally, this document
addresses some ambiguities and omissions in the core DNSSEC documents
that, if not recognized and addressed in implementations, could lead
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to security failures. In particular, the validation algorithm
clarifications in Section 4 are critical for preserving the security
properties DNSSEC offers. Furthermore, failure to address some of
@ -722,13 +741,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
of trust anchors at an upstream validator.
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9. References
9.1. Normative References
@ -765,8 +777,22 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
and RRSIG Resource Records for DNSSEC", RFC 5702,
October 2009.
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9.2. Informative References
[Huston] Michaelson, G., Wallstrom, P., Arends, R., and G. Huston,
"Roll Over and Die?", February 2010.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, March 1998.
[RFC3755] Weiler, S., "Legacy Resolver Compatibility for Delegation
Signer (DS)", RFC 3755, May 2004.
@ -777,14 +803,6 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
July 2007.
[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
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Trust Anchors", RFC 5011, September 2007.
[RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
@ -797,7 +815,7 @@ Appendix A. Acknowledgments
an editor of this document.
The editors are extremely grateful to those who, in addition to
finding errors and omissions in the DNSSECbis document set, have
finding errors and omissions in the DNSSEC document set, have
provided text suitable for inclusion in this document.
The lack of specificity about handling private algorithms, as
@ -815,6 +833,14 @@ Appendix A. Acknowledgments
The errors in the [RFC4035] examples were found by Roy Arends, who
also contributed text for Section 6.3 of this document.
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Text on the mandatory algorithm rules was derived from suggestions by
Matthijs Mekking and Ed Lewis.
@ -824,23 +850,16 @@ Appendix A. Acknowledgments
The editors would like to thank Alfred Hoenes, Ed Lewis, Danny Mayer,
Olafur Gudmundsson, Suzanne Woolf, Rickard Bellgrim, Mike St. Johns,
Mark Andrews, Wouter Wijngaards, Matthijs Mekking, Andrew Sullivan,
and Scott Rose for their substantive comments on the text of this
Jeremy Reed, Paul Hoffman, Mohan Parthasarathy, Florian Weimer,
Warren Kumari and Scott Rose for their contributions to this
document.
Appendix B. Discussion of Setting the CD Bit
RFC 4035 may be read as relying on the implicit assumption that there
is at most one validating system between the stub resolver and the
authoritative server for a given zone. It is entirely possible,
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[RFC4035] may be read as relying on the implicit assumption that
there is at most one validating system between the stub resolver and
the authoritative server for a given zone. It is entirely possible,
however, for more than one validator to exist between a stub resolver
and an authoritative server. If these different validators have
disjoint trust anchors configured, then it is possible that each
@ -870,6 +889,14 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
as local policy or from the API in the case of a stub). The second
column indicates whether the query needs to be forwarded for
resolution (F) or can be satisfied from a local cache (C). The third
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column is a line number, so that it can be referred to later in the
table. The fourth column indicates any relevant conditions at the
resolver: whether the resolver has a covering trust anchor and so on.
@ -877,26 +904,16 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
final column indicates what action the resolver takes.
The tables differentiate between "cached data" and "cached RCODE=2".
This is a shorthand; the point is that one has to treat RCODE=2 as
special, because it might indicate a validation failure somewhere
upstream. The distinction is really between "cached RCODE=2" and
"cached everything else".
This is a shorthand; the point is that one has to treat RCODE=2
(server failure) as special, because it might indicate a validation
failure somewhere upstream. The distinction is really between
"cached RCODE=2" and "cached everything else".
The tables are probably easiest to think of in terms of describing
what happens when a stub resolver sends a query to an intermediate
resolver, but they are perfectly general and can be applied to any
validating resolver.
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Model 1: "always set"
This model is so named because the validating resolver sets the CD
@ -918,6 +935,24 @@ Internet-Draft DNSSECbis Implementation Notes April 2012
0 C A5 covering TA Validate cached result and
return it.
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Model 2: "never set when receiving CD=0"
This model is so named because it sets CD=0 on upstream queries for
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Model 3: "sometimes set"
@ -1004,9 +1060,9 @@ C.1. Closest Encloser
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Encloser" policy would choose the "zone.example." trust anchor.
@ -1060,9 +1116,9 @@ C.3. Preference Based on Source
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Conversely, a validator might choose to prefer manually configured
@ -1116,5 +1172,5 @@ Authors' Addresses
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