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@@ -1,10 +1,11 @@
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INTERNET-DRAFT Samuel Weiler
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Expires: December 2003 June 12, 2003
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Expires: December 2003 June 29, 2003
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Updates: RFC 2535, [DS]
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Legacy Resolver Compatibility for Delegation Signer
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draft-ietf-dnsext-dnssec-2535typecode-change-02.txt
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draft-ietf-dnsext-dnssec-2535typecode-change-03.txt
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Status of this Memo
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@@ -44,12 +45,16 @@ Abstract
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these interactions be avoided by changing the type codes and
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mnemonics of the DNSSEC RRs (SIG, KEY, and NXT).
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Changes between 02 and 03:
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KEY (as well as SIG) retained for SIG(0) use only.
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Changes between 01 and 02:
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SIG(0) still uses SIG, not RRSIG. Added 2931 reference.
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Domain names embedded in NSECs and RRSIGs are not compressible and
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are not downcased. Added unknown-rrs reference.
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are not downcased. Added unknown-rrs reference (as informative).
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Simplified the last paragraph of section 3 (NSEC doesn't always
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signal a negative answer).
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@@ -89,11 +94,11 @@ Changes between 01 and 02:
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This document addresses a specific problem caused by Delegation
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Signer's [DS] introduction of new semantics for the NXT RR that are
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incompatible with the semantics in [RFC2535]. Answers provided by
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DS-aware servers can trigger an unacceptable failure mode in some
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resolvers that implement RFC 2535, which provides a great
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disincentive to sign zones with DS. The proposed solution allows
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for the incremental deployment of DS.
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incompatible with the semantics in RFC 2535 [RFC2535]. Answers
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provided by DS-aware servers can trigger an unacceptable failure
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mode in some resolvers that implement RFC 2535, which provides a
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great disincentive to sign zones with DS. The proposed solution
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allows for the incremental deployment of DS.
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1.1 Terminology
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@@ -108,15 +113,15 @@ Changes between 01 and 02:
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1.2 The Problem
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Delegation Signer [DS] introduces new semantics for the NXT RR that
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are incompatible with the semantics in [RFC2535]. In [RFC2535],
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NXT records were only required to be returned as part of a
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Delegation Signer introduces new semantics for the NXT RR that are
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incompatible with the semantics in RFC 2535. In RFC 2535, NXT
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records were only required to be returned as part of a
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non-existence proof. With DS, an unsecure referral returns, in
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addition to the NS, a proof of non-existence of a DS RR in the form
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of an NXT and SIG(NXT). RFC 2535 didn't specify how a resolver was
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to interpret a response with both an NS and an NXT in the authority
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section and with NOERROR or NODATA set. Some widely deployed
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2535-aware resolvers interpret any answer with an NXT as a proof of
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section, RCODE=0, and AA=0. Some widely deployed 2535-aware
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resolvers interpret any answer with an NXT as a proof of
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non-existence of the requested record. This results in unsecure
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delegations being invisible to 2535-aware resolvers and violates
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the basic architectural principle that DNSSEC must do no harm --
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@@ -164,7 +169,7 @@ Changes between 01 and 02:
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called "DA"), and having authoritative servers send DNSSEC data
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only in response to queries with the DA bit set, would accomplish
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this. This bit would presumably supplant the DO bit described in
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[RFC3225].
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RFC 3225.
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This solution is sufficient only if all 2535-aware resolvers zero
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out EDNS0 flags that they don't understand. If one passed through
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@@ -177,16 +182,16 @@ Changes between 01 and 02:
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2.4. Increment the EDNS version
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Another proposed solution is to increment the EDNS version number
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as defined in [RFC2671], on the assumption that all existing
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implementations will reject higher versions than they support,
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and retain the DO bit as the signal for DNSSEC awareness. This
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approach has not been tested.
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as defined in RFC 2671 [RFC2671], on the assumption that all
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existing implementations will reject higher versions than they
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support, and retain the DO bit as the signal for DNSSEC awareness.
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This approach has not been tested.
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2.5. Do nothing
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There is a large deployed base of DNS resolvers that understand
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DNSSEC as defined by the standards track [RFC2535] and [RFC2065]
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and, due to underspecification in those documents, interpret any
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DNSSEC as defined by the standards track RFC 2535 and RFC 2065
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and, due to under specification in those documents, interpret any
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answer with an NXT as a non-existence proof. So long as that is
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the case, zone owners will have a strong incentive to not sign any
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zones that contain unsecure delegations, lest those delegations be
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@@ -219,10 +224,10 @@ Changes between 01 and 02:
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application use, per [RFC3445]. RRSIG (Resource Record SIGnature)
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will replace SIG, and NSEC (Next SECure) will replace NXT. These
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new types completely replace the old types, except that SIG(0)
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[RFC2931] will continue to use SIG.
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[RFC2931] will continue to use SIG and KEY.
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The new types will have exactly the same syntax and semantics as
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specified for SIG, KEY, and NXT in [RFC2535] and [DS] except for
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specified for SIG, KEY, and NXT in RFC 2535 and [DS] except for
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the following:
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1) Consistent with [UNKNOWN-RRs], domain names embedded in
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@@ -239,11 +244,12 @@ Changes between 01 and 02:
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unknown RRs and SHOULD NOT assign any special semantic value to
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them. It MUST NOT use them for DNSSEC validations or other DNS
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operational decision making. For example, a resolver MUST NOT use
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DNSKEYs to validate SIGs or use KEYs to validate RRSIGs.
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Authoritative servers SHOULD NOT serve SIG, KEY, or NXT records.
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If those records are included, they MUST NOT receive special
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treatment. As an example, if a SIG is included in a signed zone,
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there MUST be an RRSIG for it.
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DNSKEYs to validate SIGs or use KEYs to validate RRSIGs. If SIG,
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KEY, or NXT RRs are included in a zone, they MUST NOT receive
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special treatment. As an example, if a SIG is included in a signed
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zone, there MUST be an RRSIG for it. Authoritative servers may
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wish to give error messages when loading zones containing SIG or
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NXT records (KEY records may be included for SIG(0)).
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As a clarification to previous documents, some positive responses,
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particularly wildcard proofs and unsecure referrals, will contain
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@@ -256,8 +262,8 @@ Changes between 01 and 02:
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Types by assigning types 46, 47, and 48 to the RRSIG, NSEC, and
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DNSKEY RRs, respectively.
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Types 24 (SIG) is retained for SIG(0) [RFC2931] use only. Types 25
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and 30 (KEY and NXT) should be marked as Obsolete.
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Types 24 and 25 (SIG and KEY) are retained for SIG(0) [RFC2931]
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use only. Type 30 (NXT) should be marked as Obsolete.
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5. Security Considerations
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@@ -312,7 +318,6 @@ Changes between 01 and 02:
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Record Types. draft-ietf-dnsext-unknown-rrs-05.txt
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Publication as RFC pending.
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8. Acknowledgments
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The proposed solution and the analysis of alternatives had many
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@@ -330,9 +335,9 @@ Changes between 01 and 02:
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9. Author's Address
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Samuel Weiler
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Network Associates Laboratories
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15204 Omega Dr., Suite 300
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Rockville, MD 20850
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SPARTA, Inc.
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7075 Samuel Morse Drive
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Columbia, MD 21046
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USA
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weiler@tislabs.com
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