draft-ietf-dnsext-dnssec-bis-updates-01.txt

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Network Working Group                                          S. Weiler
Internet-Draft                                               SPARTA, Inc
Updates: 4034, 4035 (if approved)                           May 23, 2005
Expires: November 24, 2005


         Clarifications and Implementation Notes for DNSSECbis
                draft-ietf-dnsext-dnssec-bis-updates-01

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document is a collection of minor technical clarifications to
   the DNSSECbis document set.  It is meant to serve as a resource to
   implementors as well as an interim repository of possible DNSSECbis
   errata.







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Proposed additions in future versions

   An index sorted by the section of DNSSECbis being clarified.

   A list of proposed protocol changes being made in other documents,
   such as NSEC3 and Epsilon.  This document would not make those
   changes, merely provide an index into the documents that are making
   changes.

Changes between -00 and -01

   Document significantly restructured.

   Added section on QTYPE=ANY.

Changes between personal submission and first WG draft

   Added Section 2.1 based on namedroppers discussions from March 9-10,
   2005.

   Added Section 3.4, Section 3.3, Section 4.3, and Section 2.2.

   Added the DNSSECbis RFC numbers.

   Figured out the confusion in Section 4.1.


























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Table of Contents

   1.  Introduction and Terminology . . . . . . . . . . . . . . . . .  4
     1.1   Structure of this Document . . . . . . . . . . . . . . . .  4
     1.2   Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Significant Concerns . . . . . . . . . . . . . . . . . . . . .  4
     2.1   Clarifications on Non-Existence Proofs . . . . . . . . . .  4
     2.2   Empty Non-Terminal Proofs  . . . . . . . . . . . . . . . .  5
     2.3   Validating Responses to an ANY Query . . . . . . . . . . .  5
   3.  Interoperability Concerns  . . . . . . . . . . . . . . . . . .  5
     3.1   Unknown DS Message Digest Algorithms . . . . . . . . . . .  5
     3.2   Private Algorithms . . . . . . . . . . . . . . . . . . . .  6
     3.3   Caution About Local Policy and Multiple RRSIGs . . . . . .  6
     3.4   Key Tag Calculation  . . . . . . . . . . . . . . . . . . .  7
   4.  Minor Corrections and Clarifications . . . . . . . . . . . . .  7
     4.1   Finding Zone Cuts  . . . . . . . . . . . . . . . . . . . .  7
     4.2   Clarifications on DNSKEY Usage . . . . . . . . . . . . . .  7
     4.3   Errors in Examples . . . . . . . . . . . . . . . . . . . .  8
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     7.1   Normative References . . . . . . . . . . . . . . . . . . .  8
     7.2   Informative References . . . . . . . . . . . . . . . . . .  9
       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  9
   A.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  9
       Intellectual Property and Copyright Statements . . . . . . . . 11

























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1.  Introduction and Terminology

   This document lists some minor clarifications and corrections to
   DNSSECbis, as described in [1], [2], and [3].

   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.

   In this version (-01 of the WG document), feedback is particularly
   solicited on the structure of the document and whether the text in
   the recently added sections is correct and sufficient.

   Proposed substantive additions to this document should be sent to the
   namedroppers mailing list as well as to the editor of this document.
   The editor would greatly prefer text suitable for direct inclusion in
   this document.

1.1  Structure of this Document

   The clarifications to DNSSECbis are sorted according to the editor's
   impression of their importance, starting with ones which could, if
   ignored, lead to security and stability problems and progressing down
   to clarifications that are likely to have little operational impact.
   Mere typos and awkward phrasings are not addressed unless they could
   lead to misinterpretation of the DNSSECbis documents.

1.2  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 RFC 2119 [4].

2.  Significant Concerns

   This section provides clarifications that, if overlooked, could lead
   to security issues or major interoperability problems.

2.1  Clarifications on Non-Existence Proofs

   RFC4035 Section 5.4 slightly underspecifies the algorithm for
   checking non-existence proofs.  In particular, the algorithm there
   might incorrectly allow the NSEC from the parent side of a zone cut
   to prove the non-existence of either other RRs at that name in the
   child zone or other names in the child zone.  It might also allow a
   NSEC at the same name as a DNAME to prove the non-existence of names
   beneath that DNAME.




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   A parent-side delegation NSEC (one with the NS bit set, but no SOA
   bit set, and with a singer field that's shorter than the owner name)
   must not be used to assume non-existence of any RRs below that zone
   cut (both RRs at that ownername and at ownernames with more leading
   labels, no matter their content).  Similarly, an NSEC with the DNAME
   bit set must not be used to assume the non-existence of any
   descendant of that NSEC's owner name.

2.2  Empty Non-Terminal Proofs

   To be written, based on Roy Arends' May 11th message to namedroppers.

2.3  Validating Responses to an ANY Query

   RFC4035 does not address now to validate responses when QTYPE=*.  As
   described in Section 6.2.2 of RFC1034, a proper response to QTYPE=*
   may include a subset of the RRsets at a given name -- it is not
   necessary to include all RRsets at the QNAME in the response.

   When validating a response to QTYPE=*, validate all received RRsets
   that match QNAME and QCLASS.  If any of those RRsets fail validation,
   treat the answer as Bogus.  If there are no RRsets matching QNAME and
   QCLASS, validate that fact using the rules in RFC4035 Section 5.4 (as
   clarified in this document).  To be clear, a validator must not
   insist on receiving all records at the QNAME in response to QTYPE=*.

3.  Interoperability Concerns

3.1  Unknown DS Message Digest Algorithms

   Section 5.2 of RFC4035 includes rules for how to handle delegations
   to zones that are signed with entirely unsupported algorithms, as
   indicated by the algorithms shown in those zone's DS RRsets.  It does
   not explicitly address how to handle DS records that use unsupported
   message digest algorithms.  In brief, DS records using unknown or
   unsupported message digest algorithms MUST be treated the same way as
   DS records referring to DNSKEY RRs of unknown or unsupported
   algorithms.

   The existing text says:

      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
      resolver should treat this case as it would the case of an
      authenticated NSEC RRset proving that no DS RRset exists, as
      described above.




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   To paraphrase the above, when determining the security status of a
   zone, a validator discards (for this purpose only) any DS records
   listing unknown or unsupported algorithms.  If none are left, the
   zone is treated as if it were unsigned.

   Modified to consider DS message digest algorithms, a validator also
   discards any DS records using unknown or unsupported message digest
   algorithms.

3.2  Private Algorithms

   As discussed above, section 5.2 of RFC4035 requires that validators
   make decisions about the security status of zones based on the public
   key algorithms shown in the DS records for those zones.  In the case
   of private algorithms, as described in RFC4034 Appendix A.1.1, the
   eight-bit algorithm field in the DS RR is not conclusive about what
   algorithm(s) is actually in use.

   If no private algorithms appear in the DS set or if any supported
   algorithm appears in the DS set, no special processing will be
   needed.  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 3.1).  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