786 lines
31 KiB
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786 lines
31 KiB
Plaintext
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Network Working Group S. Weiler
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Internet-Draft SPARTA, Inc.
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Updates: 4033, 4034, 4035, 5155 D. Blacka
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(if approved) VeriSign, Inc.
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Intended status: Standards Track November 10, 2010
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Expires: May 14, 2011
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Clarifications and Implementation Notes for DNSSECbis
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draft-ietf-dnsext-dnssec-bis-updates-12
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Abstract
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This document is a collection of technical clarifications to the
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DNSSECbis document set. It is meant to serve as a resource to
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implementors as well as a repository of DNSSECbis errata.
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Status of this Memo
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This Internet-Draft is submitted in full conformance with the
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provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF). Note that other groups may also distribute
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working documents as Internet-Drafts. The list of current Internet-
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Drafts is at http://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
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and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
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material or to cite them other than as "work in progress."
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This Internet-Draft will expire on May 14, 2011.
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Copyright Notice
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Copyright (c) 2010 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Provisions Relating to IETF Documents
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(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
|
||
to this document. Code Components extracted from this document must
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
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described in the Simplified BSD License.
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Weiler & Blacka Expires May 14, 2011 [Page 1]
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Internet-Draft DNSSECbis Implementation Notes November 2010
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Table of Contents
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1. Introduction and Terminology . . . . . . . . . . . . . . . . . 3
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1.1. Structure of this Document . . . . . . . . . . . . . . . . 3
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1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
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2. Important Additions to DNSSSECbis . . . . . . . . . . . . . . 3
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2.1. NSEC3 Support . . . . . . . . . . . . . . . . . . . . . . 3
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2.2. SHA-2 Support . . . . . . . . . . . . . . . . . . . . . . 4
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3. Scaling Concerns . . . . . . . . . . . . . . . . . . . . . . . 4
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3.1. Implement a BAD cache . . . . . . . . . . . . . . . . . . 4
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4. Security Concerns . . . . . . . . . . . . . . . . . . . . . . 4
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4.1. Clarifications on Non-Existence Proofs . . . . . . . . . . 4
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4.2. Validating Responses to an ANY Query . . . . . . . . . . . 5
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4.3. Check for CNAME . . . . . . . . . . . . . . . . . . . . . 5
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4.4. Insecure Delegation Proofs . . . . . . . . . . . . . . . . 5
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5. Interoperability Concerns . . . . . . . . . . . . . . . . . . 5
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5.1. Errors in Canonical Form Type Code List . . . . . . . . . 6
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5.2. Unknown DS Message Digest Algorithms . . . . . . . . . . . 6
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5.3. Private Algorithms . . . . . . . . . . . . . . . . . . . . 6
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5.4. Caution About Local Policy and Multiple RRSIGs . . . . . . 7
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5.5. Key Tag Calculation . . . . . . . . . . . . . . . . . . . 7
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5.6. Setting the DO Bit on Replies . . . . . . . . . . . . . . 8
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5.7. Setting the AD Bit on Queries . . . . . . . . . . . . . . 8
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5.8. Setting the AD Bit on Replies . . . . . . . . . . . . . . 8
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5.9. Handling Queries With the CD Bit Set . . . . . . . . . . . 8
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5.10. Nested Trust Anchors . . . . . . . . . . . . . . . . . . . 9
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5.10.1. Closest Encloser . . . . . . . . . . . . . . . . . . 9
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5.10.2. Accept Any Success . . . . . . . . . . . . . . . . . 9
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5.10.3. Preference Based on Source . . . . . . . . . . . . . 10
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6. Minor Corrections and Clarifications . . . . . . . . . . . . . 10
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6.1. Finding Zone Cuts . . . . . . . . . . . . . . . . . . . . 10
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6.2. Clarifications on DNSKEY Usage . . . . . . . . . . . . . . 11
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6.3. Errors in Examples . . . . . . . . . . . . . . . . . . . . 11
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6.4. Errors in RFC 5155 . . . . . . . . . . . . . . . . . . . . 11
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7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
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8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
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9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
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9.1. Normative References . . . . . . . . . . . . . . . . . . . 12
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9.2. Informative References . . . . . . . . . . . . . . . . . . 13
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Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 13
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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Weiler & Blacka Expires May 14, 2011 [Page 2]
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Internet-Draft DNSSECbis Implementation Notes November 2010
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1. Introduction and Terminology
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This document lists some additions, clarifications and corrections to
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the core DNSSECbis specification, as originally described in
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[RFC4033], [RFC4034], and [RFC4035], and later amended by [RFC5155].
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(See section Section 2 for more recent additions to that core
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document set.)
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It is intended to serve as a resource for implementors and as a
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repository of items that need to be addressed when advancing the
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DNSSECbis documents from Proposed Standard to Draft Standard.
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1.1. Structure of this Document
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The clarifications to DNSSECbis are sorted according to their
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importance, starting with ones which could, if ignored, lead to
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security problems and progressing down to clarifications that are
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expected to have little operational impact.
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1.2. Terminology
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in [RFC2119].
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2. Important Additions to DNSSSECbis
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This section lists some documents that should be considered core
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DNSSEC protocol documents in addition to those originally specified
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in Section 10 of [RFC4033].
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2.1. NSEC3 Support
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[RFC5155] describes the use and behavior of the NSEC3 and NSEC3PARAM
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records for hashed denial of existence. Validator implementations
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are strongly encouraged to include support for NSEC3 because a number
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of highly visible zones are expected to use it. Validators that do
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not support validation of responses using NSEC3 will likely be
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hampered in validating large portions of the DNS space.
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[RFC5155] should be considered part of the DNS Security Document
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Family as described by [RFC4033], Section 10.
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Note that the algorithm identifiers defined in RFC5155 (DSA-NSEC3-
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SHA1 and RSASHA1-NSEC3-SHA1) and RFC5702 (RSASHA256 and RSASHA512)
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signal that a zone MAY be using NSEC3, rather than NSEC. The zone
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MAY indeed be using either and validators supporting these algorithms
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Weiler & Blacka Expires May 14, 2011 [Page 3]
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Internet-Draft DNSSECbis Implementation Notes November 2010
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MUST support both NSEC3 and NSEC responses.
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2.2. SHA-2 Support
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[RFC4509] describes the use of SHA-256 as a digest algorithm in
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Delegation Signer (DS) RRs. [RFC5702] describes the use of the
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RSASHA256 and RSASHA512 algorithms in DNSKEY and RRSIG RRs.
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Validator implementations are strongly encouraged to include support
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for these algorithms for DS, DNSKEY, and RRSIG records.
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Both [RFC4509] and [RFC5702] should also be considered part of the
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DNS Security Document Family as described by [RFC4033], Section 10.
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3. Scaling Concerns
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3.1. Implement a BAD cache
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Section 4.7 of RFC4035 permits security-aware resolvers to implement
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a BAD cache. Because of scaling concerns not discussed in this
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document, that guidance has changed: security-aware resolvers SHOULD
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implement a BAD cache, as described in RFC4035.
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4. Security Concerns
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This section provides clarifications that, if overlooked, could lead
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to security issues.
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4.1. Clarifications on Non-Existence Proofs
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[RFC4035] Section 5.4 under-specifies the algorithm for checking non-
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existence proofs. In particular, the algorithm as presented would
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incorrectly allow an NSEC or NSEC3 RR from an ancestor zone to prove
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the non-existence of RRs in the child zone.
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An "ancestor delegation" NSEC RR (or NSEC3 RR) is one with:
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o the NS bit set,
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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,
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or the original owner name for the NSEC3 RR.
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Ancestor delegation NSEC or NSEC3 RRs MUST NOT be used to assume non-
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existence of any RRs below that zone cut, which include all RRs at
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that (original) owner name other than DS RRs, and all RRs below that
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owner name regardless of type.
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Weiler & Blacka Expires May 14, 2011 [Page 4]
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Internet-Draft DNSSECbis Implementation Notes November 2010
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Similarly, the algorithm would also allow an NSEC RR at the same
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owner name as a DNAME RR, or an NSEC3 RR at the same original owner
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name as a DNAME, to prove the non-existence of names beneath that
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DNAME. An NSEC or NSEC3 RR with the DNAME bit set MUST NOT be used
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to assume the non-existence of any subdomain of that NSEC/NSEC3 RR's
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(original) owner name.
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4.2. Validating Responses to an ANY Query
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[RFC4035] does not address how to validate responses when QTYPE=*.
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As described in Section 6.2.2 of [RFC1034], a proper response to
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QTYPE=* may include a subset of the RRsets at a given name. That is,
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it is not necessary to include all RRsets at the QNAME in the
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response.
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When validating a response to QTYPE=*, all received RRsets that match
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QNAME and QCLASS MUST be validated. If any of those RRsets fail
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validation, the answer is considered Bogus. If there are no RRsets
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matching QNAME and QCLASS, that fact MUST be validated according to
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the rules in [RFC4035] Section 5.4 (as clarified in this document).
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To be clear, a validator must not expect to receive all records at
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the QNAME in response to QTYPE=*.
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4.3. Check for CNAME
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Section 5 of [RFC4035] says little about validating responses based
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on (or that should be based on) CNAMEs. When validating a NOERROR/
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NODATA response, validators MUST check the CNAME bit in the matching
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NSEC or NSEC3 RR's type bitmap in addition to the bit for the query
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type. Without this check, an attacker could successfully transform a
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positive CNAME response into a NOERROR/NODATA response.
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4.4. Insecure Delegation Proofs
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[RFC4035] Section 5.2 specifies that a validator, when proving a
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delegation is not secure, needs to check for the absence of the DS
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and SOA bits in the NSEC (or NSEC3) type bitmap. The validator also
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needs to check for the presence of the NS bit in the matching NSEC
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(or NSEC3) RR (proving that there is, indeed, a delegation), or
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alternately make sure that the delegation is covered by an NSEC3 RR
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with the Opt-Out flag set. If this is not checked, spoofed unsigned
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delegations might be used to claim that an existing signed record is
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not signed.
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5. Interoperability Concerns
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Weiler & Blacka Expires May 14, 2011 [Page 5]
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Internet-Draft DNSSECbis Implementation Notes November 2010
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5.1. Errors in Canonical Form Type Code List
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When canonicalizing DNS names, DNS names in the RDATA section of NSEC
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and RRSIG resource records are not downcased.
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[RFC4034] Section 6.2 item 3 has a list of resource record types for
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which DNS names in the RDATA are downcased for purposes of DNSSEC
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canonical form (for both ordering and signing). That list
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erroneously contains NSEC and RRSIG. According to [RFC3755], DNS
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names in the RDATA of NSEC and RRSIG should not be downcased.
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The same section also erroneously lists HINFO, and twice at that.
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Since HINFO records contain no domain names, they are not subject to
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downcasing.
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5.2. Unknown DS Message Digest Algorithms
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Section 5.2 of [RFC4035] includes rules for how to handle delegations
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to zones that are signed with entirely unsupported public key
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algorithms, as indicated by the key algorithms shown in those zone's
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DS RRsets. It does not explicitly address how to handle DS records
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that use unsupported message digest algorithms. In brief, DS records
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using unknown or unsupported message digest algorithms MUST be
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treated the same way as DS records referring to DNSKEY RRs of unknown
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or unsupported public key algorithms.
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The existing text says:
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If the validator does not support any of the algorithms listed in
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an authenticated DS RRset, then the resolver has no supported
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authentication path leading from the parent to the child. The
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resolver should treat this case as it would the case of an
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authenticated NSEC RRset proving that no DS RRset exists, as
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described above.
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To paraphrase the above, when determining the security status of a
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zone, a validator disregards any DS records listing unknown or
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unsupported algorithms. If none are left, the zone is treated as if
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it were unsigned.
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Modified to consider DS message digest algorithms, a validator also
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disregards any DS records using unknown or unsupported message digest
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algorithms.
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5.3. Private Algorithms
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As discussed above, section 5.2 of [RFC4035] requires that validators
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make decisions about the security status of zones based on the public
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Weiler & Blacka Expires May 14, 2011 [Page 6]
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Internet-Draft DNSSECbis Implementation Notes November 2010
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key algorithms shown in the DS records for those zones. In the case
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of private algorithms, as described in [RFC4034] Appendix A.1.1, the
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eight-bit algorithm field in the DS RR is not conclusive about what
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algorithm(s) is actually in use.
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If no private algorithms appear in the DS set or if any supported
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algorithm appears in the DS set, no special processing will be
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needed. In the remaining cases, the security status of the zone
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depends on whether or not the resolver supports any of the private
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algorithms in use (provided that these DS records use supported hash
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functions, as discussed in Section 5.2). In these cases, the
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resolver MUST retrieve the corresponding DNSKEY for each private
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algorithm DS record and examine the public key field to determine the
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algorithm in use. The security-aware resolver MUST ensure that the
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hash of the DNSKEY RR's owner name and RDATA matches the digest in
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the DS RR. If they do not match, and no other DS establishes that
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the zone is secure, the referral should be considered Bogus data, as
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discussed in [RFC4035].
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This clarification facilitates the broader use of private algorithms,
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as suggested by [RFC4955].
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5.4. Caution About Local Policy and Multiple RRSIGs
|
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When multiple RRSIGs cover a given RRset, [RFC4035] Section 5.3.3
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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
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conflicts if these RRSIG RRs lead to differing results." In most
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cases, a resolver would be well advised to accept any valid RRSIG as
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||
sufficient. If the first RRSIG tested fails validation, a resolver
|
||
would be well advised to try others, giving a successful validation
|
||
result if any can be validated and giving a failure only if all
|
||
RRSIGs fail validation.
|
||
|
||
If a resolver adopts a more restrictive policy, there's a danger that
|
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properly-signed data might unnecessarily fail validation, perhaps
|
||
because of cache timing issues. Furthermore, certain zone management
|
||
techniques, like the Double Signature Zone-signing Key Rollover
|
||
method described in section 4.2.1.2 of [RFC4641] might not work
|
||
reliably.
|
||
|
||
5.5. Key Tag Calculation
|
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|
||
[RFC4034] Appendix B.1 incorrectly defines the Key Tag field
|
||
calculation for algorithm 1. It correctly says that the Key Tag is
|
||
the most significant 16 of the least significant 24 bits of the
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||
public key modulus. However, [RFC4034] then goes on to incorrectly
|
||
say that this is 4th to last and 3rd to last octets of the public key
|
||
|
||
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||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 7]
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Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
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modulus. It is, in fact, the 3rd to last and 2nd to last octets.
|
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|
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5.6. Setting the DO Bit on Replies
|
||
|
||
As stated in [RFC3225], the DO bit of the query MUST be copied in the
|
||
response. At least one implementation has done something different,
|
||
so it may be wise for resolvers to be liberal in what they accept.
|
||
|
||
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
|
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the AD bit without also requesting DNSSEC data via the DO bit.
|
||
|
||
5.8. Setting the AD Bit on Replies
|
||
|
||
Section 3.2.3 of [RFC4035] describes under which conditions a
|
||
validating resolver should set or clear the AD bit in a response. In
|
||
order to protect legacy stub resolvers and middleboxes, validating
|
||
resolvers SHOULD only set the AD bit when a response both meets the
|
||
conditions listed in RFC 4035, section 3.2.3, and the request
|
||
contained either a set DO bit or a set AD bit.
|
||
|
||
5.9. Handling Queries With the CD Bit Set
|
||
|
||
When processing a request with the CD bit set, a resolver SHOULD
|
||
attempt to return all responsive data, even data that has failed
|
||
DNSSEC validation. RFC4035 section 3.2.2 requires a resolver
|
||
processing a request with the CD bit set to set the CD bit on its
|
||
upstream queries.
|
||
|
||
The guidance in RFC4035 is ambiguous about what to do when a cached
|
||
response was obtained with the CD bit not set. In the typical case,
|
||
no new query is required, nor 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 permits caching of server failures for
|
||
up to five minutes.) In these cases, a new query with the CD bit set
|
||
is required.
|
||
|
||
For efficiency, a validator SHOULD set the CD bit on upstream queries
|
||
when it has a trust anchor at or above the QNAME (and thus can
|
||
reasonably expect to be able to validate the response).
|
||
|
||
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 8]
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Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
||
5.10. Nested Trust Anchors
|
||
|
||
A DNSSEC validator may be configured such that, for a given response,
|
||
more than one trust anchor could be used to validate the chain of
|
||
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
|
||
"www.sub.zone.example.", either trust anchor could apply.
|
||
|
||
When presented with this situation, DNSSEC validators have a choice
|
||
of which trust anchor(s) to use. Which to use is a matter of
|
||
implementation choice. It is possible and perhaps advisable to
|
||
expose the choice of policy as a configuration option. The rest of
|
||
this section discusses some possible policies. As a default, we
|
||
suggest that validators implement the "Accept Any Success" policy
|
||
described below in Section 5.10.2 while exposing other policies as
|
||
configuration options.
|
||
|
||
5.10.1. Closest Encloser
|
||
|
||
One policy is to choose the trust anchor closest to the QNAME of the
|
||
response. In our example, that would be the "zone.example." trust
|
||
anchor.
|
||
|
||
This policy has the advantage of allowing the operator to trivially
|
||
override a parent zone's trust anchor with one that the operator can
|
||
validate in a stronger way, perhaps because the resolver operator is
|
||
affiliated with the zone in question. This policy also minimizes the
|
||
number of public key operations needed, which may be of benefit in
|
||
resource-constrained environments.
|
||
|
||
This policy has the disadvantage of possibly giving the user some
|
||
unexpected and unnecessary validation failures when sub-zone trust
|
||
anchors are neglected. As a concrete example, consider a validator
|
||
that configured a trust anchor for "zone.example." in 2009 and one
|
||
for "example." in 2011. In 2012, "zone.example." rolls its KSK and
|
||
updates its DS records, but the validator operator doesn't update its
|
||
trust anchor. With the "closest encloser" policy, the validator gets
|
||
validation failures.
|
||
|
||
5.10.2. Accept Any Success
|
||
|
||
Another policy is to try all applicable trust anchors until one gives
|
||
a validation result of Secure, in which case 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 there is no Secure
|
||
result, then the final validation result is Bogus.
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 9]
|
||
|
||
Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
||
This has the advantage of causing the fewer validation failures,
|
||
which may deliver a better user experience. If one trust anchor is
|
||
out of date (as in our above example), the user may still be able to
|
||
get a Secure validation result (and see DNS responses).
|
||
|
||
This policy has the disadvantage of making the validator subject to
|
||
compromise of the weakest of these trust anchors while making its
|
||
relatively painless to keep old trust anchors configured in
|
||
perpetuity.
|
||
|
||
5.10.3. Preference Based on Source
|
||
|
||
When the trust anchors have come from different sources (e.g.
|
||
automated updates ([RFC5011]), one or more DLV registries
|
||
([RFC5074]), and manually configured), a validator may wish to choose
|
||
between them based on the perceived reliability of those sources.
|
||
The order of precedence might be exposed as a configuration option.
|
||
|
||
For example, a validator might choose to prefer trust anchors found
|
||
in a DLV registry over those manually configured on the theory that
|
||
the manually configured ones will not be as aggressively maintained.
|
||
|
||
Conversely, a validator might choose to prefer manually configured
|
||
trust anchors over those obtained from a DLV registry on the theory
|
||
that the manually configured ones have been more carefully
|
||
authenticated.
|
||
|
||
Or the validator might do something more complicated: prefer a sub-
|
||
set of manually configured trust anchors (based on a configuration
|
||
option), then trust anchors that have been updated using the RFC5011
|
||
mechanism, then trust anchors from one DLV registry, then trust
|
||
anchors from a different DLV registry, then the rest of the manually
|
||
configured trust anchors.
|
||
|
||
|
||
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
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 10]
|
||
|
||
Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
||
[RFC4035] specifies a mechanism for doing that.
|
||
|
||
6.2. Clarifications on DNSKEY Usage
|
||
|
||
Questions of the form "can I use a different DNSKEY for signing this
|
||
RRset" have occasionally arisen.
|
||
|
||
The short answer is "yes, absolutely". You can even use a different
|
||
DNSKEY for each RRset in a zone, subject only to practical limits on
|
||
the size of the DNSKEY RRset. However, be aware that there is no way
|
||
to tell resolvers what a particularly DNSKEY is supposed to be used
|
||
for -- any DNSKEY in the zone's signed DNSKEY RRset may be used to
|
||
authenticate any RRset in the zone. For example, if a weaker or less
|
||
trusted DNSKEY is being used to authenticate NSEC RRsets or all
|
||
dynamically updated records, that same DNSKEY can also be used to
|
||
sign any other RRsets from the zone.
|
||
|
||
Furthermore, note that the SEP bit setting has no effect on how a
|
||
DNSKEY may be used -- the validation process is specifically
|
||
prohibited from using that bit by [RFC4034] section 2.1.2. It is
|
||
possible to use a DNSKEY without the SEP bit set as the sole secure
|
||
entry point to the zone, yet use a DNSKEY with the SEP bit set to
|
||
sign all RRsets in the zone (other than the DNSKEY RRset). It's also
|
||
possible to use a single DNSKEY, with or without the SEP bit set, to
|
||
sign the entire zone, including the DNSKEY RRset itself.
|
||
|
||
6.3. Errors in Examples
|
||
|
||
The text in [RFC4035] Section C.1 refers to the examples in B.1 as
|
||
"x.w.example.com" while B.1 uses "x.w.example". This is painfully
|
||
obvious in the second paragraph where it states that the RRSIG labels
|
||
field value of 3 indicates that the answer was not the result of
|
||
wildcard expansion. This is true for "x.w.example" but not for
|
||
"x.w.example.com", which of course has a label count of 4
|
||
(antithetically, a label count of 3 would imply the answer was the
|
||
result of a wildcard expansion).
|
||
|
||
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.
|
||
|
||
6.4. Errors in RFC 5155
|
||
|
||
A NSEC3 record that matches an Empty Non-Terminal effectively has no
|
||
type associated with it. This NSEC3 record has an empty type bit
|
||
map. Section 3.2.1 of [RFC5155] contains the statement:
|
||
|
||
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 11]
|
||
|
||
Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
||
Blocks with no types present MUST NOT be included.
|
||
|
||
However, the same section contains a regular expression:
|
||
|
||
Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )+
|
||
|
||
The plus sign in the regular expression indicates that there is one
|
||
or more of the preceding element. This means that there must be at
|
||
least one window block. If this window block has no types, it
|
||
contradicts with the first statement. Therefore, the correct text in
|
||
RFC 5155 3.2.1 should be:
|
||
|
||
Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )*
|
||
|
||
|
||
7. IANA Considerations
|
||
|
||
This document specifies no IANA Actions.
|
||
|
||
|
||
8. Security Considerations
|
||
|
||
This document adds two cryptographic features to the core DNSSEC
|
||
protocol. Additionally, it addresses some ambiguities and omissions
|
||
in the core DNSSEC documents that, if not recognized and addressed in
|
||
implementations, could lead 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 the interoperability concerns in Section 5
|
||
could limit the ability to later change or expand DNSSEC, including
|
||
adding new algorithms.
|
||
|
||
|
||
9. References
|
||
|
||
9.1. Normative References
|
||
|
||
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
|
||
STD 13, RFC 1034, November 1987.
|
||
|
||
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
|
||
Requirement Levels", BCP 14, RFC 2119, March 1997.
|
||
|
||
[RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC",
|
||
RFC 3225, December 2001.
|
||
|
||
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
|
||
Rose, "DNS Security Introduction and Requirements",
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 12]
|
||
|
||
Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
||
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.
|
||
|
||
[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.
|
||
|
||
[RFC5702] Jansen, J., "Use of SHA-2 Algorithms with RSA in DNSKEY
|
||
and RRSIG Resource Records for DNSSEC", RFC 5702,
|
||
October 2009.
|
||
|
||
9.2. Informative References
|
||
|
||
[RFC3755] Weiler, S., "Legacy Resolver Compatibility for Delegation
|
||
Signer (DS)", RFC 3755, May 2004.
|
||
|
||
[RFC4641] Kolkman, O. and R. Gieben, "DNSSEC Operational Practices",
|
||
RFC 4641, September 2006.
|
||
|
||
[RFC4955] Blacka, D., "DNS Security (DNSSEC) Experiments", RFC 4955,
|
||
July 2007.
|
||
|
||
[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
|
||
Trust Anchors", RFC 5011, September 2007.
|
||
|
||
[RFC5074] Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
|
||
November 2007.
|
||
|
||
|
||
Appendix A. Acknowledgments
|
||
|
||
The editors would like the thank Rob Austein for his previous work as
|
||
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
|
||
provided text suitable for inclusion in this document.
|
||
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 13]
|
||
|
||
Internet-Draft DNSSECbis Implementation Notes November 2010
|
||
|
||
|
||
The lack of specificity about handling private algorithms, as
|
||
described in Section 5.3, and the lack of specificity in handling ANY
|
||
queries, as described in Section 4.2, were discovered by David
|
||
Blacka.
|
||
|
||
The error in algorithm 1 key tag calculation, as described in
|
||
Section 5.5, was found by Abhijit Hayatnagarkar. Donald Eastlake
|
||
contributed text for Section 5.5.
|
||
|
||
The bug relating to delegation NSEC RR's in Section 4.1 was found by
|
||
Roy Badami. Roy Arends found the related problem with DNAME.
|
||
|
||
The errors in the [RFC4035] examples were found by Roy Arends, who
|
||
also contributed text for Section 6.3 of this document.
|
||
|
||
The editors would like to thank Alfred Hoenes, Ed Lewis, Danny Mayer,
|
||
Olafur Gudmundsson, Suzanne Woolf, Rickard Bellgrim, Mike St. Johns,
|
||
and Scott Rose for their substantive comments on the text of this
|
||
document.
|
||
|
||
|
||
Authors' Addresses
|
||
|
||
Samuel Weiler
|
||
SPARTA, Inc.
|
||
7110 Samuel Morse Drive
|
||
Columbia, Maryland 21046
|
||
US
|
||
|
||
Email: weiler@tislabs.com
|
||
|
||
|
||
David Blacka
|
||
VeriSign, Inc.
|
||
21345 Ridgetop Circle
|
||
Dulles, VA 20166
|
||
US
|
||
|
||
Email: davidb@verisign.com
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Weiler & Blacka Expires May 14, 2011 [Page 14]
|
||
|
||
|