Network Working Group                                         M. Andrews
Request for Comments: 4431                   Internet Systems Consortium
Category: Informational                                        S. Weiler
                                                            SPARTA, Inc.
                                                           February 2006


       The DNSSEC Lookaside Validation (DLV) DNS Resource Record

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document defines a new DNS resource record, called the DNSSEC
   Lookaside Validation (DLV) RR, for publishing DNSSEC trust anchors
   outside of the DNS delegation chain.

1.  Introduction

   DNSSEC [1] [2] [3] authenticates DNS data by building public-key
   signature chains along the DNS delegation chain from a trust anchor,
   ideally a trust anchor for the DNS root.

   This document defines a new resource record for publishing such trust
   anchors outside of the DNS's normal delegation chain.  Use of these
   records by DNSSEC validators is outside the scope of this document,
   but it is expected that these records will help resolvers validate
   DNSSEC-signed data from zones whose ancestors either aren't signed or
   refuse to publish delegation signer (DS) records for their children.

2.  DLV Resource Record

   The DLV resource record has exactly the same wire and presentation
   formats as the DS resource record, defined in RFC 4034, Section 5.
   It uses the same IANA-assigned values in the algorithm and digest
   type fields as the DS record.  (Those IANA registries are known as
   the "DNS Security Algorithm Numbers" and "DS RR Type Algorithm
   Numbers" registries.)

   The DLV record is a normal DNS record type without any special
   processing requirements.  In particular, the DLV record does not
   inherit any of the special processing or handling requirements of the
   DS record type (described in Section 3.1.4.1 of RFC 4035).  Unlike
   the DS record, the DLV record may not appear on the parent's side of
   a zone cut.  A DLV record may, however, appear at the apex of a zone.

3.  Security Considerations

   For authoritative servers and resolvers that do not attempt to use
   DLV RRs as part of DNSSEC validation, there are no particular
   security concerns -- DLV RRs are just like any other DNS data.

   Software using DLV RRs as part of DNSSEC validation will almost
   certainly want to impose constraints on their use, but those
   constraints are best left to be described by the documents that more
   fully describe the particulars of how the records are used.  At a
   minimum, it would be unwise to use the records without some sort of
   cryptographic authentication.  More likely than not, DNSSEC itself
   will be used to authenticate the DLV RRs.  Depending on how a DLV RR
   is used, failure to properly authenticate it could lead to
   significant additional security problems including failure to detect
   spoofed DNS data.

   RFC 4034, Section 8, describes security considerations specific to
   the DS RR.  Those considerations are equally applicable to DLV RRs.
   Of particular note, the key tag field is used to help select DNSKEY
   RRs efficiently, but it does not uniquely identify a single DNSKEY
   RR.  It is possible for two distinct DNSKEY RRs to have the same
   owner name, the same algorithm type, and the same key tag.  An
   implementation that uses only the key tag to select a DNSKEY RR might
   select the wrong public key in some circumstances.

   For further discussion of the security implications of DNSSEC, see
   RFC 4033, RFC 4034, and RFC 4035.

4.  IANA Considerations

   IANA has assigned DNS type code 32769 to the DLV resource record from
   the Specification Required portion of the DNS Resource Record Type
   registry, as defined in [4].

   The DLV resource record reuses the same algorithm and digest type
   registries already used for the DS resource record, currently known
   as the "DNS Security Algorithm Numbers" and "DS RR Type Algorithm
   Numbers" registries.

5.  Normative References

   [1]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
        "DNS Security Introduction and Requirements", RFC 4033,
        March 2005.

   [2]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
        "Resource Records for the DNS Security Extensions", RFC 4034,
        March 2005.

   [3]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
        "Protocol Modifications for the DNS Security Extensions",
        RFC 4035, March 2005.

   [4]  Eastlake, D., Brunner-Williams, E., and B. Manning, "Domain Name
        System (DNS) IANA Considerations", BCP 42, RFC 2929,
        September 2000.

Authors' Addresses

   Mark Andrews
   Internet Systems Consortium
   950 Charter St.
   Redwood City, CA  94063
   US

   EMail: Mark_Andrews@isc.org


   Samuel Weiler
   SPARTA, Inc.
   7075 Samuel Morse Drive
   Columbia, Maryland  21046
   US

   EMail: weiler@tislabs.com

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