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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.)





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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.





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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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Full Copyright Statement

Copyright (C) The Internet Society (2006).

This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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