Network Working Group B. Wellington
Request for Comments: 3008 Nominum
Updates: 2535 November 2000
Category: Standards Track
Domain Name System Security (DNSSEC) Signing Authority
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document proposes a revised model of Domain Name System Security
(DNSSEC) Signing Authority. The revised model is designed to clarify
earlier documents and add additional restrictions to simplify the
secure resolution process. Specifically, this affects the
authorization of keys to sign sets of records.
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 [RFC2119].
1 - Introduction
This document defines additional restrictions on DNSSEC signatures
(SIG) records relating to their authority to sign associated data.
The intent is to establish a standard policy followed by a secure
resolver; this policy can be augmented by local rules. This builds
upon [RFC2535], updating section 2.3.6 of that document.
The most significant change is that in a secure zone, zone data is
required to be signed by the zone key.
Familiarity with the DNS system [RFC1034, RFC1035] and the DNS
security extensions [RFC2535] is assumed.
Wellington Standards Track [Page 1]RFC 3008 DNSSEC Signing Authority November 2000
2 - The SIG Record
A SIG record is normally associated with an RRset, and "covers" (that
is, demonstrates the authenticity and integrity of) the RRset. This
is referred to as a "data SIG". Note that there can be multiple SIG
records covering an RRset, and the same validation process should be
repeated for each of them. Some data SIGs are considered "material",
that is, relevant to a DNSSEC capable resolver, and some are
"immaterial" or "extra-DNSSEC", as they are not relevant to DNSSEC
validation. Immaterial SIGs may have application defined roles. SIG
records may exist which are not bound to any RRset; these are also
considered immaterial. The validation process determines which SIGs
are material; once a SIG is shown to be immaterial, no other
validation is necessary.
SIGs may also be used for transaction security. In this case, a SIG
record with a type covered field of 0 is attached to a message, and
is used to protect message integrity. This is referred to as a
SIG(0) [RFC2535, RFC2931].
The following sections define requirements for all of the fields of a
SIG record. These requirements MUST be met in order for a DNSSEC
capable resolver to process this signature. If any of these
requirements are not met, the SIG cannot be further processed.
Additionally, once a KEY has been identified as having generated this
SIG, there are requirements that it MUST meet.
2.1 - Type Covered
For a data SIG, the type covered MUST be the same as the type of data
in the associated RRset. For a SIG(0), the type covered MUST be 0.
2.2 - Algorithm Number
The algorithm specified in a SIG MUST be recognized by the client,
and it MUST be an algorithm that has a defined SIG rdata format.
2.3 - Labels
The labels count MUST be less than or equal to the number of labels
in the SIG owner name, as specified in [RFC2535, section 4.1.3].
2.4 - Original TTL
The original TTL MUST be greater than or equal to the TTL of the SIG
record itself, since the TTL cannot be increased by intermediate
servers. This field can be ignored for SIG(0) records.
Wellington Standards Track [Page 2]RFC 3008 DNSSEC Signing Authority November 20002.5 - Signature Expiration and Inception
The current time at the time of validation MUST lie within the
validity period bounded by the inception and expiration times.