RFC 3007 (rfc3007) - Page 2 of 9

Secure Domain Name System (DNS) Dynamic Update

RFC 3007                 Secure Dynamic Update             November 2000


   This document updates portions of RFC 2535, in particular section
   3.1.2, and RFC 2136.  This document obsoletes RFC 2137, an alternate
   proposal for secure dynamic update, due to implementation experience.

1.1 - Overview of DNS Dynamic Update

   DNS dynamic update defines a new DNS opcode and a new interpretation
   of the DNS message if that opcode is used.  An update can specify
   insertions or deletions of data, along with prerequisites necessary
   for the updates to occur.  All tests and changes for a DNS update
   request are restricted to a single zone, and are performed at the
   primary server for the zone.  The primary server for a dynamic zone
   must increment the zone SOA serial number when an update occurs or
   before the next retrieval of the SOA.

1.2 - Overview of DNS Transaction Security

   Exchanges of DNS messages which include TSIG [RFC 2845] or SIG(0)
   [RFC 2535, RFC 2931] records allow two DNS entities to authenticate DNS
   requests and responses sent between them.  A TSIG MAC (message
   authentication code) is derived from a shared secret, and a SIG(0) is
   generated from a private key whose public counterpart is stored in
   DNS.  In both cases, a record containing the message signature/MAC is
   included as the final resource record in a DNS message.  Keyed
   hashes, used in TSIG, are inexpensive to calculate and verify.
   Public key encryption, as used in SIG(0), is more scalable as the
   public keys are stored in DNS.

1.3 - Comparison of data authentication and message authentication

   Message based authentication, using TSIG or SIG(0), provides
   protection for the entire message with a single signing and single
   verification which, in the case of TSIG, is a relatively inexpensive
   MAC creation and check.  For update requests, this signature can
   establish, based on policy or key negotiation, the authority to make
   the request.

   DNSSEC SIG records can be used to protect the integrity of individual
   RRs or RRsets in a DNS message with the authority of the zone owner.
   However, this cannot sufficiently protect the dynamic update request.

   Using SIG records to secure RRsets in an update request is
   incompatible with the design of update, as described below, and would
   in any case require multiple expensive public key signatures and
   verifications.






Wellington                  Standards Track