RFC 2831 (rfc2831) - Page 2 of 27

Using Digest Authentication as a SASL Mechanism

RFC 2831                 Digest SASL Mechanism                  May 2000


    3.4 ONLINE DICTIONARY ATTACKS....................................16
    3.5 OFFLINE DICTIONARY ATTACKS...................................16
    3.6 MAN IN THE MIDDLE............................................17
    3.7 CHOSEN PLAINTEXT ATTACKS.....................................17
    3.8 SPOOFING BY COUNTERFEIT SERVERS..............................17
    3.9 STORING PASSWORDS............................................17
    3.10 MULTIPLE REALMS.............................................18
    3.11 SUMMARY.....................................................18
   4 EXAMPLE.........................................................18
   5 REFERENCES......................................................20
   6 AUTHORS' ADDRESSES..............................................21
   7 ABNF............................................................21
    7.1 AUGMENTED BNF................................................21
    7.2 BASIC RULES..................................................23
   8 SAMPLE CODE.....................................................25
   9 FULL COPYRIGHT STATEMENT........................................27

1  Introduction

   This specification describes the use of HTTP Digest Access
   Authentication as a SASL mechanism. The authentication type
   associated with the Digest SASL mechanism is "DIGEST-MD5".

   This specification is intended to be upward compatible with the
   "md5-sess" algorithm of HTTP/1.1 Digest Access Authentication
   specified in [Digest]. The only difference in the "md5-sess"
   algorithm is that some directives not needed in a SASL mechanism have
   had their values defaulted.

   There is one new feature for use as a SASL mechanism: integrity
   protection on application protocol messages after an authentication
   exchange.

   Also, compared to CRAM-MD5, DIGEST-MD5 prevents chosen plaintext
   attacks, and permits the use of third party authentication servers,
   mutual authentication, and optimized reauthentication if a client has
   recently authenticated to a server.

1.1  Conventions and Notation

   This specification uses the same ABNF notation and lexical
   conventions as HTTP/1.1 specification; see appendix A.

   Let { a, b, ... } be the concatenation of the octet strings a, b, ...

   Let H(s) be the 16 octet MD5 hash [RFC 1321] of the octet string s.





Leach & Newman              Standards Track