Subject: authmeth-02 && (Digest | CRAM-MD5)?

From: [email-masked]
Date: Fri, 04 Sep 1998 09:06:24 -0700

[apologies for cross-post. which single list are we going to discuss (Digest | 
CRAM-MD5) on? Seems [email-masked] is probably the appropriate one.]

Ok, so my understanding is that the Apps-area mandatory-to-impl 
simple-vs-complex auth mechanism lunch occured during the Chicago IETF on Tue 
25-Aug-1998.

My understanding from RLBob Morgan and Paul Hoffman is that at the (lunch) 
meeting, the discussion centered around CRAM vs Digest. The upshot was that 
Paul Leach and Chris Newman are to go off and tweak the Digest spec such that 
Chris' specific concerns are addressed (i.e. there was general consensus that 
Digest is better in specific areas and that we oughta utilize it rather than 
something we know has those problems and then have to change it in the 
near-to-intermediate term).

So, it seems we should be hearing from Paul & Chris about this, presummably on 
one or both of these lists ([email-masked]?).

Are there any first-hand accounts of the meeting someone who was actually 
there would like to publish (i.e. minutes?)?

thanks,

Jeff

---

From: Chris Newman <[email-masked]>
Date: Fri, 04 Sep 1998 12:22:24 -0700 (PDT)

Some observations:

It is very desirable to use the same password backend and authentication
source code for mail/news, directory and web services due to the large
number of products which combine two or more of these services.  This is
easiest to achieve if there is a common mandatory-to-implement baseline
mechanism. It is my understanding that the web community is committed to
the new HTTP digest mechanism.  The mail/news and directory areas aren't
firmly committed to a specific solution yet although there has been
significant movement in the direction of CRAM-MD5 because it's there.

CRAM-MD5 (and APOP and CHAP and the RFC 2069 HTTP-DIGEST) all lack a
client nonce.  This means a rogue server can easily get the password (with
a known plaintext attack) if an incautious client tries to authenticate to
that server.  It's my understanding that the number of clients which will
fall in the "incautious" class may be high.  I don't consider this attack
damning, but it happens to be easy to create a demonstration and use that
to rake a vendor over the coals.

Most people don't see CRAM-MD5 as the best choice for a baseline mechanism
in the long term even though it's much better than clear text.  It's
missing too many useful operational security features.

Conclusions I got from various meetings:

Paul and I will try to come up with an HTTP-digest based SASL mechanism
that's "good enough" operationally to be a mandatory-to-implement baseline
authentication mechanism.  The meeting I had with Paul went well -- I
think the result will be good. 

The current drafts that are nearing last call and need a 
mandatory-to-implement mechanism are:

	LDAP authentication
	NNTP authentication
	On-demand SMTP

We've got informal agreements to hold these drafts for two weeks for the
HTTP-digest based alternative.  Assuming the HTTP-digest based alternative
is issued promptly and it's acceptable to the LDAPEXT WG, it will be last
called along with the LDAP authentication spec.  If the HTTP-digest based
alternative starts causing undue delay in the standards process, then
CRAM-MD5 is the fallback choice. 

		- Chris

---

From: Chris Newman <[email-masked]>
Date: Fri, 04 Sep 1998 12:22:24 -0700 (PDT)

Some observations:

	LDAP authentication
	NNTP authentication
	On-demand SMTP

		- Chris