Subject: authenticated kerberos errors

From: Michael Thomas <[email-masked]>
Date: Thu, 13 Sep 2001 16:25:56 -0700 (PDT)

The packetcable security spec requires that the
receiver generate an authenticator if it is able
to do so when it generates a krb-error. The
current KINK draft is silent on this matter. I've
been looking at the MIT code (5-1.1.1) and it
appears that this is something new from the kerb
revisions, and that it is not supported.

Here's the question: while we should clearly not
*disallow* the new authenticator in KINK, it's not
very clear to me that KINK should be mandating new
features from the kerberos revisions like
packetcable does. There's a lot of backward
compatibility that we should be wary of, and I'd
really hate to see KINK not be able to work with
off the shelf and running kerberos code.

What do others think?

	Mike

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From: Matthew Hur <[email-masked]>
Date: Tue, 18 Sep 2001 15:46:25 -0700

PacketCable requires the use of the encrypted checksum in the error message 
(not an authenticator).  This has been incorporated in the Kerberos 
revisions for quite some time.  Furthermore, it is already supported in 
some commercial implementations.

I think that we should clearly state that authenticated error messages 
should be used whenever possible.

--Matt

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From: Michael Thomas <[email-masked]>
Date: Wed, 19 Sep 2001 13:01:20 -0700 (PDT)

> should be used whenever possible.

   How about just a "SHOULD"?

	     Mike

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From: Matthew Hur <[email-masked]>
Date: Wed, 19 Sep 2001 15:33:15 -0700

I feel that this should be a MUST.

Whenever possible (meaning, you have a key), the error message should be 
authenticated.  I can think of no good reason that this should be a SHOULD 
rather than a MUST.

--Matt

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From: Jan Vilhuber <[email-masked]>
Date: Wed, 19 Sep 2001 19:52:24 -0700 (PDT)

I'm a bit divided on this. Generally, it's my (possibly faulty) impression
that 'SHOULD's tend to get ignored by a lot of coders. I have seen comments
on the ipsec list to the affect that some people code ONLY the MUSTs (why? To
save time? I don't have a clue). Also, it's then the SHOULDs that wind up
causing interop problems.

On the other hand a MUST is a bit strong in this case. You said that a 'few'
commercial kerberos implementations support this. That raises the question of
how many don't and whether we want to make sure to interoperate with them or
not.

On the gripping hand, we know from IKE that authenticated messages are a good
thing, and we should (must? ;) have as many of them as we can to improve
communication between the peers and hence robustness of the protocol...

Sigh... I guess I'm just stating fact, and will now fade back into the
background, not having shed light on anything.

jan

 --
Jan Vilhuber                                            [email-masked]
Cisco Systems, San Jose                                     (408) 527-0847