Subject: RE: Protocol Action: GSS Algorithm for TSIG (GSS-TSIG) to Proposed Standard

From: "Levon Esibov" <[email-masked]>
Date: Wed, 24 Jul 2002 12:07:02 -0700

> -----Original Message-----
> From: Brian Wellington [mailto:[email-masked]]
> Sent: Wednesday, July 24, 2002 11:45 AM
> To: Levon Esibov
> Cc: Rob Austein; [email-masked]
> Subject: RE: Protocol Action: GSS Algorithm for TSIG (GSS-TSIG) to
> Proposed Standard
> 

> > [Levon Esibov]
> > Yes, I prefer making modification to TSIG rather than prohibiting
> > GSS-TSIG server to sign responses to unsigned TKEY queries for the
> > following reasons:
> > 1. Allowing response to unsigned TKEY query to be signed enables
> > client-recipient of such message to determine whether the secret key
is
> > indeed established on the server's side.
> 
> Doesn't the verification of the GSSAPI token allow this too?

[Levon Esibov] 
When secret key is established on the server side (major_status is
GSS_S_COMPLETE) and output_token is NULL, then no token needs to be
returned to the client and there is no further processing of any tokens
on the client side. In this case TSIG returned in server's response
would enable client to verify that secret key is indeed established on
the server's side.

> 
> > 2. Enabling GSS-TSIG servers to interoperate with old and new
clients
> > complicates server implementation.
> 
> Yes, but this is a GSS-TSIG issue, not a TSIG issue.  TSIG works and
is
> deployed.  It shouldn't be changed to support old, broken
applications.

[Levon Esibov] 
Brian, 
I don't think this is the right approach. If modifying RFC 2845 (TSIG)
is the "optimal" for customers and development community then we should
do it. If namedroppers believe that modifying GSS-TSIG draft is more
optimal - then I don't object it. But simply closing the door saying
that "it's not TSIG issue" because it works and because it's a proposed
standard is probably not the right approach, especially since suggested
modification does NOT affect working implementations.

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---

From: Brian Wellington <[email-masked]>
Date: Wed, 24 Jul 2002 12:16:38 -0700 (PDT)

> would enable client to verify that secret key is indeed established on

I wish someone had brought this up before.  This is the first time I've 
seen anyone say that the TSIG in this message actually helps with the 
protocol's security.  This really should have come up in April or May when 
the problem was first found.

Maybe the right solution is to change GSS-TSIG so that this can be 
verified within the TKEY exchange, not relying on TSIG.

> modification does NOT affect working implementations.

I've stated my opinion, but we'll see what other people have to say...

Brian

---

From: Paul Vixie <[email-masked]>
Date: Wed, 24 Jul 2002 13:08:40 -0700

> verified within the TKEY exchange, not relying on TSIG.

yes