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Re: Musing on SIP and SPAM and SMTP authentication-like things

Benjamin Kaduk <kaduk@mit.edu> Fri, 01 May 2020 22:07 UTC

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Date: Fri, 01 May 2020 15:07:20 -0700
From: Benjamin Kaduk <kaduk@mit.edu>
To: John R Levine <johnl@taugh.com>
Cc: IETF general list <ietf@ietf.org>
Subject: Re: Musing on SIP and SPAM and SMTP authentication-like things
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On Tue, Apr 28, 2020 at 05:10:21PM -0400, John R Levine wrote:
> On Tue, 28 Apr 2020, John C Klensin wrote:
> > While I don't think it would be useful in any realistic case I
> > can think of, I don't think anything in RFC 4954 would prevent a
> > delivery-end server from advertising the extension and an
> > intermediate MTA relay from using it.  That would provide some
> > validation of (or independent of) the argument to the EHLO
> > command that did not depend on IP addresses. ...
> 
> Sure, it's easy to imagine ways one might make arrangements like that. 
> Since SMTP AUTH uses SASL you're mostly limited to shared secrets with 
> counterparties you already know.  (I say mostly since in principle SASL 
> can use OpenID although I don't know anyone who does.)

The bits in draft-ietf-kitten-sasl-saml-ec do get used (IIRC with SASL,
though the doc supports GSS-API as well), but I don't think that's for
mail.

-Ben

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