On Tue 2019-01-15 01:50:33 -0500, Viktor Dukhovni wrote:
> where the "TCP-Info" in the "BY" clause records the SNI name? Is that
> right? It is an interesting idea, but perhaps that boat had sailed
> many decades ago? Starting with Sendmail versions going back to at
> least the mid 1980's, the "comment" after the "BY" clause has been
> used primarily used to record the MTA software version, though usages
> do very. Here are some trace headers from a single message:
>
> Received: from zardoc.esmtp.org (zardoc.esmtp.org [75.101.48.117])
> (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
> (No client certificate requested)
> by mournblade.imrryr.org (Postfix) with ESMTPS id AB5307A3309
> for <[email protected]>; Fri, 22 Jun 2018 16:30:20 +0000 (UTC)
> (envelope-from [email protected])
> Received: from x2.esmtp.org (localhost. [127.0.0.1])
> by zardoc.esmtp.org (MeTA1-1.1.Alpha10.0) with ESMTPS
> (TLS=TLSv1.2, cipher=ECDHE-RSA-AES256-GCM-SHA384, bits=256, verify=OK)
> id S000000000033346B00; Fri, 22 Jun 2018 09:30:18 -0700
> Received: (from ...@localhost)
> by x2.esmtp.org (8.14.6/8.12.10.Beta0/Submit) id w5MGUIOU003106
> for [email protected]; Fri, 22 Jun 2018 09:30:18 -0700 (PDT)
>
> None of the "BY" clauses look like "TCP-Info". Looking at Exim messages in
> my mailbox, it puts no comments after "BY". Only your messages from Qmail
> seem to have transport related information int the comment following the
> "BY" clause...
the TCP-info and the Comment are distinct parenthetical clauses. If you
read the ABNF from 5322 and 5321 closely, you can have both a
parenthetical TCP-info, followed by a parenthetical Comment.
So this is legitimate, afaict:
Received: from bar.example.net (bar.example.net [192.2.0.156])
with ESMTPS by foo.example.org (mx.example.org [192.2.0.15])
(MailTransportAgentPro 1.2.1); Tue, 15 Jan 2019 09:49:30 -0500
The ambiguity comes in if there is exactly one parenthetical, and it
matches the ABNF for a TCP-info. then it's not clear whether it was
intended as a TCP-info, or is a free-form comment that happened to
match.
--dkg
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