[apps-discuss] Stanzas of trace fields, was Adoption of draft-kucherawy-received-state

Alessandro Vesely <vesely@tana.it> Fri, 20 January 2012 17:39 UTC

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Date: Fri, 20 Jan 2012 18:39:12 +0100
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Subject: [apps-discuss] Stanzas of trace fields, was Adoption of draft-kucherawy-received-state
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(Subject changed according to topics separation)

On 19/Jan/12 12:44, Ned Freed wrote:
> Sieve is actually an example of this. Sieve can perform tests on
> all occurances of a given field or it can be restricted to look at
> the first, second, Nth, N-1th, etc. occurance. So as long as you
> have some idea of how many Received: fields are added prior to
> delivery in a given environment (and you usually do), you can write
> tests that check the correct field or fields and don't get confused
> by stuff provided by stuff outside the administrative domain (which
> is inherently unreliable).
> 
> But there's no way to test something like "the Foo: field that
> appears after the Nth Bar: field". And an extension that does that
> is going to be very, very ugly, no matter how you slice it. And
> that ugliness is going to make using such an extension quite
> problematic, even for fairly experienced script constructors.

Good point.  However, we already have that situation: see e.g.
http://www.rfc-editor.org/errata_search.php?rfc=5451&eid=2818
(Hey, I did get Murray's approval before posting that :-)

Perhaps, "the Foo: field of the Nth trace stanza" is easier.  We
should just convene that "Received:" fields delimit trace stanzas.

Of course, all the RFCs that mention "trace header fields" say that
these go at the top of the header.  Some of them explicitly mention
"Received:" (quotes below), but also RFC 5322 and RFC 5518 obviously
imply such positioning if we assume that "Received:" is always
present.  Thus, it seems feasible to introduce this concept, in one of
the trace- I-Ds, perhaps?

Quotes (emphasis added):
RFC 4408:
 The Received-SPF header field is a trace field (see [RFC2822] Section
 3.6.7) and SHOULD be prepended to the existing header, above the
 *Received*: field that is generated by the SMTP receiver.

RFC 5436:
                                 If the implementation retains the
 "Received" fields from the triggering message (see above), the "Auto-
 Submitted" field MUST be placed above those "*Received*" fields,
 serving as a boundary between the ones from the triggering message
 and those that will be part of the notification message.

RFC 5451:
     On the presumption that internal MTAs are fully compliant with
     Section 3.6 of [MAIL], and the compliant internal MTAs are using
     their own host names or the ADMD's DNS domain name as the
     "authserv-id" token, the header field proposed here should always
     appear above a *Received*: header added by a trusted MTA.

RFC 6376:
  INFORMATIVE IMPLEMENTATION NOTE: The easiest way to achieve this
  is to insert the DKIM-Signature header field at the beginning of
  the header block.  In particular, it may be placed before any
  existing *Received* header fields.  This is consistent with treating
  DKIM-Signature as a trace header field.