Re: [dmarc-ietf] ABNF errors on RFC7489 and dmarcbis-07

Douglas Foster <dougfoster.emailstandards@gmail.com> Sat, 23 April 2022 19:15 UTC

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From: Douglas Foster <dougfoster.emailstandards@gmail.com>
Date: Sat, 23 Apr 2022 15:14:48 -0400
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To: John Levine <johnl@taugh.com>
Cc: IETF DMARC WG <dmarc@ietf.org>, rfc@arcsin.de
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Subject: Re: [dmarc-ietf] ABNF errors on RFC7489 and dmarcbis-07
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RFC 7489 says that the p=(none|quarantine|reject) term is required (Section
6.3, page 17).
We could preserve that requirement or state that p=none can also be taken
as a default.

On Sat, Apr 23, 2022 at 1:50 PM John Levine <johnl@taugh.com> wrote:

> It appears that Damian Lukowski  <rfc@arcsin.de> said:
> > From the perspective of a decision problem, there are no unknown DMARC
> tags. If there are syntax errors, then the whole thing is
> >not a DMARC record, in particular it does not consist of valid tag-value
> pairs and invalid tag-value pairs. The record
> >
> >> v=DMARC1; rua=mailto:report@example.com; garbage=101; more-garbage
> >
> >should not yield DMARC reports at all, as there is no DMARC record.
>
> The spec could be worded better, but you are clearly mistaken.
> Anything that starts with "v=DMARC1;" is a DMARC record.
>
> >In my opinion, the spec should either stick to the grammar, or explicitly
> and unambiguously define the parsing procedure.
> >
> >[1] "A DMARC policy record MUST comply with the formal specification
> found in Section 5.4"
>
> Selective quoting is not helpful.  What it actually says is:
>
>   A DMARC policy record MUST comply with the formal specification
>   found in Section 5.4 in that the "v" tag MUST be present and MUST
>   appear first. Unknown tags MUST be ignored. Syntax errors in the
>   remainder of the record SHOULD be discarded in favor of default values
>   (if any) or ignored outright.
>
> As I said before, I think we should fix the spec to agree with the
> practice. The ones I've seen accept an arbitrary list of tag=value
> pairs, ignore any trailing garbage, and do not care about tag order
> other than that v=DMARC1 has to be first.
>
> I definitely would not say that clients have to ignore records wth
> syntax errors, since implmentations will ignore that and do what they
> do how.
>
> Re Ale's question about a the tag registry. I'd make it FCFS rather
> than Specification Required since there is no risk of running out of
> tag names. I'd rather know about all the tags people use, even poorly
> specified ones, so we can avoid name collisions.
>
> R's,
> John
>
>
>
>
>
>
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