Re: [dmarc-ietf] Ticket #1 - SPF alignment

[Alessandro Vesely <[e-mail]>]

On Tue 26/Jan/2021 14:14:45 +0100 Scott Kitterman wrote:
> On Tuesday, January 26, 2021 6:54:56 AM EST Alessandro Vesely wrote:
>> On Mon 25/Jan/2021 22:35:09 +0100 Scott Kitterman wrote:
>>> On Monday, January 25, 2021 4:04:33 PM EST Todd Herr wrote:
>>>> May I propose that the section labeled "SPF-Authenticated Identifiers" be
>>>> rewritten as follows:
>>>> 
>>>> [...]
>>>> 
>>>>    The reader should note that SPF alignment checks in DMARC rely solely
>>>>    on the RFC5321.MailFrom domain. This differs from section 2.3 of
>>>>    [@!RFC7208], which recommends that SPF checks be done on not only the
>>>>    "MAIL FROM" but also on a separate check of the "HELO" identity. >
>>> 
>>> I think this is fine, but there is a subtlety to be aware of.
>>> 
>>> If you look at RFC 7208 Section 2.4, when Mail From is null,
>>> postmaster@HELO is the mail from for SPF purposes.  DMARC really can't
>>> change that.
>>> 
>>> As a result, there are cases where Mail From results actually are derived
>>> from HELO and it's unavoidable.
>> 
>> I doubt that SPF filters report envelope-from=postmaster@HELO; more likely
>> they write helo=HELO.  In that case, the paragraph quoted above is
>> deceptive.
>>> I believe the proposed text is clear enough about not using separate HELO
>>> identity results and that's appropriate.
>> 
>> My filter collects SPF results recorded from an upstream SPF filter.  It
>> writes Received-SPF: lines for each identity.  For NDNs, it writes a
>> Received-SPF: for the HELO identity only.  Am I allowed to use that result
>> for DMARC?
> 
> No.  You should only use Mail From results.


So NDNs having only an aligned HELO will never pass DMARC?

And what is a <scope>helo</scope> element in aggregate reports provided for?

The spec says:

          [SPF] can authenticate either the domain that appears in the
    RFC5321.MailFrom (MAIL FROM) portion of [SMTP] or the RFC5321.EHLO/
    HELO domain, or both.

And then:

    In relaxed mode, the [SPF]-authenticated domain and RFC5322.From
    domain must have the same Organizational Domain.  In strict mode,
    only an exact DNS domain match is considered to produce Identifier
    Alignment.

So, consider the following message without DKIM signatures:

HELO example.org
MAIL FROM:<[e-mail]>

Received-SPF: pass (domain example.org
   designates 192.0.2.1 as permitted sender)
   identity=helo; helo=example.org;
Received-SPF: fail (domain of [e-mail]
   denies 192.0.2.1 as permitted sender)
   identity=mailfrom; envelope-from="[e-mail]";
Subject: Not using a mail client for this example
From: [e-mail]

Does it pass DMARC?

Best
Ale
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