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Re: [dmarc-ietf] Second WGLC for draft-ietf-dmarc-psd: Definition of NP

"Kurt Andersen (b)" <kboth@drkurt.com> Fri, 20 November 2020 16:52 UTC

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From: "Kurt Andersen (b)" <kboth@drkurt.com>
Date: Fri, 20 Nov 2020 08:52:41 -0800
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To: Doug Foster <fosterd=40bayviewphysicians.com@dmarc.ietf.org>
Cc: "dmarc@ietf.org" <dmarc@ietf.org>
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Subject: Re: [dmarc-ietf] Second WGLC for draft-ietf-dmarc-psd: Definition of NP
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On Fri, Nov 20, 2020 at 5:57 AM Doug Foster <fosterd=
40bayviewphysicians.com@dmarc.ietf.org> wrote:

>
> However, spoofing of non-existent subdomains is a potential problem for the
> RFC5321.MailFrom domain, which then becomes an attack vector for the
> RFC5322.From address as well.  The problem exists because because SPF has
> no
> organizational default.
>
> We need to think about intermediate nodes, non-mail leaf nodes, and
> non-existent subdomains.  Assume that a spammer tries to spoof a legitimate
> organization by using a non-mail  or non-existing node for both the SMTP
> MailFrom address and the message From Address.   The message will be
> evaluated as
> - SPF=None,
> - DomainAligned=True, and
> - (if checked by some unknown algorithm)  OrganizationReputation=good.
>
>

Presuming no DKIM signature is involved, SPF=None is not the required
"PASS" that DMARC enforces so I don't see the point of your argument.

--Kurt

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