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Re: [dmarc-ietf] Clarifying the value of arc.closest-fail

"Kurt Andersen (b)" <kboth@drkurt.com> Wed, 03 January 2018 01:56 UTC

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From: "Kurt Andersen (b)" <kboth@drkurt.com>
Date: Wed, 03 Jan 2018 01:56:53 +0000
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To: Bron Gondwana <brong@fastmailteam.com>
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Subject: Re: [dmarc-ietf] Clarifying the value of arc.closest-fail
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On Wed, Jan 3, 2018 at 12:39 AM, Bron Gondwana <brong@fastmailteam.com>
wrote:

> On Wed, 3 Jan 2018, at 04:34, Kurt Andersen (b) wrote:
>
> As I went through the edits for https://tools.ietf.org/htm
> l/draft-ietf-dmarc-arc-protocol-10#section-5.2.1 I was unable to
> understand the value added by having the "arc.closest-fail" listed in the
> AAR.
>
> Without a closest-fail from each step, or a similar way to determine
> changes, information about abuses gets lost along the chain, and the final
> receiver can't tell who modified the message along the way.
>

So, if we have a message that goes through four mailing lists before final
delivery, each of which modify the subject and everyone is "doing the right
thing" (I know that's not exactly an abuse scenario), we would expect:

* ARC 1: cv=none, closest-fail=0
* ARC 2: cv=pass, closest-fail=0
* ARC 3: cv=pass, closest-fail=1
* ARC 4: cv=pass, closest-fail=2
* final recipient ADMD ARC verifier would find cv=pass and evaluate
closest-fail at 3

Is that what you have in mind?

--Kurt

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