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Re: [dmarc-ietf] WGLC ARC-16 concern on Section 5.1.2 - cv=fail should sign greedily

"Murray S. Kucherawy" <superuser@gmail.com> Fri, 27 July 2018 17:39 UTC

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From: "Murray S. Kucherawy" <superuser@gmail.com>
Date: Fri, 27 Jul 2018 10:39:21 -0700
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To: Seth Blank <seth@sethblank.com>
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Subject: Re: [dmarc-ietf] WGLC ARC-16 concern on Section 5.1.2 - cv=fail should sign greedily
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On Fri, Jul 27, 2018 at 10:29 AM, Seth Blank <seth@sethblank.com> wrote:

> On Fri, Jul 27, 2018 at 10:21 AM, Murray S. Kucherawy <superuser@gmail.com
> > wrote:
>
>> On Fri, Jul 27, 2018 at 8:35 AM, Seth Blank <seth@sethblank.com> wrote:
>>
>>> The verification algorithm is straightforward. If you receive a chain
>>> that ends with cv=fail stop your evaluation, you’re done. There’s no
>>> separate validation path here.
>>>
>>
>> Then why bother signing anything when you affix "cv=fail"?
>>
>
> Because adding your ARC Seal over the chain guarantees that the receiver
> has a complete list of everyone who modified the message up until the
> failure. Without this signature any failures cannot be localized, and any
> ARC data in a failed chain could not be trusted. This data is crucial for
> analysis, understanding the experiment, and reporting back accurate and
> untampered information.
>

But (and I think this proves my point) I don't know if "cv=fail" refers to
an invalid chain or a failed chain.  I have to run the verification to
figure that out.  But you're saying you just stop when you see "cv=fail".

I remain confused.

-MSK

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