Re: [dmarc-ietf] Question regarding RFC 8617

[Brandon Long <[e-mail]>]

What's more, the point of including Subject and other mutable headers is
the same as it is for DKIM, those are the headers which are important to
the receiver, so they should be validated.

As Kurt points out, the point of ARC is to acknowledge these changes hop to
hop, and the Arc Seal proves who did the change, the question becomes do
you believe
the person who changed it wasn't malicious.

Brandon

On Wed, Nov 6, 2019 at 7:37 AM Kurt Andersen (b) <[e-mail]> wrote:

> The choice of which headers are included in the signed set is strictly up
> to the domain administrators who implement the signing practices. Also, the
> AMS is only relevant for the next receiver, it is not intended to be
> validated by hops >1 step away from the domain which adds that instance so
> I don't see how mutability would matter.
>
> --Kurt Andersen
>
> On Wed, Nov 6, 2019 at 7:30 AM Weist, Bill <[e-mail]>
> wrote:
>
>> DOI:  10.17487/RFC8617
>>
>>
>>
>> The inclusion of the address headers in the signature, and possibly the
>> Subject, is an issue:
>>
>>
>>
>> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=
>> microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
>> bh=;
>>
>>
>>
>> If a downstream server needs to modify either of these two values, the
>> signature check fails.
>>
>>
>>
>> It is my understanding that the Authenticated Received Check signature is
>> to validate the chain of possession.  As such, in my opinion, the signature
>> should only include immutable references.
>>
>>
>>
>> In my opinion, there is value in NOT requiring headers to be stripped by
>> downstream servers, thus maintaining the custody chain from origination to
>> destination.
>>
>>
>>
>> Thank you for your time and attention,
>>
>>
>>
>> *William M. Weist*
>>
>> *Enterprise Architect I – Global Messaging – Mobile and Presence*
>>
>> CIO Team – End User Computing
>>
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