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) <[email protected]> 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 <[email protected]> > 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 >> >> *[image: IQVIA logo_96dpi_100pxheight]* >> >> Learn more <http://www.iqvia.com/> about IQVIA™ >> >> >> >> 400 Campus Drive >> >> Collegeville, PA 19426 >> >> USA >> >> >> >> O: +1 610 244 2646 <(610)%20244-2646> | M: +1 484 904 8244 >> <(484)%20904-8244> >> >> >> >> >> ________________________________________ >> *IMPORTANT* - PLEASE READ: This electronic message, including its >> attachments, is CONFIDENTIAL and may contain PROPRIETARY or LEGALLY >> PRIVILEGED or PROTECTED information and is intended for the authorized >> recipient of the sender. If you are not the intended recipient, you are >> hereby notified that any use, disclosure, copying, or distribution of this >> message or any of the information included in it is unauthorized and >> strictly prohibited. If you have received this message in error, please >> immediately notify the sender by reply e-mail and permanently delete this >> message and its attachments, along with any copies thereof, from all >> locations received (e.g., computer, mobile device, etc.). To the extent >> permitted by law, we may monitor electronic communications for the purposes >> of ensuring compliance with our legal and regulatory obligations and >> internal policies. We may also collect email traffic headers for analyzing >> patterns of network traffic and managing client relationships. For further >> information see: https://www.iqvia.com/about-us/privacy/privacy-policy.. >> Thank you. >> >> _______________________________________________ >> dmarc mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/dmarc >> > _______________________________________________ > dmarc mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/dmarc >
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