Re: [dmarc-ietf] Call for Adoption: DMARC Use of the RFC5322.Sender Header Field

[Dotzero <[e-mail]>]

On Thu, Aug 13, 2020 at 8:23 PM Murray S. Kucherawy <[e-mail]>
wrote:

> On Mon, Aug 10, 2020 at 12:05 PM Tim Wicinski <[e-mail]> wrote:
>
>> During IETF 108, the chairs realized that there was interest in Dave's
>> RFC5322.Sender draft.
>>
>> This starts a Call for Adoption for draft-crocker-dmarc-sender
>>
>> The draft is available here:
>> https://datatracker.ietf.org/doc/draft-crocker-dmarc-sender/
>>
>> Currently, the draft is marked as "Standards Track".  The chairs feel if
>> the
>> working group does adopt this, it should begin as "Experimental".  If we
>> start
>> to see adoption of this work, this can be changed back to "Standards
>> Track" before
>> Working Group Last Call.  Of course, we welcome input from the working
>> group on this.
>>
>> Please review this draft to see if you think it is suitable for adoption,
>> and
>> send any comments to the list, clearly stating your view.
>>
>> Please also indicate if you are willing to contribute text, review, etc.
>>
>> This call for adoption ends: 24 August 2020
>>
>
> DISCUSS.
>
> (just kidding; +1 for adoption)
>
> -MSK, participating, except for the joke part, that was with full authority
>
> "DISCUSS" shouldn't really be a joke. draft-crocker-dmarc-sender suffers
from a similar problem as PRA in the SenderId draft. There is no way to
validate that the specific intermediary is authorized by the (From) domain
originating the email through it's generic signalling that it
authorizes intermediaries. This means that any source can emit a message
claiming to be a legitimate intermediary just as any source could game PR
to gain a neutral result. This raises a significant question as to the
value of this proposed draft. It essentially reverts to depending on
reputation as to whether the intermediary's assertions (I'm really really
trustworthy) should be accepted. One could achieve similar outcomes using
only reputation and local policy override of DMARC policy.

The only way a scheme along the lines of the proposed one would be if the
specific intermediary were authorized either through a seperate DKIM
signing of a field (with the intermediary domain ) that would remaintact
even if the DKIM signing of the entire message were broken by the
(authorized) intermediary.

The proposed approach is easily abusable by individuals with malicious
intent.

Michael Hammer