Re: [dmarc-ietf] ARC Multi Proposal

[Brandon Long <[e-mail]>]

On Fri, Nov 2, 2018 at 2:13 AM Kurt Andersen (b) <[e-mail]> wrote:

> On Fri, Nov 2, 2018, 18:09 John R Levine <[e-mail] wrote:
>
>> On Fri, 2 Nov 2018, Kurt Andersen (b) wrote:
>> >> I mean ARC as it's implemented now, not in our multi-signing draft.
>> > It seems like a poor implementation choice to be enforcing something
>> which
>> > is not part of the spec :-), especially when there are parenthetical
>> > comments and references to things like ARC-MULTI to warn you against
>> > leaping to foot-shooting enforcement choices.
>>
>> I see it also says:
>>
>>     Valid ARC Sets MUST have exactly one instance of each ARC header
>>     field (AAR, AMS, and AS) for a given instance value and signing
>>     algorithm.
>>
>> I'm reasonably sure that doesn't match a lot of running code.  I'm
>> particularly thinking of gmail here.
>>
>
> That should be easy to test but not with a tiny keyboard as I board my
> flight from ICN --> BKK.
>

If it does work, I'd be a surprised.  Most likely, it'll fail validation
prior to full parsing (we extract the i= first, and only fully parse all
the k=v pairs later).

Also, does that mean you have to use the same algorithm in both the AMS and
AS for a given instance?  And how does that correspond to an AAR which
doesn't have an algorithm... and how does that work with the AS signing
previous headers, does it only sign the ones with matching algorithm?

I'd be a bit surprised if all of those caveats are correctly matched in the
original arc spec.

Brandon