Re: [dmarc-ietf] my forward signer draft, third party authorization, not, was non-mailing list

["Rolf E. Sonneveld" <[e-mail]>]

On 31/08/2020 18:15, John Levine wrote:
> In article <CAL0qLwYuSD8ncf+HXU2B0z1NtrM7cT33vdVh2sUXJ-=[e-mail]> you write:
>> The draft suggests use of "x=" as a way to limit exposure.  If you do that,
>> then an attacker would need to be able to generate mail through your signer
>> with an "!fs=" tag identifying a domain they control, and exploit the
>> replay before the time in the "x=" tag arrives.  Sure, it's time-limited,
>> but it only takes seconds for such an attack to succeed, and automation of
>> such an attack is easy.
> The threats I had in mind were more like attacker finds an old message
> in an archive with a fs domain that's been abandoned and the attacker
> can reregister.  An x= of a few days should prevent that while still
> letting normal list traffic work.
>
> As always, as I hope we all remember DMARC alignment doesn't mean not spam,
> and you still do all of the stuff you do to sort your mail.  This scheme
> depends on the forwarders you authorize being well-behaved.  That's why I
> am concerned that senders need to be selective about who they allow to
> forward.

Yep. I like the proposal, but for me the only question left is: (how) 
will this scale? I'm not (yet) convinced it will.

/rolf