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

[John Levine <[e-mail]>]

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.

R's,
John