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Re: [ietf-dkim] Re: Concerns about DKIM and mailiing lists, etc.

2006-03-16 09:41:20
On Thu, Mar 16, 2006 at 10:12:34AM -0600, Arvel Hathcock allegedly wrote:
Every piece of mail I've sent this morning has validated. Really.

That's because it was all Re: and already had the subject line tag.
It's your lucky day.

I'm not sure that's correct.  The l= in Mike's signatures takes care of 
the bits appended by the list to the end.  The z= subject value can be 
used by verifiers to take care of the subject munging this list 
performs.  The verifier then simply replaces the subject text with the 
value from z= that was signed.  That's one way of solving the mailing 
list subject munging problem.

And there-in lies dragons methinks. Do you physically replace the
Subject: so that the final recipient gets the pre-list content or do
you logically replace it for the purposes of verifying?

If the former, you'll likely irritate exactly 50% of the planet that
wants that extra goop, and, you've precluded the possibility of a
smart UA doing that selectively on a per-user basis.

If the latter, then the vector is open for abuse and you'll have to
hope for wide deployment of smart UAs to protect users from this risk.


Mark.
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