MH Michael Hammer (5304):
-----Original Message-----
From: ietf-dkim-bounces(_at_)mipassoc(_dot_)org [mailto:ietf-dkim-
bounces(_at_)mipassoc(_dot_)org] On Behalf Of
Bill(_dot_)Oxley(_at_)cox(_dot_)com
Sent: Friday, October 15, 2010 11:59 AM
To: dcrocker(_at_)bbiw(_dot_)net
Cc: ietf-dkim(_at_)mipassoc(_dot_)org
Subject: Re: [ietf-dkim] detecting header mutations after signing
Well a broken signature is morally equivalent to unsigned so Im not
sure
of the potential harm...
And this is where I angst. In all the discussions of a broken signature
being morally equivalent to unsigned, the thrust has been that it was
likely broken in transit. We failed to have the discussion of it being
intentionally broken in transit as an attempt to game the system. For
header mutations after signing (which are likely to be a malicious
attempt in the specific cases we have been discussing) I feel that
treating it as simply the same as unsigned is ignoring the potential
maliciousness.
I'm sure this was discussed before, but perhaps a refresher helps.
How would the DKIM validator know the difference between:
A: The message had a valid signature, but it was broken after
signing.
B: The message is a forgery with a bogus signature.
If the DKIM validator cannot make that distinction, then the bad
guys will do B and the validator will treat it as A.
Wietse
_______________________________________________
NOTE WELL: This list operates according to
http://mipassoc.org/dkim/ietf-list-rules.html