> -----Original Message----- > From: ietf-dkim-boun...@mipassoc.org [mailto:ietf-dkim-boun...@mipassoc.org] > On Behalf Of John R. Levine > Sent: Wednesday, October 06, 2010 6:17 AM > To: Steve Atkins > Cc: DKIM List > Subject: Re: [ietf-dkim] THIS IS A MULTIPLE 5322.FROM MESSAGE > > Recall that the original question was about a valid message with a > valid signature, which the attacker mutated by adding an extra header > that makes it an invalid message with a signature that still > mechanically verifies. > Who's responsible for it now? > > Is it DKIM's job to make the verification fail, or is it an MUA's job > to do something reasonable with malformed messages?
Yeah, this just occurred to me as well. Any application (signer/verifier, spam filter, MLM, user agent, whatever, even if it has nothing to do with DKIM) that bases its actions on header fields but doesn't check for valid format first may have this vulnerability in some form. For example, an MLM that authenticates a poster based on one From: field while MUAs might render a different one has the very same problem. Trying to deal with this in 4871bis almost seems pointless when the issue is scaled that far. _______________________________________________ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
