> -----Original Message----- > From: John R. Levine [mailto:jo...@iecc.com] > Sent: Friday, April 23, 2010 4:04 PM > To: Murray S. Kucherawy > Cc: ietf-dkim@mipassoc.org > Subject: RE: [ietf-dkim] Why mailing lists should strip DKIM signatures > > I am about 99% certain that the FBL reports that started this > discussion > were either a guy who wanted to unsub from the list, or he reported his > whole inbox. Nearly all of the FBL reports I get are one or the other, > but this was the first time I got them for someone else's list. As I > believe I said, it didn't break anything here, but it was a useless > transaction, and for a small site like mine that has users who belong > to a > lot of lists, it could easily dominate FBL traffic.
Unfortunately I expect there to be a level of noise to which we'll just have to become accustomed. This is probably already true in the FBL world anyway. There might be ways to reduce or filter it but any design work I do will expect some. > Well, yes, leaving out irrelevant info avoids misleading them. More > info > is not necessarily better, particularly in a situation like this where > a > recipient doesn't know the order or relationship of multiple signatures > unless it has separate knowledge about the parties involved. Although you seem to have concluded so already, I don't agree that it's irrelevant data. Some verifiers might want to see both as a matter of local policy, and maybe there's an algorithm out there that would work in the majority of cases which requires access to all of the signatures. Absent a proof one way or another, I'll opt for making more information available. > This returns us to the original question. Other than the implausible > scenario of a system that is managed well enough to maintain the chain > of > signature headers, but that makes no attempt to keep spam out of its > lists, in what scenario would this be of practical use in managing Z's > mail? If Z trusts Y, why wouldn't it be sending reports about Y's > lists > to Y? The question I was discussing wasn't about where to send abuse reports, it was about whether or not to believe what was claimed by the authentication data Y sent to Z. If Y says it saw a signature from X that validated, should Z believe that claim or not? > People have been saying since the dawn of DKIM that they want to see > the > incoming signatures on list mail, but I have yet to hear a plausible > story > about what to do with them. As far as I can tell, it's just an > unexamined > assumption that more signatures must be better, or that they as the > original signer will then somehow be able to tell recipients what to > do. I think you nailed it: It's an unexamined assumption. But so, to me at least, is the assertion that an author signature to a list is a bad idea for senders and will only serve to confuse verifiers. I'd like to see some data collected from such systems before I'm willing to agree or disagree with either perspective. And until then, I don't want to exclude anything. A favourite example of mine: A DKIM signature with an "l=" passes the DKIM module, but the verifier makes use of hooks into the module that allow it to discover the message quadrupled in size after signing. As a result, it quarantines the message, as required by local policy. That's more information than RFC4871 requires the DKIM module to provide, but it served a useful purpose. Another: A DKIM signature arrived and validated, but failed to cover the Subject: header field. The receiver discovers this and disallows the message (or filters it differently) due to local policy that's concerned with a change to what would appear in an inbox summary. Again, it's more information than is required, but it's useful. _______________________________________________ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html