[ietf-dkim] list vs contributor signatures, was Wrong Discussion
bmcdowell at paypal.com
Fri Apr 30 07:38:50 PDT 2010
On Apr 30, 2010, at 10:23 AM, Michael Thomas wrote:
> On 04/30/2010 07:05 AM, McDowell, Brett wrote:
>> In that scenario, if the MLM re-signing solution has been deployed by Y, and DKIM+ADSP has been deployed by X& Z, and Z has chosen to take action on X's ADSP policies... the only thing Z is trusting Y to do is validate incoming DKIM signatures, re-sign the messages with its own DKIM signature, and pass it along with the A-R results that convey what was done. Z is not trusting everything and anything that might ever come through Y.
>> I think that's a reasonable level of trust to expect mailbox providers to have in mail lists who assert that they do this. Rogue mail lists will stop being trusted but only after they have "lost" the trust that was granted to them via their standards-based assertion (we would probably need to spec out how a MLM advertises that they indeed conduct flows in this manner) that they perform these functions on incoming mail.
>> Again, I'm not saying this is the best or most elegant way of handling the problem of properly authenticated mail not being able to traverse mail lists, but it seems worthy of further discussion as an option.
> Yeahbut... there are zillions of mailing lists out there. How do you know the good ones
> from the bad ones? Keep in mind, of course, that bad guys can resign too, and they can
> easily make themselves look like a mailing list if that's something that gives them
Indeed. But mailbox providers all have their own secret sauce for figuring out reputation of senders that I believe they could apply to this new flavor of sender -- meaning MLM's who adopt the MLM-DKIM spec we seem to be debating the virtues of developing -- without too much overhead.
> If the solution is some sort of (third party) reputation/whitelist, then there's really
> not much for us to do, right?
I think we still need this spec I'm starting to refer to as MLM-DKIM to specify both the proper way of conducting this re-signing & reporting practice and how the MLM advertises that they follow it.
> Even with your discardable adsp setting, it becomes a
> matter of the order of checks at the receiver's gate (eg, whitelist first, then adsp...)
But since mailbox providers already manage reputation at scale, how much of a burden is adding this bit to the mix? Remember this only affects mailbox providers who have decided to do DKIM blocking based on ADSP discardable policies (for some, if not all senders).
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