[Mailman-Developers] Camera-ready option to mitigate DMARC issues
vesely at tana.it
Sun Nov 6 12:39:19 EST 2016
On Sat 05/Nov/2016 19:51:13 +0100 Mark Sapiro wrote:
> On 11/05/2016 04:11 AM, Alessandro Vesely wrote:
>> The idea is to add a footer only in case it is not present, similar to
>> what is done with subject_prefix. By properly setting both of them, a
>> sender can submit what can be called a camera-ready post. Since no
>> change applies, no DKIM signature breaks. Hence,
>> dmarc_moderation_action is not needed for such posts. It is not even
>> necessary to check author's domain policy.
> Mailman could conceivably keep track of whether it has changed any
> headers or anything in the body of the post, but it's more complicated
> than that. The first big problem is the Munge From or Wrap Message
> transformations are applied before any msg_header or msg_footer is added
> (or maybe added).
Is it possible to abort processing the in-memory msg and revert to the file?
Doing so --after thorough checks-- would prevent breaking the signature by
altering the order of recipient, switching MIME values from token to
quoted-string or vice-versa, and similar changes that memory representation may
> I.e. in both MM 2.1 and MM 3, the DMARC mitigations are applied in the
> incoming handler pipeline before the message is queued for delivery
All right, so we cannot save that lookup.
> Various decorations such as adding msg_header and msg_footer and modifying
> To: depend on "personalization" and have to be done by delivery processing
> on a per-recipient basis. In fact, the "camera ready" notion can't apply to
> any post that is going to be personalized in any way. This in itself would
> limit the usefulness.
Sure, personalization cannot be compatible with camera-ready.
> It would be more feasible to do this by the poster adding a
> "X-Camera-Ready:" header to the post saying don't transform my message,
> but this is unacceptable as it would bypass content filtering,
> personalization and various other things.
X-Camera-Ready: may be useful to automate at senders'. For an author doing it
by hands, having to set a header field is an added difficulty...
>> I'm not familiar with Mailman administration, so I ask your opinion.
>> How long would it take to code this option?
> How many angels can dance on the head of a pin?
Ah, not so many of them are still able to perform that, nowadays ;-)
>> Camera-ready posts would be created by hands, by cleverly configuring
>> some email client, or by using purposely written add-ons. They could
>> also be done by MSAs who care about the damage they cause by publishing
>> p=reject --the process can certainly be standardized and automated.
> How does the sender's automated process even know what msg_header and
> msg_footer will be added by the list?
MTAs can learn List-Post addresses when they receive mail. When they see one,
they can, say, change the envelope recipient to an internal mailbox which
processes the decoration (and maybe adds X-Camera-Ready:). The decorating
module could be carved out from Mailman, and complemented so as to let it
download its parameters from well known locations or some such.
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