On Mon, Mar 2, 2020 at 4:45 PM Stephen J. Turnbull <turnbull.stephen.fw@u.tsukuba.ac.jp> wrote:
Doesn't Postfix do ARC yet? :-( rspamd seems to be recommended by a couple of Linux distros, supports the milter interface that Postfix uses to call out to 3rd party processes, and the website looks good. See rspamd.com. That said, if you want to use Mailman's support...
To me, it seems easier to use Mailman's implementation if it is possible. Rspamd seems very nice as an alternative if I find time to substitute my spamassassin, greylister and, I guess, opendkim setup. As the feature of rspamd set is large with a web UI it probably is as time consuming to set up as mailman, so I'd rather not if I can avoid it. When I migrate to another server in due time it seems interesting.
Our support doesn't have issues that I know of. You can check the issue tracker: https://gitlab.com/mailman/mailman/issues. On second thought, don't bother. I did and "ARC" picks up scads of irrelevant junk, "authenticated received chain" nothing, and a couple of other tries don't pick up anything useful either.
I run the latest release of mailman (3.3.0 of core) on Python 3.7.6 and I use postfix as MTA.
I haven't looked at ARC in some months, so it's possible that our current implementation is out of date with best current practice. However, in a quick scan I see no difference in RFC 8617 vs. ID-ARC-23, so I don't know what might have changed there.
Are the messages being refused by those sites because of the ARC errors, or are they being delivered anyway? We probably need to see the message as received by Mailman, the message as emitted by Mailman, and the message as received at the validating site to have a hope of diagnosing this.
So far, they are delivered. Probably for the same reason that my messages are accepted without ARC. IPs with good reputation and a generally well-behaved setup.
The things that I can see from the data you've provided that might be related are
- If it's just the body hash that's a problem, there may be one or more MXes that convert Content-Transfer-Encoding between your Mailman and the receiving sites. That would be easy to check if you have the messages as sent and as received.
I do not think they do, but I'll examine that. My DKIM signing works just fine but postfix might have changed something before opendkim get the message. I'll have to find a way to capture the sent message leaving mailman before it enters postfix.
You have an awfully aggressive list of signed header fields. In particular, the Resent-* fields are treated as trace fields: there may be multiple instances of each. I don't understand the semantics of DKIM/ARC signing for those headers very well, but it's something that I would think easy to mess up. You might try deleting those.
You are supposed to sign any existing DKIM-Signature fields, but that's not in the list.
I just used the default list of fields from the Mailman documentation. Now I did try a shorter list of fields but that did not help.
- The ARC RFC 8617 says that an ARC Sealer must add any DKIM-Signature *before* ARC sealing. I suppose this could be a problem, since our ARC implementation doesn't DKIM sign. (On the other hand, I don't see how it would be a problem, since any MX along the way might add a DKIM signature, and you're not signing DKIM-Signature according to your list of signed fields.)
It would be a problem if I'd add the DKIM fields to the field list of course. I see another potential problem with that list in that it includes fields that are not present, I had understood it as that would fail if a field is missing.
It would be helpful if instead of quoting small parts of error messages, you gave us the entire body of a delivery status notification message or the entire MTA log. If there's stuff (domains, mailboxes, IP addresses) you want to redact, feel free, just make sure that it's obvious what was redacted.
I can do that. For that I will have to re-run my test which I do not have time for today, alas. It is easier to me to send an entire delivered message (with some domains and IPs redacted). I'll add such an example at the bottom of this mail as it gets a bit unwieldy.
I will check our implementation, principally to make sure that the authentication results used are computed on the raw incoming message and the ARC sealing is done on the raw outgoing message after all other message modifications are done. I will also see if I can conjure up tests that test the site's MTA(s) as well as just our implementation, as we currently test our implementation using static data from the ARC implementation we use (ie, we ARC-process a given message and then do a byte-by-byte comparison on an allegedly correct ARC-Sealed version of the same).
Is there any good tool to verify an ARC signature? I could of course set another list as a subscriber to feed the result back to OpenDKIM and Mailman-ARC to see what happens but that is a bit convoluted.
Sorry I can't give more precise help. Maybe something here will be of use.
Of much use as it got me thinking, if nothing else.
// David
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b=aUkUFDX3gmRAu4yffKt1a93D0zQ5SHOVM9IBgn9Eds02d99fTpDPGPrLURXm5nMsm 5Czjhyv12hwt/sDcqjkgot7XNZgpYu+ygeNhfFr/fNDR3I+/OJhQJFl7pGFH6/LkpI eZqCZuGFTTZjLU5/kPZ3Bxul9NsWUpFoxkoDj8bumbVnkAqBpFNqKF7vojUs/0A8lU MNZRRpvFzdpJPrMOWq2ZW/SfLZJaXJEKQPBX+cxtLTadwRooG4tJ58hGbjuk5qIlHH 0rohDoyI6zFO1IZLUub+LltmX8Z9CjGyfOp7FJeXs4i/F2Y0NtZfdATjGr9ODWYsxl Do7WWaCt/IagQ== ARC-Seal: i=1; cv=none; a=rsa-sha256; d=example1.com; s=dkim; t=1582993642; b=gcSal3MqawEf89KBCDi3s7mNkPZfJhN7XJ0SRlaB6fTT1LSVbEDb6JXa0cM4owpyvPPWU VG6/bOqHJeuACWqGQ6/wnXJCuRCJJkKzv0FVJCg61xfXcSUtKKCeLFarZtx59WUGxkkmCqI oDJufbsX56AYM0awVkHn9xu+eezG87Q= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=example1.com; s=dkim; t=1582993642; h=from : sender : reply-to : subject : date : message-id : to : cc : mime-version : content-type : content-transfer-encoding : content-id : content-description : resent-date : resent-from : resent-sender : resent-to : resent-cc : resent-message-id : in-reply-to : references : list-id : list-help : list-unsubscribe : list-subscribe : list-post : list-owner : list-archive; 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