[Mailman-Developers] ARC user options

2022-09-04 Thread Stephen J. Turnbull
Alessandro Vesely writes:

 > There is a thread about ARC sealing in bind-users[*].

Not sure what you mean by "sealing".  Do you mean they're not
implementing the rest of the protocol?

 > They're applying ARC signatures, although they run Mailman 2.
 > It doesn't seem difficult to implement.

It's not.  But

1.  It's a bad idea to do it in Mailman.
2.  It was implemented in Mailman 3 three or four years ago as a proof
of concept during the development of ARC.
3.  There is a milter available for Postfix and Sendmail from the
Trusted Domain Project https://github.com/trusteddomainproject/OpenARC
as is the basic implementation which I presume is adaptable to
Exim, qmail, and other MTAs.

This is the preferred approach, as matter of conformance because
it should be implemented by the edge MTA(s), and as a practical
matter because Mailman *can't* do SPF since it is never an edge
MTA.  There is also a pure Python implementation on PyPI, I
believe (this is the basis for the Mailman 3 plugin, or maybe it
was dkimpy).

 > It requires trusting the users, though.

I don't think so, not any more than any other sign-and-send protocol.
What it requires is implementation by recipient domains who trust your
host, because if they don't it's 2014 all over again for your
subscribers if you have any DMARC p=reject posters.

 > Would Mailman implement something like it?

Yes for Mailman 3, it's already done (but you are recommended to
configure it in the MTA).  No for Mailman 2, it's EOL.

Steve

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[Mailman-Developers] ARC user options

2022-09-04 Thread Alessandro Vesely

Hi,

There is a thread about ARC sealing in bind-users[*].  They're applying ARC 
signatures, although they run Mailman 2.  The last message hypothesizes a user 
option like so:


   *From munging*:

   Set this option to /Disabled/ to receive messages with the original From:
   line intact.  Keep in mind that disabling this option will fail DMARC, so
   keep it enabled unless your MTA either doesn't check DMARC or accepts ARC
   overrides.

It doesn't seem difficult to implement.  It requires trusting the users, 
though.  Would Mailman implement something like it?  Why?  Why not?



Best
Ale
--

[*] https://lists.isc.org/pipermail/bind-users/2022-September/106612.html



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