From header mangling for some debbugs mail to yhetil.org

From header mangling for some debbugs mail to yhetil.org

[Liam Hupfer]

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Hi Kyle,

Thank you for hosting yhetil.org! public-inbox is genius and piem is a
great interface. Fortunately for me, we seem to have similar tastes in
software, so I benefit from most of the lists you mirror.

I noticed some messages involving debbugs end up with “via <list name>”
in the From header, but not others. As far as I can tell, these
rewritten From headers don’t show up in the archives at lists.gnu.org or
debbugs.gnu.org.

It seems to mostly correlate with senders, but not always, e.g. [-f:via
f:geerinckx] with and without the leading `-' both show results, although
there seems to be a shift towards “via” around 2019 in the case of this
sender, with some overlap.

Do you know what’s going on here? Thanks,

—Liam


[-f:via
f:geerinckx] <https://yhetil.org/guix-bugs/?q=-f%3Avia+f%3Ageerinckx>

Re: From header mangling for some debbugs mail to yhetil.org

[Kyle Meyer]

Liam Hupfer writes:

> Hi Kyle,
>
> Thank you for hosting yhetil.org! public-inbox is genius and piem is a
> great interface. Fortunately for me, we seem to have similar tastes in
> software, so I benefit from most of the lists you mirror.

You're welcome.  I'm glad to hear you find yhetil.org useful.

> I noticed some messages involving debbugs end up with “via <list name>”
> in the From header, but not others.

My understanding is that this From rewriting is due to how the admins
have configured Mailman.

  https://docs.mailman3.org/projects/mailman/en/latest/src/mailman/handlers/docs/dmarc-mitigations.html

Here's a previous discussion related to this on guix-devel:

  https://yhetil.org/guix-devel/87pn2kyo2c.fsf@kyleam.com/T/#u

> As far as I can tell, these rewritten From headers don’t show up in
> the archives at lists.gnu.org or debbugs.gnu.org.

I don't know what the underlying setup is there, but my guess is that
those services get the messages before the rewrite.  yhetil.org receives
messages as any regular list subscriber would.

If you look through other archives (e.g.,
<https://www.mail-archive.com/bug-guix@gnu.org/>), you'll spot some
"via" senders.

> It seems to mostly correlate with senders, but not always, e.g. [-f:via
> f:geerinckx] with and without the leading `-' both show results, although
> there seems to be a shift towards “via” around 2019 in the case of this
> sender, with some overlap.
>
> Do you know what’s going on here?

Not with any confidence, but I suspect the sender is using a different
configuration/setup when sending the non-via messages than when sending
the via messages.  Here's some support of that:

  # with via
  $ curl -fSsL -d '' 'https://yhetil.org/guix-bugs/?q=f%3Avia+f%3Ageerinckx&x=m' | zcat | grep -c 'DKIM-Signature:'
  455

  # without via
  $ curl -fSsL -d '' 'https://yhetil.org/guix-bugs/?q=-f%3Avia+f%3Ageerinckx&x=m' | zcat | grep -c 'DKIM-Signature:'
  0

Re: From header mangling for some debbugs mail to yhetil.org

[Liam Hupfer]

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Hi Kyle, just getting back to this now.

Kyle Meyer <kyle@kyleam.com> writes:

> Liam Hupfer writes:

>> I noticed some messages involving debbugs end up with “via <list name>”
>> in the From header, but not others.
>
> My understanding is that this From rewriting is due to how the admins
> have configured Mailman.
>
>   <https://docs.mailman3.org/projects/mailman/en/latest/src/mailman/handlers/docs/dmarc-mitigations.html>
>
> Here’s a previous discussion related to this on guix-devel:
>
>   <https://yhetil.org/guix-devel/87pn2kyo2c.fsf@kyleam.com/T/#u>
>
>> As far as I can tell, these rewritten From headers don’t show up in
>> the archives at lists.gnu.org or debbugs.gnu.org.
>
> I don’t know what the underlying setup is there, but my guess is that
> those services get the messages before the rewrite.  yhetil.org receives
> messages as any regular list subscriber would.
>
> If you look through other archives (e.g.,
> <https://www.mail-archive.com/bug-guix@gnu.org/>), you’ll spot some
> “via” senders.

Yup, I see them on emacs-devel as well. I think you’re exactly right about all
of this (as well as the bit about different configurations (no DKIM)
likely causing the differing behavior given a particular sender).

I did some more digging and found that Konstantin Ryabitsev’s [Subspace
mailing list server announcement] discusses appeasing DMARC. He argues
that mailing lists shouldn’t have to munge the From header assuming they
set the envelope-from address to the list domain and don’t fiddle with
any DKIM-signed content. I’m inclined to take the kernel.org list
administrator at his word on the subject.

So I guess I would have to convince the Mailman 2 maintainers to expose
this DMARC mitigation policy (or lack thereof) as an option, and then
convince the GNU sysadmins to upgrade. No idea how feasible that is.

For now, I set `p=none' in my DMARC record. Not ideal, but I don’t think
I’m at much risk of impersonation anyway.

Thanks for pointing me in the right direction!

—Liam


[Subspace
mailing list server announcement] <https://people.kernel.org/monsieuricon/subspace-mailing-list-server>