Re: .forward MDA fails, "mail.local: may only be run by the superuser"

On Sat, Feb 01, 2020 at 09:29:16AM +0000, gilles@poolp.org wrote:
> February 1, 2020 9:11 AM, "Andreas Kusalananda Kähäri" <andreas.kahari@abc.se> wrote:
>
> > Hi,
> >
> > With the latest snapshot on amd64 (6.6 GENERIC.MP#627), using a "|"-line
> > in one's ~/.forward makes delivery of mail fail with
> >
> > Feb 1 08:53:53 pooh smtpd[72575]: d9abac6b3d904e13 smtp connected address=local
> > host=pooh.prefix.duckdns.org
> > Feb 1 08:53:54 pooh smtpd[72575]: d9abac6b3d904e13 smtp message msgid=8698cb82 size=1824 nrcpt=1
> > proto=ESMTP
> > Feb 1 08:53:54 pooh smtpd[72575]: d9abac6b3d904e13 smtp envelope evpid=8698cb8264606654 from=<>
> > to=<kk@pooh.prefix.duckdns.org>
> > Feb 1 08:53:54 pooh smtpd[72575]: d9abac6b3d904e13 smtp disconnected reason=quit
> > Feb 1 08:53:54 pooh mail.local: may only be run by the superuser
> > Feb 1 08:53:54 pooh smtpd[72575]: d9abac6d77a45212 mda delivery evpid=8698cb8264606654 from=<>
> > to=<kk@pooh.prefix.duckdns.org> rcpt=<kk@pooh.prefix.duckdns.org> user=kk delay=0s result=PermFail
> > stat=Error ("mail.local: may only be run by the superuser")
> > Feb 1 08:53:54 pooh smtpd[19621]: warn: queue: no return path!
> >
> > The mail is then lost.
> >
>
> It is rejected at session time because there's no other way to handle
> this case:
>
> your user "kk" tries to execute "mail.local" from ~/.forward file but
> mail.local requires privileges and smtpd doesn't allow running things
> with privileges from ~/.forward.
>
> it can't be handled as a temporary failure either.
>
>
> > I have
> >
> > pooh % cat .forward
> > |/usr/local/bin/fdm -a stdin fetch
> >
> > where "stdin" is a simple mail "account" in fdm(1) that takes messages
> > from standard input, filters it, and sorts it into the correct Maildir
> > inbox. For me, this only affects messages originating from the local
> > system (e.g. crontab output etc., but also messages for root as my root
> > user is aliased to my ordinary user through /etc/mail/aliases).
> >
>
> I'm not sure that's what's happening, maildir can't possibly use mail.local,
> and the error message is explicit, mail.local is being executed somehow.
>
>
> > I understand that this may well be by design rather than a bug. How
> > may one use a personal MDA from ~/.forward nowadays, or is that option
> > completely unsupported from now on?
> >
>
> That shouldn't be the case as I use ~/.forward with fdm in it

Are you using the latest snapshot? This started happening after
updating today, between the snapshots that advertise MP kernel build
number #626 and #627 on amd64.

>
> It would help if you shared your config

The _only_ thing related to the "stdin" account in my ~/.fdm.conf is a
single line saying

account "stdin" disabled stdin

Mail is otherwise filtered and sorted _exactly_ like the messages that I
fetch from remote IMAPS accounts in the same configuration.

The smtpd configuration for local-to-local delivery looks like

action "local" mbox alias <aliases>
match from local for local action "local"

I did not send this to the bugs list because I wasn't sure it was a base
system bug, a bug in fdm, or the intended behaviour after the various
recent updates to smtpd, or just something that I'm doing wrong. If it
is indeed a bug, then I'll write a proper report to the bugs list.

Regards,

--
Andreas (Kusalananda) Kähäri
SciLifeLab, NBIS, ICM
Uppsala University, Sweden

.