Re: [exim] spool format error (on some list messages)

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Author: Heiko Schlittermann
Date:  
To: exim-users
Subject: Re: [exim] spool format error (on some list messages)
exim-users--- via Exim-users <exim-users@???> (Do 31 Mai 2018 21:52:51 CEST):
..
>
> >> 1fOL7J-0001BL-DC-H
> > …
> >> 031 X-Spam-Relay-Country: US US **
> >> 090 Subject: [tip:perf/urgent] perf tools: Fix perf.data format description of
> >> NRCPUS header
> >> 065 X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000)
> >> 066 X-SA-Exim-Scanned: Yes (on s-Mich Richter <tmricht@???>
> > [ HERE THE BLANK LINE WAS EATEN, so Exim doesn't recognize
> > this as the end of the header section of the message.
> >> 042 Acked-by: Andi Kleen <ak@???>
> >> 044 Cc: Adrian Hunter <adrian.hunter@???>
> >> 036 Cc: David Ahern <dsahern@???>
> >> 034 Cc: He Kuang <hekuang@???>
> >> 053 Cc: Hendrik Brueckner <brueckner@???>
> >> 038 Cc: Jin Yao <yao.jin@???>
> > …
>
> You are right, the X-SA-Exim-Scanned header is truncated (after "on", I
> missed that before) it is set by sa-exim (code snipplet from sa-exim.c
> with line numbers):


Ah, that *I* didn't see, that there's a fragment of the header to be
added. Hm. The 's-' is part of the primary hostname?

> --cut
>   31 /* Exim includes */
>   32 #include "local_scan.h"
>   33 extern FILE   *smtp_out;               /* Exim's incoming SMTP
> output file */
>   34 extern int     body_linecount;         /* Line count in body */
>   35 extern uschar *primary_hostname;
> ...
> 1277     header_add(' ', "X-SA-Exim-Scanned: Yes (on %s)\n",
> primary_hostname);
> --cut


Ok, the spool wire format is off, you said. I'm not sure about the
mechanigs of sa_exim, that is, I do not have any clue *which* file it
sees and modifies. And/or if we built some optimisations which assume
that the spooled files (spooled in $spooldir/scan) are not altered.

For better theories about what's going on we need to know which files
sa_exim accesses.

If this is important and worth to be solved,, it would need some further
investigation.

@Jeremy: Maybe we should announce that sa_exim will have
some end-of-life in the near future?

> All corrupted messages at least lack "primary-hostname" and the newline,
> some have other parts of the message in there. Any simple way to use a
> saved message to produce some more debugging information?


You can try to use something like

    swaks --data ./saved-message -f … -t … --pipe 'exim -bh 1.1.1.1'


I'm not sure, if exim stops processing right before or right after the
local_scan() call.

As you do not want to test the ACL, exim -N could be your friend.

> achieve the sa-exim functionality (on the fly spamassassin scanning and
> greylisting depending on spamassassin scores)? Spamassassin integration
> via exiscan and greylisting as described in
> https://github.com/Exim/exim/wiki/SimpleGreylisting or greylistd? Any
> best practice on this topic? What I liked on sa-exim is, that there is
> no initial greylisting for unknown senders/hosts when they send mails
> with reasonable low spamassasin scores.


I do greylisting based on the announced content size. But your approach
might be good too.

I wrote some Perl function(s) to support greylisting in Exim, these
functions work reliable for years already. Tell me, if you're
interested, I"d update the docs and the scripts a bit and publish it.

(To be true, it is published already, but the docs are outdated.)

    Best regards from Dresden/Germany
    Viele Grüße aus Dresden
    Heiko Schlittermann
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