dovecot - Jan 2015 - LDA input validation

St?phane Cottin writes:
> A typical .qmail file :
>
> | /usr/bin/dspam --client --deliver=stdout --user "$EXT@$USER" |
/usr/bin/preline -f /usr/lib/dovecot/dovecot-lda -d "$EXT@$USER" -a
"$EXT@$USER" -m "$EXT2"
>
> When dspam segfault or is killed, preline receive an empty content and
> only pass to dovecot-lda two headers ( Return-Path and Delivered-To ).
> Then dovecot-lda delivers successfully and the original message
> contents are lost.
Steffen Kaiser rightly points out:
> That's the problem of the used Unix pipe and broken by design. The
right
> member of the pipe (preline) runs independendly of dspam and recieves no
> content via pipe. Why should preline or dovecot-lda believe there is an
> error? [... and suggests a wrapper script that aborts delivery on empty
> dspam output.]
I'm not sure if it's appropriate under your circumstances, but you can
also
pass stderr to stdout as well, and the recipient will get some diagnostic
message, which may or may not be helpful.

 	| /usr/bin/dspam --client --deliver=stdout --user "$EXT@$USER"
2>&1 | ...

Joseph Tam <jtam.home at gmail.com>

> Le 23 janv. 2015 ? 23:52, Joseph Tam <jtam.home at gmail.com> a ?crit
:
> 
> St?phane Cottin writes:
> 
>> A typical .qmail file :
>> 
>> | /usr/bin/dspam --client --deliver=stdout --user
"$EXT@$USER" | /usr/bin/preline -f /usr/lib/dovecot/dovecot-lda -d
"$EXT@$USER" -a "$EXT@$USER" -m "$EXT2"
>> 
>> When dspam segfault or is killed, preline receive an empty content and
>> only pass to dovecot-lda two headers ( Return-Path and Delivered-To ).
>> Then dovecot-lda delivers successfully and the original message
>> contents are lost.
> 
> Steffen Kaiser rightly points out:
> 
>> That's the problem of the used Unix pipe and broken by design. The
right
>> member of the pipe (preline) runs independendly of dspam and recieves
no
>> content via pipe. Why should preline or dovecot-lda believe there is an
>> error? [... and suggests a wrapper script that aborts delivery on empty
>> dspam output.]
> 
> I'm not sure if it's appropriate under your circumstances, but you
can also
> pass stderr to stdout as well, and the recipient will get some diagnostic
> message, which may or may not be helpful.
> 
> 	| /usr/bin/dspam --client --deliver=stdout --user "$EXT@$USER"
2>&1 | ...
> 
> Joseph Tam <jtam.home at gmail.com>
dspam already send errors to syslog, the point here is to never loose email
contents.
This was a wrong design, i'm now use a wrapper instead ( see my previous
post for details ).

St?phane