[Dovecot] Deliver EX_TEMPFAIL's without giving any information

[Denis Khromov]

Hi all.

 I've  had  a  hard  time trying to find out why deliver isn't working
 after  I've  updated  dovecot  from  v1.11 to v1.2.8. It just gave me
 EX_TEMPFAIL without any info in the logs. My deliver was setuid-root.

 Once  I've  made a simple shell wrapper script for the deliver
 executable which saves deliver's stdout+stderr, I've found the reason:

 /usr/local/libexec/dovecot/deliver must not be both world-executable
 and setuid-root. This allows root exploits. See
 http://wiki.dovecot.org/LDA#multipleuids

 Did a 'chmod o-x deliver' and fixed groups/owners and now everything
 works as it should.

 I think this error message should go to log files, not just to
 stdout/stderr. And it's worth to describe this behaviour in the Wiki.

Cheers,
Denis