[Dovecot] Configuration of LMTP Reject Code

[Petter Urkedal]

On 2011-02-22, Timo Sirainen wrote:
> On Tue, 2011-02-22 at 11:02 +0100, Petter Urkedal wrote:
> >     userdb {
> >       driver = passwd
> >       args = home=/srv/mail/nbi.ku.dk/%1n/%n mail=maildir:~/Maildir
> >     }
> 
> The problem with passwd is that it can't separate "user doesn't exist"
> from "temporary error". http://wiki2.dovecot.org/UserDatabase/NSS can
> separate these, but it hasn't been tested much..

I can see the issue with getpwnam is described in its Linux man-page:

    The formulation given above under "RETURN VALUE" is from POSIX.1-2001.
    It does not call "not found" an error, and hence does not specify what
    value  errno might have in this situation.  But that makes it impossi-
    ble to recognize errors.  One might  argue  that  according  to  POSIX
    errno  should be left unchanged if an entry is not found.  Experiments
    on various Unix-like systems show that lots of different values  occur
    in  this  situation:  0,  ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and
    probably others.

Since this is an issue with getpwnam (even the POSIX standard,
apparently), maybe the assumption about why getpwnam fails can be passed
directly to the userdb module?  I can see that
userdb_static_template_build accepts arbitrary key=value pairs, so how
about something like

    userdb {
      driver = passwd
      args = ... tempfail=1
    }

Anyway, thanks for the suggestion about NSS.  We may also use LDAP
directly, though that means we bypass the nslcd (nscd) cache, which is a
bit unfortunate.  So I think we can manage, but you have my vote for
adding a workaround for the getpwnam issue.