[Dovecot] auth issues on centos5 with ldap backend

Timo Sirainen tss at iki.fi
Thu Jun 5 03:54:13 EEST 2008

On Wed, 2008-06-04 at 20:02 -0400, Jurvis LaSalle wrote:

> >> Jun  4 19:12:08 khan dovecot-auth: pam_unix(dovecot:auth):
> >> authentication failure; logname= uid=0 euid=0 tty=dovecot ruser=
> >> rhost=  user=user123
> >
> > Someone's trying to brute-force in?
> >
> sorry.  i changed that from a valid username at our site to
> user123.   
> nearly all of the errors are for valid accounts.

Are there any valid logins at all then?

> >> Users can usually login OK with their ldap credentials, but
> >> occasionally logins slow to a crawl if not outright fail, esp people
> >> checking mail through Squirrelmail.  Things get better after a  
> >> dovecot
> >> restart.
> >
> > You used blocking=yes with PAM, which means the PAM processes get
> > reused. This might be why restarting helps. Have you tried how it  
> > works
> > without the blocking=yes?
> >
> when we were still using the rh rpm, we were troubleshooting the  
> outlook offline issue and found this thread:
> http://www.mail-archive.com/dovecot@dovecot.org/msg04150.html
> It seemed pertinent to our situation and led us to install from source  
> and use blocking=yes.  I just commented it out.  I'm still getting an  
> error per login in /var/log/secure.  I'll see if it keeps things from  
> locking up during the thick of it tomorrow.

Having blocking=yes only for userdb passwd should be enough to fix the
nss_ldap problem.

> there's only one passdb now because I disabled the second to try to  
> get rid of the error.  I thought it would after reading this thread: http://www.mail-archive.com/dovecot@dovecot.org/msg03102.html
> since we're transitioning accounts using imapsync and don't know the  
> ldap passwords for all accounts, this is what the dovecot -n output  
> usually looks like:
>    passdb:
>      driver: passwd-file
>      args: /etc/dovecot.master
>      master: yes

passwd-file doesn't have any kind of conflicts with PAM (unlike

> > Anyway, one sure way to reduce PAM problems would be to get rid of it
> > and just configure Dovecot to use LDAP directly.
> That does appear to be the last avenue open.

The performance should also be a lot better than with PAM.
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