LightDM + LDAP accounts hang if username is preceded with whitespace

[Harald Hannelius]

This might affect PAM and/or nslcd instead, but lightdm should be able to cope with it.

We have our users in an OpenLDAP directory, and I have disabled the user list from lightdm. Some people seem to have the habit of waking the monitor by pressing the spacebar, thus entering their username with a preceding whitespace.

I have a line like this in syslog;

nslcd[2624]: [ac3ac4] username changed from " haneliuh" to "haneliuh"

The expected behaviour would be to just reject the login attempt and return back to the login windows. Instead, lightdm now just hangs. If one changes to a text console and back the lightdm login windows remains all light grey.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: lightdm 1.0.6-0ubuntu1.2
ProcVersionSignature: Ubuntu 3.0.0-14.23-generic 3.0.9
Uname: Linux 3.0.0-14-generic x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Thu Jan 12 12:45:45 2012
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.lightdm.users.conf: 2011-11-07T15:42:48
mtime.conffile..etc.pam.d.lightdm: 2011-11-29T14:16:59.873130

[Harald Hannelius (harald-arcada)]

A freshly installed xubuntu 11.10 with updates authenticating only locally doesn't experience this behaviour. This leads me to believe that the real culprit in the drama is nslcd.

[Robert Ancell (robert-ancell)]

I've reassigned this to unity greeter. It seems reasonable for it to assume usernames don't start with whitespace so they can be trimmed. You can also find more information about authentication in /var/log/lightdm/lightdm.log.

[Robert Ancell (robert-ancell)]

I also suspect any blocking is done inside PAM so it's probably not lightdm/unity-greeters fault for the unresponsiveness, but checking the log will tell more.