[Bug 53922] pam_ldap and gdm have issues

[wouter]

Public bug reported:

Binary package hint: gdm

A client of mine has a network with a Debian Sarge server and a few
Ubuntu Dapper clients. The Sarge server runs slapd, and I've set up the
clients to use pam_ldap.so and libnss-ldap.so to keep usernames
centrally located. Also, /home is now NFS-mounted on the server. The
pam_ldap stuff is configured through the common-* files in /etc/pam.d

When I log in on a getty, everything works; no sweat. So my PAM
configuration seems to be okay.

When I log in through GDM, it accepts my username and password, but then
just sits there, doing totally nothing. The password entry is greyed
out, but instead of having gdmgreeter disappear and having the gnome
session start, nothing happens.

I've tried enabling the debug option through gdm.conf, but then the bug
disappears -- at least for the time being.

When I log in, 'ps aux --forest' shows me that _after entering username
and password_, the initial gdm has three child processes: another gdm
(forked off for handling the X server, probably), which has the X server
and the gdmgreeter processes as children.

Running strace on that second gdm shows:
select(1024, [3], [], NULL, NULL
which never exits. File handle 3 is a socket; if I start strace before entering the username and the password, I see that the last syscall is a write() to that same file handle; by the looks of it, this would be the socket that communicates with the LDAP server. I believe (by looking at what is going over the wire with a sniffer) that it has already received an answer at this point, but I am not 100% sure.

To me, this looks like a race condition in one of pam_ldap.so, libnss-
ldap.so, or gdm. Since it only occurs with gdm, however, I'm filing this
against gdm.

I'm willing to provide the sniff and perhaps some more detailed strace
information, but not through a public web interface -- some of these
files contain some sensitive passwords in cleartext...

** Affects: gdm (Ubuntu)
     Importance: Untriaged
         Status: Unconfirmed

-- 
pam_ldap and gdm have issues
https://launchpad.net/bugs/53922