Bug#478263: xdm: does not allow to log in when no password is set

["Trent W. Buck" <trentbuck@gmail.com>]

On Tue, Oct 21, 2008 at 04:38:35PM +1100, Trent W. Buck wrote:
>> When I try to log in as a user with no password set xdm asks for a
>> password and fails to verify it.
>
> I can reproduce this problem.

I can log in with no problem using login(8) on the tty, so I tried 

    cp --backup /etc/pam.d/{login,xdm}
    /etc/init.d/xdm

This didn't help.  Nor does anything useful turn up in /var/log, even
with "debug" on all pam_unix.so entries in /etc/pam.d/common-*.

    Oct 21 17:08:49 Clio xdm[12858]: pam_unix(xdm:auth): authentication failure; logname= uid=0 euid=0 tty=:0 ruser= rhost=  user=twb
    Oct 21 17:08:51 Clio xdm[12858]: LOGIN FAILURE ON :0, (null)
    Tue Oct 21 17:08:51 2008 xdm error (pid 12858): pam_authenticate failure: Authentication failure