Comment 3 for bug 26175

I get this too. Adding the deug option to the pam_unix.so module shows some
more information:

Dec 22 15:51:56 localhost unix_chkpwd[14298]: check pass; user unknown
Dec 22 15:51:56 localhost kcheckpass: (pam_unix) authentication failure;
logname= uid=1000 euid=1000 tty=/dev/pts/4 ruser= rhost= user=matthew
Dec 22 15:51:56 localhost kcheckpass[14297]: Authentication failure for matthew
(invoked by uid 1000)

The first line being the interesting one there I think. user unknown? I don't
know enough a PAM to have able to say what to do about it though. The setuid
root thing works, but I am un-easy about it.