Authentication stopped working

[Chris White]

I have a dozen RedHat machines that were set up to use kerberos for
authentication aganst a M$ Active Directory server (managed by a central
admin department), they get their User account details from a LDAP database
that I manage (usernames are kept the same). All this was configured using
the authconfig tool with RedHat. It was all working.

I updated the system and now it fails to work. All I get, from a remote
login, is "Connection closed by XXX.XXX.XXX.XXX" instead of being prompted
for a password. This occures for ALL user accounts, even those that are
handled by the standard unix passwd file authentication (including root).

If I disable Kerberos authentication (but leave LDAP user accounts) in
authconfig then I can login using any account in the passwd fie (ie root),
but as soon as I re-activate the kerberos authentication it fails.

I have tried re-installing one machine with redhat 8.0 and it works fine
until I apply all the updates then the same problem occurs. I have tried
installing RedHat 9 and have exactly the same problem.

The Log files are not giving me much help, but it seams that the
authentication is progressing only to the pam_unix module and no further,

Sep 16 13:17:18 giants sshd(pam_unix)[7522]: check pass; user unknown
Sep 16 13:17:18 giants sshd(pam_unix)[7522]: authentication failure;
logname= uid=0 euid=0 tty=NODEVssh ruser= rhost=<My Host Name>

Any help would be most appreciated.

Thanks