RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

This bug is created as a clone of upstream ticket:
https://fedorahosted.org/sssd/ticket/1814

Currently, entering an empty kerberos password at the XDM login prompt creates a "critical error" message. 


It turns out that in the case of an empty password, Kerberos returns an LIBOS_CANTREADPWD to SSSD, which then returns PAM_CRED_UNAVAIL thru commit 383fa7e69136ce27031d7d0b9b9b8e5b0392bfee.

But actually it looks like Kerberos does not support empty passwords at all!

Hence, commit 383fa7e69136ce27031d7d0b9b9b8e5b0392bfee is correct in the sense that a Kerberos LIBOS_CANTREADPWD error should result in PAM_CRED_UNAVAIL.

**BUT** as Kerberos does even not support empty passwords, it returns LIBOS_CANTREADPWD somewhat wrongly here, interpreting the empty password as a failure to read a non-empty one (hence CANTREADPWD).


It should be SSSDs job to immediately return PAM_AUTH_ERR on an empty kerberos password, without actually forwarding the empty password to Kerberos (which would result in PAM_CRED_UNAVAIL).

I was not able to dig up Kerberos documentation that explicitly states that empty passwords are not allowed. Still, a google search reveals that this seems to be a commonly communicated fact".

Temporarily moving bugs to MODIFIED to work around errata tool bug

Verified the bug on SSSD Version: sssd-1.11.2-10.el7.x86_64

Steps followed during verification:
1. Login to GDM session with a kerberos user and "Empty password"
2. Monitor the /var/log/secure file for "System Error"

As expected, i couldn't find system error in the log file. The log file details during login is given below:

Dec 11 17:57:37 rhel-7 gdm-password]: pam_unix(gdm-password:auth): authentication failure; logname=(unknown) uid=0 euid=0 tty=:0 ruser= rhost=  user=tr_user

Dec 11 17:57:38 rhel-7 gdm-password]: pam_sss(gdm-password:auth): authentication failure; logname=(unknown) uid=0 euid=0 tty=:0 ruser= rhost= user=tr_user

Dec 11 17:57:38 rhel-7 gdm-password]: pam_sss(gdm-password:auth): received for user tr_user: 7 (Authentication failure)

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.