5 - RHSA-2010:0258

Problem Description:

Updated pam_krb5 packages that fix one security issue and various bugs are now available for Red Hat Enterprise Linux 5.

The Red Hat Security Response Team has rated this update as having low security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux (v. 5 server) - i386, ia64, ppc, s390x, x86_64 Red Hat Enterprise Linux Desktop (v. 5 client) - i386, x86_64

3. Description:

The pam_krb5 module allows Pluggable Authentication Modules (PAM) aware applications to use Kerberos to verify user identities by obtaining user credentials at log in time.

A flaw was found in pam_krb5. In some non-default configurations (specifically, those where pam_krb5 would be the first module to prompt for a password), the text of the password prompt varied based on whether or not the username provided was a username known to the system. A remote attacker could use this flaw to recognize valid usernames, which would aid a dictionary-based password guess attack. (CVE-2009-1384)

This update also fixes the following bugs:

* certain applications which do not properly implement PAM conversations may fail to authenticate users whose passwords have expired and must be changed, or may succeed without forcing the user's password to be changed. This bug is triggered by a previously-applied fix to pam_krb5 which makes it comply more closely to PAM specifications. If an application misbehaves, enabling the "chpw_prompt" option for its service should restore the old behavior. (BZ#509092)

* pam_krb5 does not allow the user to change an expired password in cases where the Key Distribution Center (KDC) is configured to refuse attempts to obtain forwardable password-changing credentials. This update fixes this issue. (BZ#489015)

* failure to verify TGT because of wrong keytab handling. (BZ#450776)

Users of pam_krb5 are advised to upgrade to these updated packages, which resolve these issues.

4. Solution:

Before applying this update, make sure all previously-released errata relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the Red Hat Network to apply this update are available at http://kbase.redhat.com/faq/docs/DOC-11259

5. Bugs fixed (http://bugzilla.redhat.com/):

450776 - Failed to verify TGT cause of wrong keytab handling 489015 - pam_krb5 cannot offer to change expired password 502602 - CVE-2009-1384 pam_krb5: Password prompt varies for existent and non-existent users 505265 - CVE-2009-1384 RHEL-5's pam_krb5: Password prompt varies for existent and non-existent users 509092 - pam_krb5 update breaks graphical apps (gnome and kde)