3.7 - RHSA-2013:1319

Problem Description:

Updated sssd packages that fix one security issue and several 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:

SSSD (System Security Services Daemon) provides a set of daemons to manage access to remote directories and authentication mechanisms. It provides NSS (Name Service Switch) and PAM (Pluggable Authentication Modules) interfaces toward the system and a pluggable back end system to connect to multiple different account sources.

A race condition was found in the way SSSD copied and removed user home directories. A local attacker who is able to write into the home directory of a different user who is being removed could use this flaw to perform symbolic link attacks, possibly allowing them to modify and delete arbitrary files with the privileges of the root user. (CVE-2013-0219)

The CVE-2013-0219 issue war discovered by Florian Weimer of the Red Hat Product Security Team.

This update also fixes the following bugs:

* After a paging control was used, memory in the sssd_be process was never freed which led to the growth of the sssd_be process memory usage over time. To fix this bug, the paging control was deallocated after use, and thus the memory usage of the sssd_be process no longer grows. (BZ#820908)

* If the sssd_be process was terminated and recreated while there were authentication requests pending, the sssd_pam process did not recover correctly and did not reconnect to the new sssd_be process. Consequently, the sssd_pam process was seemingly blocked and did not accept any new authentication requests. The sssd_pam process has been fixes so that it reconnects to the new instance of the sssd_be process after the original one terminated unexpectedly. Even after a crash and reconnect, the sssd_pam process now accepts new authentication requests. (BZ#882414)

* When the sssd_be process hung for a while, it was terminated and a new instance was created. If the old instance did not respond to the TERM signal and continued running, SSSD terminated unexpectedly. As a consequence, the user could not log in. SSSD now keeps track of sssd_be subprocesses more effectively, making the restarts of sssd_be more reliable in such scenarios. Users can now log in whenever the sssd_be is restarted and becomes unresponsive. (BZ#886165)

* In case the processing of an LDAP request took longer than the client timeout upon completing the request (60 seconds by default), the PAM client could have accessed memory that was previously freed due to the client timeout being reached. As a result, the sssd_pam process terminated unexpectedly with a segmentation fault. SSSD now ignores an LDAP request result when it detects that the set timeout of this request has been reached. The sssd_pam process no longer crashes in the aforementioned scenario. (BZ#923813)

* When there was a heavy load of users and groups to be saved in cache, SSSD experienced a timeout. Consequently, NSS did not start the backup process properly and it was impossible to log in. A patch has been provided to fix this bug. The SSSD daemon now remains responsive and the login continues as expected. (BZ#805729)

* SSSD kept the file descriptors to the log files open. Consequently, on occasions like moving the actual log file and restarting the back end, SSSD still kept the file descriptors open. SSSD now closes the file descriptor after the child process execution; after a successful back end start, the file descriptor to log files is closed. (BZ#961680)

* While performing access control in the Identity Management back end, SSSD erroneously downloaded the "member" attribute from the server and then attempted to use it in the cache verbatim. Consequently, the cache attempted to use the "member" attribute values as if they were pointing to the local cache which was CPU intensive. The member attribute when processing host groups is no longer downloaded and processed. Moreover, the login process is reasonably fast even with large host groups. (BZ#979047)

All sssd users are advised to upgrade to these updated packages, which contain backported patches to correct 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 https://access.redhat.com/site/articles/11258

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

884254 - CVE-2013-0219 sssd: TOCTOU race conditions by copying and removing directory trees 961680 - sssd components seem to mishandle sighup 974036 - sssd core process keeps running after backends quit 979047 - sssd_be goes to 99% CPU and causes significant login delays when client is under load