Synopsis:    Low: vixie-cron security, bug fix, and enhancement update
Issue Date:  2012-02-21
CVE Numbers: CVE-2010-0424


The vixie-cron package contains the Vixie version of cron. Cron is a
standard UNIX daemon that runs specified programs at scheduled times. The
vixie-cron package adds improved security and more powerful configuration
options to the standard version of cron.

A race condition was found in the way the crontab program performed file
time stamp updates on a temporary file created when editing a user crontab
file. A local attacker could use this flaw to change the modification time
of arbitrary system files via a symbolic link attack. (CVE-2010-0424)

This update also fixes the following bugs:

* Cron jobs of users with home directories mounted on a Lightweight
Directory Access Protocol (LDAP) server or Network File System (NFS) were
often refused because jobs were marked as orphaned (typically due to a
temporary NSS lookup failure, when NIS and LDAP servers were unreachable).
With this update, a database of orphans is created, and cron jobs are
performed as expected. 

* Previously, cron did not log any errors if a cron job file located in the
/etc/cron.d/ directory contained invalid entries. An upstream patch has
been applied to address this problem and invalid entries in the cron job
files now produce warning messages. 

* Previously, the "@reboot" crontab macro incorrectly ran jobs when the
crond daemon was restarted. If the user used the macro on multiple
machines, all entries with the "@reboot" option were executed every time
the crond daemon was restarted. With this update, jobs are executed only
when the machine is rebooted. 

* The crontab utility is now compiled as a position-independent executable
(PIE), which enhances the security of the system. 

* When the parent crond daemon was stopped, but a child crond daemon was
running (executing a program), the "service crond status" command
incorrectly reported that crond was running. The source code has been
modified, and the "service crond status" command now correctly reports that
crond is stopped. 

* According to the pam(8) manual page, the cron daemon, crond, supports
access control with PAM (Pluggable Authentication Module). However, the PAM
configuration file for crond did not export environment variables correctly
and, consequently, setting PAM variables via cron did not work. This update
includes a corrected /etc/pam.d/crond file that exports environment
variables correctly. Setting pam variables via cron now works as documented
in the pam(8) manual page. 

* Previously, the mcstransd daemon modified labels for the crond daemon.
When the crond daemon attempted to use the modified label and mcstransd was
not running, crond used an incorrect label. Consequently, Security-Enhanced
Linux (SELinux) denials filled up the cron log, no jobs were executed, and
crond had to be restarted. With this update, both mcstransd and crond use
raw SELinux labels, which prevents the problem. 

* Previously, the crontab(1) and cron(8) manual pages contained multiple
typographical errors. This update fixes those errors. 

In addition, this update adds the following enhancement:

* Previously, the crontab utility did not use the Pluggable Authentication
Module (PAM) for verification of users. As a consequence, a user could
access crontab even if access had been restricted (usually by being denied
in the access.conf file). With this update, crontab returns an error
message that the user is not allowed to access crontab because of PAM
configuration. 

All vixie-cron users should upgrade to this updated package, which resolves
these issues and adds this enhancement.

SL5:
  i386
     vixie-cron-4.1-81.el5.i386.rpm
     vixie-cron-debuginfo-4.1-81.el5.i386.rpm
  x86_64
     vixie-cron-4.1-81.el5.x86_64.rpm
     vixie-cron-debuginfo-4.1-81.el5.x86_64.rpm

- Scientific Linux Development Team