Updated pam packages that fix two security flaws, resolve several bugs, and add enhancements are now available for CentOS Linux 5. This update has been rated as having moderate security impact by the Red Hat Security Response Team.
Pluggable Authentication Modules (PAM) provide a system whereby administrators can set up authentication policies without having to recompile programs that handle authentication. A flaw was found in the way pam_console set console device permissions. It was possible for various console devices to retain ownership of the console user after logging out, possibly leaking information to another local user. (CVE-2007-1716) A flaw was found in the way the PAM library wrote account names to the audit subsystem. An attacker could inject strings containing parts of audit messages which could possibly mislead or confuse audit log parsing tools. (CVE-2007-3102) As well, these updated packages fix the following bugs: * truncated MD5-hashed passwords in "/etc/shadow" were treated as valid, resulting in insecure and invalid passwords. * the pam_namespace module did not convert context names to raw format and did not unmount polyinstantiated directories in some cases. It also crashed when an unknown user name was used in "/etc/security/namespace.conf", the pam_namespace configuration file. * the pam_selinux module was not relabeling the controlling tty correctly, and in some cases it did not send complete information about user role and level change to the audit subsystem. These updated packages add the following enhancements: * pam_limits module now supports parsing additional config files placed into the /etc/security/limits.d/ directory. These files are read after the main configuration file. * the modules pam_limits, pam_access, and pam_time now send a message to the audit subsystem when a user is denied access based on the number of login sessions, origin of user, and time of login. * pam_unix module security properties were improved. Functionality in the setuid helper binary, unix_chkpwd, which was not required for user authentication, was moved to a new non-setuid helper binary, unix_update. All users of PAM should upgrade to these updated packages, which resolve these issues and add these enhancements.