(RHSA-2004:304) pam security update

PAM (Pluggable Authentication Modules) is a system security tool that
allows system administrators to set an authentication policy without
having to recompile programs that handle authentication.

These updates fix a potential security problem present in the
pam_wheel module. These updates correct a bug in the pam_lastlog
module which prevented it from properly manipulating the /var/log/lastlog
entry for users with very high user IDs.

The pam_wheel module is used to restrict access to a particular service
based on group membership. If the pam_wheel module was used with the
“trust” option enabled, but without the “use_uid” option, any local
user would be able to spoof the username returned by getlogin(). The user
could therefore gain access to a superuser account without supplying a
password. In Red Hat Enterprise Linux 2.1, pam_wheel is not used by
default. The Common Vulnerabilities and Exposures project (cve.mitre.org)
has assigned the name CAN-2003-0388 to this issue.

When manipulating the entry in /var/log/lastlog, which corresponds to a
given user, the pam_lastlog module calculates the location of the entry by
multiplying the UID and the length of an entry in the file. On some
systems, the result of this calculation would mistakenly be truncated to 32
bits for users with sufficiently high UIDs.

All users of pam should upgrade to these updated packages, which
resolve these issues.