(RHSA-2010:0891) Moderate: pam security update

Pluggable Authentication Modules (PAM) provide a system whereby
administrators can set up authentication policies without having to
recompile programs that handle authentication.

It was discovered that the pam_namespace module executed the external
script namespace.init with an unchanged environment inherited from an
application calling PAM. In cases where such an environment was untrusted
(for example, when pam_namespace was configured for setuid applications
such as su or sudo), a local, unprivileged user could possibly use this
flaw to escalate their privileges. (CVE-2010-3853)

It was discovered that the pam_env and pam_mail modules used root
privileges while accessing user’s files. A local, unprivileged user could
use this flaw to obtain information, from the lines that have the KEY=VALUE
format expected by pam_env, from an arbitrary file. Also, in certain
configurations, a local, unprivileged user using a service for which the
pam_mail module was configured for, could use this flaw to obtain limited
information about files or directories that they do not have access to.
(CVE-2010-3435)

Note: As part of the fix for CVE-2010-3435, this update changes the default
value of pam_env’s configuration option user_readenv to 0, causing the
module to not read user’s ~/.pam_environment configuration file by default,
as reading it may introduce unexpected changes to the environment of the
service using PAM, or PAM modules consulted after pam_env.

It was discovered that the pam_xauth module did not verify the return
values of the setuid() and setgid() system calls. A local, unprivileged
user could use this flaw to execute the xauth command with root privileges
and make it read an arbitrary input file. (CVE-2010-3316)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for
reporting the CVE-2010-3435 issue.

All pam users should upgrade to these updated packages, which contain
backported patches to correct these issues.