Moderate: openssh (SL6)

Synopsis: Moderate: openssh security, bug fix and enhancement update
Issue Date: 2013-02-21
CVE Numbers: CVE-2012-5536

Due to the way the pam_ssh_agent_auth PAM module was built in Scientific Linux
6, the glibc’s error() function was called rather than the intended error()
function in pam_ssh_agent_auth to report errors. As these two functions expect
different arguments, it was possible for an attacker to cause an application
using pam_ssh_agent_auth to crash, disclose portions of its memory or,
potentially, execute arbitrary code. (CVE-2012-5536)

Note that the pam_ssh_agent_auth module is not used in Scientific Linux 6 by

This update also fixes the following bugs:

* All possible options for the new RequiredAuthentications directive were not
documented in the sshd_config man page. This update improves the man page to
document all the possible options.

* When stopping one instance of the SSH daemon (sshd), the sshd init script
(/etc/rc.d/init.d/sshd) stopped all sshd processes regardless of the PID of the
processes. This update improves the init script so that it only kills processes
with the relevant PID. As a result, the init script now works more reliably in
a multi-instance environment.

* Due to a regression, the ssh-copy-id command returned an exit status code of
zero even if there was an error in copying the key to a remote host. With this
update, a patch has been applied and ssh-copy-id now returns a non-zero exit
code if there is an error in copying the SSH certificate to a remote host.

* When SELinux was disabled on the system, no on-disk policy was installed, a
user account was used for a connection, and no “~/.ssh” configuration was
present in that user’s home directory, the SSH client terminated unexpectedly
with a segmentation fault when attempting to connect to another system. A patch
has been provided to address this issue and the crashes no longer occur in the
described scenario.

* The “HOWTO” document /usr/share/doc/openssh-ldap-5.3p1/HOWTO.ldap-keys
incorrectly documented the use of the AuthorizedKeysCommand directive. This
update corrects the document.

This update also adds the following enhancements:

* When attempting to enable SSH for use with a Common Access Card (CAC), the
ssh-agent utility read all the certificates in the card even though only the ID
certificate was needed. Consequently, if a user entered their PIN incorrectly,
then the CAC was locked, as a match for the PIN was attempted against all three
certificates. With this update, ssh-add does not try the same PIN for every
certificate if the PIN fails for the first one. As a result, the CAC will not
be disabled if a user enters their PIN incorrectly.

* This update adds a “netcat mode” to SSH. The “ssh -W host:port …” command
connects standard input and output (stdio) on a client to a single port on a
server. As a result, SSH can be used to route connections via intermediate

* Due to a bug, arguments for the RequiredAuthentications2 directive were not
stored in a Match block. Consequently, parsing of the config file was not in
accordance with the man sshd_config documentation. This update fixes the bug
and users can now use the required authentication feature to specify a list of
authentication methods as expected according to the man page.

After installing this update, the OpenSSH server daemon (sshd) will be
restarted automatically.


– Scientific Linux Development Team