RHSA-2013:0519 - Security Advisory

Topic

Updated openssh packages that fix one security issue, multiple bugs, and
add various enhancements are now available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having moderate
security impact. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available from the CVE link in
the References section.

Description

OpenSSH is OpenBSD's Secure Shell (SSH) protocol implementation. These
packages include the core files necessary for the OpenSSH client and
server.

Due to the way the pam_ssh_agent_auth PAM module was built in Red Hat
Enterprise 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 Red Hat Enterprise
Linux 6 by default.

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. (BZ#821641)

• 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. (BZ#826720)

• 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. (BZ#836650)

• 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. (BZ#836655)

• 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. (BZ#857760)

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. (BZ#782912)

• 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 servers. (BZ#860809)

• 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. (BZ#869903)

All users of openssh are advised to upgrade to these updated packages,
which fix these issues and add these enhancements. After installing this
update, the OpenSSH server daemon (sshd) will be restarted automatically.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

• BZ - 821641 - Document possible options to RequiredAuthentications1/2
• BZ - 826720 - sshd initscript clobbers other sshd processes.
• BZ - 834618 - CVE-2012-5536 pam_ssh_agent_auth: symbol crash leading to glibc error() called incorrectly
• BZ - 836650 - ssh-copy-id returns 0 even if the actual operation fails.
• BZ - 857760 - Error/typo in openssh-ldap HOWTO file
• BZ - 869903 - RequiredAuthentications2 does not work in Match blocks as documented.

CVEs

• CVE-2012-5536

References

• https://access.redhat.com/security/updates/classification/#moderate