Synopsis

Moderate: openssh security, bug fix and enhancement update

Type/Severity

Security Advisory: Moderate

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)



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)



(/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)



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)



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)



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)



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 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

Fixes

CVEs

References