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.

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.

Due to the way the pam_ssh_agent_auth PAM module was built, 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)

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 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.

  - 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 servers.

  - 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.

The remote Oracle Linux 6 host has packages installed that are affected by a vulnerability as referenced in the ELSA-2013-0519 advisory.

    [5.3p1-84.1]
    - Add a 'netcat mode' (ssh -W) (#860809)

    [5.3p1-83]
    - fix the required authentications patch (#869903)

    [5.3p1-82]
    - check return value of PK11_Authenticate in ssh-add -n (#782912)
    - document available methods to RequiredAuthentications[12] (#821641)
    - fix ssh-copy-id (#836650)
    - fix segmentation fault in ssh client (#836655)
    - update pam_ssh_agent_auth to 0.9.3 upstream version
    - fix segfault in su when pam_ssh_agent_auth is used and the ssh-agent       is not running (#834404)

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Published	Updated	Severity
64766	RHEL 6 : openssh (RHSA-2013:0519)	Nessus	Red Hat Local Security Checks	2/21/2013	1/14/2021	medium
65150	CentOS 6 : openssh (CESA-2013:0519)	Nessus	CentOS Local Security Checks	3/10/2013	1/4/2021	medium
69724	Amazon Linux AMI : openssh (ALAS-2013-165)	Nessus	Amazon Linux Local Security Checks	9/4/2013	4/18/2018	medium
64954	Scientific Linux Security Update : openssh on SL6.x i386/x86_64 (20130221)	Nessus	Scientific Linux Local Security Checks	3/1/2013	1/14/2021	medium
68755	Oracle Linux 6 : openssh (ELSA-2013-0519)	Nessus	Oracle Linux Local Security Checks	7/12/2013	10/22/2024	critical

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