openssh (SL6)

Synopsis: Moderate: openssh security, bug fix, and enhancement update
Advisory ID: SLSA-2014:1552-2
Issue Date: 2014-10-14
CVE Numbers: CVE-2014-2532

It was discovered that OpenSSH clients did not correctly verify DNS SSHFP
records. A malicious server could use this flaw to force a connecting
client to skip the DNS SSHFP record check and require the user to perform
manual host verification of the DNS SSHFP record. (CVE-2014-2653)

It was found that OpenSSH did not properly handle certain AcceptEnv
parameter values with wildcard characters. A remote attacker could use
this flaw to bypass intended environment variable restrictions.

This update also fixes the following bugs:

* Based on the SP800-131A information security standard, the generation of
a digital signature using the Digital Signature Algorithm (DSA) with the
key size of 1024 bits and RSA with the key size of less than 2048 bits is
disallowed after the year 2013. After this update, ssh-keygen no longer
generates keys with less than 2048 bits in FIPS mode. However, the sshd
service accepts keys of size 1024 bits as well as larger keys for
compatibility reasons.

* Previously, the openssh utility incorrectly set the oom_adj value to -17
for all of its children processes. This behavior was incorrect because the
children processes were supposed to have this value set to 0. This update
applies a patch to fix this bug and oom_adj is now properly set to 0 for
all children processes as expected.

* Previously, if the sshd service failed to verify the checksum of an
installed FIPS module using the fipscheck library, the information about
this failure was only provided at the standard error output of sshd. As a
consequence, the user could not notice this message and be uninformed when
a system had not been properly configured for FIPS mode. To fix this bug,
this behavior has been changed and sshd now sends such messages via the
syslog service.

* When keys provided by the pkcs11 library were removed from the ssh agent
using the “ssh-add -e” command, the user was prompted to enter a PIN. With
this update, a patch has been applied to allow the user to remove the keys
provided by pkcs11 without the PIN.

In addition, this update adds the following enhancements:

* With this update, ControlPersist has been added to OpenSSH. The option
in conjunction with the ControlMaster configuration directive specifies
that the master connection remains open in the background after the
initial client connection has been closed.

* When the sshd daemon is configured to force the internal SFTP session,
and the user attempts to use a connection other than SFTP, the appropriate
message is logged to the /var/log/secure file.

* Support for Elliptic Curve Cryptography modes for key exchange (ECDH)
and host user keys (ECDSA) as specified by RFC5656 has been added to the
openssh packages. However, they are not enabled by default and the user
has to enable them manually.


– Scientific Linux Development Team