RHSA-2014:1552 - Security Advisory

Topic

Updated openssh packages that fix two security issues, several bugs, and
add various enhancements are now available for Red Hat Enterprise Linux 6.

Red Hat Product Security has rated this update as having Moderate security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

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

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. (CVE-2014-2532)

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. (BZ#993580)

• 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. (BZ#1010429)

• 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. (BZ#1020803)

• 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. (BZ#1042519)

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. (BZ#953088)

• 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. (BZ#997377)

• 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. For more information on how to configure ECDSA and
ECDH with OpenSSH, see: https://access.redhat.com/solutions/711953 (BZ#1028335)

All openssh users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues and add these
enhancements.

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/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 - 953088 - OpenSSH adding ControlPersist patch to enable full usage of SSH control options
• BZ - 1010429 - Openssh Incorrectly sets oom_adj in all Children after Performing a Reload
• BZ - 1023043 - ssh_config manual page lists incorrect default value of KexAlgorithms
• BZ - 1023044 - Fix man page for ssh-keygen because of certificate support
• BZ - 1027197 - X11 Forwarding does not work with default config - error: Failed to allocate internet-domain X11 display socket
• BZ - 1028643 - Connection remains when fork() fails.
• BZ - 1077843 - CVE-2014-2532 openssh: AcceptEnv environment restriction bypass flaw
• BZ - 1081338 - CVE-2014-2653 openssh: failure to check DNS SSHFP records in certain scenarios
• BZ - 1108836 - ssh-keyscan should ignore SIGPIPE
• BZ - 1111568 - AUTOCREATE_SERVER_KEYS=RSAONLY is not supported by init script

CVEs

• CVE-2014-2532
• CVE-2014-2653

References

• https://access.redhat.com/security/updates/classification/#moderate
• https://access.redhat.com/solutions/711953