Scientific Linux Security Update : openssh on SL7.x x86_64

This script is Copyright (C) 2015 Tenable Network Security, Inc.

Synopsis :

The remote Scientific Linux host is missing one or more security

Description :

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.

It was found that when OpenSSH was used in a Kerberos environment,
remote authenticated users were allowed to log in as a different user
if they were listed in the ~/.k5users file of that user, potentially
bypassing intended authentication restrictions. (CVE-2014-9278)

The openssh packages have been upgraded to upstream version 6.6.1,
which provides a number of bug fixes and enhancements over the
previous version.

Bug fixes :

- An existing /dev/log socket is needed when logging using
the syslog utility, which is not possible for all chroot
environments based on the user's home directories. As a
consequence, the sftp commands were not logged in the
chroot setup without /dev/log in the internal sftp
subsystem. With this update, openssh has been enhanced
to detect whether /dev/log exists. If /dev/log does not
exist, processes in the chroot environment use their
master processes for logging.

- The buffer size for a host name was limited to 64 bytes.
As a consequence, when a host name was 64 bytes long or
longer, the ssh-keygen utility failed. The buffer size
has been increased to fix this bug, and ssh-keygen no
longer fails in the described situation.

- Non-ASCII characters have been replaced by their octal
representations in banner messages in order to prevent
terminal re-programming attacks. Consequently, banners
containing UTF-8 strings were not correctly displayed in
a client. With this update, banner messages are
processed according to RFC 3454, control characters have
been removed, and banners containing UTF-8 strings are
now displayed correctly.

- Scientific Linux uses persistent Kerberos credential
caches, which are shared between sessions. Previously,
the GSSAPICleanupCredentials option was set to 'yes' by
default. Consequently, removing a Kerberos cache on
logout could remove unrelated credentials of other
sessions, which could make the system unusable. To fix
this bug, GSSAPICleanupCredentials is set by default to

- Access permissions for the /etc/ssh/moduli file were set
to 0600, which was unnecessarily strict. With this
update, the permissions for /etc/ssh/moduli have been
changed to 0644 to make the access to the file easier.

- Due to the KRB5CCNAME variable being truncated, the
Kerberos ticket cache was not found after login using a
Kerberos-enabled SSH connection. The underlying source
code has been modified to fix this bug, and Kerberos
authentication works as expected in the described

Enhancements :

- When the sshd daemon is configured to force the internal
SFTP session, a connection other then SFTP is used, the
appropriate message is logged to the /var/log/secure

- The sshd-keygen service was run using the
'ExecStartPre=-/usr/sbin/sshd- keygen' option in the
sshd.service unit file. With this update, the separate
sshd-keygen.service unit file has been added, and
sshd.service has been adjusted to require

See also :

Solution :

Update the affected packages.

Risk factor :

Medium / CVSS Base Score : 5.8

Family: Scientific Linux Local Security Checks

Nessus Plugin ID: 82258 ()

Bugtraq ID:

CVE ID: CVE-2014-2653

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