(RHSA-2015:0425) Moderate: openssh security, bug fix and enhancement update

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 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.
(BZ#1059667)

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.
  (BZ#1083482)

• 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. (BZ#1097665)

• Non-ASCII characters have been replaced by their octal representations in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. (BZ#1104662)

• Red Hat Enterprise 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 “no”.
  (BZ#1134447)

• 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. (BZ#1134448)

• 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 situation. (BZ#1161173)

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 file. (BZ#1130198)

• 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 sshd-keygen.service. (BZ#1134997)

Users of openssh are advised to upgrade to these updated packages, which correct
these issues and add these enhancements.