(RHSA-2015:2154) Moderate: krb5 security, bug fix, and enhancement update

Kerberos is a network authentication system, which can improve the security
of your network by eliminating the insecure practice of sending passwords
over the network in unencrypted form. It allows clients and servers to
authenticate to each other with the help of a trusted third party, the
Kerberos key distribution center (KDC).

It was found that the krb5_read_message() function of MIT Kerberos did not
correctly sanitize input, and could create invalid krb5_data objects.
A remote, unauthenticated attacker could use this flaw to crash a Kerberos
child process via a specially crafted request. (CVE-2014-5355)

A flaw was found in the OTP kdcpreauth module of MIT kerberos.
An unauthenticated remote attacker could use this flaw to bypass the
requires_preauth flag on a client principal and obtain a ciphertext
encrypted in the principal’s long-term key. This ciphertext could be used
to conduct an off-line dictionary attack against the user’s password.
(CVE-2015-2694)

The krb5 packages have been upgraded to upstream version 1.13.2, which
provides a number of bug fixes and enhancements over the previous version.
(BZ#1203889)

Notably, this update fixes the following bugs:

• Previously, the RADIUS support (libkrad) in krb5 was sending krb5
  authentication for Transmission Control Protocol (TCP) transports multiple
  times, accidentally using a code path intended to be used only for
  unreliable transport types, for example User Datagram Protocol (UDP)
  transports. A patch that fixes the problem by disabling manual retries for
  reliable transports, such as TCP, has been applied, and the correct code
  path is now used in this situation. (BZ#1251586)

• Attempts to use Kerberos single sign-on (SSO) to access SAP NetWeaver
  systems sometimes failed. The SAP NetWeaver developer trace displayed the
  following error message:

  No credentials were supplied, or the credentials were
  unavailable or inaccessible
  Unable to establish the security context

Querying SSO credential lifetime has been modified to trigger credential
acquisition, thus preventing the error from occurring. Now, the user can
successfully use Kerberos SSO for accessing SAP NetWeaver systems.
(BZ#1252454)

All krb5 users are advised to upgrade to these updated packages, which
correct these issues and add these enhancements.