5.8 - RHSA-2015:2154

Problem Description:

Updated krb5 packages that fix two security issues, several bugs, and add various enhancements are now available for Red Hat Enterprise Linux 7.

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.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Client (v. 7) - x86_64 Red Hat Enterprise Linux Client Optional (v. 7) - x86_64 Red Hat Enterprise Linux ComputeNode (v. 7) - x86_64 Red Hat Enterprise Linux ComputeNode Optional (v. 7) - x86_64 Red Hat Enterprise Linux Server (v. 7) - aarch64, ppc64, ppc64le, s390x, x86_64 Red Hat Enterprise Linux Workstation (v. 7) - x86_64

3. Description:

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.

4. Solution:

Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

5. Bugs fixed (https://bugzilla.redhat.com/):

1156144 - krb5 upstream test t_kdb.py failure 1163402 - kdb5_ldap_util view_policy does not shows ticket flags on s390x and ppc64 1164304 - Upstream unit tests loads the installed shared libraries instead the ones from the build 1185770 - Missing upstream test in krb5-1.12.2: src/tests/gssapi/t_invalid.c 1193939 - CVE-2014-5355 krb5: unauthenticated denial of service in recvauth_common() and others 1203889 - RFE: Rebase krb5 in RHEL7.2 to krb5 1.13 (krb1.13.2) ... 1216133 - CVE-2015-2694 krb5: issues in OTP and PKINIT kdcpreauth modules leading to requires_preauth bypass 1222903 - [SELinux] AVC denials may appear when kadmind starts 1247608 - [RFE] Add support for multi-hop preauth mechs via |KDC_ERR_MORE_PREAUTH_DATA_REQUIRED| for RFC 6113 ("A Generalized Framework for Kerberos Pre-Authentication") 1247751 - krb5-config returns wrong -specs path 1247761 - RFE: Minor krb5 spec file cleanup and sync with recent Fedora 22/23 changes 1250154 - [s390x, ppc64, ppc64le]: kadmind does not accept ACL if kadm5.acl does not end with EOL 1251586 - KDC sends multiple requests to ipa-otpd for the same authentication 1259846 - KDC does not return proper client principal for client referrals