krb5 (SL5)

Synopsis: Low: krb5 security and bug fix update
Issue Date: 2012-02-20
CVE Numbers: CVE-2011-1526

Kerberos is a network authentication system which allows clients and
servers to authenticate to each other using symmetric encryption and a
trusted third-party, the Key Distribution Center (KDC).

It was found that ftpd, a Kerberos-aware FTP server, did not properly drop
privileges. On Red Hat Enterprise Linux 5, the ftpd daemon did not check
for the potential failure of the effective group ID change system call. If
the group ID change failed, a remote FTP user could use this flaw to gain
unauthorized read or write access to files that are owned by the root
group. (CVE-2011-1526)

Red Hat would like to thank the MIT Kerberos project for reporting this
issue. Upstream acknowledges Tim Zingelman as the original reporter.

This update also fixes the following bugs:

* Due to a mistake in the Kerberos libraries, a client could fail to
contact a Key Distribution Center (KDC) or terminate unexpectedly if the
client had already more than 1024 file descriptors in use. This update
backports modifications to the Kerberos libraries and the libraries use
the poll() function instead of the select() function, as poll() does not
have this limitation. (BZ#701444)

* The KDC failed to release memory when processing a TGS (ticket-granting
server) request from a client if the client request included an
authenticator with a subkey. As a result, the KDC consumed an excessive
amount of memory. With this update, the code releasing the memory has been
added and the problem no longer occurs. (BZ#708516)

* Under certain circumstances, if services requiring Kerberos
authentication sent two authentication requests to the authenticating
server, the second authentication request was flagged as a replay attack.
As a result, the second authentication attempt was denied. This update
applies an upstream patch that fixes this bug. (BZ#713500)

* Previously, if Kerberos credentials had expired, the klist command could
terminate unexpectedly with a segmentation fault when invoked with the -s
option. This happened when klist encountered and failed to process an entry
with no realm name while scanning the credential cache. With this update,
the underlying code has been modified and the command handles such entries
correctly. (BZ#729067)

* Due to a regression, multi-line FTP macros terminated prematurely with a
segmentation fault. This occurred because the previously-added patch failed
to properly support multi-line macros. This update restores the support for
multi-line macros and the problem no longer occurs. (BZ#735363, BZ#736132)

All users of krb5 are advised to upgrade to these updated packages, which
resolve these issues.


– Scientific Linux Development Team