RHBA-2008:0381 - Bug Fix Advisory

Topic

Updated krb5 packages that resolve several issues are now available.

Description

Kerberos is an authentication system which permits clients and servers to
authenticate to each other with the help of a trusted third party and
symmetric-key cryptography.

A flaw was found in the way the MIT Kerberos Authentication Service and Key
Distribution Center server (krb5kdc) handled Kerberos v4 protocol packets.
An un-authenticated remote attacker could use this flaw to crash the
krb5kdc daemon, disclose portions of its memory, or possibly execute
arbitrary code using malformed or truncated Kerberos v4 protocol requests.
(CVE-2008-0062, CVE-2008-0063)

This issue only affected krb5kdc with Kerberos v4 protocol compatibility
enabled, which is the default setting on Red Hat Enterprise Linux 4.
Kerberos v4 protocol support can be disabled by akdding "v4_mode=none"
(without the quotes) to the "[kdcdefaults]" section of
/var/kerberos/krb5kdc/kdc.conf.

Jeff Altman of Secure Endpoints discovered a flaw in the RPC library as
used by MIT Kerberos kadmind server. An un-authenticated remote attacker
could use this flaw to crash kadmind or possibly execute arbitrary code.
This issue only affected systems with certain resource limits configured
and did not affect systems using default resource limits used by Red Hat
Enterprise Linux 5. (CVE-2008-0947)

Red Hat would like to thank MIT for reporting these issues.

Multiple memory management flaws were discovered in the GSSAPI library used
by MIT Kerberos. These flaws could possibly result in use of already freed
memory or an attempt to free already freed memory blocks (double-free
flaw), possibly causing a crash or arbitrary code execution.
(CVE-2007-5901, CVE-2007-5971)

In addition, these updated krb5 packages provide fixes for the following bugs:

• delegated krb5 credentials were not properly stored when SPNEGO was the

underlying mechanism during GSSAPI authentication. SPNEGO credentials can
now be properly searched, and applications can copy delegated credentials
as expected.

• applications can initiate context acceptance (via gss_accept_sec_context)

without passing a ret_flags value that would indicate that credentials were
delegated.

• password change requests would fail if the primary server was unavailable

when libkrb5 generated a set- or change-password request.

• quality checks on the setting of a new password were bypassed when a user

attempted to log in remotely with an expired password.

• when a user's password expired, kinit would not prompt that user to

change the password. kinit now prompts the user to set a new password.

• the mget command was unable to successfully download and set SELinux labels.
• the mget command was unable to transfer files when runique was turned on.
• attempts to download non-existent files via FTP would sockets to remain open.
• the krb5 init scripts have been updated to conform more closely to init

script guidelines.

• if a Key Distribution Center (KDC) returned a KDC_ERR_SVC_UNAVAILABLE

code, the next KDC was not tried.

• kadmin would print a misleading "too many arguments" error message to the

console under certain conditions.

• kpasswd did not fall back to TCP on receipt of certain errors, or when a

packet was too big for UDP. This update corrects this.

• Kerberos password expiration warnings were based on principal expiration

rather than user password expiration.

• the kpasswd command would attempt to determine the user's principal name

by reading it from the user's credential cache. If an access error
occurred, kpasswd would fail rather than being handled gracefully.

• in the telnet man pages, the description of the escape character as

announced on program invocation was misleading if rlogin mode was selected.

• a package verification problem.
• support for the Red Hat Directory Server's nsAccountLock attribute was added.
• the manual page for kdc.conf was missing a section on the 'kdc_tcp_ports'

option.

Users are advised to upgrade to these updated krb5 packages, which resolve
these issues.

Solution

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

This update is available via Red Hat Network. Details on how to use
the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/FAQ_58_10188

Affected Products

• Red Hat Enterprise Linux Server 5 x86_64
• Red Hat Enterprise Linux Server 5 ia64
• Red Hat Enterprise Linux Server 5 i386
• Red Hat Enterprise Linux Workstation 5 x86_64
• Red Hat Enterprise Linux Workstation 5 i386
• Red Hat Enterprise Linux Desktop 5 x86_64
• Red Hat Enterprise Linux Desktop 5 i386
• Red Hat Enterprise Linux for IBM z Systems 5 s390x
• Red Hat Enterprise Linux for Power, big endian 5 ppc
• Red Hat Enterprise Linux Server from RHUI 5 x86_64
• Red Hat Enterprise Linux Server from RHUI 5 i386

Fixes

• BZ - 242500 - Wrong init script
• BZ - 247633 - ftp client: runique on stops mget from working
• BZ - 247741 - Documentation of rlogin mode is misleading
• BZ - 248618 - ftp leaks socket fds when it fails to open a file
• BZ - 248631 - kpasswd insists on a valid credentials cache and doesn't use the UID
• BZ - 314651 - gss_init_sec_context() mechglue wrapper doesn't handle ret_flags right
• BZ - 319351 - gss_krb5_copy_ccache can't find delegated Kerberos creds when using SPNEGO
• BZ - 329771 - Rpm Verify Fails - krb5.conf needs %verify(not md5 size mtime) in %config
• BZ - 381011 - /etc/init.d/kadmin: line 35: [: too many arguments
• BZ - 392631 - kpasswd does not fallback to tcp
• BZ - 413051 - kinit does not automatically start a password change when password is expired
• BZ - 426085 - kerberos ftp receives sigabort on mget since krb5-1.6.1-selinux-label.patch
• BZ - 427789 - krb5 password changing uses incorrect sequence numbers for every server but the first
• BZ - 431784 - RFE: Support for Directory Server specify account lock attribute

CVEs

(none)

References

(none)