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FreeBSD-SA-04:09.kadmind                                    Security Advisory
                                                          The FreeBSD Project

Topic:          heimdal kadmind remote heap buffer overflow

Category:       contrib
Module:         crypto_heimdal
Announced:      2004-05-05
Credits:        Evgeny Demidov, VulnDisco, Love Hornquist-Astrand
Affects:        FreeBSD 4 systems built with both Kerberos 4 and Kerberos 5.
                FreeBSD 5 systems prior to 5.1 built with both Kerberos 4 and
                Kerberos 5.
Corrected:      2004-05-05 20:19:48 UTC (RELENG_4, 4.10-PRERELEASE)
                2004-05-05 20:48:57 UTC (RELENG_4_10, 4.10-RELEASE-RC)
                2004-05-05 20:15:56 UTC (RELENG_4_9, 4.9-RELEASE-p7)
                2004-05-05 20:17:51 UTC (RELENG_4_8, 4.8-RELEASE-p20)
CVE Name:       CAN-2004-0434
FreeBSD only:   NO

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

Heimdal implements the Kerberos 5 network authentication protocols.
The k5admind(8) daemon provides the administrative interface to the
Kerberos Key Distribution Center (KDC).  In some configurations,
k5admind also includes Kerberos 4 compatibility.

NOTE: FreeBSD versions prior to 5.1-RELEASE contain optional Kerberos
4 support.  FreeBSD versions 5.1-RELEASE and later do not include
Kerberos 4 support of any kind.

II.  Problem Description

An input validation error was discovered in the k5admind code that
handles the framing of Kerberos 4 compatibility administration
requests.  The code assumed that the length given in the framing was
always two or more bytes.  Smaller lengths will cause k5admind to read
an arbitrary amount of data into a minimally-sized buffer on the heap.

Note that this code is not present unless k5admind has been compiled
with Kerberos 4 support.  This will occur if a FreeBSD system is
compiled with both of the WITH_KERBEROS4 and WITH_KERBEROS5 build flags.
These flags are never simultaneously set during the FreeBSD binary
release process; consequently, binary installs of FreeBSD (even with
Kerberos support installed) are not affected.

III. Impact

A remote attacker may send a specially formatted message to k5admind,
causing it to crash or possibly resulting in arbitrary code execution.

IV.  Workaround

Disable the Kerberos 4 support in k5admind by running it with the
`--no-kerberos4' option.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE; or to the RELENG_4_9 or
RELENG_4_8 security branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.8 and
4.9.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:09/kadmind.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:09/kadmind.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/kerberos5/tools
# make obj && make depend && make
# cd /usr/src/kerberos5/lib
# make obj && make depend && make
# cd /usr/src/kerberos5/libexec/k5admind
# make obj && make depend && make all install

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_4
  src/crypto/heimdal/kadmin/version4.c                        1.1.1.1.2.6
RELENG_4_10
  src/crypto/heimdal/kadmin/version4.c                    1.1.1.1.2.5.6.1
RELENG_4_9
  src/UPDATING                                              1.73.2.89.2.8
  src/crypto/heimdal/kadmin/version4.c                    1.1.1.1.2.5.4.1
  src/sys/conf/newvers.sh                                   1.44.2.32.2.8
RELENG_4_8
  src/UPDATING                                             1.73.2.80.2.23
  src/crypto/heimdal/kadmin/version4.c                    1.1.1.1.2.5.2.1
  src/sys/conf/newvers.sh                                  1.44.2.29.2.21
- -------------------------------------------------------------------------
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