FreeBSD: cvs Chroot escape vulnerability
Posted by LinuxSecurity.com Team   
FreeBSD This patch fixes two cvs errors, one with the client and one with the server. Both allow chroot escapes.

FreeBSD-SA-04:07.cvs                                        Security Advisory
                                                          The FreeBSD Project

Topic:          CVS path validation errors

Category:       contrib
Module:         contrib_cvs
Announced:      2004-04-15
Credits:        Sebastian Krahmer <krahmer@suse.de>
                Derek Robert Price <derek@ximbiot.com>
Affects:        All FreeBSD versions prior to 4.10-RELEASE
Corrected:      2004-04-15 15:35:26 UTC (RELENG_4, 4.10-BETA)
                2004-04-15 15:42:50 UTC (RELENG_5_2, 5.2.1-RELEASE-p5)
                2004-04-15 15:59:05 UTC (RELENG_4_9, 4.9-RELEASE-p18)
                2004-04-15 15:59:54 UTC (RELENG_4_8, 4.8-RELEASE-p5)
CVE Name:       CAN-2004-0180
FreeBSD only:   NO

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

I.   Background

The Concurrent Versions System (CVS) is a version control system.  It
may be used to access a repository locally, or to access a `remote
repository' using a number of different methods.  When accessing a
remote repository, the target machine runs the CVS server to fulfill
client requests.

II.  Problem Description

Two programming errors were discovered in which path names handled by
CVS were not properly validated.  In one case, the CVS client accepts
absolute path names from the server when determining which files to
update.  In another case, the CVS server accepts relative path names
from the client when determining which files to transmit, including
those containing references to parent directories (`../').

III. Impact

These programming errors generally only have a security impact when
dealing with remote CVS repositories.

A malicious CVS server may cause a CVS client to overwrite arbitrary
files on the client's system.

A CVS client may request RCS files from a remote system other than
those in the repository specified by $CVSROOT.  These RCS files need
not be part of any CVS repository themselves.

IV.  Workaround

Disable remote CVS repository operations.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE; or to the RELENG_5_2,
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,
4.9, 5.1, and 5.2 systems.

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-04:07/cvs.patch
# fetch  ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:07/cvs.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/gnu/usr.bin/cvs
# make obj && make depend && make && make 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/contrib/cvs/src/client.c                                    1.2.2.7
  src/contrib/cvs/src/modules.c                               1.1.1.5.2.4
RELENG_5_2
  src/UPDATING                                                 1.282.2.13
  src/sys/conf/newvers.sh                                       1.56.2.12
  src/contrib/cvs/src/client.c                                   1.10.4.1
  src/contrib/cvs/src/modules.c                               1.1.1.8.6.2
RELENG_4_9
  src/UPDATING                                              1.73.2.89.2.6
  src/sys/conf/newvers.sh                                   1.44.2.32.2.6
  src/contrib/cvs/src/client.c                                1.2.2.6.4.1
  src/contrib/cvs/src/modules.c                           1.1.1.5.2.3.4.1
RELENG_4_8
  src/UPDATING                                             1.73.2.80.2.21
  src/sys/conf/newvers.sh                                  1.44.2.29.2.19
  src/contrib/cvs/src/client.c                                1.2.2.6.2.1
  src/contrib/cvs/src/modules.c                           1.1.1.5.2.3.2.1
- -------------------------------------------------------------------------

VII. References
 
http://ccvs.cvshome.org/servlets/NewsItemView?newsID=102