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FreeBSD-SA-05:14.bzip2                                      Security Advisory
                                                          The FreeBSD Project

Topic:          bzip2 denial of service and permission race vulnerabilities

Category:       contrib
Module:         contrib_bzip2
Announced:      2005-06-29
Credits:        Imran Ghory, Chris Evans
Affects:        All FreeBSD releases
Corrected:      2005-06-29 21:38:48 UTC (RELENG_5, 5.4-STABLE)
                2005-06-29 21:41:03 UTC (RELENG_5_4, 5.4-RELEASE-p3)
                2005-06-29 21:42:33 UTC (RELENG_5_3, 5.3-RELEASE-p17)
                2005-06-29 21:43:42 UTC (RELENG_4, 4.11-STABLE)
                2005-06-29 21:45:14 UTC (RELENG_4_11, 4.11-RELEASE-p11)
                2005-06-29 21:46:15 UTC (RELENG_4_10, 4.10-RELEASE-p16)
CVE Name:       CAN-2005-0953, CAN-2005-1260

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

bzip2 is a block-sorting file compression utility.

II.  Problem Description

Two problems have been discovered relating to the extraction of
bzip2-compressed files.  First, a carefully constructed invalid bzip2
archive can cause bzip2 to enter an infinite loop.  Second, when
creating a new file, bzip2 closes the file before setting its
permissions.

III. Impact

The first problem can cause bzip2 to extract a bzip2 archive to an
infinitely large file.  If bzip2 is used in automated processing of
untrusted files this could be exploited by an attacker to create an
denial-of-service situation by exhausting disk space or by consuming
all available cpu time.

The second problem can allow a local attacker to change the
permissions of local files owned by the user executing bzip2 providing
that they have write access to the directory in which the file is
being extracted.

IV.  Workaround

Do not uncompress bzip2 archives from untrusted sources and do not
uncompress files in directories where untrusted users have write
access.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the
RELENG_5_4, RELENG_5_3, RELENG_4_11, or RELENG_4_10 security branch
dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.10,
4.11, 5.3, and 5.4 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-05:14/bzip2.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:14/bzip2.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libbz2
# make obj && make depend && make && make install
# cd /usr/src/usr.bin/bzip2
# 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
  contrib/bzip2/bzip2.c                                       1.1.1.1.2.3
  contrib/bzip2/bzlib.c                                       1.1.1.1.2.3
  contrib/bzip2/compress.c                                    1.1.1.1.2.3
  contrib/bzip2/decompress.c                                  1.1.1.1.2.3
  contrib/bzip2/huffman.c                                     1.1.1.1.2.3
RELENG_4_11
  src/UPDATING                                             1.73.2.91.2.12
  src/sys/conf/newvers.sh                                  1.44.2.39.2.15
  contrib/bzip2/bzip2.c                                  1.1.1.1.2.2.12.1
  contrib/bzip2/bzlib.c                                  1.1.1.1.2.2.12.1
  contrib/bzip2/compress.c                               1.1.1.1.2.2.12.1
  contrib/bzip2/decompress.c                             1.1.1.1.2.2.12.1
  contrib/bzip2/huffman.c                                1.1.1.1.2.2.12.1
RELENG_4_10
  src/UPDATING                                             1.73.2.90.2.17
  src/sys/conf/newvers.sh                                  1.44.2.34.2.18
  contrib/bzip2/bzip2.c                                  1.1.1.1.2.2.10.1
  contrib/bzip2/bzlib.c                                  1.1.1.1.2.2.10.1
  contrib/bzip2/compress.c                               1.1.1.1.2.2.10.1
  contrib/bzip2/decompress.c                             1.1.1.1.2.2.10.1
  contrib/bzip2/huffman.c                                1.1.1.1.2.2.10.1
RELENG_5
  contrib/bzip2/bzip2.c                                       1.1.1.2.8.1
  contrib/bzip2/bzlib.c                                       1.1.1.2.8.1
  contrib/bzip2/compress.c                                    1.1.1.2.8.1
  contrib/bzip2/decompress.c                                  1.1.1.2.8.1
  contrib/bzip2/huffman.c                                     1.1.1.2.8.1
RELENG_5_4
  src/UPDATING                                            1.342.2.24.2.12
  src/sys/conf/newvers.sh                                   1.62.2.18.2.8
  contrib/bzip2/bzip2.c                                      1.1.1.2.12.1
  contrib/bzip2/bzlib.c                                      1.1.1.2.12.1
  contrib/bzip2/compress.c                                   1.1.1.2.12.1
  contrib/bzip2/decompress.c                                 1.1.1.2.12.1
  contrib/bzip2/huffman.c                                    1.1.1.2.12.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.20
  src/sys/conf/newvers.sh                                  1.62.2.15.2.22
  contrib/bzip2/bzip2.c                                      1.1.1.2.10.1
  contrib/bzip2/bzlib.c                                      1.1.1.2.10.1
  contrib/bzip2/compress.c                                   1.1.1.2.10.1
  contrib/bzip2/decompress.c                                 1.1.1.2.10.1
  contrib/bzip2/huffman.c                                    1.1.1.2.10.1
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-0953
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1260
http://marc.theaimsgroup.com/?l=bugtraq&m=111229375217633
http://scary.beasts.org/security/CESA-2005-002.txt

The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:14.bzip.asc
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