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FreeBSD-SA-07:05.libarchive                                 Security Advisory
                                                          The FreeBSD Project

Topic:          Errors handling corrupt tar files in libarchive(3)

Category:       core
Module:         libarchive
Announced:      2007-07-12
Credits:        CPNI, CERT-FI, Tim Kientzle, Colin Percival
Affects:        FreeBSD 5.3 and later.
Corrected:      2007-07-12 15:00:44 UTC (RELENG_6, 6.2-STABLE)
                2007-07-12 15:01:14 UTC (RELENG_6_2, 6.2-RELEASE-p6)
                2007-07-12 15:01:32 UTC (RELENG_6_1, 6.1-RELEASE-p18)
                2007-07-12 15:01:42 UTC (RELENG_5, 5.5-STABLE)
                2007-07-12 15:01:56 UTC (RELENG_5_5, 5.5-RELEASE-p14)
CVE Name:       CVE-2007-3641, CVE-2007-3644, CVE-2007-3645

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

I.   Background

The libarchive library provides a flexible interface for reading and
writing streaming archive files such as tar and cpio, and has been the
basis for FreeBSD's implementation of the tar(1) utility since FreeBSD 5.3.

II.  Problem Description

Several problems have been found in the code used to parse the tar and
pax interchange formats.  These include entering an infinite loop if an
archive prematurely ends within a pax extension header or if certain
types of corruption occur in pax extension headers [CVE-2007-3644];
dereferencing a NULL pointer if an archive prematurely ends within a
tar header immediately following a pax extension header or if certain
other types of corruption occur in pax extension headers [CVE-2007-3645];
and miscomputing the length of a buffer resulting in a buffer overflow
if yet another type of corruption occurs in a pax extension header
[CVE-2007-3641].

III. Impact

An attacker who can cause a corrupt archive of his choice to be parsed
by libarchive, including by having "tar -x" (extract) or "tar -t" (list
entries) run on it, can cause libarchive to enter an infinite loop, to
core dump, or possibly to execute arbitrary code provided by the
attacker.

IV.  Workaround

No workaround is available, but systems which do not read tar or pax
extension archives provided by untrusted sources are not vulnerable.
Note that while these issues do not affect libarchive's ability to
parse cpio, ISO9660, or zip format archives, libarchive automatically
detects the format of an archive, so external metadata (e.g., a file
name) is not sufficient to ensure that a file will not be parsed using
the vulnerable tar/pax format parser.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE, or 6-STABLE, or to the
RELENG_6_2, RELENG_6_1, or RELENG_5_5 security branch dated after the
correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 5.5, 6.1,
and 6.2 systems.

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

# fetch http://security.FreeBSD.org/patches/SA-07:05/libarchive.patch
# fetch http://security.FreeBSD.org/patches/SA-07:05/libarchive.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libarchive
# make obj && make depend && make && make install
# cd /usr/src/rescue
# make obj && make depend && make && make install

NOTE: On the amd64 platform, the above procedure will not update the
lib32 (i386 compatibility) libraries.  On amd64 systems where the i386
compatibility libraries are used, the operating system should instead
be recompiled as described in
<URL:http://www.freebsd.org/handbook/makeworld.html>

VI.  Correction details

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

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_5
  src/lib/libarchive/archive_read_support_format_tar.c           1.26.2.8
RELENG_5_5
  src/UPDATING                                            1.342.2.35.2.14
  src/sys/conf/newvers.sh                                  1.62.2.21.2.16
  src/lib/libarchive/archive_read_support_format_tar.c       1.26.2.7.2.1
RELENG_6
  src/lib/libarchive/archive_read_support_format_tar.c           1.32.2.5
RELENG_6_2
  src/UPDATING                                             1.416.2.29.2.9
  src/sys/conf/newvers.sh                                   1.69.2.13.2.9
  src/lib/libarchive/archive_read_support_format_tar.c       1.32.2.2.2.1
RELENG_6_1
  src/UPDATING                                            1.416.2.22.2.20
  src/sys/conf/newvers.sh                                  1.69.2.11.2.20
  src/lib/libarchive/archive_read_support_format_tar.c           1.32.6.1
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3641
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3644
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3645

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-07:05.libarchive.asc
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