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Category:   Application (Generic)  >   ee Vendors:   FreeBSD
FreeBSD ee Unsafe Temporary Files May Let Local Users Gain Elevated Privileges
SecurityTracker Alert ID:  1015469
SecurityTracker URL:  http://securitytracker.com/id/1015469
CVE Reference:   CVE-2006-0055   (Links to External Site)
Date:  Jan 11 2006
Impact:   Modification of system information, Modification of user information, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  

Description:   A vulnerability was reported in 'ee' on FreeBSD. A local user may be able to obtain elevated privileges on the target system.

The ee(1) utility uses temporary files in an unsafe manner when performing spell check operations. The ispell_op() function is affected. As a result, a local user can create a symbolic link (symlink) from a critical file on the system to a temporary file to be used by ee. Then, when the target user runs ee, the symlinked file may be overwritten with the privileges of the target user.

Impact:   A local user may be able to cause files to be modified with the privileges of the target user running texindex.
Solution:   FreeBSD has provided the following fix [quoted]:

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_0, 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, 5.4, and 6.0 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-06:02/ee.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:02/ee.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/usr.bin/ee
# make obj && make depend && make && make install

The vendor's advisory is available at:

ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:02.ee.asc

Vendor URL:  www.freebsd.org/security/ (Links to External Site)
Cause:   Access control error, State error
Underlying OS:  UNIX (FreeBSD)

Message History:   None.


 Source Message Contents

Subject:  FreeBSD Security Advisory FreeBSD-SA-06:02.ee

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

=============================================================================
FreeBSD-SA-06:02.ee                                         Security Advisory
                                                          The FreeBSD Project

Topic:          ee temporary file privilege escalation

Category:       core
Module:         ee
Announced:      2006-01-11
Credits:        Christian S.J. Peron
Affects:        All FreeBSD versions
Corrected:      2006-01-11 08:02:16 UTC (RELENG_6, 6.0-STABLE)
                2006-01-11 08:03:18 UTC (RELENG_6_0, 6.0-RELEASE-p2)
                2006-01-11 08:03:55 UTC (RELENG_5, 5.4-STABLE)
                2006-01-11 08:04:33 UTC (RELENG_5_4, 5.4-RELEASE-p9)
                2006-01-11 08:05:54 UTC (RELENG_5_3, 5.3-RELEASE-p24)
                2006-01-11 08:06:47 UTC (RELENG_4, 4.11-STABLE)
                2006-01-11 08:07:18 UTC (RELENG_4_11, 4.11-RELEASE-p14)
                2006-01-11 08:08:08 UTC (RELENG_4_10, 4.10-RELEASE-p20)
CVE Name:       CVE-2006-0055

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

The ee utility is a simple screen oriented text editor. This editor is
popular with a lot of users due to its ease of use.

II.  Problem Description

The ispell_op function used by ee(1) while executing spell check
operations employs an insecure method of temporary file generation.
This method produces predictable file names based on the process ID
and fails to confirm which path will be over written with the user.

It should be noted that ispell does not have to be installed in order
for this to be exploited.  The option simply needs to be selected.

III. Impact

These predictable temporary file names are problematic because they
allow an attacker to take advantage of a race condition in order to
execute a symlink attack, which could allow them to overwrite files
on the system in the context of the user running the ee(1) editor.

IV.  Workaround

Instead of invoking ispell through ee(1), invoke it directly.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_0, 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, 5.4, and 6.0 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-06:02/ee.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:02/ee.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/usr.bin/ee
# 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
  usr.bin/ee/ee.c                                                1.16.2.9
RELENG_4_11
  src/UPDATING                                             1.73.2.91.2.15
  src/sys/conf/newvers.sh                                  1.44.2.39.2.18
  usr.bin/ee/ee.c                                            1.16.2.7.6.1
RELENG_4_10
  src/UPDATING                                             1.73.2.90.2.21
  src/sys/conf/newvers.sh                                  1.44.2.34.2.22
  usr.bin/ee/ee.c                                            1.16.2.7.4.1
RELENG_5
  usr.bin/ee/ee.c                                                1.31.4.2
RELENG_5_4
  src/UPDATING                                            1.342.2.24.2.18
  src/sys/conf/newvers.sh                                  1.62.2.18.2.14
  usr.bin/ee/ee.c                                            1.31.4.1.2.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.27
  src/sys/conf/newvers.sh                                  1.62.2.15.2.29
  usr.bin/ee/ee.c                                                1.31.6.1
RELENG_6
  usr.bin/ee/ee.c                                                1.32.2.1
RELENG_6_0
  src/UPDATING                                              1.416.2.3.2.7
  src/sys/conf/newvers.sh                                    1.69.2.8.2.3
  usr.bin/ee/ee.c                                                1.32.4.1
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0055

The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:02.ee.asc
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