FreeBSD Security Advisory FreeBSD-SA-01:57.sendmail

[FreeBSD Security Advisories]

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=============================================================================
FreeBSD-SA-01:57                                           Security Advisory
                                                                FreeBSD, Inc.

Topic:          sendmail contains local root vulnerability

Category:       core
Module:         sendmail
Announced:      2001-08-27
Credits:        Cade Cairnss <cairnsc at securityfocus.com>
Affects:        FreeBSD 4-STABLE after August 27, 2000 and prior to
                the correction date, FreeBSD 4.1.1-RELEASE,
                4.2-RELEASE, 4.3-RELEASE
Corrected:      2001-08-21 01:36:37 UTC (FreeBSD 4.3-STABLE)
                2001-08-22 05:34:11 UTC (RELENG_4_3)
FreeBSD only:   NO

I.   Background

sendmail is a mail transfer agent.

II.  Problem Description

Sendmail contains an input validation error which may lead to the
execution of arbitrary code with elevated privileges by local users.
Due to the improper use of signed integers in code responsible for the
processing of debugging arguments, a local user may be able to supply
the signed integer equivalent of a negative value supplied to
sendmail's "trace vector".  This may allow a local user to write data
anywhere within a certain range of locations in process memory.
Because the '-d' command-line switch is processed before the program
drops its elevated privileges, the attacker may be able to cause
arbitrary code to be executed with root privileges. 

III. Impact

Local users may be able to execute arbitrary code with root privileges.

IV.  Workaround

Do not allow untrusted users to execute the sendmail binary.

V.   Solution

One of the following:

1) Upgrade your vulnerable FreeBSD system to 4.3-STABLE or the
RELENG_4_3 security branch after the respective correction dates.

2) FreeBSD 4.x systems after August 27, 2000 and prior to the
correction date:

The following patch has been verified to apply to FreeBSD
4.1.1-RELEASE, 4.2-RELEASE, 4.3-RELEASE and 4-STABLE dated prior to
the correction date.

Download the patch and the detached PGP signature from the following
locations, and verify the signature using your PGP utility.

# fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:57/sendmail.patch
# fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:57/sendmail.patch.asc

Execute the following commands as root:

# cd /usr/src
# patch -p < /path/to/patch
# cd /usr/src/lib/libsmutil
# make depend && make all
# cd /usr/src/usr.sbin/sendmail
# make depend && make all install

3) FreeBSD 4.3-RELEASE systems:

An experimental upgrade package is available for users who wish to
provide testing and feedback on the binary upgrade process.  This
package may be installed on FreeBSD 4.3-RELEASE systems only, and is
intended for use on systems for which source patching is not practical
or convenient.

If you use the upgrade package, feedback (positive or negative) to
security-officer at FreeBSD.org is requested so we can improve the
process for future advisories.

During the installation procedure, backup copies are made of the
files which are replaced by the package.  These backup copies will
be reinstalled if the package is removed, reverting the system to a
pre-patched state.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:57/security-patch-sendmail-01.57.tgz
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/packages/SA-01:57/security-patch-sendmail-01.57.tgz.asc

Verify the detached PGP signature using your PGP utility.

# pkg_add security-patch-sendmail-01:57.tgz

Restart sendmail after applying the patch by executing the following
commands as root:

# killall sendmail
# /usr/sbin/sendmail -bd -q30m

The flags to sendmail may need to be adjusted as required for the
local system configuration.

VI.   Correction details

The following is the sendmail $Id$ revision number of the file that
was corrected for the supported branches of FreeBSD.  The $Id$
revision number of the installed source can be examined using the
ident(1) command.

  Revision   Path
  8.20.22.4  src/contrib/sendmail/src/trace.c

VII.  References

<URL:http://www.securityfocus.com/bid/3163>

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