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FreeBSD-SA-03:04.sendmail                                   Security Advisory
                                                          The FreeBSD Project

Topic:          sendmail header parsing buffer overflow

Category:       contrib
Module:         contrib_sendmail
Announced:      2003-03-03
Credits:        Mark Dowd (ISS)
Affects:        All releases prior to 4.8-RELEASE and 5.0-RELEASE-p4
                FreeBSD 4-STABLE prior to the correction date
Corrected:      2003-03-03
FreeBSD only:   NO

I.   Background

FreeBSD includes sendmail(8), a general purpose internetwork mail
routing facility, as the default Mail Transfer Agent (MTA).

II.  Problem Description

ISS has identified a buffer overflow that may occur during header
parsing in all versions of sendmail after version 5.79.

In addition, Sendmail, Inc. has identified and corrected a defect in
buffer handling within sendmail's RFC 1413 ident protocol support.

III. Impact

A remote attacker could create a specially crafted message that may
cause sendmail to execute arbitrary code with the privileges of the
user running sendmail, typically root.  The malicious message might be
handled (and therefore the vulnerability triggered) by the initial
sendmail MTA, any relaying sendmail MTA, or by the delivering sendmail
process.  Exploiting this defect is particularly difficult, but is
believed to be possible.

The defect in the ident routines is not believed to be exploitable.

IV.  Workaround

There is no workaround, other than disabling sendmail.

V.   Solution

Do one of the following:

1) Upgrade your vulnerable system to 4-STABLE; or to the RELENG_5_0,
RELENG_4_7, or RELENG_4_6 security branch dated after the correction
date (5.0-RELEASE-p4, 4.7-RELEASE-p7, or 4.6.2-RELEASE-p10,
respectively).

[NOTE: At the time of this writing, the FreeBSD 4-STABLE branch is
 labeled `4.8-RC1'.]

2) To patch your present system:

The following patch has been verified to apply to FreeBSD 5.0, 4.7,
and 4.6 systems.

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

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail.patch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libsm
# make obj && make depend && make
# cd /usr/src/lib/libsmutil
# make obj && make depend && make
# cd /usr/src/usr.sbin/sendmail
# make obj && make depend && make && make install

3) For i386 systems only, a patched sendmail binary is available.
Select the correct binary based on your FreeBSD version and whether or
not you want STARTTLS support.  If you want STARTTLS support, you must
have the crypto distribution installed.

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

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.6-i386-crypto.bin.gz
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.6-i386-crypto.bin.gz.asc

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.6-i386-nocrypto.bin.gz
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.6-i386-nocrypto.bin.gz.asc

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.7-i386-crypto.bin.gz
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.7-i386-crypto.bin.gz.asc

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.7-i386-nocrypto.bin.gz
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-4.7-i386-nocrypto.bin.gz.asc

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-5.0-i386-crypto.bin.gz
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-5.0-i386-crypto.bin.gz.asc

ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-5.0-i386-nocrypto.bin.gz
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:04/sendmail-5.0-i386-nocrypto.bin.gz.asc

b) Install the binary.  Execute the following commands as root.
Note that these examples utilizes the FreeBSD 4.7 crypto binary.
Substitute BINARYGZ with the file name which you downloaded in
step (a).

# BINARYGZ=/path/to/sendmail-4.7-i386-crypto.bin.gz
# gunzip ${BINARYGZ}
# install -s -o root -g smmsp -m 2555 ${BINARYGZ%.gz} /usr/libexec/sendmail/sendmail

c) Restart sendmail.  Execute the following command as root.

# /bin/sh /etc/rc.sendmail restart

VI.  Correction details

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

Path                                                             Revision
  Branch
- -------------------------------------------------------------------------
src/contrib/src/sendmail.h
src/contrib/sendmail/src/daemon.c
src/contrib/sendmail/src/headers.c
src/contrib/sendmail/src/main.c
src/contrib/sendmail/src/parseaddr.c
- -------------------------------------------------------------------------

VII. References

<URL: http://www.kb.cert.org/vuls/id/398025 >
<URL: http://www.iss.net/issEn/delivery/xforce/alertdetail.jsp?oid=21950 >
<URL: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-1337 >
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