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FreeBSD-SA-06:08.ppp Security Advisory
The FreeBSD Project

Topic: Buffer overflow in sppp(4)

Category: core
Module: sys_net
Announced: 2006-08-23
Credits: Martin Husemann, Pavel Cahyna
Affects: All FreeBSD releases.
Corrected: 2006-08-23 22:01:44 UTC (RELENG_6, 6.1-STABLE)
2006-08-23 22:02:25 UTC (RELENG_6_1, 6.1-RELEASE-p4)
2006-08-23 22:02:52 UTC (RELENG_6_0, 6.0-RELEASE-p10)
2006-08-23 22:03:55 UTC (RELENG_5, 5.5-STABLE)
2006-08-23 22:04:28 UTC (RELENG_5_5, 5.5-RELEASE-p3)
2006-08-23 22:04:58 UTC (RELENG_5_4, 5.4-RELEASE-p17)
2006-08-23 22:05:49 UTC (RELENG_5_3, 5.3-RELEASE-p32)
2006-08-23 22:06:08 UTC (RELENG_4, 4.11-STABLE)
2006-08-23 22:06:40 UTC (RELENG_4_11, 4.11-RELEASE-p20)
CVE Name: CVE-2006-4304

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/&gt;.

0. Revision History

v1.0 2006-08-23 Initial release.
v1.1 2006-08-25 Corrected name of affected driver.

NOTE WELL: The original version of this advisory identified the affected
driver as ppp(4). This is incorrect; the problem occurs in the sppp(4)
driver instead.

I. Background

The sppp(4) driver implements the state machine and the Link Control
Protocol (LCP) of the Point-to-Point Protocol (PPP) and is used in
combination with underlying drivers which provide synchronous
point-to-point connections. In particular, sppp(4) is commonly used
with i4bisppp(4) and ng_sppp(4).

II. Problem Description

While processing Link Control Protocol (LCP) configuration options received
from the remote host, sppp(4) fails to correctly validate option lengths.
This may result in data being read or written beyond the allocated kernel
memory buffer.

III. Impact

An attacker able to send LCP packets, including the remote end of a sppp(4)
connection, can cause the FreeBSD kernel to panic. Such an attacker may
also be able to obtain sensitive information or gain elevated privileges.

IV. Workaround

No workaround is available, but systems which do not use sppp(4) are not
vulnerable.

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_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, RELENG_5_3,
or RELENG_4_11 security branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.11, 5.3,
5.4, 5.5, 6.0, and 6.1 systems.

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

[FreeBSD 4.x]

fetch http://security.FreeBSD.org/patches/SA-06:18/ppp4x.patch

fetch http://security.FreeBSD.org/patches/SA-06:18/ppp4x.patch.asc

[FreeBSD 5.3]

fetch http://security.FreeBSD.org/patches/SA-06:18/ppp53.patch

fetch http://security.FreeBSD.org/patches/SA-06:18/ppp53.patch.asc

[FreeBSD 5.4, 5.5, and 6.x]

fetch http://security.FreeBSD.org/patches/SA-06:18/ppp.patch

fetch http://security.FreeBSD.org/patches/SA-06:18/ppp.patch.asc

b) Apply the patch.

cd /usr/src

patch < /path/to/patch

c) Recompile your kernel as described in
<URL:http://www.freebsd.org/handbook/kernelconfig.html&gt; and reboot the
system.

VI. Correction details

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

Branch Revision
Path

---

RELENG_4
src/sys/net/if_spppsubr.c 1.59.2.15
RELENG_4_11
src/UPDATING 1.73.2.91.2.21
src/sys/conf/newvers.sh 1.44.2.39.2.24
src/sys/net/if_spppsubr.c 1.59.2.13.10.1
RELENG_5
src/sys/net/if_spppsubr.c 1.113.2.3
RELENG_5_5
src/UPDATING 1.342.2.35.2.3
src/sys/conf/newvers.sh 1.62.2.21.2.5
src/sys/net/if_spppsubr.c 1.113.2.2.4.1
RELENG_5_4
src/UPDATING 1.342.2.24.2.26
src/sys/conf/newvers.sh 1.62.2.18.2.22
src/sys/net/if_spppsubr.c 1.113.2.2.2.1
RELENG_5_3
src/UPDATING 1.342.2.13.2.35
src/sys/conf/newvers.sh 1.62.2.15.2.37
src/sys/net/if_spppsubr.c 1.113.2.1.2.1
RELENG_6
src/sys/net/if_spppsubr.c 1.119.2.3
RELENG_6_1
src/UPDATING 1.416.2.22.2.6
src/sys/conf/newvers.sh 1.69.2.11.2.6
src/sys/net/if_spppsubr.c 1.119.2.2.2.1
RELENG_6_0
src/UPDATING 1.416.2.3.2.15
src/sys/conf/newvers.sh 1.69.2.8.2.11
src/sys/net/if_spppsubr.c 1.119.2.1.2.1

---

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4304

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-06:18.ppp.asc
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