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FreeBSD Kernel Flaw in Checking Signal Numbers May Let Local Users Modify Kernel Memory or Crash the System
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SecurityTracker Alert ID: 1007459 |
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SecurityTracker URL: http://securitytracker.com/id/1007459
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CVE Reference:
GENERIC-MAP-NOMATCH
(Links to External Site)
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Date: Aug 11 2003
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Impact:
Denial of service via local system, Execution of arbitrary code via local system, Modification of system information, Root access via local system
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Fix Available: Yes Vendor Confirmed: Yes
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Version(s): 5.1 and prior
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Description:
A vulnerability was reported in the FreeBSD kernel in the checking of signal number values. A local user may be able to trigger a kernel panic. In some configurations, a local user may be able to modify kernel memory and take full control of the system.
It is reported that a local user can cause certain applications to send a negative or out-of-range signal number to the kernel. Those applications reportedly include the ptrace(2) system call and the 'spigot' video capture device driver.
The flaw in ptrace(2) was reportedly introduced into FreeBSD version 4.2. The vulnerable `spigot' device driver was reportedly introduced in FreeBSD 2.0.5, but is not part of the default kernel (only systems with 'device spigot' in the kernel configuration are affected).
According to the report, a local user can trigger an assertion failure and kernel panic.
On some FreeBSD 5.x systems (those where the 'INVARIANTS' kernel option is not used; including the default configuration of FreeBSD 5.0-RELEASE and 5.1-RELEASE), the assertion code is not included. As a result, a local user may be able to modify kernel memory.
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Impact:
A local user can cause the system to crash.
A local user may be able to modify kernel memory on certain kernel configurations.
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Solution:
The vendor has released a fix and recommends that you upgrade your system to 4.8-STABLE, or to any of the RELENG_4_8 (4.8-RELEASE-p2), RELENG_4_7 (4.7-RELEASE-p12), or RELENG_5_1 (5.1-RELEASE-p1) security branches dated after the respective correction dates [see the Source Message for the correction dates].
Alternately, you can download the following patch:
[FreeBSD 5.1-RELEASE]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal51.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal51.patch.asc
[FreeBSD 5.0-RELEASE]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal50.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal50.patch.asc
[FreeBSD 4.8-RELEASE, 4.8-STABLE, 4.7-STABLE dated Jan 2 20:39:13 2003 UTC or later]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal4s.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal4s.patch.asc
[FreeBSD 4.3-RELEASE through 4.7-RELEASE, 4.7-STABLE dated before Jan 2 20:39:13 2003 UTC]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal47.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal47.patch.asc
The patch can be applied with the following commands:
# cd /usr/src
# patch < /path/to/patch
After applying the patch, you must then recompile the kernel as described in <URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the system.
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Vendor URL: www.freebsd.org/security/ (Links to External Site)
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Cause:
Boundary error
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Underlying OS:
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Message History:
This archive entry has one or more follow-up message(s) listed below.
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Source Message Contents
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Date: Sun, 10 Aug 2003 19:57:06 -0700 (PDT)
Subject: FreeBSD Security Advisory FreeBSD-SA-03:09.signal
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
=============================================================================
FreeBSD-SA-03:09.signal Security Advisory
The FreeBSD Project
Topic: Insufficient range checking of signal numbers
Category: core
Module: sys
Announced: 2003-08-10
Affects: All releases of FreeBSD up to and including 4.8-RELEASE-p1,
5.1-RELEASE (but see `Problem Description' below)
FreeBSD 4-STABLE prior to the correction date
Corrected: 2003-08-10 23:09:28 UTC (RELENG_4)
2003-08-10 23:14:08 UTC (RELENG_5_1)
2003-08-10 23:17:48 UTC (RELENG_5_0)
2003-08-10 23:19:35 UTC (RELENG_4_8)
2003-08-10 23:20:30 UTC (RELENG_4_7)
2003-08-10 23:21:18 UTC (RELENG_4_6)
2003-08-10 23:22:19 UTC (RELENG_4_5)
2003-08-10 23:23:05 UTC (RELENG_4_4)
2003-08-10 23:23:56 UTC (RELENG_4_3)
FreeBSD only: YES
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
Signals are a UNIX mechanism for handling asynchronous events such as
pressing the terminal interrupt key (e.g. Ctrl-C), job control, memory
access violations, I/O completion, and many others. Each signal is
assigned a positive number. There are a number of mechanisms by which
a process may cause a signal to be sent, including using the kill(2)
system call or registering with certain device drivers.
II. Problem Description
Some mechanisms for causing a signal to be sent did not properly
validate the signal number, in some cases allowing the kernel to
attempt to deliver a negative or out-of-range signal number. Such
errors were present in the ptrace(2) system call and the `spigot'
video capture device driver.
The error in ptrace(2) was introduced in FreeBSD version 4.2-RELEASE
(4-STABLE dated Oct 26 04:34:41 2000 UTC).
The `spigot' device driver (including the error) was introduced in
FreeBSD 2.0.5. It has never been included in the kernel installed by
default, nor in the GENERIC kernel configuration. Only systems with
`device spigot' added to the kernel configuration are affected by this
instance of the error.
III. Impact
In most cases, attempted delivery of a negative or out-of-range signal
number will trigger an assertion failure and panic, thereby crashing
the system. A malicious local user could use this vulnerability
as a local denial-of-service attack.
However, in FreeBSD 5.x, the assertion code is not present if the
`INVARIANTS' kernel option is not used. In FreeBSD 5.0-RELEASE and
5.1-RELEASE, `INVARIANTS' is not enabled by default. In this
configuration, a malicious local user could use this vulnerability
to modify kernel memory, potentially leading to complete system
compromise. (FreeBSD 4.x is not vulnerable in this way.)
IV. Workaround
There is no workaround for the local denial-of-service attack.
The more severe impact, present only in FreeBSD 5.x systems, can be
avoided by uncommenting or adding the `INVARIANTS' line to your kernel
configuration:
options INVARIANTS #Enable calls of extra sanity checking
Recompile your kernel as described in
<URL:http://www.freebsd.org/handbook/kernelconfig.html>
and reboot the system.
NOTE WELL: This workaround is only for FreeBSD 5.x systems. This
workaround does not eliminate the possibility of a local
denial-of-service attack.
V. Solution
1) Upgrade your vulnerable system to 4.8-STABLE, or to any of the
RELENG_4_8 (4.8-RELEASE-p2), RELENG_4_7 (4.7-RELEASE-p12), or
RELENG_5_1 (5.1-RELEASE-p1) security branches dated after the
respective correction dates.
2) To patch your present system:
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
[FreeBSD 5.1-RELEASE]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal51.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal51.patch.asc
[FreeBSD 5.0-RELEASE]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal50.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal50.patch.asc
[FreeBSD 4.8-RELEASE, 4.8-STABLE, 4.7-STABLE dated Jan 2 20:39:13 2003 UTC
or later]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal4s.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal4s.patch.asc
[FreeBSD 4.3-RELEASE through 4.7-RELEASE, 4.7-STABLE dated before
Jan 2 20:39:13 2003 UTC]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal47.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:09/signal47.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>
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
- -------------------------------------------------------------------------
src/sys/UPDATING
RELENG_5_1 1.251.2.2
RELENG_5_0 1.229.2.15
RELENG_4_8 1.73.2.80.2.4
RELENG_4_7 1.73.2.74.2.15
RELENG_4_6 1.73.2.68.2.43
RELENG_4_5 1.73.2.50.2.45
RELENG_4_4 1.73.2.43.2.46
RELENG_4_3 1.73.2.28.2.33
src/sys/conf/newvers.sh
RELENG_5_1 1.50.2.3
RELENG_5_0 1.48.2.10
RELENG_4_8 1.44.2.29.2.3
RELENG_4_7 1.44.2.26.2.14
RELENG_4_6 1.44.2.23.2.32
RELENG_4_5 1.44.2.20.2.29
RELENG_4_4 1.44.2.17.2.37
RELENG_4_3 1.44.2.14.2.23
src/sys/i386/isa/spigot.c
RELENG_4 1.44.2.1
RELENG_5_1 1.58.2.1
RELENG_5_0 1.55.2.1
RELENG_4_8 1.44.14.1
RELENG_4_7 1.44.12.1
RELENG_4_6 1.44.10.1
RELENG_4_5 1.44.8.1
RELENG_4_4 1.44.6.1
RELENG_4_3 1.44.4.1
src/sys/kern/sys_process.c
RELENG_4 1.51.2.7
RELENG_5_1 1.108.2.1
RELENG_5_0 1.104.2.1
RELENG_4_8 1.51.2.6.2.1
RELENG_4_7 1.51.2.4.2.1
RELENG_4_6 1.51.2.3.4.1
RELENG_4_5 1.51.2.3.2.1
RELENG_4_4 1.51.2.1.4.2
RELENG_4_3 1.51.2.1.2.2
src/sys/kern_sig.c
RELENG_5_1 1.239.2.1
RELENG_5_0 1.197.2.1
- -------------------------------------------------------------------------
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.2 (FreeBSD)
iD8DBQE/Nt6VFdaIBMps37IRAs/0AJ9qtj0Cv+y3QjUZXrFDQx00oTv+AwCgnys1
p3OHIN16XjGz8OhmjF1nWKM=
=tnsF
-----END PGP SIGNATURE-----
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