NetBSD fast_ipsec() Endian Order Lets Remote Users Bypass IPSec Policy Restrictions
SecurityTracker Alert ID: 1019533|
SecurityTracker URL: http://securitytracker.com/id/1019533
(Links to External Site)
Updated: Mar 19 2008|
Original Entry Date: Feb 29 2008
Host/resource access via network|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): 2.0, 2.1, 3.0, and 3.1|
A vulnerability was reported in NetBSD in the IPSec implementation. A remote user can bypass security restrictions.|
A remote user can bypass IPSec policy by establishing a security association using a different byte order than the target NetBSD system (which assumes host endian order).
The vulnerability resides in the fast_ipsec(4) ipsec4_get_ulp() function.
Kernels compiled with the 'options FAST_IPSEC' option are affected.
Karl Knutsson reported this vulnerability.
A remote user can bypass IPSec policy that is based on protocol and port number parameters.|
NetBSD has issued a fix.|
The NetBSD advisory is available at:
Vendor URL: ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2008-002.txt.asc (Links to External Site)
Access control error|
Source Message Contents
Subject: NetBSD Security Advisory 2008-002: Endianness issue in fast_ipsec(4)|
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NetBSD Security Advisory 2008-002
Topic: Endianness issue in fast_ipsec(4)
Version: NetBSD-current: affected
NetBSD 4.0: not affected
NetBSD 3.1: affected
NetBSD 3.0.*: affected
NetBSD 3.0: affected
NetBSD 2.1: affected
NetBSD 2.0.*: affected
NetBSD 2.0: affected
Severity: IPSEC Security bypass
Fixed: NetBSD-current: October 28, 2007
NetBSD-3-1 branch: November 22, 2007
(3.1.2 will include the fix)
NetBSD-3-0 branch: November 22, 2007
(3.0.4 will include the fix)
NetBSD-3 branch: November 22, 2007
(3.2 will include the fix)
NetBSD-2-1 branch: December 01, 2007
NetBSD-2-0 branch: December 01, 2007
NetBSD-2 branch: December 01, 2007
If a IPsec association is made between two hosts with different byte orders
it is possible to bypass the IPsec policy. It is possible for this situation
to occur if a NetBSD system is just one host, or both hosts, involved in the
The function ipsec4_get_ulp() assumes that ip_off is host endian. This
means that IPsec processing, that is dependent on protocol and/or port number,
can be bypassed.
Solutions and Workarounds
Only kernels compiled with the following option are vulnerable to this issue:
As a temporary workaround recompile the kernel with the above option
commented out. The default NetBSD GENERIC kernels (with the exception
of GENERIC.FAST_IPSEC) do not have this option enabled.
For all NetBSD versions, you need to obtain fixed kernel sources,
rebuild and install the new kernel, and reboot the system.
The fixed source may be obtained from the NetBSD CVS repository.
The following instructions briefly summarise how to upgrade your
kernel. In these instructions, replace:
ARCH with your architecture (from uname -m), and
KERNCONF with the name of your kernel configuration file.
To update from CVS, re-build, and re-install the kernel:
# cd src
# cvs update sys/netipsec/xform_ah.c \
# ./build.sh kernel=KERNCONF
# mv /netbsd /netbsd.old
# cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd
# shutdown -r now
For more information on how to do this, see:
Karl Knutsson for reporting this issue and supplying an initial fix.
Arnaud Degroote for coming up with a final patch.
2008-02-28 Initial release
Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at
Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/.
Copyright 2008, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2008-002.txt,v 1.3 2008/02/28 19:27:42 adrianp Exp $
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