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AUSCERT External Security Bulletin Redistribution
ESB-2008.0224 -- [NetBSD]
Endianness issue in fast_ipsec(4)
29 February 2008
AusCERT Security Bulletin Summary
Operating System: NetBSD
Impact: Reduced Security
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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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