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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
IPsec connection.

Technical Details

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:

        options FAST_IPSEC

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 \
                sys/netipsec/ipsec.c \
                sys/netipsec/xform_ipip.c \
                sys/netipsec/ipsec_output.c \
        # ./ 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:

Thanks To

Karl Knutsson for reporting this issue and supplying an initial fix.
Arnaud Degroote for coming up with a final patch.

Revision History

        2008-02-28      Initial release

More Information

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 and

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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