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Category:   OS (UNIX)  >   NetBSD Vendors:   NetBSD
NetBSD fast_ipsec() Endian Order Lets Remote Users Bypass IPSec Policy Restrictions
SecurityTracker Alert ID:  1019533
SecurityTracker URL:  http://securitytracker.com/id/1019533
CVE Reference:   CVE-2008-1335   (Links to External Site)
Updated:  Mar 19 2008
Original Entry Date:  Feb 29 2008
Impact:   Host/resource access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.0, 2.1, 3.0, and 3.1
Description:   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.

Impact:   A remote user can bypass IPSec policy that is based on protocol and port number parameters.
Solution:   NetBSD has issued a fix.

The NetBSD advisory is available at:

ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2008-002.txt.asc

Vendor URL:  ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2008-002.txt.asc (Links to External Site)
Cause:   Access control error

Message History:   None.


 Source Message Contents

Subject:  NetBSD Security Advisory 2008-002: Endianness issue in fast_ipsec(4)


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


		 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


Abstract
========

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 \
		sys/netipsec/ipsec_osdep.h
	# ./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:

   http://www.NetBSD.org/guide/en/chap-kernel.html


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 
  ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2008-002.txt.asc

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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