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                 NetBSD Security Advisory 2002-016
                 =================================

Topic: Insufficient length check in ESP authentication data

Version: NetBSD-current: source prior to August 23, 2002
                NetBSD-1.6 beta: source prior to August 23, 2002
                NetBSD-1.5.3: affected
                NetBSD-1.5.2: affected
                NetBSD-1.5.1: affected
                NetBSD-1.5: affected
                NetBSD-1.4.*: not affected (no IPsec shipped with it)

Severity: remote denial of service (kernel panic by malicious packet)

Fixed: NetBSD-current: August 23, 2002
                NetBSD-1.6 branch: August 23, 2002 (1.6 includes the fix)
                NetBSD-1.5 branch: September 5, 2002

Abstract
========

The KAME-based IPsec implementation included in NetBSD was missing
some packet length checks, and could be tricked into passing negative
value as buffer length. By transmiting a specially-formed (very
short) ESP packet, a malicious sender can cause a cause kernel panic
on the victim node.

For the attack to be effective the attacker has to have knowledge of
the ESP settings being used by the victim node (wiretapping traffic
would achieve this). Also victim node has to be configured with
certain ESP security-association (SA).

The publication of this advisory is delayed to coordinate with third parties.

Technical Details
=================

http://www.kb.cert.org/vuls/id/459371

Your system is not vulnerable if:
 - you do not enable IPsec ESP in the kernel (options IPSEC_ESP), or
 - you do not have IPsec ESP SA with ESP authentication data setting
   active on your system. However, if you have IPSEC_ESP enabled, we
   suggest upgrading your kernel to bring in the fix, even if you are
   not presently using IPSec.

Solutions and Workarounds
=========================

The recent NetBSD 1.6 release is not vulnerable to this issue. A full
upgrade to NetBSD 1.6 is the recommended resolution for all users able
to do so. Many security-related improvements have been made, and
indeed this release has been delayed several times in order to include
fixes for a number of recent issues.

If you are using ESP with authentication, you must upgrade to avoid
the vulnerability, as described below for your version of NetBSD:

* NetBSD-current:

        Systems running NetBSD-current dated from before 2002-08-23
        should be upgraded to NetBSD-current dated 2002-08-23 or later.

        The kernel code needs to be updated from the netbsd-1-6 CVS branch.

        To update from CVS:
                # cd src
                # cvs update -d -P sys

        See http://www.netbsd.org/Documentation/kernel/#how_to_build_a_kernel
        on how you rebuild the kernel.

* NetBSD 1.6 betas:

        Systems running NetBSD 1.6 BETAs and Release Candidates should
        be upgraded to the NetBSD 1.6 release.

        If a source-based point upgrade is required, sources from the
        NetBSD 1.6 branch dated 2002-08-23 or later should be used.

        The kernel code needs to be updated from the netbsd-1-6 CVS branch.

        To update from CVS:
                # cd src
                # cvs update -d -P -r netbsd-1-6 sys

        See http://www.netbsd.org/Documentation/kernel/#how_to_build_a_kernel
        for instructions on how you rebuild the kernel.

* NetBSD 1.5, 1.5.1, 1.5.2, 1.5.3:

        Systems running NetBSD 1.5 branch dated from before 2002-09-05
        should be upgraded to NetBSD 1.5 tree dated 2002-09-05 or later.

        The kernel code needs to be updated from the netbsd-1-5 CVS branch.

        To update from CVS:
                # cd src
                # cvs update -d -P -r netbsd-1-5 sys

        See http://www.netbsd.org/Documentation/kernel/#how_to_build_a_kernel
        for instructions on how you rebuild the kernel.

Thanks To
=========

Todd Sabin and BindView for analysis and report.

The NetBSD Release Engineering teams, for great patience and
assistance in dealing with repeated security issues discovered
recently.

Revision History
================

        2002-10-22 Initial release

More Information
================

An up-to-date PGP signed copy of this release will be maintained at
  ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2002-016.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/.

Copyright 2002, The NetBSD Foundation, Inc. All Rights Reserved.

$NetBSD: NetBSD-SA2002-016.txt,v 1.16 2002/10/22 00:27:56 itojun Exp $

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