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Home » Hacking News » NetBSD Security Advisory 2002-024: IPFilter FTP proxy

NetBSD Security Advisory 2002-024: IPFilter FTP proxy

by Nikola Strahija on November 9th, 2002 Version: NetBSD-current: source prior to September 20, 2002 NetBSD 1.6: affected NetBSD-1.5.3: affected NetBSD-1.5.2: affected NetBSD-1.5.1: affected NetBSD-1.5: affected


Abstract
========

FTP proxy module in IPFilter package may not adequately maintain the
state of FTP commands and responses. As a result, an attacker could
establish arbitrary TCP connections to FTP servers or clients located
behind a vulnerable firewall.


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

http://www.kb.cert.org/vuls/id/328867


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

The IPFilter package, which is shipped with NetBSD, prior to 3.4.29
includes the vulnerable FTP proxy module.

Systems enabling both IPFilter and its FTP module are vulnerable.
IPFilter and the FTP proxy module are not enabled by default.
Therefore, the default installation of NetBSD is not vulnerable to
this attack.

Quick workaround:
Disable FTP proxy module in IP NAT configuration file by removing
or commenting out the line which includes both "proxy" and "ftp/".
The default location of the configuration file is /etc/ipnat.conf.

Solution:
Upgrade of the kernel as well as IPFilter-related userland tools.

The following instructions describe how to upgrade your kernel and IPFilter-
related binaries by updating your source tree and rebuilding and
installing a new version.

* NetBSD-current:

Systems running NetBSD-current dated from before 2002-09-20
should be upgraded to NetBSD-current dated 2002-09-20 or later.

The following directories need to be updated from the
netbsd-current CVS branch (aka HEAD):
dist/ipf
regress/sys/kern/ipf
sys/lkm/netinet/if_ipl
sys/netinet
usr.sbin/ipf

Update the source files:
# cd src
# cvs update -d -P dist/ipf
# cvs update -d -P regress/sys/kern/ipf
# cvs update -d -P sys/lkm/netinet/if_ipl
# cvs update -d -P sys/netinet
# cvs update -d -P usr.sbin/ipf

Install the updated include files:
# cd src/sys
# make includes

Rebuild the userland tools:
# cd src/usr.sbin/ipf
# make cleandir dependall
# make install

Rebuild the LKM:
# cd src/sys/lkm/netinet
# make cleandir dependall
# make install

Rebuild the kernel and reboot:
# cd src/sys/ARCH/conf
# config FILENAME
# cd ../compile/FILENAME
# make dependall install


* NetBSD 1.6:

Systems running NetBSD 1.6 dated from before 2002-10-25
should be upgraded to NetBSD 1.6 dated 2002-10-25 or later.

The following directories need to be updated from the
netbsd-1-6 CVS branch:
dist/ipf
regress/sys/kern/ipf
sys/lkm/netinet/if_ipl
sys/netinet
usr.sbin/ipf

Update the source files:
# cd src
# cvs update -d -P -r netbsd-1-6 dist/ipf
# cvs update -d -P -r netbsd-1-6 regress/sys/kern/ipf
# cvs update -d -P -r netbsd-1-6 sys/lkm/netinet/if_ipl
# cvs update -d -P -r netbsd-1-6 sys/netinet
# cvs update -d -P -r netbsd-1-6 usr.sbin/ipf

Install the updated include files:
# cd src/sys
# make includes

Rebuild the userland tools:
# cd src/usr.sbin/ipf
# make cleandir dependall
# make install

Rebuild the LKM:
# cd src/sys/lkm/netinet
# make cleandir dependall
# make install

Rebuild the kernel and reboot:
# cd src/sys/ARCH/conf
# config FILENAME
# cd ../compile/FILENAME
# make dependall install


* NetBSD 1.5, 1.5.1, 1.5.2, 1.5.3:

Systems running NetBSD 1.5 dated from before 2002-10-19
should be upgraded to NetBSD 1.5 dated 2002-10-19 or later.

The following directories need to be updated from the
netbsd-1-5 CVS branch:
dist/ipf
sys/netinet
usr.sbin/ipf

Update the source files:
# cd src
# cvs update -d -P -r netbsd-1-5 dist/ipf
# cvs update -d -P -r netbsd-1-5 usr.sbin/ipf
# cvs update -d -P -r netbsd-1-5 sys/netinet

Install the updated include files:
# cd src/sys
# make includes

Rebuild the userland tools:
# cd src/usr.sbin/ipf
# make cleandir dependall
# make install

Rebuild the LKM:
# cd src/sys/lkm/netinet
# make cleandir dependall
# make install

Rebuild the kernel and reboot:
# cd src/sys/ARCH/conf
# config FILENAME
# cd ../compile/FILENAME
# make dependall install


Thanks To
=========

Darren Reed
Martti Kuparinen

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

2002-11-04 Initial release


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

Advisories may be updated as new information comes to hand. The most
recent version of this advisory (PGP signed) can be found at
ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2002-024.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-SA2002-024.txt,v 1.15 2002/11/04 23:10:47 itojun Exp $


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