![[LWN Logo]](/images/lcorner.png) |
|
![[LWN.net]](/images/Included.png) |
From: Kurt Seifried <seifried@SECURITYPORTAL.COM>
To: LINUX-SECURITY@LISTSERV.SECURITYPORTAL.COM
Subject: LSLID:2001051504 - Progeny - Kernel (netfilter) -
PROGENY-SA-2001-15
Date: Tue, 15 May 2001 15:28:48 -0600
LSLID:2001051504
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
---------------------------------------------------------------------------
PROGENY SERVICE NETWORK -- SECURITY ADVISORY PROGENY-SA-2001-15
---------------------------------------------------------------------------
Synopsis: netfilter ftp connection tracking security flaw
Software: kernel-image-2.4.2
History:
2001-04-16 Vulnerability announced
2001-04-16 Vendor patch/fix available
2001-05-11 Update available in Progeny archive
2001-05-15 Advisory released
Credits: Cristiano Lincoln Mattos <lincoln@cesar.org.br>
Affects: Progeny Debian (kernel-image-2.4.2 prior to 0.05)
Progeny Only: NO
Vendor-Status: New Version Released (kernel-image-2.4.2_0.05)
$Progeny: security/advisory/PROGENY-SA-2001-15,v 1.2 2001/05/15 21:13:28
jdaily Exp $
---------------------------------------------------------------------------
SUMMARY
The linux 2.4.x firewalling code, netfilter, contains a vulnerability
whereby an attacker can bypass firewall rules.
DETAILED DESCRIPTION
The netfilter code in the released versions of the 2.4.x linux kernel
allows an attacker to exploit the ip_conntrack_ftp (stateful inspection
of ftp traffic) module to insert rules into the RELATED ruleset.
The ip_conntrack_ftp module does not validate parameters passed to it in
an ftp PORT command when automatically adding a rule to the RELATED
ruleset. As such, an attacker that can establish an ftp connection
through the firewall is able to bypass the firewall's rules and connect
to arbitrary hosts and ports.
More details and an exploit can be found at
http://www.tempest.com.br/advisories/01-2001.html
IMPACT
Progeny Debian 1.0 does not install a 2.4 kernel by default. The 2.4.2
kernel that ships with Progeny Debian 1.0 does have a vulnerable
ip_conntrack_ftp module, but does not automatically enable any firewall
rules.
On firewall systems that run 2.4.x kernels and have enabled rules that
utilize the ip_conntrack_ftp module, an attacker could insert rules to
the RELATED ruleset and gain access to machines behind a firewall that
they normally would not be able to access.
SOLUTION (See also: UPDATING VIA APT-GET)
Upgrade to a version of the 2.4.x linux kernel with the security fix
applied. For your convenience, you may upgrade to the
kernel-image-2.4.2_0.05 package.
UPDATING VIA APT-GET
1. Ensure that your /etc/apt/sources.list file has a URI for Progeny's
update repository:
deb http://archive.progeny.com/progeny updates/newton/
2. Update your cache of available packages for apt(8).
Example:
# apt-get update
3. Using apt(8), install the new package. apt(8) will download the
update, verify its integrity with md5, and then install the
package on your system with dpkg(8).
Example:
# apt-get install kernel-image-2.4.2
UPDATING VIA DPKG
1. Use your preferred FTP/HTTP client to retrieve the following
updated files from Progeny's update archive at:
http://archive.progeny.com/progeny/updates/newton/
MD5 Checksum Filename
-------------------------------- -------------------------------------
0c3ad9bc6dbfa8c099549bdf596ad295 kernel-image-2.4.2_0.05_i386.deb
Example:
$ wget \
http://archive.progeny.com/progeny/updates/newton/kernel-image-2.4.2_0.05_i386
.deb
2. Use the md5sum(1) command on the retrieved files to verify that
they match the MD5 checksum provided in this advisory:
Example:
$ md5sum kernel-image-2.4.2_0.05_i386.deb
3. Then install the replacement package(s) using dpkg(8).
Example:
# dpkg --install kernel-image-2.4.2_0.05_i386.deb
WORKAROUND
As an alternative to the above solution, disable stateful inspection
of ftp traffic by removing the lines that load the ip_conntrack_ftp
module from your firewall's rule scripts. Passive ftp should not be
impacted, but other ftp connections will no longer work.
MORE INFORMATION
Some Cisco equipment has been reported to depend on the behavior that
this advisory details as a security vulnerability. The solution
mentioned above may cause problems if you are depending on netfilter to
allow for this behavior.
Progeny advisories can be found at http://www.progeny.com/security/.
---------------------------------------------------------------------------
pub 1024D/F92D4D1F 2001-04-04 Progeny Security Team <security@progeny.com>
- -----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.0.4 (GNU/Linux)
Comment: For info see http://www.gnupg.org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=6dRm
- -----END PGP PUBLIC KEY BLOCK-----
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.4 (GNU/Linux)
Comment: For info see http://www.gnupg.org
iEYEARECAAYFAjsBnGQACgkQScF9I/ktTR8jGQCfdiym4ndMCjFUcqdofadoDhEA
8oQAni9U2TONge8ZEH8NAAay6XVC3Lyv
=I9aU
-----END PGP SIGNATURE-----