[ GLSA 200507-20 ] Shorewall: Security policy bypass

[GLSA]

Gentoo Linux Security Advisory

Title: Shorewall: Security policy bypass (GLSA 200507-20)
Severity: low
Exploitable: remote
Date: July 22, 2005
Updated: September 14, 2005
Bug(s): #99398
ID: 200507-20

Synopsis


A vulnerability in Shorewall allows clients authenticated by MAC address
filtering to bypass all other security rules.


Background


Shorewall is a high level tool for configuring Netfilter, the firewall
facility included in the Linux Kernel.


Affected Packages

Package: net-firewall/shorewall
Vulnerable: <= 2.4.1
Unaffected: >= 2.4.2
Architectures: All supported architectures


Description


Shorewall fails to enforce security policies if configured with
"MACLIST_DISPOSITION" set to "ACCEPT" or "MACLIST_TTL" set to a value
greater or equal to 0.


Impact


A client authenticated by MAC address filtering could bypass all
security policies, possibly allowing him to gain access to restricted
services. The default installation has MACLIST_DISPOSITION=REJECT and
MACLIST_TTL=(blank) (equivalent to 0). This can be checked by looking
at the settings in /etc/shorewall/shorewall.conf


Workaround


Set "MACLIST_TTL" to "0" and "MACLIST_DISPOSITION" to "REJECT" in the
Shorewall configuration file (usually /etc/shorewall/shorewall.conf).


Resolution


All Shorewall users should upgrade to the latest available version: