Gentoo: Shorewall Security policy bypass
Posted by Benjamin D. Thomas   
Gentoo A vulnerability in Shorewall allows clients authenticated by MAC address filtering to bypass all other security rules.
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Gentoo Linux Security Advisory [ERRATA UPDATE]        GLSA 200507-20:02
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                                            http://security.gentoo.org/
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  Severity: Low
     Title: Shorewall: Security policy bypass
      Date: July 22, 2005
   Updated: September 14, 2005
      Bugs: #99398
        ID: 200507-20:02

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Errata
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The "unaffected" version was incorrectly set to 2.4.1 in the initial
advisory, the correct "unaffected" version is 2.4.2.

The corrected sections appear below.

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

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

Affected packages
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    -------------------------------------------------------------------
     Package                 /  Vulnerable  /               Unaffected
    -------------------------------------------------------------------
  1  net-firewall/shorewall      <=3D 2.4.1                     >=3D 2.4=
=2E2

Description
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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
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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=3DREJECT and
MACLIST_TTL=3D(blank) (equivalent to 0). This can be checked by looking
at the settings in /etc/shorewall/shorewall.conf

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

Resolution
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All Shorewall users should upgrade to the latest available version:

    # emerge --sync
    # emerge --ask --oneshot --verbose net-firewall/shorewall

References
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  [ 1 ] CAN-2005-2317
        http://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCAN-2005-2317
  [ 2 ] Shorewall Announcement
        http://www.shorewall.net/News.htm#20050717

Availability
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This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

  http://security.gentoo.org/glsa/glsa-200507-20.xml

Concerns?
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Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
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Copyright 2005 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

http://creativecommons.org/licenses/by-sa/2.0