(Conectiva Issues Fix) Squid Proxy Cache '%00' URL Character Access Control Bug May Let Remote Users Bypass Certain Access Controls
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SecurityTracker Alert ID: 1009742 |
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SecurityTracker URL: http://securitytracker.com/id/1009742
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CVE Reference:
CAN-2004-0189
(Links to External Site)
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Date: Apr 13 2004
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Impact:
Host/resource access via network
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Fix Available: Yes Vendor Confirmed: Yes
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Version(s): Squid-2.x up to and including 2.5.STABLE4
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Description:
A vulnerability was reported in the Squid Proxy Cache server in the processing of URLs containing '%00'. A remote user may be able to bypass certain access controls.
It is reported that a flaw in the '%xx' URL decoding function may allow a remote user to bypass access controls that use 'url_regex' access control list (ACL) types. The report indicates that Squid will insert a NUL character in place of '%00' in a URL before analyzing the URL for access control purposes. As a result, the 'http://foo%00@www.example.com/' URL will not be properly detected as a URL to be denied in accordance with the following type of access control configuration:
acl BadSite url_regex www\.example\.com
http_access deny BadSite
In this example, Squid will attempt to compare 'http://foo' with 'www\.example\.com' and will not find a match, so the URL will not be denied.
Mitch Adair is credited with reporting this flaw.
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Impact:
A remote user may be able to submit a specially crafted URL to bypass url_regex access controls.
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Solution:
Conectiva has released a fix.
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-auth-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-doc-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-templates-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/SRPMS/squid-2.4.7-1U80_4cl.src.rpm
ftp://atualizacoes.conectiva.com.br/9/RPMS/squid-2.5.5-25761U90_3cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/9/RPMS/squid-auth-2.5.5-25761U90_3cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/9/RPMS/squid-extra-templates-2.5.5-25761U90_3cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/9/SRPMS/squid-2.5.5-25761U90_3cl.src.rpm
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Vendor URL: www.squid-cache.org/Advisories/SQUID-2004_1.txt (Links to External Site)
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Cause:
Access control error
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Underlying OS:
Linux (Conectiva)
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Message History:
This archive entry is a follow-up to the message listed below.
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Source Message Contents
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Date: Mon, 12 Apr 2004 17:19:30 -0300
Subject: [conectiva-updates] [CLA-2004:838] Conectiva Security Announcement - squid
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
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CONECTIVA LINUX SECURITY ANNOUNCEMENT
- --------------------------------------------------------------------------
PACKAGE : squid
SUMMARY : ACL bypass vulnerability
DATE : 2004-04-12 17:17:00
ID : CLA-2004:838
RELEVANT
RELEASES : 8, 9
- -------------------------------------------------------------------------
DESCRIPTION
Squid is a full-featured web proxy cache.
Squid uses Access Control Lists (ACLs) to restrict access to sites or
users according to certain rules. This update fixes a
vulnerability[1] that allows a malicious user to bypass url_regex
ACLs by using a specially crafted URL containing the characters
'%00'. When interpreted by squid, only part of such a URL is
considered, potentially allowing the client to access prohibited
sites.
The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2004-0189 to this issue[2].
Additionally, the packages for Conectiva Linux 9 are being updated to
the latest stable squid version (2.5STABLE5), which includes several
other fixes and improvements. One of the most notorious improvements
is the inclusion of a new Access Control type called "urllogin". This
new configuration directive (which is not enabled by default) can be
used to protect vulnerable[3,4,5] Microsoft Internet Explorer(TM)
clients from accessing some malicious and specially crafted URLs.
SOLUTION
It is recommended that all squid users upgrade to the latest
packages. This update will automatically restart the service if it is
already running.
REFERENCES:
1.http://www.squid-cache.org/Advisories/SQUID-2004_1.txt
2.http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0189
3.http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-1025
4.http://www.kb.cert.org/vuls/id/652278
5.http://www.microsoft.com/security/incident/spoof.asp
UPDATED PACKAGES
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-auth-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-doc-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/squid-templates-2.4.7-1U80_4cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/SRPMS/squid-2.4.7-1U80_4cl.src.rpm
ftp://atualizacoes.conectiva.com.br/9/RPMS/squid-2.5.5-25761U90_3cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/9/RPMS/squid-auth-2.5.5-25761U90_3cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/9/RPMS/squid-extra-templates-2.5.5-25761U90_3cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/9/SRPMS/squid-2.5.5-25761U90_3cl.src.rpm
ADDITIONAL INSTRUCTIONS
The apt tool can be used to perform RPM packages upgrades:
- run: apt-get update
- after that, execute: apt-get upgrade
Detailed instructions regarding the use of apt and upgrade examples
can be found at http://distro.conectiva.com.br/atualizacoes/#apt?idioma=en
- -------------------------------------------------------------------------
All packages are signed with Conectiva's GPG key. The key and instructions
on how to import it can be found at
http://distro.conectiva.com.br/seguranca/chave/?idioma=en
Instructions on how to check the signatures of the RPM packages can be
found at http://distro.conectiva.com.br/seguranca/politica/?idioma=en
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All our advisories and generic update instructions can be viewed at
http://distro.conectiva.com.br/atualizacoes/?idioma=en
- -------------------------------------------------------------------------
Copyright (c) 2004 Conectiva Inc.
http://www.conectiva.com
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subscribe: conectiva-updates-subscribe@papaleguas.conectiva.com.br
unsubscribe: conectiva-updates-unsubscribe@papaleguas.conectiva.com.br
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