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Category: Application (Generic) > Squid

Vendors: Squid-cache.org

(Red Hat Issues Fix for RH Enterprise Linux) Squid Proxy Cache '%00' URL Character Access Control Bug May Let Remote Users Bypass Certain Access Controls

SecurityTracker Alert ID: 1009804

CVE Reference: CAN-2004-0189 (Links to External Site)

Date: Apr 15 2004

Impact: Host/resource access via network

Fix Available: Yes Vendor Confirmed: Yes

Version(s): Squid-2.x up to and including 2.5.STABLE4

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.

Impact: A remote user may be able to submit a specially crafted URL to bypass url_regex access controls.

Vendor URL: www.squid-cache.org/Advisories/SQUID-2004_1.txt (Links to External Site)

Cause: Access control error

Underlying OS: Linux (Red Hat Enterprise)

Underlying OS Comments: 2.1, 3

Reported By: bugzilla@redhat.com

Message History: This archive entry is a follow-up to the message listed below.

Mar 1 2004

Squid Proxy Cache '%00' URL Character Access Control Bug May Let Remote Users Bypass Certain Access Controls

Source Message Contents

Date: Wed, 14 Apr 2004 10:13 -0400
From: bugzilla@redhat.com
Subject: [RHSA-2004:133-01] Updated squid package fixes security

 

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

- ---------------------------------------------------------------------
                   Red Hat Security Advisory

Synopsis:          Updated squid package fixes security vulnerability
Advisory ID:       RHSA-2004:133-01
Issue date:        2004-04-14
Updated on:        2004-04-14
Product:           Red Hat Enterprise Linux
Keywords:          Phishing  Spoofing
Cross references:  
Obsoletes:         
CVE Names:         CAN-2004-0189
- ---------------------------------------------------------------------

1. Topic:

An updated squid package is avaliable that fixes a security vulnerability in
URL decoding and provides a new ACL type for protecting vulnerable clients.

2. Relevant releases/architectures:

Red Hat Enterprise Linux AS (Advanced Server) version 2.1 - i386, ia64
Red Hat Linux Advanced Workstation 2.1 - ia64
Red Hat Enterprise Linux ES version 2.1 - i386
Red Hat Enterprise Linux AS version 3 - i386, ia64, ppc, ppc64, s390, s390x, x86_64
Red Hat Enterprise Linux ES version 3 - i386
Red Hat Enterprise Linux WS version 3 - i386, ia64, x86_64

3. Problem description:

Squid is a full-featured Web proxy cache.

A bug was found in the processing of %-encoded characters in a URL in
versions of Squid 2.5.STABLE4 and earlier.  If a Squid configuration uses
Access Control Lists (ACLs), a remote attacker could create URLs that would
not be correctly tested against Squid's ACLs, potentially allowing clients
to access prohibited URLs.

Users of Squid should update to these erratum packages which are not
vulnerable to this issue.

In addition, these packages contain a new Access Control type, "urllogin",
which can be used to protect vulnerable Microsoft Internet Explorer clients
from accessing URLs that contain login information.  Such URLs are often
used by fraudsters to trick web users into revealing valuable personal data.

Note that the default Squid configuration does not make use of this new
access control type.  You must explicitly configure Squid with ACLs that
use this new type, in accordance with your own site policies.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade.  Only those
RPMs which are currently installed will be updated.  Those RPMs which are
not installed but included in the list will not be updated.  Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network.  Many
people find this an easier way to apply updates.  To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

If up2date fails to connect to Red Hat Network due to SSL
Certificate Errors, you need to install a version of the
up2date client with an updated certificate.  The latest version of
up2date is available from the Red Hat FTP site and may also be
downloaded directly from the RHN website:

https://rhn.redhat.com/help/latest-up2date.pxt

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):

118032 - CAN-2004-0189 Squid ACL bypass

6. RPMs required:

Red Hat Enterprise Linux AS (Advanced Server) version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1AS/en/os/SRPMS/squid-2.4.STABLE6-10.21as.src.rpm

i386:
Available from Red Hat Network: squid-2.4.STABLE6-10.21as.i386.rpm

ia64:
Available from Red Hat Network: squid-2.4.STABLE6-10.21as.ia64.rpm

Red Hat Linux Advanced Workstation 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1AW/en/os/SRPMS/squid-2.4.STABLE6-10.21as.src.rpm

ia64:
Available from Red Hat Network: squid-2.4.STABLE6-10.21as.ia64.rpm

Red Hat Enterprise Linux ES version 2.1:

SRPMS:
ftp://updates.redhat.com/enterprise/2.1ES/en/os/SRPMS/squid-2.4.STABLE6-10.21as.src.rpm

i386:
Available from Red Hat Network: squid-2.4.STABLE6-10.21as.i386.rpm

Red Hat Enterprise Linux AS version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3AS/en/os/SRPMS/squid-2.5.STABLE3-5.3E.src.rpm

i386:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.i386.rpm

ia64:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.ia64.rpm

ppc:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.ppc.rpm

ppc64:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.ppc64.rpm

s390:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.s390.rpm

s390x:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.s390x.rpm

x86_64:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.x86_64.rpm

Red Hat Enterprise Linux ES version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3ES/en/os/SRPMS/squid-2.5.STABLE3-5.3E.src.rpm

i386:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.i386.rpm

Red Hat Enterprise Linux WS version 3:

SRPMS:
ftp://updates.redhat.com/enterprise/3WS/en/os/SRPMS/squid-2.5.STABLE3-5.3E.src.rpm

i386:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.i386.rpm

ia64:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.ia64.rpm

x86_64:
Available from Red Hat Network: squid-2.5.STABLE3-5.3E.x86_64.rpm



7. Verification:

MD5 sum                          Package Name
- --------------------------------------------------------------------------

465f0c77fd485041607ffe5b65e3adfa 2.1AS/en/os/SRPMS/squid-2.4.STABLE6-10.21as.src.rpm
2f72879474d822e5ee35c6169f3d350d 2.1AS/en/os/i386/squid-2.4.STABLE6-10.21as.i386.rpm
a039857fa6ac4492986f508f0554c75b 2.1AS/en/os/ia64/squid-2.4.STABLE6-10.21as.ia64.rpm
465f0c77fd485041607ffe5b65e3adfa 2.1AW/en/os/SRPMS/squid-2.4.STABLE6-10.21as.src.rpm
a039857fa6ac4492986f508f0554c75b 2.1AW/en/os/ia64/squid-2.4.STABLE6-10.21as.ia64.rpm
465f0c77fd485041607ffe5b65e3adfa 2.1ES/en/os/SRPMS/squid-2.4.STABLE6-10.21as.src.rpm
2f72879474d822e5ee35c6169f3d350d 2.1ES/en/os/i386/squid-2.4.STABLE6-10.21as.i386.rpm
2732d4487caab1fa0d3238dbe2c6a1e6 3AS/en/os/SRPMS/squid-2.5.STABLE3-5.3E.src.rpm
f49a76f72f5811387b337cbfe6fea983 3AS/en/os/i386/squid-2.5.STABLE3-5.3E.i386.rpm
f436a858a28cf351802a7ae4b792d9ca 3AS/en/os/ia64/squid-2.5.STABLE3-5.3E.ia64.rpm
3c5c99d1fea5ab90596557a78ef21a91 3AS/en/os/ppc/squid-2.5.STABLE3-5.3E.ppc.rpm
f230504e2f3aee72fe46754ae0dc0e9e 3AS/en/os/ppc64/squid-2.5.STABLE3-5.3E.ppc64.rpm
9370229f49341fa002dfc566edbae0e6 3AS/en/os/s390/squid-2.5.STABLE3-5.3E.s390.rpm
5b5b760cb7b52691c1055b87bdc33183 3AS/en/os/s390x/squid-2.5.STABLE3-5.3E.s390x.rpm
9041369b91c153bb4f7ba392c62327ae 3AS/en/os/x86_64/squid-2.5.STABLE3-5.3E.x86_64.rpm
2732d4487caab1fa0d3238dbe2c6a1e6 3ES/en/os/SRPMS/squid-2.5.STABLE3-5.3E.src.rpm
f49a76f72f5811387b337cbfe6fea983 3ES/en/os/i386/squid-2.5.STABLE3-5.3E.i386.rpm
2732d4487caab1fa0d3238dbe2c6a1e6 3WS/en/os/SRPMS/squid-2.5.STABLE3-5.3E.src.rpm
f49a76f72f5811387b337cbfe6fea983 3WS/en/os/i386/squid-2.5.STABLE3-5.3E.i386.rpm
f436a858a28cf351802a7ae4b792d9ca 3WS/en/os/ia64/squid-2.5.STABLE3-5.3E.ia64.rpm
9041369b91c153bb4f7ba392c62327ae 3WS/en/os/x86_64/squid-2.5.STABLE3-5.3E.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key is
available from https://www.redhat.com/security/team/key.html

You can verify each package with the following command:
    
    rpm --checksig -v <filename>

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    
    md5sum <filename>


8. References:

http://www.squid-cache.org/Advisories/SQUID-2004_1.txt
http://www.microsoft.com/security/incident/spoof.asp
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0189

9. Contact:

The Red Hat security contact is <secalert@redhat.com>.  More contact
details at https://www.redhat.com/security/team/contact.html

Copyright 2004 Red Hat, Inc.
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