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Category:   Application (Security)  >   Mod_ssl Vendors:   Modssl.org
(Red Hat Issues Fix) Re: Apache mod_ssl 'Off-by-One' Bug May Let Local Users Crash the Web Server or Possibly Execute Arbitrary Code
SecurityTracker Alert ID:  1004790
SecurityTracker URL:  http://securitytracker.com/id/1004790
CVE Reference:   CAN-2002-0653   (Links to External Site)
Date:  Jul 18 2002
Impact:   Denial of service via local system, Execution of arbitrary code via local system, Modification of user information, User access via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.4.9 and prior
Description:   A vulnerability was reported in mod_ssl. A local user that can create '.htaccess' files may be able to cause mod_ssl to crash or execute arbitrary code on the system with the privileges of the web server.

An 'off-by-one' error has been reported in mod_ssl. The flaw reportedly exists in the ssl_compat_directive() while invoking the Apache web server rewrite_command extended API (EAPI) hook. According to the report, when backward compatibility is enabled, mod_ssl registers a rewrite_command hook and calls the ssl_compat_directive() function for every line read in a configuration file.

A local user that can create a '.htaccess' file on the web server can place specially crafted information in the file to cause Apache mod_ssl to execute arbitrary code when reading the file (e.g., when a remote user attempts to access a file in a directory protected by the '.htaccess' file).

Servers that allow virtual hosts and have the "AllowOverride" directive not set to "None" for virtual hosts may be affected if local users have access to any part of the web directory. Other configurations may also be vulnerable.

According to the report, mod_ssl compiled without backward compatibility is not vulnerable. However, the backward compatibility feature is reportedly enabled by default during compilation.

Impact:   A local user could cause denial of service conditions or could possibly execute arbitrary code with the privileges of the web server.
Solution:   Red Hat has issued a fix.

Red Hat Linux 7.0:

SRPMS:
ftp://updates.redhat.com/7.0/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm

alpha:
ftp://updates.redhat.com/7.0/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm

i386:
ftp://updates.redhat.com/7.0/en/os/i386/mod_ssl-2.8.5-5.i386.rpm

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm

alpha:
ftp://updates.redhat.com/7.1/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/mod_ssl-2.8.5-5.i386.rpm

ia64:
ftp://updates.redhat.com/7.1/en/os/ia64/mod_ssl-2.8.5-5.ia64.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/mod_ssl-2.8.5-6.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/mod_ssl-2.8.5-6.i386.rpm

ia64:
ftp://updates.redhat.com/7.2/en/os/ia64/mod_ssl-2.8.5-6.ia64.rpm

Red Hat Linux 7.3:

SRPMS:
ftp://updates.redhat.com/7.3/en/os/SRPMS/mod_ssl-2.8.7-6.src.rpm

i386:
ftp://updates.redhat.com/7.3/en/os/i386/mod_ssl-2.8.7-6.i386.rpm

The verification checksums are:

MD5 sum Package Name

68f324107e24931fbd3c13fd7f0a4f66 7.0/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm
5505cb06688d8d669a927dc5a29d0bac 7.0/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm
2fdd482796a973447d19e01cf8a11603 7.0/en/os/i386/mod_ssl-2.8.5-5.i386.rpm
68f324107e24931fbd3c13fd7f0a4f66 7.1/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm
5505cb06688d8d669a927dc5a29d0bac 7.1/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm
2fdd482796a973447d19e01cf8a11603 7.1/en/os/i386/mod_ssl-2.8.5-5.i386.rpm
9a0d26822a4055ccf1433d92c0c565a2 7.1/en/os/ia64/mod_ssl-2.8.5-5.ia64.rpm
39e695b50d1a2496cad55cf396ea5d88 7.2/en/os/SRPMS/mod_ssl-2.8.5-6.src.rpm
4a18209d091f3c8bbc2edc21ddbc0ae8 7.2/en/os/i386/mod_ssl-2.8.5-6.i386.rpm
56781cdd2dc2ca137aabe23d587ce783 7.2/en/os/ia64/mod_ssl-2.8.5-6.ia64.rpm
f7388246313fc23b83228361671fa8ff 7.3/en/os/SRPMS/mod_ssl-2.8.7-6.src.rpm
8c9e4f55866bd16df07bc945766bc680 7.3/en/os/i386/mod_ssl-2.8.7-6.i386.rpm

Vendor URL:  www.modssl.org/ (Links to External Site)
Cause:   Boundary error
Underlying OS:   Linux (Red Hat Linux)

Message History:   This archive entry is a follow-up to the message listed below.
Jun 27 2002 Apache mod_ssl 'Off-by-One' Bug May Let Local Users Crash the Web Server or Possibly Execute Arbitrary Code



 Source Message Contents

Date:  Tue, 16 Jul 2002 16:53 -0400
Subject:  [RHSA-2002:134-12] Updated mod_ssl packages available


---------------------------------------------------------------------
                   Red Hat, Inc. Red Hat Security Advisory

Synopsis:          Updated mod_ssl packages available
Advisory ID:       RHSA-2002:134-12
Issue date:        2002-07-01
Updated on:        2002-07-16
Product:           Red Hat Linux
Keywords:          mod_ssl overflow
Cross references:  RHSA-2002:135 RHSA-2002:136
Obsoletes:         RHSA-2002:041
CVE Names:         CAN-2002-0653
---------------------------------------------------------------------

1. Topic:

Updated mod_ssl packages are now available for Red Hat Linux 7, 7.1, 7.2,
and 7.3. These updates incorporate a fix for an incorrect bounds check in
versions of mod_ssl up to and including version 2.8.9.

2. Relevant releases/architectures:

Red Hat Linux 7.0 - alpha, i386

Red Hat Linux 7.1 - alpha, i386, ia64

Red Hat Linux 7.2 - i386, ia64

Red Hat Linux 7.3 - i386

3. Problem description:

The mod_ssl module provides strong cryptography for the Apache Web
server via the Secure Sockets Layer (SSL) and Transport Layer Security
(TLS) protocols.  Versions of mod_ssl prior to 2.8.10 are subject to a
single NULL overflow that can cause arbitrary code execution.

In order to exploit this vulnerability, the Apache Web server has to be
configured to allow overriding of configuration settings on a per-directory
basis, and untrusted local users must be able to modify a directory in
which the server is configured to allow overriding.  The local attacker may
then become the user that Apache is running as (usually 'www' or 'nobody').  

Note that regardless of this bug, local users can obtain the same
privileges if the server is configured to allow them to create CGI scripts
which run as the Web server user, or if PHP is enabled but not configured
in "safe mode".

The errata packages contain versions of mod_ssl that have been patched and
are not vulnerable to this issue.

Please note that you must restart the httpd daemon to use the updated
module. For instructions on doing this, see the bottom of the Solutions
section below.

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.

After the appropriate updates have been applied, it will be necessary to
manually restart the server with the following command:

/sbin/service httpd restart

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



6. RPMs required:

Red Hat Linux 7.0:

SRPMS:
ftp://updates.redhat.com/7.0/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm

alpha:
ftp://updates.redhat.com/7.0/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm

i386:
ftp://updates.redhat.com/7.0/en/os/i386/mod_ssl-2.8.5-5.i386.rpm

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm

alpha:
ftp://updates.redhat.com/7.1/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/mod_ssl-2.8.5-5.i386.rpm

ia64:
ftp://updates.redhat.com/7.1/en/os/ia64/mod_ssl-2.8.5-5.ia64.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/mod_ssl-2.8.5-6.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/mod_ssl-2.8.5-6.i386.rpm

ia64:
ftp://updates.redhat.com/7.2/en/os/ia64/mod_ssl-2.8.5-6.ia64.rpm

Red Hat Linux 7.3:

SRPMS:
ftp://updates.redhat.com/7.3/en/os/SRPMS/mod_ssl-2.8.7-6.src.rpm

i386:
ftp://updates.redhat.com/7.3/en/os/i386/mod_ssl-2.8.7-6.i386.rpm



7. Verification:

MD5 sum                          Package Name
--------------------------------------------------------------------------
68f324107e24931fbd3c13fd7f0a4f66 7.0/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm
5505cb06688d8d669a927dc5a29d0bac 7.0/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm
2fdd482796a973447d19e01cf8a11603 7.0/en/os/i386/mod_ssl-2.8.5-5.i386.rpm
68f324107e24931fbd3c13fd7f0a4f66 7.1/en/os/SRPMS/mod_ssl-2.8.5-5.src.rpm
5505cb06688d8d669a927dc5a29d0bac 7.1/en/os/alpha/mod_ssl-2.8.5-5.alpha.rpm
2fdd482796a973447d19e01cf8a11603 7.1/en/os/i386/mod_ssl-2.8.5-5.i386.rpm
9a0d26822a4055ccf1433d92c0c565a2 7.1/en/os/ia64/mod_ssl-2.8.5-5.ia64.rpm
39e695b50d1a2496cad55cf396ea5d88 7.2/en/os/SRPMS/mod_ssl-2.8.5-6.src.rpm
4a18209d091f3c8bbc2edc21ddbc0ae8 7.2/en/os/i386/mod_ssl-2.8.5-6.i386.rpm
56781cdd2dc2ca137aabe23d587ce783 7.2/en/os/ia64/mod_ssl-2.8.5-6.ia64.rpm
f7388246313fc23b83228361671fa8ff 7.3/en/os/SRPMS/mod_ssl-2.8.7-6.src.rpm
8c9e4f55866bd16df07bc945766bc680 7.3/en/os/i386/mod_ssl-2.8.7-6.i386.rpm
 

These packages are GPG signed by Red Hat, Inc. for security.  Our key
is available at:
    http://www.redhat.com/about/contact/pgpkey.html

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

8. References:

http://marc.theaimsgroup.com/?l=apache-modssl&m=102491918531562
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0653



Copyright(c) 2000, 2001, 2002 Red Hat, Inc.


 
 


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