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phpMyAdmin Multiple CSRF Vulnerabilities



Advisory 07/2006: phpMyAdmin Multiple CSRF Vulnerabilities
Advisory 07/2006: phpMyAdmin Multiple CSRF Vulnerabilities



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                        Hardened-PHP Project
www.hardened-php.net 

                      -= Security  Advisory =-


     Advisory: phpMyAdmin Multiple CSRF Vulnerabilities
 Release Date: 2006/10/01
Last Modified: 2006/10/01
Author: Stefan Esser [sesser@hardened-php.net] 

  Application: phpMyAdmin <= 2.9.0
     Severity: Multiple vulnerabilities within phpMyAdmin allow
               bypassing it's protection against CSRF 
         Risk: Medium Critical
Vendor Status: Vendor has a released an updated version
References: http://www.hardened-php.net/advisory_072006.130.html 


Overview:

Quote from http://www.phpmyadmin.net 
   "phpMyAdmin is a tool written in PHP intended to handle the 
   administration of MySQL over the Web. Currently it can create and 
   drop databases, create/drop/alter tables, delete/edit/add fields, 
   execute any SQL statement, manage keys on fields, manage privileges,
   export data into various formats and is available in 50 languages."

   During an audit of phpMyAdmin's protection against CSRF: Cross Site
   Request Forgeries we discovered that there were multiple ways to
   bypass the protection.
   
   The failure of phpMyAdmin's CSRF protection obviously means that a
   potential attacker can use CSRF attacks to trick the browser of a
   phpMyAdmin user to execute any kind of SQL queries on the victims 
   database server.


Details:

   phpMyAdmin uses a random token that is stored within the user's
   session to protect against Cross Site Request Forgeries. CSRF
   basically means that a website tricks the browser of a visiting
   user into issuing HTTP requests against another site that does
   ensure, that the request was intended.
   
   In case of phpMyAdmin a CSRF vulnerability obviously means that
   another site could trick the browser of a phpMyAdmin user into
   issuing arbitrary SQL queries against his database.
   
   In phpMyAdmin the CSRF protection works like this
   
      1) Start PHP's Session Handling
      2) Is there already a token assigned to the session?
         -> No: create a random token
      3) Is supplied token equal to session token?
         -> No: unset() all request variables not in white-list
      
   While this design could actually work the implementation in
   phpMyAdmin was vulnerable to multiple attacks because before 
   and during the 3 steps mentioned several modifications to the
   request variable arrays are made and these variables get
   globalised. (This is done within the PHP code and has nothing
   to do with register_globals)
   
   The attacks we found attack different phases of the CSRF
   protection. The following is an overview of the vulnerabilities
   within the 3 phases. For each phase several different attacks
   are possible. Several of the attacks require GPC variables
   with names that are equal to PHP's superglobals, therefore
   these attacks are automatically stopped by our Suhosin extension.
   
   [-- Token Verification --]
   
   The token verification could be tricked because there existed
   several flaws in the globalisation routine that allowed 
   destroying the content of the session variables. Additionally
   the special handling of session variables during while
   register_globals is activated allowed directly setting the
   session token from within the URL.
   Obviously it is very easy to "guess" the required token when
   the token is empty or is set to a value of his choice.
   
   [-- Determine which variables to unset --]
   
   The _REQUEST array was used to determine which variables should
   be unset() but phpMyAdmin contained intended and unintended ways
   that allowed overwriting the content of the _REQUEST array.
   In the new version all GPC arrays are used for this process and 
   the unintended way to destroy superglobal arrays within the 
   globalisation was closed.
      
   [-- Unset variables --]
   
   Unset() is a dangerous function because older PHP versions
   (that are still installed on most servers) contained 
   vulnerabilities that allowed bypassing it.
   
   For further information take a look at:
   
http://www.hardened-php.net/critical_php_vulnerability_explained.124.html 
   

Proof of Concept:

   The Hardened-PHP Project is not going to release exploits for
   this vulnerability to the public.


Disclosure Timeline:

   23. September 2006 - Contacted phpMyAdmin developers by email
   01. October 2006   - Updated phpMyAdmin was released
   01. October 2006   - Public Disclosure


Recommendation:

   It is strongly recommended to upgrade to the newest version of
   phpMyAdmin 2.9.0.1 which you can download at:

http://www.phpmyadmin.net/home_page/downloads.php 
   
   As usual we very strongly recommend to install our Suhosin PHP 
   extension. It disallows request variables with the same name
   as PHP superglobal arrays. This stops several of the attacks
   described in this advisory.
   
   Grab your copy and more information at:
   
http://www.hardened-php.net/suhosin/index.html 
   

GPG-Key:

http://www.hardened-php.net/hardened-php-signature-key.asc 

   pub  1024D/0A864AA1 2004-04-17 Hardened-PHP Signature Key
   Key fingerprint = 066F A6D0 E57E 9936 9082  7E52 4439 14CC 0A86 4AA1


Copyright 2006 Stefan Esser. All rights reserved.

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