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Advisory 21/2005: Multiple vulnerabilities in PHPKIT
From: Christopher Kunz <christopher.kunz () hardened-php net>
Date: Tue, 08 Nov 2005 09:23:57 +0100

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                        Hardened PHP Project
                        www.hardened-php.net

                      -= Security  Advisory =-


     Advisory: Multiple vulnerabilities in PHPKIT
 Release Date: 2005/11/07
Last Modified: 2005/11/04
       Author: Christopher Kunz <christopher.kunz () hardened-php net>
  Application: PHPKIT 1.6.1 R2 and prior
     Severity: Cross-Site Scripting, SQL injection and information
               disclosure, password hash disclosure, local file
               disclosure, arbitrary code execution
         Risk: High / Critical (depending on server configuration)
Vendor Status: No fix available
   References: http://www.hardened-php.net/advisory_212005.80.html


Overview:

   PHPKIT [1] is a combined content management, homepage building and community
   software written in PHP. Although it is available as open source, it has
   to be licensed for any other than private use. PHPKIT has the usual feat-
   ures for that kind of product (content editing, forums, user management,
   etc.). Typically for content management and portal systems, there are
   multiple vulnerabilities in several places in the front- and backend.
   The install base for PHPKIT can only be estimated - Google shows about
   25,000 results for the query "powered by phpkit" [2].
   Since we did not perform a full audit, there is no guarantee that the de-
   scribed vulnerabilities are the only ones in the product.


Details:

   1) XSS
      Although the PHPKIT team seems to have made an effort to mitigate attacks
      with cross-site scripting, this was only partially successful. We found
      a number of critical XSS holes that can be exploited by any third party
      to steal admin cookies, change HTML code, launch CSRF attacks and so on.

   1.1) login/profile.php and login/userinfo.php
        Two fields in the profile settings - those for AIM and Yahoo! screen
        names - are inserted into the database without any input validation.
        Thus, an XSS attack can be performed that is launched on any user who
        looks at the offending profile.
        The same attack can be launched on an administrator viewing a profile
        via the administrator back-end.

   1.2) admin/admin.php (with register_globals On)
        Since the variable $site_body is not properly initialized, an attacker
        can launch an XSS attack against the administrator login screen. This
        attack can utilize DOM to steal the administrator's credentials in
        cleartext as long as they have some kind of "password safe" function
        in their browser. Since script code can be executed on load, all that
        an attacker has to do is get the administrator to click on a manipula-
        ted link.

   1.3) Referrer statistics
        By launching a HTTP request with the Referer set to some script code,
        e.g. <script>alert('foo')</script>, an attacker prompts this code to
        be included in the administrative backend, and executed as soon as
        an administrator views the referrer statistics. This comes in handy
        since it is a quasi-anonymous way of obtaining the administrator's
        session cookies.

   1.4) Forum
        Although input filtering takes place in the subject and content of
        a forum postings, no such filtering is performed when constructing
        the HTML <title> tag and the logo's <img alt> attribute - both con-
        tain the thread subject in unfiltered HTML, and script code is execu-
        ted twice per page.

   1.5) imcenter.php
        PHPKIT's own instant messaging system does not perform input validation
        on the subject line, so any user can IM the admin and contain script
        code in the subject.

   1.6) Guestbook
        The "Homepage" input field in the guest book is not properly sanitized
        and any guest (no logged-in users, because their home page is not dis-
        played by default) can enter script code. As usual, this is displayed
        as soon as the guestbook is viewed.

   2) SQL Injection
          Same as above: Although many places inside the PHPKIT software are not
          prone to SQL injection, some are. This leads to information disclosure
          and possibly deletion of arbitrary data in the database.

   2.1) SQL injection in profile pages (with magic_quotes_gpc Off)
        Using a simple injection, any user of the PHPKIT-powered web site can
        disclose the administrator's password hash. This is done via the $id
        parameter in login/userinfo.php which is not properly sanitized. With
        a crafted UNION statement, the attacker can obtain arbitrary data, in-
        cluding but not limited to any user's password hash. A simple cast into
        an int would have prevented this problem.
        Example: include.php?path=login/userinfo.php&id='%20UNION%20SELECT%201,
        1,user_pw,1,1,1,1,1,1,1,1,1,1,1,1,user_pw,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
        1,1,1,1,1,1%20FROM%20phpkit_user%20where%20%20user_id=1%20and%20'1'='1
        
   2.2) PHPKITSID
        Since sessions are contained within the database, an attacker can craft
        a session ID to contain SQL commands (which have to be exactly 32 Bytes
        in length, though. The vulnerable code is directly in include.php:
            if(isset($_REQUEST['PHPKITSID']))
                $session=$DB->fetch_array($DB->query("SELECT session_id,
                session_userid FROM ".$db_tab['session']." WHERE
            session_id='".$_REQUEST['PHPKITSID']."' LIMIT 1"));
        This SELECT yields one result which is then fed to another SQL query:
            $DB->query("DELETE FROM ".$db_tab['session']." WHERE session_id='"
            .$session['session_id']."' LIMIT 1");
        Using a carefully-crafted SQL statement, arbitrary data rows can be
        deleted from the database.

   3) Arbitrary local file inclusion and local code execution
      Using the vulnerable path parameter that is used in nearly every subsys-
      tem of PHPKIT, an attacker can include arbitrary files on the local file
      system. This includes uploaded avatars (preferrably in PNG format) that
      can also include PHP code. Uploading avatars is not enabled in the
      default configuration, so this attack vector is unlikely to be open in
      every PHPKIT installation in the wild.
      Example: echo "<?php phpinfo() ?>" >> avatar.png
               /phpkit/?path=../images/avatar/avauser_1.png%00

   4) Remote code execution (with register_globals On)
      Yeah, we saved the best for last. Since PHPKIT relies heavily on eval()
      for its homegrown template engine, an attacker only needs a way to inject
      a variable in curly braces including PHP code. With register_globals set
      to On (which is still the case in a lot of installations, for compati-
      bility purposes), this can be accomplished via the help function that
      makes use of not properly initialized variables. Thus, any PHP code can
      be executed.
      There is a number of other places, including the admin backend, that are
      vulnerable to this kind of code injection. These vulnerabilities are
      either exploitable via complex syntax (a.k.a. curly braces) or, if magic_
      quotes_gpc is turned Off, with any code that includes "".
      The whole template system urgently needs to be rewritten from scratch,
      without relying on unsafe variables and with careful consideration for
      register_globals.


Proof of Concept:

   Apart from the examples mentioned above, the Hardened PHP Project is not
   going to release any PoC for these vulnerabilities to the public.


Disclosure Timeline:

   30. September 2005 - Vendor informed.
   05. October 2005   - Vendor contacted via phone. Advisory re-sent (allegedly
                        lost in transit).
   16. October 2005   - Vendor informed of intended disclosure timeline.
   07. November 2005  - public disclosure at the 2005 International PHP Confer-
                        ence.


Credits:

   Credit for the vulnerabilities listed in 4) goes to Stefan Esser of the
   Hardened-PHP team.
   Credit for the vulnerability described in 2.2) goes to Stefan Walk.
   Credit for the vulnerability named 1.2) goes to Johann-Peter Hartmann.
   All other vulnerabilities were investigated by the author.


Recommendation:

   With the aforementioned lack in vendor reaction, we currently recommend
   avoiding usage of PHPKIT altogether.
   If you already use the product, we recommend installing the Hardening-Patch
   for PHP which can be obtained on our website, and deactivating the
   "register_globals" setting in php.ini, virtual host configuration or
   .htaccess.


References:

   [1] http://www.phpkit.de/
   [2] http://www.google.com/search?q=%22powered+by+PHPKIT%22


Plug:

   You can discuss this and other vulnerabilities in our forum at
   http://forum.hardened-php.net/ - an up-to-date list of advisories can be
   found at http://www.hardened-php.net/.


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 2005 Christopher Kunz / Hardened PHP Project. All rights reserved.

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