PHP-Nuke 8.x Cross Site Request Forgery

`PHP-Nuke 8.x <= Cross Site Request Forgery (CSRF) / Anti-CSRF Bypass  
Vulnerability  
  
  
  
1. OVERVIEW  
  
The PHP-Nuke version 8.x and lower versions are vulnerable to Cross  
Site Request Forgery (CSRF) because its Anti-CSRF mechanism (Referer  
Check) is found to be broken.  
  
  
2. BACKGROUND  
  
PHP-Nuke is a Web Portal System or content management system. The goal  
of PHP-Nuke is to have an automated web site to distribute news and  
articles with users system. Each user can submit comments to discuss  
the articles. Main features include: web based admin, surveys, top  
page, access stats page with counter, user customizable box, themes  
manager for registered users, friendly administration GUI with graphic  
topic manager, option to edit or delete stories, option to delete  
comments, moderation system, Referrers page to know who link us,  
sections manager, customizable HTML blocks, user and authors edit, an  
integrated Banners Ads system, search engine, backend/headlines  
generation (RSS/RDF format), and many, many more friendly functions.  
  
  
3. VULNERABILITY DESCRIPTION  
  
The PHP-Nuke version 8.x and lower versions contain a flaw that allows  
a remote Cross-site Request Forgery (CSRF / XSRF) attack. The flaw  
exists because the application does not require multiple steps or  
explicit confirmation for sensitive transactions for majority of  
administrator functions such as adding new user, assigning user to  
administrative privilege. By using a crafted URL, an attacker may  
trick the victim into visiting to his web page to take advantage of  
the trust relationship between the authenticated victim and the  
application. Such an attack could trick the victim into executing  
arbitrary commands in the context of their session with the  
application, without further prompting or verification.  
  
  
4. VERSIONS AFFECTED  
  
8.0 and lower  
  
Tested version: 8.0  
The paid versions, 8.1 and 9.0, of PHP-Nuke may be vulnerable as well.  
  
  
5. PROOF-OF-CONCEPT/EXPLOIT  
  
Consider the following code snippet in /mainfile.php of PHP-Nuke:  
  
//////////////////////////////////////////////////////////////////////////////  
  
109 if(!function_exists('stripos')) {  
function stripos_clone($haystack, $needle, $offset=0) {  
$return = strpos(strtoupper($haystack), strtoupper($needle), $offset);  
if ($return === false) {  
return false;  
} else {  
return true;  
}  
}  
} else {  
// But when this is PHP5, we use the original function  
function stripos_clone($haystack, $needle, $offset=0) {  
$return = stripos($haystack, $needle, $offset=0);  
if ($return === false) {  
return false;  
} else {  
return true;  
}  
}  
128 }  
  
......  
  
206 // Posting from other servers in not allowed  
207 // Fix by Quake  
208 // Bug found by PeNdEjO  
  
210 if ($_SERVER['REQUEST_METHOD'] == "POST") {  
if (isset($_SERVER['HTTP_REFERER'])) {  
212 if (!stripos_clone($_SERVER['HTTP_REFERER'], $_SERVER['HTTP_HOST'])) {  
die('Posting from another server not allowed!');  
}  
} else {  
die($posttags);  
}  
}  
//////////////////////////////////////////////////////////////////////////////  
  
It is clear that stripos_clone checks HTTP_REFERER value whether it  
matches the target domain or not.  
Attacker can easily bypass it by creating victim domain name under his  
web root folder like:  
  
http://attacker.in/victim.com/  
  
>From there, he could effectively perform CSRF attacks against php-Nuke users.  
  
A short P0C demo video can be seen at  
http://yehg.net/lab/pr0js/training/view/misc/PHPNuke_8x_Anti-CSRF-Bypass/  
  
  
6. SOLUTION  
  
Not Available.  
Use of this product is NOT recommended because of long lack of update  
and vendor negligence about security reports.  
  
  
7. VENDOR  
  
PHP-Nuke Developers  
http://phpnuke.org/  
  
  
8. CREDIT  
  
Aung Khant, http://yehg.net, YGN Ethical Hacker Group, Myanmar.  
  
  
9. DISCLOSURE TIME-LINE  
  
2011-01-01: contacted author through emails  
2011-01-25: contacted author through web site contact form  
2010-03-23: no replies from author  
2010-03-23: vulnerability disclosed  
  
  
10. REFERENCES  
  
Original Advisory URL:  
http://yehg.net/lab/pr0js/advisories/[phpnuke-8.x]_cross_site_request_forgery  
CSRF Wiki: https://secure.wikimedia.org/wikipedia/en/wiki/Cross-site_request_forgery  
About PHP-Nuke: http://en.wikipedia.org/wiki/PHP-Nuke  
PHP-Nuke 8.0: http://phpnuke.org/modules.php?name=Downloads&d_op=getit&lid=658  
CWE-352: http://cwe.mitre.org/data/definitions/352.html  
  
#yehg [2010-03-23]  
  
keywords: php nuke, php-nuke, phpnuke, 8.0, 8.1, csrf  
  
  
  
---------------------------------  
Best regards,  
YGN Ethical Hacker Group  
Yangon, Myanmar  
http://yehg.net  
Our Lab | http://yehg.net/lab  
Our Directory | http://yehg.net/hwd  
  
`