MSA080801

Tomcat File Inclusion Vulnerabity


Tested OS:
Linux Ubuntu 8.04


Tested Tomcat Versions:
Tomcat <= 6.0.16
Tomcat <= 5.5.26
Tomcat <= 4.1.37
Tomcat <= 5.0.x
Tomcat <= 4.0.x
Tomcat <= 3.x


Note: several Tomcat based application server such as JBoss, glassfish and Sun Java System Web Server could be affected as well.

Vulnerability identifier:

CVE-2008-2370

Minded Security ReferenceID:
MSA080801

Credits:
Discovered by
Stefano Di Paola of Minded Security

Reference: MSA080801

Solution:
Upgrade to latest Tomcat version or patches:
http://tomcat.apache.org/

Summary
Tomcat server fails in normalizing the path of uri part including the query string in the normalization algorithm, leading to potential directory traversal in the context of the web server root.

Proof of Concept
Let's suppose a server side Jsp is used to dispatch requests to internal pages passing parts of the query string.

---page.jsp---

<%
pageContext.forward("/page2.jsp?parameter="+request.getParameter("aparam"))
%>

---end page.jsp----


Tomcat server fails in normalizing the path of uri part including the query string in the normalization algorithm.

In particular the problem lies in the fact that Tomcat calls
RequestUtil.normalize(path);

before parsing the url for '?'.

Infact, the string will become:

pageContext.forward("/page.jsp?parameter=/../WEB-INF/web.xml");

This fools Tomcat considering

'page2.jsp?somepar=someval&par='

as a file and then when normalize() is called, the presence of

/../

makes the argument of forward() to point to:

/WEB-INF/web.xml

and will send the content of web.xml as response to our request.
Obviously the same could be done for every class and file existing in the root of the application.

Disclosure Timeline
13/06/2008 Initial vendor notification
17/06/2008 Vendor Confirmed
15/07/2008 Coordinated public disclosure
01/08/2008 Vendor Security Bullettin
04/08/2008 Minded Security Research Lab Advisory

Acknowledgements
Minded Security would like to thanks Mario Manfredi and Loris Delpero for initial heads up.

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