Apache Jakarta Tomcat 3 URL parsing vulnerability

[Jouko Pynnonen <jouko () solutions fi>]

OVERVIEW
========

Tomcat is a JSP/Servlet implementation developed at the Apache Software 
Foundation. Tomcat versions 3.3.1 and earlier contain some security 
vulnerabilities which allow a remote user to retrieve listings of  
directories despite index.html or index.jsp files. It is also possible 
to retrieve contents of files and directories that shouldn't be visible to 
outside. The vulnerability also allows retrieving the source of JSP files.



DETAILS
=======

Certain kinds of HTTP requests containing binary null or backslash 
characters are parsed incorrectly by Tomcat's built-in web server. The 
following GET request causes Tomcat to output the directory listing of 
the web root under default installation:

GET /<null byte>.jsp HTTP/1.0

The following UNIX command can be issued to test the vulnerability:

$ perl -e 'print "GET /\x00.jsp HTTP/1.0\r\n\r\n";' | nc my.server 8080

If your server is vulnerable, the command will output a HTTP header and 
the directory listing even if there's an index file present. Furthermore, 
a backslash can be used in the following way to get information from 
otherwise inaccessible directories:

$ perl -e 'print "GET /admin/WEB-INF\\classes/ContextAdmin.java\x00.jsp HTTP/1.0\r\n\r\n";'|nc my.server 8080

This will output the contents of ContextAdmin.java.

The servlet engine interprets the directory listing and any file 
retrieved in this way as a JSP page, which might be exploited to run 
arbitrary Java code under some imaginable scenarios. If the attacker can 
create a file whose name contains JSP tags somewhere under the web root, 
the code would be run when the directory listing is fetched in the way 
described above. Similarly Java code embedded in *.html or any other file 
can be compiled and run by an attacker.

In the same way a remote user may force a *.jsp file to be interpreted as 
plain HTML, ie. retrieve the source of JSP files:

$ perl -e 'print "GET /examples/jsp/cal/cal1.jsp\x00.html HTTP/1.0\r\n\r\n";'|nc my.server 8080

This would output the source of the example JSP file.



SOLUTION
========

The vendor was informed on January 10, 2003. A new version of Tomcat 
addressing this problem has been released. The fixed version 3.3.1a and 
additional information is available at

  http://jakarta.apache.org/builds/jakarta-tomcat/release/v3.3.1a/

According to the vendor, the problem only affects Tomcat used with JDK 
1.3.1 or earlier.



CREDITS
=======

The vulnerability was discovered by Jouko Pynnönen of Online Solutions 
Ltd, Finland.



-- 
Jouko Pynnonen          Online Solutions Ltd       Secure your Linux -
jouko () solutions fi      http://www.solutions.fi    http://www.secmod.com