How to implement a security sub-system?

Question

Hi Everyone,
I got the following task below from my team leader. I don't know where to start to get the following task done. If you have any idea on how to get the following task done, please give me the steps on how to complete the following task. Or give me some links (websites) which can get me start on getting the following task done. Thanks for your time and help in advance!
Your next task is depicted in the case scenario as follows:
Some remote process is able to view a directory listing of the files on the directory and then selects a JSP file to execute. It runs without any enforced permission on the server and the remote process is able to view the output or that the JSP file is executed without the proper caller - a DocIt system process (JSP, Javabean). How can we solve this problem?
For one thing the directory listing permissions should only be permitted explicitly by the server "system security/permission objects" (configured by the administrator/root) on win32/Linux. Second, all JSP files must include a security module as part of it's code base before even a single line of code is written by the programmer. This ensures that at least the caller is allowed certain permissions to execute the code residing in the JSP file. The granularity of the permissions depend directly on the type of caller. Is it a "user", a "power user", a "system admin", a "pre-defined DocIt system object" (forms subsystem), and so on. We need a powerful yet flexible security system as it is important to register the permitted objects to execute only the rightful code determined by the DocIt system security policy.
This task is less specific and thus you have more flexibility to provide a solution. Please describe and analyze a security policy to prevent any executable code from running without its proper caller for the case scenario above. Be creative in determining the requirements for identifying the calling object and the code that checks for the proper credentials before permitting execution of the code. Say you have an hierarchy of inheritable permission objects. The code must be able to check that the caller belongs to the set of permission objects. Please use diagrams, cases scenarios, and other designs to provide a basis for implementation. After the designs are reviewed along side any other requirements we will implement this security sub-system in the near future

Answer 1

You may also want to look at JAAS. http://java.sun.com/developer/technicalArticles/Security/jaasv2/
It's probably a tad overkill for some JSP applications, but it would give you an additional layer of protection for documents, i.e., you can control access to actual files based on roles. I say it's a bit of overkill because Tomcat incorporates most of the ideas into their realms.