Programming Project I
CS 6238 Secure Computer Systems
Due Date: March 29, 2007
For this project, you can work in a group of two.
In this programming project, you will implement a highly simplified “protected”
document store. More specifically, you will implement an access control module that
enforces specified access control policy for the documents. The focus of the project is on
implementing an access control list mechanism but you will also implement space
management associated with document storage. You can make the following simplifying
assumptions in this project.
1. You will create a large file which is used to store documents that users create and
update. This file is created by the document system at initialization time. You will
keep track of where documents are stored in the file and what areas are free.
2. Documents can be accessed using a document system API. In particular, once a
document is created, users can checkout a document when they have read access
for it, and they can check-in a document back into the system if they have write
access. In addition, the API includes calls that allow users to manage access
control lists associated with documents. Both negative and positive access rights
can be defined.
3. Users will authenticate to the document system using passwords. Once a user is
authenticated, a user identifier (UID) is returned. All calls to the document system
include the UID as the first argument. You can assume that the UID is
unforgeable like a capability.
4. A certain user can create a group and allow other users to be part of the group. In
fact, group members can be other groups as well. Access rights can also be
associated with groups.
5. A document can be deleted by its owner only.
You will implement the access controller and the document storage systems along with
code that tests the functionality provided by them. The test code will do multiple logins,
obtain UIDs, create documents and groups, update access rights, check-in and checkout
documents and clearly demonstrate that the system enforces the access policy that is
defined. To make the testing more dynamic you should read simple commands from a
file. By default, the owner of the document has both read and write access, but other
users must be granted access by the owner (either to a specific user or to a group to which
the user belongs).
The first task is to clearly define the document system API. Since you can use a
programming language of your choice, the exact API calls may differ. You will then
implement and demonstrate that the implementation works correctly. You are particularly
required to pay close attention to secure coding practices (you may want to try fuzzing to
ensure that there are no vulnerabilities such as buffer overflows).
