Linux Firewall Project

A project to build a simple firewall and file access control system into the 4.x Linux kernel (for x86 architectures).

At a high level, the new functionality adds a few system calls directly to the kernel. They're exposed only to the root user through CLI commands. The commands allow root to block, unblock, and check the status of TCP/UDP ports and any file on the filesystem.

Here's What's Interesting

• Project Documentation - this documentation folder contains the design docs for the project, including both a preliminary exploration through the kernel and the final design explanation.
• Tests - the tests folder contains its own README for instructions on running the numerous and detailed test bench that I custom wrote for this project. See below for a sample test run.
• Code - this is where some of the custom code lives, mostly net-new code that was added to the kernel, not including modifications of existing files or functions. You can also check out these files for more interesting code points:
  • fw_421.c - system call implementations
  • namei.c - filesystem controls
  • socket.c - firewall controls
  • Other modifications are noted in the Project Documentation

Sample Test Run

Background

This project was the second of two in my college operating systems course (you'll notice proj2 and 421 baked into many identifiers).

This project was one of the most difficult, yet rewarding, I've ever worked on. It gave me a whole new appreciation for software and operating systems, that latter of which I'd like to have a career in one day. Despite that I scored over 100% on this assignment (after extra credit and a curve), I still have one failing test in my test suite that I intend to solve some day.