ProgSoc Fuzzing Workshop Demo

This repo is a basic json parser that I wrote the other day, with a few bugs intentionally included.

See if you can spot them before they are found by the fuzzer!

Setup

First, make sure you have cargo-fuzz installed:

cargo install --locked cargo-fuzz

Keep in mind that rust-fuzz requires nightly rust, so make sure you have that installed and up to date.

Looking at the project

This project contains a lib.rs file which has all the json parsing logic, along with a main.rs if you want to quickly run it and test.rs to run tests on "every" edge case that I could think of. Surely that's enough for right?

Feel free to play around with it and see if you can break it yourself.

Setting up fuzzing

Run cargo fuzz init to set up the fuzzing in this folder. This creates a folder called fuzz.

Under fuzz/fuzz_targets, rename the target to whatever you like, make sure you update fuzz/Cargo.toml accordingly.

Inside the fuzzing macro, set up the function to fuzz as you prefer, for example:

fuzz_target!(|data: &[u8]| {
    if let Ok(s) = std::str::from_utf8(data) {
        let _ = json::parse_json(s);
    }
});

It will throw random inputs at it until it panicks or crashes the process.

Now, just run cargo fuzz <your target name>, and watch it automatically find bugs!

Results!

For spoilers on the results, check out BUGS.md. Though I recommend trying to find them yourself first.