Adding a dictionary element that terminates a bit stream

[Samuel Xifaras]

Hello all,

I am working on a fuzzing-related project, using the Atheris fuzzer for Python, which is built on top of libfuzzer, and it would be very helpful for us if we could store some metadata in each fuzzing sample after some magic terminator value that has a 0% probability of getting mutated. I am aware of libfuzzer's dictionary capability, but as far as I know there is no way to achieve what I'm describing with that feature. I am considering modifying the libfuzzer codebase to achieve this. Before I do this though, I wanted to ask: are there easier ways to accomplish what I'm thinking of? And as I dive into the codebase, where should I start, and is there anything about the feature I described that would result in a lot of complexity given how the software is designed?

Hopefully that was clear, and I look forward to hearing back. Thanks!

Best,

Sam