Add custom mutate, post mutate, fuzzer_test_tlv_server

[ghost]

As I mentioned on Issue#64, I made this pull request mainly focusing on network server/client application fuzzing.

I only use built-in LibFuzzer mutator on example, but you can also using with other custom mutators like libprotobuf-mutator for structure-aware fuzzing.

I used multi input fuzzing feature with my test socket server. I know that test code quality is like shit but at least you will see that it works like persistent mode as I wanted.

[0vercl0k]

Wow this looks pretty cool, thanks for working on this @y0ny0ns0n 🙏🏽I'll be reviewing this this week!

Cheers

[0vercl0k]

All right, I've read the code and I think I have a good understanding of the scenarios you'd like to enable.

I've been wanting to have a mechanism for fuzzing modules to provide their mutator logic for a while so I like that now you can customize those. It means that we could implement multi packet as some sort of utility function / class and users can use it if they want and the core doesn't need to know about it. I also like the TLV server example, I think it'd be good to include this as well in wtf as it shows a more advanced usage.

What I'd like to change in your proposal is to basically move the multi packet logic into a mutator instead of having this logic inside the core of wtf. I don't think it brings anything more to have it in the core; I think it actually potentially limits what the user could do.

What do you think?

cc @yrp604

[ghost]

Yep. I agree with that. I also think user can control those things on CustomMutate function

[0vercl0k]

Thanks a lot @y0ny0ns0n 🙏🏽🎉 - I'll be working on adding the server / cleaning up the code / updating the doc, etc. in other PRs which I'll add you too FYI :)

Cheers