sandsifter VS fuzzing

This has some background.

sandsifter

This is a really clever technique! I was impressed by sandsifter[1] when it originally came out, and this seems an awful lot faster and less prone to false negatives (since it's purely speculative and doesn't require sandsifter's `#PF` hack).

At the risk of unwarranted self-promotion: the other side of this equation is fidelity in software instruction set decoders. x86's massive size and layers of historical complexity make it among the most difficult instruction formats to accurately decode; I've spent a good part of the last two years working on a fuzzer that's discovered thousands of bugs in various popular x86 decoders[2][3].

[1]: https://github.com/xoreaxeaxeax/sandsifter

[2]: https://github.com/trailofbits/mishegos

[3]: https://ww.easychair.org/publications/preprint_download/1LHr

Idea:

If any assembler/disassembler author/team out there wants to produce an assembler/disassembler which is authoritative (difficult to do on x86, because there are so many different possible combinations of instruction encoding, https://github.com/xoreaxeaxeax/sandsifter : "Typically, several million undocumented instructions on your processor will be found, but these generally fall into a small number of different groups.") -- then what they'd do is to create a third program -- which "pits" the output of Assembler A vs. Assembler B, Disassembler A vs. Disassembler B...

That is, between any two assemblers (for the same CPU architecture/instruction set), or any two disassemblers, where are the anomalies?

If we think about an assembler as a simple function, y=f(x), that is, I give it a string of ascii bytes as input (x), and I get a string (1..n) binary bytes as output (y),

so I just wanted to start to fuzz a little bit and I used libfuzzer for that. and as you can tell in this tutorial https://github.com/google/fuzzing/blob/master/tutorial/libFuzzerTutorial.md it tells you that if you leave it running like that you will get a bounty. and so I did exactly this, I followed the exact instructions listed there(I fuzzed this woff thing they mentioned) and my fuzzer said "SUMMARY: AddressSanitizer: heap-buffer-overflow" can I report that? or is this woff thing just for testing?

For a project like this, fuzz testing is also crucial. The issue pointed out by gremolata would have been trivial to find with fuzzing.

Another is testing: Many C++ projects use sanitizers regularly together with fuzzing, https://github.com/google/fuzzing/blob/master/docs/why-fuzz.md, https://github.com/google/fuzzing/blob/master/docs/intro-to-fuzzing.md#sanitizers

Maybe a bit biased opinion here, but you could start with this blog post, and see whether you go more into C/C++ fuzzing or web fuzzing from there:

https://blog.code-intelligence.com/the-magic-behind-feedback...

https://github.com/google/fuzzing