_      __    _          ____                   
 | | /| / /__ (_)_____   / __/_ ________ ___ ____
 | |/ |/ / -_) /_ /_ /  / _// // /_ /_ // -_) __/
 |__/|__/\__/_//__/__/ /_/  \_,_//__/__/\__/_/   
                                               v1.0

  Written and maintained by Andrea Fioraldi <andreafioraldi@gmail.com>
  Based on American Fuzzy Lop by Michal Zalewski

What

Weizz is a fuzzer implementing a technique to automatically apply structural mutations without an input format model. It targets unknown chunk-based binary formats, so it is not a general purpose fuzzer.

The main idea is that as comparison instructions can be used to bypass fuzzing roadblocks (e.g. Redqueen), maybe we can use them too to collect insights about the parsed input format.

So the Weizz technique reason about comparisons for both roadblocks bypassing and structural mutations. Comparisons are used to guess input fields and other metadata collected during the tracing, like the timestamp of a comparison, are used to guess an approximate structure of the chunks on-the-fly while mutating.

The structural mutations are inspired by AFLSmart.

Prepare and Build

Download Weizz with:

$ git clone https://github.com/andreafioraldi/weizz-fuzzer

Build the fuzzer, the QEMU and the LLVM tracers with:

$ make

Usage

The command line usage of Weizz is similar to AFL.

$ ./prepare_sys.sh # needed only one time each boot
$ ./weizz -i seeds_dir -o findings_dir [ options ] -- ./program [ args... ]

Use weizz --help to show the all commands.

Note that the llvm-tracer is experimental and lacks of the checksums pacthing and context-sensitive coverage.

Example

Download the lastest snapshot of the FFmpeg source.

$ wget https://ffmpeg.org/releases/ffmpeg-snapshot.tar.bz2
$ tar xvf ffmpeg-snapshot.tar.bz2

Build it without instrumentation:

$ cd ffmpeg
$ ./configure
$ make

Fuzz FFmpeg with Weizz in QEMU mode enabling the structural mutations (-w -h) and a limit of 8k for each testcase to enter in getdeps:

$ mkdir INPUTS
$ cp /path/to/weizz/testcases/5.7kb.avi INPUTS/
$ WEIZZ_CTX_SENSITIVE=1 /path/to/weizz/weizz -i INPUTS -o OUTPUT \
  -d -w -h -Q -L 8k -- ./ffmpeg -y -i @@ -c:v mpeg4 -c:a out.mp4

Cite

Preprint: https://andreafioraldi.github.io/assets/weizz-issta2020.pdf

Presentation video: https://www.youtube.com/watch?v=67Bj1AaEECE

@inproceedings{weizz-ISSTA20,
    author = {Fioraldi, Andrea and D'Elia, Daniele Cono and Coppa, Emilio },
    title = {{WEIZZ}: Automatic Grey-box Fuzzing for Structured Binary Formats},
    year = {2020},
    isbn = {9781450380089},
    publisher = {Association for Computing Machinery},
    address = {New York, NY, USA},
    url = {https://doi.org/10.1145/3395363.3397372},
    doi = {10.1145/3395363.3397372},
    booktitle = {Proceedings of the 29th ACM SIGSOFT International Symposium on Software Testing and Analysis},
    series = {ISSTA 2020}
}