American Fuzzy Lop plus plus (AFL++)

Release version: 4.33c

GitHub version: 4.34a

Repository: https://github.com/AFLplusplus/AFLplusplus

AFL++ is maintained by:

• Marc "van Hauser" Heuse mh@mh-sec.de
• Dominik Maier mail@dmnk.co
• Andrea Fioraldi andreafioraldi@gmail.com
• Heiko "hexcoder-" Eissfeldt heiko.eissfeldt@hexco.de
• frida_mode is maintained by @Worksbutnottested

Originally developed by Michal "lcamtuf" Zalewski.

AFL++ is a superior fork to Google's AFL - more speed, more and better mutations, more and better instrumentation, custom module support, etc.

You are free to copy, modify, and distribute AFL++ with attribution under the terms of the Apache-2.0 License. See the LICENSE for details.

Getting started

Here is some information to get you started:

• For an overview of the AFL++ documentation and a very helpful graphical guide, please visit docs/README.md.
• To get you started with tutorials, go to docs/tutorials.md.
• For releases, see the Releases tab and branches. The best branches to use are, however, stable or dev - depending on your risk appetite. Also take a look at the list of important changes in AFL++ and the list of features.
• If you want to use AFL++ for your academic work, check the papers page on the website.
• To cite our work, look at the Cite section.
• For comparisons, use the fuzzbench aflplusplus setup, or use afl-clang-fast with AFL_LLVM_CMPLOG=1. You can find the aflplusplus default configuration on Google's fuzzbench.

Building and installing AFL++

To have AFL++ easily available with everything compiled, pull the image directly from the Docker Hub (available for both x86_64 and arm64):

shell docker pull aflplusplus/aflplusplus docker run -ti -v /location/of/your/target:/src aflplusplus/aflplusplus

This image is automatically published when a push to the stable branch happens (see branches). If you use the command above, you will find your target source code in /src in the container.

Note: you can also pull aflplusplus/aflplusplus:dev which is the most current development state of AFL++.

To build AFL++ yourself - which we recommend - continue at docs/INSTALL.md.

Quick start: Fuzzing with AFL++

NOTE: Before you start, please read about the common sense risks of fuzzing.

This is a quick start for fuzzing targets with the source code available. To read about the process in detail, see docs/fuzzingindepth.md.

To learn about fuzzing other targets, see: * Binary-only targets: docs/fuzzingbinary-onlytargets.md * Network services: docs/best_practices.md#fuzzing-a-network-service * GUI programs: docs/best_practices.md#fuzzing-a-gui-program

Step-by-step quick start:

1. Compile the program or library to be fuzzed using afl-cc. A common way to do this would be:

CC=/path/to/afl-cc CXX=/path/to/afl-c++ ./configure --disable-shared make clean all

1. Get a small but valid input file that makes sense to the program. When fuzzing verbose syntax (SQL, HTTP, etc.), create a dictionary as described in dictionaries/README.md, too.

2. If the program reads from stdin, run afl-fuzz like so:

./afl-fuzz -i seeds_dir -o output_dir -- \ /path/to/tested/program [...program's cmdline...]

To add a dictionary, add -x /path/to/dictionary.txt to afl-fuzz.

If the program takes input from a file, you can put @@ in the program's command line; AFL++ will put an auto-generated file name in there for you.

1. Investigate anything shown in red in the fuzzer UI by promptly consulting docs/afl-fuzz_approach.md#understanding-the-status-screen.

2. You will find found crashes and hangs in the subdirectories crashes/ and hangs/ in the -o output_dir directory. You can replay the crashes by feeding them to the target, e.g. if your target is using stdin:

cat output_dir/crashes/id:000000,* | /path/to/tested/program [...program's cmdline...]

You can generate cores or use gdb directly to follow up the crashes.

1. We cannot stress this enough - if you want to fuzz effectively, read the docs/fuzzingindepth.md document!

Contact

Questions? Concerns? Bug reports?

• The contributors can be reached via (e.g., by creating an issue): https://github.com/AFLplusplus/AFLplusplus.
• Take a look at our FAQ. If you find an interesting or important question missing, submit it via https://github.com/AFLplusplus/AFLplusplus/discussions.
• Best: join the Awesome Fuzzing Discord server.
• There is a (not really used) mailing list for the AFL/AFL++ project (browse archive). To compare notes with other users or to get notified about major new features, send an email to afl-users+subscribe@googlegroups.com, but note that this is not managed by us.

Branches

The following branches exist:

• release: the latest release
• stable/trunk: stable state of AFL++ - it is synced from dev from time to time when we are satisfied with its stability
• dev: development state of AFL++ - bleeding edge and you might catch a checkout which does not compile or has a bug. We only accept PRs (pull requests) for the 'dev' branch!
• (any other): experimental branches to work on specific features or testing new functionality or changes.

Help wanted

We have several ideas we would like to see in AFL++ to make it even better. However, we already work on so many things that we do not have the time for all the big ideas.

This can be your way to support and contribute to AFL++ - extend it to do something cool.

For everyone who wants to contribute (and send pull requests), please read our contributing guidelines before you submit.

Special thanks

Many of the improvements to the original AFL and AFL++ wouldn't be possible without feedback, bug reports, or patches from our contributors.

Thank you! (For people sending pull requests - please add yourself to this list :-)

Cite

If you use AFL++ in scientific work, consider citing our paper presented at WOOT'20:

Andrea Fioraldi, Dominik Maier, Heiko Eißfeldt, and Marc Heuse. “AFL++: Combining incremental steps of fuzzing research”. In 14th USENIX Workshop on Offensive Technologies (WOOT 20). USENIX Association, Aug. 2020.