These instructions lead you through setup and fuzzing of a sample program.

Setup

Jump to the appropriate part of this Setup section based on what you're configuring, then go to the next section (Building AFL).

Logging in to the provided instance

If you're reading these instructions then you've probably already made it! Skip to the vulnerable program section.

Running the docker image locally

See the "Running locally" section of docker/README.md, then skip to the vulnerable program section.

Setting up your own machine manually

Install dependencies (this is more than you need just for AFL, but you'll end up wanting these during the workshop; see the Dockerfile for a comprehensive list of dependencies for all of the challenges):

$ sudo apt-get install git build-essential curl libssl-dev sudo libtool libtool-bin libglib2.0-dev bison flex automake python3 python3-dev python3-setuptools libpixman-1-dev gcc-9-plugin-dev cgroup-tools \
clang-11 clang-tools-11 libc++1-11 libc++-11-dev libc++abi1-11 libc++abi-11-dev libclang1-11 libclang-11-dev libclang-common-11-dev libclang-cpp11 libclang-cpp11-dev liblld-11 liblld-11-dev liblldb-11 liblldb-11-dev libllvm11 libomp-11-dev libomp5-11 lld-11 lldb-11 python3-lldb-11 llvm-11 llvm-11-dev llvm-11-runtime llvm-11-tools

Work around some Ubuntu annoyances

$ sudo update-alternatives --install /usr/bin/clang clang `which clang-11.0` 1
$ sudo update-alternatives --install /usr/bin/clang++ clang++ `which clang++-11.0` 1
$ sudo update-alternatives --install /usr/bin/llvm-config llvm-config `which llvm-config-11.0` 1
$ sudo update-alternatives --install /usr/bin/llvm-symbolizer llvm-symbolizer `which llvm-symbolizer-11.0` 1

Get, build, and install afl:

    $ git clone https://github.com/AFLplusplus/AFLplusplus
    $ cd AFLplusplus
    $ git checkout 2.68c # if you want a specific version, otherwise skip this step
    $ make distrib
    $ sudo make install

Make system not interfere with crash detection, plus some other tweaks:

$ ~/AFLplusplus/afl-system-config

The vulnerable program

Build our quickstart program using the instrumented compiler:

$ cd quickstart
$ CC=afl-clang-fast AFL_HARDEN=1 make

Test it:

$ ./vulnerable
# Press enter to get usage instructions.
# Test it on one of the provided inputs:
$ ./vulnerable < inputs/u

Fuzzing

Fuzz it:

$ afl-fuzz -i inputs -o out ./vulnerable

Your session should soon resemble this:

For comparison you could also test without the provided example inputs, e.g.:

$ mkdir in
$ echo "my seed" > in/a
$ afl-fuzz -i in -o out ./vulnerable