Example/skeleton for using libprotobuf-mutator together with AFL.

0. Download and compile AFLplusplus
1. Put your protobuffer in gen/out.proto
2. Write your own protobuffer-message-to-raw-data methods
3. export AFL_CUSTOM_MUTATOR_ONLY=1
4. export AFL_CUSTOM_MUTATOR_LIBRARY=./mutator.so

The current implementation turns enum values into bytes. It was an experiment in encoding regexps as protobuffers. Unfortunately, PBs are not powerful enough to do that.

export AFL_CUSTOM_MUTATOR_ONLY=1
export AFL_CUSTOM_MUTATOR_LIBRARY=./mutator.so
afl-fuzz -i /tmp/in -o /tmp/out -Q -- ./dumper @@

In order to dump/verify the content of the protobuffers:

for f in /tmp/out/queue/id*src*; do echo "== $f =="; ./dumper $f; done

./build.sh
make

• AFLplusplus doesn't yet provide a custom splicing hook, so we can't mix two protobuffers
  • I have a custom version on my PC but I'm not sure it's bug-free so I won't push it for the time being
• honggfuzz has support for external mutators/postprocessors, so it should be trivial to add support (maybe it'll be a little bit slower do to I/O)