AFLplusplus/custom_mutators/gramatron

GramaTron

Gramatron is a coverage-guided fuzzer that uses grammar automatons to perform grammar-aware fuzzing. Technical details about our framework are available in the ISSTA'21 paper. The artifact to reproduce the experiments presented in the paper are present in artifact/. Instructions to run a sample campaign and incorporate new grammars is presented below:

Compiling

Simply execute ./build_gramatron_mutator.sh

Running

You have to set the grammar file to use with GRAMMATRON_AUTOMATION:

export AFL_DISABLE_TRIM=1
export AFL_CUSTOM_MUTATOR_ONLY=1
export AFL_CUSTOM_MUTATOR_LIBRARY=./gramatron.so
export GRAMATRON_AUTOMATION=grammars/ruby/source_automata.json
afl-fuzz -i in -o out -- ./target

Adding and testing a new grammar

• Specify in a JSON format for CFG. Examples are correspond source.json files
• Run the automaton generation script (in src/gramfuzz-mutator/preprocess) which will place the generated automaton in the same folder.

./preprocess/prep_automaton.sh <grammar_file> <start_symbol> [stack_limit]

Eg. ./preprocess/prep_automaton.sh ~/grammars/ruby/source.json PROGRAM

• If the grammar has no self-embedding rules then you do not need to pass the stack limit parameter. However, if it does have self-embedding rules then you need to pass the stack limit parameter. We recommend starting with 5 and then increasing it if you need more complexity
• To sanity-check that the automaton is generating inputs as expected you can use the test binary housed in src/gramfuzz-mutator

./test SanityCheck <automaton_file>

Eg. ./test SanityCheck ~/grammars/ruby/source_automata.json