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dictionaries | ||
fuzz_csv_reader_corpus | ||
fuzz_json_loads_corpus | ||
fuzz_sre_compile_corpus | ||
fuzz_struct_unpack_corpus | ||
_xxtestfuzz.c | ||
fuzz_tests.txt | ||
fuzzer.c | ||
README.rst |
Fuzz Tests for CPython ====================== These fuzz tests are designed to be included in Google's `oss-fuzz`_ project. oss-fuzz works against a library exposing a function of the form ``int LLVMFuzzerTestOneInput(const uint8_t* data, size_t length)``. We provide that library (``fuzzer.c``), and include a ``_fuzz`` module for testing with some toy values -- no fuzzing occurs in Python's test suite. oss-fuzz will regularly pull from CPython, discover all the tests in ``fuzz_tests.txt``, and run them -- so adding a new test here means it will automatically be run in oss-fuzz, while also being smoke-tested as part of CPython's test suite. Adding a new fuzz test ---------------------- Add the test name on a new line in ``fuzz_tests.txt``. In ``fuzzer.c``, add a function to be run:: int $test_name (const char* data, size_t size) { ... return 0; } And invoke it from ``LLVMFuzzerTestOneInput``:: #if _Py_FUZZ_YES(fuzz_builtin_float) rv |= _run_fuzz(data, size, fuzz_builtin_float); #endif ``LLVMFuzzerTestOneInput`` will run in oss-fuzz, with each test in ``fuzz_tests.txt`` run separately. Seed data (corpus) for the test can be provided in a subfolder called ``<test_name>_corpus`` such as ``fuzz_json_loads_corpus``. A wide variety of good input samples allows the fuzzer to more easily explore a diverse set of paths and provides a better base to find buggy input from. Dictionaries of tokens (see oss-fuzz documentation for more details) can be placed in the ``dictionaries`` folder with the name of the test. For example, ``dictionaries/fuzz_json_loads.dict`` contains JSON tokens to guide the fuzzer. What makes a good fuzz test --------------------------- Libraries written in C that might handle untrusted data are worthwhile. The more complex the logic (e.g. parsing), the more likely this is to be a useful fuzz test. See the existing examples for reference, and refer to the `oss-fuzz`_ docs. .. _oss-fuzz: https://github.com/google/oss-fuzz