fuzzing-python

Python Fuzzing Skill

Setting up fuzzing for a Python project

Fuzz testing for Python projects are Atheris. Atheris is a coverage-guided Python fuzzing engine. It supports fuzzing of Python code, but also native extensions written for CPython. Atheris is based off of libFuzzer. When fuzzing native code, Atheris can be used in combination with Address Sanitizer or Undefined Behavior Sanitizer to catch extra bugs.

You can install prebuilt versions of Atheris with pip:

pip3 install atheris

These wheels come with a built-in libFuzzer, which is fine for fuzzing Python code. If you plan to fuzz native extensions, you may need to build from source to ensure the libFuzzer version in Atheris matches your Clang version.

Using Atheris

Example

#!/usr/bin/python3

import atheris

with atheris.instrument_imports():
  import some_library
  import sys

def TestOneInput(data):
  some_library.parse(data)

atheris.Setup(sys.argv, TestOneInput)
atheris.Fuzz()

When fuzzing Python, Atheris will report a failure if the Python code under test throws an uncaught exception.

Python coverage