73 releases (21 breaking)
0.219.1 | Oct 10, 2024 |
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0.218.0 | Sep 30, 2024 |
0.215.0 | Jul 31, 2024 |
0.202.0 | Mar 26, 2024 |
0.2.1 | Feb 17, 2022 |
#564 in WebAssembly
52,806 downloads per month
Used in 2 crates
2MB
46K
SLoC
wasm-mutate
A Bytecode Alliance project
wasm-mutate is a new tool for fuzzing Wasm compilers, runtimes, validators, and other Wasm-consuming programs.
Usage
Add wasm-mutate
to your Cargo.toml
:
$ cargo add wasm-mutate
You can also mutate a WebAssembly binary by using the cli tool:
wasm-tools mutate original.wasm --seed 0 -o out.wasm --preserve-semantics
Features
-
semantically equivalent transformations:
wasm-mutate
has the ability to only apply semantics-preserving changes to the input Wasm module. When it is used in this mode, the mutated Wasm computes identical results when given the same inputs as the original Wasm module. -
determinism:
wasm-mutate
is deterministic, i.e., given the same input Wasm module and the same seed, it always produces the same mutated output Wasm module. -
libfuzzer integration:
wasm-mutate
integrates well with mutation-based fuzzers like libFuzzer. It reuses the fuzzer's raw input strings.wasm-mutate
works with theLLVMFuzzerCustomMutator
hook and thelibfuzzer_sys::fuzz_mutator!
macro.Example
#![no_main] use libfuzzer_sys::{fuzz_mutator, fuzz_target}; use std::io::{BufRead, Read, Write}; use wasmparser::WasmFeatures; fuzz_target!(|bytes: &[u8]| { // Initialize the Wasm for example }); fuzz_mutator!(|data: &mut [u8], size: usize, max_size: usize, seed: u32| { // Generate a random Wasm module with `wasm-smith` as well as a RNG seed for let wasm = &data[..size]; let features = WasmFeatures::default(); let mut validator = wasmparser::Validator::new(); validator.wasm_features(features); let validation_result = validator.validate_all(&wasm); // Mutate the data if its a valid Wasm file, otherwise, create a random one let wasm = if validation_result.is_ok() { wasm.to_vec() } else { let (w, _) = match wasm_tools_fuzz::generate_valid_module_from_seed(seed, |config, u| { config.exceptions_enabled = false; config.simd_enabled = false; config.reference_types_enabled = false; config.memory64_enabled = false; config.max_memories = 1; Ok(()) }) { Ok(m) => m, Err(_) => { return size; } }; w }; let mutated_wasm = wasm_mutate::WasmMutate::default() .seed(seed.into()) .fuel(1000) .preserve_semantics(true) .run(&wasm); let mutated_wasm = match mutated_wasm { Ok(w) => w, Err(_) => wasm, }; // The mutated Wasm should still be valid, since the input Wasm was valid. let newsize = mutated_wasm.len(); data[..newsize].copy_from_slice(&mutated_wasm[..newsize]); newsize });
-
test case reduction (WIP):
wasm-mutate
can have the ability to restrict mutations to only those that shrink the size of the Wasm module. If it is used in this mode,wasm-mutate
essentially becomes a Wasm test-case reducer. We are currently working to provide a prototype of this feature as a separate binary. The following pseudo-Rust provides the general picture of it as an standard hill-climbing algorithm.let wasmmutate = wasm_mutate::WasmMutate::default() .seed(seed) .fuel(1000) .preserve_semantics(true) .reduce(true); while MAX_ITERATIONS > 0 { let new_wasm = wasmmutate.run(&wasm); wasm = if check_equivalence(new_wasm, wasm) { wasm } else{ panic!("No valid transformations") } MAX_ITERATIONS -= 1; } return wasm
License
This project is licensed under the Apache 2.0 license with the LLVM exception. See LICENSE for more details.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.
Special contribution
- Javier Cabrera Arteaga (Phd. student at KTH)
Dependencies
~1.9–2.8MB
~53K SLoC