41eb225765
* Add the instance allocation strategy to generated fuzzing configs. This commit adds support for generating configs with arbitrary instance allocation strategies. With this, the pooling allocator will be fuzzed as part of the existing fuzz targets. * Refine maximum constants for arbitrary module limits. * Add an `instantiate-many` fuzz target. This commit adds a new `instantiate-many` fuzz target that will attempt to instantiate and terminate modules in an arbitrary order. It generates up to 5 modules, from which a random sequence of instances will be created. The primary benefactor of this fuzz target is the pooling instance allocator. * Allow no aliasing in generated modules when using the pooling allocator. This commit prevents aliases in the generated modules as they might count against the configured import limits of the pooling allocator. As the existing module linking proposal implementation will eventually be deprecated in favor of the component model proposal, it isn't very important that we test aliases in generated modules with the pooling allocator. * Improve distribution of memory config in fuzzing. The previous commit attempted to provide a 32-bit upper bound to 64-bit arbitrary values, which skewed the distribution heavily in favor of the upper bound. This commit removes the constraint and instead uses arbitrary 32-bit values that are converted to 64-bit values in the `Arbitrary` implementation.
cargo fuzz Targets for Wasmtime
This crate defines various libFuzzer
fuzzing targets for Wasmtime, which can be run via cargo fuzz.
These fuzz targets just glue together pre-defined test case generators with
oracles and pass libFuzzer-provided inputs to them. The test case generators and
oracles themselves are independent from the fuzzing engine that is driving the
fuzzing process and are defined in wasmtime/crates/fuzzing.
Example
To start fuzzing run the following command, where $MY_FUZZ_TARGET is one of
the available fuzz targets:
cargo fuzz run $MY_FUZZ_TARGET
Available Fuzz Targets
At the time of writing, we have the following fuzz targets:
compile: Attempt to compile libFuzzer's raw input bytes with Wasmtime.instantiate: Attempt to compile and instantiate libFuzzer's raw input bytes with Wasmtime.instantiate_translated: Pass libFuzzer's input bytes towasm-opt -ttfto generate a random, valid Wasm module, and then attempt to instantiate it.
The canonical list of fuzz targets is the .rs files in the fuzz_targets
directory:
ls wasmtime/fuzz/fuzz_targets/
Corpora
While you can start from scratch, libFuzzer will work better if it is given a corpus of seed inputs to kick start the fuzzing process. We maintain a corpus for each of these fuzz targets in a dedicated repo on github.
You can use our corpora by cloning it and placing it at wasmtime/fuzz/corpus:
git clone \
https://github.com/bytecodealliance/wasmtime-libfuzzer-corpus.git \
wasmtime/fuzz/corpus