Wassail

wassail (WebAssembly static analyzer and inspection library) is a toolkit to perform both lightweight and heavyweight static analysis of WebAssembly modules.

• Web version
• Installation
• Usage
• Contributing

Web version

Parts of Wassail can be run in your web browser here.

Installation

0. Install opam

1. Run opam install core_unix

2. Run opam install .

Usage

Wassail can perform a number of tasks on WebAssembly modules, both in their textual representation (.wat files) or in their binary representation (.wasm)

Listing imports

$ wassail imports foo.wasm
0	time	i32 -> i32
1	ctime	i32 -> i32
2	roundf	f32 -> f32
...

Listing exports

$ wassail exports foo.wasm
11563	atof	i32 -> f64
11586	strlen	i32 -> i32
11483	fopen	i32, i32 -> i32
...

Listing section sizes

Section sizes are reported in bytes.

$ wassail sizes foo.wasm
1962	type
8724	import
13120	func
0	table
0	memory
23	global
1316	export
0	start
9480	elem
2063620	code
507825	data

Generating Call Graphs

To generate the call graph for a module foo.dot:

$ wassail callgraph benchmarks/benchmarksgame/fankuchredux.wat foo.dot

Output graph:

Generating Control-Flow Graphs

You can either generate a single CFG, for example to generate the CFG of function 1 from file foo.wat into foo.dot:

$ wassail cfg foo.wasm 1 foo.dot

Or you can generate all CFGs in a given directory:

$ wassail cfgs foo.wat out/

Example output:

Contributing

Contributions are welcome! Wassail is licensed under the conditions of the GPLv3.0 license with a non-commercial usage clause.

Running the tests

$ make test

Using the web interface

You can access the web interface here, or compile it for yourself as follows:

$ opam install js_of_ocaml js_of_ocaml-ppx
$ make js
$ open js/index.html

References

The following publications use Wassail:

• Compositional Information Flow Analysis for WebAssembly Programs, SCAM 2020. (pdf, video)
• Wassail: A WebAssembly Static Analysis Library, ProWeb 2021.
• Static Stack-Preserving Intra-Procedural Slicing of WebAssembly Binaries, ICSE 2022.
• Dynamic Slicing of WebAssembly Binaries, ICSME 2023.