openssl-wasm

What is this?

This repository holds the source files and generated WebAssembly (WASM) output for OpenSSL compiled to WASM.

Versioning

The versions here are linked to OpenSSL versions, so if you require('openssl-wasm') and get OpenSSL 3.1.0, but you want OpenSSL 1.1.1 then you should install that with npm install openssl-wasm@1.1.1

Getting Started

The following assumes that you are working in a bash terminal with docker installed and available.

1. Build the openssl-wasm docker image
   • Run ./src/build-image.sh
   • The image expects a volume to be mounted at /WASM
2. Build a specific version of OpenSSL
   • Run docker run openssl-wasm OpenSSL_1_1_1-stable if you want to build OpenSSL_1_1_1-stable
   • You can use any tag or branch from the OpenSSL GitHub repo
3. Build all OpenSSL tags and branches
   • Run ./src/build-all-tags.sh
   • It takes a while

How does it work?

tldr; it uses empscripten to build the specified OpenSSL tag or branch in a container, and the WASM output is written to a mounted volume (a local folder).

1. The Dockerfile
   • Installs dependencies
   • Installs emscripten SDK (emsdk)
   • Clones the OpenSSL repo into the image
   • Copies the build script (./src/docker/emscripten.sh) on build
2. The openssl-wasm image
   • Will git checkout the given a tag or branch name
   • Configure emsdk and build tooling
   • Builds OpenSSL using emmake make
   • Copies the output to the mounted volume/folder
3. The *.wasm output
   • Should be copied to a local folder
   • Should have an openssl.js file (Module) to load the WebAssembly
   • Should have an openssl.wasm file which is the WebAssembly version of OpenSSL

Using it

You can this directly from javascript using node or even in the web-browser, we use the default emscripten settings so that it targets as many platforms as possible and should be usable with wasm2js

First install this library

npm install openssl-wasm

Then you can start with something like this:

import opensslWASM from 'openssl-wasm';

const module = {
	print: function (text) {
		console.log(`stdout: ${text}`);
	},
	printErr: function (text) {
		console.error(`stderr: ${text}`);
	}
};

(async () => {
	const openSSL = await opensslWASM(module);
	await openSSL.callMain(['version']);
})().catch((errorDetail) => {
	console.error(`stderr: ${errorDetail}`);
});

Typescript

If you're looking for an easy, drop-in Typescript ambient module, then you can use something like the following, but you'll need to install @types/emscripten first.

declare module 'openssl-wasm' {
	import { EmscriptenModule, EmscriptenModuleFactory } from '@types/emscripten';

	interface CallMain extends EmscriptenModule {
		ccall: typeof ccall;
		callMain: typeof ccall;
	}

	function opensslWASM(module: EmscriptenModule<CallMain>): EmscriptenModuleFactory<CallMain>;

	export default opensslWASM;
}