Proposal crypto's KeyObject interaction with worker_threads.

README.md

Proposal

crypto's KeyObject interaction with worker_threads

• (required) when KeyObject instances are part of the message (it would be okay if they also had to be put in transferList) they get transmitted as KeyObject instances
• (optional) the KeyObject instance remains the same object in the worker thread when passed again

index.js

const { Worker, isMainThread, parentPort } = require('worker_threads')
const crypto = require('crypto')
const { promisify } = require('util')
const { strict: assert } = require('assert')

const generateKeyPair = promisify(crypto.generateKeyPair)

if (isMainThread) {
  const tasks = new Map()
  let worker
  let taskId = 0

  const spawn = () => {
    worker = new Worker(__filename)
    worker.on('message', function ({ id, signature }) {
      const task = tasks.get(id)
      tasks.delete(id)
      if (tasks.size === 0) worker.unref()
      task(signature)
    })
  }

  const sign = (algorithm, data, key) => new Promise((resolve) => {
    const id = taskId++
    tasks.set(id, resolve)
    if (worker === undefined) spawn()
    worker.ref()
    worker.postMessage({ id, algorithm, data, key })
  })

  ;(async () => {
    const { privateKey } = await generateKeyPair('ec', { namedCurve: 'secp256k1' })
    const algorithm = 'sha256'

    console.log(await sign(algorithm, Buffer.from('foo'), privateKey))
    console.log(await sign(algorithm, Buffer.from('bar'), privateKey))
  })().catch((err) => {
    process.exitCode = 1
    if (worker) worker.unref()
    console.error(err)
  })
} else {
  const { sign, KeyObject } = crypto

  let inst

  parentPort.on('message', ({ id, algorithm, data, key }) => {
    // required
    assert.ok(key instanceof KeyObject, 'expect key to be an instance of KeyObject')
    
    // optional
    {
      if (!inst) {
        inst = key
      }
      assert.equal(inst, key) // this will pass on task id 0 but fail on task id 1
    }

    parentPort.postMessage({ id, signature: sign(algorithm, data, key) })
  })
}