tauri/core/tauri-utils/src/pattern/isolation.js

// Copyright 2019-2021 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

/**
 * IMPORTANT: See ipc.js for the main frame implementation.
 * main frame -> isolation frame = isolation payload
 * isolation frame -> main frame = isolation message
 */

;(async function () {
  /**
   * Sends the message to the isolation frame.
   * @param {any} message
   */
  function sendMessage(message) {
    window.parent.postMessage(message, '*')
  }

  /**
   * @type {Uint8Array} - Injected by Tauri during runtime
   */
  const aesGcmKeyRaw = new Uint8Array(__TEMPLATE_runtime_aes_gcm_key__)

  /**
   * @type {CryptoKey}
   */
  const aesGcmKey = await window.crypto.subtle.importKey(
    'raw',
    aesGcmKeyRaw,
    'AES-GCM',
    true,
    ['encrypt']
  )

  /**
   * @param {object} data
   * @return {Promise<{nonce: number[], payload: number[]}>}
   */
  async function encrypt(data) {
    let algorithm = Object.create(null)
    algorithm.name = 'AES-GCM'
    algorithm.iv = window.crypto.getRandomValues(new Uint8Array(12))

    let encoder = new TextEncoder()
    let payloadRaw = encoder.encode(JSON.stringify(data))

    return window.crypto.subtle
      .encrypt(algorithm, aesGcmKey, payloadRaw)
      .then((payload) => {
        let result = Object.create(null)
        result.nonce = Array.from(new Uint8Array(algorithm.iv))
        result.payload = Array.from(new Uint8Array(payload))
        return result
      })
  }

  /**
   * Detect if a message event is a valid isolation payload.
   *
   * @param {MessageEvent<object>} event - a message event that is expected to be an isolation payload
   * @return boolean
   */
  function isIsolationPayload(event) {
    return (
      typeof event.data === 'object' &&
      'callback' in event.data &&
      'error' in event.data
    )
  }

  /**
   * Handle incoming payload events.
   * @param {MessageEvent<any>} event
   */
  async function payloadHandler(event) {
    if (!isIsolationPayload(event)) {
      return
    }

    let data = event.data

    if (typeof window.__TAURI_ISOLATION_HOOK__ === 'function') {
      // await even if it's not async so that we can support async ones
      data = await window.__TAURI_ISOLATION_HOOK__(data)
    }

    const encrypted = await encrypt(data)
    sendMessage(encrypted)
  }

  window.addEventListener('message', payloadHandler, false)

  /**
   * @type {number} - How many milliseconds to wait between ready checks
   */
  const readyIntervalMs = 50

  /**
   * Wait until this Isolation context is ready to receive messages, and let the main frame know.
   */
  function waitUntilReady() {
    // consider either a function or an explicitly set null value as the ready signal
    if (
      typeof window.__TAURI_ISOLATION_HOOK__ === 'function' ||
      window.__TAURI_ISOLATION_HOOK__ === null
    ) {
      sendMessage('__TAURI_ISOLATION_READY__')
    } else {
      setTimeout(waitUntilReady, readyIntervalMs)
    }
  }

  setTimeout(waitUntilReady, readyIntervalMs)
})()