extension/src/content/index.js

// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

var debug = require('debug')('content-script:index');

var pageEventProxy = require('./event-proxy');
var random = require('../../../src/lib/random');

// Port to communicate with background js.
// One content script runs per iframe / tabs so there may be multiple ports
// per page.
var _backgroundPort;
function getBackgroundPort() {
  // Lazily connect to background port.
  if (!_backgroundPort) {
    _backgroundPort = chrome.runtime.connect();
    _backgroundPort.onMessage.addListener(backgroundPageMessageForwarder);
  }
  return _backgroundPort;
}

// We generate and send different instanceIds to the background page than those
// coming from the web app. This prevents the web app from intentionally
// colliding with instanceIds from apps on other tabs. The two maps below are
// used to map between the two instanceIds.
var backgroundToPage = {};
var pageToBackground = {};

// If the plug-in crashed, the state of the connected Vanadium instances
// are invalid. We will block any further messages.
var invalidated = false;

// Whitelist of message types to allow from the web app.
var messageTypeWhitelist = [
  'auth',
  'browsprCleanup',
  'browsprMsg',
  'createInstance'
];
if (process.env.ALLOW_INTENTIONAL_CRASH) {
  messageTypeWhitelist.push('intentionallyPanic');
}

function isAllowedMessage(type) {
  return messageTypeWhitelist.indexOf(type) >= 0;
}

// Forward messages from the webApp to the background page.
pageEventProxy.onAny(function(body) {
  if (invalidated && !process.env.ALLOW_INTENTIONAL_CRASH) {
    pageEventProxy.send('error', 'Refusing to send Vanadium message. ' +
      'Plug-in crashed and page must be reloaded.');
    return;
  }

  // 'this' is bound to event emitter2 instance, which sets 'this.event' to the
  // type of the event.
  var type = this.event;
  debug('content script received message of type', type, 'from page:', body);

  if (!isAllowedMessage(type)) {
    var err = new Error('Ignoring message with unknown type: ' + type);
    console.error(err);
    pageEventProxy.send('error', { message: err.message });
    return;
  }

  // Swap the instanceId with a generated one.
  if (body && body.instanceId) {
    var outgoingInstanceId = pageToBackground[body.instanceId] ||
        random.int32();
    pageToBackground[body.instanceId] = outgoingInstanceId;
    backgroundToPage[outgoingInstanceId] = body.instanceId;
    body.instanceId = outgoingInstanceId;
  }

  try {
    getBackgroundPort().postMessage({
      type: this.event,
      body: body
    });
  } catch (err) {
    pageEventProxy.send('error', 'Error posting message, ' +
          'you may need to reload this tab. ' + err);
  }
});

// Forward any messages from the background page to the webApp.
function backgroundPageMessageForwarder(msg) {
  debug('content script received message of type', msg.type,
    'from background script:', msg.body);

  if (msg.type === 'crash') {
    // Block any future messages, as we don't currently have a way to
    // be sure the response will be correct.
    invalidated = true;

    pageEventProxy.send('crash', msg.body);

    return;
  }

  // Swap the instanceId with the original one.
  if (msg.instanceId) {
    msg.instanceId = backgroundToPage[msg.instanceId];
  }

  pageEventProxy.send(msg.type, msg);
}

debug('content script loaded');