guest-window-manager.js

'use strict';

const electron = require('electron');
const { BrowserWindow } = electron;
const { isSameOrigin } = process.electronBinding('v8_util');
const { ipcMainInternal } = require('@electron/internal/browser/ipc-main-internal');
const ipcMainUtils = require('@electron/internal/browser/ipc-main-internal-utils');
const parseFeaturesString = require('@electron/internal/common/parse-features-string');

const hasProp = {}.hasOwnProperty;
const frameToGuest = new Map();

// Security options that child windows will always inherit from parent windows
const inheritedWebPreferences = new Map([
  ['contextIsolation', true],
  ['javascript', false],
  ['nativeWindowOpen', true],
  ['nodeIntegration', false],
  ['enableRemoteModule', false],
  ['sandbox', true],
  ['webviewTag', false],
  ['nodeIntegrationInSubFrames', false]
]);

// Copy attribute of |parent| to |child| if it is not defined in |child|.
const mergeOptions = function (child, parent, visited) {
  // Check for circular reference.
  if (visited == null) visited = new Set();
  if (visited.has(parent)) return;

  visited.add(parent);
  for (const key in parent) {
    if (key === 'type') continue;
    if (!hasProp.call(parent, key)) continue;
    if (key in child && key !== 'webPreferences') continue;

    const value = parent[key];
    if (typeof value === 'object' && !Array.isArray(value)) {
      child[key] = mergeOptions(child[key] || {}, value, visited);
    } else {
      child[key] = value;
    }
  }
  visited.delete(parent);

  return child;
};

// Merge |options| with the |embedder|'s window's options.
const mergeBrowserWindowOptions = function (embedder, options) {
  if (options.webPreferences == null) {
    options.webPreferences = {};
  }
  if (embedder.browserWindowOptions != null) {
    let parentOptions = embedder.browserWindowOptions;

    // if parent's visibility is available, that overrides 'show' flag (#12125)
    const win = BrowserWindow.fromWebContents(embedder.webContents);
    if (win != null) {
      parentOptions = { ...embedder.browserWindowOptions, show: win.isVisible() };
    }

    // Inherit the original options if it is a BrowserWindow.
    mergeOptions(options, parentOptions);
  } else {
    // Or only inherit webPreferences if it is a webview.
    mergeOptions(options.webPreferences, embedder.getLastWebPreferences());
  }

  // Inherit certain option values from parent window
  const webPreferences = embedder.getLastWebPreferences();
  for (const [name, value] of inheritedWebPreferences) {
    if (webPreferences[name] === value) {
      options.webPreferences[name] = value;
    }
  }

  if (!webPreferences.nativeWindowOpen) {
    // Sets correct openerId here to give correct options to 'new-window' event handler
    options.webPreferences.openerId = embedder.id;
  }

  return options;
};

// Setup a new guest with |embedder|
const setupGuest = function (embedder, frameName, guest, options) {
  // When |embedder| is destroyed we should also destroy attached guest, and if
  // guest is closed by user then we should prevent |embedder| from double
  // closing guest.
  const guestId = guest.webContents.id;
  const closedByEmbedder = function () {
    guest.removeListener('closed', closedByUser);
    guest.destroy();
  };
  const closedByUser = function () {
    embedder._sendInternal('ELECTRON_GUEST_WINDOW_MANAGER_WINDOW_CLOSED_' + guestId);
    embedder.removeListener('current-render-view-deleted', closedByEmbedder);
  };
  embedder.once('current-render-view-deleted', closedByEmbedder);
  guest.once('closed', closedByUser);
  if (frameName) {
    frameToGuest.set(frameName, guest);
    guest.frameName = frameName;
    guest.once('closed', function () {
      frameToGuest.delete(frameName);
    });
  }
  return guestId;
};

// Create a new guest created by |embedder| with |options|.
const createGuest = function (embedder, url, referrer, frameName, options, postData) {
  let guest = frameToGuest.get(frameName);
  if (frameName && (guest != null)) {
    guest.loadURL(url);
    return guest.webContents.id;
  }

  // Remember the embedder window's id.
  if (options.webPreferences == null) {
    options.webPreferences = {};
  }

  guest = new BrowserWindow(options);
  if (!options.webContents) {
    // We should not call `loadURL` if the window was constructed from an
    // existing webContents (window.open in a sandboxed renderer).
    //
    // Navigating to the url when creating the window from an existing
    // webContents is not necessary (it will navigate there anyway).
    const loadOptions = {
      httpReferrer: referrer
    };
    if (postData != null) {
      loadOptions.postData = postData;
      loadOptions.extraHeaders = 'content-type: application/x-www-form-urlencoded';
      if (postData.length > 0) {
        const postDataFront = postData[0].bytes.toString();
        const boundary = /^--.*[^-\r\n]/.exec(postDataFront);
        if (boundary != null) {
          loadOptions.extraHeaders = `content-type: multipart/form-data; boundary=${boundary[0].substr(2)}`;
        }
      }
    }
    guest.loadURL(url, loadOptions);
  }

  return setupGuest(embedder, frameName, guest, options);
};

const getGuestWindow = function (guestContents) {
  let guestWindow = BrowserWindow.fromWebContents(guestContents);
  if (guestWindow == null) {
    const hostContents = guestContents.hostWebContents;
    if (hostContents != null) {
      guestWindow = BrowserWindow.fromWebContents(hostContents);
    }
  }
  if (!guestWindow) {
    throw new Error('getGuestWindow failed');
  }
  return guestWindow;
};

const isChildWindow = function (sender, target) {
  return target.getLastWebPreferences().openerId === sender.id;
};

const isRelatedWindow = function (sender, target) {
  return isChildWindow(sender, target) || isChildWindow(target, sender);
};

const isScriptableWindow = function (sender, target) {
  return isRelatedWindow(sender, target) && isSameOrigin(sender.getURL(), target.getURL());
};

const isNodeIntegrationEnabled = function (sender) {
  return sender.getLastWebPreferences().nodeIntegration === true;
};

// Checks whether |sender| can access the |target|:
const canAccessWindow = function (sender, target) {
  return isChildWindow(sender, target) ||
         isScriptableWindow(sender, target) ||
         isNodeIntegrationEnabled(sender);
};

// Routed window.open messages with raw options
ipcMainInternal.on('ELECTRON_GUEST_WINDOW_MANAGER_WINDOW_OPEN', (event, url, frameName, features) => {
  // This should only be allowed for senders that have nativeWindowOpen: false
  {
    const webPreferences = event.sender.getLastWebPreferences();
    if (webPreferences.nativeWindowOpen || webPreferences.sandbox) {
      event.returnValue = null;
      throw new Error('GUEST_WINDOW_MANAGER_WINDOW_OPEN denied: expected native window.open');
    }
  }
  if (url == null || url === '') url = 'about:blank';
  if (frameName == null) frameName = '';
  if (features == null) features = '';

  const options = {};

  const ints = ['x', 'y', 'width', 'height', 'minWidth', 'maxWidth', 'minHeight', 'maxHeight', 'zoomFactor'];
  const webPreferences = ['zoomFactor', 'nodeIntegration', 'enableRemoteModule', 'javascript', 'contextIsolation', 'webviewTag'];
  const disposition = 'new-window';

  // Used to store additional features
  const additionalFeatures = [];

  // Parse the features
  parseFeaturesString(features, function (key, value) {
    if (value === undefined) {
      additionalFeatures.push(key);
    } else {
      // Don't allow webPreferences to be set since it must be an object
      // that cannot be directly overridden
      if (key === 'webPreferences') return;

      if (webPreferences.includes(key)) {
        if (options.webPreferences == null) {
          options.webPreferences = {};
        }
        options.webPreferences[key] = value;
      } else {
        options[key] = value;
      }
    }
  });
  if (options.left) {
    if (options.x == null) {
      options.x = options.left;
    }
  }
  if (options.top) {
    if (options.y == null) {
      options.y = options.top;
    }
  }
  if (options.title == null) {
    options.title = frameName;
  }
  if (options.width == null) {
    options.width = 800;
  }
  if (options.height == null) {
    options.height = 600;
  }

  for (const name of ints) {
    if (options[name] != null) {
      options[name] = parseInt(options[name], 10);
    }
  }

  const referrer = { url: '', policy: 'default' };
  internalWindowOpen(event, url, referrer, frameName, disposition, options, additionalFeatures);
});

// Routed window.open messages with fully parsed options
function internalWindowOpen (event, url, referrer, frameName, disposition, options, additionalFeatures, postData) {
  options = mergeBrowserWindowOptions(event.sender, options);
  event.sender.emit('new-window', event, url, frameName, disposition, options, additionalFeatures, referrer);
  const { newGuest } = event;
  if ((event.sender.getType() === 'webview' && event.sender.getLastWebPreferences().disablePopups) || event.defaultPrevented) {
    if (newGuest != null) {
      if (options.webContents === newGuest.webContents) {
        // the webContents is not changed, so set defaultPrevented to false to
        // stop the callers of this event from destroying the webContents.
        event.defaultPrevented = false;
      }
      event.returnValue = setupGuest(event.sender, frameName, newGuest, options);
    } else {
      event.returnValue = null;
    }
  } else {
    event.returnValue = createGuest(event.sender, url, referrer, frameName, options, postData);
  }
}

const handleMessage = function (channel, handler) {
  ipcMainUtils.handle(channel, (event, guestId, ...args) => {
    // Access webContents via electron to prevent circular require.
    const guestContents = electron.webContents.fromId(guestId);
    if (!guestContents) {
      throw new Error(`Invalid guestId: ${guestId}`);
    }

    return handler(event, guestContents, ...args);
  });
};

const securityCheck = function (contents, guestContents, check) {
  if (!check(contents, guestContents)) {
    console.error(`Blocked ${contents.getURL()} from accessing guestId: ${guestContents.id}`);
    throw new Error(`Access denied to guestId: ${guestContents.id}`);
  }
};

const windowMethods = new Set([
  'destroy',
  'focus',
  'blur'
]);

handleMessage('ELECTRON_GUEST_WINDOW_MANAGER_WINDOW_METHOD', (event, guestContents, method, ...args) => {
  securityCheck(event.sender, guestContents, canAccessWindow);

  if (!windowMethods.has(method)) {
    console.error(`Blocked ${event.sender.getURL()} from calling method: ${method}`);
    throw new Error(`Invalid method: ${method}`);
  }

  return getGuestWindow(guestContents)[method](...args);
});

handleMessage('ELECTRON_GUEST_WINDOW_MANAGER_WINDOW_POSTMESSAGE', (event, guestContents, message, targetOrigin, sourceOrigin) => {
  if (targetOrigin == null) {
    targetOrigin = '*';
  }

  // The W3C does not seem to have word on how postMessage should work when the
  // origins do not match, so we do not do |canAccessWindow| check here since
  // postMessage across origins is useful and not harmful.
  securityCheck(event.sender, guestContents, isRelatedWindow);

  if (targetOrigin === '*' || isSameOrigin(guestContents.getURL(), targetOrigin)) {
    const sourceId = event.sender.id;
    guestContents._sendInternal('ELECTRON_GUEST_WINDOW_POSTMESSAGE', sourceId, message, sourceOrigin);
  }
});

const webContentsMethods = new Set([
  'getURL',
  'loadURL',
  'executeJavaScript',
  'print'
]);

handleMessage('ELECTRON_GUEST_WINDOW_MANAGER_WEB_CONTENTS_METHOD', (event, guestContents, method, ...args) => {
  securityCheck(event.sender, guestContents, canAccessWindow);

  if (!webContentsMethods.has(method)) {
    console.error(`Blocked ${event.sender.getURL()} from calling method: ${method}`);
    throw new Error(`Invalid method: ${method}`);
  }

  return guestContents[method](...args);
});

exports.internalWindowOpen = internalWindowOpen;