electron/lib/browser/rpc-server.js

'use strict';

const electron = require('electron');
const { EventEmitter } = require('events');
const fs = require('fs');

const v8Util = process.electronBinding('v8_util');
const eventBinding = process.electronBinding('event');
const clipboard = process.electronBinding('clipboard');
const features = process.electronBinding('features');

const { getContentScripts } = require('@electron/internal/browser/chrome-extension');
const { crashReporterInit } = require('@electron/internal/browser/crash-reporter-init');
const { ipcMainInternal } = require('@electron/internal/browser/ipc-main-internal');
const ipcMainUtils = require('@electron/internal/browser/ipc-main-internal-utils');
const objectsRegistry = require('@electron/internal/browser/objects-registry');
const guestViewManager = require('@electron/internal/browser/guest-view-manager');
const bufferUtils = require('@electron/internal/common/buffer-utils');
const errorUtils = require('@electron/internal/common/error-utils');
const typeUtils = require('@electron/internal/common/type-utils');
const { isPromise } = require('@electron/internal/common/is-promise');

const hasProp = {}.hasOwnProperty;

// The internal properties of Function.
const FUNCTION_PROPERTIES = [
  'length', 'name', 'arguments', 'caller', 'prototype'
];

// The remote functions in renderer processes.
// id => Function
const rendererFunctions = v8Util.createDoubleIDWeakMap();

// Return the description of object's members:
const getObjectMembers = function (object) {
  let names = Object.getOwnPropertyNames(object);
  // For Function, we should not override following properties even though they
  // are "own" properties.
  if (typeof object === 'function') {
    names = names.filter((name) => {
      return !FUNCTION_PROPERTIES.includes(name);
    });
  }
  // Map properties to descriptors.
  return names.map((name) => {
    const descriptor = Object.getOwnPropertyDescriptor(object, name);
    const member = { name, enumerable: descriptor.enumerable, writable: false };
    if (descriptor.get === undefined && typeof object[name] === 'function') {
      member.type = 'method';
    } else {
      if (descriptor.set || descriptor.writable) member.writable = true;
      member.type = 'get';
    }
    return member;
  });
};

// Return the description of object's prototype.
const getObjectPrototype = function (object) {
  const proto = Object.getPrototypeOf(object);
  if (proto === null || proto === Object.prototype) return null;
  return {
    members: getObjectMembers(proto),
    proto: getObjectPrototype(proto)
  };
};

// Convert a real value into meta data.
const valueToMeta = function (sender, contextId, value, optimizeSimpleObject = false) {
  // Determine the type of value.
  const meta = { type: typeof value };
  if (meta.type === 'object') {
    // Recognize certain types of objects.
    if (value === null) {
      meta.type = 'value';
    } else if (bufferUtils.isBuffer(value)) {
      meta.type = 'buffer';
    } else if (Array.isArray(value)) {
      meta.type = 'array';
    } else if (value instanceof Error) {
      meta.type = 'error';
    } else if (value instanceof Date) {
      meta.type = 'date';
    } else if (isPromise(value)) {
      meta.type = 'promise';
    } else if (hasProp.call(value, 'callee') && value.length != null) {
      // Treat the arguments object as array.
      meta.type = 'array';
    } else if (optimizeSimpleObject && v8Util.getHiddenValue(value, 'simple')) {
      // Treat simple objects as value.
      meta.type = 'value';
    }
  }

  // Fill the meta object according to value's type.
  if (meta.type === 'array') {
    meta.members = value.map((el) => valueToMeta(sender, contextId, el, optimizeSimpleObject));
  } else if (meta.type === 'object' || meta.type === 'function') {
    meta.name = value.constructor ? value.constructor.name : '';

    // Reference the original value if it's an object, because when it's
    // passed to renderer we would assume the renderer keeps a reference of
    // it.
    meta.id = objectsRegistry.add(sender, contextId, value);
    meta.members = getObjectMembers(value);
    meta.proto = getObjectPrototype(value);
  } else if (meta.type === 'buffer') {
    meta.value = bufferUtils.bufferToMeta(value);
  } else if (meta.type === 'promise') {
    // Add default handler to prevent unhandled rejections in main process
    // Instead they should appear in the renderer process
    value.then(function () {}, function () {});

    meta.then = valueToMeta(sender, contextId, function (onFulfilled, onRejected) {
      value.then(onFulfilled, onRejected);
    });
  } else if (meta.type === 'error') {
    meta.members = plainObjectToMeta(value);

    // Error.name is not part of own properties.
    meta.members.push({
      name: 'name',
      value: value.name
    });
  } else if (meta.type === 'date') {
    meta.value = value.getTime();
  } else {
    meta.type = 'value';
    meta.value = value;
  }
  return meta;
};

// Convert object to meta by value.
const plainObjectToMeta = function (obj) {
  return Object.getOwnPropertyNames(obj).map(function (name) {
    return {
      name: name,
      value: obj[name]
    };
  });
};

// Convert Error into meta data.
const exceptionToMeta = function (error) {
  return {
    type: 'exception',
    value: errorUtils.serialize(error)
  };
};

const throwRPCError = function (message) {
  const error = new Error(message);
  error.code = 'EBADRPC';
  error.errno = -72;
  throw error;
};

const removeRemoteListenersAndLogWarning = (sender, callIntoRenderer) => {
  const location = v8Util.getHiddenValue(callIntoRenderer, 'location');
  let message = `Attempting to call a function in a renderer window that has been closed or released.` +
    `\nFunction provided here: ${location}`;

  if (sender instanceof EventEmitter) {
    const remoteEvents = sender.eventNames().filter((eventName) => {
      return sender.listeners(eventName).includes(callIntoRenderer);
    });

    if (remoteEvents.length > 0) {
      message += `\nRemote event names: ${remoteEvents.join(', ')}`;
      remoteEvents.forEach((eventName) => {
        sender.removeListener(eventName, callIntoRenderer);
      });
    }
  }

  console.warn(message);
};

// Convert array of meta data from renderer into array of real values.
const unwrapArgs = function (sender, frameId, contextId, args) {
  const metaToValue = function (meta) {
    switch (meta.type) {
      case 'value':
        return meta.value;
      case 'remote-object':
        return objectsRegistry.get(meta.id);
      case 'array':
        return unwrapArgs(sender, frameId, contextId, meta.value);
      case 'buffer':
        return bufferUtils.metaToBuffer(meta.value);
      case 'date':
        return new Date(meta.value);
      case 'promise':
        return Promise.resolve({
          then: metaToValue(meta.then)
        });
      case 'object': {
        const ret = {};
        Object.defineProperty(ret.constructor, 'name', { value: meta.name });

        for (const { name, value } of meta.members) {
          ret[name] = metaToValue(value);
        }
        return ret;
      }
      case 'function-with-return-value':
        const returnValue = metaToValue(meta.value);
        return function () {
          return returnValue;
        };
      case 'function': {
        // Merge contextId and meta.id, since meta.id can be the same in
        // different webContents.
        const objectId = [contextId, meta.id];

        // Cache the callbacks in renderer.
        if (rendererFunctions.has(objectId)) {
          return rendererFunctions.get(objectId);
        }

        const callIntoRenderer = function (...args) {
          let succeed = false;
          if (!sender.isDestroyed()) {
            succeed = sender._sendToFrameInternal(frameId, 'ELECTRON_RENDERER_CALLBACK', contextId, meta.id, valueToMeta(sender, contextId, args));
          }
          if (!succeed) {
            removeRemoteListenersAndLogWarning(this, callIntoRenderer);
          }
        };
        v8Util.setHiddenValue(callIntoRenderer, 'location', meta.location);
        Object.defineProperty(callIntoRenderer, 'length', { value: meta.length });

        v8Util.setRemoteCallbackFreer(callIntoRenderer, frameId, contextId, meta.id, sender);
        rendererFunctions.set(objectId, callIntoRenderer);
        return callIntoRenderer;
      }
      default:
        throw new TypeError(`Unknown type: ${meta.type}`);
    }
  };
  return args.map(metaToValue);
};

const isRemoteModuleEnabledCache = new WeakMap();

const isRemoteModuleEnabled = function (contents) {
  if (!isRemoteModuleEnabledCache.has(contents)) {
    isRemoteModuleEnabledCache.set(contents, contents._isRemoteModuleEnabled());
  }

  return isRemoteModuleEnabledCache.get(contents);
};

const handleRemoteCommand = function (channel, handler) {
  ipcMainInternal.on(channel, (event, contextId, ...args) => {
    let returnValue;
    if (!isRemoteModuleEnabled(event.sender)) {
      event.returnValue = null;
      return;
    }

    try {
      returnValue = handler(event, contextId, ...args);
    } catch (error) {
      returnValue = exceptionToMeta(error);
    }

    if (returnValue !== undefined) {
      event.returnValue = returnValue;
    }
  });
};

const emitCustomEvent = function (contents, eventName, ...args) {
  const event = eventBinding.createWithSender(contents);

  electron.app.emit(eventName, event, contents, ...args);
  contents.emit(eventName, event, ...args);

  return event;
};

handleRemoteCommand('ELECTRON_BROWSER_WRONG_CONTEXT_ERROR', function (event, contextId, passedContextId, id) {
  const objectId = [passedContextId, id];
  if (!rendererFunctions.has(objectId)) {
    // Do nothing if the error has already been reported before.
    return;
  }
  removeRemoteListenersAndLogWarning(event.sender, rendererFunctions.get(objectId));
});

handleRemoteCommand('ELECTRON_BROWSER_REQUIRE', function (event, contextId, moduleName) {
  const customEvent = emitCustomEvent(event.sender, 'remote-require', moduleName);

  if (customEvent.returnValue === undefined) {
    if (customEvent.defaultPrevented) {
      throw new Error(`Blocked remote.require('${moduleName}')`);
    } else {
      customEvent.returnValue = process.mainModule.require(moduleName);
    }
  }

  return valueToMeta(event.sender, contextId, customEvent.returnValue);
});

handleRemoteCommand('ELECTRON_BROWSER_GET_BUILTIN', function (event, contextId, moduleName) {
  const customEvent = emitCustomEvent(event.sender, 'remote-get-builtin', moduleName);

  if (customEvent.returnValue === undefined) {
    if (customEvent.defaultPrevented) {
      throw new Error(`Blocked remote.getBuiltin('${moduleName}')`);
    } else {
      customEvent.returnValue = electron[moduleName];
    }
  }

  return valueToMeta(event.sender, contextId, customEvent.returnValue);
});

handleRemoteCommand('ELECTRON_BROWSER_GLOBAL', function (event, contextId, globalName) {
  const customEvent = emitCustomEvent(event.sender, 'remote-get-global', globalName);

  if (customEvent.returnValue === undefined) {
    if (customEvent.defaultPrevented) {
      throw new Error(`Blocked remote.getGlobal('${globalName}')`);
    } else {
      customEvent.returnValue = global[globalName];
    }
  }

  return valueToMeta(event.sender, contextId, customEvent.returnValue);
});

handleRemoteCommand('ELECTRON_BROWSER_CURRENT_WINDOW', function (event, contextId) {
  const customEvent = emitCustomEvent(event.sender, 'remote-get-current-window');

  if (customEvent.returnValue === undefined) {
    if (customEvent.defaultPrevented) {
      throw new Error('Blocked remote.getCurrentWindow()');
    } else {
      customEvent.returnValue = event.sender.getOwnerBrowserWindow();
    }
  }

  return valueToMeta(event.sender, contextId, customEvent.returnValue);
});

handleRemoteCommand('ELECTRON_BROWSER_CURRENT_WEB_CONTENTS', function (event, contextId) {
  const customEvent = emitCustomEvent(event.sender, 'remote-get-current-web-contents');

  if (customEvent.returnValue === undefined) {
    if (customEvent.defaultPrevented) {
      throw new Error('Blocked remote.getCurrentWebContents()');
    } else {
      customEvent.returnValue = event.sender;
    }
  }

  return valueToMeta(event.sender, contextId, customEvent.returnValue);
});

handleRemoteCommand('ELECTRON_BROWSER_CONSTRUCTOR', function (event, contextId, id, args) {
  args = unwrapArgs(event.sender, event.frameId, contextId, args);
  const constructor = objectsRegistry.get(id);

  if (constructor == null) {
    throwRPCError(`Cannot call constructor on missing remote object ${id}`);
  }

  return valueToMeta(event.sender, contextId, new constructor(...args));
});

handleRemoteCommand('ELECTRON_BROWSER_FUNCTION_CALL', function (event, contextId, id, args) {
  args = unwrapArgs(event.sender, event.frameId, contextId, args);
  const func = objectsRegistry.get(id);

  if (func == null) {
    throwRPCError(`Cannot call function on missing remote object ${id}`);
  }

  try {
    return valueToMeta(event.sender, contextId, func(...args), true);
  } catch (error) {
    const err = new Error(`Could not call remote function '${func.name || 'anonymous'}'. Check that the function signature is correct. Underlying error: ${error.message}\nUnderlying stack: ${error.stack}\n`);
    err.cause = error;
    throw err;
  }
});

handleRemoteCommand('ELECTRON_BROWSER_MEMBER_CONSTRUCTOR', function (event, contextId, id, method, args) {
  args = unwrapArgs(event.sender, event.frameId, contextId, args);
  const object = objectsRegistry.get(id);

  if (object == null) {
    throwRPCError(`Cannot call constructor '${method}' on missing remote object ${id}`);
  }

  return valueToMeta(event.sender, contextId, new object[method](...args));
});

handleRemoteCommand('ELECTRON_BROWSER_MEMBER_CALL', function (event, contextId, id, method, args) {
  args = unwrapArgs(event.sender, event.frameId, contextId, args);
  const object = objectsRegistry.get(id);

  if (object == null) {
    throwRPCError(`Cannot call method '${method}' on missing remote object ${id}`);
  }

  try {
    return valueToMeta(event.sender, contextId, object[method](...args), true);
  } catch (error) {
    const err = new Error(`Could not call remote method '${method}'. Check that the method signature is correct. Underlying error: ${error.message}\nUnderlying stack: ${error.stack}\n`);
    err.cause = error;
    throw err;
  }
});

handleRemoteCommand('ELECTRON_BROWSER_MEMBER_SET', function (event, contextId, id, name, args) {
  args = unwrapArgs(event.sender, event.frameId, contextId, args);
  const obj = objectsRegistry.get(id);

  if (obj == null) {
    throwRPCError(`Cannot set property '${name}' on missing remote object ${id}`);
  }

  obj[name] = args[0];
  return null;
});

handleRemoteCommand('ELECTRON_BROWSER_MEMBER_GET', function (event, contextId, id, name) {
  const obj = objectsRegistry.get(id);

  if (obj == null) {
    throwRPCError(`Cannot get property '${name}' on missing remote object ${id}`);
  }

  return valueToMeta(event.sender, contextId, obj[name]);
});

handleRemoteCommand('ELECTRON_BROWSER_DEREFERENCE', function (event, contextId, id, rendererSideRefCount) {
  objectsRegistry.remove(event.sender, contextId, id, rendererSideRefCount);
});

handleRemoteCommand('ELECTRON_BROWSER_CONTEXT_RELEASE', (event, contextId) => {
  objectsRegistry.clear(event.sender, contextId);
});

handleRemoteCommand('ELECTRON_BROWSER_GUEST_WEB_CONTENTS', function (event, contextId, guestInstanceId) {
  const guest = guestViewManager.getGuestForWebContents(guestInstanceId, event.sender);

  const customEvent = emitCustomEvent(event.sender, 'remote-get-guest-web-contents', guest);

  if (customEvent.returnValue === undefined) {
    if (customEvent.defaultPrevented) {
      throw new Error(`Blocked remote.getGuestForWebContents()`);
    } else {
      customEvent.returnValue = guest;
    }
  }

  return valueToMeta(event.sender, contextId, customEvent.returnValue);
});

// Implements window.close()
ipcMainInternal.on('ELECTRON_BROWSER_WINDOW_CLOSE', function (event) {
  const window = event.sender.getOwnerBrowserWindow();
  if (window) {
    window.close();
  }
  event.returnValue = null;
});

ipcMainUtils.handle('ELECTRON_CRASH_REPORTER_INIT', function (event, options) {
  return crashReporterInit(options);
});

ipcMainUtils.handle('ELECTRON_BROWSER_GET_LAST_WEB_PREFERENCES', function (event) {
  return event.sender.getLastWebPreferences();
});

// Methods not listed in this set are called directly in the renderer process.
const allowedClipboardMethods = (() => {
  switch (process.platform) {
    case 'darwin':
      return new Set(['readFindText', 'writeFindText']);
    case 'linux':
      return new Set(Object.keys(clipboard));
    default:
      return new Set();
  }
})();

ipcMainUtils.handle('ELECTRON_BROWSER_CLIPBOARD', function (event, method, ...args) {
  if (!allowedClipboardMethods.has(method)) {
    throw new Error(`Invalid method: ${method}`);
  }

  return typeUtils.serialize(electron.clipboard[method](...typeUtils.deserialize(args)));
});

if (features.isDesktopCapturerEnabled()) {
  const desktopCapturer = require('@electron/internal/browser/desktop-capturer');

  ipcMainUtils.handle('ELECTRON_BROWSER_DESKTOP_CAPTURER_GET_SOURCES', function (event, ...args) {
    const customEvent = emitCustomEvent(event.sender, 'desktop-capturer-get-sources');

    if (customEvent.defaultPrevented) {
      console.error('Blocked desktopCapturer.getSources()');
      return [];
    }

    return desktopCapturer.getSources(event, ...args);
  });
}

const getPreloadScript = async function (preloadPath) {
  let preloadSrc = null;
  let preloadError = null;
  try {
    preloadSrc = (await fs.promises.readFile(preloadPath)).toString();
  } catch (err) {
    preloadError = errorUtils.serialize(err);
  }
  return { preloadPath, preloadSrc, preloadError };
};

ipcMainUtils.handle('ELECTRON_GET_CONTENT_SCRIPTS', () => getContentScripts());

ipcMainUtils.handle('ELECTRON_BROWSER_SANDBOX_LOAD', async function (event) {
  const preloadPaths = event.sender._getPreloadPaths();
  const webPreferences = event.sender.getLastWebPreferences() || {};

  return {
    contentScripts: getContentScripts(),
    preloadScripts: await Promise.all(preloadPaths.map(path => getPreloadScript(path))),
    isRemoteModuleEnabled: isRemoteModuleEnabled(event.sender),
    isWebViewTagEnabled: guestViewManager.isWebViewTagEnabled(event.sender),
    guestInstanceId: webPreferences.guestInstanceId,
    openerId: webPreferences.openerId,
    process: {
      arch: process.arch,
      platform: process.platform,
      env: process.env,
      version: process.version,
      versions: process.versions,
      execPath: process.helperExecPath
    }
  };
});

ipcMainInternal.on('ELECTRON_BROWSER_PRELOAD_ERROR', function (event, preloadPath, error) {
  event.sender.emit('preload-error', event, preloadPath, errorUtils.deserialize(error));
});