components/extensions/ExtensionCommon.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";

/**
 * This module contains utilities and base classes for logic which is
 * common between the parent and child process, and in particular
 * between ExtensionParent.jsm and ExtensionChild.jsm.
 */

const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;

/* exported ExtensionCommon */

this.EXPORTED_SYMBOLS = ["ExtensionCommon"];

Cu.import("resource://gre/modules/Services.jsm");
Cu.import("resource://gre/modules/XPCOMUtils.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "MessageChannel",
                                  "resource://gre/modules/MessageChannel.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "PrivateBrowsingUtils",
                                  "resource://gre/modules/PrivateBrowsingUtils.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Schemas",
                                  "resource://gre/modules/Schemas.jsm");

Cu.import("resource://gre/modules/ExtensionUtils.jsm");

var {
  EventEmitter,
  ExtensionError,
  SpreadArgs,
  getConsole,
  getInnerWindowID,
  getUniqueId,
  runSafeSync,
  runSafeSyncWithoutClone,
  instanceOf,
} = ExtensionUtils;

XPCOMUtils.defineLazyGetter(this, "console", getConsole);

class BaseContext {
  constructor(envType, extension) {
    this.envType = envType;
    this.onClose = new Set();
    this.checkedLastError = false;
    this._lastError = null;
    this.contextId = getUniqueId();
    this.unloaded = false;
    this.extension = extension;
    this.jsonSandbox = null;
    this.active = true;
    this.incognito = null;
    this.messageManager = null;
    this.docShell = null;
    this.contentWindow = null;
    this.innerWindowID = 0;
  }

  setContentWindow(contentWindow) {
    let {document} = contentWindow;
    let docShell = contentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
                                .getInterface(Ci.nsIDocShell);

    this.innerWindowID = getInnerWindowID(contentWindow);
    this.messageManager = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
                                  .getInterface(Ci.nsIContentFrameMessageManager);

    if (this.incognito == null) {
      this.incognito = PrivateBrowsingUtils.isContentWindowPrivate(contentWindow);
    }

    MessageChannel.setupMessageManagers([this.messageManager]);

    let onPageShow = event => {
      if (!event || event.target === document) {
        this.docShell = docShell;
        this.contentWindow = contentWindow;
        this.active = true;
      }
    };
    let onPageHide = event => {
      if (!event || event.target === document) {
        // Put this off until the next tick.
        Promise.resolve().then(() => {
          this.docShell = null;
          this.contentWindow = null;
          this.active = false;
        });
      }
    };

    onPageShow();
    contentWindow.addEventListener("pagehide", onPageHide, true);
    contentWindow.addEventListener("pageshow", onPageShow, true);
    this.callOnClose({
      close: () => {
        onPageHide();
        if (this.active) {
          contentWindow.removeEventListener("pagehide", onPageHide, true);
          contentWindow.removeEventListener("pageshow", onPageShow, true);
        }
      },
    });
  }

  get cloneScope() {
    throw new Error("Not implemented");
  }

  get principal() {
    throw new Error("Not implemented");
  }

  runSafe(...args) {
    if (this.unloaded) {
      Cu.reportError("context.runSafe called after context unloaded");
    } else if (!this.active) {
      Cu.reportError("context.runSafe called while context is inactive");
    } else {
      return runSafeSync(this, ...args);
    }
  }

  runSafeWithoutClone(...args) {
    if (this.unloaded) {
      Cu.reportError("context.runSafeWithoutClone called after context unloaded");
    } else if (!this.active) {
      Cu.reportError("context.runSafeWithoutClone called while context is inactive");
    } else {
      return runSafeSyncWithoutClone(...args);
    }
  }

  checkLoadURL(url, options = {}) {
    let ssm = Services.scriptSecurityManager;

    let flags = ssm.STANDARD;
    if (!options.allowScript) {
      flags |= ssm.DISALLOW_SCRIPT;
    }
    if (!options.allowInheritsPrincipal) {
      flags |= ssm.DISALLOW_INHERIT_PRINCIPAL;
    }
    if (options.dontReportErrors) {
      flags |= ssm.DONT_REPORT_ERRORS;
    }

    try {
      ssm.checkLoadURIStrWithPrincipal(this.principal, url, flags);
    } catch (e) {
      return false;
    }
    return true;
  }

  /**
   * Safely call JSON.stringify() on an object that comes from an
   * extension.
   *
   * @param {array<any>} args Arguments for JSON.stringify()
   * @returns {string} The stringified representation of obj
   */
  jsonStringify(...args) {
    if (!this.jsonSandbox) {
      this.jsonSandbox = Cu.Sandbox(this.principal, {
        sameZoneAs: this.cloneScope,
        wantXrays: false,
      });
    }

    return Cu.waiveXrays(this.jsonSandbox.JSON).stringify(...args);
  }

  callOnClose(obj) {
    this.onClose.add(obj);
  }

  forgetOnClose(obj) {
    this.onClose.delete(obj);
  }

  /**
   * A wrapper around MessageChannel.sendMessage which adds the extension ID
   * to the recipient object, and ensures replies are not processed after the
   * context has been unloaded.
   *
   * @param {nsIMessageManager} target
   * @param {string} messageName
   * @param {object} data
   * @param {object} [options]
   * @param {object} [options.sender]
   * @param {object} [options.recipient]
   *
   * @returns {Promise}
   */
  sendMessage(target, messageName, data, options = {}) {
    options.recipient = options.recipient || {};
    options.sender = options.sender || {};

    options.recipient.extensionId = this.extension.id;
    options.sender.extensionId = this.extension.id;
    options.sender.contextId = this.contextId;

    return MessageChannel.sendMessage(target, messageName, data, options);
  }

  get lastError() {
    this.checkedLastError = true;
    return this._lastError;
  }

  set lastError(val) {
    this.checkedLastError = false;
    this._lastError = val;
  }

  /**
   * Normalizes the given error object for use by the target scope. If
   * the target is an error object which belongs to that scope, it is
   * returned as-is. If it is an ordinary object with a `message`
   * property, it is converted into an error belonging to the target
   * scope. If it is an Error object which does *not* belong to the
   * clone scope, it is reported, and converted to an unexpected
   * exception error.
   *
   * @param {Error|object} error
   * @returns {Error}
   */
  normalizeError(error) {
    if (error instanceof this.cloneScope.Error) {
      return error;
    }
    let message;
    if (instanceOf(error, "Object") || error instanceof ExtensionError) {
      message = error.message;
    } else if (typeof error == "object" &&
        this.principal.subsumes(Cu.getObjectPrincipal(error))) {
      message = error.message;
    } else {
      Cu.reportError(error);
    }
    message = message || "An unexpected error occurred";
    return new this.cloneScope.Error(message);
  }

  /**
   * Sets the value of `.lastError` to `error`, calls the given
   * callback, and reports an error if the value has not been checked
   * when the callback returns.
   *
   * @param {object} error An object with a `message` property. May
   *     optionally be an `Error` object belonging to the target scope.
   * @param {function} callback The callback to call.
   * @returns {*} The return value of callback.
   */
  withLastError(error, callback) {
    this.lastError = this.normalizeError(error);
    try {
      return callback();
    } finally {
      if (!this.checkedLastError) {
        Cu.reportError(`Unchecked lastError value: ${this.lastError}`);
      }
      this.lastError = null;
    }
  }

  /**
   * Wraps the given promise so it can be safely returned to extension
   * code in this context.
   *
   * If `callback` is provided, however, it is used as a completion
   * function for the promise, and no promise is returned. In this case,
   * the callback is called when the promise resolves or rejects. In the
   * latter case, `lastError` is set to the rejection value, and the
   * callback function must check `browser.runtime.lastError` or
   * `extension.runtime.lastError` in order to prevent it being reported
   * to the console.
   *
   * @param {Promise} promise The promise with which to wrap the
   *     callback. May resolve to a `SpreadArgs` instance, in which case
   *     each element will be used as a separate argument.
   *
   *     Unless the promise object belongs to the cloneScope global, its
   *     resolution value is cloned into cloneScope prior to calling the
   *     `callback` function or resolving the wrapped promise.
   *
   * @param {function} [callback] The callback function to wrap
   *
   * @returns {Promise|undefined} If callback is null, a promise object
   *     belonging to the target scope. Otherwise, undefined.
   */
  wrapPromise(promise, callback = null) {
    let runSafe = this.runSafe.bind(this);
    if (promise instanceof this.cloneScope.Promise) {
      runSafe = this.runSafeWithoutClone.bind(this);
    }

    if (callback) {
      promise.then(
        args => {
          if (this.unloaded) {
            dump(`Promise resolved after context unloaded\n`);
          } else if (!this.active) {
            dump(`Promise resolved while context is inactive\n`);
          } else if (args instanceof SpreadArgs) {
            runSafe(callback, ...args);
          } else {
            runSafe(callback, args);
          }
        },
        error => {
          this.withLastError(error, () => {
            if (this.unloaded) {
              dump(`Promise rejected after context unloaded\n`);
            } else if (!this.active) {
              dump(`Promise rejected while context is inactive\n`);
            } else {
              this.runSafeWithoutClone(callback);
            }
          });
        });
    } else {
      return new this.cloneScope.Promise((resolve, reject) => {
        promise.then(
          value => {
            if (this.unloaded) {
              dump(`Promise resolved after context unloaded\n`);
            } else if (!this.active) {
              dump(`Promise resolved while context is inactive\n`);
            } else if (value instanceof SpreadArgs) {
              runSafe(resolve, value.length == 1 ? value[0] : value);
            } else {
              runSafe(resolve, value);
            }
          },
          value => {
            if (this.unloaded) {
              dump(`Promise rejected after context unloaded: ${value && value.message}\n`);
            } else if (!this.active) {
              dump(`Promise rejected while context is inactive: ${value && value.message}\n`);
            } else {
              this.runSafeWithoutClone(reject, this.normalizeError(value));
            }
          });
      });
    }
  }

  unload() {
    this.unloaded = true;

    MessageChannel.abortResponses({
      extensionId: this.extension.id,
      contextId: this.contextId,
    });

    for (let obj of this.onClose) {
      obj.close();
    }
  }

  /**
   * A simple proxy for unload(), for use with callOnClose().
   */
  close() {
    this.unload();
  }
}

/**
 * An object that runs the implementation of a schema API. Instantiations of
 * this interfaces are used by Schemas.jsm.
 *
 * @interface
 */
class SchemaAPIInterface {
  /**
   * Calls this as a function that returns its return value.
   *
   * @abstract
   * @param {Array} args The parameters for the function.
   * @returns {*} The return value of the invoked function.
   */
  callFunction(args) {
    throw new Error("Not implemented");
  }

  /**
   * Calls this as a function and ignores its return value.
   *
   * @abstract
   * @param {Array} args The parameters for the function.
   */
  callFunctionNoReturn(args) {
    throw new Error("Not implemented");
  }

  /**
   * Calls this as a function that completes asynchronously.
   *
   * @abstract
   * @param {Array} args The parameters for the function.
   * @param {function(*)} [callback] The callback to be called when the function
   *     completes.
   * @returns {Promise|undefined} Must be void if `callback` is set, and a
   *     promise otherwise. The promise is resolved when the function completes.
   */
  callAsyncFunction(args, callback) {
    throw new Error("Not implemented");
  }

  /**
   * Retrieves the value of this as a property.
   *
   * @abstract
   * @returns {*} The value of the property.
   */
  getProperty() {
    throw new Error("Not implemented");
  }

  /**
   * Assigns the value to this as property.
   *
   * @abstract
   * @param {string} value The new value of the property.
   */
  setProperty(value) {
    throw new Error("Not implemented");
  }

  /**
   * Registers a `listener` to this as an event.
   *
   * @abstract
   * @param {function} listener The callback to be called when the event fires.
   * @param {Array} args Extra parameters for EventManager.addListener.
   * @see EventManager.addListener
   */
  addListener(listener, args) {
    throw new Error("Not implemented");
  }

  /**
   * Checks whether `listener` is listening to this as an event.
   *
   * @abstract
   * @param {function} listener The event listener.
   * @returns {boolean} Whether `listener` is registered with this as an event.
   * @see EventManager.hasListener
   */
  hasListener(listener) {
    throw new Error("Not implemented");
  }

  /**
   * Unregisters `listener` from this as an event.
   *
   * @abstract
   * @param {function} listener The event listener.
   * @see EventManager.removeListener
   */
  removeListener(listener) {
    throw new Error("Not implemented");
  }
}

/**
 * An object that runs a locally implemented API.
 */
class LocalAPIImplementation extends SchemaAPIInterface {
  /**
   * Constructs an implementation of the `name` method or property of `pathObj`.
   *
   * @param {object} pathObj The object containing the member with name `name`.
   * @param {string} name The name of the implemented member.
   * @param {BaseContext} context The context in which the schema is injected.
   */
  constructor(pathObj, name, context) {
    super();
    this.pathObj = pathObj;
    this.name = name;
    this.context = context;
  }

  callFunction(args) {
    return this.pathObj[this.name](...args);
  }

  callFunctionNoReturn(args) {
    this.pathObj[this.name](...args);
  }

  callAsyncFunction(args, callback) {
    let promise;
    try {
      promise = this.pathObj[this.name](...args) || Promise.resolve();
    } catch (e) {
      promise = Promise.reject(e);
    }
    return this.context.wrapPromise(promise, callback);
  }

  getProperty() {
    return this.pathObj[this.name];
  }

  setProperty(value) {
    this.pathObj[this.name] = value;
  }

  addListener(listener, args) {
    try {
      this.pathObj[this.name].addListener.call(null, listener, ...args);
    } catch (e) {
      throw this.context.normalizeError(e);
    }
  }

  hasListener(listener) {
    return this.pathObj[this.name].hasListener.call(null, listener);
  }

  removeListener(listener) {
    this.pathObj[this.name].removeListener.call(null, listener);
  }
}

/**
 * This object loads the ext-*.js scripts that define the extension API.
 *
 * This class instance is shared with the scripts that it loads, so that the
 * ext-*.js scripts and the instantiator can communicate with each other.
 */
class SchemaAPIManager extends EventEmitter {
  /**
   * @param {string} processType
   *     "main" - The main, one and only chrome browser process.
   *     "addon" - An addon process.
   *     "content" - A content process.
   */
  constructor(processType) {
    super();
    this.processType = processType;
    this.global = this._createExtGlobal();
    this._scriptScopes = [];
    this._schemaApis = {
      addon_parent: [],
      addon_child: [],
      content_parent: [],
      content_child: [],
    };
  }

  /**
   * Create a global object that is used as the shared global for all ext-*.js
   * scripts that are loaded via `loadScript`.
   *
   * @returns {object} A sandbox that is used as the global by `loadScript`.
   */
  _createExtGlobal() {
    let global = Cu.Sandbox(Services.scriptSecurityManager.getSystemPrincipal(), {
      wantXrays: false,
      sandboxName: `Namespace of ext-*.js scripts for ${this.processType}`,
    });

    Object.assign(global, {global, Cc, Ci, Cu, Cr, XPCOMUtils, extensions: this});

    XPCOMUtils.defineLazyGetter(global, "console", getConsole);

    XPCOMUtils.defineLazyModuleGetter(global, "require",
                                      "resource://devtools/shared/Loader.jsm");

    return global;
  }

  /**
   * Load an ext-*.js script. The script runs in its own scope, if it wishes to
   * share state with another script it can assign to the `global` variable. If
   * it wishes to communicate with this API manager, use `extensions`.
   *
   * @param {string} scriptUrl The URL of the ext-*.js script.
   */
  loadScript(scriptUrl) {
    // Create the object in the context of the sandbox so that the script runs
    // in the sandbox's context instead of here.
    let scope = Cu.createObjectIn(this.global);

    Services.scriptloader.loadSubScript(scriptUrl, scope, "UTF-8");

    // Save the scope to avoid it being garbage collected.
    this._scriptScopes.push(scope);
  }

  /**
   * Called by an ext-*.js script to register an API.
   *
   * @param {string} namespace The API namespace.
   *     Intended to match the namespace of the generated API, but not used at
   *     the moment - see bugzil.la/1295774.
   * @param {string} envType Restricts the API to contexts that run in the
   *    given environment. Must be one of the following:
   *     - "addon_parent" - addon APIs that runs in the main process.
   *     - "addon_child" - addon APIs that runs in an addon process.
   *     - "content_parent" - content script APIs that runs in the main process.
   *     - "content_child" - content script APIs that runs in a content process.
   * @param {function(BaseContext)} getAPI A function that returns an object
   *     that will be merged with |chrome| and |browser|. The next example adds
   *     the create, update and remove methods to the tabs API.
   *
   *     registerSchemaAPI("tabs", "addon_parent", (context) => ({
   *       tabs: { create, update },
   *     }));
   *     registerSchemaAPI("tabs", "addon_parent", (context) => ({
   *       tabs: { remove },
   *     }));
   */
  registerSchemaAPI(namespace, envType, getAPI) {
    this._schemaApis[envType].push({namespace, getAPI});
  }

  /**
   * Exports all registered scripts to `obj`.
   *
   * @param {BaseContext} context The context for which the API bindings are
   *     generated.
   * @param {object} obj The destination of the API.
   */
  generateAPIs(context, obj) {
    let apis = this._schemaApis[context.envType];
    if (!apis) {
      Cu.reportError(`No APIs have been registered for ${context.envType}`);
      return;
    }
    SchemaAPIManager.generateAPIs(context, apis, obj);
  }

  /**
   * Mash together all the APIs from `apis` into `obj`.
   *
   * @param {BaseContext} context The context for which the API bindings are
   *     generated.
   * @param {Array} apis A list of objects, see `registerSchemaAPI`.
   * @param {object} obj The destination of the API.
   */
  static generateAPIs(context, apis, obj) {
    // Recursively copy properties from source to dest.
    function copy(dest, source) {
      for (let prop in source) {
        let desc = Object.getOwnPropertyDescriptor(source, prop);
        if (typeof(desc.value) == "object") {
          if (!(prop in dest)) {
            dest[prop] = {};
          }
          copy(dest[prop], source[prop]);
        } else {
          Object.defineProperty(dest, prop, desc);
        }
      }
    }

    for (let api of apis) {
      if (Schemas.checkPermissions(api.namespace, context.extension)) {
        api = api.getAPI(context);
        copy(obj, api);
      }
    }
  }
}

const ExtensionCommon = {
  BaseContext,
  LocalAPIImplementation,
  SchemaAPIInterface,
  SchemaAPIManager,
};