patchedmediakeys_apple.js

/** @license
 * Copyright 2016 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

goog.provide('shaka.polyfill.PatchedMediaKeysApple');

goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.media.DrmEngine');
goog.require('shaka.polyfill');
goog.require('shaka.util.BufferUtils');
goog.require('shaka.util.EventManager');
goog.require('shaka.util.FakeEvent');
goog.require('shaka.util.FakeEventTarget');
goog.require('shaka.util.PublicPromise');


/**
 * @summary A polyfill to implement modern, standardized EME on top of Apple's
 * prefixed EME in Safari.
 */
shaka.polyfill.PatchedMediaKeysApple = class {
  /**
   * Installs the polyfill if needed.
   */
  static install() {
    if (!window.HTMLVideoElement || !window.WebKitMediaKeys) {
      // No HTML5 video or no prefixed EME.
      return;
    }

    // TODO: Prefer unprefixed EME once we know how to use it.
    // See: https://bugs.webkit.org/show_bug.cgi?id=197433
    /*
    if (navigator.requestMediaKeySystemAccess &&
        MediaKeySystemAccess.prototype.getConfiguration) {
      // Prefixed EME is preferable.
      return;
    }
    */

    shaka.log.info('Using Apple-prefixed EME');

    // Alias
    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;

    // Delete mediaKeys to work around strict mode compatibility issues.
    // eslint-disable-next-line no-restricted-syntax
    delete HTMLMediaElement.prototype['mediaKeys'];
    // Work around read-only declaration for mediaKeys by using a string.
    // eslint-disable-next-line no-restricted-syntax
    HTMLMediaElement.prototype['mediaKeys'] = null;
    // eslint-disable-next-line no-restricted-syntax
    HTMLMediaElement.prototype.setMediaKeys =
        PatchedMediaKeysApple.setMediaKeys;

    // Install patches
    window.MediaKeys = PatchedMediaKeysApple.MediaKeys;
    window.MediaKeySystemAccess = PatchedMediaKeysApple.MediaKeySystemAccess;
    navigator.requestMediaKeySystemAccess =
        PatchedMediaKeysApple.requestMediaKeySystemAccess;
  }

  /**
   * An implementation of navigator.requestMediaKeySystemAccess.
   * Retrieves a MediaKeySystemAccess object.
   *
   * @this {!Navigator}
   * @param {string} keySystem
   * @param {!Array.<!MediaKeySystemConfiguration>} supportedConfigurations
   * @return {!Promise.<!MediaKeySystemAccess>}
   */
  static requestMediaKeySystemAccess(keySystem, supportedConfigurations) {
    shaka.log.debug('PatchedMediaKeysApple.requestMediaKeySystemAccess');
    goog.asserts.assert(this == navigator,
        'bad "this" for requestMediaKeySystemAccess');

    // Alias.
    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;
    try {
      const access = new PatchedMediaKeysApple.MediaKeySystemAccess(
          keySystem, supportedConfigurations);
      return Promise.resolve(/** @type {!MediaKeySystemAccess} */ (access));
    } catch (exception) {
      return Promise.reject(exception);
    }
  }

  /**
   * An implementation of HTMLMediaElement.prototype.setMediaKeys.
   * Attaches a MediaKeys object to the media element.
   *
   * @this {!HTMLMediaElement}
   * @param {MediaKeys} mediaKeys
   * @return {!Promise}
   */
  static setMediaKeys(mediaKeys) {
    shaka.log.debug('PatchedMediaKeysApple.setMediaKeys');
    goog.asserts.assert(this instanceof HTMLMediaElement,
        'bad "this" for setMediaKeys');

    // Alias
    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;

    const newMediaKeys =
    /** @type {shaka.polyfill.PatchedMediaKeysApple.MediaKeys} */ (
        mediaKeys);
    const oldMediaKeys =
    /** @type {shaka.polyfill.PatchedMediaKeysApple.MediaKeys} */ (
        this.mediaKeys);

    if (oldMediaKeys && oldMediaKeys != newMediaKeys) {
      goog.asserts.assert(
          oldMediaKeys instanceof PatchedMediaKeysApple.MediaKeys,
          'non-polyfill instance of oldMediaKeys');
      // Have the old MediaKeys stop listening to events on the video tag.
      oldMediaKeys.setMedia(null);
    }

    delete this['mediaKeys'];  // in case there is an existing getter
    this['mediaKeys'] = mediaKeys;  // work around read-only declaration

    if (newMediaKeys) {
      goog.asserts.assert(
          newMediaKeys instanceof PatchedMediaKeysApple.MediaKeys,
          'non-polyfill instance of newMediaKeys');
      return newMediaKeys.setMedia(this);
    }

    return Promise.resolve();
  }

  /**
   * Handler for the native media elements webkitneedkey event.
   *
   * @this {!HTMLMediaElement}
   * @param {!MediaKeyEvent} event
   * @suppress {constantProperty} We reassign what would be const on a real
   *   MediaEncryptedEvent, but in our look-alike event.
   * @private
   */
  static onWebkitNeedKey_(event) {
    shaka.log.debug('PatchedMediaKeysApple.onWebkitNeedKey_', event);

    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;
    const mediaKeys =
    /** @type {shaka.polyfill.PatchedMediaKeysApple.MediaKeys} */(
        this.mediaKeys);
    goog.asserts.assert(mediaKeys instanceof PatchedMediaKeysApple.MediaKeys,
        'non-polyfill instance of newMediaKeys');

    goog.asserts.assert(event.initData != null, 'missing init data!');

    // Convert the prefixed init data to match the native 'encrypted' event.
    const uint8 = shaka.util.BufferUtils.toUint8(event.initData);
    const dataview = shaka.util.BufferUtils.toDataView(uint8);
    // The first part is a 4 byte little-endian int, which is the length of
    // the second part.
    const length = dataview.getUint32(
        /* position= */ 0, /* littleEndian= */ true);
    if (length + 4 != uint8.byteLength) {
      throw new RangeError('Malformed FairPlay init data');
    }
    // The remainder is a UTF-16 skd URL.  Convert this to UTF-8 and pass on.
    const str = shaka.util.StringUtils.fromUTF16(
        uint8.subarray(4), /* littleEndian= */ true);
    const initData = shaka.util.StringUtils.toUTF8(str);

    // NOTE: Because "this" is a real EventTarget, the event we dispatch here
    // must also be a real Event.
    const event2 = new Event('encrypted');

    const encryptedEvent =
      /** @type {!MediaEncryptedEvent} */(/** @type {?} */(event2));
    encryptedEvent.initDataType = 'skd';
    encryptedEvent.initData = shaka.util.BufferUtils.toArrayBuffer(initData);

    this.dispatchEvent(event2);
  }
};


/**
 * An implementation of MediaKeySystemAccess.
 *
 * @implements {MediaKeySystemAccess}
 */
shaka.polyfill.PatchedMediaKeysApple.MediaKeySystemAccess = class {
  /**
   * @param {string} keySystem
   * @param {!Array.<!MediaKeySystemConfiguration>} supportedConfigurations
   */
  constructor(keySystem, supportedConfigurations) {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeySystemAccess');

    /** @type {string} */
    this.keySystem = keySystem;

    /** @private {!MediaKeySystemConfiguration} */
    this.configuration_;

    // Optimization: WebKitMediaKeys.isTypeSupported delays responses by a
    // significant amount of time, possibly to discourage fingerprinting.
    // Since we know only FairPlay is supported here, let's skip queries for
    // anything else to speed up the process.
    if (keySystem.startsWith('com.apple.fps')) {
      for (const cfg of supportedConfigurations) {
        const newCfg = this.checkConfig_(cfg);
        if (newCfg) {
          this.configuration_ = newCfg;
          return;
        }
      }
    }

    // According to the spec, this should be a DOMException, but there is not a
    // public constructor for that.  So we make this look-alike instead.
    const unsupportedKeySystemError = new Error('Unsupported keySystem');
    unsupportedKeySystemError.name = 'NotSupportedError';
    unsupportedKeySystemError['code'] = DOMException.NOT_SUPPORTED_ERR;
    throw unsupportedKeySystemError;
  }

  /**
   * Check a single config for MediaKeySystemAccess.
   *
   * @param {MediaKeySystemConfiguration} cfg The requested config.
   * @return {?MediaKeySystemConfiguration} A matching config we can support, or
   *   null if the input is not supportable.
   * @private
   */
  checkConfig_(cfg) {
    if (cfg.persistentState == 'required') {
      // Not supported by the prefixed API.
      return null;
    }

    // Create a new config object and start adding in the pieces which we find
    // support for.  We will return this from getConfiguration() later if
    // asked.

    /** @type {!MediaKeySystemConfiguration} */
    const newCfg = {
      'audioCapabilities': [],
      'videoCapabilities': [],
      // It is technically against spec to return these as optional, but we
      // don't truly know their values from the prefixed API:
      'persistentState': 'optional',
      'distinctiveIdentifier': 'optional',
      // Pretend the requested init data types are supported, since we don't
      // really know that either:
      'initDataTypes': cfg.initDataTypes,
      'sessionTypes': ['temporary'],
      'label': cfg.label,
    };

    // PatchedMediaKeysApple tests for key system availability through
    // WebKitMediaKeys.isTypeSupported.
    let ranAnyTests = false;
    let success = false;

    if (cfg.audioCapabilities) {
      for (const cap of cfg.audioCapabilities) {
        if (cap.contentType) {
          ranAnyTests = true;

          const contentType = cap.contentType.split(';')[0];
          if (WebKitMediaKeys.isTypeSupported(this.keySystem, contentType)) {
            newCfg.audioCapabilities.push(cap);
            success = true;
          }
        }
      }
    }

    if (cfg.videoCapabilities) {
      for (const cap of cfg.videoCapabilities) {
        if (cap.contentType) {
          ranAnyTests = true;

          const contentType = cap.contentType.split(';')[0];
          if (WebKitMediaKeys.isTypeSupported(this.keySystem, contentType)) {
            newCfg.videoCapabilities.push(cap);
            success = true;
          }
        }
      }
    }

    if (!ranAnyTests) {
      // If no specific types were requested, we check all common types to
      // find out if the key system is present at all.
      success = WebKitMediaKeys.isTypeSupported(this.keySystem, 'video/mp4');
    }

    if (success) {
      return newCfg;
    }
    return null;
  }

  /** @override */
  createMediaKeys() {
    shaka.log.debug(
        'PatchedMediaKeysApple.MediaKeySystemAccess.createMediaKeys');

    // Alias
    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;

    const mediaKeys = new PatchedMediaKeysApple.MediaKeys(this.keySystem);
    return Promise.resolve(/** @type {!MediaKeys} */ (mediaKeys));
  }

  /** @override */
  getConfiguration() {
    shaka.log.debug(
        'PatchedMediaKeysApple.MediaKeySystemAccess.getConfiguration');
    return this.configuration_;
  }
};


/**
 * An implementation of MediaKeys.
 *
 * @implements {MediaKeys}
 */
shaka.polyfill.PatchedMediaKeysApple.MediaKeys = class {
  /** @param {string} keySystem */
  constructor(keySystem) {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeys');

    /** @private {!WebKitMediaKeys} */
    this.nativeMediaKeys_ = new WebKitMediaKeys(keySystem);

    /** @private {!shaka.util.EventManager} */
    this.eventManager_ = new shaka.util.EventManager();
  }

  /** @override */
  createSession(sessionType) {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeys.createSession');

    sessionType = sessionType || 'temporary';
    // For now, only the 'temporary' type is supported.
    if (sessionType != 'temporary') {
      throw new TypeError('Session type ' + sessionType +
      ' is unsupported on this platform.');
    }

    // Alias
    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;

    return new PatchedMediaKeysApple.MediaKeySession(
        this.nativeMediaKeys_, sessionType);
  }

  /** @override */
  setServerCertificate(serverCertificate) {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeys.setServerCertificate');
    return Promise.resolve(false);
  }

  /**
   * @param {HTMLMediaElement} media
   * @protected
   * @return {!Promise}
   */
  setMedia(media) {
    // Alias
    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;

    // Remove any old listeners.
    this.eventManager_.removeAll();

    // It is valid for media to be null; null is used to flag that event
    // handlers need to be cleaned up.
    if (!media) {
      return Promise.resolve();
    }

    // Intercept and translate these prefixed EME events.
    this.eventManager_.listen(media, 'webkitneedkey',
    /** @type {shaka.util.EventManager.ListenerType} */
        (PatchedMediaKeysApple.onWebkitNeedKey_));

    // Wrap native HTMLMediaElement.webkitSetMediaKeys with a Promise.
    try {
      // Some browsers require that readyState >=1 before mediaKeys can be
      // set, so check this and wait for loadedmetadata if we are not in the
      // correct state
      shaka.util.MediaReadyState.waitForReadyState(media,
          HTMLMediaElement.HAVE_METADATA,
          this.eventManager_, () => {
            media.webkitSetMediaKeys(this.nativeMediaKeys_);
          });

      return Promise.resolve();
    } catch (exception) {
      return Promise.reject(exception);
    }
  }
};


/**
 * An implementation of MediaKeySession.
 *
 * @implements {MediaKeySession}
 */
shaka.polyfill.PatchedMediaKeysApple.MediaKeySession =
class extends shaka.util.FakeEventTarget {
  /**
   * @param {WebKitMediaKeys} nativeMediaKeys
   * @param {string} sessionType
   */
  constructor(nativeMediaKeys, sessionType) {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeySession');
    super();

    /**
     * The native MediaKeySession, which will be created in generateRequest.
     * @private {WebKitMediaKeySession}
     */
    this.nativeMediaKeySession_ = null;

    /** @private {WebKitMediaKeys} */
    this.nativeMediaKeys_ = nativeMediaKeys;

    // Promises that are resolved later
    /** @private {shaka.util.PublicPromise} */
    this.generateRequestPromise_ = null;

    /** @private {shaka.util.PublicPromise} */
    this.updatePromise_ = null;

    /** @private {!shaka.util.EventManager} */
    this.eventManager_ = new shaka.util.EventManager();

    /** @type {string} */
    this.sessionId = '';

    /** @type {number} */
    this.expiration = NaN;

    /** @type {!shaka.util.PublicPromise} */
    this.closed = new shaka.util.PublicPromise();

    /** @type {!shaka.polyfill.PatchedMediaKeysApple.MediaKeyStatusMap} */
    this.keyStatuses =
        new shaka.polyfill.PatchedMediaKeysApple.MediaKeyStatusMap();
  }

  /** @override */
  generateRequest(initDataType, initData) {
    shaka.log.debug(
        'PatchedMediaKeysApple.MediaKeySession.generateRequest');

    this.generateRequestPromise_ = new shaka.util.PublicPromise();

    try {
      // This EME spec version requires a MIME content type as the 1st param to
      // createSession, but doesn't seem to matter what the value is.
      // It also only accepts Uint8Array, not ArrayBuffer, so explicitly make
      // initData into a Uint8Array.
      const session = this.nativeMediaKeys_.createSession(
          'video/mp4', shaka.util.BufferUtils.toUint8(initData));
      this.nativeMediaKeySession_ = session;
      this.sessionId = session.sessionId || '';

      // Attach session event handlers here.
      this.eventManager_.listen(
          this.nativeMediaKeySession_, 'webkitkeymessage',
          /** @type {shaka.util.EventManager.ListenerType} */
          ((event) => this.onWebkitKeyMessage_(event)));
      this.eventManager_.listen(session, 'webkitkeyadded',
          /** @type {shaka.util.EventManager.ListenerType} */
          ((event) => this.onWebkitKeyAdded_(event)));
      this.eventManager_.listen(session, 'webkitkeyerror',
          /** @type {shaka.util.EventManager.ListenerType} */
          ((event) => this.onWebkitKeyError_(event)));

      this.updateKeyStatus_('status-pending');
    } catch (exception) {
      this.generateRequestPromise_.reject(exception);
    }

    return this.generateRequestPromise_;
  }

  /** @override */
  load() {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeySession.load');

    return Promise.reject(new Error('MediaKeySession.load not yet supported'));
  }

  /** @override */
  update(response) {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeySession.update');

    this.updatePromise_ = new shaka.util.PublicPromise();

    try {
      // Pass through to the native session.
      this.nativeMediaKeySession_.update(
          shaka.util.BufferUtils.toUint8(response));
    } catch (exception) {
      this.updatePromise_.reject(exception);
    }

    return this.updatePromise_;
  }

  /** @override */
  close() {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeySession.close');

    try {
      // Pass through to the native session.
      this.nativeMediaKeySession_.close();

      this.closed.resolve();
      this.eventManager_.removeAll();
    } catch (exception) {
      this.closed.reject(exception);
    }

    return this.closed;
  }

  /** @override */
  remove() {
    shaka.log.debug('PatchedMediaKeysApple.MediaKeySession.remove');

    return Promise.reject(new Error(
        'MediaKeySession.remove is only applicable for persistent licenses, ' +
        'which are not supported on this platform'));
  }

  /**
   * Handler for the native keymessage event on WebKitMediaKeySession.
   *
   * @param {!MediaKeyEvent} event
   * @private
   */
  onWebkitKeyMessage_(event) {
    shaka.log.debug('PatchedMediaKeysApple.onWebkitKeyMessage_', event);

    // We can now resolve this.generateRequestPromise, which should be non-null.
    goog.asserts.assert(this.generateRequestPromise_,
        'generateRequestPromise_ should be set before now!');
    if (this.generateRequestPromise_) {
      this.generateRequestPromise_.resolve();
      this.generateRequestPromise_ = null;
    }

    const isNew = this.keyStatuses.getStatus() == undefined;

    const event2 = new shaka.util.FakeEvent('message', {
      messageType: isNew ? 'license-request' : 'license-renewal',
      message: shaka.util.BufferUtils.toArrayBuffer(event.message),
    });

    this.dispatchEvent(event2);
  }

  /**
   * Handler for the native keyadded event on WebKitMediaKeySession.
   *
   * @param {!MediaKeyEvent} event
   * @private
   */
  onWebkitKeyAdded_(event) {
    shaka.log.debug('PatchedMediaKeysApple.onWebkitKeyAdded_', event);

    // This shouldn't fire while we're in the middle of generateRequest,
    // but if it does, we will need to change the logic to account for it.
    goog.asserts.assert(!this.generateRequestPromise_,
        'Key added during generate!');

    // We can now resolve this.updatePromise, which should be non-null.
    goog.asserts.assert(this.updatePromise_,
        'updatePromise_ should be set before now!');
    if (this.updatePromise_) {
      this.updateKeyStatus_('usable');
      this.updatePromise_.resolve();
      this.updatePromise_ = null;
    }
  }

  /**
   * Handler for the native keyerror event on WebKitMediaKeySession.
   *
   * @param {!MediaKeyEvent} event
   * @private
   */
  onWebkitKeyError_(event) {
    shaka.log.debug('PatchedMediaKeysApple.onWebkitKeyError_', event);

    const error = new Error('EME PatchedMediaKeysApple key error');
    error['errorCode'] = this.nativeMediaKeySession_.error;

    if (this.generateRequestPromise_ != null) {
      this.generateRequestPromise_.reject(error);
      this.generateRequestPromise_ = null;
    } else if (this.updatePromise_ != null) {
      this.updatePromise_.reject(error);
      this.updatePromise_ = null;
    } else {
      // Unexpected error - map native codes to standardised key statuses.
      // Possible values of this.nativeMediaKeySession_.error.code:
      // MEDIA_KEYERR_UNKNOWN        = 1
      // MEDIA_KEYERR_CLIENT         = 2
      // MEDIA_KEYERR_SERVICE        = 3
      // MEDIA_KEYERR_OUTPUT         = 4
      // MEDIA_KEYERR_HARDWARECHANGE = 5
      // MEDIA_KEYERR_DOMAIN         = 6

      switch (this.nativeMediaKeySession_.error.code) {
        case WebKitMediaKeyError.MEDIA_KEYERR_OUTPUT:
        case WebKitMediaKeyError.MEDIA_KEYERR_HARDWARECHANGE:
          this.updateKeyStatus_('output-not-allowed');
          break;
        default:
          this.updateKeyStatus_('internal-error');
          break;
      }
    }
  }

  /**
   * Updates key status and dispatch a 'keystatuseschange' event.
   *
   * @param {string} status
   * @private
   */
  updateKeyStatus_(status) {
    this.keyStatuses.setStatus(status);
    const event = new shaka.util.FakeEvent('keystatuseschange');
    this.dispatchEvent(event);
  }
};


/**
 * @summary An implementation of MediaKeyStatusMap.
 * This fakes a map with a single key ID.
 *
 * @todo Consolidate the MediaKeyStatusMap types in these polyfills.
 * @implements {MediaKeyStatusMap}
 */
shaka.polyfill.PatchedMediaKeysApple.MediaKeyStatusMap = class {
  constructor() {
    /**
     * @type {number}
     */
    this.size = 0;

    /**
     * @private {string|undefined}
     */
    this.status_ = undefined;
  }

  /**
   * An internal method used by the session to set key status.
   * @param {string|undefined} status
   */
  setStatus(status) {
    this.size = status == undefined ? 0 : 1;
    this.status_ = status;
  }

  /**
   * An internal method used by the session to get key status.
   * @return {string|undefined}
   */
  getStatus() {
    return this.status_;
  }

  /** @override */
  forEach(fn) {
    if (this.status_) {
      fn(this.status_, shaka.media.DrmEngine.DUMMY_KEY_ID.value());
    }
  }

  /** @override */
  get(keyId) {
    if (this.has(keyId)) {
      return this.status_;
    }
    return undefined;
  }

  /** @override */
  has(keyId) {
    const fakeKeyId = shaka.media.DrmEngine.DUMMY_KEY_ID.value();
    if (this.status_ && shaka.util.BufferUtils.equal(keyId, fakeKeyId)) {
      return true;
    }
    return false;
  }

  /**
   * @suppress {missingReturn}
   * @override
   */
  entries() {
    goog.asserts.assert(false, 'Not used!  Provided only for the compiler.');
  }

  /**
   * @suppress {missingReturn}
   * @override
   */
  keys() {
    goog.asserts.assert(false, 'Not used!  Provided only for the compiler.');
  }

  /**
   * @suppress {missingReturn}
   * @override
   */
  values() {
    goog.asserts.assert(false, 'Not used!  Provided only for the compiler.');
  }
};


shaka.polyfill.register(shaka.polyfill.PatchedMediaKeysApple.install);