rx-player/src/main_thread/decrypt/utils/server_certificate_store.ts

Canal+ HTML5 Video Player

/**
 * Copyright 2015 CANAL+ Group
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import type { IMediaKeys } from "../../../compat/browser_compatibility_types";
import hashBuffer from "../../../utils/hash_buffer";

/**
 * Keep track of server certificate which have been set for a MediaKeys.
 * As it is impossible for a MediaKeys to have his server certificate reset
 * or updated, we consider that once it has been set, it will remain set until
 * the MediaKeys instance is killed.
 *
 * So, a WeakMap helps keeping a trace of which server certificate (identified
 * with a unique hash) is set on a MediaKeys.
 * `null` indicate that we don't know (and not `undefined`, because this is the
 * default value for when a WeakMap has no value for a key) which server
 * certificate is attached to a MediaKeys instance (most likely because related
 * EME APIs failed or had an unexpected behavior).
 */
const serverCertificateHashesMap = new WeakMap<
  IMediaKeys,
  { hash: number; serverCertificate: Uint8Array } | null
>();

/** ServerCertificateStore */
export default {
  /**
   * Tells the ServerCertificateStore that you begin to call the APIs to set a
   * ServerCertificate on `mediaKeys`.
   *
   * Calling this function is necessary due to how server certificate work
   * currently in EME APIs:
   * Because right now, it is impossible to tell if a MediaKeys instance has an
   * attached ServerCertificate or not when the corresponding API fails or if it
   * never answers, we prefer to announce through this function that the current
   * server certificate attached to this MediaKeys is for now invalid.
   * @param {MediaKeys | Object} mediaKeys
   */
  prepare(mediaKeys: IMediaKeys): void {
    serverCertificateHashesMap.set(mediaKeys, null);
  },

  /**
   * Attach a new server certificate to a MediaKeys in the
   * ServerCertificateStore.
   *
   * Only one server certificate should ever be attached to a MediaKeys
   * instance and the `prepare` function should have been called before any
   * action to update the server certificate took place (this function does not
   * enforce either of those behaviors).
   * @param {MediaKeys | Object} mediaKeys
   * @param {ArrayBufferView | BufferSource} serverCertificate
   */
  set(mediaKeys: IMediaKeys, serverCertificate: ArrayBufferView | BufferSource): void {
    const formattedServerCertificate: Uint8Array =
      serverCertificate instanceof Uint8Array
        ? serverCertificate
        : new Uint8Array(
            serverCertificate instanceof ArrayBuffer
              ? serverCertificate
              : serverCertificate.buffer,
          );
    const hash = hashBuffer(formattedServerCertificate);
    serverCertificateHashesMap.set(mediaKeys, {
      hash,
      serverCertificate: formattedServerCertificate,
    });
  },

  /**
   * Returns `true` if the MediaKeys instance has an attached ServerCertificate.
   * Returns `false` if it doesn't.
   *
   * Returns `undefined` if we cannot know, most likely because related EME APIs
   * failed or had an unexpected behavior.
   * @param {MediaKeys} mediaKeys
   * @returns {Boolean|undefined}
   */
  hasOne(mediaKeys: IMediaKeys): boolean | undefined {
    const currentServerCertificate = serverCertificateHashesMap.get(mediaKeys);
    if (currentServerCertificate === undefined) {
      return false;
    }
    if (currentServerCertificate === null) {
      return undefined;
    }
    return true;
  },

  /**
   * Returns `true` if the given `mediaKeys` has `serverCertificate` attached to
   * it.
   * Returns `false` either if it doesn't of if we doesn't know if it does.
   * @param {MediaKeys | Object} mediaKeys
   * @param {ArrayBufferView | BufferSource} serverCertificate
   * @returns {boolean}
   */
  has(mediaKeys: IMediaKeys, serverCertificate: ArrayBufferView | BufferSource): boolean {
    const serverCertificateHash = serverCertificateHashesMap.get(mediaKeys);
    if (serverCertificateHash === undefined || serverCertificateHash === null) {
      return false;
    }
    const { hash: oldHash, serverCertificate: oldServerCertificate } =
      serverCertificateHash;
    const newServerCertificate: Uint8Array =
      serverCertificate instanceof Uint8Array
        ? serverCertificate
        : new Uint8Array(
            serverCertificate instanceof ArrayBuffer
              ? serverCertificate
              : serverCertificate.buffer,
          );
    const newHash = hashBuffer(newServerCertificate);
    if (
      newHash !== oldHash ||
      oldServerCertificate.length !== newServerCertificate.length
    ) {
      return false;
    }
    for (let i = 0; i < oldServerCertificate.length; i++) {
      if (oldServerCertificate[i] !== newServerCertificate[i]) {
        return false;
      }
    }
    return true;
  },
};