hmac.js

var CryptoJS = require('./core');

(function() {
  // Shortcuts
  var C = CryptoJS;
  var C_lib = C.lib;
  var Base = C_lib.Base;
  var C_enc = C.enc;
  var Utf8 = C_enc.Utf8;
  var C_algo = C.algo;

  /**
   * HMAC algorithm.
   */
  var HMAC = C_algo.HMAC = Base.extend({
    /**
     * Initializes a newly created HMAC.
     *
     * @param {Hasher} hasher The hash algorithm to use.
     * @param {WordArray|string} key The secret key.
     *
     * @example
     *
     *     var hmacHasher = CryptoJS.algo.HMAC.create(CryptoJS.algo.SHA256, key);
     */
    init: function(hasher, key) {
      // Init hasher
      hasher = this._hasher = new hasher.init();

      // Convert string to WordArray, else assume WordArray already
      if (typeof key == 'string') {
        key = Utf8.parse(key);
      }

      // Shortcuts
      var hasherBlockSize = hasher.blockSize;
      var hasherBlockSizeBytes = hasherBlockSize * 4;

      // Allow arbitrary length keys
      if (key.sigBytes > hasherBlockSizeBytes) {
        key = hasher.finalize(key);
      }

      // Clamp excess bits
      key.clamp();

      // Clone key for inner and outer pads
      var oKey = this._oKey = key.clone();
      var iKey = this._iKey = key.clone();

      // Shortcuts
      var oKeyWords = oKey.words;
      var iKeyWords = iKey.words;

      // XOR keys with pad constants
      for (var i = 0; i < hasherBlockSize; i++) {
        oKeyWords[i] ^= 0x5c5c5c5c;
        iKeyWords[i] ^= 0x36363636;
      }
      oKey.sigBytes = iKey.sigBytes = hasherBlockSizeBytes;

      // Set initial values
      this.reset();
    },

    /**
     * Resets this HMAC to its initial state.
     *
     * @example
     *
     *     hmacHasher.reset();
     */
    reset: function() {
      // Shortcut
      var hasher = this._hasher;

      // Reset
      hasher.reset();
      hasher.update(this._iKey);
    },

    /**
     * Updates this HMAC with a message.
     *
     * @param {WordArray|string} messageUpdate The message to append.
     *
     * @return {HMAC} This HMAC instance.
     *
     * @example
     *
     *     hmacHasher.update('message');
     *     hmacHasher.update(wordArray);
     */
    update: function(messageUpdate) {
      this._hasher.update(messageUpdate);

      // Chainable
      return this;
    },

    /**
     * Finalizes the HMAC computation.
     * Note that the finalize operation is effectively a destructive, read-once operation.
     *
     * @param {WordArray|string} messageUpdate (Optional) A final message update.
     *
     * @return {WordArray} The HMAC.
     *
     * @example
     *
     *     var hmac = hmacHasher.finalize();
     *     var hmac = hmacHasher.finalize('message');
     *     var hmac = hmacHasher.finalize(wordArray);
     */
    finalize: function(messageUpdate) {
      // Shortcut
      var hasher = this._hasher;

      // Compute HMAC
      var innerHash = hasher.finalize(messageUpdate);
      hasher.reset();
      var hmac = hasher.finalize(this._oKey.clone().concat(innerHash));

      return hmac;
    }
  });
}());

module.exports = CryptoJS;