@sskmy1024y/react-native-hash/JSHash/lib/core/HMAC.js

A hashing library for react-native

/* eslint linebreak-style: ["error", "windows"] */
/* eslint-disable no-use-before-define */

import Base from './Base.js';
import Utf8 from './Utf8.js';

/**
 * HMAC algorithm.
 */
export default class HMAC extends Base {
  /**
     * Initializes a newly created HMAC.
     *
     * @param {Hasher} SubHasher The hash algorithm to use.
     * @param {WordArray|string} key The secret key.
     *
     * @example
     *
     *     var hmacHasher = CryptoJS.algo.HMAC.create(CryptoJS.algo.SHA256, key);
     */
  constructor(SubHasher, key) {
    super();

    const hasher = new SubHasher();
    this._hasher = hasher;

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

    // Shortcuts
    const hasherBlockSize = hasher.blockSize;
    const 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
    const oKey = _key.clone();
    this._oKey = oKey;
    const iKey = _key.clone();
    this._iKey = iKey;

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

    // XOR keys with pad constants
    for (let i = 0; i < hasherBlockSize; i += 1) {
      oKeyWords[i] ^= 0x5c5c5c5c;
      iKeyWords[i] ^= 0x36363636;
    }
    oKey.sigBytes = hasherBlockSizeBytes;
    iKey.sigBytes = hasherBlockSizeBytes;

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

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

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

    return hmac;
  }
}