git.squeep.com Git - squeep-totp/blob - lib/totp.js

   1 'use strict';
   2
   3 const HOTP = require('./hotp');
   4
   5 class TimeBasedOneTimePassword extends HOTP {
   6   /**
   7    *
   8    * @param {object} options options
   9    * @param {number} options.codeLength digits in code
  10    * @param {Buffer|string} options.key secret key
  11    * @param {string} options.keyEncoding secret key encoding
  12    * @param {string} options.algorithm algorithm
  13    * @param {number} options.timeStepSeconds seconds per increment
  14    * @param {number} options.timeStepStartSeconds seconds offset
  15    * @param {number} options.driftForward allowed future steps to check
  16    * @param {number} options.driftBackward allowed past steps to check
  17    */
  18   constructor(options) {
  19     const _options = { ...options };
  20     super(_options);
  21     this.driftOffsets = [
  22       0n, // Check now first
  23       ...Array.from({ length: this.driftBackward }, (v, k) => BigInt(-(k + 1))),
  24       ...Array.from({ length: this.driftForward }, (v, k) => BigInt(k + 1)),
  25     ];
  26   }
  27
  28   static get _algorithmKeyLengths() {
  29     return {
  30       ...super._algorithmKeyLengths,
  31       'sha256': 32,
  32       'sha512': 64,
  33     };
  34   }
  35
  36   /**
  37    * The type used when constructing the otpauth URI.
  38    * @returns {string} otp auth type
  39    */
  40   static get _type() {
  41     return 'totp';
  42   }
  43
  44   /**
  45    * Derive counter from epoch.
  46    * @returns {bigint} time based counter
  47    */
  48   get counter() {
  49     const epoch = Math.floor(Date.now() / 1000);
  50     return BigInt(Math.floor((epoch - this.timeStepStartSeconds) / this.timeStepSeconds));
  51   }
  52
  53   set counter(_) { /* Ignore assignment */ } // eslint-disable-line class-methods-use-this
  54
  55   static get _defaultOptions() {
  56     const options = Object.assign(super._defaultOptions, {
  57       timeStepSeconds: 30,
  58       timeStepStartSeconds: 0,
  59       driftForward: 1,
  60       driftBackward: 1,
  61     });
  62     delete options.counter;
  63     return options;
  64   }
  65
  66   /**
  67    *
  68    * @param {bigint=} count counter value
  69    * @returns {string} code
  70    */
  71   generate(count = this.counter) {
  72     return super.generate(count);
  73   }
  74
  75   /**
  76    *
  77    * @param {string} hotp code
  78    * @param {bigint=} count counter value
  79    * @returns {boolean} is valid
  80    */
  81   validate(hotp, count) {
  82     const counter = count ?? this.counter;
  83     for (const offset of this.driftOffsets) {
  84       const codeString = this.generate(counter + offset);
  85       if (codeString === hotp.trim()) {
  86         return true;
  87       }
  88     }
  89     return false;
  90   }
  91
  92 }
  93
  94 module.exports = TimeBasedOneTimePassword;