otp-io/dist/hotp.js

🕖 Typed library to work 2fa via Google Authenticator/Time-based TOTP/Hmac-based HOTP

'use strict';const bytes=require('./bytes.js'),hotp_options=require('./hotp.options.js');/**
 * Generates HOTP code from secret key, counter and options
 *
 * @export
 * @param {Hmac} hmac
 * @param {HOTPOptions} options
 * @return {Promise<string>}
 */
async function hotp(hmac, options) {
    const merged = Object.assign(Object.assign({}, hotp_options.getDefaultHOTPOptions()), options);
    const digest = await hmac(merged.algorithm, merged.secret.bytes, bytes.getBigIntBytes(merged.counter));
    const offset = digest[digest.length - 1] & 0xf;
    const view = new DataView(digest.buffer);
    const binary = view.getUint32(offset) & 2147483647;
    return binary.toString().slice(-merged.digits);
}exports.hotp=hotp;