landing_signature_check_node.js

const crypto = require('crypto');

module.exports = (secretKey, ttl, signature) => {
  try {
    let sign = Buffer.from(signature, 'base64').toString('utf8');
    sign = JSON.parse(sign);

    if (!sign.timestamp || !sign.hash) return false;

    const signedHash = crypto
      .createHmac('sha1', secretKey)
      .update(sign.timestamp)
      .digest('hex');

    if (signedHash !== sign.hash || sign.timestamp < (((new Date().getTime() / 1000) | 0) - ttl).toString()) return false;

    return true;
  } catch (err) {
    return false;
  }
};