square webhook validate signature

// The crypto module provides cryptographic functionality
const crypto = require('crypto');

// const body = JSON.stringify(req.body);
// const signature = req.header('x-square-signature');

function isValidSignature(body, url, signature) {
  // Concatenate your notification URL and
  // the JSON body of the webhook notification
  const combined = url + body;

  // Webhook subscription signature key defined in dev portal for app 
  // webhook listener endpoint: https://webhook.site/my-listener-endpoint
  // Note: Signature key is truncated for illustration
  const signatureKey = 'uTYf8X...0HGvYg';

  // Generate the HMAC-SHA1 signature of the string
  // signed with your webhook signature key
  const hmac = crypto.createHmac('sha1', signatureKey);
  hmac.write(combined)
  hmac.end()
  const checkHash = hmac.read().toString('base64');
    
  // Compare HMAC-SHA1 signatures.
  if (checkHash === signature) {
    console.log('Validation success!');
  } else {
    console.log('Validation error.');
  }
}