Security Considerations

// Node.js example for verifying webhook signatures
const crypto = require('crypto');

function verifyWebhookSignature(payload, signature, secret) {
  // Get the signature provided in the X-Signature header
  const providedSignature = signature;

  // Compute the HMAC signature of the payload using your webhook secret
  const computedSignature = crypto
    .createHmac('sha256', secret)
    .update(payload)
    .digest('hex');

  // Use timing-safe comparison to prevent timing attacks
  return crypto.timingSafeEqual(
    Buffer.from(providedSignature, 'hex'),
    Buffer.from(computedSignature, 'hex')
  );
}

// Express.js route example
app.post('/webhooks/twocoin', express.raw({type: 'application/json'}), (req, res) => {
  const signature = req.headers['x-signature'];
  const payload = req.body;

  // Verify the signature
  if (!verifyWebhookSignature(payload, signature, process.env.WEBHOOK_SECRET)) {
    return res.status(401).send('Invalid signature');
  }

  // Process the webhook payload
  const event = JSON.parse(payload);

  // Handle different event types
  switch(event.type) {
    case 'order.completed':
      // Process completed order
      break;
    case 'order.failed':
      // Handle failed order
      break;
    default:
      // Handle other event types
  }

  // Always respond with 200 OK to acknowledge receipt
  res.status(200).send('Webhook received');
});

// Example CSP header that allows TwoCoin widget iframe
Content-Security-Policy: default-src 'self'; frame-src 'self' https://your-widget-domain.com;

// Example: Client-side validation before submitting the wallet address
function validateWalletAddress(address, currency) {
  // Basic validation patterns
  const patterns = {
    'BTC': /^(bc1|[13])[a-zA-HJ-NP-Z0-9]{25,62}$/,
    'ETH': /^0x[a-fA-F0-9]{40}$/,
    'XRP': /^r[0-9a-zA-Z]{24,34}$/
  };

  // Check if we have a pattern for this currency
  if (!patterns[currency]) {
    return true; // Skip validation for unsupported currencies
  }

  // Test the address against the pattern
  return patterns[currency].test(address);
}

// Use during form submission
document.getElementById('exchange-form').addEventListener('submit', function(event) {
  const address = document.getElementById('wallet-address').value;
  const currency = document.getElementById('target-currency').value;

  if (!validateWalletAddress(address, currency)) {
    event.preventDefault();
    alert('Please enter a valid ' + currency + ' wallet address.');
  }
});