Arp Spoofing in Fiber with Api Keys

Arp spoofing is a Layer 2 attack where an adversary sends falsified ARP messages to associate their MAC address with the IP address of another host, typically the gateway or an API server. In a Fiber application that relies on API keys for authorization, arp spoofing can expose those keys in transit. When a client sends an HTTP request with an API key header (e.g., apikey: {key}) over a local network under attacker control, the falsified ARP mappings can redirect traffic through the attacker’s machine. Even if the request uses TLS, the attacker can terminate and re-encrypt the connection (a form of SSL stripping or rogue proxy behavior), capturing the API key in plaintext before re-issuing it to the legitimate server. Because API keys are often static long-lived credentials, intercepted keys enable unauthorized access until rotation occurs. This is particularly risky in environments where authentication is header-based and lacks mutual TLS or additional context-bound verification, making the combination of Fiber, API keys, and an untrusted local network a notable exposure.

To mitigate arp spoofing risks when using API keys in Fiber, shift from static header keys to dynamic, short-lived tokens and enforce transport integrity. Below are concrete code examples using the Fiber framework and recommended security practices.

1. Use HTTPS with strict TLS settings

Ensure all API traffic is served over TLS and disable insecure protocols. In Fiber, enforce HTTPS and use strong cipher suites.

const https = require('https');
const fs = require('fs');
const Fiber = require('fiber');

const options = {
  key: fs.readFileSync('/path/to/private.key'),
  cert: fs.readFileSync('/path/to/certificate.crt'),
  minVersion: 'TLSv1.3',
  ciphers: 'TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256'
};

const app = require('fiber')();

app.get('/secure-endpoint', (req, res) => {
  const apiKey = req.headers['apikey'];
  if (!validateApiKey(apiKey)) {
    return res.status(401).send({ error: 'Invalid API key' });
  }
  res.send({ data: 'secure data' });
});

https.createServer(options, app).listen(443);

2. Rotate API keys frequently and avoid static keys in headers when possible

Instead of long-lived static keys, use short-lived tokens or session-based authentication. If API keys must be used, rotate them on a strict schedule and avoid embedding them in URLs or logs.

// Example of validating a short-lived key with expiration check
function validateApiKey(key) {
  const knownKeys = {
    'abc123': { expiresAt: Date.now() + 5 * 60 * 1000 }, // 5-minute window
  };
  const entry = knownKeys[key];
  return entry && entry.expiresAt > Date.now();
}

3. Add per-request nonce or timestamp to prevent replay

Require a client-supplied timestamp and nonce in headers, and reject requests with stale timestamps. This reduces the usefulness of captured keys in replay attacks that may occur via arp spoofing.

function validateApiKeyWithNonce(req) {
  const apiKey = req.headers['apikey'];
  const nonce = req.headers['x-nonce'];
  const timestamp = parseInt(req.headers['x-timestamp'], 10);

  // Reject if timestamp is older than 2 minutes
  if (Date.now() - timestamp > 2 * 60 * 1000) {
    return false;
  }
  // Verify nonce uniqueness (e.g., in a short-lived cache)
  if (seenNonces.has(nonce)) {
    return false;
  }
  seenNonces.add(nonce);

  return validateApiKey(apiKey);
}

4. Network-level mitigations

While not code, it’s important to pair application controls with network practices: use static ARP entries for critical gateway pairs where feasible, prefer TLS mutual authentication, and segment networks to limit lateral movement. These practices reduce the attack surface available for arp spoofing even if keys are intercepted.