Arp Spoofing in Fiber with Basic Auth

Arp Spoofing is a network-layer attack where an adversary sends falsified Address Resolution Protocol messages to associate their MAC address with the IP address of another host, typically the default gateway. In a Fiber-based application that uses HTTP Basic Authentication, this attack undermines the confidentiality of credentials in two specific ways.

First, Basic Auth encodes credentials using Base64, which is not encryption. An attacker performing successful Arp Spoofing can intercept and decode these credentials easily. Because Fiber routes traffic based on the network stack, a compromised host or a malicious node on the same local network can insert itself into the communication path. The attacker can sniff cleartext credentials from intercepted requests that use the Authorization: Basic header.

Second, the combination of a stateless protocol (HTTP) and weak transport-layer assumptions can amplify the impact. If the Fiber server does not enforce TLS, an attacker who successfully spoofs ARP entries can capture session tokens or perform session hijacking. Even when TLS is used, improper certificate validation in client code can leave the channel vulnerable. The scanner’s checks for Unauthenticated LLM endpoint detection and Data Exposure do not directly test this network attack, but findings related to Encryption and Input Validation highlight whether credentials are adequately protected in transit.

To mitigate Arp Spoofing risks when using Basic Auth in Fiber, you must avoid sending credentials in cleartext and enforce strong transport security. Below are concrete, syntactically correct examples using the Fiber framework.

1. Always use HTTPS with TLS

Never deploy Basic Auth over plain HTTP. Use TLS to protect credentials from being readable even if ARP spoofing occurs. Configure your Fiber server with secure options.

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

const options = {
  key: fs.readFileSync('/path/to/private-key.pem'),
  cert: fs.readFileSync('/path/to/certificate.pem'),
};

const app = fiber();

app.get('/secure', (req, res) => {
  const auth = req.get('Authorization');
  if (!auth || !auth.startsWith('Basic ')) {
    res.status(401).send('Unauthorized');
    return;
  }
  const base64 = auth.split(' ')[1];
  const decoded = Buffer.from(base64, 'base64').toString('utf-8');
  const [user, pass] = decoded.split(':');
  if (user === 'admin' && pass === 'S3cureP@ss!') {
    res.send('Authenticated over HTTPS');
  } else {
    res.status(403).send('Forbidden');
  }
});

https.createServer(options, app).listen(3000, () => {
  console.log('HTTPS server running on port 3000');
});

2. Validate and sanitize inputs to reduce injection risks

While ARP spoofing is a network attack, validating inputs prevents additional classes of compromise that may be chained. Basic Auth credentials should be checked for malformed content before processing.

app.post('/login', (req, res) => {
  const auth = req.get('Authorization');
  if (!auth || !auth.startsWith('Basic ')) {
    return res.status(400).send('Missing authorization header');
  }
  const payload = auth.split(' ')[1];
  if (!payload) {
    return res.status(400).send('Invalid authorization token');
  }
  try {
    const decoded = Buffer.from(payload, 'base64').toString('utf-8');
    const [user, pass] = decoded.split(':');
    if (!user || !pass || user.length > 100 || pass.length > 100) {
      return res.status(400).send('Invalid credentials format');
    }
    // Proceed with authentication logic
    res.json({ user });
  } catch (e) {
    res.status(400).send('Failed to decode credentials');
  }
});

3. Use environment variables for credentials and avoid hardcoding

Hardcoded credentials increase risk if a codebase is exposed. Store sensitive values in environment variables and validate them at runtime.

require('dotenv').config();
const expectedUser = process.env.BASIC_AUTH_USER;
const expectedPass = process.env.BASIC_AUTH_PASS;

app.get('/profile', (req, res) => {
  const auth = req.get('Authorization');
  if (!auth || !auth.startsWith('Basic ')) {
    return res.status(401).send('Unauthorized');
  }
  const decoded = Buffer.from(auth.split(' ')[1], 'base64').toString();
  const [user, pass] = decoded.split(':');
  if (user === expectedUser && pass === expectedPass) {
    res.json({ profile: 'secure data' });
  } else {
    res.status(403).send('Forbidden');
  }
});

4. Complementary network-level defenses

While the above code changes address application-layer concerns, you should also consider network hardening: use VLANs to limit broadcast domains, employ static ARP entries for critical hosts where appropriate, and monitor for unusual ARP replies using network monitoring tools. These steps reduce the likelihood of a successful Arp Spoofing attack reaching your Fiber services.