Arp Spoofing in Feathersjs with Api Keys

Arp spoofing is a Layer 2 network attack where an attacker sends falsified ARP messages to associate their MAC address with the IP address of another host, typically the gateway or another service. In a FeathersJS application that relies on API keys for authentication, this attack can undermine transport-layer trust by allowing an attacker to intercept or modify unencrypted traffic between the client and the server. FeathersJS is a framework for real-time applications that often exposes REST and WebSocket endpoints; if API keys are passed in headers over a compromised local network, an attacker positioned via ARP spoofing can observe and replay those keys.

The combination is risky when the network perimeter is not trusted, such as in shared environments (e.g., co-working spaces or public Wi-Fi), or when internal segmentation is weak. An attacker conducting ARP spoofing does not need to exploit application logic; they simply redirect traffic through their host. If the FeathersJS service authenticates solely via API keys in headers and does not enforce TLS, intercepted keys can be reused to impersonate clients. Even when TLS is present, ARP spoofing can facilitate SSL stripping or redirect users to malicious endpoints if certificate validation is not strict, potentially exposing API key exchanges to passive collection.

Importantly, middleBrick’s unauthenticated scan checks for Data Exposure and Encryption as part of its 12 parallel security checks, which can surface services that transmit API keys without adequate transport protection. While middleBrick does not perform active ARP spoofing, it can detect whether API key transmission occurs over connections that lack strong encryption or show indicators of insecure configurations. This detection helps highlight scenarios where network-layer attacks like ARP spoofing could lead to credential compromise.

To mitigate ARP spoofing risks when using API keys in FeathersJS, focus on ensuring that all API key transmission occurs exclusively over authenticated and encrypted channels, and that keys are validated server-side with minimal exposure. The following patterns demonstrate secure handling of API keys in FeathersJS services.

Enforce TLS and secure transport

Ensure your FeathersJS server is behind a termination or proxy that enforces HTTPS. Never accept API keys over plain HTTP. Configure your server to redirect HTTP to HTTPS and set secure headers.

// src/index.js
const feathers = require('@feathersjs/feathers');
const express = require('@feathersjs/express');
const app = express(feathers());

// Enforce secure headers and HTTPS redirect in production
app.use((req, res, next) => {
  if (process.env.NODE_ENV === 'production' && !req.secure) {
    return res.redirect('https://' + req.headers.host + req.url);
  }
  next();
});

app.use('/api', require('./services'));

app.listen(443).on('listening', () => {
  console.log('Feathers server over HTTPS on port 443');
});

Validate API keys via a service hook with constant-time comparison

Use a service hook to validate API keys stored securely (e.g., hashed in a database). Avoid passing keys in URLs or logging them. Use constant-time comparison to prevent timing attacks that could be amplified in a spoofed environment.

// src/services/authentication/hook.js
const crypto = require('crypto');

// Constant-time comparison helper
function safeCompare(a, b) {
  if (a.length !== b.length) return false;
  let result = 0;
  for (let i = 0; i < a.length; i++) {
    result |= a.charCodeAt(i) ^ b.charCodeAt(i);
  }
  return result === 0;
}

module.exports = function () {
  return async context => {
    const { apikey } = context.data; // Assume passed securely in body for this example
    const storedKeyHash = context.params.user.apiKeyHash; // Retrieved from DB

    if (!apikey || !storedKeyHash || !safeCompare(
      crypto.createHash('sha256').update(apikey).digest('hex'),
      storedKeyHash
    )) {
      throw new Error('Invalid API key');
    }

    // Attach user or remove key from context to avoid accidental exposure
    context.params.apikey = undefined;
    return context;
  };
};

Require secure channels for WebSocket transports

If your FeathersJS app uses real-time transports, ensure WebSocket connections are secured (wss://) and that API keys are not embedded in query strings that could be logged or exposed via ARP spoofing.

// src/index.js (transport configuration)
const app = require('./app');

app.configure(express.rest());
app.configure(express.socketio({
  path: '/ws',
  cors: {
    origin: process.env.FRONTEND_ORIGIN,
    credentials: true
  },
  handlePreflightRequest: (req, res) => {
    res.writeHead(200, {
      'Access-Control-Allow-Origin': process.env.FRONTEND_ORIGIN,
      'Access-Control-Allow-Credentials': true,
      'Access-Control-Allow-Methods': 'GET,POST,OPTIONS',
      'Access-Control-Allow-Headers': 'Authorization,Content-Type'
    });
    res.end();
  }
}));

// Ensure socket authentication hook
app.io.use(async (socket, next) => {
  const apikey = socket.handshake.auth?.apikey;
  if (!apikey) return next(new Error('Authentication required'));
  // Validate key via hook or service; example omitted for brevity
  const isValid = await validateApiKey(apikey);
  if (!isValid) return next(new Error('Invalid API key'));
  next();
});