Arp Spoofing in Hapi with Firestore

Arp Spoofing is a Layer 2 attack where an attacker sends falsified Address Resolution Protocol messages to associate their MAC address with the IP of a legitimate host, such as a Firestore endpoint or an API server running Hapi. When this happens, traffic that should go to Firestore is instead routed through the attacker’s machine, enabling interception or manipulation of unencrypted or improperly protected data. This is particularly relevant when Hapi services interact with Google Cloud Firestore over local networks or less-secured virtual environments where ARP trust is implicit.

In a Hapi-based application, server routes are often long-lived and handle multiple request streams, increasing the window of exposure if an attacker successfully spoofs the ARP table of a client or another service within the same subnet. If the application communicates with Firestore using HTTP calls from the Hapi server or from a client-side application served by Hapi, an attacker on the same network can redirect those calls to a malicious host that may proxy or alter requests before forwarding them to the real Firestore instance. This can expose sensitive document reads or writes, especially if additional protections such as per-request authentication tokens or IP-based rules are weak or absent.

The risk is compounded when Firestore security rules rely solely on request origin IPs or when tokens are passed in headers that can be intercepted post-ARP manipulation. Because Firestore does not inherently validate the network path of requests, any trust placed in the local network’s ARP responses becomes a potential vector. Hapi applications that do not enforce transport layer encryption or mutual TLS for backend-to-Firestore communication may inadvertently allow a spoofed node to observe or modify payloads containing database operations, user identifiers, or configuration data.

Using middleBrick’s unauthenticated black-box scans, such network-based weaknesses can be detected in the Encryption and SSRF security checks, which assess whether communications are adequately protected and whether internal endpoints are inadvertently exposed. While middleBrick does not fix these issues directly, its findings include remediation guidance to harden the network path, enforce encryption, and validate server identity to mitigate ARP spoofing risks in Hapi and Firestore integrations.

To reduce the impact of ARP spoofing when Hapi services communicate with Firestore, implement cryptographic and network-layer protections that do not depend on the integrity of local ARP responses. Prefer HTTPS with strict certificate validation for all Firestore requests, and avoid relying on IP-based trust alone. Where possible, use environment-bound service accounts and restrict Firestore rules to only necessary operations and authenticated users.

Below are concrete Hapi server examples using the Firebase Admin SDK and the Google Cloud Firestore client library for Node.js, demonstrating secure request handling and scoped permissions.

Example 1: Hapi route with verified Firestore access using service account isolation

const Hapi = require('@hapi/hapi');
const { initializeApp, cert } = require('firebase-admin/app');
const { getFirestore } = require('firebase-admin/firestore');

const initializeFirebase = () => {
  if (!initializeApp.apps.length) {
    initializeApp({
      credential: cert({
        projectId: process.env.FIREBASE_PROJECT_ID,
        clientEmail: process.env.FIRESTORE_CLIENT_EMAIL,
        privateKey: process.env.FIRESTORE_PRIVATE_KEY.replace(/\\n/g, '\n'),
      }),
    });
  }
};

const server = Hapi.server({ port: 4000, host: 'localhost' });

server.route({
  method: 'GET',
  path: '/api/notes/{id}',
  handler: async (request, h) => {
    initializeFirebase();
    const db = getFirestore();
    const docRef = db.collection('notes').doc(request.params.id);
    const doc = await docRef.get();
    if (!doc.exists) {
      return h.response({ error: 'Not found' }).code(404);
    }
    return doc.data();
  },
});

server.start().console();

Example 2: Hapi route with user-scoped Firestore rules enforcement

const Hapi = require('@hapi/hapi');
const { initializeApp, cert } = require('firebase-admin/app');
const { getFirestore } = require('firebase-admin/firestore');

const initializeFirebase = () => {
  if (!initializeApp.apps.length) {
    initializeApp({
      credential: cert({
        projectId: process.env.FIREBASE_PROJECT_ID,
        clientEmail: process.env.FIRESTORE_CLIENT_EMAIL,
        privateKey: process.env.FIRESTORE_PRIVATE_KEY.replace(/\\n/g, '\n'),
      }),
    });
  }
};

const server = Hapi.server({ port: 4000, host: 'localhost' });

server.route({
  method: 'POST',
  path: '/api/notes',
  handler: async (request, h) => {
    initializeFirebase();
    const db = getFirestore();
    const userId = request.auth.credentials.userId;
    const noteData = request.payload;
    const notesRef = db.collection('users').doc(userId).collection('notes');
    const docRef = notesRef.doc();
    await docRef.set({
      ...noteData,
      createdAt: new Date(),
      userId,
    });
    return docRef.get().then(d => d.data());
  },
});

server.auth.strategy('session', 'cookie', {
  password: process.env.COOKIE_PASSWORD,
  isSecure: process.env.NODE_ENV === 'production',
});

server.auth.default('session');

server.start().console();

Network and configuration recommendations

• Enforce HTTPS for all external communications and use certificate pinning where feasible.
• Restrict Firestore database rules to authenticated users and apply principle of least privilege.
• Run Hapi services inside private subnets when possible and avoid exposing Firestore ports to public internet.
• Rotate service account keys regularly and monitor usage for anomalies using Cloud Audit Logs.

These measures reduce the effectiveness of ARP spoofing by ensuring that even if an attacker intercepts traffic, they cannot read or modify authenticated requests without valid credentials and TLS termination at the server side. middleBrick scans can help verify that such protections are visible in the exposed attack surface.