Broken Authentication in Restify with Firestore

Broken Authentication in a Restify service that uses Firestore typically occurs when session handling, token validation, or access controls are implemented incorrectly, allowing attackers to bypass authentication or escalate privileges. Restify is a Node.js web framework commonly used to build APIs, and when it integrates with Google Cloud Firestore, developers must ensure that every authenticated request is properly verified and scoped.

One common pattern is using Firebase Admin SDK with service account credentials on the server. If Restify endpoints incorrectly trust client-supplied identifiers (such as user IDs in URLs or tokens that are not validated), this can lead to Insecure Direct Object References (IDOR) or Broken Object Level Authorization (BOLA). For example, an endpoint like /users/:userId/profile that retrieves a Firestore document without verifying that the authenticated subject matches userId allows horizontal privilege escalation.

Another risk arises when custom authentication tokens or ID tokens are passed from a client to a Restify route and are decoded or verified in an unsafe way. If the server skips signature validation or fails to validate the token’s audience and issuer, an attacker can forge a token and gain unauthorized access. Firestore security rules alone are not sufficient when the backend does not enforce identity checks; rules are bypassed if the backend trusts the client implicitly.

Session fixation and weak session storage can also contribute to broken authentication. If Restify stores session identifiers in non-secure cookies or does not rotate tokens after login, attackers can steal or predict session tokens. Additionally, misconfigured CORS settings in Restify can allow unauthorized origins to interact with authenticated endpoints, further exposing authentication mechanisms.

When using Firestore, ensure that tokens are verified using the Firebase Admin SDK and that the authenticated UID is used to scope all database queries. For example, avoid querying documents by only a client-provided ID without cross-checking against the authenticated user’s identity. Continuous scanning with middleBrick can detect these misconfigurations in unauthenticated attack surface tests, highlighting authentication weaknesses before they are exploited.

To remediate broken authentication when using Restify and Firestore, always verify Firebase ID tokens on the server and bind the authenticated user to each Firestore operation. Below is a secure Restify handler that demonstrates this pattern.

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

const app = initializeApp({
  credential: cert({
    projectId: process.env.FIREBASE_PROJECT_ID,
    clientEmail: process.env.FIREBASE_CLIENT_EMAIL,
    privateKey: process.env.FIREBASE_PRIVATE_KEY.replace(/\\n/g, '\n'),
  }),
});
const db = getFirestore(app);

const server = restify.createServer();
server.use(restify.plugins.bodyParser());

server.get('/profile', async (req, res, next) => {
  try {
    const authHeader = req.headers.authorization;
    if (!authHeader || !authHeader.startsWith('Bearer ')) {
      return res.send(401, { error: 'Unauthorized' });
    }
    const idToken = authHeader.split('Bearer ')[1];
    const decodedToken = await admin.auth().verifyIdToken(idToken);
    const uid = decodedToken.uid;

    const userDoc = await db.collection('users').doc(uid).get();
    if (!userDoc.exists) {
      return res.send(404, { error: 'Profile not found' });
    }
    res.send(200, userDoc.data());
    return next();
  } catch (err) {
    return res.send(401, { error: 'Invalid token' });
  }
});

server.listen(8080, () => {
  console.log('Server listening on port 8080');
});

This example verifies the ID token using the Firebase Admin SDK, extracts the UID, and uses it to scope the Firestore read to that user’s document. Never use a client-provided user ID to directly reference a document without this verification step.

For endpoints that require role-based checks, store roles in Firestore and validate them server-side. For example:

server.get('/admin/settings', async (req, res, next) =>
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith('Bearer ')) {
    return res.send(401, { error: 'Unauthorized' });
  }
  const idToken = authHeader.split('Bearer ')[1];
  const decodedToken = await admin.auth().verifyIdToken(idToken);
  const uid = decodedToken.uid;

  const userDoc = await db.collection('users').doc(uid).get();
  if (!userDoc.exists) {
    return res.send(404, { error: 'User not found' });
  }
  const userData = userDoc.data();
  if (userData.role !== 'admin') {
    return res.send(403, { error: 'Insufficient permissions' });
  }

  const settingsDoc = await db.collection('settings').doc('global').get();
  res.send(200, settingsDoc.data());
  return next();
});

Additionally, enforce token expiration checks and use short-lived ID tokens where possible. Configure Restify to reject requests with missing or malformed authorization headers. middleBrick’s authentication checks can validate that your endpoints consistently enforce token verification and scope data access to the authenticated subject.