Bola Idor in Fiber with Basic Auth

Broken Object Level Authorization (BOLA) occurs when an API fails to enforce proper ownership or authorization checks between objects that should be isolated for different users. In Fiber, a BOLA vulnerability can emerge when endpoints that operate on resource IDs do not validate that the authenticated user is permitted to access or modify the specific object. This becomes especially risky when Basic Auth is used for authentication.

With Basic Auth, the client sends an Authorization: Basic base64(username:password) header on every request. Fiber can read this header and extract credentials, but if route handlers then use the authenticated identity to locate user-specific data without confirming that the requested resource belongs to that identity, the API conflates authentication with proper authorization. For example, an endpoint like /users/:userID/profile might trust req.params.userID directly after confirming a valid Basic Auth header, allowing an attacker to increment or guess another user’s ID and view or alter their profile. Because Basic Auth lacks built-in scoping, the server must explicitly map the decoded username to the correct database record and compare it to the target resource. Omitting this comparison creates a horizontal BOLA: authenticated but unauthorized access across different users’ objects.

Consider an endpoint that retrieves an order by ID after validating Basic Auth credentials:

// Insecure example: missing ownership check after Basic Auth validation
app.get('/orders/:id', (req, res) => {
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith('Basic ')) {
    return res.status(401).send('Unauthorized');
  }
  const decoded = Buffer.from(authHeader.slice(6), 'base64').toString('ascii');
  const [username, password] = decoded.split(':');
  // Validate username/password against a user store (simplified)
  const user = validateUser(username, password);
  if (!user) {
    return res.status(401).send('Invalid credentials');
  }
  // Vulnerable: no check that the order belongs to the authenticated user
  const order = db.getOrderById(parseInt(req.params.id));
  if (!order) {
    return res.status(404).send('Not found');
  }
  res.json(order);
});

Here, authentication succeeds, but the application never confirms that order.userId matches user.id. An attacker who knows or guesses another order ID can read or manipulate it. This is a classic horizontal BOLA across the orders collection. In a vertical privilege escalation scenario, a similar pattern can appear in admin routes where Basic Auth identifies a regular user, but the handler mistakenly grants elevated permissions because it trusts the presence of credentials rather than roles. The combination of Fiber’s flexible routing, Basic Auth’s simplicity, and missing object-level checks creates a path for unauthorized data access or modification across user boundaries.

Because Basic Auth transmits credentials on every request, logging and monitoring become important to detect enumeration attempts on resource IDs. However, detection does not prevent the vulnerability; explicit ownership checks at the handler level are required. middleBrick’s scans can surface this class of issue by correlating authentication mechanisms with missing authorization checks in route implementations, highlighting where object-level boundaries are not enforced.

To remediate BOLA when using Basic Auth in Fiber, enforce strict ownership validation and avoid relying on client-supplied IDs alone. Always map the authenticated subject to the resource they are allowed to access, and use server-generated identifiers where possible.

First, ensure credentials are validated and the user identity is tied to a data record. Then, before returning or modifying a resource, compare the resource’s owning user ID with the authenticated user’s ID:

// Secure example: validate ownership after Basic Auth
app.get('/orders/:id', async (req, res) => {
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith('Basic ')) {
    return res.status(401).send('Unauthorized');
  }
  const decoded = Buffer.from(authHeader.slice(6), 'base64').toString('ascii');
  const [username, password] = decoded.split(':');
  const user = await validateUserAndRole(username, password);
  if (!user) {
    return res.status(401).send('Invalid credentials');
  }
  const orderId = parseInt(req.params.id);
  const order = await db.getOrderById(orderId);
  if (!order) {
    return res.status(404).send('Not found');
  }
  // Critical ownership check: ensure the order belongs to the authenticated user
  if (order.userId !== user.id) {
    return res.status(403).send('Forbidden');
  }
  res.json(order);
});

Use server-generated IDs for resources so that clients cannot easily guess other valid IDs. If you must expose sequential IDs, consider mapping them to opaque identifiers or enforcing strict access control lists. Additionally, apply consistent middleware to verify permissions for all routes that operate on user-specific resources. middleBrick’s scans can help identify endpoints where authentication is present but object-level authorization is missing, guiding you to these critical checks.

For applications using role-based access, extend the checks to verify permissions rather than mere ownership:

// Example with role-based checks in addition to ownership
app.delete('/users/:userId', async (req, res) => {
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith('Basic ')) {
    return res.status(401).send('Unauthorized');
  }
  const decoded = Buffer.from(authHeader.slice(6), 'base64').toString('ascii');
  const [username, password] = decoded.split(':');
  const adminUser = await validateUserAndRole(username, password);
  if (!adminUser || adminUser.role !== 'admin') {
    return res.status(403).send('Insufficient permissions');
  }
  const userId = parseInt(req.params.userId);
  // Admins may delete users, but still validate existence and log appropriately
  const targetUser = await db.getUserById(userId);
  if (!targetUser) {
    return res.status(404).send('Not found');
  }
  await db.deleteUser(userId);
  res.status(204).end();
});

These patterns ensure that even when Basic Auth confirms identity, each operation validates that the authenticated subject has the necessary rights for the specific object. Combine this with transport-layer encryption and careful logging to reduce risk. middleBrick’s continuous monitoring and CI/CD integration can help catch regressions early, while the dashboard and alerts keep your API security posture visible over time.

• Does using Basic Auth over HTTPS prevent BOLA?

  No. Transport encryption protects credentials in transit, but it does not enforce object-level permissions. BOLA is about authorization, not confidentiality of credentials. You must still validate ownership or roles on every request.

• Can middleBrick detect BOLA when Basic Auth is used?

  Yes. middleBrick scans unauthenticated attack surfaces and can identify endpoints where resource IDs are exposed without proper ownership checks, even when Basic Auth is present. Findings include remediation guidance to add server-side authorization mapping and strict access controls.