Insecure Direct Object Reference in Chi with Basic Auth

Insecure Direct Object Reference (BOLA/IDOR) occurs when an API exposes internal object references such as user IDs or record identifiers in URLs and does not enforce authorization checks for the authenticated subject. In Chi, this commonly arises when route parameters like :id are bound directly to handlers without verifying that the requesting user is allowed to access the resource. When Basic Auth is used, the server typically relies on an Authorization header containing a base64-encoded username:password pair. If the application decodes this header to identify the user but then uses only the user-supplied identifier to locate data, the combination creates an IDOR path: the resource exists, the user is authenticated, yet there is no logic ensuring the resource belongs to or is permitted for that user.

For example, a Chi application might parse credentials into a request context and later use a user-supplied integer to look up a database row. Without explicit authorization, any authenticated user can increment the identifier to access other users’ records. This is an unauthenticated attack surface if authentication is weak or misconfigured, because the scan tests endpoints without credentials; however, with Basic Auth present, the scanner can send the header and observe responses that differ across identifiers, revealing that direct object references are not properly constrained. Common indicators include predictable numeric IDs in URLs, verbose error messages that disclose record existence, and responses that differ only by authorization status rather than by business logic enforcement.

The scanner’s twelve parallel checks include Authentication, BOLA/IDOR, and Property Authorization, which together examine whether access controls are tied to the subject identified by Basic Auth rather than to the object alone. Findings often highlight that route parameters are used directly in queries without scoping to the authenticated user’s tenant or ownership. In OpenAPI/Swagger analyses, the spec may define a path like /users/{userId}/documents/{documentId} without clarifying that userId must match the authenticated subject’s identifier. Cross-referencing spec definitions with runtime behavior can show discrepancies where the documented parameter is not validated against the credentials derived from Basic Auth, enabling an attacker to traverse relationships and access data that should be restricted.

Real-world attack patterns mirror CVE scenarios where horizontal privilege escalation occurs due to missing ownership checks. For instance, if a handler retrieves a document by ID and returns it without confirming that the document’s user_id equals the user derived from the Basic Auth credentials, the vulnerability is effectively an IDOR. Input validation checks ensure the parameter is correctly typed, but they do not substitute for authorization. Data exposure findings may flag responses that include sensitive fields when accessed with modified identifiers, even when Basic Auth credentials are valid. This demonstrates that the vulnerability is not about authentication weakness alone, but about the authorization boundary between subjects and objects being undefined or bypassed.

Because Chi is a lightweight router, developers must explicitly enforce scoping in each route handler. The framework does not automatically bind authenticated subject context to resource ownership, so it is the developer’s responsibility to retrieve the user from the Basic Auth header and use it to filter queries. Scans that include spec-based $ref resolution can map documented parameters to runtime behavior, showing whether the implementation aligns with the declared contract. Without such alignment, IDOR risks remain even when the API appears to require authentication, because the critical link between subject and object is missing or incorrectly implemented.

Remediation focuses on ensuring that every data access is scoped to the authenticated subject derived from the Basic Auth credentials. Developers should extract the user identity early in the middleware chain and use it to constrain all subsequent queries. This prevents attackers from substituting identifiers and accessing resources that do not belong to them.

Example: Secure Chi handler with Basic Auth and ownership check

import 'dart:convert';
import 'package:chi/chi.dart';
import 'package:postgres/postgres.dart';

Future<void> main() async {
  final router = Router();

  router.get('/users/:userId/documents/:documentId', (req) async {
    // 1. Extract Basic Auth credentials
    final authHeader = req.headers['authorization'];
    if (authHeader == null || !authHeader.startsWith('Basic ')) {
      throw HttpException(401, 'Unauthorized');
    }
    final encoded = authHeader.substring('Basic '.length).trim();
    final decoded = utf8.decode(base64.decode(encoded));
    final parts = decoded.split(':');
    if (parts.length != 2) {
      throw HttpException(401, 'Invalid credentials');
    }
    final authenticatedUser = parts[0]; // e.g., 'alice'

    // 2. Parse route parameters
    final userId = req.params['userId'];
    final documentId = req.params['documentId'];

    // 3. Enforce ownership: ensure userId matches authenticated subject
    if (userId != authenticatedUser) {
      throw HttpException(403, 'Forbidden: cannot access other users\' resources');
    }

    // 4. Query with scoping to the authenticated user
    final results = await postgresConnection.query(
      'SELECT * FROM documents WHERE user_id = @user AND id = @id',
      substitutionValues: {
        'user': authenticatedUser,
        'id': documentId,
      },
    );

    if (results.isEmpty) {
      throw HttpException(404, 'Not found');
    }
    return Response.json(results.first);
  });

  // Start server omitted for brevity
}

This pattern ensures that the resource identifier is validated against the authenticated subject before any data access. The query includes both the user identity and the document identifier, so even if an attacker manipulates :documentId, they cannot access documents owned by another user because the user_id condition binds the lookup to the subject derived from Basic Auth.

Alternative: Centralized authorization helper

To reduce duplication across routes, encapsulate the ownership check in a helper that uses the request context. This keeps route handlers clean and ensures consistent scoping.

class AuthContext {
  final String user;
  AuthContext(this.user);
}

Future<AuthContext> extractAuthContext(Request req) async {
  final authHeader = req.headers['authorization'];
  if (authHeader == null || !authHeader.startsWith('Basic ')) {
    throw HttpException(401, 'Unauthorized');
  }
  final decoded = utf8.decode(base64.decode(authHeader.substring('Basic '.length).trim()));
  final parts = decoded.split(':');
  if (parts.length != 2) {
    throw HttpException(401, 'Invalid credentials');
  }
  return AuthContext(parts[0]);
}

// Usage in handler:
router.get('/records/:recordId', (req) async {
  final auth = await extractAuthContext(req);
  final recordId = req.params['recordId'];
  final row = await postgresConnection.query(
    'SELECT * FROM records WHERE owner = @owner AND id = @id',
    substitutionValues: {'owner': auth.user, 'id': recordId},
  );
  if (row.isEmpty) {
    throw HttpException(404, 'Not found');
  }
  return Response.json(row.first);
});

These examples demonstrate concrete remediation that aligns with the scanner’s findings. By correlating the authenticated subject from Basic Auth with the resource identifier in queries, developers close the IDOR vector. The middleBrick CLI can be used to verify that such scoping is present by scanning the endpoint with valid Basic Auth credentials and checking that modified identifiers do not yield different data. For teams using the Pro plan, continuous monitoring helps detect regressions where ownership checks might be accidentally removed in future changes.