Insecure Direct Object Reference

Insecure Direct Object Reference (IDOR)

Definition:

Insecure Direct Object Reference (IDOR) occurs when an attacker is able to access or modify objects (like files, database entries, etc.) they aren't supposed to by manipulating input parameters, usually because the application lacks proper authorization checks.

Key Points:

• IDOR vulnerabilities arise when an application uses user-supplied input to access objects directly.

• IDOR can lead to unauthorized data access, data manipulation, and in some cases, even full system compromise.

Typical Scenario:

Imagine a web application that displays a user's profile based on the user ID in the URL, e.g., https://example.com/profile?userid=1234. If proper authorization checks aren't in place, an attacker might change userid to 1235 to access someone else's profile.

Common Attack Vectors:

1. URL Parameters: As in the example above, manipulating parameters in the URL.

2. Hidden Form Fields: Applications might use hidden fields to store object references, which can be modified by an attacker.

3. JSON Web Tokens (JWT): If object references are stored in JWTs without adequate protection, they can be vulnerable to IDOR.

4. API Endpoints: Changing values in API requests can expose or modify other users' data.

Mitigation:

1. Always Authenticate and Authorize: Even if an identifier (like userid) is hard to guess, always check that the user making the request has the right to access or modify the resource.

2. Avoid Exposing Direct Object References: Instead of using actual database IDs or direct file names, use mapped values or indices that are valid only for that specific user session.

3. Limit Data Exposure: Use the principle of least privilege. Only provide data or access if it's necessary for the functionality.

4. Monitor and Log: Keep track of failed attempts to access resources, which might indicate an attacker trying to exploit IDOR.

5. Rate Limiting: Implement rate limiting on sensitive endpoints to limit the attacker's ability to enumerate and access resources.

Example of IDOR:

Imagine a banking application where a user can view their transaction details by visiting a URL like: https://bank.example.com/transaction?id=5678. If authorization checks aren't in place, an attacker logged into their account might change the transaction id to view details of someone else's transaction, leading to sensitive data exposure.

Detection:

1. Manual Testing:

   • Penetration testers can manipulate parameters in URLs, hidden form fields, API endpoints, etc., to try and access or modify resources they shouldn't have access to.

2. Automated Scanning:

   • Use automated vulnerability scanners, but note that IDOR vulnerabilities often require human intuition to detect, making manual testing crucial.

Conclusion:

IDOR is a serious vulnerability that exposes sensitive data and functionalities to attackers. It stems from a lack of proper authorization checks when accessing application resources. Developers need to ensure that, regardless of the input source (URL, form fields, headers, etc.), they're verifying the authenticity and authorization of the user before granting access or making changes. Proper implementation of security controls and regular security testing can help in preventing IDOR vulnerabilities.