Secure Code Review (SCR) : A4 Insecure Direct Object Reference

Insecure Direct Object References (IDOR) is a common security vulnerability that occurs when a developer exposes a reference to an internal implementation object, such as a file, directory, or database key, in a URL or form parameter. Attackers can manipulate these references to gain unauthorized access to data. In this blog, we will delve into the details of IDOR, provide examples, and offer a checklist for identifying this vulnerability during a secure code review.

Understanding Insecure Direct Object References

Insecure Direct Object References occur when an application provides direct access to objects based on user-supplied input. As a result, attackers can bypass authorization and directly access resources in the system.

For example, consider a URL that references an internal object like this: http://example.com/app/accountInfo?acct=12345. An attacker could change the acct parameter value to 12346 to access another user's account.

Identifying Insecure Direct Object References in Code Review

During a secure code review, it’s crucial to identify places where user-supplied input might be used to construct direct references to internal objects. Here are some things to look for:

1. User Input in Object References: Look for instances where user-supplied input is used to reference objects directly. This could be in URLs, form parameters, or hidden fields.
2. Lack of Access Control Checks: Check if the application verifies the user’s rights to access the targeted object. The absence of such checks is a clear sign of potential IDOR vulnerability.
3. Inadequate Input Validation: Ensure that the application properly validates user-supplied input. It should reject any input that may reference unauthorized objects.

Secure Code Review Checklist for IDOR

Here’s a checklist to follow when reviewing code for Insecure Direct Object References:

1. Identify all points in the application where user input is used to access data objects.
2. Check if the application performs any access control checks before allowing the user to access the object.
3. Verify if the application validates and sanitizes user input before using it to access objects.
4. Look for any hidden fields or URL parameters that contain direct object references. Check if these can be manipulated to access unauthorized data.
5. Review the application’s error handling. Ensure that it does not reveal any sensitive information when an unauthorized access attempt is made.

Mitigating Insecure Direct Object References

To prevent IDOR vulnerabilities, follow these best practices:

1. Use Indirect Object References: Instead of using direct references to objects, use indirect references that are mapped to the user’s session. This way, the application can validate the user’s access rights before allowing access to the object.
2. Implement Access Control Checks: Always check if the user is authorized to access the object before allowing access.
3. Validate User Input: Validate and sanitize user input to ensure that it does not contain any unauthorized object references.

In conclusion, Insecure Direct Object References can lead to serious data breaches if not properly handled. By conducting a thorough secure code review and following the best practices outlined above, you can significantly reduce the risk of IDOR vulnerabilities in your application.

Thanks for your time!!!

References:

1. https://owasp.org/www-project-code-review-guide/assets/OWASP_Code_Review_Guide_v2.pdf