Broken Access Control

Broken Access Control is a security vulnerability that occurs when an application fails to properly enforce restrictions on what authenticated users are allowed to access or modify. This vulnerability allows attackers to bypass authorization mechanisms and gain unauthorized access to sensitive data or functionality. Below, I'll explain Broken Access Control in detail and provide examples of scenarios where it can occur.

Understanding Broken Access Control:

Broken Access Control vulnerabilities arise from weaknesses in the enforcement of access controls within web applications. These weaknesses can manifest in various forms, such as insufficient authorization checks, insecure direct object references, missing access controls on sensitive functions, predictable resource identifiers, or improper session management.

Example Scenarios of Broken Access Control:

1. Unprotected Admin Functionality: Consider a web application that includes administrative functionality accessible at http://example.com/admin. If the application fails to enforce proper access controls, any authenticated user may access this administrative interface, potentially leading to unauthorized modifications to system settings or sensitive data.

2. Insecure Direct Object Reference (IDOR): As mentioned earlier, Insecure Direct Object Reference (IDOR) is a form of Broken Access Control where an attacker can manipulate parameters, such as URLs or form fields, to access unauthorized resources. For example, an attacker might change a URL parameter to access another user's account or confidential information.

3. Predictable Resource Identifiers: Some applications use predictable identifiers for sensitive resources, such as session tokens, user IDs, or file paths. If these identifiers are easy to guess or manipulate, attackers can bypass access controls and gain unauthorized access to sensitive data or functionality.

4. Missing Function-Level Access Controls: In some cases, applications may lack proper access controls on specific functions or API endpoints, allowing authenticated users to perform privileged actions they should not be allowed to. For example, an e-commerce application may allow any authenticated user to access an endpoint for updating product prices without proper authorization checks.

Vulnerable Code Example:

<?php
// admin.php - Example of Broken Access Control
session_start();

// Check if user is logged in
if (!isset($_SESSION['user'])) {
    header('Location: login.php');
    exit;
}

// Display admin panel...
?>

Explanation of Vulnerability:

In the above code example, the application only checks if the user is logged in and but don't verifies if the user has an administrator role. By only using directory forcing, they may be able to access the administrative functionality without proper checks.

Mitigation Strategies:

To prevent Broken Access Control vulnerabilities, developers should implement the following best practices:

1. Enforce Proper Access Controls: Ensure that access controls are properly enforced at both the function and data levels throughout the application.

2. Implement Role-Based Access Controls (RBAC): Use RBAC to define roles and permissions for different user groups and restrict access to sensitive functionality accordingly.

3. Apply Principle of Least Privilege: Grant users only the permissions necessary to perform their intended tasks and restrict access to sensitive resources or functionality whenever possible.

4. Regular Security Reviews: Conduct regular security reviews and code audits to identify and address access control vulnerabilities proactively.