Broken Access Control Testing Workflow

This document outlines a comprehensive workflow for testing websites for broken access control vulnerabilities. Follow these steps to systematically test and identify potential security weaknesses in a web application's access control mechanisms.

Table of Contents

1. Introduction
2. Pre-requisites
3. Understanding Access Control
4. Types of Broken Access Control Vulnerabilities
5. Testing Workflow
   • 1. Identify Entry Points
   • 2. Check for Unauthenticated Access
   • 3. Test for Role-Based Access Control (RBAC)
   • 4. Bypass Business Logic Controls
   • 5. Test URL Manipulation and Insecure Direct Object References (IDOR)
   • 6. Test API Access Controls
   • 7. Session Fixation and Management
   • 8. Vertical and Horizontal Privilege Escalation
   • 9. Forced Browsing
   • 10. Cross-Origin Resource Sharing (CORS) Misconfigurations
   • 11. Testing Multi-Factor Authentication (MFA) Bypass
   • 12. Advanced Access Control Testing Scenarios
   • 13. Authentication and Authorization Testing
   • 14. Security Misconfigurations Affecting Access Control
   • 15. Access Control in Microservices and Serverless Architectures
   • 16. Security in Cloud Environments
   • 17. Insider Threat Scenarios
   • 18. Access Control Testing in Mobile and IoT Environments
   • 19. Best Practices and Recommendations
   • 20. Considerations for Testing Environments
6. Tools and Techniques
7. Reporting
8. Remediation Recommendations
9. Conclusion

Introduction

Broken access control is a common vulnerability in web applications where users can access resources or perform actions that they should not be able to. This workflow will help you identify and mitigate these vulnerabilities through systematic testing.

Pre-requisites

Before you begin, ensure you have the following:

• Access to the target web application.
• An understanding of the application's user roles and permissions.
• Tools for testing, such as a web proxy (e.g., Burp Suite, OWASP ZAP).
• A test plan outlining the user roles and actions to be tested.

Understanding Access Control

Access control ensures that users can only perform actions and access data that their role allows. There are several types of access control mechanisms, including:

• Role-Based Access Control (RBAC): Access is granted based on user roles.
• Discretionary Access Control (DAC): Access is granted based on rules defined by users.
• Mandatory Access Control (MAC): Access is based on regulated policies.
• Attribute-Based Access Control (ABAC): Access is granted based on attributes (e.g., user, resource, environment).

Types of Broken Access Control Vulnerabilities

Broken access control can manifest in several ways:

• Unrestricted URL Access: Accessing URLs or API endpoints that should be restricted.
• Insecure Direct Object References (IDOR): Accessing or manipulating objects that should be restricted.
• Privilege Escalation: Gaining unauthorized access to higher-privilege functionality.
• Forced Browsing: Accessing parts of the application not intended for certain users.
• Parameter Tampering: Modifying request parameters to perform unauthorized actions.
• CORS Misconfigurations: Accessing resources cross-origin without proper authorization.
• Session Fixation: Reusing or setting session identifiers to impersonate users.
• MFA Bypass: Bypassing multi-factor authentication mechanisms.

Testing Workflow

1. Identify Entry Points

• List all entry points for the web application, including pages, endpoints, and APIs.
• Identify publicly accessible pages versus those requiring authentication.
• Check for hidden or less-obvious entry points like administrative interfaces, old endpoints, or staging environments.

To enumerate pages, use tools like Gobuster or Dirb with a suitable wordlist to identify potential access points.

2. Check for Unauthenticated Access

• Attempt to access restricted pages without logging in.
• Verify if unauthenticated users can access sensitive data or functionalities.
• Test different HTTP methods (GET, POST, PUT, DELETE) to see if they allow unauthorized actions.

Use web proxies or manual inspection to identify any resources that may be inadvertently exposed to unauthenticated users.

3. Test for Role-Based Access Control (RBAC)

• Login with different user roles (e.g., Admin, User, Guest).
• Try to access functionalities outside the user's assigned role.
• Ensure that each role has appropriate access and restrictions.
• Check for improper role validation in the backend.

Intercept and modify HTTP requests to change user roles and test access to functionalities not allowed for the logged-in role.

4. Bypass Business Logic Controls

• Test for flaws in the application's business logic that could allow privilege escalation or unauthorized actions.
• Check if a regular user can change their role to an admin by modifying request parameters or headers.
• Test for improper state transitions where actions should be restricted based on user role or context but are not.

Modify HTTP requests to attempt changing roles or perform unauthorized actions by altering parameters or headers.

5. Test URL Manipulation and Insecure Direct Object References (IDOR)

• Attempt to access restricted resources by directly manipulating URLs.
• Change URL parameters to access another user's data or resources.
• Test if predictable URL patterns allow for IDOR vulnerabilities.
• Verify if unauthorized users can enumerate resources through URL manipulation.

Check if changing URL parameters, like IDs, allows access to other users' profiles or data.

6. Test API Access Controls

• Ensure that APIs enforce access control consistently with the web application's front-end.
• Test authenticated and unauthenticated API endpoints for unauthorized access.
• Check if sensitive endpoints are exposed or lack proper authentication checks.
• Test for excessive data exposure where the API returns more data than necessary.

Send API requests using tools like Postman or curl, with or without proper authorization tokens, to verify access controls.

7. Session Fixation and Management

• Test for session fixation issues where an attacker can set or reuse a session ID.
• Verify that sessions are properly invalidated upon logout or password change.
• Test for session expiration issues to ensure that sessions are appropriately terminated after inactivity or timeout.
• Ensure secure cookie attributes are set (e.g., HttpOnly, Secure, SameSite).

Test session management by manually setting session cookies or tokens and checking if they persist or get invalidated appropriately.

8. Vertical and Horizontal Privilege Escalation

• Vertical Privilege Escalation: Test if a user can gain access to functions reserved for higher-privileged roles.
• Horizontal Privilege Escalation: Test if a user can access or modify data of another user with the same level of privilege.

Attempt to use lower-privileged accounts to access or modify data or functionalities of higher-privileged accounts or peers.

9. Forced Browsing

• Attempt to access hidden or unlinked pages that may not be properly protected.
• Use automated tools to crawl and discover pages that may not be linked in the application but are accessible.

Check if unprotected resources can be accessed directly without authorization.

10. Cross-Origin Resource Sharing (CORS) Misconfigurations

• Test for misconfigured CORS policies that may allow unauthorized cross-origin access.
• Ensure that sensitive endpoints do not allow wildcard (*) origins unless absolutely necessary.
• Check if CORS policies correctly enforce allowed methods and headers.

Attempt to make cross-origin requests to sensitive endpoints and observe if they are accepted without proper validation.

11. Testing Multi-Factor Authentication (MFA) Bypass

• Attempt to bypass MFA mechanisms using known techniques like brute-forcing, phishing, or exploiting logic flaws.
• Verify if MFA can be bypassed by resetting factors (e.g., email, SMS) without proper validation.

Check if MFA implementation has weaknesses that can be exploited to gain unauthorized access.

12. Advanced Access Control Testing Scenarios (Continued)

• Referer and Origin-Based Access Controls: Check if the application relies on HTTP Referer or Origin headers for access control. Test if these headers can be manipulated to bypass controls.
• Time-Based Access Controls: Test if access is restricted based on time constraints, such as allowing access only during certain hours or days. Attempt to access resources outside of the permitted time window.
• Geolocation-Based Access Controls: Test if access is restricted based on geolocation. Use VPNs or proxies to attempt accessing the application from different locations and see if the access controls are properly enforced.
• Rate Limiting and Brute Force Protections: Check if there are mechanisms to limit the number of login attempts or API requests to prevent brute force attacks. Test these mechanisms to ensure they are effective.
• Access Control Policy Changes: Verify if changes to access control policies are immediately enforced across the application. Test scenarios where policies are updated and ensure that the new policies are correctly applied.

13. Authentication and Authorization Testing

• OAuth and OpenID Connect Testing: Test the OAuth and OpenID Connect implementations for potential vulnerabilities, such as improper scope handling, token leakage, or insecure redirect URIs.
• JWT (JSON Web Token) Misconfigurations: Test JWTs for weak signing algorithms, improper token expiration settings, or lack of claims validation. Verify that tokens cannot be tampered with or replayed.
• SAML (Security Assertion Markup Language) Attacks: Test for vulnerabilities in SAML implementations, such as XML signature wrapping, replay attacks, or incorrect attribute handling.

14. Security Misconfigurations Affecting Access Control

• Default Configurations and Credentials: Check for default configurations or credentials that have not been changed. Ensure that default settings are not exposing sensitive functionality.
• Error Messages and Debug Information: Test if verbose error messages or debug information reveal details about the access control logic or other sensitive information.

15. Access Control in Microservices and Serverless Architectures

• Service-to-Service Authentication and Authorization: Test how microservices authenticate and authorize requests from other services. Ensure that service-to-service communication is properly secured.
• Serverless Function Access Controls: Verify that serverless functions (e.g., AWS Lambda, Azure Functions) enforce appropriate access controls and do not expose sensitive operations.

16. Security in Cloud Environments

• Cloud-Specific Access Controls: Test for proper implementation of cloud-native access control mechanisms, such as IAM roles and policies in AWS, Azure, and GCP. Ensure that least privilege principles are applied.
• Access Control Misconfigurations in Containers and Orchestrators: Check access controls in containerized environments (e.g., Kubernetes). Ensure that sensitive operations are not exposed due to misconfigurations.

17. Insider Threat Scenarios

• Testing for Insider Attacks: Simulate scenarios where users with legitimate access attempt to escalate privileges or access unauthorized data. Ensure that proper controls are in place to detect and prevent such actions.
• Data Leakage through Misconfigured Permissions: Verify that data access controls are correctly implemented to prevent data leakage. Ensure that users cannot access data beyond their intended permissions.

18. Access Control Testing in Mobile and IoT Environments

• Mobile Application Access Controls: Test access controls in mobile applications. Use mobile proxies, debuggers, and reverse engineering tools to identify potential vulnerabilities.
• IoT Device Access Controls: Test access control mechanisms on IoT devices. Check for hardcoded credentials, weak network communication protocols, and unauthorized access to device functionalities.

19. Best Practices and Recommendations

• Implement Context-Aware Access Controls: Use access controls that consider multiple factors such as user behavior, device, and network conditions.
• Regularly Update and Patch Software: Ensure all components, libraries, and dependencies are up-to-date to fix known vulnerabilities.
• Use Security Headers and Response Headers: Implement headers like Content-Security-Policy (CSP), X-Content-Type-Options, and X-Frame-Options to enhance security.
• Continuous Monitoring and Logging: Implement comprehensive logging and monitoring of all access attempts to detect and respond to potential violations in real-time.
• User Education and Awareness: Educate users and administrators about secure access practices and recognizing social engineering attempts.

20. Considerations for Testing Environments

• Test in Staging Environments: Conduct tests in staging or test environments that replicate production to avoid impacting live users.
• Use Safe Testing Techniques: Use non-disruptive methods, especially in environments resembling production, to prevent service disruptions or data loss.

Tools and Techniques

• Burp Suite: For intercepting and modifying HTTP requests.
• OWASP ZAP: An open-source tool for finding vulnerabilities in web applications.
• Postman: For API testing.
• Fiddler: A free web debugging proxy tool.
• Gobuster/Dirb: For directory and file enumeration.
• Nmap: For network discovery and vulnerability scanning.
• Custom Scripts: Use Python, Bash, or other scripting languages for automated testing.
• JWT.io: For decoding and testing JSON Web Tokens (JWTs).
• NoSQLMap: For testing NoSQL databases for access control weaknesses.

Reporting

• Document all findings with detailed descriptions, steps to reproduce, and evidence such as screenshots or request/response logs.
• Include severity ratings and potential impacts of each vulnerability.
• Use a structured format like the OWASP Risk Rating Methodology to evaluate the risk.
• Provide detailed recommendations for each finding, focusing on how to fix the vulnerabilities.