What is Broken Object Level Authorisation (BOLA) And How to Fix It?

Web apps and APIs (application programming interfaces), have emerged as the two most important parts of modern software systems. While these technologies offer unprecedented convenience and functionality, they also introduce new security challenges. 

Among these, Broken Object Level Authorisation, commonly known as BOLA, stands out as a critical vulnerability that demands our attention.

What is Broken Object Level Authorisation (BOLA)?

Broken Object Level Authorisation is a security flaw that happens when an application fails to properly verify a user's permission to access or modify specific data objects. To put it simply, BOLA is like having a key that not only opens your own locker but accidentally grants access to everyone else's lockers too!

BOLA vulnerabilities arise when an application uses object IDs (unique identifiers for pieces of data) without adequately verifying if the user requesting the data should have access to it. This oversight can lead to unauthorised users viewing, modifying, or deleting information they shouldn't be able to touch.

How Does BOLA Work?

To truly grasp what broken object level authorisation is, it's essential to understand how it operates within an application:

• Object References: Applications often use unique identifiers (IDs) to reference specific data objects, such as user profiles, documents, or transactions.
• API Endpoints: These IDs are typically used in API endpoints to retrieve or manipulate data.
• Insufficient Checks: In a BOLA vulnerability, the application fails to verify if the authenticated user has the right to access the object specified by the ID.
• Unauthorised Access: This allows attackers to manipulate the object IDs in their requests to access data belonging to other users.

The Significance of BOLA in API Security

Broken Object Level Authorisation is not just another security buzzword. Its significance in API security cannot be overstated:

1. Top API Vulnerability: BOLA is ranked as the number one security risk for APIs by the OWASP in their API Security Top 10 list.
2. Widespread Impact: BOLA vulnerabilities can affect a vast number of users and their data, potentially compromising entire user databases.
3. Ease of Exploitation: Unlike some complex cyber attacks, exploiting a BOLA vulnerability often requires minimal technical skills. Attackers might only need to change a few numbers in a web address or API request.
4. Severe Consequences: BOLA attacks can lead to major data breaches, exposing sensitive personal or financial information, and causing significant damage to both users and organisations.

Also Read: What is the OWASP API Security Top 10?

Anatomy of a BOLA Attack

To better understand how a BOLA attack unfolds, let's walk through a typical scenario:

1. A user logs into an online service and receives a unique ID, say "user123".
2. The application uses this ID to fetch the user's data, such as their profile information, through an API endpoint like /api/users/user123/profile.
3. A potential attacker notices that changing the ID in the API request from "user123" to "user124" reveals another user's data.
4. The attacker can now access, and potentially modify, other users' information simply by iterating through different ID values.

This scenario demonstrates the core of what broken object level authorisation is - the application isn't verifying if the logged-in user should have permission to access data associated with other IDs.

The Devastating Impact of BOLA Attacks

When a BOLA attack occurs, its repercussions can be far-reaching and severe:

• Unauthorised Data Access: Attackers can view sensitive information belonging to other users, compromising privacy on a large scale.
• Data Manipulation: Hackers might alter or delete data they shouldn't have access to, potentially causing chaos in systems that rely on data integrity.
• Privacy Violations: Personal information can be exposed, leading to any form of cybercrime.
• Compliance Issues: Companies might face legal problems and hefty fines for not adequately protecting user data, especially in regulated industries.
• Reputation Damage: Organisations can suffer severe reputational harm if their systems are compromised, leading to loss of customer trust and potential business impacts.
• Financial Losses: Both direct costs (like fines and legal fees) and indirect costs (like lost business) can result from a BOLA attack.

Comprehensive Strategies to Prevent BOLA Attacks

Protecting against Broken Object Level Authorisation requires a multi-faceted approach. Here are detailed strategies to safeguard your APIs:

Implement Robust Authorisation Checks

The cornerstone of preventing BOLA attacks is implementing strong, consistent authorisation checks:

• Contextual Authorisation: Don't just check if a user is logged in. Verify that they have the right to access the specified resource they're requesting.
• Centralised Authorisation Logic: Implement authorisation checks in a central place to ensure consistency across all API endpoints.
• Use Authorisation Frameworks: Leverage established authorisation frameworks like OAuth 2.0 to manage access controls effectively.

Utilise Universally Unique Identifiers (UUIDs)

Replacing simple, sequential IDs with Universally Unique Identifiers (UUIDs) can significantly enhance security:

• Unpredictability: UUIDs are long, random strings that are virtually impossible for attackers to guess or enumerate.
• Example UUID: 550e8400-e29b-41d4-a716-446655440000
• Implementation: Use UUID libraries, which are available in most programming languages, to generate these identifiers.

Adopt the Principle of Least Privilege

Minimise potential damage by restricting access rights:

• Granular Permissions: Define fine-grained permissions for different types of data and operations.
• Regular Access Reviews: Periodically review and adjust user permissions to ensure they align with needs.
• Temporary Access: Implement time-bound access for sensitive operations or data.

Implement Comprehensive API Security Testing

Regular and thorough API security testing is crucial for identifying and addressing BOLA vulnerabilities:

• Automated Scanning: Use API security testing tools to regularly scan for common vulnerabilities, including BOLA.
• Manual Penetration Testing: Engage security experts to perform in-depth penetration testing of your APIs.
• Continuous Integration: Your CI/CD pipeline should include security checks to discover vulnerabilities early in development.
• Fuzz Testing: Employ fuzz testing techniques to identify unexpected behaviours in your API that could lead to BOLA vulnerabilities.

Implement Role-Based Access Control (RBAC)

RBAC provides a structured approach to managing permissions:

• Define Roles: Create roles that group related permissions together.
• Assign Users to Roles: Instead of assigning permissions directly to users, assign them to roles.
• Regular Role Reviews: Periodically review and update role definitions to ensure they remain appropriate.

Also Read: What is Role-Based Access Control (RBAC)?

Embrace the Zero Trust Security Model

Adopt a "never trust, always verify" approach:

• Continuous Verification: Verify every request, regardless of where it originates.
• Micro-Segmentation: To prevent breaches, divide your application into tiny, secure portions.
• Least-Privilege Access: Grant only the minimum permissions necessary for each operation.

Enhance Session Management

Proper session management is crucial in preventing unauthorised access:

• Secure Session Tokens: Use strong, cryptographically secure methods to generate session tokens.
• Short Session Lifetimes: Implement reasonably short session expiration times.
• Secure Token Storage: Ensure session tokens are stored securely on both the client and server sides.

Implement Thorough Input Validation

Validate all input to prevent manipulation of object IDs or other sensitive data:

• Server-Side Validation: Never rely solely on client-side validation. Always validate input on the server.
• Strict Type Checking: Ensure that input matches the expected data type (e.g., integers for numeric IDs).
• Sanitise Input: Remove or escape potentially harmful characters from user input.

Best Practices for Comprehensive API Security

To further fortify your APIs against BOLA and other vulnerabilities, consider these best practices:

• Regular API Updates: Keep your API infrastructure up-to-date with the latest security patches.
• Use HTTPS Everywhere: Encrypt all API traffic to avoid data loss and man-in-the-middle attacks.
• Implement Rate Limiting: Limit user requests per time period to prevent brute-force attacks and API misuse.
• Comprehensive Logging and Monitoring: Maintain detailed logs of API access and set up real-time monitoring to detect unusual patterns or potential attacks.
• Use Modern Authentication Protocols: Implement OAuth 2.0 or JSON Web Tokens (JWT) for secure API authentication and authorisation.
• API Versioning: Implement proper API versioning to manage changes and updates without breaking existing integrations.
• Error Handling: Implement proper error handling to avoid leaking sensitive information through error messages.

Also Read: What is API Authentication and Authorisation?

The Critical Role of Continuous API Security Testing

Continuous API security testing is paramount in the fight against BOLA and other API vulnerabilities:

1. Automated Security Scans: Utilise automated tools to frequently check your APIs for vulnerabilities, including BOLA.
2. Regular Penetration Testing: Engage cybersecurity experts to conduct thorough penetration testing of your API infrastructure.
3. Code Reviews with Security Focus: Implement mandatory security-focused code reviews as part of your development process.
4. Security in the SDLC: Integrate security checks at every stage of the Software Development Life Cycle (SDLC).
5. API Fuzzing: Employ API fuzzing techniques to uncover potential vulnerabilities by sending unexpected or random data to your API endpoints.
6. Continuous Monitoring: Install real-time monitoring and warning systems to promptly address security threats.

By making API security testing a continuous, integral part of your development and operations processes, you can significantly reduce the risk of BOLA and other security vulnerabilities.

Conclusion

Broken Object Level Authorisation (BOLA) remains one of the most critical and pervasive security vulnerabilities in the API landscape. As our dependence on APIs grows, so does the necessity of identifying and addressing BOLA issues.

At InstaSafe, we understand the critical importance of protecting against threats like Broken Object Level Authorisation (BOLA). Our Zero Trust Network Access (ZTNA) solution offers robust protection against BOLA and other API vulnerabilities by implementing continuous verification and least-privilege access controls.

Frequently Asked Questions (FAQs)

1. What is the difference between BOLA and Insecure Direct Object Reference (IDOR)?

BOLA is a broader category that includes IDOR. BOLA refers to any authorisation flaw allowing access to objects, while IDOR specifically involves manipulating object references to bypass authorisation.

2. What are the two main types of Broken Object Level Authorisation?

The two main types are:

1. Horizontal BOLA: Accessing objects of other users at the same privilege level.
2. Vertical BOLA: Accessing objects requiring higher privileges.
3. What is the root cause of BOLA?

The root cause of BOLA is inadequate or missing access control checks when a user requests access to an object, allowing unauthorised users to view or modify data.