Broken Access Control
Broken access control is when an application fails to properly restrict what users can do and access within the system. You see, when we use an app or a website, we expect that we’ll only be able to see and interact with the parts of the system we’re authorized for. If you’re just a regular user, you shouldn’t be able to access admin features or someone else’s private data, right? Well, that’s where broken access control comes in. When it’s not working as it should, users can end up with access to resources and functions they really shouldn’t have.
Now, you might be thinking, “Okay, but how common is this issue?” Turns out, it’s actually quite prevalent in modern applications. In fact, the Open Web Application Security Project (OWASP) lists broken access control as one of the top security risks in their widely-used OWASP Top 10 list. This means that a lot of applications out there – maybe even some of your favorites – could have this vulnerability lurking in the shadows, just waiting to be exploited.
Understanding Broken Access Control
Access control has two main components: authentication and authorization. Authentication is all about verifying who you are, like when you enter your username and password to log in. Once you’re authenticated, the system moves on to authorization, which determines what you can and can’t do based on your access level. For example, a regular user might be allowed to view their own account details, but an admin could have the power to view and manage all user accounts. So, how does access control get broken? There are a few key causes:
- Insecure configurations: Sometimes, developers leave default settings or configurations that aren’t secure, or they might even disable security features during development and forget to turn them back on. This can leave the application wide open to attackers.
- Insufficient user access management: If an application doesn’t have a robust system in place to manage user access levels and permissions, it’s all too easy for users to end up with more access than they should have.
- Flawed implementation of access control mechanisms: Even with good intentions, developers can make mistakes when implementing access control. They might use weak or broken algorithms, skip important security checks, or simply misunderstand how to properly implement access controls.
Now that we know how access control can break, let’s look at some specific examples of broken access control vulnerabilities:
- Insecure direct object references (IDOR): This happens when an attacker can access an object (like a file or a database record) simply by changing a URL or parameter value. For example, if you can view someone else’s profile just by changing the user ID in the URL (like incrementing from /1 to /2), that’s IDOR in action.
- Missing function-level access control: This occurs when the application doesn’t properly check if a user has permission to access a specific function, like deleting a post or changing account settings. Attackers can exploit this by directly accessing the unprotected function, bypassing the intended access restrictions.
- Privilege escalation: This is when a user gains elevated access levels they shouldn’t have, like going from a regular user to an admin. This can happen due to misconfigurations, bugs, or weak security measures, allowing attackers to wreak havoc in a system with their newfound powers.
Identifying Broken Access Control Vulnerabilities
First off, we have three main security testing tools that can help us uncover broken access control vulnerabilities:
- Static application security testing (SAST): This is like having a super-smart proofreader go through your code and point out potential security issues before your application is even up and running. SAST tools scan your source code, looking for patterns and weaknesses that could lead to vulnerabilities like broken access control. A popular example now days is Snyk.
- Dynamic application security testing (DAST): Think of this as a hands-on approach to finding vulnerabilities. DAST tools interact with your running application, testing it from the outside to identify any issues. Burp Suite Pro, Invicti and OWASP ZAP are good examples.
- Interactive application security testing (IAST): This method combines the best of both worlds. IAST tools work alongside your application as it runs, monitoring both the code and the app’s behavior. This gives you real-time feedback and helps you pinpoint the exact location of any broken access control vulnerabilities.
Another way to identify these types of vulnerabilities are:
- Penetration testing: Penetration testing involves having a skilled security expert (or team of experts) try to break into your application, just like a real attacker would. This can be an effective way to identify broken access control issues, as well as other vulnerabilities that automated tools might miss.
- Manual code reviews: Don’t underestimate the power of good old-fashioned human intuition! Having experienced developers or Application Security Engineers review code can help identify potential broken access control vulnerabilities that automated tools might overlook.
- Bug bounty: Having a bug bounty program can also help with identification, however you wouldn’t want to rely only on this.
Mitigating and Preventing Broken Access Control Vulnerabilities
Secure development practices:
- Security training for developers: First and foremost, it’s essential to make sure your developers are up to speed on the latest security best practices. Regular training sessions and workshops can help ensure that everyone on your team knows how to build secure applications from the ground up.
- Integrating security into the software development lifecycle (SDLC): Don’t wait until the end of the development process to start thinking about security. Instead, make it an integral part of every stage, from planning to deployment. This proactive approach can help you catch vulnerabilities like broken access control early on, saving you time and headaches down the line.
Implementation of robust access control mechanisms:
- Role-based access control (RBAC): One effective way to manage user permissions is by using roles. With RBAC, you define a set of roles (e.g., admin, user, guest) and assign specific access levels and privileges to each role. This makes it easier to manage and maintain access control across your application.
- Attribute-based access control (ABAC): ABAC takes access control a step further by considering additional user attributes, such as location, time, or device. This dynamic approach can help you create even more granular and fine-tuned access policies.
- Mandatory access control (MAC): In a MAC system, access control policies are strictly enforced, and users cannot override them. This can be useful in high-security environments where you need to minimize the risk of unauthorized access.
Incident response planning:
Despite your best efforts, there’s always a chance that a security incident could occur. Having a solid incident response plan in place can help you minimize the damage and recover more quickly if your application does fall victim to a broken access control attack or another security breach.
Well, we’ve reached the end of our deep dive into broken access control. We’ve covered a lot of ground, from understanding what it is and how it happens to learning how to prevent and mitigate these vulnerabilities. As we’ve seen, broken access control is a prevalent issue in modern applications and can have significant consequences for both users and organizations.
About the Author:
Application Security Engineer and Red-Teamer. Over 15 years of experience in Application Security, Software Engineering and Offensive Security. OSCE3 & OSCP Certified. CTF nerd.