Welcome to the third lesson of our "Broken Access Control" course! In this lesson, we will explore the concept of forced browsing, a technique used by attackers to exploit predictable URL patterns and gain unauthorized access to sensitive areas of a web application.

Uderstanding forced browsing is crucial for implementing effective access control mechanisms and protecting your applications from unauthorized access. Let's dive in and learn how to identify and mitigate these vulnerabilities. 🌟

Forced browsing occurs when attackers manipulate predictable URL patterns to access unauthorized pages within a web application. This vulnerability often arises when developers do not implement proper access control mechanisms, allowing attackers to bypass authentication and authorization checks. For example, if an application has predictable URLs like /admin/dashboard or /user/settings, an attacker might try accessing these URLs directly to gain unauthorized access.

Additionally, attackers often use automated tools like DirBuster, Gobuster, or Burp Suite's Content Discovery feature to systematically scan and discover unprotected endpoints. These tools work by testing thousands of common endpoint patterns against a target application, making it easier for attackers to find vulnerable administrative interfaces or sensitive resources that lack proper access controls.

With that being said, let's look at a code example to understand how this vulnerability might look like.

Let's examine a code snippet that demonstrates a vulnerable admin endpoint susceptible to forced browsing. This example highlights how the lack of access control can lead to unauthorized access to sensitive information.

In this code, the /admin/getAppInfo endpoint is exposed without any access control checks. This means anyone who knows the URL can access sensitive admin information, making it vulnerable to forced browsing attacks.

Next, we'll see how an attacker can exploit this vulnerability.

An attacker can easily exploit this vulnerability by sending a request to the vulnerable endpoint. Here's how it can be done using a simple command-line tool:

This command uses curl to send a request to the /getAppInfo endpoint. Since there are no access controls in place, the server responds with the sensitive admin information, demonstrating how easily an attacker can exploit this vulnerability.

To prevent such exploitation, we need to implement access control mechanisms.

To secure the endpoint, we need to implement role-based access control (RBAC). This ensures that only users with the appropriate role can access sensitive information. Remember, it's critical to enforce these checks on the server-side - hiding admin panels or disabling UI elements with JavaScript won't prevent attackers from making direct API requests.

This function checks the user's role and only allows access if the user is an admin. The security of this implementation relies on proper authentication:

1. When users log in, they receive a JWT token containing their userId
2. Before this middleware runs, the JWT token is verified and decoded
3. The decoded userId is stored in req.user, making it trusted data
4. We then use this trusted userId to look up the user's role

This ensures that users cannot manipulate their role or impersonate other users, as the userId comes from a verified JWT token, not from user input.

Now, let's apply the RBAC to the endpoint to ensure it is secure.

By implementing RBAC, we ensure that only authorized admin users can access the endpoint, significantly reducing the risk of forced browsing attacks.

With these measures in place, the endpoint is now secure against unauthorized access.

In this lesson, we explored the concept of forced browsing and learned how to secure endpoints using role-based access control. By understanding and mitigating these vulnerabilities, you can protect your web applications from unauthorized access.

Now, it's time to apply what you've learned in the practice exercises that follow. Keep up the great work, and continue exploring web application security in the upcoming lessons! 🚀