Welcome back! In the previous lesson, we explored the fundamentals of secure password storage and authentication. We learned about the importance of hashing passwords using the bcryptjs library to ensure that user credentials are stored securely. Now, we will build on that foundation by introducing the concept of rate limiting, a crucial technique to enhance the security of your web applications.

Rate limiting is a strategy used to control the number of requests a user can make to a server within a specific time frame. This is particularly important for authentication endpoints, as it helps prevent brute force attacks where an attacker tries multiple password combinations to gain unauthorized access. By the end of this lesson, you'll be able to implement rate limiting in your authentication process to protect against such attacks.

Before we dive into rate limiting, let's quickly recap the initial setup of our Pastebin application. This will ensure that we are all on the same page. Here's a brief reminder of how we set up our Express application:

In this setup, we import the necessary modules, create an Express app, and configure session management. This forms the foundation upon which we will build our authentication and rate limiting logic.

Rate limiting is a technique used to control the number of requests a client can make to a server within a specified time period. It is a crucial security measure to prevent abuse and protect your application from attacks such as brute force attempts on login endpoints.

By limiting the number of login attempts, you can reduce the risk of unauthorized access. For example, you might allow a maximum of 5 login attempts within a 15-minute window. If a user exceeds this limit, they will be temporarily blocked from making further attempts.

To implement rate limiting in our application, we will use the express-rate-limit library. This library provides a simple way to set up rate limiting for your Express routes.

First, ensure that you have the library installed. If you're working on your own device, you can install it using npm:

In the CodeSignal environment, this library is pre-installed, so you don't need to worry about installation there.

Now, let's set up rate limiting for our login route:

Here, loginLimiter is a simple Express middleware—just like any other middleware you might use in your routes. It checks the number of requests and blocks further attempts if the limit is exceeded. There’s no magic involved; you simply attach it to your route to enforce rate limiting.

In this code, we set up a rate limiter using express-rate-limit. We define a 15-minute window during which a maximum of 5 login attempts is allowed. The rate limiting is enforced based on the client's IP address. If an IP address surpasses this limit, it will be temporarily restricted from making additional attempts. When the rate limit is breached, the server returns an HTTP status code of 429 (Too Many Requests), indicating that the user has exceeded the allowed number of requests in the specified time frame.

Now that we have set up rate limiting, let's integrate it into our existing authentication logic. Here's how you can modify the login route to include rate limiting:

In this updated login route, we apply the loginLimiter middleware to enforce rate limiting. The rest of the login logic remains the same, where we verify the user's credentials and establish a session upon successful login.

To ensure that rate limiting is functioning correctly, you can test it by simulating multiple login attempts. Try entering incorrect credentials more than 5 times within 15 minutes and observe the response. You should receive an error message indicating that there have been too many login attempts.

Testing rate limiting helps verify that your application is protected against brute force attacks and that legitimate users are not unfairly blocked.

In this lesson, we explored the concept of rate limiting and its importance in securing authentication endpoints. We learned how to implement rate limiting using the express-rate-limit library and integrated it into our existing authentication process. By doing so, we can protect our application from brute force attacks and ensure a more secure user experience.

As you move on to the practice exercises, remember to apply what you've learned about secure authentication and rate limiting. These skills are essential for building robust and secure web applications. Keep up the great work, and let's continue to enhance our security knowledge!