Secure Your Applications with Flask and JWT Authentication

So, you're developing an API with Flask and you'd like to add some authentication. You need a way to securely store user credentials and generate tokens for valid users who sign in to your application. JWT (JSON Web Token) authentication is becoming increasingly popular, especially with developers building single page applications and mobile applications that use APIs. This tutorial will show you how to use Flask and the Flask-JWT extension to add JWT authentication to your application.

What is JWT?

JWT stands for JSON Web Token and it's an open standard (RFC 7519) for creating and sharing information securely between parties. A JWT consists of three parts: a header, a payload, and a signature. The header and payload are base64 encoded and combined separated by a period. They contain information such as the algorithm used to generate the token and data about the user or application. The signature is then generated using the header and payload along with a secret key.

How does JWT Work?

When a user authenticates to an application, the application will generate a JWT for the user. The token contains data about the user, as well as a signature that is generated using the secret key. When the user accesses an endpoint that requires authentication, they will pass the token to the server. The server will then validate the token and make sure it was not tampered with, and if it is valid, it will allow the user to access the desired endpoint.

Prerequisites

Before we dive into creating our application, there are a few things that we need to have installed and setup.

• Python 3.6+
• Flask
• Flask-JWT
• PyJWT
• Optional - Postman for testing endpoints

Creating the Application

Now that we have all of the prerequisites installed, let's create our application. We'll start by creating a directory for our project, and then creating a virtual environment. Virtual environments help keep our project dependencies and code separate from other projects on our system. Next, let's install the required packages. We'll use pip to install Flask, Flask-JWT and PyJWT. Now that we have everything installed, let's create our application. We'll start by creating a file named app.py, which will contain our Flask application code.

Configuration

Before we start writing code, let's make sure that our application is properly configured. First, we'll add some configuration options to our application. We need to set a secret key and enable debug mode so that our application will work properly. Next, let's set up our JWT configuration. First, we need to set the algorithm that will be used to sign our tokens. Then, we'll set the expiration time for the tokens. This is how long the token will be valid for before it needs to be renewed.

Creating the Routes

Now that our application is configured, let's create some routes that will be used for authentication. First, we'll create a route that will generate the JWT token when a user successfully logs in. For this example, we'll assume that the user has already been authenticated against a separate database.

• @app.route('/login', methods=['POST'])
• def login():
• # Create the JWT token
• token = jwt.encode({'user': user.name}, app.config['SECRET_KEY'])
• return jsonify({'token': token.decode('UTF-8')})

Next, we'll create a route that will be used to protect any endpoints that require authentication. This route will check that the user has a valid JWT token before allowing them to access the endpoint.

• @app.route('/protected', methods=['POST'])
• @jwt_required
• def protected():
• return jsonify({'message': 'You are authenticated!'})

Testing the Application

To verify that our application is working as expected, let’s create a few test cases. We’ll use Postman to make sure that our application responds correctly when valid and invalid tokens are provided. First, let’s try accessing the protected endpoint without providing a token. We should expect that the application returns an HTTP 401 Unauthorized status code. Next, let’s provide a valid token and make sure that the endpoint returns an HTTP 200 OK status code along with the message “You are authenticated!” Finally, let’s provide an invalid token and verify that the application still returns an HTTP 401 Unauthorized status code.

Conclusion

In this tutorial, we learned how to add JWT authentication to a Flask application using the Flask-JWT extension. We created a few routes, configured our application, and tested the endpoints with Postman. Adding JWT authentication to your application is a great way to add a secure layer of authentication to your application. With JWT authentication, you can rest easy knowing your application and its data are secure.