Application security with PyJWT and FastAPI

Introduction

#fastapi is a modern, fast, web framework for building #apis with Python 3.6+ based on standard #python type hints. One of the most critical aspects of building secure APIs is authentication and authorization. In this article, we will explore how to use PyJWT in FastAPI to authenticate and authorize users.

What is PyJWT?

PyJWT is a Python library that allows you to encode and decode JSON Web Tokens (JWTs). JWTs are a secure way to transmit data between parties, and they are commonly used for authentication and authorization. A JWT consists of three parts: the header, the payload, and the signature. The header contains metadata about the token, such as the type of token and the algorithm used to sign the token. The payload contains the data that you want to transmit, such as user information. Finally, the signature is a hash of the header, payload, and a secret key.

Installing PyJWT

The first step is to install the PyJWT library. You can do this using pip, the package manager for Python: pip install pyjwt

Creating a JWT

To create a JWT, you need to import the PyJWT library and define a payload dictionary that contains the data you want to transmit. For example, let's say we want to transmit the user's username and email address:

In the above code, we import the PyJWT library and define a payload dictionary containing the user's username and email address. We then call the jwt.encode() function to create the JWT, passing in the payload dictionary, a secret key, and the signing algorithm. In this case, we are using the HS256 algorithm, which is a symmetric algorithm that uses a secret key to sign and verify the token. The result is a long string of encoded data that can now be transmitted.

Verifying a JWT

Once a JWT has been created, it can be transmitted to the client. When the client makes a subsequent request, the JWT should be included in the request headers. To verify the JWT in FastAPI, we can create a function that extracts the token from the request headers, decodes the token, and returns the payload.

In the above code, we define a dependency called verify_token that extracts the JWT from the request headers using the HTTPBearer security scheme. We then call the jwt.decode() function to decode the JWT, passing in the token, the secret key, and the list of allowed algorithms. If the JWT is valid, the function returns the payload, which can be used to authenticate and authorize the user. If the JWT is invalid or has expired, the function raises an HTTPException with a status code of 401 (Unauthorized).

Now can create an endpoint for clients to call on the verify_token for verification

The complete code looks like this:

Final Notes

The app = FastAPI() all the uvicorn server to run the myapp.py file as the main file in our application. To run our application, we enter uvicorn myapp:app --reload.

The reload flag let's uvicorn refresh refresh our webpage automatically without having to restart the server. Finally, navigate to 127.0.0.1:8080/ in your browser to view the result.

Conclusion

In this article, we explored how to use PyJWT in FastAPI to authenticate and authorize users. PyJWT is a powerful library that allows developers to create secure and efficient APIs by leveraging the power of JSON Web Tokens. By using PyJWT in FastAPI, developers can create a robust authentication and authorization system that ensures only authorized users can access protected resources.

PyJWT supports a variety of algorithms for signing and verifying JWTs, including symmetric algorithms like HS256 and asymmetric algorithms like RS256. Developers can choose the algorithm that best suits their needs based on security requirements and performance considerations.

In conclusion, PyJWT and FastAPI are a powerful combination for creating secure and efficient APIs. By leveraging the strengths of both libraries, developers can create a robust authentication and authorization system that ensures only authorized users can access protected resources.