JSON Web Tokens(JWT) For Authentication and Authorization in AWS
Tags: python, jwt, aws
Published: 2023-04-17 16:30:43

**JSON Web Tokens** (JWTs) are a compact type of access token that is used to securely transmit information between parties. In the context of authentication, a JWT can be used as a secure and stateless way to authenticate users and authorize access to resources. It can be verified locally by the client without the need to call the third-party service (such as an OAuth provider) every time the client wants to access a protected resource.

JWTs can be verified locally because they are self-contained and contain all the necessary information to verify their authenticity. A JWT consists of three parts: **a header, a payload, and a signature.**

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/4jeb0kygd7b33y3bad0v.png)

- _The header contains information about the type of token and the algorithm used to sign it._
-  _The payload contains the claims or assertions about the user or entity that the token represents._
-  _The signature is created by combining the header, payload, and a secret key that is only known to the server. The signature can be used to verify the authenticity of the JWT._

When a client sends a JWT to a server, the server can verify the authenticity of the token by decoding the token, checking the signature using the secret key, and verifying that the claims in the payload are valid. Since the secret key is only known to the server, this process ensures that only tokens issued by the server are accepted, and that the claims in the token have not been tampered with.

In contrast to OAuth, which relies on a centralized authorization server to manage access tokens, **JWTs can be verified locally without the need for a third-party service**. This makes JWTs a good option for applications that need to authenticate and authorize users without relying on external services.

**Here's how you can use JWTs for authentication and authorization:**

1. _The client (such as a web or mobile app) sends a request to your server with a username and password._
2. - _Your server authenticates the user and generates a JWT that includes the user's ID and any relevant permissions or roles._
3. - _Your server sends the JWT back to the client in the response._
4. - _The client stores the JWT (usually in local storage or a cookie) and sends it in the Authorization header of subsequent requests to your server_.
5. - _Your server verifies the JWT by checking the signature and decoding the claims (such as the user ID and permissions)._
6. - _If the JWT is valid, your server allows the request and returns the requested resource or performs the requested action._
7. - _If the JWT is invalid or expired, your server returns an error response._
_



## To use JWT (JSON Web Token) in AWS using Python, you can follow these steps:





**1.Create a JWT token using PyJWT:**

```
import jwt

def lambda_handler(event, context):
    # Generate a JWT with a payload containing the user's data
    token = jwt.encode({'username': 'johndoe', 'role': 'admin'}, 'my-secret-key', algorithm='HS256')

    return {
        'statusCode': 200,
        'body': token,
    }


```
In this example, the payload is a dictionary that includes the user ID and permissions. The secret key is a string that is used to sign the JWT. The jwt.encode() function encodes the payload and signs it with the secret key using the HS256 algorithm.

**2.- Verify the JWT in API Gateway:**
Make an API request to an AWS service (e.g., AWS Lambda) and include the JWT token in the request headers:

```
import requests

url = 'https://your-lambda-function-endpoint.amazonaws.com'
headers = {'Authorization': f'Bearer {token.decode()}'}

response = requests.get(url, headers=headers)

```

In the above example, we make an HTTP GET request to an AWS Lambda function using the requests library. We include the JWT token in the request headers using the Authorization field with the Bearer prefix.

Note that the token variable needs to be decoded to a string before it can be included in the headers.

That's it! You should now be able to use JWT in AWS using Python.