O que é JWT? Aprenda tudo sobre JSON Web Token

Introduction

This tutorial will help you understand JSON Web Tokens (JWT), a crucial mechanism for authorization in web applications. We will break down the JWT flow, its purpose, and how to effectively implement it in your projects.

Step 1: Understanding JWT

• JWT stands for JSON Web Token, which is used for communication between two parties in a secure manner.
• JWT is often confused with authentication; however, it is primarily used for authorization after a user has been authenticated.
• Authorization allows users to access specific resources based on their authentication status.

Step 2: The JWT Authorization Flow

The flow of using JWT is straightforward and consists of the following steps:

1. User Authentication: The user logs into the system or API by providing credentials (email/username and password).
2. Token Generation: Upon successful authentication, the server generates a JSON Web Token and sends it to the user.
3. Token Storage: The user should save the token, typically in localStorage using JavaScript.
4. Sending Token with Requests: For every subsequent request to the server, the token must be included.
5. Token Validation: The server decodes and validates the token. If valid, the user is granted access to the requested resources.

Step 3: Implementing JWT

• Login Process:

  • Create a login form to collect user credentials.
  • On form submission, authenticate the user and issue a JWT.

• Storing the Token:

  localStorage.setItem('jwt', token);
  

• Using the Token:

  • For API requests, include the token in the headers:

  fetch('https://api.example.com/protected', {
      method: 'GET',
      headers: {
          'Authorization': `Bearer ${localStorage.getItem('jwt')}`
      }
  });
  

Step 4: Token Validation on the Server

• On the server side, decode the JWT to verify its validity:

  const jwt = require('jsonwebtoken');
  
  const token = req.headers['authorization'].split(' ')[1];
  
  jwt.verify(token, 'your_secret_key', (err, decoded) => {
      if (err) {
          return res.status(403).send('Unauthorized');
      }
      // Proceed with the request
  });
  

Conclusion

In summary, JWT is an essential tool for handling authorization in web applications. By following the steps outlined, you can implement JWT effectively to manage user access securely. Next steps include reading more about JWT specifications or exploring more advanced security measures such as token expiration and refresh tokens.