Learn the fundamentals of JSON Web Tokens (JWT) and discover how to effectively implement them in your applications.
JSON Web Token (JWT) is a widely adopted standard for creating access tokens in applications. It provides a secure method for verifying user identities and ensuring the integrity of data exchanged between the client and server.
What is JWT and How Does it Work?
JWT operates by generating a token on the server, certifying the user’s identity, and sending this token to the client. The client then includes this token in subsequent requests to the server, allowing the server to identify and authenticate the user.
This architecture is especially beneficial for modern web applications that rely on API requests, whether to a REST or GraphQL API. Major companies like Google also utilize JWT for their APIs.
JWT tokens are cryptographically signed to ensure their authenticity. However, it’s essential to note that they are not encrypted. Storing user data in a JWT should only be done over an HTTPS connection to prevent unauthorized access.
Though JWTs have gained popularity, they are subject to criticism for being overused. It’s crucial to understand the advantages and limitations of JWT in comparison to other available options.
Use Cases of JWT
JWT primarily serves as a means of API authentication and server-to-server authorization. Its ability to securely authenticate users makes it an excellent choice in many scenarios.
Generating a JWT Token
In Node.js, you can generate a JWT token using the following code:
const header = { "alg": "HS256", "typ": "JWT" };
const encodedHeader = Buffer.from(JSON.stringify(header)).toString('base64');
This snippet sets the signing algorithm as “HMAC SHA256”. It then creates a buffer from the encoded JSON object and encodes it using base64.
Next, you can add a payload with customized data to the token using an object:
const payload = { username: 'Flavio' };
const encodedPayload = Buffer.from(JSON.stringify(payload)).toString('base64');
The payload object is also encoded using base64.
To ensure the integrity of the token, you can generate a signature from the header and payload content. Using the crypto module in Node.js, you can accomplish this:
const crypto = require('crypto');
const jwtSecret = 'secretKey';
const signature = crypto.createHmac('sha256', jwtSecret).update(encodedHeader + '.' + encodedPayload).digest('base64');
Here, a secret key, jwtSecret, is used to generate a base64-encoded representation of the encrypted signature.
To finalize the creation of a JWT token, concatenate the three parts (header, payload, and signature) with a dot:
const jwt = `${encodedHeader}.${encodedPayload}.${signature}`;
API Authentication
API authentication is one of the most practical ways to utilize JWT. In this scenario, a user signs up for a service and receives a JWT token from the service dashboard. This token is then used for authenticating subsequent requests to the server.
Another use case is when you manage an API, and clients connect to your service. You can require your users to pass the JWT token with every subsequent request.
To securely manage the token on the client-side, it is recommended to store it in an HttpOnly cookie. This approach mitigates the risk of XSS attacks and automatically sends the token to the origin server with each request.
Choosing the Right JWT Library
Numerous libraries exist for different programming languages and environments to handle JWT. For the best selection, you can refer to the jwt.io website.
Not Suitable for Session Tokens
It is essential to note that JWTs should not be used as session tokens. For session management, it is more efficient and secure to adopt a regular server-side session mechanism.
Additional Resources
To enhance your understanding of JSON Web Tokens, explore the following resources:
To delve further into the topic, consider reading the following articles: