Authentication and authorization in web applications can be achieved in various ways, and one of the most frequently utilized methods is the use of JSON Web Tokens (JWTs). JWT is a compact, URL-safe means of representing claims securely between two parties.
Here is a simple way to implement JWT authorization and authentication for a web application:
1. Set up necessary packages:
In order to use JWT for user authentication, you’ll need to use some libraries. In the case of a Node.js application, you would need to install the jsonwebtoken and bcryptjs libraries.
Install them with:
```
npm install jsonwebtoken bcryptjs
```
1. User Registration:
When a user registers with your application, you’ll need to store some information about the user, such as username and password, in the database. The password must be hashed before you store it.
Example in Node.js:
```
const bcrypt = require(‘bcryptjs’);
let hashedPassword = bcrypt.hashSync(userPassword, 8);
```
1. User Login:
When a user tries to login, fetch the password for the supplied username from database. Hash the supplied password and check if it matches the hashed password in database. If the match is successful, this means that the password is correct.
Example in Node.js:
```
let passwordIsValid = bcrypt.compareSync(userPassword, passwordFromDatabase);
if (!passwordIsValid) return res.status(401).send({ auth: false, token: null });
```
1. Generation of JWT:
If the user is successfully authenticated, you will generate a JWT for the user. You would need to choose a secret key for signing the token.
Example in Node.js:
```
var jwt = require(‘jsonwebtoken’);
var token = jwt.sign({ id: userId }, mySecretKey, {expiresIn: 86400}); // Expires in 24 hours
```
1. Respond with JWT
After generating the token, include it in the response.
1. Client side:
Save the token at the client side, and include it in header for every subsequent request that requires authentication.
1. Securing Endpoints:
For certain routes, you would want to check if the user is authenticated. You would do that checking if there is a token in the header of the request, and checking the signature of the token.
Example in Node.js:
```
var token = req.headers[‘x-access-token’];
if (!token) return res.status(401).send({ auth: false, message: ‘No token provided.’ });
Remember that JWT doesn’t encrypt data, so don’t put sensitive information in it. It only signs the data with a secret, so that it cannot be tampered with by others.
Also remember to keep your signing secret a secret and rotate it.
