Adding Authentication to full stack MERN web application
This article is part 2 of "Let's build and deploy a full stack MERN web application". In that tutorial, we created an application called Productivity Tracker that allows you to log your daily activities. However, there is a problem with our app. Can you figure it out ๐? Your hint is in the title of this article. In this tutorial, let's see the problem and how to tackle it.
Let's get started
โ ๏ธ Warning: Authentication used in this tutorial is not secure. I don't recommend using this authentication method for real projects.
The Problem
Since your application is currently available online, anyone can use it and add activities to your database. That is not good, is it? Here, authentication steps in to save the day. To prevent unauthorized access to your app, add authentication.
Adding Authentication
We had to develop front-end and back-end authentication separately because we separated the two. Once more, for the sake of simplicity, we'll build basic authentication without the use of any libraries.
Backend authentication
We need to implement backend authentication and authorize some routes.
Authentication vs Authorization
These two words can be confusing to you. Authentication is allowing someone with credentials to access our application and Authorization is giving access to resources to authorized people.
In our scenario, authorization grants access to resources like creating activities and fetching activities whereas authentication entails logging into the application.
Introduction to JWT
JSON Web Token (JWT) is a compact URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted.
In simple terms, JWT is used is to verify that the user has permission to perform an action.
Let's implement login authentication with JWT.
Since you are the only person using your application you don't need a signup functionality and you can store EMAIL
and PASSWORD
in the .env
file.
- Open the
.env
file and add these three variables.
TOKEN_KEY=somesecrettoken EMAIL=youremail PASSWORD=yourpassword
Here TOKEN_KEY
can be any random string. It is used by JWT.
- Open up a terminal and install the
jsonwebtoken
package.
npm i jsonwebtoken
- Open
controllers
folder and createauth.controller.js
file. Copy and paste the below code.
1const jwt = require("jsonwebtoken"); 2 3require("dotenv").config(); 4 5const EMAIL = process.env.EMAIL; 6const PASSWORD = process.env.PASSWORD; 7 8/* If the email and password are correct, then return a token. */ 9const login = (req, res) => { 10 /* Destructuring the email and password from the request body. */ 11 const { email, password } = req.body; 12 13 if (email === EMAIL && password === PASSWORD) { 14 /* Creating a token. */ 15 const token = jwt.sign({ email }, process.env.TOKEN_KEY, { 16 expiresIn: "2h", 17 }); 18 return res.status(200).json({ 19 statusCode: 200, 20 msg: "Login successful", 21 token, 22 }); 23 } 24 return res.status(401).json({ 25 statusCode: 401, 26 msg: "Invalid Credentials", 27 }); 28}; 29 30module.exports = { 31 login, 32};
The code above checks to see if the email address and password match, and if they do, it generates a token and sends it to the front end to implement front-end authentication.
- Open the
routes
folder createauth.routes.js
and register a new route for login.
1const express = require("express"); 2 3const { login } = require("../controllers/auth.controller"); 4 5const router = express.Router(); 6 7router.post("/login", login); 8 9module.exports = router;
- Lastly, in
server.js
, use the registered route.
1... 2const AuthRouter = require("./routes/auth.route"); 3... 4 5... 6app.use("/api/auth", AuthRouter); 7...
We successfully implemented authentication. Now only authenticated people can access our application. But authenticated people can still access our resources and add activities because we haven't authorized those routes.
Let's create a middleware to authorize these routes.
GET /api/activities POST /api/activity
- In the project root, create a folder called
middleware
, and in that folder create theauth.js
file. Copy and paste the below code.
1const jwt = require("jsonwebtoken"); 2 3require("dotenv").config(); 4 5/* It checks if the token is valid and if it is, it decodes it and attaches the decoded token to the request object */ 6const verifyToken = (req, res, next) => { 7 const token = String(req.headers.authorization) 8 .replace(/^bearer|^jwt/i, "") 9 .replace(/^\s+|\s+$/gi, ""); 10 11 try { 12 if (!token) { 13 return res.status(403).json({ 14 statusCode: 403, 15 msg: "A token is required for authentication", 16 }); 17 } 18 /* Verifying the token. */ 19 const decoded = jwt.verify(token, process.env.TOKEN_KEY); 20 req.userData = decoded; 21 } catch (err) { 22 return res.status(401).json({ 23 statusCode: 401, 24 msg: "Invalid Token", 25 }); 26 } 27 return next(); 28}; 29 30module.exports = verifyToken;
We created a middleware function called verifyToken()
to verify the token sent by the front end through the header. If verification is successful then the user can access the above routes.
- Now open
activity.route.js
and modify the code like this.
1... 2router.get("/activities", auth, getActivities); 3 4router.post("/activity", auth, addActivity); 5...
That's it! Backend authentication is done ๐.
Frontend authentication
It's time to implement front-end authentication.
- First, let's create a login page.
- In
src
folder createLogin.jsx
andLogin.css
files. Copy and paste the below code inLogin.jsx
file and use this inLogin.css
.
1import React from "react"; 2 3import "./Login.css"; 4 5const Login = () => { 6 /* When the user submits the form, prevent the default action, grab the email and password from the form, send a POST request to the backend with the email and password, and if the response is successful, store the token in local storage and reload the page. */ 7 const handleSubmit = async (event) => { 8 event.preventDefault(); 9 const { email, password } = event.target; 10 11 const response = await fetch( 12 `${process.env.REACT_APP_BACKEND_URL}/auth/login`, 13 { 14 method: "POST", 15 headers: { 16 "Content-Type": "application/json", 17 }, 18 body: JSON.stringify({ 19 email: email.value, 20 password: password.value, 21 }), 22 } 23 ); 24 25 const data = await response.json(); 26 localStorage.setItem("token", data.token); 27 window.location.reload(); 28 }; 29 30 return ( 31 <div className="login"> 32 <h1>Login</h1> 33 <form onSubmit={handleSubmit}> 34 <span> 35 <label htmlFor="email">Email:</label> 36 <input type="email" id="email" name="email" /> 37 </span> 38 <span> 39 <label htmlFor="password">Password:</label> 40 <input type="password" id="password" name="password" /> 41 </span> 42 <button type="submit">Login</button> 43 </form> 44 </div> 45 ); 46}; 47 48export default Login;
This will render the login page.
The handleSubmit()
gets the email and password from the form, makes a POST
request, and sends email and password values for verification. After that server verifies and sends back a token that we can use to access resources.
Here we are using localStorage
to store the value in the browser permanently so that we won't get logged out after closing the application or browser.
- Open the
index.js
file and add this logic. If there is a token inlocalStorage
renderApp.jsx
otherwiseLogin.jsx
.
1... 2const token = localStorage?.getItem("token"); 3 4root.render( 5 <React.StrictMode> 6 {token ? <App /> : <Login />} 7 </React.StrictMode> 8); 9...
- Now in the
App.jsx
file, we need to sendtoken
through the header, so that backend will verify it and gives access to the routes.
1... 2useEffect(() => { 3 const fetchData = async () => { 4 const result = await fetch( 5 `${process.env.REACT_APP_BACKEND_URL}/activities`, 6 { 7 headers: { 8 Authorization: `Bearer ${token}`, // <----------- HERE 9 }, 10 } 11 ); 12 const data = await result.json(); 13 setActivities(data); 14 }; 15 fetchData(); 16}, [token]); 17... 18 19... 20const addActivity = async (event) => { 21 event.preventDefault(); 22 23 const newActivity = { 24 name: event.target.activity.value, 25 time: event.target.time.value, 26 }; 27 28 await fetch(`${process.env.REACT_APP_BACKEND_URL}/activity`, { 29 method: "POST", 30 headers: { 31 "Content-Type": "application/json", 32 Authorization: `Bearer ${token}`, // <---------- HERE 33 }, 34 body: JSON.stringify(newActivity), 35 }); 36 37 event.target.activity.value = ""; 38 event.target.time.value = ""; 39 window.location.reload(); 40}; 41...
Done โ ! We implemented both frontend and backend authentication. Now only you can access your application ๐ฅณ (as long as you don't share your credentials ๐).
Source code: productivity-app
In the next article, we will learn how to write tests for frontend and backend ๐.
Follow for more ๐ฏ.
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