Stateless authorization using JWT in node.js made easy

2020-02-07

Using JWT for stateless authorization.

Introduction

Before diving deep let us first understand what authorization means? So basically authorization means giving someone permission to do or have something. Similarly in Web(or app) we authorize user to access private routes once logged in.

While authentication is simply verifying a user. Authentication is divided into two main type, Stateful and Stateless.

a. Stateful:- In Stateful authentication a session is created on server once authenticated, and after this user is authorized to access private routes until session exist.

b. Stateless:- In Stateless authentication no session is created but a token is generated and send it to the client(user) and when that client(user) wants to access private route he has to show that token, once verifying the token authorization is granted.

In Stateless authentication we generally use JWT or JSON Web Tokens.

Implementation

In this article we are going to create three simple routes as /register /login and a /secret route to implement authorization. /secret is going to be our private route.

We are going to implement this inside node application using express.

Step 0:- Dependencies Packages required are

• express:- for routing;
• jsonwebtoken:- for implementing tokens
• bcrypt:- for password hashing of password.

var express         = require("express"); 
var app             = express();
var jwt             = require("jsonwebtoken");

Step 1:- Register route In our registration route we have to perform 4 main operation as

• Generating salt for hashing.
• Hashing of password
• Creating a user
• Redirect route to /login.

app.post("/register",async function(req,res){
    //Salt generation through bcrypt
    const salt = await bcrypt.genSalt(10);

    //Hashing password 
    const hashedPassword =await bcrypt.hash(req.body.password,salt)

    //Creating user
    var user = new User({username:req.body.username, email:req.body.email, password:hashedPassword});
    user.save()

    //redirecting to /login route
    res.redirect("/")
});

Step 2:- Login route In our login route we have to perform 3 main operation as

• Finding user in your database using email(can use any other key too)
• Comparing password with hashed password
• Creating and sending token

app.post("/login",async function(req,res){
    //Finding user
    const user = await User.findOne({email:req.body.email});
    (!user){//if user does't exist
        return res.json('user not found')
    }

    //Comparing password
    const validPass =await bcrypt.compare(req.body.password,user.password)
    
    if(!validPass){
       return  res.json("Invalid password")
    }else{

        //Creating a token with user id 
        const token = jwt.sign({_id:user._id},process.env.TOKEN_SECRET);
        
        //sending token
        res.json({token});
    }
});

Format of jwt.sign() is jwt.sign(payload, secretOrPrivateKey, [options, callback]) Where

• payload is the data we want to send(in our case it is user._id),
• secretOrPrivateKey is a key for security of token we use during authorization
• optional options for token.

Step 3:- Secret route This route is our private route and we want to give access once the user is logged in. We make a route private by adding a express middleware to check whether a client is authorized to access that route or not, id user is authorized it will give access to the user else it will not. We are going to add a middleware function isLoggedIn.

app.get("/secret",isLoggedIn,function(req,res){
    //Secret route
    res.json({"msg":"inside secret route"});
});

Middleware

function isLoggedIn(req,res,next){
     //get token from header 
    const token = req.header('x-auth-token');

    // check if no token
    if(!token){
        return res.json({msg:"No token, authorization denied "});
    }

    // verify token
    try {
        const decoded = jwt.verify(token,process.env.TOKEN_SECRET);
        req.user = decoded.user;
        next();
    } catch (error) {
        res.json({msg:"token is not valid"});
    }
}

We are expecting a user to send token via x-auth-token header

Thats it for today's article.

In this article we have had a very quick look through the JWT JSON Web Token. Have a play with the code. We would like to grow our readership. Can you help us out by sharing this blog post?

Thank You.

Written by Kundan Chandel