Application Using Express Server with JWT

Estimated Time Needed: 1 hour

Overview:

In the CRUD lab you performed CRUD operations on transient data by creating API endpoints with an Express Server. In this lab, you will restrict these operations to authenticated users using JWT and session authentication.

• In this lab, the friends object will be a JSON/dictionary with email as the key and friends object as the value. The friends object is a dictionary with firstName,lastName, DOB mapped to their respective values. You will thus be using “body” from the HTTP request instead of “query” and “params”.

• Only authenticated users will be able to perform all the CRUD operations.

• We will be testing the output of the endpoints on Postman.

Next

Set-up : Create application

1. Open a terminal window by using the menu in the editor: Terminal > New Terminal.

2. Change to your project folder, if you are not in the project folder already.

cd /home/project

3. Run the following command to clone the git repository that contains the starter code needed for this lab, if it does not already exist.

[ ! -d 'express-rest-boilerplate' ] && git clone https://github.com/CharlesDerek/express-rest-boilerplate.git

4. Change to the directory express-rest-boilerplate to start working on the lab.

cd express-rest-boilerplate

5. List the contents of this directory to see the artifacts for this lab.

ls

Requisite packages for a server application

1. The packages required for this lab are defined as dependencies in packages.json as below. You can view the file on the file explorer.

   "dependencies": {
      "express": "^4.18.1",
      "express-session": "^1.17.3",
      "jsonwebtoken": "^8.5.1",
      "nodemon": "^2.0.19"
  }

2. In the terminal run the following command to install all the packages.

npm install --save

This will install all the packages required for your server application to run.

Step 1: Understanding the User Authentication process

Let us understand the code in index.js.

1. Firstly, as the intent of this application is to provide access to the API endpoints only to the authenticated users, you need to provide a way to register the users. This endpoint will be a post request that accepts username and password through the body. The user doesn’t have to be authenticated to access this endpoint.

  `app.post("/register", (req,res) => {
    const username = req.body.username;
    const password = req.body.password;

    if (username && password) {
      if (!doesExist(username)) {
        users.push({"username":username,"password":password});
        return res.status(200).json({message: "User successfully registred. Now you can login"});
      } else {
        return res.status(404).json({message: "User already exists!"});
      }
    }
    return res.status(404).json({message: "Unable to register user."});
  });

2. You need to provide a manner in which it can be checked to see if the username exists in the list of registered users, to avoid duplications and keep the username unique. This is a utility function and not an endpoint.

  const doesExist = (username)=>{
    let userswithsamename = users.filter((user)=>{
      return user.username === username
    });
    if(userswithsamename.length > 0){
      return true;
    } else {
      return false;
    }
  }

3. You will next check if the username and password match what you have in the list of registered users. It returns a boolean depending on whether the credentials match or not. This is also a utility function and not an endpoint.

  const authenticatedUser = (username,password)=>{
    let validusers = users.filter((user)=>{
      return (user.username === username && user.password === password)
    });
    if(validusers.length > 0){
      return true;
    } else {
      return false;
    }
  }

4. You will now create and use a session object with user-defined secret, as a middleware to intercept the requests and ensure that the session is valid before processing the request.

app.use(session({secret:"fingerpint"},resave=true,saveUninitialized=true));

5. You will provide an endpoint for the registered users to login. This endpoint will do the following:

• Return an error if the username or password is not provided.

• Creates an access token that is valid for 1 hour (60 X 60 seconds) and logs the user in, if the credentials are correct.

• Throws an error, if the credentials are incorrect.

  app.post("/login", (req,res) => {
    const username = req.body.username;
    const password = req.body.password;

    if (!username || !password) {
        return res.status(404).json({message: "Error logging in"});
    }
   if (authenticatedUser(username,password)) {
      let accessToken = jwt.sign({
        data: password
      }, 'access', { expiresIn: 60 * 60 });

      req.session.authorization = {
        accessToken,username
    }
    return res.status(200).send("User successfully logged in");
    } else {
      return res.status(208).json({message: "Invalid Login. Check username and password"});
    }});

6. You will now ensure that all operations restricted to auhtenticated users are intercepted by the middleware. The following code ensures that all the endpoints starting with /friends go through the middleware. It retrieves the authorization details from the session and verifies it. If the token is validated, the user is aunteticated and the control is passed on to the next endpoint handler. If the token is invalid, the user is not authenticated and an error message is returned.

  app.use("/friends", function auth(req,res,next){
     if(req.session.authorization) {
         token = req.session.authorization['accessToken'];
         jwt.verify(token, "access",(err,user)=>{
             if(!err){
                 req.user = user;
                 next();
             }
             else{
                 return res.status(403).json({message: "User not authenticated"})
             }
          });
      } else {
          return res.status(403).json({message: "User not logged in"})
      }
  });

Example:

  const express = require('express');
  const jwt = require('jsonwebtoken');
  const session = require('express-session')
  const routes = require('./router/friends.js')

  let users = []

  const doesExist = (username)=>{
    let userswithsamename = users.filter((user)=>{
      return user.username === username
    });
    if(userswithsamename.length > 0){
      return true;
    } else {
      return false;
    }
  }

  const authenticatedUser = (username,password)=>{
    let validusers = users.filter((user)=>{
      return (user.username === username && user.password === password)
    });
    if(validusers.length > 0){
      return true;
    } else {
      return false;
    }
  }

  const app = express();

  app.use(express.json());

  app.use(session({secret:"fingerpint"}))

  app.use(express.json());

  app.use("/friends", function auth(req,res,next){
     if(req.session.authorization) {
         token = req.session.authorization['accessToken'];
         jwt.verify(token, "access",(err,user)=>{
             if(!err){
                 req.user = user;
                 next();
             }
             else{
                 return res.status(403).json({message: "User not authenticated"})
             }
          });
      } else {
          return res.status(403).json({message: "User not logged in"})
      }
  });

  app.post("/login", (req,res) => {
    const username = req.body.username;
    const password = req.body.password;

    if (!username || !password) {
        return res.status(404).json({message: "Error logging in"});
    }

    if (authenticatedUser(username,password)) {
      let accessToken = jwt.sign({
        data: password
      }, 'access', { expiresIn: 60 * 60 });

      req.session.authorization = {
        accessToken,username
    }
    return res.status(200).send("User successfully logged in");
    } else {
      return res.status(208).json({message: "Invalid Login. Check username and password"});
    }
  });

  app.post("/register", (req,res) => {
    const username = req.body.username;
    const password = req.body.password;

    if (username && password) {
      if (!doesExist(username)) { 
        users.push({"username":username,"password":password});
        return res.status(200).json({message: "User successfully registred. Now you can login"});
      } else {
        return res.status(404).json({message: "User already exists!"});    
      }
    } 
    return res.status(404).json({message: "Unable to register user."});
  });

  const PORT =5000;

  app.use("/friends", routes);

  app.listen(PORT,()=>console.log("Server is running"));

You have an express server that has been configured to run at port 5000. When you access the server with /friends, you can access the end points defined in routes/friends.js. But for doing this, you need to register as a new user in the /register endpoint and login with those credentials in the /login endpoint.

Note: You will now be implementing various CRUD operations for adding, editing and deleting friends by adding the necessary codes and further test the output on Postman.

Step 2: Implement the GET method:

Navigate to friends.js file under the directory router and you will observe that the endpoints defined in them have skeletal,where you have to implement the get method.

1. Write the code in router/friends.js file inside router.get("/",(req,res)=>{} in the space provided to get all the user information using JSON string.

  router.get("/",(req,res)=>{
      res.send(JSON.stringify(friends,null,4));

  });

Step 3: Implement the GET by specific email method:

1. Write the code inside router.get("/:email",(req,res)=>{} to view the user based on email but without using filter method.

router.get('/:email',function (req, res) {
const email = req.params.email;
res.send(friends[email])
});

Step 4: Implement the POST method:

1. Paste the below code inside router.post("/",(req,res)=>{} to add the new user to the JSON/dictionary.And also update the codes in the places mentioned.

  router.post("/",function (req,res){
      if (req.body.email){
          friends[req.body.email] = {
              "firstName":req.body.firstName,
              //Add similarly for lastName
              //Add similarly for DOB
              }
      }
  res.send("The user" + (' ')+ (req.body.firstName) + " Has been added!");
  });

Step 5: Implement the PUT method:

1. Paste the below code inside router.put("/:email", (req, res) => {} to modify the friend details.And also add the codes in the places mentioned.

  router.put("/:email", function (req, res) {
      const email = req.params.email;
      let friend = friends[email]
      if (friend) { //Check is friend exists
          let DOB = req.body.DOB;
          //Add similarly for firstName
          //Add similarly for lastName

          //if DOB the DOB has been changed, update the DOB 
          if(DOB) {
              friend["DOB"] = DOB
          }
          //Add similarly for firstName
          //Add similarly for lastName
          friends[email]=friend;
          res.send(Friend with the email  ${email} updated.);
      }
      else{
          res.send("Unable to find friend!");
      }
    });

Step 6: Implement the DELETE method:

1. Paste the below code inside router.delete("/:email", (req, res) => {} to delete the friend information based on the email.

    router.delete("/:email", (req, res) => {
      const email = req.params.email;
      if (email){
          delete friends[email]
      }
      res.send('Friend with the email  ${email} deleted.');
    });

Run the server to view the output

1. In the terminal, ensure that you are in the /home/projects/nodejs_PracticeProject_AuthUserMgmtdirectory.

2. Install all the packages that are required for running the server

npm install

3. Start the Express server.

npm start

Step 7: User registration, login & testing the endpoints using Postman:

Go to Postman and go to a new HTTP request window (as you did in Hands-on Lab - CRUD operations with Node.js)

User registration

1. Submit a POST request on the endpoint - 0.0.0.0:5000/register using the below JSON paramters in the ‘body’ of the request.

• Select ‘Body’ >> ‘raw’ >> ‘JSON’ and pass the parameters.

{"username":"user2", "password":"password2"}

Note: “user2” & “password2” are used for reference. You can use any username & password.

2. It should return the output as {"message": "User successfully registred. Now you can login"}.

User login

1. Submit a POST request on the endpoint - 0.0.0.0/login using the above username and password in the same JSON format in the ‘body’ of the request.

2. It should return the output as User successfully logged in.

Testing the endpoints on Postman:

1. Submit a GET request on the ‘friends’ endpoint - 0.0.0.0/friends and ensure that you see all the friends that have been added in the code.

2. Submit a GET request on the endpoint - 0.0.0.0/friends/<email> and ensure the details of that particular friend are returned.

For the user ‘[email protected]‘, it will be ‘[[email protected]](0.0.0.0/user/<a href=)'" target="_blank" rel="noopener noreferrer"">0.0.0.0/user/[email protected]'

3. Add a new friend using a POST request on the endpoint - 0.0.0.0/friends/ by using the below format in the request body:

{"email":"[email protected]","firstName":"Andy","lastName":"Smith","DOB":"1/1/1987"}

• The above is a reference for adding a new user with email [email protected].

Note: Please ensure using fictional/non-existent email domains by creating one or changing the spelling as done here (example.com). Avoid using actual email domains like gmail.com, yahoo.com.

4. Update a friend attribute(firstName, lastName, DOB) using a PUT request on the endpoint - 0.0.0.0/friends/<email>

• Use the below format in the request body for updating the DOB as 1/1/1989 & likewise for updating ‘firstName’,’lastName’.

{"DOB":"1/1/1989"}

5. Delete a friend by sumbitting a DELETE request on the endpoint 0.0.0.0/friends/<email>.

Modifying the access token validity:

1. Consider the below code snippet for access token validity which we have observed earlier in index.js file.

if (authenticatedUser(username,password)) {
    let accessToken = jwt.sign({
      data: password
    }, 'access', { expiresIn: 60 * 60 });

    req.session.authorization = {
      accessToken,username
  }

2. Now edit the ‘expiresIn’ attribute to 60 seconds to check the validity:

if (authenticatedUser(username,password)) {
    let accessToken = jwt.sign({
      data: password
    }, 'access', { expiresIn: 60 });

    req.session.authorization = {
      accessToken,username
  }

3. Repeat the User Registration & User Login steps on Postman to verify the changes.

• If you submit the login request within 60 seconds of generating the access token, you will be authenticated. Else, you will get the message
  {message: "Invalid Login. Check username and password"}.