Node.js Express API Authorization Tutorial

This tutorial shows how to add authorization to Node.js Express API with PlusAuth. If you do not have a PlusAuth account, register from here.

Create PlusAuth Client

After you sign up or log in to PlusAuth, you need to create a client to get the necessary configuration keys in the dashboard. Go to Clients and create a client with the type of Server to Server Application

Configure Client

Get Client Properties

You will need your Client Id and Client Secret for interacting with PlusAuth. You can retrieve them from the created client's details.

Configure APIs

Create API

API is a definition in PlusAuth equals to your services which you want to secure. You need to create an API to add authorization to your app. Go to Api's and create a new API. Provide a name and audience to your api. Audience must be a URL that identifies your api, like https://example.com/api.

Create API Permissions

After you create API, you can create permissions for it. Permissions allow you to define how resources can be accessed with a specific access token. Go to Dashboard > Api's and click on the Permissions button on the row at the data table which contains your API.

Authorize Client

Finally, authorize your client in your api to grant permissions. Go to Dashboard > Api's , then select your api and navigate to Authorized Clients. Add your client to the Authorized Clients list and grant permissions to it.

Configure Node.js to add Authorization

Create a Node.js Express application or download the sample project from the link on the top of the page.

Install the dependencies

To get started, install the following dependencies.

• body-parser - Node.js body parsing middleware
• node-jsonwebtoken - JsonWebToken implementation for node.js
• jwks-rsa - Library to retrieve signing keys from a JWKS
• dotenv - Module to load environment variables from a .env file

# installation with npm
npm install body-parser jsonwebtoken jwks-rsa dotenv cors --save

Create the .env file

Create the .env file in the root of your app and add your PlusAuth variables and values to it.

# .env
PLUSAUTH_ISSUER=https://<YOUR-TENANT-ID>.plusauth.com
PLUSAUTH_AUDIENCE=<YOUR_AUDIENCE>
PORT=3000

Configure Express Application

We will configure our Express application in a simple way. We will be using body-parser for request body parsing middleware

// server.js
const express = require("express");

(async () => {
  const app = express();

  app.use(cors());
  
  // Enable the use of request body parsing middleware
  app.use(bodyParser.json());
  app.use(
    bodyParser.urlencoded({
      extended: true,
    })
  );

})();

Configure Authorization Middleware

We will use jsonwebtoken and jwks-rsa to add authorization middleware.

// checkJwt.js

const jwksRsa = require('jwks-rsa');
const jwt = require('jsonwebtoken');

//jsonwebtoken options
const options = {
  audience: process.env.PLUSAUTH_AUDIENCE,
  issuer: `${process.env.PLUSAUTH_ISSUER}`, // Validate the issuer
  algorithms: ['RS256'], // Signing Algorithm
};

//jwks-rsa options
const jwksClient = jwksRsa({
  cache: true,
  rateLimit: true,
  jwksRequestsPerMinute: 5,
  jwksUri: `${process.env.PLUSAUTH_ISSUER}/.well-known/jwks.json`, // Signing Keys Uri
});

function getKey(header, callback) {
  jwksClient.getSigningKey(header.kid, function (err, key) {
    var signingKey = key.publicKey || key.rsaPublicKey;
    callback(null, signingKey);
  });
}

module.exports = (scope = null) => {
  return function (req, res, next) {
    // If token not present in request header return 401
    if (req.headers.authorization === undefined) {
      return res.status(401).json({ message: 'token not found' });
    }

    // Get Bearer token
    const token = req.headers.authorization.split(' ')[1];

    jwt.verify(token, getKey, options, function (err, decoded) {
      if (err) {
        return res.status(401).json({ message: err.message }); // return 401 if token validation failed
      }

      if (!scope) {
        // If scope not present for route, then return response since token validated successfully
        next();
      } else if (decoded.scope && decoded.scope.split(' ').includes(scope)) {
        // If scope present for the route and token has required scope then return response
        next();
      } else {
        // If scope present for the route but token doesn't have required scope then return 403
        return res.status(403).json({ message: 'Insufficient scope' });
      }
    });
  };
};

checkJwt middleware looks for access_token in the request header. If the access token is not provided or not valid, the response status will be 401 Unauthorized. In case token validation succeeds, the middleware checks for the requested scope as the second step. If the requested scope is not provided in the token, the response status will be 403 Forbidden.

Create and Protect API Endpoints

Finally, we will create API endpoints. We will be using checkJwt middleware here to validate jwt and check scopes for protecting resources with permissions.

// server.js

  // get users API endpoint (token requires users:read scope)
  app.get('/users', checkJwt('users:read'), function (req, res) {
    //send the response
    res.status(200).send('All Users List');
  });

  // create user API endpoint (token requires users:write scope)
  app.post('/users', checkJwt('users:write'), function (req, res) {
    //send the response
    res.status(200).send('New User Created');
  });

  // update user API endpoint (token requires users:update scope)
  app.put('/users', checkJwt('users:update'), function (req, res) {
    //send the response
    res.status(200).send('User Updated');
  });

  // update user API endpoint (token requires users:delete scope)
  app.delete('/users', checkJwt('users:delete'), function (req, res) {
      //send the response
      res.status(200).send('User Deleted');
    }
  );

See it in action

Start your app and follow the Using API section to see it in action.

Using API

You need to obtain an access token to call your API. This tutorial shows how OAuth Client Credentials Flow works for server-to-server communication where there is no user and login process. You will need your client's Client Id and Client Secret properties to acquire an access token in Client Credentials Flow. Also you must include Audience and Scope parameters to access your API.

Obtain Access Token

You can obtain an access token using the command line or another application. Create a POST request and enter the required parameters.

# bash

curl --request POST \
  --url 'https://<YOUR_TANENT_ID>.plusauth.com/oauth2/token' \
  --header 'content-type: application/x-www-form-urlencoded' \
  --data 'grant_type=client_credentials' \
  --data 'client_id=<YOUR_CLIENT_ID>' \
  --data 'client_secret=<YOUR_CLIENT_SECRET>' \
  --data 'audience=<YOUR_AUDIENCE>' \
  --data 'scope=<SCOPE>'

You may have noticed that the values defined in Configure Client and Configure APIs sections are used here. If you have used different values make sure to update this file accordingly.

Call Your API

• Calling Endpoint Without Access Token

If you request your protected endpoint without an access token, you will get a 401 Unauthorized error response.

# bash

> curl -i http://localhost:3000/users
HTTP/1.1 401 Unauthorized
Access-Control-Allow-Origin: *
Content-Type: application/json; charset=utf-8
Content-Length: 46
Connection: keep-alive
Keep-Alive: timeout=5

• Calling Endpoint With Access Token

If you request your protected endpoint with a valid access token, you will get a 200 OK response.

# bash

> curl -i http://localhost:3000/users \
-H "Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6ImF0K2p3dCIsImtpZCI6Inh4T3l2R0hWV3dCIsImtpZ..."
HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Content-Type: text/html; charset=utf-8
Content-Length: 14
Connection: keep-alive
Keep-Alive: timeout=5

All Users List

If you request your protected endpoint with insufficient scope, you will get 403 Forbidden error response.

# bash

> curl -i http://localhost:3000/users \
-H "Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6ImF0K2p3dCIsImtpZCI6Inh4T3l2R0hWV3dvc0dOMU9..."
HTTP/1.1 403 Forbidden
Access-Control-Allow-Origin: *
WWW-Authenticate: Bearer scope="users:read", error="Insufficient scope"
Content-Type: text/html; charset=utf-8
Content-Length: 18
Connection: keep-alive
Keep-Alive: timeout=5

Insufficient scope

As you see, the access token needs to have users:read scope to access the endpoint.