Authentication and authorization in API's NodeJS: Implementation of login with social networks

Authentication and authorization are critical components of any web application, and implementing these features in NodeJS APIs is no exception. In this chapter, we'll talk about how to implement login with social networks, an increasingly common feature in many websites and applications.

Login with social networks is a form of authentication in which users can access an application using their existing social network accounts. Not only does this improve the user experience by avoiding the need to remember yet another set of credentials, but it can also increase security as many social media providers have advanced security features like two-factor authentication.

To implement social media login in a NodeJS API, you will need a package called Passport. Passport is an extremely flexible and modular authentication middleware for Node.js that can be fully integrated into your application.

First, you need to install Passport in your NodeJS project. This can be done using npm (Node Package Manager) with the following command: npm install passport. Next, you'll need to install the Passport-specific package for the social network you want to use for authentication. For example, for Facebook you would use: npm install passport-facebook.

Once Passport is installed, you will need to configure it in your application. This involves creating an authentication strategy, which is an object that Passport uses to authenticate users. Each authentication strategy requires a verification function, which accepts credentials (in this case, a Facebook access token) and invokes a callback function with the authenticated user.

Here is an example of what this might look like:

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const FacebookStrategy = require('passport-facebook').Strategy;

passport.use(new FacebookStrategy({
    clientID: FACEBOOK_APP_ID,
    clientSecret: FACEBOOK_APP_SECRET,
    callbackURL: "http://www.example.com/auth/facebook/callback"
  },
  function(accessToken, refreshToken, profile, done) {
    User.findOrCreate({ facebookId: profile.id }, function (err, user) {
      return done(err, user);
    });
  }
));

In this example, the findOrCreate function is used to find the user in the database based on the Facebook ID or create a new user if none is found. The returned user object is then passed to the done function, which Passport uses to establish a login session.

For the callback route, you'll need to configure a route in your app that matches the callback URL you provided when creating the Facebook strategy. When a user tries to login with Facebook, they will be redirected to this URL after successfully authenticating with Facebook.

app.get('/auth/facebook/callback',
  passport.authenticate('facebook', { failureRedirect: '/login' }),
  function(req, res) {
    // Successful authentication, redirect home.
    res.redirect('/');
  });

Finally, to start the authentication process, you'll need to create a route that redirects the user to Facebook. This can be done using Passport's authenticate method, as shown below:

app.get('/auth/facebook',
  passport.authenticate('facebook'));

This is a basic example of how to implement login with social networks in a NodeJS API using Passport. However, Passport supports a wide range of authentication strategies including Twitter, Google and more, so you can adapt this example to work with almost any social media provider.

Also, it is important to note that authentication is only the first step. Once a user is authenticated, you will also need to implement authorization, which is the process of determining what an authenticated user is allowed to do. This is usually done using some form of role-based access control (RBAC), but that's beyond the scope of this chapter.

In summary, implementing login with social networks can improve the user experience and increase the security of your application. With Passport, this functionality can be added to a NodeJS API relatively simply and straightforwardly.