Authentication and Authorization in Module Federation

In the realm of micro frontends, applications are fragmented into compact, standalone units that can be deployed independently. As I discussed in my prior article, ‘Enabling Micro-front end Architecture’, the importance of robust security measures, especially authentication, and authorization, cannot be overstated. With the advent of Webpack 5’s Module Federation, we now have the capability to distribute modules across various builds. The pressing question then arises: how can we guarantee secure access to these shared modules?

In this article, we’ll delve into the intricacies of implementing authentication and authorization when using Module Federation.

Understanding Authentication and Authorization

Before diving into the specifics, let’s clarify the difference between authentication and authorization:

• Authentication: It’s the process of verifying the identity of a user. In simpler terms, it answers the question, “Who are you?”
• Authorization: Once a user’s identity is verified, authorization determines what they can and cannot do. It answers the question, “What are you allowed to do?”

A Visual Representation of the Authentication and Authorization Flow

In the sequence diagram:

1. The user sends a login request to the host application (App1).
2. App1 authenticates the user.
3. Upon successful authentication, App1 returns a JWT token (or similar authentication token) to the user.
4. The user then tries to access a remote module from App2 through App1.
5. App2 performs an authorization check using the provided JWT token.
6. If the authorization check is successful, App2’s remote module is rendered to the user.

Implementing Authentication and Authorization in Module Federation

1. Secure the Remote Entry

The first step is to ensure that the remoteEntry.js file, which is the entry point for our remote modules, is secure. This can be achieved using standard web authentication techniques.

For instance, if your application uses JSON Web Tokens (JWT), the remote entry can be secured by checking for a valid JWT before serving the file.

2. Propagate User Context

When a host application interacts with a remote module, the user context (like authentication tokens or user roles) should be propagated to the remote module. This ensures that the remote module has enough context to make authorization decisions.

3. Implement Authorization Checks in Remote Modules

Once the remote module has the necessary user context, it can implement its own authorization checks. For instance, if a remote module exposes an admin dashboard, it can check if the propagated user role has admin privileges before rendering the dashboard.

4. Handle Authentication Failures

It’s crucial to handle scenarios where authentication fails gracefully. If a user tries to access a remote module without proper authentication, they should be redirected to a login page or be shown an appropriate error message.

5. Use Secure Communication

When sharing modules or propagating user context, always use secure communication channels like HTTPS. This ensures that sensitive information like authentication tokens is not exposed to potential attackers.

Practical Example: Authenticating a Remote Module

Imagine a scenario where the host application (App1) has a user dashboard, and it wants to fetch a user’s profile component from a remote application (App2). However, this profile component should only be accessible to authenticated users.

Host Application (App1)

1. User Authentication:

// src/auth.js
export function authenticateUser(username, password) {
  // Logic to authenticate user
  // On successful authentication, return a JWT or similar token
  return jwtToken;
}

2. Accessing Remote Module with Token:

// src/App.js
import React from "react";
import RemoteUserProfile from "app2/UserProfile";

function App() {
  const userToken = authenticateUser("username", "password");

  return (
    <div>
      <h1>Welcome to App1</h1>
      <RemoteUserProfile token={userToken} />
    </div>
  );
}

export default App;

Remote Application (App2)

1. UserProfile Component with Authorization:

// src/UserProfile.js
export default function UserProfile({ token }) {
  // Use the token to make authorization checks
  if (!isValidToken(token)) {
    return <p>You do not have permission to view this profile.</p>;
  }

  return (
    <div>
      {/* User profile content */}
    </div>
  );
}

In this example:

• The host application (App1) authenticates the user and obtains a JWT token.
• App1 then tries to access the UserProfile component from App2 and passes the JWT token as a prop.
• App2’s UserProfile component receives the token and performs an authorization check.
• If the token is valid, the user profile is rendered; otherwise, an error message is displayed.

Conclusion

Security is paramount, especially in a modular architecture where different parts of an application can be developed and deployed independently. By implementing robust authentication and authorization mechanisms and ensuring secure communication, we can leverage the power of Module Federation without compromising on security.