TypeScript is a popular programming language that is known for its type safety and enhanced readability. OpenID Connect is a widely-used authentication protocol that is built on top of the OAuth 2.0 protocol. In this tutorial, we will learn how to use TypeScript with OpenID Connect to build secure and reliable web applications.


Prerequisites

  1. Basic knowledge of TypeScript
  2. Familiarity with OpenID Connect protocol
  3. Node.js installed on your system


Step 1: Setup

The first step is to create a new TypeScript project. Open a terminal window and run the following command to create a new project directory:

mkdir my-app
cd my-app
npm init

Follow the prompts to initialize the project with default settings.

Next, install the required dependencies for OpenID Connect using npm. Run the following command to install the dependencies:

npm install openid-client @types/openid-client

This will install the openid-client library, which is a popular OpenID Connect client library for Node.js, and the @types/openid-client package, which provides TypeScript definitions for the openid-client library.


Step 2: Create OpenID Connect Configuration

In this step, we will create a configuration object for the OpenID Connect client. This object contains the necessary parameters for communicating with the OpenID Connect provider.

Create a new file called config.ts in the root directory of your project and add the following code:

import { Issuer } from 'openid-client';

export const getIssuer = async () => {
  return await Issuer.discover('https://example.com/auth/realms/myrealm');
};

export const getConfig = async () => {
  const issuer = await getIssuer();
  return {
    client_id: 'my-client-id',
    client_secret: 'my-client-secret',
    redirect_uri: 'http://localhost:3000/callback',
    response_types: ['code'],
    scope: 'openid profile email',
    token_endpoint_auth_method: 'client_secret_post',
    userinfo_endpoint: issuer.userInfoEndpoint,
    authorization_endpoint: issuer.authorizationEndpoint,
    token_endpoint: issuer.tokenEndpoint,
    jwks_uri: issuer.jwksUri,
  };
};

The getIssuer function discovers the OpenID Connect provider's configuration by retrieving the provider's metadata from the specified URL. The getConfig function returns a configuration object with the necessary parameters for communicating with the OpenID Connect provider.

In this example, we are using the client_secret_post authentication method for token exchange, which means that the client secret is sent in the request body instead of the URL.


Step 3: Create OpenID Connect Client

In this step, we will create an OpenID Connect client instance using the configuration object created in Step 2.

Create a new file called client.ts in the root directory of your project and add the following code:

import { Client } from 'openid-client';
import { getConfig } from './config';

export const getClient = async () => {
  const config = await getConfig();
  return new Client(config);
};

The getClient function creates a new OpenID Connect client instance with the configuration object returned by the getConfig function.


Step 4: Implement Authentication Flow

In this step, we will implement the authentication flow using the OpenID Connect client instance created in Step 3.

Create a new file called app.ts in the root directory of your project and add the following code:

import express from 'express';
import { getClient } from './client';

const app = express();
const port = 3000;

app.get('/', async (req, res) => {
  const client = await getClient();
  const authorizationUrl = client.authorizationUrl({
    scope: 'openid profile email',
state: 'random-state',
});
res.redirect(authorizationUrl);
});

app.get('/callback', async (req, res) => {
const client = await getClient();
const params = client.callbackParams(req);
const tokenSet = await client.callback('http://localhost:3000/callback', params, {
code_verifier: req.session.code_verifier,
});
req.session.tokenSet = tokenSet;
res.redirect('/profile');
});

app.get('/profile', async (req, res) => {
const { tokenSet } = req.session;
if (!tokenSet) {
res.redirect('/');
return;
}
const client = await getClient();
const userInfo = await client.userinfo(tokenSet.access_token);
res.send(userInfo);
});

app.listen(port, () => {
console.log(App listening at http://localhost:${port});
});

This code sets up an Express.js server that listens on port 3000. When a user visits the root URL `/`, the server redirects the user to the OpenID Connect provider's authorization URL, which includes the requested scopes and a random state value.

When the user grants permission to the application, the provider redirects the user back to the application's `/callback` URL with an authorization code. The `callback` function of the OpenID Connect client exchanges the authorization code for an access token and ID token, and stores them in the user's session.

The server then redirects the user to the `/profile` URL, which displays the user's profile information obtained from the userinfo endpoint using the access token.


Step 5: Test the Application

To test the application, start the server by running the following command in the terminal: 

node app.js

Open a web browser and visit `http://localhost:3000` to initiate the authentication flow. You should be redirected to the OpenID Connect provider's login page. After successfully authenticating, you should be redirected to the `/profile` URL, which displays your profile information.


Conclusion

In this tutorial, we learned how to use TypeScript with OpenID Connect to build secure and reliable web applications. We created an OpenID Connect client instance, implemented the authentication flow, and obtained the user's profile information. OpenID Connect provides a secure and standardized way of handling authentication and authorization in web applications, and TypeScript provides enhanced type safety and readability to our code.