Cat's Nest! OpenID Connect Authentication with NestJS, React, and MongoDB

Photo by Stephen Doxsee

In this post, we’ll explore how to create a NestJS back-end that handles OpenID Connect authentication for a React app that it serves up with an express-session. The session store will share the MongoDB instance that is also used for storing cats.

Disclaimer: I’m not a cat guy. I’m using cats for this tutorial because the NestJS documentation did. However, I did take the picture for this post when we discovered 5 wild baby cats in our backyard! They’ve all since found loving homes :)

Table of Contents

  1. Quickstart
    1. Start the back-end
    2. Start the front-end
    3. Try it out
  2. Why NestJS
  3. Create the back-end
    1. Add AuthModule
    2. Add dependencies
    3. Add OidcStrategy
      1. Create LoginGuard to handle the OIDC dance
      2. Replace AuthController with this
      3. Add SessionSerializer
      4. Update AuthModule
    4. Update AppModule
    5. Add some Cat CRUD
      1. Add AuthenticatedGuard
      2. Add CatsModule
      3. Configure MongoDB
  4. Create the front-end
    1. Add reactstrap
    2. Add Cat interface
    3. Add CatsTable component
    4. Replace App.tsx with…
    5. Proxy requests to back-end in development
  5. Start everything up
  6. Serve static resources in production
  7. References
  8. Conclusion


The source can be found at

git clone
cd cats-nest

Start the back-end

cd back-end
npm install

Add `.env’ like this. I realize I’m sharing credentials for a Google OAuth2 Client and a MongoDB user but that’s just for you to test this out easily. Please feel free create/use your own.


Now you can start the backend on port 3000.

npm run start:dev

Start the front-end

In a new terminal

cd front-end
npm install
PORT=3001 npm start

Try it out

Your browser will open to http://localhost:3001. Click Login, sign in with your google credentials, give consent to “Cat’s Nest”, and you’ll see your name and any cats that are in the database!

Cat's Nest Screenshot

Use to create/read/update cat records. Here are some examples

  • Create: http -f POST localhost:3000/cats name=Gladiator age=4 breed=General
  • Read: http localhost:3000/cats
  • Update: http -f PUT localhost:3000/cats/5e3859ab9ffdd4d02913e0fc name=Maximus

Note: You’ll need to temporarily comment out @UseGuards(AuthenticatedGuard) on CatsController if you want to run the commands above since you’re not authenticated.

Why NestJS

JavaScript development can be a bit like the wild west. There are lots of ways to skin a cat (sorry, bad joke). I’ve done a fair bit on the front-end with JavaScript before but not so much on the back-end. NestJS promises to bring best-practice architecture and consistency to Node applications. It actually feels a lot like Spring Boot development (which is a win from my perspective).

Create the back-end

npm i -g @nestjs/cli
mkdir cats-nest && cd cats-nest
nest new back-end && cd back-end

If you run npm run start:dev you’ll see “Hello, World!” on http://localhost:3000! Cool, but we’ll want to go further than that ;) Let’s start working on Authentication

Add AuthModule

nest g module auth
nest g controller auth
nest g service auth

We won’t be using AuthService in this tutorial but we’re creating an empty one as this is where you’d probably check the Identity Provider’s user against what you care about in your own database.

Add dependencies

npm i --save @nestjs/passport passport openid-client @nestjs/config express-session @nestjs/mongoose mongoose connect-mongo

Here’s what those dependencies are about:

  • @nestjs/passport - NestJS modules for working with passport
  • passport - Passport itself–authentication middleware for Node.js
  • openid-client - OIDC certified client library with a passport strategy
  • @nestjs/config - NestJS configuration support
  • express-session - For a session-based application
  • @nestjs/mongoose - NestJS modules for working with mongoose
  • mongoose - Mongoose itself–Node.js ODM for MongoDB
  • connect-mongo - Express session store that uses MongoDB

Add OidcStrategy

Let’s create an OpenID Connect passport strategy, based on the node-openid-client project.

// auth/oidc.strategy.ts
import { UnauthorizedException } from '@nestjs/common';
import { PassportStrategy } from '@nestjs/passport';
import { Strategy, Client, UserinfoResponse, TokenSet, Issuer } from 'openid-client';
import { AuthService } from './auth.service';

export const buildOpenIdClient = async () => {
  const TrustIssuer = await`${process.env.OAUTH2_CLIENT_PROVIDER_OIDC_ISSUER}/.well-known/openid-configuration`);
  const client = new TrustIssuer.Client({
  return client;

export class OidcStrategy extends PassportStrategy(Strategy, 'oidc') {
  client: Client;

  constructor(private readonly authService: AuthService, client: Client) {
      client: client,
      params: {
        redirect_uri: process.env.OAUTH2_CLIENT_REGISTRATION_LOGIN_REDIRECT_URI,
        scope: process.env.OAUTH2_CLIENT_REGISTRATION_LOGIN_SCOPE,
      passReqToCallback: false,
      usePKCE: false,

    this.client = client;

  async validate(tokenset: TokenSet): Promise<any> {
    const userinfo: UserinfoResponse = await this.client.userinfo(tokenset);

    try {
      const id_token = tokenset.id_token
      const access_token = tokenset.access_token
      const refresh_token = tokenset.refresh_token
      const user = {
      return user;
    } catch (err) {
      throw new UnauthorizedException();

Create LoginGuard to handle the OIDC dance

// src/auth/login.guard.ts
import { ExecutionContext, Injectable } from '@nestjs/common';
import { AuthGuard } from '@nestjs/passport';

export class LoginGuard extends AuthGuard('oidc') {
  async canActivate(context: ExecutionContext) {
    const result = (await super.canActivate(context)) as boolean;
    const request = context.switchToHttp().getRequest();
    await super.logIn(request);
    return result;

Replace AuthController with this

// auth/auth.controller.ts
import {
} from '@nestjs/common';
import { Response } from 'express';

import { LoginGuard } from './login.guard';
import { Issuer } from 'openid-client';

export class AuthController {

  login() {}

  user(@Request() req) {
    return req.user
  loginCallback(@Res() res: Response) {
  async logout(@Request() req, @Res() res: Response) {
    const id_token = req.user ? req.user.id_token : undefined;
    req.session.destroy(async (error: any) => {
      const TrustIssuer = await`${process.env.OAUTH2_CLIENT_PROVIDER_OIDC_ISSUER}/.well-known/openid-configuration`);
      const end_session_endpoint = TrustIssuer.metadata.end_session_endpoint;
      if (end_session_endpoint) {
        res.redirect(end_session_endpoint + 
          '?post_logout_redirect_uri=' + process.env.OAUTH2_CLIENT_REGISTRATION_LOGIN_POST_LOGOUT_REDIRECT_URI + 
          (id_token ? '&id_token_hint=' + id_token : ''));
      } else {

The two endpoints annotated with @UseGuards(LoginGuard) are those involved in the two kinds of authentication OAuth2 authorization code flow requires (i.e. user and client)

  1. /login: redirects to authorization endpoint of Identity Provider for front-channel user authentication
  2. /callback: receives the code grant from the Identity Provider and exchanges it, back-channel, for an id_token by means of client credential authentication

The /logout endpoint provides a way of using the end_session_endpoint if such an endpoint is discovered while the req.user object returned at the /user endpoint will be populated automatically by passport once the user is authenticated.

Add SessionSerializer

The way passport populates the req.user is by using a PassportSerializer. Passport serializes and deserializes user instances to and from the session using a PassportSerializer. Since we’re only using the user from the Identity Provider, we have a vanilla serializer that uses the user “as is”.

// src/auth/session.serializer.ts
import { PassportSerializer } from '@nestjs/passport';
import { Injectable } from '@nestjs/common';
export class SessionSerializer extends PassportSerializer {
  serializeUser(user: any, done: (err: Error, user: any) => void): any {
    done(null, user);
  deserializeUser(payload: any, done: (err: Error, payload: string) => void): any {
    done(null, payload);

Update AuthModule

Let’s let our AuthModule know about our strategy, guard, and serializer.

// src/auth/auth.module.ts
import { Module } from '@nestjs/common';
import { PassportModule } from '@nestjs/passport';
import { OidcStrategy, buildOpenIdClient } from './oidc.strategy';
import { SessionSerializer } from './session.serializer';
import { AuthService } from './auth.service';
import { AuthController } from './auth.controller';

const OidcStrategyFactory = {
  provide: 'OidcStrategy',
  useFactory: async (authService: AuthService) => {
    const client = await buildOpenIdClient(); // secret sauce! build the dynamic client before injecting it into the strategy for use in the constructor super call.
    const strategy = new OidcStrategy(authService, client);
    return strategy;
  inject: [AuthService]

  imports: [
    PassportModule.register({ session: true, defaultStrategy: 'oidc' }),
  controllers: [AuthController],
  providers: [OidcStrategyFactory, SessionSerializer, AuthService],
export class AuthModule {}

Update AppModule

And let’s be sure to let our AppModule know about our ConfigModule so that we can use our .env config file!

// app.module.ts
import { Module } from '@nestjs/common';
import { AuthModule } from './auth/auth.module';
import { ConfigModule } from '@nestjs/config';
import { AppController } from './app.controller';
import { AppService } from './app.service';

  imports: [
    ConfigModule.forRoot(), // so that we can pull in config
  controllers: [AppController],
  providers: [AppService],
export class AppModule {}

If you remember when we started our app originally, we just saw “Hello World!”. Let’s go to our AppController to add a link to login/logout and, if we have a user, display the user’s name instead!

import { Controller, Get, Request } from '@nestjs/common';
import { AppService } from './app.service';

export class AppController {
  constructor(private readonly appService: AppService) {}

  getHello(@Request() req): string {
    if (req.user) {
      return 'Hello, ' + + '! <a href="/logout">Logout</a>';
    } else {
      return this.appService.getHello() + ' <a href="/login">Login</a>';

Finally, we need to replace main.ts with the following to configure our session and to use passport with it.

// src/main.ts
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import * as session from 'express-session';
import * as passport from 'passport';
import * as connectMongo from 'connect-mongo';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  const MongoStore = connectMongo(session);

  // Authentication & Session
    store: new MongoStore({ url: process.env.MONGODB_URL}), // where session will be stored
    secret: process.env.SESSION_SECRET, // to sign session id
    resave: false, // will default to false in near future:
    saveUninitialized: false, // will default to false in near future:
    rolling: true, // keep session alive
    cookie: {
      maxAge: 30 * 60 * 1000, // session expires in 1hr, refreshed by `rolling: true` option.
      httpOnly: true, // so that cookie can't be accessed via client-side script
  await app.listen(3000);

If we drop the .env file in and start the app with npm run start:dev, we’ll see an error

node_modules/connect-mongo/src/types.d.ts:8:23 - error TS2688: Cannot find type definition file for 'express-session'.

We can fix that by adding type definitions for the express-session library

npm i --save-dev @types/express-session

Now, when we go to http://localhost:3000/login, we’ll be directed to Google for user authentication!

Add some Cat CRUD

Add AuthenticatedGuard

In order to prevent unauthorized calls from disturbing our cats, let’s create a generic AuthenticatedGuard that only allows calls by authenticated users on the annotated controller class or method.

// src/common/guards/authenticated.guard.ts
import { ExecutionContext, Injectable, CanActivate } from '@nestjs/common';

export class AuthenticatedGuard implements CanActivate {
  async canActivate(context: ExecutionContext) {
    const request = context.switchToHttp().getRequest();
    return request.isAuthenticated();

Add CatsModule

Create the CatsModule and related controller and service

nest g module cats
nest g controller cats
nest g service cats

Now, copy paste from the NestJS sample app providing the basics, from controller to model, to create Cat collections on MongoDB. See and replace the generated files with the files from the repository.

Let’s annotate the CatsController with @UseGuards(AuthenticatedGuard) to protect its endpoints and add an update method.

  async update(@Param() params, @Body() createCatDto: CreateCatDto) {
    await this.catsService.update(, createCatDto);

and let’s add an update method to CatsService

  async update(id: string, createCatDto: CreateCatDto): Promise<Cat> {
    const updatedCatDto = this.catModel.findByIdAndUpdate(id, createCatDto, { new: true });
    return updatedCatDto;

Configure MongoDB

Finally, we’ll add the following to our imports array in our AppModule

MongooseModule.forRoot(process.env.MONGODB_URL), // so that we can use Mongoose

Create the front-end

For the front-end we’ll be using create-react-app to build a react application with TypeScript.

npx create-react-app front-end --template typescript --use-npm
cd front-end

Add reactstrap

npm i --save bootstrap reactstrap
npm i --save-dev @types/reactstrap

Add import 'bootstrap/dist/css/bootstrap.min.css'; to index.tsx

Add Cat interface

// cat.interface.tsx
export interface Cat {
  readonly _id: string;
  readonly name: string;
  readonly age: number;
  readonly breed: string;

Add CatsTable component

// cats.table.tsx
import React from 'react'
import { Table } from 'reactstrap'
import { Cat } from './cat.interface'

interface Props {
  cats: Cat[]

const CatsTable = (props: Props) => (
  <Table hover responsive>
      {props.cats.length > 0 ? ( => (
          <tr key={cat._id}>
      ) : (
          <td colSpan={3}>No cats</td>

export default CatsTable

Replace App.tsx with…

// App.tsx
import React, { useState, useEffect } from 'react';
import './App.css';
import { Cat } from './cat.interface';
import CatsTable from './cats.table';
import { Jumbotron, Button } from 'reactstrap';

const App = () => {

  // Data
  const catsData : Cat[] = []
  const userData : User = {}

  interface User {
    id_token?: string,
    access_token?: string,
    refresh_token?: string,
    userinfo?: UserInfo

  interface UserInfo {
    name?: string

  // Setting state
  const [ cats, setCats ] = useState(catsData)
  const [ user, setUser ] = useState(userData)

  const getCats = async () => {
    try {
      const response = await fetch('/cats')
      const cats = await response.json()
    } catch {
      // add better error handling here (e.g. 401?)

  useEffect(() => {
    // Create a scoped async function in the hook
    async function runAsync() {
      try {
        const response = await fetch('/user')
        const userResponse = await response.text()
        if (userResponse !== '') {
      } catch(error) {
        // add better error handling here
    // Execute the created function directly
  // eslint-disable-next-line
  }, [])

  const login = () => {window.location.replace('/login')}
  const logout = () => {window.location.replace('/logout')}
  const isEmpty = (obj: Object) => {return Object.keys(obj).length === 0 && obj.constructor === Object}

  return (
        <h1 className="display-3">Cat's Nest! <span role="img" aria-label="smiling cat">😺</span></h1>
        {user && user.userinfo && 
        <p className="lead">Hey {}</p>
        <p className="lead">
          {isEmpty(user) ? 
          <Button color="primary" onClick={login}>Login</Button>
          <Button color="danger" onClick={logout}>Logout</Button>
      {!isEmpty(user) && <CatsTable cats={cats}/>}

export default App;

Proxy requests to back-end in development

Finally, to get our client to proxy certain calls to our NestJS back-end on port 3000, we add http-proxy-middleware as per the CRA docs

npm i --save-dev http-proxy-middleware

And add the following setupProxy.js file to configure it

// setupProxy.js
const proxy = require('http-proxy-middleware');
module.exports = function(app) {
      target: 'http://localhost:3000',
      changeOrigin: true,
      xfwd: true,

Start everything up

Note: Before we fire up the front-end on 3001, we need to change environment variables in the back-end’s .env file to point to 3001 instead of 3000. That’s because we want all redirects to come to the front-end in development. You’ll want to change the two environment variables back to 3000 when running this in production.

Start the back-end

npm run start:dev

In another terminal window, start the front-end

PORT=3001 npm start

Watch the magic happen!

Serve static resources in production

To serve up static resources (like a React application) in production, add the dependency @nestjs/serve-static

npm i --save @nestjs/serve-static

and add the following to our imports array in AppModule to point to our front-end build.

      rootPath: join(__dirname, '../..', 'front-end/build'),
    }), // so that front-end can be served up by back-end

Note: You’ll also want to remove AppController and AppService from AppModule so that the “Hello, World!” endpoint won’t conflict with the static resources we’re serving up.



Hope you enjoyed this tutorial. With NestJS and create-react-app, it’s pretty easy to create a clean session-based OIDC application!

Let me know what you think in the comments section.

Thanks for reading!

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