Auth0 Remix Server

The missing library for authentication on the server with Remix

Please contribute!

What is this?

This is a library for authentication with Auth0 on the server with Remix.

It's built as part of the efforts to deliver the trance-stack. As such, the initial release of this library only covers the MVP needs of the stack. It will keep evolving over time and with your help.

Why?

Other solutions out there seem to miss the actual token validation and basic security measures. This library attempts to bridge that gap and also provide a convenient interface to use.

What is still missing?

• utilise the STATE parameter to prevent CSRF
• failed events should remove the user from the session automatically
• see if we can handle the callback while maintaining the session from before the login
• opt out of the session handling

How to use

Everything below assumes that you're using Remix and Auth0 and you're familiar with how they work.

Installation

npm install auth0-remix-server

Usage

Some steps below might be familiar to anyone who attempted this with the remix-auth-auth0 package.

Environment Variables

Environment variables are not required for the library, the examples only use them when configuring the authenticator. I do recommend using environment variables for sensitive information like client secrets and domain names.

• AUTH0_DOMAIN - The domain name of your Auth0 tenant
• AUTH0_CLIENT_ID - The client ID of your Auth0 application
• AUTH0_CLIENT_SECRET - The client secret of your Auth0 application
• APP_DOMAIN - The domain name of your application (http://localhost:3333 for local development)

1. Create an instance of the authenticator in src/auth.server.ts

// src/auth.server.ts
import { Auth0RemixServer } from 'auth0-remix-server';
import { getSessionStorage } from './sessionStorage.server'; // this is where your session storage is configured

export const authenticator = new Auth0RemixServer({
  clientDetails: {
    domain: process.env.AUTH0_DOMAIN,
    clientID: process.env.AUTH0_CLIENT_ID,
    clientSecret: process.env.AUTH0_CLIENT_SECRET,
    usePost: true // optional, defaults to true
  },
  callbackURL: `${process.env.APP_DOMAIN}/auth/callback`,
  refreshTokenRotationEnabled: true,
  failedLoginRedirect: '/',
  session: {
    store: getSessionStorage(),
    key: 'user' //optional
  },
  credentialsCallback: (credentials) => {
      // this gets called upon a successful callback or a credentials refresh event
  } //optional
});

2. Create a login route in src/routes/login.tsx

// src/routes/login.tsx
import { Form } from '@remix-run/react';
import { redirect } from '@remix-run/node';

export default () => {
  return (
    <Form action="/auth/auth0" method="post">
      <button>Login</button>
    </Form>
  );
};

3. Create an authentication route in src/routes/auth/auth0.ts

// src/routes/auth/auth0.ts
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = () => {
  authenticator.authorize();
};

Note You can modify the behaviour of the authorize method. More on that here

4. Create a callback route in src/routes/auth/callback.tsx

// src/routes/auth/callback.tsx
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = async ({ request }) => {
  await authenticator.handleCallback(request, {
    onSuccessRedirect: '/dashboard' // change this to be wherever you want to redirect to after a successful login
  });
};

5. Create a logout route in src/routes/logout.tsx

import { authenticator } from '../auth.server';
import { destroySession, getSessionFromRequest } from '../session.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = async ({ request }) => {
  const session = await getSessionFromRequest(request);

  await authenticator.logout(process.env.APP_DOMAIN, {
    'Set-Cookie': await destroySession(session) // this is where you destroy the session
  });
};

export const loader = action; // this to allow you to hit /logout directly in the browser

6. Optional - Create a dashboard route in src/routes/dashboard.tsx

import { json } from '@remix-run/node';
import { Form, useLoaderData } from '@remix-run/react';
import { authenticator } from '../auth.server';
import type { LoaderFunction } from '@remix-run/node';

export const loader: LoaderFunction = async ({ request, context }) => {
  const user = await authenticator.getUser(request, context); // this is what determines if the user is logged in or not
  return json({
    user: user
  });
};

export default () => {
  const { user } = useLoaderData<typeof loader>();
  return (
    <div>
      <div>Dashboard for {user.nickname || user.givenName || user.name}</div>
      <Form action="/logout" method="post">
        <button>Logout</button>
      </Form>
    </div>
  );
};

Session Storage Strategies

When you're constructing the authorizer, you can customize how the library behaves when refreshing the tokens.

// src/auth.server.ts
...
  session: {
    store: getSessionStorage(),
    strategy: SessionStrategy.Browser,  // <----- This line here
    key: 'user' //optional
  },
...

Keeping the session data in the cookie

The authenticator uses a session strategy to determine how to handle the case of refreshing the tokens. The default setting SessionStrategy.Browser assumes that you store all your tokens in a cookie and that you need to send the browser cookie headers whenever you refresh the tokens. This results in a literal page refresh, which is not ideal.

:note: This is most likely NOT going to be your use case.

Keeping the session data in a database

Ideally you will only store the session id in the cookie and leave the session data to be stored in a database. This is where the SessionStrategy.Server comes in. It assumes that you have a session id stored in a cookie and that once the ID is set upon login, you will be able to retrieve - and update - the session data from a database.

Caching the user profile

Unfortunately with the current implementation of Remix and the lack of a proper middleware, every loader runs in parallel, and they can generate a lot of noise towards Auth0.

In this situation you might want to have some sort of a "user profile caching" in place. Redis, Dyanmo, in-memory, you name it.

The auth0-remix-server offers you a way to do this.

// src/auth.server.ts
import {Auth0RemixServer} from 'auth0-remix-server';
import {getSessionStorage} from './sessionStorage.server';
import {UserProfile} from "./Auth0RemixTypes"; // this is where your session storage is configured

export const authenticator = new Auth0RemixServer({
  ...,
  profileCacheGet: async (accessToken: string): Promise<UserProfile> => {
      //return a UserProfile or throw an error if not found
  },
  profileCacheSet: async (accessToken: string, profile: UserProfile, expiresAt: number): Promise<void> => {
    // use the expiresAt as a TTL value if your cache storage supports such a thing.
    // Otherwise use it to invalidate the record yourself.
  },
  ...,
});

Securely decoding tokens

If you're using the contents of the tokens, you should always make sure that they're valid and haven't been tampered with. You can quickly verify the validity of the tokens by using the verifyToken and isValid methods on the authenticator described in the Validating Tokens section.

But if you want to decode the tokens and use the contents, you should use the decodeToken method .

import { authenticator } from './auth.server';
import { Token } from 'auth0-remix-server';

const decodedToken = await authenticator.decodeToken('your id token here', Token.ID);

The decodedToken will contain the contents of the IDToken but at this point you can be sure that it passed the cryptographic validation checks.

If the verification fails, the decodeToken method will throw the same set of errors as the verifyToken method throws. You can see the list of errors in the Errors section.

Validating Tokens

ID and Access Tokens can be decoded easily by anyone but in order to make sure that the data hasn't been tampered with, it's advisable to validate the tokens against the public keys provided by Auth0.

You can do this by using the verifyToken and the isValid methods on the authenticator. They both take a Token as a second argument because the validation process is different for each type of token.

The isValid function is a quick yes/no answer to whether or not the token is valid.

import { authenticator } from './auth.server';
import { Token } from 'auth0-remix-server';

await authenticator.isValid('your access token here', Token.AccessToken); // returns true or false

The verifyToken function will resolve if the token is valid and will reject if it's not.

import { authenticator } from './auth.server';
import { Token } from 'auth0-remix-server';

try {
  await authenticator.verifyToken('your id token here', Token.ID);
} catch (error) {
  // handle the error
  const { code, message } = error as TokenError;
}

Modifying the Authorize process

Forcing a login

During the authrization process, if the user is already logged into Auth0, they will not be asked to log in again. You can change that behaviour by passing in the forceLogin option to the authorize method.

// src/routes/auth/auth0.ts
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = () => {
  authenticator.authorize({
    forceLogin: true
  });
};

Forcing a signup

You can force the user to the sign-up page by passing in the forceSignup option to the authorize method.

// src/routes/auth/auth0.ts
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = () => {
  authenticator.authorize({
    forceSignup: true
  });
};

Forcing a silent authentication

You can force the user to the sign-up page by passing in the forceSignup option to the authorize method.

// src/routes/auth/auth0.ts
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = () => {
  authenticator.authorize({
    silentAuth: true
  });
};

Combining the forceLogin, forceSignup and silentAuth parameters to control the behavior of the authorization request produce the following results:

parameter	No existing session	Existing session
{forceSignup: true}	Shows the signup page	Redirects to the callback url
{forceLogin: true}	Shows the login page	Shows the login page
{forceSignup: true, forceLogin: true}	Shows the signup page	Shows the signup page
{silentAuth: true, forceLogin: true}	Type Error / Silent auth	Type Error / Silent auth
{silentAuth: true, forceSignup: true}	Needs testing	Needs testing

Adding a connection

You can also specify the name of the connection configured to your application.

// src/routes/auth/auth0.ts
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = () => {
  authenticator.authorize({
    connection: 'google'
  });
};

Adding custom redirect url parameters

You can also specify custom parameters to be added to the redirect url.

// src/routes/auth/auth0.ts
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = () => {
  authenticator.authorize({
    callbackParams: {
      foo: 'bar'
    }
  });
};

Adding a redirect url override for each authorization request

You can also specify a redirect url to be used for each authorization request. This will override the default redirect url that you specified when you created the authenticator.

// src/routes/auth/callback.tsx
import { authenticator } from '../../auth.server';
import type { ActionFunction } from '@remix-run/node';

export const action: ActionFunction = async ({ request }) => {
  await authenticator.handleCallback(request, {
    onSuccessRedirect: '/dashboard', // change this to be wherever you want to redirect to after a successful login
    onFailureRedirect: '/login' // change this to be wherever you want to redirect to after a failed login
  });
};

Errors

Authorization errors

When the authorization process fails, the failure redirect url will be called with an error query parameter that contains the error code auth0 has given us.

Verification errors

The verification errors each have a code property that you can use to determine what went wrong.

Code	Description
ERR_JWT_CLAIM_VALIDATION_FAILED	The JWT claim validation failed.
ERR_JWT_EXPIRED	The JWT has expired.
ERR_JWT_INVALID	The JWT is invalid.
ERR_JWKS_INVALID	The JWKS is invalid.
ERR_JWKS_NO_MATCHING_KEY	No matching key was found.
ERR_JWKS_MULTIPLE_MATCHING_KEYS	Multiple matching keys were found.

Gotchas

Accessing the tokens

When you instantiate the authenticator, you can pass in a credentialsCallback function. This function will be called when the user is successfully authenticated or when the access token is refreshed.

It will contain the credentials obtained from Auth0.

The credentials object looks like this:

{
  accessToken: string; // the access token
  refreshToken: string; // the refresh token
  expiresIn: number; // the number of seconds until the access token expires
  expiresAt: number; // the timestamp when the access token expires
  lastRefreshed: number; // the timestamp when the access token was last refreshed
}

Refresh Token Rotation

The refreshTokenRotationEnabled option is set to false by default. This is because it's off by default in Auth0.

When it's set to true, the refresh tokens will be appended to the session. This is secure and makes it easier to manage the refresh tokens.

Please see this post and this one for more information.

Refreshing the access token

Until this issue in Remix is shipped, you'll need to pass in the context from the loaders and actions to the getUser method.

This ensures (in an awkward way) that the refresh only happens once.

It's not pretty but once we have proper middleware in Remix, it should clean up.