By David Patrick
This tutorial demonstrates how to add authorization to an Express.js API.We recommend that you log in to follow this quickstart with examples configured for your account.
New to Auth0? Learn how Auth0 works and read about implementing API authentication and authorization using the OAuth 2.0 framework.

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Configure Auth0 APIs

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Create an API

In the APIs section of the Auth0 dashboard, click Create API. Provide a name and an identifier for your API, for example, https://quickstarts/api. You will use the identifier as an audience later, when you are configuring the Access Token verification. Leave the Signing Algorithm as RS256.
Create API
By default, your API uses RS256 as the algorithm for signing tokens. Since RS256 uses a private/public keypair, it verifies the tokens against the public key for your Auth0 account. The public key is in the JSON Web Key Set (JWKS) format, and can be accessed here.
We recommend using the default RS256 signing algorithm for your API. If you need to use the HS256 algorithm, see the HS256 integration sample.

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Define permissions

Permissions let you define how resources can be accessed on behalf of the user with a given access token. For example, you might choose to grant read access to the messages resource if users have the manager access level, and a write access to that resource if they have the administrator access level. You can define allowed permissions in the Permissions view of the Auth0 Dashboard’s APIs section.
Configure Permissions
This example uses the read:messages scope.
This example demonstrates:
  • How to check for a JSON Web Token (JWT) in the Authorization header of an incoming HTTP request.
  • How to check if the token is valid, using the JSON Web Key Set (JWKS) for your Auth0 account. To learn more about validating Access Tokens, see Validate Access Tokens.

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Validate Access Tokens

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Install dependencies

This guide shows you how to protect an Express API using the express-oauth2-jwt-bearer middleware. First install the SDK using npm. 
npm install --save express-oauth2-jwt-bearer

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Configure the middleware

Configure express-oauth2-jwt-bearer with your Domain and API Identifier. 
// server.js

const express = require('express');
const app = express();
const { auth } = require('express-oauth2-jwt-bearer');

// Authorization middleware. When used, the Access Token must
// exist and be verified against the Auth0 JSON Web Key Set.
const checkJwt = auth({
  audience: '{yourApiIdentifier}',
  issuerBaseURL: `https://{yourDomain}/`,
});
The checkJwt middleware shown above checks if the user’s Access Token included in the request is valid. If the token is not valid, the user gets a 401 Authorization error when they try to access the endpoints. The middleware doesn’t check if the token has the sufficient scope to access the requested resources.

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Protect API Endpoints

The routes shown below are available for the following requests:
  • GET /api/public: available for non-authenticated requests
  • GET /api/private: available for authenticated requests containing an access token with no additional scopes
  • GET /api/private-scoped: available for authenticated requests containing an access token with the read:messages scope granted
To protect an individual route that requires a valid JWT, configure the route with the checkJwt express-oauth2-jwt-bearer middleware. 
// server.js

// This route doesn't need authentication
app.get('/api/public', function(req, res) {
  res.json({
    message: 'Hello from a public endpoint! You don\'t need to be authenticated to see this.'
  });
});

// This route needs authentication
app.get('/api/private', checkJwt, function(req, res) {
  res.json({
    message: 'Hello from a private endpoint! You need to be authenticated to see this.'
  });
});
You can configure individual routes to look for a particular scope. To achieve that, set up another middleware with the requiresScope method. Provide the required scopes and apply the middleware to any routes you want to add authorization to. Pass the checkJwt and requiredScopes middlewares to the route you want to protect. 
// server.js
const { requiredScopes } = require('express-oauth2-jwt-bearer');

const checkScopes = requiredScopes('read:messages');

app.get('/api/private-scoped', checkJwt, checkScopes, function(req, res) {
  res.json({
    message: 'Hello from a private endpoint! You need to be authenticated and have a scope of read:messages to see this.'
  });
});
In this configuration, only Access Tokens with the read:messages scope can access the endpoint.
What can you do next?
Configure other identity providersEnable multifactor authentication
Learn about attack protectionLearn about rules
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