Server Client + API: Node.js Implementation for the API
Server + API Architecture Scenario
This document is part of the Server + API Architecture Scenario and it explains how to implement the API in Node.js. Please refer to the scenario for information on the implemented solution.
Full source code for the Node.js API implementation can be found in this GitHub repository.
1. Define the API endpoint
We will use the Express web application framework to build our Node.js API.
Create a package.json File
Create a folder for your API, navigate into it and run
npm init. This will setup your
You can leave the default settings or change them as you see fit.
package.json looks like the following:
Install the Dependencies
Next, we need to set our dependencies. We will use the following modules:
express: This module adds the Express web application framework.
jwks-rsa: This library retrieves RSA signing keys from a JWKS (JSON Web Key Set) endpoint. Using
expressJwtSecretwe can generate a secret provider that will provide the right signing key to
express-jwtbased on the
kidin the JWT header. For more information refer to the node-jwks-rsa GitHub repository.
express-jwt: This module lets you authenticate HTTP requests using JWT tokens in your Node.js applications. It provides several functions that make working with JWTs easier. For more information refer to the express-jwt GitHub repository.
body-parser: This is a Node.js body parsing middleware. It extracts the entire body portion of an incoming request stream and exposes it on
req.bodyas something easier to interface with.For more information and several alternatives refer to the body-parser GitHub repository.
To install these dependencies run the following:
Implement the Endpoint
Navigate to your API directory and create a
server.js file. Your code needs to:
- Set the dependencies.
- Enable the request body parsing middleware.
- Implement the endpoint.
- Launch the API server.
This is our sample implementation:
Launch your API server using
node server and make an HTTP POST request to
localhost:8080/timesheets/upload. You should see a JSON response with a message
This is the POST /timesheets/upload endpoint.
So now we have our endpoint but anyone can call it. Continue to the next paragraph to see how we can fix this.
2. Secure the API endpoint
In order to validate our token we will use the
jwt function, provided by the express-jwt middleware, and the
jwks-rsa package to retrieve the public key from Auth0. The libraries do the following:
express-jwtwill decode the token and pass the request, the header and the payload to
jwks-rsawill then download all signing keys from the JWKS endpoint and see if a one of the signing keys matches the
kidin the header of the JWT. If none of the signing keys match the incoming
kid, an error will be thrown. If we have a match, we will pass the right signing key to
express-jwtwill the continue its own logic to validate the signature of the token, the expiration,
The steps we will follow in our code are:
- Create the middleware function to validate the Access Token.
- Enable the use of the middleware in our routes.
This is also a good time for you to implement the logic to save the timesheet entries to a local database, or whatever other storage mechanism you may prefer. This is our sample implementation (some code is omitted for brevity):
If we launch our server now and do an HTTP POST to
localhost:8080/timesheets/upload we should get the error message
Missing or invalid token (which is perfectly fine since we didn’t send an Access Token in our request).
In order to test the working scenario as well we need to:
- Get an Access Token. For details on how to do so refer to: Get an Access Token.
- Invoke the API while adding an
Authorizationheader to our request with the value
Bearer ACCESS_TOKEN(where ACCESS_TOKEN is the value of the token we retrieved in the first step).
3. Check the Client permissions
In this step we will add to our implementation the ability to check if the client has permissions (or
scope) to use our endpoint in order to upload a timesheet. In particular we want to ensure that the token has the correct scope, which is
In order to do this we will make use of the
express-jwt-authz Node.js package, so go ahead and add that to your project:
Now it is as simple as adding a call to
jwtAuthz(...) to your middleware to ensure that the JWT contain a particular scope in order to execute a particular endpoint. This is our sample implementation (some code is omitted for brevity):
If we invoke our API with a token that does not include this scope we should get the error message Forbidden with the HTTP status code
403. You can test this by removing this scope from your API.
That's it! You are done!