Creating a Self-Signed HTTPS Certificate for an Express Server

In this blog post, we will learn how to create a self-signed HTTPS certificate for a Node.js application to test locally. A self-signed certificate is sufficient for establishing a secure, HTTPS connection during development, even though browsers may display a warning that the certificate is not trusted.

To begin, you need to have OpenSSL installed on your system. If it is not installed, you can check by typing openssl in your terminal. On a Mac, you can install OpenSSL using brew install openssl if you have Homebrew installed. Otherwise, you can search on Google for instructions on how to install OpenSSL on your particular system.

Once OpenSSL is installed, run the following command in your terminal:

openssl req -nodes -new -x509 -keyout server.key -out server.cert

This command will generate a self-signed certificate and prompt you to answer a few questions to customize it. You can leave most of the fields blank, but make sure to set the Common Name to localhost and provide an email address if desired.

After running this command, you will have two files in the folder where you ran the command: server.cert (the self-signed certificate file) and server.key (the private key of the certificate).

To use these files to establish an HTTPS connection, you will need to put them in a location accessible by your application and configure your server accordingly.

Here is an example of using the https core module and Express to create an HTTPS server:

const https = require('https');
const fs = require('fs');
const express = require('express');

const app = express();

app.get('/', (req, res) => {
  res.send('Hello HTTPS!');
});

https.createServer({
  key: fs.readFileSync('server.key'),
  cert: fs.readFileSync('server.cert')
}, app).listen(3000, () => {
  console.log('Listening...');
});

In the example above, we create an Express app and define a single route that returns a simple message. The https.createServer method is used to create the HTTPS server, and the key and cert options are set to the contents of the server.key and server.cert files, respectively.

Without adding the certificate, if you try to connect to https://localhost:3000, the browser will display a warning message. However, after adding the certificate, the browser will still show a warning about the invalid certificate but will allow you to proceed with the HTTPS connection.

Remember to replace any file paths in the code with the appropriate paths to your certificate files.

And that’s it! You now have a self-signed HTTPS certificate that you can use to test your Node.js applications locally.

Tags: self-signed certificate, HTTPS server, Express, Node.js, OpenSSL