Onboarding Utility
Node.js
Nginx (Reverse Proxy)

A Complete Guide to Securely Connecting Node.js and Nginx (Reverse Proxy) Using Mutual TLS

How to use TLS, client authentication, and CA certificates in Node.js and Nginx (Reverse Proxy)

Create a private key and request a certificate for your Node.js server

Before you can teach your server to speak TLS, you will need a certificate issued by a trusted certificate authority (CA). If your organization already runs its own CA and you have a private key and certificate for your Node.js server, along with your CA's root certificate, you can skip to the next step.

If your organization does not yet run its own internal CA, you can read more about creating and running a CA using the open source smallstep software here.

$ step ca certificate "myserver.internal.net" server.crt server.key

Your certificate and private key will be saved in server.crt and server.key respectively.

Request a copy of your CA root certificate, which will be used to make sure each application can trust certificates presented by other applications.

$ step ca root ca.crt

Your certificate will be saved in ca.crt.

Configure Node.js to authenticate itself with its TLS certificate

We now want to instruct our Node.js server to identify itself using the certificate issued in the last step and to force clients to connect over TLS.

In your https server, specify the locations of the server's certificate and private key.

const fs = require('fs'); const https = require('https'); https .createServer( { // ... cert: fs.readFileSync('server.crt'), key: fs.readFileSync('server.key') // ... }, (req, res) => { res.writeHead(200); res.end('Hello, world!'); } ) .listen(9443);

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Configure Node.js to require clients to authenticate with a certificate issued by your CA

To tell Node.js to use mutual TLS and not just one-way TLS, we must instruct it to require client authentication to ensure clients present a certificate from our CA when they connect.

In your https server, specify the location of your CA root certificate to use for authenticating client certificates.

In this case, we instruct our server to request client certificates, but not to reject unauthorized requests so that we can check for authorization later and provide a friendly message on client authentication failures.

const fs = require('fs'); const https = require('https'); https .createServer( { // ... requestCert: true, rejectUnauthorized: false, ca: fs.readFileSync('ca.crt'), // ... }, (req, res) => { if (!req.client.authorized) { res.writeHead(401); return res.end('Invalid client certificate authentication.'); } res.writeHead(200); res.end('Hello, world!'); } ) .listen(9443);

That's it! Node.js should now be able to receive TLS connections from clients who authenticate themselves using a certificate issued by your trusted CA.

Create a private key and request a certificate for your Nginx (Reverse Proxy) client

Request a new certificate from your CA to represent your Nginx (Reverse Proxy) client.

$ step ca certificate "myuser" client.crt client.key

Your certificate and private key will be saved in client.crt and client.key respectively.

Make a request from Nginx (Reverse Proxy) using mutual TLS

Now, we need only to configure our Nginx (Reverse Proxy) client to make authenticated requests using our certificate and private key. The CA root certificate will be used to verify that the client can trust the certificate presented by the server.

Configure your upstream location to use a certificate for TLS communication when it proxies traffic to the backend. We'll specify the TLS protocol and some preferred ciphers:

location /upstream { proxy_pass https://myserver.internal.net:9443; proxy_ssl_certificate client.crt; proxy_ssl_certificate_key client.key; proxy_ssl_protocols TLSv1.2 TLSv1.3; proxy_ssl_ciphers HIGH:!aNULL:!MD5; # ... }

Further, configure your Nginx proxy to verify the server using your CA root certificate along with a verification depth for the server's certificate chain:

location /upstream { # ... proxy_ssl_trusted_certificate /etc/nginx/ca.crt; proxy_ssl_verify on; proxy_ssl_verify_depth 2; # ... }

All documentation content from the Hello mTLS project is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0).

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