Simple Node script showing details of TLS client certificate without a fixed set of accepted CAs

index.js

// prerequisites:
// dependency installation:    npm i fs https express
// create server certificate:  openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 3650 -nodes -subj "/C=XX/ST=StateName/L=CityName/O=CompanyName/OU=CompanySectionName/CN=CommonNameOrHostname"

// point your browser to https://localhost:8443
// this should allow you to select a certificate to use as the client cert, if you have any
// the server then returns some details about that certificate

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

const app = express();

app.get('/', (req, res) => {
  let clientCertDetails = req.socket.getPeerCertificate()

  return res.send(
    "<pre>" +
    "Certificate Fingerprint: " + clientCertDetails.fingerprint + "<br/>" +
    "Certificate CN: " + clientCertDetails.subject.CN + "<br/>" +
    "</pre>"    
  );
});

https
  .createServer(
    {
      cert: fs.readFileSync('cert.pem'),
      key: fs.readFileSync('key.pem'),
      requestCert: true,
      rejectUnauthorized: false,
    },
    app
  )
  .listen(8443);