Hands-On TLS: Inspect Certificates, Verify PFS, and Build a Local HTTPS Server

Source: Dev.to

TL;DR

Run three quick checks:

• Browser certificate
• openssl s_client
• DevTools mixed‑content scan

Use the Node.js example to experiment locally.

Look for:

• TLS 1.2 / TLS 1.3
• AEAD ciphers
• ECDHE for Perfect Forward Secrecy (PFS)

Minimal HTTPS Server (Node.js)

Save this as server.js. You’ll need key.pem and cert.pem (self‑signed is fine for local testing).

// server.js
const https = require('https');
const fs = require('fs');

const options = {
  key: fs.readFileSync('key.pem'),
  cert: fs.readFileSync('cert.pem')
};

https.createServer(options, (req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('secure chat placeholder\n');
}).listen(8443, () => {
  console.log('Listening on https://localhost:8443');
});

Create a Local Certificate (Testing Only)

openssl req -x509 -newkey rsa:2048 -nodes \
  -keyout key.pem \
  -out cert.pem \
  -days 365 \
  -subj "/C=IN/ST=State/L=City/O=Org/CN=localhost"

Hit It

node server.js
curl -vkI https://localhost:8443 --insecure

Inspect a Production Certificate (OpenSSL)

openssl s_client -connect example.com:443 -servername example.com