Tls Configuration

TLS configuration

A TLS setup that merely shows a padlock can still allow downgrade to a broken cipher, serve a certificate that expired overnight, or let a browser fall back to plaintext on the next visit. The job is to pin the protocol floor, keep certificates fresh without a human in the loop, and make the browser refuse anything but HTTPS after the first contact.

Method

1. Disable everything below TLS 1.2. Turn off SSLv3, TLS 1.0, and TLS 1.1 explicitly. In nginx set ssl_protocols TLSv1.2 TLSv1.3;. Prefer 1.3 where the client base allows it: it drops RSA key exchange and static ciphers by design, so the negotiation surface shrinks on its own.
2. Choose the cipher list from a maintained source, not memory. Paste the Mozilla SSL Configuration Generator "intermediate" profile for your server and version rather than handpicking suites. Set ssl_prefer_server_ciphers off for 1.3, and keep only forward-secret ECDHE suites on 1.2.
3. Automate issuance and renewal with ACME. Run certbot or acme.sh, or let Caddy and Traefik handle it inline. Renew at 30 days remaining, not at expiry, and reload the server after the hook installs the new cert. Never let a renewal depend on someone reading a calendar reminder.
4. Send HSTS only once the whole origin is HTTPS. Add Strict-Transport-Security: max-age=31536000; includeSubDomains. Ramp max-age up from a few hours while you confirm nothing still needs plaintext, because the browser will honor a bad value for its full life.
5. Add preload deliberately, then submit to hstspreload.org. Preload bakes the rule into the browser binary and is slow to reverse, so commit only when every subdomain, forever, will serve TLS.
6. Staple OCSP and serve the full chain. Enable ssl_stapling on; with a resolver so clients skip a revocation round-trip, and include intermediates in the chain file so mobile clients without the intermediate cached still validate.

Checks

• Does testssl.sh https://host or SSL Labs report grade A with no protocol or cipher warnings?
• Does openssl s_client -connect host:443 -tls1_1 fail to negotiate?
• Does the response carry an HSTS header with max-age at least 31536000 once the origin is fully migrated?
• Will the certificate renew and reload untouched if every operator is on vacation the week it expires?

Boundaries

This covers server and proxy configuration, not the certificate authority trust decisions your organization makes or mutual TLS between services, which carries its own key distribution problem. Where a managed load balancer or CDN terminates TLS, configure it there and confirm the origin leg is encrypted too rather than assuming the edge covers it.