What is TLS and when to use it

Topic: Security basics

TLS (Transport Layer Security) encrypts and authenticates traffic between client and server. Use it for all HTTP, APIs, mail, and database connections that carry sensitive data. Use this when enabling HTTPS or securing any network service.

Intent: Decision

Quick answer

  • TLS provides confidentiality (encryption), integrity (tamper detection), and optional server (and client) authentication via certificates. Use TLS for any login, API, or data in transit.
  • Enable HTTPS (TLS on HTTP) for all web and API endpoints; use valid certificates (public CA or private CA with trust). Disable TLS 1.0 and 1.1; prefer TLS 1.2 or 1.3.
  • Certificates expire; set up renewal (e.g. Let's Encrypt, ACM) and alerts. For internal services use a private CA or mutual TLS so both sides are authenticated.

Prerequisites

Steps

  1. Use TLS for all sensitive traffic

    HTTP, APIs, database client connections, and mail should use TLS. Redirect HTTP to HTTPS; use HSTS so browsers do not fall back to plain. Do not send passwords or tokens over plain connections.

  2. Configure certificates

    Use a certificate from a public CA for public-facing sites (e.g. Let's Encrypt). For internal, use a private CA and distribute trust. Ensure certificate chain is complete and key is secure.

  3. Harden protocol and ciphers

    Disable TLS 1.0 and 1.1; use TLS 1.2 or 1.3. Prefer strong ciphers; disable NULL and weak ciphers. Run a scanner (e.g. testssl) to verify configuration.

  4. Renew and monitor

    Certificates expire; automate renewal (certbot, ACM). Alert on expiry and on protocol or cipher misconfigurations. For mutual TLS, protect client certificates like secrets.

Summary

TLS encrypts and authenticates traffic. Use it for all HTTP, APIs, and sensitive connections; use valid certificates and modern protocol versions. Automate renewal and monitor configuration.

Prerequisites

Steps

Step 1: Use TLS for all sensitive traffic

Enable HTTPS for web and API; use TLS for DB and mail. Redirect HTTP to HTTPS; do not send credentials over plain connections.

Step 2: Configure certificates

Use a public CA for public sites; use a private CA for internal. Ensure the full chain is served and the private key is protected.

Step 3: Harden protocol and ciphers

Use TLS 1.2 or 1.3; disable weak protocols and ciphers. Verify with a TLS scanner.

Step 4: Renew and monitor

Automate certificate renewal; set alerts for expiry and misconfiguration. Protect client certs like secrets.

Verification

All sensitive endpoints use TLS; certificates are valid and renew automatically; protocol and ciphers are hardened.

Troubleshooting

Certificate errors — Fix chain, expiry, or hostname mismatch. Legacy client — Prefer upgrading the client; if not possible, isolate and use a TLS terminator with strong config.

Next steps

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