How to get a perfect SSL Labs score

It is easy to get an A+ on your website. But it is a little bit hard to make a 4 parts, Certificate, Protocol Support, Key Exchange, and Cipher Strength, to be 100%.

Most of time, I got A+ rating of my site. For individual scores, the last two are 90%.

Let me break down.

Certificate

It is preaty easy to get 100% here.

  • Make sure your certificate and intermediate certificate and CA are in the correct order.
  • Don’t use SHA1 for the signature algorithm. Use SHA256 instead. Actually all main CA are using SHA256 now.
  • Use a trusted CA. Do not use WoSign, StartCom.

Protocol Support

  • SSL 2.0 0%
  • SSL 3.0 80%
  • TLS 1.0 90%
  • TLS 1.1 95%
  • TLS 1.2 100%

So it is best to just use TLS 1.2.

 

Key Exchange

Make a strong DHE (Ephemeral Diffie-Hellman) paramaaters.

openssldhparam -out /etc/nginx/ssl/dhparam.pem 4096

It is not enough. Add following into Nginx settings.

ssl_ecdh_curve secp384r1;

Cipher Strength

  • 0 bits (no encryption) 0%
  • < 128 bits (e.g., 40, 56) 20%
  • < 256 bits (e.g., 128, 168) 80%
  • >= 256 bits (e.g., 256) 100%

So I just use 256 bit cipher suites.

 

Here is a test site, I tried it today, 2018-08-11. It is A+ with four 100% scores.

Here is the most important part of Nginx config file. I put them all together.

ssl_certificate /etc/nginx/ssl/whovpn.com/fullchain;
ssl_certificate_key /etc/nginx/ssl/whovpn.com/key;
ssl_session_timeout 10m;
ssl_session_cache shared:SSL:10m;
ssl_session_tickets off;

ssl_dhparam /etc/nginx/ssl/dhparam.pem;

# modern configuration. tweak to your needs.
ssl_protocols TLSv1.2;
ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES256-SHA384';
ssl_prefer_server_ciphers on;

ssl_ecdh_curve secp384r1;

# HSTS (ngx_http_headers_module is required) (15768000 seconds = 6 months)
add_header Strict-Transport-Security max-age=15768000;

# OCSP Stapling ---
# fetch OCSP records from URL in ssl_certificate and cache them
ssl_stapling on;
ssl_stapling_verify on;

 

## verify chain of trust of OCSP response using Root CA and Intermediate certs
ssl_trusted_certificate /etc/nginx/ssl/whovpn.com/fullchain;

resolver 8.8.8.8;