Thomas Fuchs
Hi, I'm Thomas Fuchs. I'm the author of Zepto.js, of script.aculo.us, and I'm a Ruby on Rails core alumnus. With Amy Hoy I'm building cheerful software, like Freckle Time Tracking and Every Time Zone and write books like Retinafy.me.
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How to get an A+ on the Qualsys SSL Labs test

April 4th, 2014

Recently we upgraded our server infrastructure for Freckle Time Tracking and in the process wanted to improve how we serve SSL.

If you don’t know much about this, it’s fine—there’s a few simple steps you can take to make your website more secure and faster loading in the process. _Important: of course, there’s no absolute security, and I make no claim that what I describe here is secure and will work for you. Use it at your own risk._

Long story short, you’ll want to get an A+ rating on the Qualsys SSL Labs test.

For that you’ll need to do the following:

  • Don’t support older protocols. A lot of servers support really old and obsolete protocols. If you run a web app, your users will very likely not need support for these.
  • Don’t support flawed SSL ciphers. There’s a bunch of these and you can avoid using them. Browsers support multiple different ciphers, so this is not a problem.
  • Cache SSL sessions. This will improve performance.
  • Turn on HTTP Strict Transport Security (HSTS). This is a special header that will tell browsers to never connect to the server via normal HTTP.

And that’s it. In order so you don’t need to research the proper settings, here’s how this looks like in form of an nginx configuration:

server {
  # deferred allows for faster connections if there's
  # no other servers on port 443 defined
  listen 443 ssl spdy deferred;

  ssl on;
  ssl_certificate /etc/nginx/your-certificate.crt;
  ssl_certificate_key /etc/nginx/your-private-key.key;

  ssl_prefer_server_ciphers on;
  ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2;
  ssl_ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS:!AES256;
  ssl_session_cache shared:SSL:10m;
  ssl_session_timeout 10m;
  ssl_stapling on;

  # tell any upstream things like unicorns that we're on https
  proxy_set_header X-Forwarded-Proto 'https';
  underscores_in_headers on;

  location / {
    add_header Strict-Transport-Security "max-age=31536000; includeSubdomains";
    # ...
  }

  # ...
}

And that’s it. Have fun with your new A+ rating on the SSL labs test.