How to install a letsencrypt cert with nginx?

Question

I've used letsencrypt to install an SSL cert for the latest nginx on ubuntu. The setup is fine and works great with the exception of:

I don't know enough about SSL to know what's going on but I have a suspicion: I installed the SSL cert for Apache a while back and just now moved to Nginx for it's http/2 support. As the nginx plugin is not stable yet I had to install the cert myself and this is what I did:

In my nginx config (/etc/nginx/conf/default.conf) I added:

server {
    listen       80;
    server_name  [domain];
    return 301   https://$host$request_uri;
}

server {
    listen       443 http2;
    listen       [::]:443 http2;
    server_name  [domain];

    ssl on;
    ssl_certificate /etc/letsencrypt/live/[domain]/cert.pem;
    ssl_certificate_key /etc/letsencrypt/live/[domain]/privkey.pem;
}

Is it possible that this breaks the chain somehow? What is the proper way here?

Thanks guys

Answer 1

1) For strong Diffie-Hellman and avoid Logjam attacks see this great manual.

You need extend your nginx config with these directives (after you will generate dhparams.pem file):

ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA';
ssl_prefer_server_ciphers on;
ssl_dhparam /etc/nginx/ssl/dhparams.pem;

2) For correct certificate chain use fullchain.pem, not cert.pem, see this great tutorial for details.

And you will get A grade :)

3) and as bonus try this great service:

"Generate Mozilla Security Recommended Web Server Configuration Files".