How to setup Let's Encrypt for Nginx on Ubuntu 16.04 (including IPv6, HTTP/2 and A+ SLL rating)

There are two modes when you don't want Certbot to edit your configuration:

Standalone: replaces the webserver to respond to ACME challenges
Webroot: needs your webserver to serve challenges from a known folder.

Webroot is better because it doesn't need to replace Nginx (to bind to port 80) to renew certificates.

Nginx snippets

First we create two snippets to avoid duplicating code in every virtual host configuration.

Create a file /etc/nginx/snippets/letsencrypt.conf containing:

location ^~ /.well-known/acme-challenge/ {
	default_type "text/plain";
	root /var/www/letsencrypt;
}

Create a file /etc/nginx/snippets/ssl.conf containing:

ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_session_tickets off;

ssl_dhparam /etc/ssl/private/dhparams_2048.pem;
ssl_protocols TLSv1.2;
ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256';

ssl_prefer_server_ciphers on;
add_header Strict-Transport-Security max-age=15768000;
ssl_stapling on;
ssl_stapling_verify on;

The SSL config is based on Mozilla's Modern profile: oldest compatible clients are Firefox 27, Chrome 30, IE 11 on Windows 7, Edge, Opera 17, Safari 9, Android 5.0, and Java 8.

Nginx virtual hosts (HTTP-only)

We don't have a certificate yet at this point, so the domain is served only as HTTP.

Create a file /etc/nginx/sites-available/mydomain.conf containing:

server {
	listen 80 default_server;
	listen [::]:80 default_server ipv6only=on;
	server_name mydomain.com www.mydomain.com;

	include /etc/nginx/snippets/letsencrypt.conf;

	root /var/www/mydomain;
	index index.html;
	location / {
		try_files $uri $uri/ =404;
	}
}

And reload Nginx:

sudo systemctl reload nginx

Note the line include /etc/nginx/snippets/letsencrypt.conf; that makes Nginx serve challenges for both http://www.mydomain.com/.well-known/acme-challenge/ and http://mydomain.com/.well-known/acme-challenge/.

Let's Encrypt client

Install the client:

sudo apt-get install letsencrypt

Create a folder for the challenges:

sudo mkdir -p /var/www/letsencrypt/.well-known/acme-challenge

Generate a Diffie-Hellman parameter for DHE ciphersuites:

sudo openssl dhparam -out /etc/ssl/private/dhparams_2048.pem 2048

And finally, get a certificate (don't forget to replace with your own email address):

letsencrypt certonly --webroot -w /var/www/letsencrypt -d www.domain.com -d domain.com --email [email protected] --agree-tos

It will save the files in /etc/letsencrypt/live/www.mydomain.com/.

Nginx virtual hosts (HTTPS-only)

Now that you have a certificate for the domain, switch to HTTPS by editing the file /etc/nginx/sites-available/mydomain.conf and replacing contents with:

server {
	listen 80 default_server;
	listen [::]:80 default_server ipv6only=on;
	server_name mydomain.com www.mydomain.com;
	
	include /etc/nginx/snippets/letsencrypt.conf;

	location / {
		return 301 https://www.mydomain.com$request_uri;
	}
}


server {
	server_name www.mydomain.com;
	listen 443 ssl http2 default_server;
	listen [::]:443 ssl http2 default_server ipv6only=on;
	
	ssl_certificate /etc/letsencrypt/live/www.mydomain.com/fullchain.pem;
	ssl_certificate_key /etc/letsencrypt/live/www.mydomain.com/privkey.pem;
	ssl_trusted_certificate /etc/letsencrypt/live/www.mydomain.com/fullchain.pem;
	include /etc/nginx/snippets/ssl.conf;
	
	root /var/www/mydomain.com;
	index index.html;
	location / {
		try_files $uri $uri/ =404;
	}
}


server {
	listen 443 ssl http2;
	listen [::]:443 ssl http2;
	server_name mydomain.com;

	ssl_certificate /etc/letsencrypt/live/www.mydomain.com/fullchain.pem;
	ssl_certificate_key /etc/letsencrypt/live/www.mydomain.com/privkey.pem;
	ssl_trusted_certificate /etc/letsencrypt/live/www.mydomain.com/fullchain.pem;
	include /etc/nginx/snippets/ssl.conf;

	location / {
		return 301 https://www.mydomain.com$request_uri;
	}
}

Then reload Nginx:

sudo systemctl reload nginx

Conclusion

You should now be able to see your website at https://www.mydomain.com. Congratulations 😃

You can test now also test that your domain has A+ SLL rating:

You can renew using letsencrypt renew: when called it will attempt to renew certificates expiring in less than 30 days, so you can put this command in cron to renew automatically.

If letsencrypt is useful to you, consider donating to the EFF.