Let's Encrypt on Nginx Setup

31 August 2016

Encryption is a thing now, 314, proliferated to the point that Google will downrank site which do not have it. I’ve never exactly cared who, if anyone, reads this site, but I thought I’d give Let’s Encrypt a try - if for no better reason than because I’d like to use HTTP2 on a web app I’m writing.

These notes are really for my benefit, though it might benefit you as well.

First, install Let’s Encrypt.

sudo apt install -y letsencrypt

For every domain, modify the virtual server definition to look like this:

sudo vim /etc/nginx/sites-available/mysteriouspants.com
  # a reflector domain that just redirects to www.,
  # and serves .well-known files
  server {
    listen 80;
    server_name mysteriouspants.com;
    access_log off;

    root /var/www/empty;

    location /.well-known {
      root /var/www/letsencrypt;
      try_files $uri /dev/null =404;
    }

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

  server {
    listen 443 ssl http2;
    server_name mysteriouspants.com;
    access_log off;

    ssl_certificate /etc/letsencrypt/live/mysteriouspants.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/mysteriouspants.com/privkey.pem;

    return 301 https://www.$host$request_uri;
  }
sudo vim /etc/nginx/sites-available/www.mysteriouspants.com
  server {
    listen 80;
    server_name www.mysteriouspants.com;
    access_log off;

    root /var/www/empty;

    location /.well-known {
      root /var/www/letsencrypt;
      try_files $uri /dev/null =404;
    }

    location / {
      return 301 https://$host$request_uri;
    }
  }

  server {
    listen 443 ssl http2;
    server_name www.mysteriouspants.com;
    access_log off;

    ssl_certificate /etc/letsencrypt/live/mysteriouspants.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/mysteriouspants.com/privkey.pem;

    root /var/www/www.mysteriouspants.com;
  }
sudo service nginx reload

Make some directories. The empty directory in particular is for the root of the redirection mirrors.

sudo mkdir /var/www/empty
sudo mkdir /var/www/letsencrypt

Actually grab your first SSL certificate. It will ask you to accept a EULA, then it will populate /var/www/letsencrypt with some challenge files. Their servers will ask your domains for those files to prove that you control the domains - so they’re not just handing out certificates willy-nilly.

sudo letsencrypt certonly --webroot -w /var/www/letsencrypt \
  -d mysteriouspants.com \
  -d www.mysteriouspants.com

This command should complete with no errors, if it does, your Nginx configuration is likely messed up.

At this point, your web pages are actually SSL’d now that your SSL certificates exist. Harden up your Nginx server by adding this set of ciphers I totally didn’t just pull off some webpage.

sudo vim /etc/nginx/nginx.conf
  ssl_ciphers EECDH+CHACHA20:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;

Finally, Let’s Encrypt certificates are only good for 90 days, so it’s best to renew them. They suggest twice a day, which is super easy to do via a simple cron task.

sudo vim /etc/cron.d/letencrypt
  0 0,12 * * * * letsencrypt renew

And there you have it.