map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

server {
    listen 80;
    listen [::]:80;
    server_name instance.example.com;
    location / { return 301 https://$host$request_uri; }
}

server {
    listen      443 ssl;
    listen [::]:443 ssl;
    server_name instance.example.com;

    # TLS
    ssl_protocols TLSv1.2;
    ssl_ciphers HIGH:!MEDIUM:!LOW:!aNULL:!NULL:!SHA;
    ssl_prefer_server_ciphers on;
    ssl_session_cache shared:SSL:10m;
    ssl_certificate     /etc/letsencrypt/live/instance.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/instance.example.com/privkey.pem;

    # Ciphers with intermediate compatibility
    # https://mozilla.github.io/server-side-tls/ssl-config-generator/?server=nginx-1.6.2&openssl=1.0.1t&hsts=yes&profile=intermediate
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    #ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS';
    # Follows the Web Security Directives from the Mozilla Dev Lab and the Mozilla Obervatory + Partners
    # https://wiki.mozilla.org/Security/Guidelines/Web_Security
    # https://observatory.mozilla.org/
    add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload";
    add_header Content-Security-Policy "upgrade-insecure-requests";
    add_header Content-Security-Policy-Report-Only "default-src https: data: 'unsafe-inline' 'unsafe-eval'";
    add_header X-Content-Type-Options nosniff;
    add_header X-XSS-Protection "1; mode=block";
    add_header X-Download-Options noopen;
    add_header X-Permitted-Cross-Domain-Policies none;
    add_header X-Frame-Options "SAMEORIGIN";

    gzip on;
    gzip_disable "msie6";
    gzip_vary on;
    gzip_proxied any;
    gzip_comp_level 6;
    gzip_buffers 16 8k;
    gzip_http_version 1.1;
    gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

    # HSTS
    add_header Strict-Transport-Security "max-age=31536000";

    location / {
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto https;
        proxy_pass_header Server;

        proxy_pass  http://private_ip:80;

    proxy_buffering off;
        proxy_redirect off;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        tcp_nodelay on;
    }
}