Set up ssl proxy with nginx and letsencrypt (https://secure.example.com => http://example.com)

iptables.rules

# https://wiki.debian.org/iptables

*filter

# Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
-A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT

# Accepts all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allows all outbound traffic
# You could modify this to only allow certain traffic
-A OUTPUT -j ACCEPT

# Allows HTTP and HTTPS connections from anywhere (the normal ports for websites)
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT

# Allows SSH connections 
# The --dport number is the same as in /etc/ssh/sshd_config
-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT

# Now you should read up on iptables rules and consider whether ssh access 
# for everyone is really desired. Most likely you will only allow access from certain IPs.

# Allow ping
#  note that blocking other types of icmp packets is considered a bad idea by some
#  remove -m icmp --icmp-type 8 from this line to allow all kinds of icmp:
#  https://security.stackexchange.com/questions/22711
-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT

# log iptables denied calls (access via 'dmesg' command)
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7

# Reject all other inbound - default deny unless explicitly allowed policy:
-A INPUT -j REJECT
-A FORWARD -j REJECT

COMMIT

nginx-config.conf

# SSL server config
server {
        listen 443 ssl;

        server_name secure.example.com;

        ssl_certificate /etc/letsencrypt/live/secure.example.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/secure.example.com/privkey.pem;
        
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_prefer_server_ciphers on;
        ssl_dhparam /etc/ssl/certs/dhparam.pem;
        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_session_timeout 1d;
        ssl_session_cache shared:SSL:50m;
        ssl_stapling on;
        ssl_stapling_verify on;
        add_header Strict-Transport-Security max-age=15768000;
        
        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 $scheme;

                proxy_pass          http://example.com;
                proxy_read_timeout  90;
        }
}

# Redirect http to https
server {
    listen 80;
    server_name example.com www.example.com;
    return 301 https://$host$request_uri;
}

setup.sh

# Update & upgrade
sudo apt-get update
sudo apt-get upgrade

# Install & start nginx
sudo apt-get install nginx -y
sudo service nginx start

# Install git
sudo apt-get install git -y

# Install letsencrypt
sudo git clone https://github.com/letsencrypt/letsencrypt /opt/letsencrypt

# Install letsencrypt dependencies
sudo /opt/letsencrypt-auto --help all

# Stop nginx (port 80 needed by letsencrypt)
sudo nginx service stop

# Generate certificate
sudo /opt/letsencrypt-auto certonly --rsa-key-size 4096

# Generate a strong Diffie-Hellman (2048-bit) group
sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048

# Config nginx to use certificate (see nginx-config.conf)
sudo vim /etc/nginx/sites-available/default

# Restart nginx
sudo service nginx start

# Test SSL config with https://www.ssllabs.com/ssltest/

# Configure iptables (see iptables.rules) & persist rules
sudo vim /etc/iptables.test.rules
sudo iptables-restore < /etc/iptables.test.rules
sudo iptables -L
sudo apt-get install iptables-persistent -y

# Configure SSL certificate renew with letsencrypt & cron
# /opt/letsencrypt/letsencrypt-auto renew
sudo crontab -e

# Add to crontab (to auto renew certs every monday)
# 30 2 * * 1 /opt/letsencrypt/letsencrypt-auto renew >> /var/log/le-renew.log
# 35 2 * * 1 /etc/init.d/nginx reload

# Sources
# - https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-14-04
# - https://www.digitalocean.com/community/tutorials/how-to-configure-nginx-with-ssl-as-a-reverse-proxy-for-jenkins