Configure the server to act as a forwarder for port 80/443 While only allowing traffic from Cloudflare IPs

readme.md

Purpose:

Helps facilitate the ability to run internet facing web apps on a homelab ($desinationip) without exposing the homelab's IP address and forcing the use of CloudFlare for incoming traffic. Tunnels both incoming web traffic and outgoing traffic. Uses public cloud VPS ($serverip) as the reverse proxy and VPN.

This setup should hide the homelab's IP even in the event of compromise, end-to-end encrypt all web traffic between CloudFlare and the homelab, and prevents the proxy server from being accessed directly.

Internet --> Cloudflare (80/443) --> Cloud Provider (cloudflare-reverse-proxy.sh) --> Homelab (port forward + nginx-proxy-manager)

Homelab (all traffic) --> Cloud Provider (OpenVPN on 4443) --> Internet

• If Homelab's IP is discovered, it will only accept traffic from the proxy server, directed at a specific domain, and that traffic will only hit the web apps if it is properly encrypted from CloudFlare.
• If the proxy's IP is discovered, it will only accept incoming connections from HomeLab's IP on port 4443 and a managment IP on port 22. Additonally traffic sent to 80/443 will only be forwarded to the homelab if it's from CloudFlare.
• If the Homelab web app is pwnd, all outbound connections will be forced through the proxy, hiding the homelab's location.

Prerequisites:

• Setup $serverip OpenVPN server on port 4443
• Setup VM's running on $destinationip to connect to $serverip OpenVPN (ideally using pfsense with killswitch). This should prevent accidental IP disclosure.
• Setup $destinationip port 80/443 forwarding to nginx-proxy-manager, only allow from $serverip
• Setup $destinationip nginx-proxy-manager domains and only allow access from $serverip, import Cloudflare SSL origin certs.
• Setup cloudflare domains and point to $serverip, enable proxying and "Full Strict SSL".
• Run the script wget https://gist.githubusercontent.com/GlitchWitch/207d18c8902fcb5e1c5f0e043f8e9101/raw/862bf56e2fe02e09f3dec22a218824990bb18079/cloudflare-reverse-proxy.sh && bash cloudflare-reverse-proxy.sh desinationip managmentip && rm cloudflare-reverse-proxy.sh

This script should do the following assuming I didn't fuck it up:

• Blocks all incoming SSH traffic on $serverip
• Whitelists $managmentip to access SSH port on $serverip
• Blocks all web (80/443) traffic on $serverip
• Forwards all web traffic (80/443) on on $serverip to $destinationip only if received from cloudflare
• Whitelist $destinationip to access OpenVPN on $serverip

cloudflare-reverse-proxy.sh

# !/bin/bash
#
# Configure server to act as a reverse proxy for port 80/443 and only allow Cloudflare IPs
# Usage: bash cloudflare-reverse-proxy.sh destinationip managmentip

# Clear existing iptables

iptables -F

# Forward traffic from Cloudflare
for i in `curl https://www.cloudflare.com/ips-v4`; do
iptables -t nat -A PREROUTING -s $i -p tcp --dport 80 -j DNAT --to-destination $1:80;
done
for i in `curl https://www.cloudflare.com/ips-v4`; do
      iptables -t nat -A PREROUTING -s $i -p tcp --dport 443 -j DNAT --to-destination $1:443;
done

# Block all other web traffic
iptables -A INPUT -p tcp -s 0.0.0.0/0 --dport 80 -j DROP
iptables -A INPUT -p tcp -s 0.0.0.0/0 --dport 443 -j DROP

# Block SSH Traffic not from our Managment IP
iptables -I INPUT -p tcp -s $2 --dport 22 -j ACCEPT
iptables -A INPUT -p tcp -s 0.0.0.0/0 --dport 22 -j DROP

# Allow access to OpenVPN
iptables -I INPUT -p tcp -s $1 --dport 4443 -j ACCEPT
iptables -A INPUT -p tcp -s 0.0.0.0/0 --dport 4443 -j DROP
iptables -I INPUT -p udp -s $1 --dport 4443 -j ACCEPT
iptables -A INPUT -p udp -s 0.0.0.0/0 --dport 4443 -j DROP

iptables -A FORWARD -i tun+ -j ACCEPT
iptables -A FORWARD -i tun+ -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i eth0 -o tun+ -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -s 10.8.0.1/24 -j ACCEPT


iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
iptables -A OUTPUT -o tun+ -j ACCEPT

# Enable IP Forwarding
sysctl net.ipv4.ip_forward=1
#iptables -t nat -A POSTROUTING -j MASQUERADE
iptables -t nat -A POSTROUTING -p tcp --dport 80 -j MASQUERADE
iptables -t nat -A POSTROUTING -p tcp --dport 443 -j MASQUERADE

thank you, Dear @GlitchWitch, I appreciate it