#!/usr/bin/env bash

# Clears the old iptables rules and sets new ones to only allow SSH & I2NP traffic (+ ICMP pings)


sudo apt update && sudo apt install iptables iptables-persistent -y

read -p "[?] Confirm the deletion of old iptables rules: " -n 1 -r
! [[ "$REPLY" =~ ^[Yy]$ ]] && echo -e "\n[!] Aborting..." && exit 0

! [ -f ".env" ] && echo "[!] The .env file not found, aborting..." && exit 1

set -a
source .env
set +a

[ -z ${EXT_PORT} ] && echo "[!] EXT_PORT is not configured, aborting..." && exit 1

# Clear all old rules (IPv4)
sudo iptables -P INPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables -P OUTPUT ACCEPT
sudo iptables -t nat -F
sudo iptables -t mangle -F
sudo iptables -F
sudo iptables -X

# Clear all old rules (IPv6)
sudo ip6tables -P INPUT ACCEPT
sudo ip6tables -P FORWARD ACCEPT
sudo ip6tables -P OUTPUT ACCEPT
sudo ip6tables -t nat -F
sudo ip6tables -t mangle -F
sudo ip6tables -F
sudo ip6tables -X

# Allow all incoming SSH traffic (tcp:22)
sudo iptables -A INPUT -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT
sudo ip6tables -A INPUT -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

# Allow all I2NP traffic (tcp:$EXT_PORT, udp:$EXT_PORT)
# Not using `--state NEW,ESTABLISHED` guarantees that **all** incoming and outgoing traffic is let through
sudo iptables -A INPUT -p tcp --dport $EXT_PORT -j ACCEPT
sudo ip6tables -A INPUT -p tcp --dport $EXT_PORT -j ACCEPT
sudo iptables -A INPUT -p udp --dport $EXT_PORT -j ACCEPT
sudo ip6tables -A INPUT -p udp --dport $EXT_PORT -j ACCEPT

# Allow all incoming ICMP echo requests (pings)
sudo iptables -A INPUT -p icmp --icmp-type echo-request -m state --state NEW,ESTABLISHED -j ACCEPT

# Allow all ICMP traffic via IPv6 (ICMPv6 is essential for IPv6 to function)
sudo ip6tables -A INPUT -p ipv6-icmp -j ACCEPT

# Allow all related and established incoming traffic (i.e. allow responses to outgoing requests initiated by the local system)
sudo iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
sudo ip6tables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Reject all other incoming traffic with DROP (DROP doesn't provide information about 
# the host configuration to potential attackers like REJECT would, which is why it's used)
sudo iptables -A INPUT -j DROP
sudo ip6tables -A INPUT -j DROP

# Persist changes
sudo iptables-save | sudo tee /etc/iptables/rules.v4
sudo ip6tables-save | sudo tee /etc/iptables/rules.v6