firewall.sh

#!/bin/bash

PATH=/usr/sbin:/usr/bin:/sbin:/bin
SPECIAL_ADDRS='255.255.255.255/32 240.0.0.0/4 233.252.0.0/24 224.0.0.0/4 203.0.113.0/24 198.51.100.0/24 198.18.0.0/15 192.168.0.0/16 192.88.99.0/24 192.0.2.0/24 192.0.0.0/24 172.16.0.0/12 169.254.0.0/16 127.0.0.0/8 100.64.0.0/10 10.0.0.0/8 0.0.0.0/8'

# ---

[ $EUID != 0 ] && echo run as root && exit 1

# ---

id debian-tor || exit 2

# ---

iptables -F; iptables -t nat -F
iptables -P INPUT DROP; iptables -P FORWARD DROP; iptables -P OUTPUT DROP

# ---

iptables -A INPUT -m state --state INVALID -j DROP
iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -j DROP

# ---

iptables -A FORWARD -j DROP

# ---

iptables -A OUTPUT -m state --state INVALID -j DROP
iptables -A OUTPUT -m state --state ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p udp -d 127.0.0.1 --dport 9053 -j ACCEPT
iptables -A OUTPUT -p tcp -d 127.0.0.1 --dport 9040 --syn -j ACCEPT

iptables -A OUTPUT -p tcp -m owner --uid-owner debian-tor -m state --state NEW --syn -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT

for special_addr in $SPECIAL_ADDRS; do
  iptables -A OUTPUT -d $special_addr -j DROP
done

iptables -A OUTPUT -j DROP

# ---

iptables -t nat -A OUTPUT -p udp --dport 53 -j DNAT --to-destination='127.0.0.1:9053'
iptables -t nat -A OUTPUT -p tcp -d 10.192.0.0/10 --syn -j DNAT --to-destination='127.0.0.1:9040'

iptables -t nat -A OUTPUT -m owner --uid-owner debian-tor -j RETURN
iptables -t nat -A OUTPUT -o lo -j RETURN

for special_addr in $SPECIAL_ADDRS; do
  iptables -t nat -A OUTPUT -d $special_addr -j RETURN
done

iptables -t nat -A OUTPUT -p tcp --syn -j DNAT --to-destination='127.0.0.1:9040'

# ---

ip6tables -F; ip6tables -t nat -F
ip6tables -P INPUT DROP; ip6tables -P FORWARD DROP; ip6tables -P OUTPUT DROP
ip6tables -A INPUT -j DROP; ip6tables -A FORWARD -j DROP; ip6tables -A OUTPUT -j DROP

# ---

> /etc/hosts.allow
echo ALL:ALL > /etc/hosts.deny

# ---

chattr -i /etc/resolv.conf
{
  echo nameserver 127.0.0.1
} > /etc/resolv.conf && chattr +i /etc/resolv.conf

# ---

{
  echo DNSPort 127.0.0.1:9053
  echo AutomapHostsOnResolve 1
  echo AutomapHostsSuffixes .onion
  echo
  echo TransPort 127.0.0.1:9040
  echo VirtualAddrNetwork 10.192.0.0/10
} > /etc/tor/torrc && systemctl restart tor && echo tcp: ok, udp: ok, icmp: ok, webrtc: ng