#!/bin/bash

# The name of the main external interface.
EX_IF="eth0"
# The name of the VM-Private network interface.
VM_IF="eth1"

# Disable ICMP redirects.
# Note: Redirects are used when a router believes a packet is being routed sub optimally and it would like to inform
# the sending host that it should forward subsequent packets to that same destination through a different gateway.
echo 0 >"/proc/sys/net/ipv4/conf/$EX_IF/accept_redirects"
echo 0 >"/proc/sys/net/ipv6/conf/$EX_IF/accept_redirects"
echo 0 >"/proc/sys/net/ipv4/conf/$EX_IF/send_redirects"

# Flush old rules.
iptables -F
ip6tables -F
iptables -t nat -F
ip6tables -t nat -F
iptables -t mangle -F
ip6tables -t mangle -F

# Delete any custom chains.
iptables -X
ip6tables -X
iptables -t nat -X
ip6tables -t nat -X
iptables -t mangle -X
ip6tables -t mangle -X

# Drop invalid packets on all interfaces.
iptables -A INPUT -m conntrack --ctstate INVALID -j DROP
ip6tables -A INPUT -m conntrack --ctstate INVALID -j DROP

# Drop unroutable IPs on the external interface.
iptables -A INPUT -i "$EX_IF" -s 127.0.0.0/8 -j DROP
ip6tables -A INPUT -i "$EX_IF" -s ::1/128 -j DROP
iptables -A INPUT -i "$EX_IF" -s 10.0.0.0/8 -j DROP
iptables -A INPUT -i "$EX_IF" -s 172.16.0.0/12 -j DROP
iptables -A INPUT -i "$EX_IF" -s 192.168.0.0/16 -j DROP

# Allow all loopback traffic.
iptables -A INPUT -i lo -j ACCEPT
ip6tables -A INPUT -i lo -j ACCEPT

# Allow all VM-Private network traffic.
iptables -A INPUT -i "$VM_IF" -j ACCEPT
ip6tables -A INPUT -i "$VM_IF" -j ACCEPT

# Allow unrestricted access from our IPs.
iptables -A INPUT -i "$EX_IF" -m iprange --src-range 91.109.244.7-91.109.244.11 -j ACCEPT
iptables -A INPUT -i "$EX_IF" -m iprange --src-range 91.109.244.78-91.109.244.79 -j ACCEPT
iptables -A INPUT -i "$EX_IF" -m iprange --src-range 91.109.244.239-91.109.244.243 -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -s 2a02:2498:1:227::/64 -j ACCEPT
iptables -A INPUT -i "$EX_IF" -s 185.176.90.169 -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -s 2a07:4580:b0d:57f::/64 -j ACCEPT

# Allow packets of established connections and those related to them.
iptables -A INPUT -i "$EX_IF" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

# Allow pings, but ratelimited.
iptables -A INPUT -i "$EX_IF" -p icmp --icmp-type echo-request -m limit --limit 1/sec --limit-burst 5 -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type echo-request -m limit --limit 1/sec --limit-burst 5 -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p icmp --icmp-type echo-reply -m limit --limit 1/sec --limit-burst 5 -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type echo-reply -m limit --limit 1/sec --limit-burst 5 -j ACCEPT

# Allow certain types of ICMP informational packets.
iptables -A INPUT -i "$EX_IF" -p icmp --icmp-type destination-unreachable -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type destination-unreachable -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p icmp --icmp-type time-exceeded -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type time-exceeded -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p icmp --icmp-type parameter-problem -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type parameter-problem -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type packet-too-big -j ACCEPT

# Always allow SSH.
# Note: We never want to be locked out of the system, so also accept on the standard ssh port, just in case things accidently get
# set back to defaults.  Any connections to the standard port will just get a 'connection refused' message, unless this happens.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 22,9922 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 22,9922 -m conntrack --ctstate NEW -j ACCEPT

# Service: DNS.
iptables -A INPUT -i "$EX_IF" -p tcp --syn --dport 53 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn --dport 53 -m conntrack --ctstate NEW -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p udp --dport 53 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p udp --dport 53 -m conntrack --ctstate NEW -j ACCEPT

# Service: HTTP{,S}.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 80,443 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 80,443 -m conntrack --ctstate NEW -j ACCEPT

# Service: FTP{,S}.
# Note: This is a very permissive configuration - it leaves the high ports completely open.  To close it down,
# change the last two rules to "ESTABLISHED,RELATED" state; but this will prevent ftps passive from working.
modprobe nf_conntrack_ftp
echo 1 >/proc/sys/net/netfilter/nf_conntrack_helper	# Required to allow nf_conntrack_ftp to actually work.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 21,990 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 21,990 -m conntrack --ctstate NEW -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 20,989 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 20,989 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p tcp -m multiport --dports 49152:65534 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -m multiport --dports 49152:65534 -m conntrack --ctstate NEW -j ACCEPT

# Service: rsync.
iptables -A INPUT -i "$EX_IF" -p tcp --syn --dport 873 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn --dport 873 -m conntrack --ctstate NEW -j ACCEPT

# Service: SMTP and submission.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 25,587 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 25,587 -m conntrack --ctstate NEW -j ACCEPT

# Service: IMAP{,S}.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 143,993 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 143,993 -m conntrack --ctstate NEW -j ACCEPT

# Service: POP3{,S}.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 110,995 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 110,995 -m conntrack --ctstate NEW -j ACCEPT

# Service: Bittorrent.
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 6881:6899 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 6881:6899 -m conntrack --ctstate NEW -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p udp -m multiport --dports 6881:6899 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p udp -m multiport --dports 6881:6899 -m conntrack --ctstate NEW -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 49152:65534 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp --syn -m multiport --dports 49152:65534 -m conntrack --ctstate NEW -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p udp -m multiport --dports 49152:65534 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p udp -m multiport --dports 49152:65534 -m conntrack --ctstate NEW -j ACCEPT

# Set default policies.
iptables -P INPUT DROP
ip6tables -P INPUT DROP
iptables -P OUTPUT ACCEPT		# We don't firewall outgoing connections.
ip6tables -P OUTPUT ACCEPT		# We don't firewall outgoing connections.
iptables -P FORWARD DROP
ip6tables -P FORWARD DROP