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bootstrap/rc.d/rc.firewall-float

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#!/bin/bash
# Version: 0.2.1
# Copyright (c) 2022:
# Darren 'Tadgy' Austin <darren (at) afterdark.org.uk>
# Licensed under the terms of the GNU General Public License version 3.
# The name of the main external interface.
EX_IF="eth0"
# IP addresses.
PRIMARYIP=""
PRIMARYIP6=""
FLOATINGIP=""
FLOATINGIP6=""
# The IP ranges from where to accept unfiltered connections
# |-- UK Servers --| |---------------------------------- UK2 -----------------------------------| |-- Linode ---| |- L'Servers --| |----- Home -----|
UNFILTERED_RANGES_V4=('5.101.171.210/28' '91.109.244.7' '91.109.244.8' '91.109.244.9' '91.109.244.10' '91.109.244.11' '88.80.191.137' '185.176.90.169' 'afterdark.org.uk')
# |---- UK Servers -----| |------- UK2 --------| |----------- Linode -----------| |---- LoveServers -----|
UNFILTERED_RANGES_V6=('2a01:a500:2981:1::/64' '2a02:2498:1:227::/64' '2a01:7e00::f03c:93ff:fe86:afae' '2a07:4580:b0d:57f::169')
start_firewall() {
# 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 "$EX_IF" -s ::1/128 -j DROP
# Allow local nets if our IP is in the same range.
if [[ "$(ip -br a s "$EX_IF" | awk -e '{printf $3}' | cut -d. -f1)" == "10" ]]; then
iptables -A INPUT -i "$EX_IF" -s 10.0.0.0/8 -j ACCEPT
else
iptables -A INPUT -i "$EX_IF" -s 10.0.0.0/8 -j DROP
fi
if [[ "$(ip -br a s "$EX_IF" | awk -e '{printf $3}' | cut -d. -f1,2)" == "172.16" ]]; then
iptables -A INPUT -i "$EX_IF" -s 172.16.0.0/12 -j ACCEPT
else
iptables -A INPUT -i "$EX_IF" -s 172.16.0.0/12 -j DROP
fi
if [[ "$(ip -br a s "$EX_IF" | awk -e '{printf $3}' | cut -d. -f1,2)" == "192.168" ]]; then
iptables -A INPUT -i "$EX_IF" -s 192.168.0.0/16 -j ACCEPT
else
iptables -A INPUT -i "$EX_IF" -s 192.168.0.0/16 -j DROP
fi
# Allow all loopback traffic.
iptables -A INPUT -i lo -j ACCEPT
ip6tables -A INPUT -i lo -j ACCEPT
# Allow unrestricted access from our IPs.
for ENTRY in "${UNFILTERED_RANGES_V4[@]}"; do
iptables -A INPUT -i "$EX_IF" -s "$ENTRY" -j ACCEPT
done
for ENTRY in "${UNFILTERED_RANGES_V6[@]}"; do
ip6tables -A INPUT -i "$EX_IF" -s "$ENTRY" -j ACCEPT
done
# Allow packets of established connections and those related to them.
iptables -A INPUT -i "$EX_IF" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
# Allow pings.
iptables -A INPUT -i "$EX_IF" -p icmp -m icmp --icmp-type echo-request -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type echo-request -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p icmp --icmp-type echo-reply -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type echo-reply -j ACCEPT
# Allow certain types of ICMP informational packets.
iptables -A INPUT -i "$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
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type neighbour-solicitation -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p icmpv6 --icmpv6-type neighbour-advertisement -j ACCEPT
# Allow SSH.
iptables -A INPUT -i "$EX_IF" -p tcp -d "$PRIMARYIP" --syn -m multiport --dports 22,9922 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$PRIMARYIP6" --syn -m multiport --dports 22,9922 -m conntrack --ctstate NEW -j ACCEPT
# Service: HTTP{,S}.
iptables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP" --syn -m multiport --dports 80,443 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP6" --syn -m multiport --dports 80,443 -m conntrack --ctstate NEW -j ACCEPT
# Service: FTP.
iptables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP" --syn --dport 21 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP6" --syn --dport 21 -m conntrack --ctstate NEW -j ACCEPT
iptables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP" --syn --dport 20 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP6" --syn --dport 20 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
# Service: rsync.
iptables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP" --syn --dport 873 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$FLOATINGIP6" --syn --dport 873 -m conntrack --ctstate NEW -j ACCEPT
# Service: IMAP{,S}.
iptables -A INPUT -i "$EX_IF" -p tcp -d "$PRIMARYIP" --syn -m multiport --dports 143,993 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$PRIMARYIP6" --syn -m multiport --dports 143,993 -m conntrack --ctstate NEW -j ACCEPT
# Service: POP3{,S}.
iptables -A INPUT -i "$EX_IF" -p tcp -d "$PRIMARYIP" --syn -m multiport --dports 110,995 -m conntrack --ctstate NEW -j ACCEPT
ip6tables -A INPUT -i "$EX_IF" -p tcp -d "$PRIMARYIP6" --syn -m multiport --dports 110,995 -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
}
stop_firewall() {
# Set default policies to ACCEPT.
iptables -P INPUT ACCEPT
ip6tables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
ip6tables -P OUTPUT ACCEPT
iptables -P FORWARD ACCEPT
ip6tables -P FORWARD ACCEPT
# Flush 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
# Reset ICMP redirects.
cat /proc/sys/net/ipv4/conf/default/accept_redirects >"/proc/sys/net/ipv4/conf/$EX_IF/accept_redirects"
cat /proc/sys/net/ipv6/conf/default/accept_redirects >"/proc/sys/net/ipv6/conf/$EX_IF/accept_redirects"
cat /proc/sys/net/ipv4/conf/default/send_redirects >"/proc/sys/net/ipv4/conf/$EX_IF/send_redirects"
}
case "$1" in
'start')
start_firewall
;;
'stop')
stop_firewall
;;
'restart')
stop_firewall
sleep 0.5
start_firewall
;;
*)
echo "Usage: ${BASH_SOURCE[0]} <start|stop|restart>" >&2
exit 1
;;
esac
# Restart fail2ban to re-create the ban chains.
[[ -x /etc/rc.d/rc.fail2ban ]] && /etc/rc.d/rc.fail2ban restart >/dev/null
exit 0
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