firewall.sh

#!/bin/sh

# remove all current rules
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X

# drop all incoming traffic by default
iptables -P INPUT DROP
iptables -P FORWARD DROP

# accept all outgoing traffic
iptables -P OUTPUT ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# accept all loopback traffic
iptables -A INPUT -i lo -j ACCEPT

# accept SSH, HTTP, and HTTPS
iptables -A INPUT -p tcp -m multiport --dports 22,80,443,8080,8443 -j ACCEPT
iptables -A OUTPUT -p tcp -m multiport --sports 22,80,443,8080,8443 -j ACCEPT

# redirect 80 and 443 to 8080 and 8443, respectively
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 8443