O script a seguir está em shell e tem como objetivo configurar o firewall iptables, podendo ser modificado de acordo com suas necessidades.

Comandos do firewall:

Ativar:

# ./firewall
Ou:
# ./firewall --start

Desativar:

# ./firewall --stop

Reiniciar:

# ./firewall --restart

• Download script_firewall.sh
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Esconder código-fonte

#!/bin/bash

#######################################
# Script de Firewall
# Criado por: Thiago Nogueira
# Data de criação: 25/03/15
# Última modificação: 18/05/15
#######################################

### Variáveis ###
#INT="eth0"
EXT="ppp0"
#SUBNET="192.168.100.0/24"

################
# Função Help
################
function help(){
    echo -e "Para ativar o Firewall, adicione o parâmetro '--start'."
    echo -e "Para desativar, adicione '--stop'."
    echo -e "Para reiniciar, '--restart'."
    echo -e "Para obter ajuda, novamente, adicione o parâmetro '--help'."
}

################
# Função Stop
################
function stop(){
    ### Exclui todas as regras ###
    iptables -F
    iptables -t nat -F
    iptables -t mangle -F
    iptables -t filter -F

    ### Exclui cadeias customizadas ###
    iptables -X

    ### Zera os contadores das cadeias ###
    iptables -t nat -Z
    iptables -t mangle -Z
    iptables -t filter -Z

    ### Carrega os modulos ###
    modprobe iptable_nat
    modprobe iptable_filter
    modprobe iptable_mangle

    ### Políticas em ACCEPT ###
    iptables -P INPUT ACCEPT
    iptables -P OUTPUT ACCEPT
    iptables -P FORWARD ACCEPT
    # Ip6tables #
    ip6tables -P INPUT ACCEPT
    ip6tables -P FORWARD ACCEPT
    ip6tables -P OUTPUT ACCEPT

    ## Habilita roteamento ###
    echo 1 > /proc/sys/net/ipv4/ip_forward
    iptables -t nat -A POSTROUTING -o $EXT -j MASQUERADE
}

################
# Função Start
################
function start(){
    ### Exclui todas as regras ###
    iptables -t nat -F
    iptables -t mangle -F
    iptables -t filter -F

    ### Exclui cadeias customizadas ###
    iptables -X

    ### Zera os contadores das cadeias ###
    iptables -t nat -Z
    iptables -t mangle -Z
    iptables -t filter -Z

    ### Carrega os modulos ###
    modprobe iptable_nat
    modprobe iptable_filter
    modprobe iptable_mangle

    ### Define a política padrão do firewall ###
    iptables -P INPUT DROP
    iptables -P OUTPUT ACCEPT
    iptables -P FORWARD DROP
    # Ip6tables #
    ip6tables -P INPUT DROP
    ip6tables -P FORWARD DROP
    ip6tables -P OUTPUT DROP

    ### Liberando DNS ###
    iptables -A FORWARD -p udp --dport 53 -j ACCEPT
    iptables -A FORWARD -p tcp --dport 53 -j ACCEPT
    iptables -A INPUT -p udp --dport 53 -j ACCEPT
    iptables -A INPUT -p tcp --dport 53 -j ACCEPT

    ### Jogando tráfego da porta 80 e 443 para o Squid ###
    iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 3128
    iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 3130

    ### Regras INPUT ###
    iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
    iptables -A INPUT -m state --state NEW -i !$EXT -j ACCEPT
    # Loopback #
    iptables -A INPUT -i lo -j ACCEPT
    # ICMP 0 #
    iptables -A INPUT -p icmp --icmp-type 0 -j ACCEPT
    # ICMP 8 #
    iptables -A INPUT -p icmp --icmp-type 8 -j ACCEPT
    # SSH #
    iptables -A INPUT -p tcp --dport 22 -j ACCEPT
    # FTP #
    iptables -A INPUT -p tcp --dport 21 -j ACCEPT
    # OpenVPN #
    iptables -A INPUT -p tcp --dport 1194 -j ACCEPT
    # HTTP #
    iptables -A INPUT -p tcp --dport 80 -j ACCEPT
    # SAMBA #
    iptables -A INPUT -p tcp --dport 139 -j ACCEPT
    iptables -A INPUT -p udp --dport 139 -j ACCEPT
    # VOIP #
    iptables -A INPUT -p udp --dport 5060 -j ACCEPT

    ### Regras FORWARD ###
    iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
    iptables -A FORWARD -m state --state NEW -i !$EXT -j ACCEPT
    # ICMP #
    iptables -A FORWARD -p icmp -j ACCEPT
    # SMTP #
    iptables -A FORWARD -p tcp --dport 25 -j ACCEPT
    iptables -A FORWARD -p tcp --dport 587 -j ACCEPT
    iptables -A FORWARD -p tcp --dport 465 -j ACCEPT
    # IMAP #
    iptables -A FORWARD -p tcp --dport 993 -j ACCEPT
    # POP3 #
    iptables -A FORWARD -p tcp --dport 995 -j ACCEPT
        # POP #
        iptables -A FORWARD -p tcp --dport 110 -j ACCEPT
    # SSH #
    iptables -A FORWARD -p tcp --dport 22 -j ACCEPT
    # FTP #
    iptables -A FORWARD -p tcp --dport 20 -j ACCEPT
    iptables -A FORWARD -p tcp --dport 21 -j ACCEPT
    # POP #
    iptables -A FORWARD -p tcp --dport 110 -j ACCEPT
    # MS Terminal Server #
    iptables -A FORWARD -p tcp --dport 3389 -j ACCEPT
    # HTTP #
    iptables -A FORWARD -p tcp --dport 80 -j ACCEPT
    # HTTPS #
    iptables -A FORWARD -p tcp --dport 443 -j ACCEPT
    # VNC #
    iptables -A FORWARD -p tcp --dport 5900 -j ACCEPT
        # SAMBA #
        iptables -A FORWARD -p tcp --dport 139 -j ACCEPT
        iptables -A FORWARD -p udp --dport 139 -j ACCEPT
    # VOIP #
    iptables -A FORWARD -p udp --sport 5060 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
    iptables -A FORWARD -p udp --dport 5060 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
    iptables -A FORWARD -p udp --sport 10000:20000 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
    iptables -A FORWARD -p udp --dport 10000:20000 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
    # Sites #
    for list in `cat /etc/firewall/sites_bloq` ; do
        iptables -I FORWARD -m string --algo bm --string $list -j DROP
    done

    ### Regras OUTPUT ###
    iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
    iptables -A OUTPUT -m state --state NEW -o !$EXT -j ACCEPT

    ### Regras POSTROUTING ###
    route add default gw 192.168.100.1 2> /dev/null
    echo 1 > /proc/sys/net/ipv4/ip_forward
    iptables -t nat -A POSTROUTING -o $EXT -j MASQUERADE
}

case $1 in
    "")
        start
        echo -e "Firewall ativado\nPara ajuda, adicione o parâmetro '--help'"
        ;;
    --start)
        start
        echo -e "Firewall ativado\nPara ajuda, adicione o parâmetro '--help'"
        ;;
    --stop)
        stop
        echo -e "Firewall desativado\nPara ajuda, adicione o parâmetro '--help'"
        ;;
    --restart)
        stop
        start
        echo -e "Firewall reiniciado\nPara ajuda, adicione o parâmetro '--help'"
        ;;
    --help)
        help
        ;;
    *)
        echo -e "Parâmetro inválido\nPara ajuda, adicione o parâmetro '--help'"
        exit 0
        ;;
esac

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