Este é um script de firewall simples, mas funcional, que utilizo sempre como base para iniciar qualquer pequeno projeto com aquelas mesmas configurações de sempre (kk). Eu removi bastante particularidades dele, deixando-o com apenas o essencial para postar aqui e ser útil a qualquer um. Neste exemplo, o link interno vem de um bonding (união das placas eth1 e eth2), o link externo vem de ppp0 com IP dinâmico!!

No mesmo host há o Squid, Apache, Openfire, MySQL, VPN (PPTP)... e dentro da rede alguns webservers...

Correções, melhorias e qualquer outra coisa é bem-vinda!! Este script surgiu juntando vários outros que estão disponíveis na internet e também de necessidades (exemplo, o retorno visual e o sleep era para que o estagiário soubesse que o script "rodou"...).

• Download exemplo de firewall
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Esconder código-fonte

#!/bin/bash
#
# ## BEGIN INIT INFO
# Provides:         Firewall
# Required-Start:   $all
# Required-Stop:
# Should-Start: S
# Should-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Firewall - Eslih
# Description: Script para Firewall
#
# ## END INIT INFO


#############################
#           VARIAVEIS       #
#############################
# bond0 --> união da eth1 e eth2
placa_interna=bond0
placa_externa=ppp0
rede_interna=172.22.0.0/24
rede_externa=0.0.0.0/0.0.0.0
LOG_FLOOD="1/s"
IPT=$(which iptables)
ROUTE=$(which route)
# A variável abaixo é para saber qual meu IP Externo, pois o link ppp0 trata-se de adsl de ip dinâmico
ip_externo=$(ifconfig ppp0 | grep -i "inet end.:" | cut -d : -f 2 | grep -i [^Bcast] > /tmp/ifconfig.txt && cat /tmp/ifconfig.txt | cut -d " " -f 2)
OK="[ \E[01;32mOK\E[m ]"
NO="[ \E[01;31mNO\E[m ]"


start ()
{
#########################
#        MODULOS        #
#########################

modprobe ip_conntrack_ftp
modprobe ip_nat_ftp
modprobe ipt_state
modprobe ipt_limit
modprobe ipt_MASQUERADE
modprobe ipt_LOG
modprobe iptable_nat
modprobe iptable_filter
modprobe ip_gre
echo -e "Carregando modulos do kernel \t\t\t\t $OK"
#sleep 1







#########################
#        NEGAR          #
#########################

$IPT -P INPUT DROP
$IPT -P FORWARD DROP
$IPT -P OUTPUT ACCEPT
$IPT -A INPUT -i lo -j ACCEPT
echo -e "Fechando o Firewall \t\t\t\t\t $OK"
echo -e "DROP em INPUT e FORWARD \t\t\t\t $OK"
#sleep 1


#########################
#        LIMPAR     #
#########################

$IPT -F
$IPT -X
$IPT -F -t nat
$IPT -X -t nat
$IPT -F -t mangle
$IPT -X -t mangle
$IPT -A INPUT -i lo -j ACCEPT

echo -e "Eliminado regras existentes \t\t\t\t $OK"
echo -e "Limpando Firewall \t\t\t\t\t $OK"
#sleep 1


#########################
#        PROTEÇAO   #
#########################

#Barrando Time
iptables -A INPUT -p TCP --dport 113 -j DROP

#Barrando Auth
iptables -A INPUT -p TCP --dport 37 -j DROP

#Barrando VNC
iptables -A INPUT -p TCP --dport 5901 -j DROP
iptables -A INPUT -p TCP --dport 5900 -j DROP

#Barrando X11
iptables -A INPUT -p TCP --dport 6000 -j DROP
iptables -A INPUT -p TCP --dport 6001 -j DROP

#Proteção contra ping da morte
iptables -A FORWARD -p icmp --icmp-type echo-request -m limit --limit 1/s -j ACCEPT

#Proteções contra syn-floods
iptables -A FORWARD -p tcp --syn -m limit --limit 1/s -j ACCEPT
echo 1 > /proc/sys/net/ipv4/tcp_syncookies
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses

#Proteção contra port scanners ocultos
iptables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST RST -m limit --limit 1/s -j ACCEPT

#Proteções contra spoofing
echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter
echo 0 > /proc/sys/net/ipv4/conf/all/accept_source_route


echo -e "Inserindo camadas de proteção \t\t\t\t $OK"
#sleep 1



#########################
#        LOGS       #
#########################

$IPT -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -N log
$IPT -A log -j LOG --log-prefix [firewall]
$IPT -A INPUT -p tcp --dport 1753 -j LOG --log-prefix=" [ACESSO SSH] "
$IPT -A INPUT -p tcp --dport 22 -j LOG --log-prefix=" [ACESSO SSH] "
$IPT -A INPUT -p tcp --dport 80 -j LOG --log-prefix=" [TENTATIVA ACESSO APACHE] "
$IPT -A INPUT -p tcp --dport 53 -j LOG --log-prefix=" [TENTATIVA ACESSO DNS] "
$IPT -A INPUT -p tcp --dport 3306 -j LOG --log-prefix=" [TENTATIVA ACESSO MYSQL] "
$IPT -A INPUT -p tcp --dport 21 -j LOG --log-prefix=" [TENTATIVA ACESSO FTP] "
$IPT -A INPUT -p tcp --dport 3128 -j LOG --log-prefix=" [ACESSO AO SQUID] "
$IPT -A INPUT -p tcp --dport 25 -j LOG --log-prefix " [ACESSO AO SMTP] "
$IPT -A INPUT -p tcp --dport 143 -j LOG --log-prefix " [ACESSO AO IMAP] "
$IPT -A INPUT -p tcp --dport 110 -j LOG --log-prefix " [ACESSO AO POP] "

$IPT -A INPUT -p icmp -m limit --limit $LOG_FLOOD -j LOG --log-level info --log-prefix " [ICMP Dropped] "
$IPT -A INPUT -p tcp -m limit --limit $LOG_FLOOD -j LOG --log-level info --log-prefix " [TCP Dropped] "
$IPT -A INPUT -p udp -m limit --limit $LOG_FLOOD -j LOG --log-level info --log-prefix " [UDP Dropped] "
$IPT -A INPUT -f -m limit --limit $LOG_FLOOD -j LOG --log-level warning --log-prefix " [FRAGMENT Dropped] "
$IPT -A INPUT -m limit --limit 1/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix " [IPT INPUT packet died:] "
$IPT -A INPUT -m limit --limit 3/minute --limit-burst 3 -j LOG --log-level DEBUG --log-prefix " [IPT INPUT packet died:] "



echo -e "Habilitando logs do firewall \t\t\t\t $OK"
#sleep 1



#########################
#        INPUT      #
#########################

$IPT -A INPUT -i lo -j ACCEPT
$IPT -I INPUT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
# SQUID:
$IPT -A INPUT -i $placa_interna -p tcp --dport 3128 -j ACCEPT
# MYSQL:
$IPT -A INPUT -p tcp --dport 3306 -j ACCEPT
# DNS:
$IPT -A INPUT -i $placa_interna -p udp --dport 53 -j ACCEPT
# SSH:
$IPT -A INPUT -p tcp --dport 1753 -j ACCEPT

#Openfire - Servidor Jabber XMPP
$IPT -A INPUT -p tcp --dport 8080 -j ACCEPT
$IPT -A INPUT -p tcp --dport 5222 -j ACCEPT
$IPT -A INPUT -i $placa_interna -p tcp --dport 5222 -j ACCEPT

#Acessos web - para redirecionamentos a webservers internos da rede
$IPT -A INPUT -p tcp --dport 8988 -j ACCEPT
$IPT -A INPUT -p tcp --dport 8987 -j ACCEPT
$IPT -A INPUT -p tcp --dport 8986 -j ACCEPT

# VPN
$IPT -A INPUT -p tcp --dport 1723 -j ACCEPT
$IPT -A INPUT -i ppp0 -p tcp --dport 1723 -j ACCEPT


# Webmin
$IPT -A INPUT -s $rede_interna -p tcp --dport 12121 -j ACCEPT
#Acesso externo ao webmin
$IPT -A INPUT -i $placa_externa -p tcp --dport 12121 -j ACCEPT


echo -e "Configurando as opções e conexões de INPUT \t\t $OK"
#sleep 1


#########################
#        FORWARD    #
#########################

$IPT -I FORWARD -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

### Gerencia - IPs fixados no dhcp server ###
$IPT -A FORWARD -m iprange --src-range 172.22.0.95-172.22.0.99 -j ACCEPT


### Liberacao de Portas ###
# MYSQL:
$IPT -A FORWARD -p tcp --dport 3306 -j ACCEPT
# ASTERISK - SIP
$IPT -A FORWARD -p udp --dport 5060 -j ACCEPT
# ASTERISK - SIP
$IPT -A FORWARD -p udp --dport 3478 -j ACCEPT
# ASTERISK - SIP
$IPT -A FORWARD -p udp --dport 3479 -j ACCEPT

# ASTERISK - AIX2/IAX
$IPT -A FORWARD -p udp --dport 4569 -j ACCEPT
$IPT -A FORWARD -p udp --dport 5036 -j ACCEPT
# MGCP
$IPT -A FORWARD -p udp --dport 2727 -j ACCEPT
# DNS
$IPT -A FORWARD -p udp --dport 53 -j ACCEPT
# HTTP,HTTPS
$IPT -A FORWARD -p tcp -m multiport --dport 80,443 -j ACCEPT
# e-mail:
$IPT -A FORWARD -p tcp -m multiport --dport 25,110,110,995,587 -j ACCEPT
# SSH:
$IPT -A FORWARD -p tcp -m multiport --dport 1753 -j ACCEPT
# Audio VOIP:
$IPT -A FORWARD -p udp --dport 10001:20000 -j ACCEPT
# FTP:
$IPT -A FORWARD -p tcp -m multiport --dport 20,21 -j ACCEPT

# Paginas webservers
$IPT -A FORWARD -p tcp -m multiport --dport 8989,8988,8987,8986 -j ACCEPT

# ACBr
$IPT -A FORWARD -p tcp -m multiport --dport 3436 -j ACCEPT
# Bradesco obbplus - tcp
$IPT -A FORWARD -p tcp --dport 3000 -j ACCEPT
# Bradesco obbplus - udp
$IPT -A FORWARD -p udp --dport 3000 -j ACCEPT
# Terminal Service
$IPT -A FORWARD -p tcp --dport 3389 -j ACCEPT
# Redirecionamento para Aplicação Interna, clientes externos
$IPT -A FORWARD -p tcp -i $placa_externa --destination-port 19234 --destination 172.22.0.207 -j ACCEPT
$IPT -t nat -A PREROUTING -p tcp -i $placa_externa --destination-port 19234 -j DNAT --to-destination 172.22.0.207:19234

# TS - RDP p/ Windows
$IPT -t nat -A PREROUTING -p tcp --dport 3389 -j DNAT --to 172.22.0.207
$IPT -A FORWARD -p tcp --dport 3389 -j ACCEPT


#Servidor OpenVZ
$IPT -t nat -A PREROUTING -p tcp --dport 8006 -j DNAT --to 172.22.0.250
$IPT -A FORWARD -p tcp --dport 8006 -j ACCEPT

#Servidor SVN - OpenVZ VM
$IPT -t nat -A PREROUTING -p tcp --dport 3690 -j DNAT --to 172.22.0.244
$IPT -A FORWARD -p tcp --dport 3690 -j ACCEPT

#Servidor SVN - OpenVZ VM
$IPT -t nat -A PREROUTING -p tcp --dport 8989 -j DNAT --to 172.22.0.244:80
$IPT -A FORWARD -p tcp --dport 8989 -j ACCEPT

#Servidor web243 - OpenVZ VM
#$IPT -t nat -A PREROUTING -p tcp --dport 8988 -j DNAT --to 172.22.0.243:80
#$IPT -A FORWARD -p tcp --dport 8988 -j ACCEPT

#Servidor LAMP - Eslih
$IPT -t nat -A PREROUTING -p tcp --dport 8986 -j DNAT --to 172.22.0.247:80
$IPT -A FORWARD -p tcp --dport 8986 -j ACCEPT

#Servidor VOIP - SSH
$IPT -t nat -A PREROUTING -p tcp --dport 22100 -j DNAT --to 172.22.0.241:22
$IPT -A FORWARD -p tcp --dport 22100 -j ACCEPT


#Webchat - Cliente Jabber XMPP
$IPT -A FORWARD -p tcp --dport 8080 -j ACCEPT

$IPT -A FORWARD -p tcp -i ppp0 -s 172.22.0.0/24 --dport 21 -j ACCEPT
$IPT -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT

#MySQL
$IPT -A INPUT -p tcp --dport 3306 -j ACCEPT
$IPT -t nat -A POSTROUTING -p tcp --dport 3306 -j MASQUERADE

$IPT -A INPUT -m multiport -p tcp --dport 20,21 -j ACCEPT
$IPT -t nat -A POSTROUTING -m multiport -p tcp --dport 20,21 -j MASQUERADE

$IPT -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
$IPT -A INPUT -p tcp --sport 21 -m state --state ESTABLISHED -j ACCEPT
$IPT -A OUTPUT -p tcp --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT
$IPT -A INPUT -p tcp --sport 20 -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -p tcp --dport 20 -m state --state ESTABLISHED -j ACCEPT
$IPT -A INPUT -p tcp --sport 1024: --dport 1024: -m state --state ESTABLISHED -j ACCEPT
$IPT -A OUTPUT -p tcp --sport 1024: --dport 1024: -m state --state ESTABLISHED,RELATED -j ACCEPT



echo -e "Configurando regras de FORWARD \t\t\t\t $OK"
echo -e "Habilitando portas do firewall \t\t\t\t $OK"
#sleep 2


#########################
#        NAT        #
#########################

# Masquerade da conexao de internet
echo 1 > /proc/sys/net/ipv4/ip_forward
#$IPT -t nat -A POSTROUTING -o $placa_externa -j MASQUERADE
$IPT -t nat -A POSTROUTING -o $placa_interna -j MASQUERADE


# ACESSO Externo das maquinas em VPN
$IPT -A POSTROUTING -s 172.22.0.0/24 -j MASQUERADE


# Redirecionamento de requisicoes WWW p/ SQUID
$IPT -t nat -A PREROUTING -s $rede_interna -p tcp --dport 80  -j REDIRECT --to-port 3128



echo -e "Acionando NAT e redirecionamento \t\t\t $OK"
echo -e "Habilitando Internet \t\t\t\t\t $OK"
#sleep 1
}

case "$1" in
'start')
    start
    echo -e "FIREWALL EXECUTADO \t\t\t\t\t $OK"

    #sleep 1
        ;;


'filter') $IPT -nL | more
        ;;

'status') $IPT -L -vn | more
        ;;

'nat') $IPT -t nat -L -nv | more
        ;;

'mangle') $IPT -t mangle -nL | more
    ;;

*) echo "erro use "$0" {start|filter|nat|mangle}"
           exit 1
        ;;
esac
exit 0

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