Senhores, seria possível analisarem meu script de firewall ?
O problema é o seguinte: Quando adoto uma política OUTPUT DROP não
consigo navegar na Internet.
#!/bin/sh
IPTABLES=/sbin/iptables
IFLAN=eth0
IFWAN=eth1
LAN=172.21.5.0/24
WAN=172.18.0.0/16
# Ativando modulos
# -------------------------------------------------------
echo "Ativando modulos"
echo
" "
/sbin/modprobe iptable_nat
/sbin/modprobe ip_conntrack
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_nat_ftp
/sbin/modprobe ipt_LOG
/sbin/modprobe ipt_MASQUERADE
/sbin/modprobe sch_sfq
/sbin/modprobe sch_htb
/sbin/modprobe cls_u32
echo "Habilitando o filtro de ip ( seguranca ) Protecao contra IP spoofing"
echo " "
echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter
echo "1" > /proc/sys/net/ipv4/conf/eth0/rp_filter
echo "1" > /proc/sys/net/ipv4/conf/eth1/rp_filter
# Ativa roteamento no kernel
# -------------------------------------------------------
echo "Ativando repasse de pacotes"
echo " "
echo "1" > /proc/sys/net/ipv4/ip_forward
# Ativa syn cookies
# -------------------------------------------------------
echo "Ativando syn cookies"
echo " "
echo "1" > /proc/sys/net/ipv4/tcp_syncookies
# Zera regras
#
-------------------------------------------------------
echo "Limpando as regras antigas"
echo " "
$IPTABLES -F
$IPTABLES -X
$IPTABLES -F -t nat
$IPTABLES -X -t nat
$IPTABLES -F -t mangle
$IPTABLES -X -t mangle
echo "Definindo a politica padrao"
echo " "
# Determina a politica padrao
$IPTABLES -P INPUT DROP
$IPTABLES -P FORWARD DROP
$IPTABLES -P OUTPUT DROP
# Aceita pacotes que ja estabelecerao conexao ( Statefull)
#-----------------------------------------------
echo "Definindo regras Statefull"
echo " "
$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Aceitando pela interface interna
#-----------------------------------------------
echo "Liberando icmp local"
echo " "
$IPTABLES -A INPUT -i lo -j ACCEPT
$IPTABLES -A OUTPUT -o lo -j ACCEPT
# Liberando ICMP para
rede
#-----------------------------------------------
echo "Liberando icmp para rede"
echo " "
$IPTABLES -A INPUT -p icmp -s $LAN -j ACCEPT
$IPTABLES -A FORWARD -p icmp -s $LAN -j ACCEPT
# Acesso ssh (firewall)
#-----------------------------------------------
echo "Liberando ssh"
echo " "
$IPTABLES -A INPUT -p tcp -i $IFLAN -s $LAN --dport 22 -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 22 -j ACCEPT
#DNS udp=consulta tcp=transferencia
echo "Liberando DNS"
echo " "
$IPTABLES -A FORWARD -p udp -s $LAN --dport 53 -j ACCEPT
$IPTABLES -A INPUT -p udp -s $LAN --dport 53 -j ACCEPT
$IPTABLES -A FORWARD -p tcp -s $WAN --dport 53 -j ACCEPT
$IPTABLES -A INPUT -p tcp -s $WAN --dport 53 -j ACCEPT
#DHCP
echo "Liberando DHCP"
echo " "
$IPTABLES -A FORWARD -p udp -i $IFLAN -s $LAN --dport 68 -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 67 -j
ACCEPT
#E-Mail
echo "Liberando servico de e-mail"
echo " "
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 110 -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 25 -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 143 -j ACCEPT
#LDAP, SAMBA e AD
echo "Liberando servico LDAP, SAMBA e AD"
echo " "
#Replicacao LDAP semef
$IPTABLES -A FORWARD -p tcp -i $IFWAN -s 172.18.1.164 --dport 389 -j ACCEPT
#Microsoft Naked CIFS
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 445 -j ACCEPT
$IPTABLES -A FORWARD -p udp -i $IFLAN -s $LAN --dport 445 -j ACCEPT
#NETBIOS Name Service
$IPTABLES -A FORWARD -p udp -i $IFLAN -s $LAN --dport 137 -j ACCEPT
#NETBIOS Datagram Service
$IPTABLES -A FORWARD -p udp -i $IFLAN -s $LAN --dport 138 -j ACCEPT
#NETBIOS session service
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 139 -j ACCEPT
#https
echo "Liberando
https"
echo " "
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 443 -j ACCEPT
#http
echo "Liberando http para acesso ao Sarg"
echo " "
$IPTABLES -A INPUT -p tcp -i $IFLAN -s $LAN --dport 80 -j ACCEPT
$IPTABLES -A INPUT -p tcp -i $IFLAN -s $LAN --dport 3128 -j ACCEPT
$IPTABLES -A FORWARD -p tcp -i $IFLAN -s $LAN --dport 80 -j ACCEPT
# Proxy transparente
# ----------------------------
#echo "Ativando proxy transparente"
#echo " "
$IPTABLES -t nat -A PREROUTING -p tcp -d ! 172.0.0.0/8 --dport 80 -j
REDIRECT --to-port 3128
#################################################
# Tabela NAT #
#################################################
# MASCARAMENTO
$IPTABLES -t nat -A POSTROUTING -o $IFWAN
-j MASQUERADE
_______________________________________________________
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