Firewall avançado [Shell Script]

Firewall avançado

Publicado por Eduardo Vieira Mendes 21/07/2008

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Script de firewall avançado, com várias opções, como liberação de certos ips, liberação de ip/porta, checagem de sanidade do script, compatibilidade com funções start|stop|restart do RedHat, entre outros. Tudo bem comentado.
Esconder código-fonte
#!/bin/sh
# iptables, by Alexandre Iamamoto
# $Id: iptables,v 1.61 06/06/2004 10:03:00
# chkconfig: 2345 08 80
# description: Script de configuraÃ§ao da rede e firewall
# processname: iptables

# Usando RedHat Linux?
REDHAT="YES"
# O firewall estÃ¡ ativado (Y/N)?
ATIVADO="Y"
ATIVAREDIR="Y"
ATIVAPROXY="Y"

# Executar teste de Sanidade do script?
OVERRIDE_SANITY_CHECKS="FALSE"
PROXY="192.168.0.254" # Endereco do Proxy
PROXYPORTA="3128"  # Porta do Proxy
REDIRECIONAMENTOS=/etc/redirecionamentos.txt
PORTAS_LIBERADAS_TCP=(20 21 22 25 53 80 110 1234 143 1064 1065 1723 3389)
PORTAS_LIBERADAS_UDP=(1234 1723 53 5222)

# Cores
VERDE=$'\e[32;01m'
AMARELO=$'\e[33;01m'
VERMELHO=$'\e[31;01m'
NORMAL=$'\e[0m'


# Interfaces de Rede
# Modifique suas interfaces de rede aqui
# Interna e externa
INTERNALIF="eth0"
EXTERNALIF="eth1"
# Enderecos de Rede

# Rede interna
INTERNALNET="192.168.0.0/24"

# Broadcast
INTERNALBCAST="192.168.0.255"

# Especificos
# Ips que sao permitidos tudo, nao passam pelo proxy
IPSPERMITIDOSTUDO=(192.168.0.1 192.168.0.2 192.168.0.3 192.168.0.9 192.168.0.10 192.168.0.74 192.168.0.65 192.168.0.54 192.168.0.53 192.168.0.94 192.168.0.55 192.168.0.92 192.168.0.82 192.168.0.95 192.168.0.77 192.198.0.66);

MODULOSA=(ip_tables iptable_filter ip_conntrack ip_conntrack_ftp ip_nat_ftp);

# Mude os x para os seus ips, externo e interno
EXTERNAL_IP=xxx.xxx.xxx.xx
INTERNAL_IP=xxx.xxx.x.xxx

OVERRIDE_NO_FORWARD="FALSE"
USE_SYNCOOKIES="TRUE"

# Caminhos de programas
DMESG="/bin/dmesg"
IPTABLES="`which iptables`"
MODPROBE="/sbin/modprobe"
/sbin/modprobe ip_tables
/sbin/modprobe iptable_filter
/sbin/modprobe ip_conntrack
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_nat_ftp


# Este é uma função do Red Hat que habilita o sistema de start/stop/restart
if [ X"$REDHAT" = X"YES" ]; then
        . /etc/rc.d/init.d/functions
        case "$1" in
                stop)
action "Desligando Firewall:" echo
echo -n "Limpando regras: "
${IPTABLES} -t filter -F INPUT
echo -n "INPUT "
${IPTABLES} -t filter -F OUTPUT
echo -n "OUTPUT1 "
${IPTABLES} -t filter -F FORWARD
echo -n "FORWARD "
${IPTABLES} -t nat -F PREROUTING
echo -n "PREROUTING1 "
${IPTABLES} -t nat -F OUTPUT
echo -n "OUTPUT2 "
${IPTABLES} -t nat -F POSTROUTING
echo -n "POSTROUTING "
${IPTABLES} -t mangle -F PREROUTING
echo -n "PREROUTING2 "
${IPTABLES} -t mangle -F OUTPUT
echo -n "OUTPUT3"
echo
                        exit 0
                        ;;
                status)
                        echo "The status command is not supported for iptables"
                        exit 0
                        ;;
                restart|reload)
                        $0 stop
                        exec $0 start
                        ;;
                start)
                        action "Iniciando Firewall:" echo
                        ;;
                *)
                        echo "Utilizacao: iptables (start|stop|restart)"
                        exit 1
        esac
fi
################################################################


#------------------------------------------------------------
#Informa configuracoes
echo Interface externa: $EXTERNALIF Ip externo: $EXTERNAL_IP
echo Interface interna: $INTERNALIF Ip externo: $INTERNAL_IP

#Inicia teste de sanidade no script
if [ "$OVERRIDE_SANITY_CHECKS" = "TRUE" ] ; then
echo "Teste Ignorado! Se acontecerem problemas não reclame!"
echo "Se existe um motivo para isso por favor informe o suporte do sistema 62 205-1422"
echo
echo -n "Aguarde 5 segundos..."
sleep 5
echo "continuando"
echo
echo 
else
# Esta ativado?
if ! [ "$ATIVADO" = "Y" ] ; then
echo
echo "${VERMELHO} SUA CONFIGURACAO INDICA QUE O FIREWALL ESTA DESATIVADO"
echo -n "$VERDE"
exit 99
fi
# É dificil executar o firewall sem o iptables...
if ! [ -x $IPTABLES ] ; then
echo
echo "ERRO NA CONFIGURAÇÃO: ${IPTABLES} não existe ou não é executável!"
exit 4
fi



fi
# Insere os modulos no kernel
  dmesg -n 1 #Mata mensagem de carregamento
  let CONTADOR=0;
  for TEMP_VAR01 in ${MODULOSA[@]} ; do
        echo Carregando o modulo de kernel: $TEMP_VAR01
        $MODPROBE $TEMP_VAR01
        let CONTADOR=$CONTADOR+1;
  done;

                        echo -n "Limpando regras: "
                        ${IPTABLES} -t filter -F INPUT
                        echo -n "INPUT "
                        ${IPTABLES} -t filter -F OUTPUT
                        echo -n "OUTPUT1 "
                        ${IPTABLES} -t filter -F FORWARD
                        echo -n "FORWARD "
                        ${IPTABLES} -t nat -F PREROUTING
                        echo -n "PREROUTING1 "
                        ${IPTABLES} -t nat -F OUTPUT
                        echo -n "OUTPUT2 "
                        ${IPTABLES} -t nat -F POSTROUTING
                        echo -n "POSTROUTING "
                        ${IPTABLES} -t mangle -F PREROUTING
                        echo -n "PREROUTING2 "
                        ${IPTABLES} -t mangle -F OUTPUT
                        echo -n "OUTPUT3"
                        echo

##Setup sysctl controls which affect tcp/ip
#

if [ "$INTERNALNET" != "" ] && [ "$OVERRIDE_NO_FORWARD" != "TRUE" ] ; then
        echo -n "Checando por IP Forwarding..."
        if [ -e /proc/sys/net/ipv4/ip_forward ] ; then
                echo 1 > /proc/sys/net/ipv4/ip_forward
                echo "ativado."
        else
                echo "support not found! This will cause problems if you need to do any routing."
        fi
fi
# Enable TCP Syncookies
echo -n "Checando por IP SynCookies..."
if [ -e /proc/sys/net/ipv4/tcp_syncookies ] ; then
        if [ "$USE_SYNCOOKIES" = "TRUE" ] ; then
                echo 1 > /proc/sys/net/ipv4/tcp_syncookies
                echo "ativado."
        else
                echo 0 > /proc/sys/net/ipv4/tcp_syncookies
                echo "desativado."
        fi
else
        echo "suporte nao encontrado, porem ok."
fi

#Disabling IP Spoofing attacks.
echo 2 > /proc/sys/net/ipv4/conf/all/rp_filter

#Don't respond to broadcast pings
echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

#Defragment all Packets
#Default now

#Enable forwarding
#echo 1 >/proc/sys/net/ipv4/ip_forward

#Block source routing
echo 0 >/proc/sys/net/ipv4/conf/all/accept_source_route

#Kill timestamps.  These have been the subject of a recent bugtraq thread
echo 0 > /proc/sys/net/ipv4/tcp_timestamps

#Enable SYN Cookies
#echo 1 > /proc/sys/net/ipv4/tcp_syncookies

#Kill redirects
echo 0 >/proc/sys/net/ipv4/conf/all/accept_redirects

#Enable bad error message protection
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses

#Allow dynamic ip addresses
echo "1" > /proc/sys/net/ipv4/ip_dynaddr

#Log martians (packets with impossible addresses)
#RiVaL said that certain NICs don't like this.  Comment out if necessary.
#echo 1 >/proc/sys/net/ipv4/conf/all/log_martians
echo 0 >/proc/sys/net/ipv4/conf/all/log_martians

#Set out local port range
echo "32768 61000" >/proc/sys/net/ipv4/ip_local_port_range

#Reduce DoS'ing ability by reducing timeouts
echo 30 > /proc/sys/net/ipv4/tcp_fin_timeout
echo 1800 > /proc/sys/net/ipv4/tcp_keepalive_time
echo 1 > /proc/sys/net/ipv4/tcp_window_scaling
echo 0 > /proc/sys/net/ipv4/tcp_sack
echo 1280 > /proc/sys/net/ipv4/tcp_max_syn_backlog
#
# Permite que pacotes oriundos da interface loopback 
#
$IPTABLES -A INPUT -i lo -j ACCEPT
#
# Mata qualquer pacote venha da rede 127
# 
$IPTABLES -A INPUT -d 127.0.0.0/8 -j REJECT
#
# Permite acesso ao servidor via redes locais e VPN
#
$IPTABLES -A INPUT -i $INTERNALIF -s $INTERNALNET -j ACCEPT

#
# Funcao navegacao total dos ips listados na variavel 
# 
echo Ips Liberados a sair totalmente: ${IPSPERMITIDOSTUDO}
  let CONTADOR=0;
  for TEMP_VAR01 in ${IPSPERMITIDOSTUDO[@]} ; do
echo Liberando acesso completo a: $TEMP_VAR01
        $IPTABLES -A FORWARD -o $EXTERNALIF -i $INTERNALIF -s $TEMP_VAR01 -j ACCEPT;
        let CONTADOR=$CONTADOR+1;
  done;


#
#Allow IPV6 tunnel traffic
#$IPTABLES -A INPUT -p ipv6 -j ACCEPT

#Allow IPSEC tunnel traffic
#$IPTABLES -A INPUT -p 50 -j ACCEPT
#Allow all traffic from the ipsec device to the internal network
#$IPTABLES -A FORWARD -i ipsec0 -o $INTERNALIF -j ACCEPT

#Kill anything from outside claiming to be from internal network
$IPTABLES -A INPUT -i $EXTERNALIF -s $INTERNALNET -j REJECT

##ICMP
#ping don't forward pings going inside
#$IPTABLES -A FORWARD -p icmp --icmp-type echo-request -o $INTERNALIF -j REJECT
#ping flood protection
$IPTABLES -A INPUT -p icmp --icmp-type echo-request -m limit --limit 1/s -j ACCEPT
$IPTABLES -A INPUT -p icmp --icmp-type echo-request -j DROP
#Deny icmp to broadcast address
$IPTABLES -A INPUT -p icmp -d $INTERNALBCAST -j DROP

#Allow all other icmp
$IPTABLES -A INPUT -p icmp -j ACCEPT

#ProteÃ§ao contra tcp FIN


##Allow established connections
#Unlike ipchains, we don't have to go through the business of allowing
#a local port range- just allow all connections already established.

$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

#Note that unlike ipchains, the following must be enabled even with masquerading
#Don't forward SMB related traffic
#$IPTABLES -A FORWARD -o $EXTERNALIF -p tcp --dport 137 -j REJECT 
#$IPTABLES -A FORWARD -o $EXTERNALIF -p tcp --dport 138 -j REJECT 
#$IPTABLES -A FORWARD -o $EXTERNALIF -p tcp --dport 139 -j REJECT 
#$IPTABLES -A FORWARD -o $EXTERNALIF -p udp --dport 137 -j REJECT 
#$IPTABLES -A FORWARD -o $EXTERNALIF -p udp --dport 138 -j REJECT 
#$IPTABLES -A FORWARD -o $EXTERNALIF -p udp --dport 139 -j REJECT 

#$IPTABLES -A INPUT -i $EXTERNALIF -p udp --dport 137 -j REJECT

#Allow ALL other forwarding going out
#$IPTABLES -A FORWARD -o $EXTERNALIF -i $INTERNALIF -j ACCEPT

#Allow replies coming in

$IPTABLES -A FORWARD -i $EXTERNALIF -m state --state ESTABLISHED,RELATED -j ACCEPT


#Whack allowances
#Allow DHCP- Optus users need this
#$IPTABLES -A INPUT -p udp -d 255.255.255.255 --dport 68 -j ACCEPT

#Allow yourself to be a DHCP server for your inside network
#Necessary because the default rule allowing valid addresses ignores broadcast
$IPTABLES -A INPUT -i $INTERNALIF -p tcp --sport 68 --dport 67 -j ACCEPT
$IPTABLES -A INPUT -i $INTERNALIF -p udp --sport 68 --dport 67 -j ACCEPT

#Allow nameserver packets.  Different versions of iptables seem to error here.
#Comment out if necessary.

cat /etc/resolv.conf | \
awk '/^nameserver/ {print $2}' | \
xargs -n1 $IPTABLES -A INPUT -p udp --sport 53 -j ACCEPT -s

#Allow Telstra hearbeat
#This section is propz to Defed
#$IPTABLES -A INPUT -p udp --sport 5050 -j ACCEPT
#$IPTABLES -A INPUT -p udp --sport 5051 -j ACCEPT

#From here on, we're dealing with connection attempts.
#The -m limit is a DoS protection on connects
#First we allow a certain amount of connections per second
#DROP the rest (so we don't DoS ourself with rejections)
#We don't limit normal packets (!syn) by allowing the rest
##Basic services.  Uncomment to allow in.
# ftp-data


# Funcao para permitir acesso externo a inteface.
  echo Portas abertas: 
  let CONTADOR=0;
  for TEMP_VAR01 in ${PORTAS_LIBERADAS_TCP[@]} ; do
        echo Liberando acesso a porta TCP: $TEMP_VAR01
        $IPTABLES -A INPUT -p tcp --dport $TEMP_VAR01 -j ACCEPT;
        let CONTADOR=$CONTADOR+1;
  done;
  let CONTADOR=0;
  for TEMP_VAR01 in ${PORTAS_LIBERADAS_UDP[@]} ; do
        echo Liberando acesso a porta UDP: $TEMP_VAR01
        $IPTABLES -A INPUT -p udp --dport $TEMP_VAR01 -j ACCEPT;
        let CONTADOR=$CONTADOR+1;
  done;

# smtp  One per second limt -burst rate of ten
$IPTABLES -A INPUT -p tcp --dport 25 --syn -m limit --limit 1/s \
        --limit-burst 10 -j ACCEPT 
$IPTABLES -A INPUT -p tcp --dport 25 --syn -j DROP 
$IPTABLES -A INPUT -p tcp --dport 25 -j ACCEPT

#
##DNAT
        if [ "$ATIVAREDIR" = "Y" ] ; then
echo Ativando redirecionamentos da interface valida para maquinas internas

           if [ -f $REDIRECIONAMENTOS ]; then
             while read IP_PORT; do
               # extract the protocols, IPs and ports
       NAT_TYPE=$(echo "$IP_PORT" | awk '{print $1}')
               NAT_EXT_PORT=$(echo "$IP_PORT" | awk '{print $2}')
               NAT_INT_IP=$(echo "$IP_PORT" | awk '{print $3}')
               NAT_INT_PORT=$(echo "$IP_PORT" | awk '{print $4}')


               ${IPTABLES} -A PREROUTING -t nat -p $NAT_TYPE -d $EXTERNAL_IP --dport $NAT_EXT_PORT -j DNAT --to-destination $NAT_INT_IP:$NAT_INT_PORT
               ${IPTABLES} -A FORWARD -i $EXTERNALIF -o $INTERNALIF -p $NAT_TYPE -d $NAT_INT_IP --dport $NAT_INT_PORT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
               ${IPTABLES} -A FORWARD -i $INTERNALIF -o $EXTERNALIF -p $NAT_TYPE -s $NAT_INT_IP --sport $NAT_INT_PORT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
               ${IPTABLES} -t nat -A POSTROUTING -d $NAT_INT_IP -s $INTERNALNET -p $NAT_TYPE --dport $NAT_INT_PORT -j SNAT --to $INTERNAL_IP
               echo Inserida regra de redirecionamento dnat: $NAT_TYPE:$EXTERNAL_IP:$NAT_EXT_PORT - $NAT_INT_IP:$NAT_INT_PORT
             done < $REDIRECIONAMENTOS

       unset IP_PORT
unset NAT_TYPE
        unset NAT_EXT_PORT
        unset NAT_INT_IP
        unset NAT_INT_PORT
   else
              echo "$REDIRECIONAMENTOS (tabela de redir) nao encontrado! Redirecionamento desabilitado."
   fi
        fi

echo -n $VERMELHO
echo "Enderecos q nao podem passar no proxy:";
echo -n $NORMAL
  let CONTADOR01=0;
  for TEMP_VAR02 in ${IPSNAOPROXY[@]} ; do
        echo -n $VERDE;
        echo "Permitindo acesso nao proxyado a: $TEMP_VAR02";
        echo -n $NORMAL;
        $IPTABLES -A FORWARD -o $EXTERNALIF -i $INTERNALIF -s $TEMP_VAR02 -j ACCEPT;
        #$IPTABLES -A FORWARD -p tcp --dport 80 -d $TEMP_VAR02 -j ACCEPT;
        $IPTABLES -A FORWARD -p tcp -d $TEMP_VAR02 -j ACCEPT;
        #$IPTABLES -A FORWARD -p tcp --dport 443 -d $TEMP_VAR02 -j ACCEPT;
        $IPTABLES -A FORWARD -p udp -d $TEMP_VAR02 -j ACCEPT;
        $IPTABLES -A PREROUTING -t nat -p tcp -d $TEMP_VAR02 -j ACCEPT;
        let CONTADOR01=$CONTADOR01+1;
  done;


# Proxy transparente?
if [ "$ATIVAPROXY" = "Y" ] ; then
echo "Ativando Proxy Transparente para ${PROXY}: "
$IPTABLES -t nat -A PREROUTING -i $INTERNALIF -p tcp --dport 80 -j REDIRECT --to-port 3128        

fi


##Some ports should be denied and logged.
$IPTABLES -A INPUT -p tcp --dport 1433 -m limit -j LOG \
                          --log-prefix "Firewalled packet: MSSQL " 

$IPTABLES -A INPUT -p tcp --dport 1433 -j DROP
$IPTABLES -A INPUT -p tcp --dport 6670 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Deepthrt " 
$IPTABLES -A INPUT -p tcp --dport 6670 -j DROP
$IPTABLES -A INPUT -p tcp --dport 6711 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Sub7 " 
$IPTABLES -A INPUT -p tcp --dport 6711 -j DROP
$IPTABLES -A INPUT -p tcp --dport 6712 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Sub7 " 
$IPTABLES -A INPUT -p tcp --dport 6712 -j DROP
$IPTABLES -A INPUT -p tcp --dport 6713 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Sub7 " 
$IPTABLES -A INPUT -p tcp --dport 6713 -j DROP

$IPTABLES -A INPUT -p tcp --dport 12345 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Netbus " 
$IPTABLES -A INPUT -p tcp --dport 12345 -j DROP
$IPTABLES -A INPUT -p tcp --dport 12346 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Netbus " 
$IPTABLES -A INPUT -p tcp --dport 12346 -j DROP
$IPTABLES -A INPUT -p tcp --dport 20034 -m limit -j LOG \
                          --log-prefix "Firewalled packet: Netbus " 
$IPTABLES -A INPUT -p tcp --dport 20034 -j DROP
$IPTABLES -A INPUT -p tcp --dport 31337 -m limit -j LOG \
                          --log-prefix "Firewalled packet: BO " 
$IPTABLES -A INPUT -p tcp --dport 31337 -j DROP
$IPTABLES -A INPUT -p tcp --dport 6000  -m limit -j LOG \
                          --log-prefix "Firewalled packet: XWin "
$IPTABLES -A INPUT -p tcp --dport 6000  -j DROP


#Traceroutes depend on finding a rejected port.  DROP the ones it uses

$IPTABLES -A INPUT -p udp --dport 33434:33523 -j DROP

#Don't log ident because it gets hit all the time eg connecting to an irc server
$IPTABLES -A INPUT -p tcp --dport 113 -j REJECT

#Don't log igmp.  Some people get too many of these
$IPTABLES -A INPUT -p igmp -j REJECT

#Don't log web or ssl because people surfing for long times lose connection
#tracking and cause the system to create a new one, flooding logs.
$IPTABLES -A INPUT -p tcp --dport 80 -j REJECT
$IPTABLES -A INPUT -p tcp --dport 443 -j REJECT

##Catch all rules.
#iptables reverts to these if it hasn't matched any of the previous rules.
#Log.  There's no point logging noise.  There's too much of it.
#Just log connection requests
$IPTABLES -A INPUT -p tcp --syn -m limit --limit 5/minute -j LOG  \
        --log-prefix "Firewalled packet:"
$IPTABLES -A FORWARD -p tcp --syn -m limit --limit 5/minute -j LOG \
        --log-prefix "Firewalled packet:"
#Reject
$IPTABLES -A INPUT -p tcp -j REJECT --reject-with tcp-reset
$IPTABLES -A INPUT -p all -j DROP

$IPTABLES -A FORWARD -p tcp -j REJECT --reject-with tcp-reset
$IPTABLES -A FORWARD -p all -j DROP  

#Accept it anyway if it's only output
$IPTABLES -A OUTPUT -j ACCEPT

#Masquerade internal connections going out.
$IPTABLES -A POSTROUTING -t nat -o $EXTERNALIF -j MASQUERADE

# Implementacao experimental de seguranca
# Usuario teria que fazer conexao 3 vezes na porta 223 para somente assim
# liberar a porta 221 para efetivar a conexao

#iptables -A INPUT -p tcp -m tcp --dport 221 -m state --state NEW -m recent --rcheck --name SSH --rsource --seconds 60 --hitcount 3 -j ACCEPT 
#iptables -A INPUT -p tcp -m tcp --dport 222 -m state --state NEW -m recent --name SSH --remove -j DROP 
#iptables -A INPUT -p tcp -m tcp --dport 223 -m state --state NEW -m recent --set --name SSH --rsource -j DROP 
#iptables -A INPUT -p tcp -m tcp --dport 224 -m state --state NEW -m recent --name SSH --remove -j DROP 

exit 0
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