FIREWALL
1
Konsep Firewall
 salah satu lapisan pertahanan yang mengatur
hubungan komputer dengan dunia luar melalui
interogasi setiap traffic, packet, dan port-port yang
diatur dengan rule-rule yang ada

Dilakukan dengan cara :
Menyaring
membatasi
menolak
hubungan /kegiatan suatu segmen pada
jaringan pribadi dengan jaringan luar yang
bukan merupakan ruang lingkupnya
2
Konfigurasi Sederhana
pc (jaringan local) <==> firewall <==> internet (jaringan lain)
Boleh lewat mbak ?
Nih surat-suratnya
Anak kecil ga boleh
keluar.. sudah malam
Firewall
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Firewall Topologi :
Basic Two-interface Firewall (no DMZ)
 Connects to ISP using DSL,
Cable Modem, ISDN, Dial-up,
…
 Provides for “Internet
Connection Sharing” of a
single public IP address for a
local network using
SNAT/Masquerading
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Firewall Topologi :
Three-interface Firewall (with DMZ)
 Provides internet connection
sharing of one or more public IP
addresses.
 Had a DMZ containing servers
that are exposed to the internet.
 If a server is hacked, the Firewall
and the Local network aren’t
compromised.
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Tipe Firewall
Berdasarkan mekanisme cara kerja :

Packet Filtering
–

Application Level
–

Biasa disebut proxy firewall, filter bisa berdasarkan content paket
Circuit Level Gateway
–
–

Memfilter paket berdasarkan sumber, tujuan dan atribut paket (filter berdasar
IP dan Port). Yang difilter IP, TCP, UDP, and ICMP headers and port number
Filter berdasarkan sesi komunikasi, dengan pengawasan sesi handshake.
Terdapat sesi NEW/ESTABLISH
Statefull Multilayer Inspection Firewall
–
Kombinasi dari ketiga tipe firewall diatas
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Circuit Level / Stateful Inspection Firewalls

Default Behavior
Permit connections initiated by an internal host
Deny connections initiated by an external host
Can change default behavior with ACL

For DMZ Implementation
Automatically Accept Connection Attempt
Router
Internet
Automatically Deny Connection Attempt
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DMZ Configuration
 Place web servers in the “DMZ” network
 Only allow web ports (TCP ports 80 and 443)
internet
Firewall
Web Server
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DMZ Configuration
 Don’t allow web servers access to your network
 Allow local network to manage web servers (SSH)
 Don’t allow servers to connect to the Internet
Mas ..yang
merah gak
boleh lewat
lho
 Patching is not convenient
internet
Firewall
Web Server
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IPTABLES
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IPTABLES
 iptables is a networking administration
command-line tool on Linux which
interfaces to the kernel-provided Netfilter
modules. This allows for stateless and
stateful firewalls and NAT. It is useful to
think of IPtables as being a specialised
firewall-creation programming language.
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Prinsip Kerja iptables


Paket masuk diproses berdasarkan tujuan :
–
Destination IP untuk Firewall  masuk proses input
–
Destination IP bukan untuk firewall tapi diteruskan  masuk proses
FORWARD
Selanjutnya dicocokkan berdasarkan tabel policy yang dipunyai firewall
apakah di-accept atau di-drop
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Prinsip Kerja Firewall
Firewall Machine
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Sintaks IPTABLES

Opsi
1. -A, menambah satu aturan baru ditempatkan pada posisi terakhir
iptables –A INPUT …
1. -D, menghapus rule
iptables –D INPUT 1
iptables –D –s 202.154.178.2 …
2. -I, menambah aturan baru penempatan bisa disisipkan sesuai
nomor
iptables –I INPUT 3 –s 202.154.178.2 –j ACCEPT
3. -R, mengganti rule
iptables –R INPUT 2 –s –s 202.154.178.2 –j ACCEPT
4. -F, menghapus seluruh rule
iptables –F
5. -L, melihat Rule
iptables -L
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Parameter
 -p [!] protocol, protokol yang akan dicek
Iptables –A INPUT –p tcp …
 -s [!] address/[mask], memeriksa kecocokan sumber paket
Iptables –A INPUT –s 10.252.44.145 …
 -d [!] address/[mask], memerika kecocokan tujuan paket
Iptables –A INPUT –d 202.154.178.2 …
 -j target, menentukan nasib paket, target misal ACCEPT/DROP/REJECT
Iptables –A INPUT –d 202.154.178 –j DROP
 -i [!] interface_name, identifikasi kartu jaringan tempat masuknya data
Iptables –A INPUT –i etho ….
 -o [!] interface_name, identifikasi kartu jaringan tempat keluarnya paket
Iptables –A OUTPUT –o eth1 ….
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Match iptables
 --mac address, matching paket berdasarkan nomor
MAC Address
Iptables –m mac –mac-address 44:45:53:54:00:FF
 Multiport, mendifinisikan banyak port
Iptables –m multiport –source-port 22,25,110,80 –j ACCEPT
 State, mendefinisikan state dari koneksi
Iptables –A INPUT –m state –state NEW, ESTABLISH –j
ACCEPT
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Target/Jump iptables
 ACCEPT, setiap paket langsung diterima
Iptables –A INPUT –p tcp –dport 80 –j ACCEPT
 DROP, paket datang langsung dibuang
Iptables –A INPUT –p tcp –dport 21 –j DROP
 REJECT, paket yang ditolak akan dikirimi pesan ICMP error
Iptables –A INPUT –p tcp –dport 21 –j REJECT
 SNAT, sumber paket dirubah, biasanya yang memiliki koneksi internet
Iptables –t nat –A POSROUTING –p tcp –o eth0 –j SNAT –to-source 202.154.178.2
 DNAT, merubah tujuan alamat paket. Biasanya jika server alamat Ipnya lokal,
supaya internet bisa tetap akses diubah ke publik
Iptables –t nat –A PREPROUTING –p tcp –d 202.154.178.2 –dport 80 –j DNAT –todestination 192.168.1.1
 MASQUERADE, untuk berbagi koneksi internet dimana no_ipnya terbatas, sebagai
mapping ip lokal ke publik
Iptables –t nat –A POSTROUTING –o eth0 –dport 80 –j MASQUERADE
 REDIRECT, sigunakan untuk transparent proxy
Ipatbles –t nat –A PREROUTING –p tcp –d 0/0 –dport 80 –j REDIRECT –to-port 8080
 LOG, melakukan pencatatan terhadap aktifitas firewall kita, untuk melihat bisa
dibuka /etc/syslog.conf
Iptables –A FORWARD –j LOG –log-level-debug
Iptables –A FORWARD –j LOG –log-tcp-options
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Firewall Option



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


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
# Mengeluarkan Modul-modul Iptables
/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
/sbin/modprobe iptable_filter
/sbin/modprobe iptable_mangle
/sbin/modprobe iptable_nat
/sbin/modprobe ipt_LOG
/sbin/modprobe ipt_limit
/sbin/modprobe ipt_state
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_conntrack_irc
/sbin/modprobe ip_nat_ftp
/sbin/modprobe ip_nat_irc
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Menghapus Rule iptables
 # Menghapus aturan iptables
$IPTABLES -F
$IPTABLES -t nat -F
$IPTABLES -t mangle -F
 # Menghapus nama kolom yg dibuat manual
$IPTABLES -X
$IPTABLES -t nat -X
$IPTABLES -t mangle -X
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Packet Filtering Firewall
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Packet Filtering Firewall
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Circuit Level Gateway
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Forward
 iptables –t nat –A POSTROUTING –s IP_number -d 0/0 –j
MASQUERADE
 #iptables –A FORWARD –p icmp –s 0/0 –d 0/0 –j ACCEPT
 Iptables –A INPUT –p imcp –s 0/0 –j DROP
 #iptables –A FORWARD –i eth1 –o eth0 –p icmp –s 10.252.105.109 –d
192.168.108.5 –j ACCEPT
 #iptables –A FORWARD –s 192.168.108.5/24 –d 0/0 –p tcp --dport ftp, -j
REJECT
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Studi Kasus 1

Bangun Jaringan sendiri

Install web server dan FTP Server pada jaringan Internet
(10.252.105.xxx)

Setting memblok PC2 dan PC3 supaya tidak bisa mengakses web
dan FTP
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Setting Komputer Router
PC1
 Setting Ip_forward
#echo 1> /proc/sys/net/ipv4/ip_forward
 Setting menggunakan NAT
iptables –t nat –A POSTROUTING –o eth0 –s IP_number
-d 0/0 –j
MASQUERADE
 Setting IP
Eth0  192.168.105.109 Bcast:192.168.105.255 Mask:255.255.255.0
Eth0:1  192.168.108.1 Bcast:192.168.108.255 Mask:255.255.255.0
 Setting Routing
# route add default gw 192.168.105.1
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Setting Setiap Client
 PC2
Setting IP
inet addr:192.168.108.10 Bcast:192.168.108.255 Mask:255.255.255.0
 PC3
Setting IP
inet addr:192.168.108.5 Bcast:192.168.108.255 Mask:255.255.255.0
 PC4
Setting IP
inet addr:192.168.108.20 Bcast:192.168.108.255 Mask:255.255.255.0
 Setting Gateway untuk PC2, PC3 & PC4
route add default gw 192.168.108.1
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Test Konektifitas
 Router PC 1
ping 192.168.108.10, ping 192.168.108.5, ping 192.168.108.20,
ping 192.168.105.1, ping 202.154.187.4
 PC 2
ping 192.168.105.109, ping 192.168.108.5, ping 192.168.108.20,
ping 192.168.105.1, ping 202.154.187.4
 PC 3
ping 192.168.105.109, ping 192.168.108.10, ping 192.168.108.20,
ping 192.168.105.1, ping 202.154.187.4
 PC 4
ping 192.168.105.109, ping 192.168.108.10, ping 192.168.108.5,
ping 192.168.105.1, ping 202.154.187.4
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Rule Firewall
 Setting memblok PC2 dan PC3 supaya tidak bisa
mengakses web dan FTP
#iptables –A FORWARD –m state –state NEW –m
multiport –s 192.168.108.5/24 –d 0/0 –p tcp –dport
www, -j REJECT
#iptables –A FORWARD –m state –state NEW –m
multiport –s 192.168.108.5/24 –d 0/0 –p tcp –dport
ftp, -j REJECT
#iptables –restore, iptables save
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Studi Kasus 2 - DMZ
 eth0 with 192.168.1.1 private IP
address - Internal LAN ~ Desktop
system
 eth1 with 202.54.1.1 public IP
address - WAN connected to ISP
router
 eth2 with 192.168.2.1 private IP
address - DMZ connected to Mail /
Web / DNS and other private
servers
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Routing traffic between public and DMZ server
 To set a rule for routing all incoming SMTP requests to a dedicated Mail
server at IP address 192.168.2.2 and port 25, network address translation
(NAT) calls a PREROUTING table to forward the packets to the proper
destination.
 This can be done with appropriate IPTABLES firewall rule to route traffic
between LAN to DMZ and public interface to DMZ. For example, all incoming
mail traffic from internet (202.54.1.1) can be send to DMZ mail server
(192.168.2.2) with the following iptables prerouting rule (assuming default
DROP all firewall policy):
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Routing traffic between public and DMZ server
### end init firewall .. Start DMZ stuff ####
# forward traffic between DMZ and LAN
iptables -A FORWARD -i eth0 -o eth2 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i eth2 -o eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
# forward traffic between DMZ and WAN servers SMTP, Mail etc
iptables -A FORWARD -i eth2 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i eth1 -o eth2 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
# Route incoming SMTP (port 25 ) traffic to DMZ server 192.168.2.2
iptables -t nat -A PREROUTING -p tcp -i eth1 -d 202.54.1.1 --dport 25 -j DNAT --to-destination 192.168.2.2
# Route incoming HTTP (port 80 ) traffic to DMZ server load balancer IP 192.168.2.3
iptables -t nat -A PREROUTING -p tcp -i eth1 -d 202.54.1.1 --dport 80 -j DNAT --to-destination 192.168.2.3
# Route incoming HTTPS (port 443 ) traffic to DMZ server reverse load balancer IP 192.168.2.4
iptables -t nat -A PREROUTING -p tcp -i eth1 -d 202.54.1.1 --dport 443 -j DNAT --to-destination 192.168.2.4
### End DMZ .. Add other rules ###
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 Where,
 -i eth1 : Wan network interface
 -d 202.54.1.1 : Wan public IP address
 --dport 25 : SMTP Traffic
 -j DNAT : DNAT target used set the destination address
of the packet with --to-destination
 --to-destination 192.168.2.2: Mail server ip address
(private IP)
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Multi port redirection
 You can also use multiport iptables module to matches a set of
source or destination ports. Up to 15 ports can be specified. For
example, route incoming HTTP (port 80 ) and HTTPS ( port 443)
traffic to WAN server load balancer IP 192.168.2.3:
 iptables -t nat -A PREROUTING -p tcp -i eth1 -d 202.54.1.1 -m
multiport --dport 80,443 -j DNAT --to-destination 192.168.2.3
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Studi Kasus 3 - Tugas
10.252.2.3/24
10.252.2.2/24
192.168.1.2/24
202.0.0.100/24
10.252.0.3/24
10.252.0.2/24
192.168.1.3/24
202.0.0.200/24
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SHOREWALL
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Shorewall
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Shorewall

Shorewall
tools for building a firewall
variable : interfaces, zones, rules

Konfigurasi Shorewall terdapat pada direktori
/etc/shorewall, yang minimal terdiri dari zone,
interfaces, rule, policy, dan shorewall.conf.
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Topologi Shorewall
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Zone
 Shorewall membagi jaringan menjadi beberapa zone yang dideskripsikan
di /etc/shorewall/zones
 diibaratkan komputer terdiri dari dua interfaces maka akan kita buat
menjadi zone net dan zone loc, sehingga konfigurasi /etc/shorewall/zones
sbb:
 #ZONE TYPE OPTIONS
IN
OUT
 #
OPTIONS
OPTIONS
 fw
firewall
 net
ipv4
 loc
ipv4

– Zone net adalah zona internet
– zone loc adalah zona lokal
– Zona fw mendeskripsikan mesin firewall itu sendiri.
 Penamaan zona terserah kepada kita.
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Interfaces
 Kemudian kita definisikan interfaces apa saja yang
akan kita terapkan zona tadi pada
/etc/shorewall/interfaces, konfigurasinya kira-kira
seperti :
#ZONE
INTERFACE
BROADCAST
net
eth0
detect
loc
eth1
detect
OPTIONS
norfc1918
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Rules
 Rules dalah kebijakan yang akan mengatur setiap koneksi yang masuk ke firewall, contoh
konfigurasi /etc/shorewall/rules :
 #ACTION
 Ping/ACCEPT
 ACCEPT
SOURCE
loc:192.168.0.1
$FW
 Web/ACCEPT
all
 SSH/ACCEPT
loc:192.168.0.1
DEST
PROTO
DEST PORT(S)
$FW
all
icmp
$FW
$FW
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Policy
 Policy adalah kebijakan umum yang diterapkan untuk hubungan masingmasing zone jika nanti tidak ada rule yang mendeskripsikannya , misalkan
:
 #SOURCE
DEST
POLICY
LOG LEVEL
 loc
net
ACCEPT
 net
all
DROP
info
 all
all
REJECT
info
LIMIT:BURST
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 Untuk instalasi berbasis debian biasanya file
/etc/shorewall kosong, file-file rule default dapat di copy
dari /usr/share/doc/shorewall/default-config serta
contoh-contoh konfigurasi juga ada pada
/usr/share/doc/shorewall/examples
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Installation
 Remove
:~# apt-get remove portmap
:~# apt-get remove nfs-common
:~# apt-get remove pidentd
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Installation
 Install Shorewall
:~# apt-get install shorewall
 Install documentation
:~# apt-get install shorewall-doc
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Configuration
 goto shorewall directory
:~# cd /etc/shorewall
 look inside
:/etc/shorewall# ls
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Configuration
 Change /etc/default/shorewall from
startup=0
to
startup=1
 # vim /etc/default/shorewall
change the startup
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Activate the firewall
 do this
# /etc/init.d/shorewall start
 watch your firewall
# iptables –nL | less
53
Configure shorewall dari webmin
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