2. 2
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
3. 3
Konfigurasi Sederhana
pc (jaringan local) <==> firewall <==> internet (jaringan lain)
Firewall
Boleh lewat mbak ?
Nih surat-suratnya
Anak kecil ga boleh
keluar.. sudah malam
4. 4
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
5. 5
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.
8. 8
Tipe Firewall
Berdasarkan mekanisme cara kerja :
Packet Filtering
– Memfilter paket berdasarkan sumber, tujuan dan atribut paket (filter berdasar
IP dan Port). Yang difilter IP, TCP, UDP, and ICMP headers and port number
Application Level
– Biasa disebut proxy firewall, filter bisa berdasarkan content paket
Circuit Level Gateway
– Filter berdasarkan sesi komunikasi, dengan pengawasan sesi handshake.
– Terdapat sesi NEW/ESTABLISH
Statefull Multilayer Inspection Firewall
– Kombinasi dari ketiga tipe firewall diatas
9. 9
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
Internet
Automatically Accept Connection Attempt
Router
Automatically Deny Connection Attempt
10. 10
DMZ Configuration
Place web servers in the “DMZ” network
Only allow web ports (TCP ports 80 and 443)
internet
Firewall
Web Server
11. 11
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
Patching is not convenient
Firewall
Web Server
internet
Mas ..yang
merah gak
boleh lewat
lho
13. 13
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.
14. 14
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
16. 16
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
17. 17
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 ….
18. 18
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
19. 19
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 –to-
destination 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
26. 26
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
30. 30
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
31. 31
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
32. 32
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):
33. 33
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 ###
34. 34
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)
35. 35
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
36. 36
Studi Kasus 3 - Tugas
10.252.2.3/24
192.168.1.3/24
10.252.0.2/24
10.252.2.2/24
10.252.0.3/24
192.168.1.2/24 202.0.0.100/24
202.0.0.200/24
39. 39
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.
41. 41
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.
43. 43
Interfaces
Kemudian kita definisikan interfaces apa saja yang
akan kita terapkan zona tadi pada
/etc/shorewall/interfaces, konfigurasinya kira-kira
seperti :
#ZONE INTERFACE BROADCAST OPTIONS
net eth0 detect norfc1918
loc eth1 detect
45. 45
Rules
Rules dalah kebijakan yang akan mengatur setiap koneksi yang masuk ke firewall, contoh
konfigurasi /etc/shorewall/rules :
#ACTION SOURCE DEST PROTO DEST PORT(S)
Ping/ACCEPT loc:192.168.0.1 $FW
ACCEPT $FW all icmp
Web/ACCEPT all $FW
SSH/ACCEPT loc:192.168.0.1 $FW
47. 47
Policy
Policy adalah kebijakan umum yang diterapkan untuk hubungan masing-
masing zone jika nanti tidak ada rule yang mendeskripsikannya , misalkan
:
#SOURCE DEST POLICY LOG LEVEL LIMIT:BURST
loc net ACCEPT
net all DROP info
all all REJECT info
49. 49
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
