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FIREWALL
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
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Konfigurasi Sederhana
pc (jaringan local) <==> firewall <==> internet (jaringan lain)
Firewall Boleh lewat mbak ?
Nih surat-suratnya
Anak kecil ga boleh keluar.. sudah malam
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
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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.
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
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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
Internet
Automatically Accept Connection Attempt
Router
Automatically Deny Connection Attempt
DMZ Configuration
Place web servers in the “DMZ” network Only allow web ports (TCP ports 80 and 443)
internet
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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 Patching is not convenient
Firewall Web Server internet Mas ..yang merah gak boleh lewat lho
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.
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
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 -.
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 –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
Firewall Option
# 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_irc19
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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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
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
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
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
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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
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 ###
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
Studi Kasus 3 - Tugas
DMZ Server
Internet
Router `
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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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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 OPTIONS net eth0 detect norfc1918 loc eth1 detect
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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
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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
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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
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
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Configuration
goto shorewall directory
:~# cd /etc/shorewall
look inside
:/etc/shorewall# ls
Configuration
Change /etc/default/shorewall from
startup=0
to
startup=1
# vim /etc/default/shorewall
change the startup
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