FIREWALL. Konsep Firewall

Transkripsi

1 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 hubungan /kegiatan suatu segmen pada membatasi jaringan pribadi dengan jaringan luar yang menolak bukan merupakan ruang lingkupnya 2

2 Konfigurasi Sederhana pc (jaringan local) <==> firewall <==> internet (jaringan lain) Boleh lewat mbak? Nih surat-suratnya Anak kecil ga boleh keluar.. sudah malam Firewall 3 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 4

3 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. 5 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 6

4 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 7 DMZ Configuration Place web servers in the DMZ network Only allow web ports (TCP ports 80 and 443) internet Firewall Web Server 8

5 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 Mas..yang merah gak boleh lewat lho internet Firewall Web Server 9 IPTABLES 10

6 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. 11 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 12

7 Prinsip Kerja Firewall Firewall Machine 13 Sintaks IPTABLES Opsi 1. -A, menambah satu aturan baru ditempatkan pada posisi terakhir iptables A INPUT D, menghapus rule iptables D INPUT 1 iptables D s I, menambah aturan baru penempatan bisa disisipkan sesuai nomor iptables I INPUT 3 s j ACCEPT 3. -R, mengganti rule iptables R INPUT 2 s s j ACCEPT 4. -F, menghapus seluruh rule iptables F 5. -L, melihat Rule iptables -L 14

8 Parameter -p [!] protocol, protokol yang akan dicek Iptables A INPUT p tcp - -s [!] address/[mask], memeriksa kecocokan sumber paket Iptables A INPUT s d [!] address/[mask], memerika kecocokan tujuan paket Iptables A INPUT d j target, menentukan nasib paket, target misal ACCEPT/DROP/REJECT Iptables A INPUT d 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 eth 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 16

9 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 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 dport 80 j DNAT todestination 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 17 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_irc 18

10 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 19 Packet Filtering Firewall 20

11 Packet Filtering Firewall 21 Circuit Level Gateway 22

12 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 d j ACCEPT #iptables A FORWARD s /24 d 0/0 p tcp --dport ftp, -j REJECT 23 Studi Kasus 1 Bangun Jaringan sendiri Install web server dan FTP Server pada jaringan Internet ( xxx) Setting memblok PC2 dan PC3 supaya tidak bisa mengakses web dan FTP 24

13 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 Setting IP Eth Bcast: Mask: Eth0: Bcast: Mask: Setting Routing # route add default gw MASQUERADE 25 Setting Setiap Client PC2 Setting IP inet addr: Bcast: Mask: PC3 Setting IP inet addr: Bcast: Mask: PC4 Setting IP inet addr: Bcast: Mask: Setting Gateway untuk PC2, PC3 & PC4 route add default gw

14 Test Konektifitas Router PC 1 PC 2 PC 3 PC 4 ping , ping , ping , ping , ping ping , ping , ping , ping , ping ping , ping , ping , ping , ping ping , ping , ping , ping , ping Rule Firewall Setting memblok PC2 dan PC3 supaya tidak bisa mengakses web dan FTP #iptables A FORWARD m state state NEW m multiport s /24 d 0/0 p tcp dport www, -j REJECT #iptables A FORWARD m state state NEW m multiport s /24 d 0/0 p tcp dport ftp, -j REJECT #iptables restore, iptables save 28

15 Studi Kasus 2 -DMZ eth0 with private IP address - Internal LAN ~ Desktop system eth1 with public IP address - WAN connected to ISP router eth2 with private IP address - DMZ connected to Mail / Web / DNS and other private servers 29 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 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 ( ) can be send to DMZ mail server ( ) with the following iptables prerouting rule (assuming default DROP all firewall policy): 30

16 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 iptables -t nat -A PREROUTING -p tcp -i eth1 -d dport 25 -j DNAT --to-destination # Route incoming HTTP (port 80 ) traffic to DMZ server load balancer IP iptables -t nat -A PREROUTING -p tcp -i eth1 -d dport 80 -j DNAT --to-destination # Route incoming HTTPS (port 443 ) traffic to DMZ server reverse load balancer IP iptables -t nat -A PREROUTING -p tcp -i eth1 -d dport 443 -j DNAT --to-destination ### End DMZ.. Add other rules ### 31 Where, -i eth1 : Wan network interface -d : 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 : Mail server ip address (private IP) 32

17 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 : iptables -t nat -A PREROUTING -p tcp -i eth1 -d m multiport --dport 80,443 -j DNAT --to-destination Studi Kasus 3 -Tugas DMZ Server ` Internet Internal Network IDS + Firewall Router 34

18 SHOREWALL 35 Shorewall 36

19 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. 37 Topologi Shorewall 38

20 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 net loc firewall ipv4 ipv4 Zone net adalah zona internet zone loc adalah zona lokal Zona fw mendeskripsikan mesin firewall itu sendiri. Penamaan zona terserah kepada kita

21 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 41 42

22 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: $FW ACCEPT $FW all icmp Web/ACCEPT all $FW SSH/ACCEPT loc: $FW 43 44

23 Policy Policy adalah kebijakan umum yang diterapkan untuk hubungan masingmasing 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 45 46

24 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 47 Installation Remove :~# apt-get remove portmap :~# apt-get remove nfs-common :~# apt-get remove pidentd 48

25 49 Installation Install Shorewall :~# apt-get install shorewall Install documentation :~# apt-get install shorewall-doc 50

26 Configuration goto shorewall directory :~# cd /etc/shorewall look inside :/etc/shorewall# ls 51 Configuration Change /etc/default/shorewall from to startup=0 startup=1 # vim /etc/default/shorewall change the startup 52

27 Activate the firewall do this # /etc/init.d/shorewall start watch your firewall # iptables nl less 53 Configure shorewall dari webmin 54