====== Cisco: Context-based access control (CBAC) ====== CBAC (Context-Based Access Control) to funkcja zapory stanu (stateful firewall) dostępna na routerach Cisco, która analizuje ruch przechodzący przez router, tworząc dynamiczne listy ACL na podstawie wykrytych sesji. Umożliwia filtrowanie ruchu na podstawie stanu połączenia, a nie tylko adresów i portów. ===== Jak działa CBAC ===== * CBAC monitoruje sesje warstwy 4 (TCP, UDP, ICMP) * Analizuje i śledzi stan połączeń w obu kierunkach * Dynamicznie dodaje wpisy do list ACL, aby umożliwić ruch powrotny (np. odpowiedzi na zapytania) * Chroni przed nieautoryzowanym dostępem i niektórymi typami ataków (np. DoS) ===== Zalety ===== * Dynamiczne otwieranie portów tylko dla aktywnych połączeń * Lepsza kontrola niż standardowe ACL * Możliwość logowania i alertowania ===== Podstawowa konfiguracja CBAC ===== === 1. Zdefiniuj inspekcję protokołów === ip inspect name CBAC_INSPECT http ip inspect name CBAC_INSPECT ftp ip inspect name CBAC_INSPECT tcp ip inspect name CBAC_INSPECT udp === 2. Przypisz inspekcję do interfejsu === *Ruch wychodzący (gdzie inicjowane są połączenia)* interface FastEthernet0/0 ip inspect CBAC_INSPECT out === 3. Skonfiguruj ACL na interfejsie wejściowym (np. od strony Internetu) === access-list 100 permit tcp any any established access-list 100 permit icmp any any echo-reply access-list 100 deny ip any any interface FastEthernet0/1 ip access-group 100 in === 4. (Opcjonalnie) Włącz logowanie CBAC === ip inspect audit-trail ip inspect log drop-pkt ip inspect log tcp syn ===== Przydatne polecenia do diagnostyki ===== show ip inspect sessions show ip inspect config debug ip inspect ===== Uwagi końcowe ===== * CBAC działa najlepiej na ruchu inicjowanym z wewnątrz sieci * Może obciążać router przy dużym ruchu – warto monitorować wydajność * W nowoczesnych konfiguracjach zastępowany często przez **Zone-Based Firewall (ZBF)** ===== Przykład ===== {{.:pasted:20250528-164132.png}} test:\\ R1#ping 2.0.0.254 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.0.0.254, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) R1#telnet 2.0.0.254 Trying 2.0.0.254 ... Open User Access Verification Password: R3> konfiguracja R1:\\ Building configuration... Current configuration : 1303 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R1 ! boot-start-marker boot-end-marker ! ! no aaa new-model memory-size iomem 5 no ip icmp rate-limit unreachable ip cef ! ! ! ! no ip domain lookup ! multilink bundle-name authenticated ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! archive log config hidekeys ! ! ! ! ip tcp synwait-time 5 ! ! ! ! interface FastEthernet0/0 ip address 1.0.0.254 255.255.255.0 duplex auto speed auto ! interface Serial0/0 no ip address shutdown clock rate 2000000 ! interface FastEthernet0/1 no ip address shutdown duplex auto speed auto ! interface Serial0/1 no ip address shutdown clock rate 2000000 ! interface Serial0/2 no ip address shutdown clock rate 2000000 ! interface FastEthernet1/0 no ip address shutdown duplex auto speed auto ! interface FastEthernet2/0 no ip address shutdown duplex auto speed auto ! ip forward-protocol nd ip route 0.0.0.0 0.0.0.0 1.0.0.1 ! ! no ip http server no ip http secure-server ! no cdp log mismatch duplex ! ! ! ! ! ! control-plane ! ! ! ! ! ! ! ! ! ! line con 0 exec-timeout 0 0 privilege level 15 logging synchronous line aux 0 exec-timeout 0 0 privilege level 15 logging synchronous line vty 0 4 login ! ! end konfiguracja R2:\\ Building configuration... Current configuration : 1445 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R2 ! boot-start-marker boot-end-marker ! ! no aaa new-model memory-size iomem 5 no ip icmp rate-limit unreachable ip cef ! ! ! ! no ip domain lookup ip inspect name TELNET_ONLY telnet ! multilink bundle-name authenticated ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! archive log config hidekeys ! ! ! ! ip tcp synwait-time 5 ! ! ! ! interface FastEthernet0/0 ip address 1.0.0.1 255.255.255.0 ip inspect TELNET_ONLY out duplex auto speed auto ! interface Serial0/0 no ip address shutdown clock rate 2000000 ! interface FastEthernet0/1 ip address 2.0.0.1 255.255.255.0 ip access-group 100 in duplex auto speed auto ! interface Serial0/1 no ip address shutdown clock rate 2000000 ! interface Serial0/2 no ip address shutdown clock rate 2000000 ! interface FastEthernet1/0 no ip address shutdown duplex auto speed auto ! interface FastEthernet2/0 no ip address shutdown duplex auto speed auto ! ip forward-protocol nd ! ! no ip http server no ip http secure-server ! access-list 100 permit tcp any any established access-list 100 deny ip any any no cdp log mismatch duplex ! ! ! ! ! ! control-plane ! ! ! ! ! ! ! ! ! ! line con 0 exec-timeout 0 0 privilege level 15 logging synchronous line aux 0 exec-timeout 0 0 privilege level 15 logging synchronous line vty 0 4 login ! ! end konfiguracja R3:\\ Building configuration... Current configuration : 1342 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R3 ! boot-start-marker boot-end-marker ! enable password cisco ! no aaa new-model memory-size iomem 5 no ip icmp rate-limit unreachable ip cef ! ! ! ! no ip domain lookup ! multilink bundle-name authenticated ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! archive log config hidekeys ! ! ! ! ip tcp synwait-time 5 ! ! ! ! interface FastEthernet0/0 ip address 2.0.0.254 255.255.255.0 duplex auto speed auto ! interface Serial0/0 no ip address shutdown clock rate 2000000 ! interface FastEthernet0/1 no ip address shutdown duplex auto speed auto ! interface Serial0/1 no ip address shutdown clock rate 2000000 ! interface Serial0/2 no ip address shutdown clock rate 2000000 ! interface FastEthernet1/0 no ip address shutdown duplex auto speed auto ! interface FastEthernet2/0 no ip address shutdown duplex auto speed auto ! ip forward-protocol nd ip route 0.0.0.0 0.0.0.0 2.0.0.1 ! ! no ip http server no ip http secure-server ! no cdp log mismatch duplex ! ! ! ! ! ! control-plane ! ! ! ! ! ! ! ! ! ! line con 0 exec-timeout 0 0 privilege level 15 logging synchronous line aux 0 exec-timeout 0 0 privilege level 15 logging synchronous line vty 0 4 password cisco login ! ! end