Kahanan
Dina libur. Aku ngombe kopi. Siswa kasebut nyiyapake sambungan VPN ing antarane rong titik lan ilang. Aku mriksa: pancen ana trowongan, nanging ora ana lalu lintas ing trowongan. Siswa ora mangsuli telpon.
Aku sijine ketel lan nyilem menyang S-Terra Gateway ngatasi masalah. Aku nuduhake pengalaman lan metodologi.
Data sumber
Loro situs sing dipisahake sacara geografis disambungake karo trowongan GRE. GRE kudu dienkripsi:
Aku mriksa fungsi terowongan GRE. Kanggo nindakake iki, aku mbukak ping saka piranti R1 menyang antarmuka GRE piranti R2. Iki minangka lalu lintas target kanggo enkripsi. Ora ana wangsulan:
root@R1:~# ping 1.1.1.2 -c 4
PING 1.1.1.2 (1.1.1.2) 56(84) bytes of data.
--- 1.1.1.2 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3057msAku ndeleng log ing Gate1 lan Gate2. Log kasebut kanthi seneng nglaporake manawa terowongan IPsec kasil diluncurake, ora ana masalah:
root@Gate1:~# cat /var/log/cspvpngate.log
Aug 5 16:14:23 localhost vpnsvc: 00100119 <4:1> IPSec connection 5 established, traffic selector 172.17.0.1->172.16.0.1, proto 47, peer 10.10.10.251, id "10.10.10.251", Filter
IPsec:Protect:CMAP:1:LIST, IPsecAction IPsecAction:CMAP:1, IKERule IKERule:CMAP:1Ing statistik terowongan IPsec ing Gate1 aku weruh yen pancen ana trowongan, nanging counter RΡvd direset menyang nol:
root@Gate1:~# sa_mgr show
ISAKMP sessions: 0 initiated, 0 responded
ISAKMP connections:
Num Conn-id (Local Addr,Port)-(Remote Addr,Port) State Sent Rcvd
1 3 (10.10.10.251,500)-(10.10.10.252,500) active 1070 1014
IPsec connections:
Num Conn-id (Local Addr,Port)-(Remote Addr,Port) Protocol Action Type Sent Rcvd
1 3 (172.16.0.1,*)-(172.17.0.1,*) 47 ESP tunn 480 0Aku alangan S-Terra kaya iki: Aku katon kanggo ngendi paket target ilang ing path saka R1 kanggo R2. Ing proses (spoiler) aku bakal nemokake kesalahan.
Ngatasi masalah
Langkah 1. Apa Gate1 ditampa saka R1
Aku nggunakake sniffer paket sing dibangun ing - tcpdump. Aku miwiti sniffer ing antarmuka internal (Gi0/1 ing notasi kaya Cisco utawa eth1 ing notasi Debian OS):
root@Gate1:~# tcpdump -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 262144 bytes
14:53:38.879525 IP 172.16.0.1 > 172.17.0.1: GREv0, key=0x1, length 92: IP 1.1.1.1 > 1.1.1.2: ICMP echo request, id 2083, seq 1, length 64
14:53:39.896869 IP 172.16.0.1 > 172.17.0.1: GREv0, key=0x1, length 92: IP 1.1.1.1 > 1.1.1.2: ICMP echo request, id 2083, seq 2, length 64
14:53:40.921121 IP 172.16.0.1 > 172.17.0.1: GREv0, key=0x1, length 92: IP 1.1.1.1 > 1.1.1.2: ICMP echo request, id 2083, seq 3, length 64
14:53:41.944958 IP 172.16.0.1 > 172.17.0.1: GREv0, key=0x1, length 92: IP 1.1.1.1 > 1.1.1.2: ICMP echo request, id 2083, seq 4, length 64Aku weruh sing Gate1 nampa paket GRE saka R1. Aku nerusake.
Langkah 2. Apa Gate1 karo paket GRE
Nggunakake sarana klogview aku bisa ndeleng apa sing kedadeyan karo paket GRE ing driver S-Terra VPN:
root@Gate1:~# klogview -f 0xffffffff
filtration result for out packet 172.16.0.1->172.17.0.1, proto 47, len 112, if eth0: chain 4 "IPsecPolicy:CMAP", filter 8, event id IPsec:Protect:CMAP:1:LIST, status PASS
encapsulating with SA 31: 172.16.0.1->172.17.0.1, proto 47, len 112, if eth0
passed out packet 10.10.10.251->10.10.10.252, proto 50, len 160, if eth0: encapsulated
Aku weruh sing target GRE lalu lintas (proto 47) 172.16.0.1 -> 172.17.0.1 teka ing aturan enkripsi LIST ing peta crypto CMAP lan encapsulated. Sabanjure, paket kasebut dialihake (passed out). Ora ana lalu lintas respon ing output klogview.
Aku mriksa dhaptar akses ing piranti Gate1. Aku ndeleng dhaptar dhaptar akses siji, sing nemtokake lalu lintas target kanggo enkripsi, tegese aturan firewall ora dikonfigurasi:
Gate1#show access-lists
Extended IP access list LIST
10 permit gre host 172.16.0.1 host 172.17.0.1Kesimpulan: masalah ora karo piranti Gate1.
Liyane babagan klogview
Driver VPN nangani kabeh lalu lintas jaringan, ora mung lalu lintas sing kudu dienkripsi. Iki minangka pesen sing katon ing klogview yen driver VPN ngolah lalu lintas jaringan lan dikirim tanpa enkripsi:
root@R1:~# ping 172.17.0.1 -c 4root@Gate1:~# klogview -f 0xffffffff
filtration result for out packet 172.16.0.1->172.17.0.1, proto 1, len 84, if eth0: chain 4 "IPsecPolicy:CMAP": no match
passed out packet 172.16.0.1->172.17.0.1, proto 1, len 84, if eth0: filteredAku weruh sing lalu lintas ICMP (proto 1) 172.16.0.1-> 172.17.0.1 ora klebu (ora cocog) ing aturan enkripsi kertu crypto CMAP. Paket kasebut diarahake (lulus) kanthi teks sing jelas.
Langkah 3. Apa sing ditampa Gate2 saka Gate1
Aku miwiti sniffer ing antarmuka WAN (eth0) Gate2:
root@Gate2:~# tcpdump -i eth0
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
16:05:45.104195 IP 10.10.10.251 > 10.10.10.252: ESP(spi=0x30088112,seq=0x1), length 140
16:05:46.093918 IP 10.10.10.251 > 10.10.10.252: ESP(spi=0x30088112,seq=0x2), length 140
16:05:47.117078 IP 10.10.10.251 > 10.10.10.252: ESP(spi=0x30088112,seq=0x3), length 140
16:05:48.141785 IP 10.10.10.251 > 10.10.10.252: ESP(spi=0x30088112,seq=0x4), length 140Aku weruh sing Gate2 nampa paket ESP saka Gate1.
Langkah 4. Apa Gate2 karo paket ESP
Aku miwiti utilitas klogview ing Gate2:
root@Gate2:~# klogview -f 0xffffffff
filtration result for in packet 10.10.10.251->10.10.10.252, proto 50, len 160, if eth0: chain 17 "FilterChain:L3VPN", filter 21, status DROP
dropped in packet 10.10.10.251->10.10.10.252, proto 50, len 160, if eth0: firewall
Aku weruh sing paket ESP (proto 50) dropped (DROP) dening aturan firewall (L3VPN). Aku mesthekake yen Gi0/0 pancen duwe dhaptar akses L3VPN sing dilampirake:
Gate2#show ip interface gi0/0
GigabitEthernet0/0 is up, line protocol is up
Internet address is 10.10.10.252/24
MTU is 1500 bytes
Outgoing access list is not set
Inbound access list is L3VPNAku nemokake masalah kasebut.
Langkah 5. Apa salah karo dhaptar akses
Aku ndeleng apa dhaptar akses L3VPN:
Gate2#show access-list L3VPN
Extended IP access list L3VPN
10 permit udp host 10.10.10.251 any eq isakmp
20 permit udp host 10.10.10.251 any eq non500-isakmp
30 permit icmp host 10.10.10.251 anyAku weruh sing ISAKMP paket diijini, supaya tunnel IPsec ditetepake. Nanging ora ana aturan sing bisa digunakake kanggo ESP. Jebul muride bingung icmp lan esp.
Ngowahi dhaptar akses:
Gate2(config)#
ip access-list extended L3VPN
no 30
30 permit esp host 10.10.10.251 anyLangkah 6. Priksa fungsi
Kaping pisanan, aku priksa manawa dhaptar akses L3VPN bener:
Gate2#show access-list L3VPN
Extended IP access list L3VPN
10 permit udp host 10.10.10.251 any eq isakmp
20 permit udp host 10.10.10.251 any eq non500-isakmp
30 permit esp host 10.10.10.251 anySaiki aku miwiti lalu lintas target saka piranti R1:
root@R1:~# ping 1.1.1.2 -c 4
PING 1.1.1.2 (1.1.1.2) 56(84) bytes of data.
64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=35.3 ms
64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=3.01 ms
64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=2.65 ms
64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=2.87 ms
--- 1.1.1.2 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3006ms
rtt min/avg/max/mdev = 2.650/10.970/35.338/14.069 mskamenangan. Trowongan GRE wis ditetepake. Counter lalu lintas mlebu ing statistik IPsec ora nol:
root@Gate1:~# sa_mgr show
ISAKMP sessions: 0 initiated, 0 responded
ISAKMP connections:
Num Conn-id (Local Addr,Port)-(Remote Addr,Port) State Sent Rcvd
1 3 (10.10.10.251,500)-(10.10.10.252,500) active 1474 1350
IPsec connections:
Num Conn-id (Local Addr,Port)-(Remote Addr,Port) Protocol Action Type Sent Rcvd
1 4 (172.16.0.1,*)-(172.17.0.1,*) 47 ESP tunn 1920 480Ing gateway Gate2, ing output klogview, pesen katon yen lalu lintas target 172.16.0.1-> 172.17.0.1 kasil didekripsi (PASS) dening aturan LIST ing peta crypto CMAP:
root@Gate2:~# klogview -f 0xffffffff
filtration result for in packet 172.16.0.1->172.17.0.1, proto 47, len 112, if eth0: chain 18 "IPsecPolicy:CMAP", filter 25, event id IPsec:Protect:CMAP:1:LIST, status PASS
passed in packet 172.16.0.1->172.17.0.1, proto 47, len 112, if eth0: decapsulatedHasil
Siswa ngrusak dina libur.
Ati-ati karo aturan ME.
Insinyur Anonim
t.me/anonymous_engineer
Source: www.habr.com