실습> IP 헤더에서 TTL 값 변경하기
o mangle table 의 TTL값 변경하기
Attacker ~# iptables -t mangle -nL
| Chain PREROUTING (policy ACCEPT) target prot opt source destination Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain POSTROUTING (policy ACCEPT) target prot opt source destination |
Attacker ~# ping -c 5 192.168.108.2
PING 192.168.108.2 (192.168.108.2) 56(84) bytes of data.
64 bytes from 192.168.108.2: icmp_seq=1 ttl=128 time=0.289 ms
64 bytes from 192.168.108.2: icmp_seq=2 ttl=128 time=0.260 ms
64 bytes from 192.168.108.2: icmp_seq=3 ttl=128 time=0.201 ms
64 bytes from 192.168.108.2: icmp_seq=4 ttl=128 time=0.183 ms
64 bytes from 192.168.108.2: icmp_seq=5 ttl=128 time=0.232 ms
--- 192.168.108.2 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4184ms
rtt min/avg/max/mdev = 0.183/0.233/0.289/0.038 ms
Attacker ~# iptables -t mangle -A PREROUTING -j TTL --ttl-set 10
Attacker ~# ping -c 5 192.168.108.2
PING 192.168.108.2 (192.168.108.2) 56(84) bytes of data.
64 bytes from 192.168.108.2: icmp_seq=1 ttl=10 time=0.478 ms
64 bytes from 192.168.108.2: icmp_seq=2 ttl=10 time=0.210 ms
64 bytes from 192.168.108.2: icmp_seq=3 ttl=10 time=0.232 ms
64 bytes from 192.168.108.2: icmp_seq=4 ttl=10 time=0.251 ms
64 bytes from 192.168.108.2: icmp_seq=5 ttl=10 time=0.252 ms
--- 192.168.108.2 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4142ms
rtt min/avg/max/mdev = 0.210/0.284/0.478/0.097 ms
Attacker ~#
Attacker ~# iptables -t mangle -nL
| Chain PREROUTING (policy ACCEPT) target prot opt source destination TTL all -- 0.0.0.0/0 0.0.0.0/0 TTL set to 10 Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain POSTROUTING (policy ACCEPT) target prot opt source destination |
Attacker ~# iptables -t mangle -nvL
| Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination 43 2668 TTL all -- * * 0.0.0.0/0 0.0.0.0/0 TTL set to 10 Chain INPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination |
Attacker ~# iptables -t mangle -A POSTROUTING -j TTL --ttl-set 3
Attacker ~# iptables -t mangle -nL
| Chain PREROUTING (policy ACCEPT) target prot opt source destination TTL all -- 0.0.0.0/0 0.0.0.0/0 TTL set to 10 Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain POSTROUTING (policy ACCEPT) target prot opt source destination TTL all -- 0.0.0.0/0 0.0.0.0/0 TTL set to 3 |
TTL을 3으로 변경했기 때문에 8.8.8.8까지 갈 수 없다.
Attacker ~# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
^C
--- 8.8.8.8 ping statistics ---
25 packets transmitted, 0 received, 100% packet loss, time 25119ms
Attacker ~# iptables -t mangle -F
Attacker ~# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=128 time=46.7 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=128 time=46.8 ms
^C
--- 8.8.8.8 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1019ms
rtt min/avg/max/mdev = 46.703/46.731/46.759/0.028 ms
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