iodine (IP over DNS tunnel)

iodine 可以透過 DNS Server 來建立 IP tunnel
它可以把 traffic 封裝成一般的 DNS 封包 (query and response)

Linux Server
run: ./iodined -f 10.0.0.1 test.asdf
Enter a password

Linux Client
run: ./iodine -f 192.168.0.1 test.asdf (Replace 192.168.0.1 with the server's ip address)
Enter the same password

正常的話 Client 端應該就會取得 10.0.0.2 (dns0), 可以 ping 得到 Server 端 10.0.0.1
# ifconfig dns0
dns0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:10.0.0.2 P-t-P:10.0.0.2 Mask:255.255.255.0
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1130 Metric:1
RX packets:20 errors:0 dropped:0 overruns:0 frame:0
TX packets:19 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:1352 (1.3 KiB) TX bytes:1332 (1.3 KiB)

# ping -c5 10.0.0.1
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=2.56 ms
64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=2.54 ms
64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=2.55 ms
64 bytes from 10.0.0.1: icmp_seq=4 ttl=64 time=2.50 ms
64 bytes from 10.0.0.1: icmp_seq=5 ttl=64 time=2.62 ms

--- 10.0.0.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3999ms
rtt min/avg/max/mdev = 2.504/2.556/2.621/0.037 ms

其中 test.asdf 是 Domain, 若 Client 端是直連 Server 端, 這個 Domain 可任意取名,
若 Client 端是透過其他 DNS 再 Relay 過來, 這個 Domain 必需合法, 而且執行 iodined 的 Server 端需被 NS 指向
有些 DNS Server 會有 rate limit 以降低被攻擊時的傷害程度, 像這些有保護的 DNS Server 就無法用來建立 tunnel
若是使用 Win32 版本, 需先裝 OpenVPN, 它會建立一個 TAP 區域連線