mischard

unbefleckte_empfangnis

hxp_39c3

Task: establish a TCP connection to a service that blocks all SYN packets. Solution: brute-force SYN cookies by sending ACK packets with random sequence numbers, exploiting the modified MAX_SYNCOOKIE_AGE (1111 > 255) which makes the 8-bit age check always pass.

$ ls tags/ techniques/

brute_force iptables network tcp syn_cookies kernel_exploitation raw_sockets linux_kernel tcp_handshake virgin_birth

SYN cookie validation bypass via MAX_SYNCOOKIE_AGE overflowTCP ACK brute-force with random sequence numbersRaw socket packet craftingRST packet blocking to maintain connection

Analysis

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$ python3 exploit.py --target 192.168.1.1 --port 8080
[*] Connecting to target...
[+] Shell obtained!

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