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This commit is contained in:
Dongho Kim
2024-11-01 00:07:17 +09:00
parent 65986c1ca5
commit 2858c522ef
5 changed files with 197 additions and 138 deletions
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102
Task pwn02/week02/easy/server.py
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@ -12,9 +12,10 @@ from scapy.sendrecv import send, sniff
log = logging.getLogger(__name__)
TCP_CLIENTS = {} # ((IP, port) -> [sent_packets])
SERVER_IP = "127.0.0.1" # TODO
# SERVER_IP = '131.159.15.68' # TODO
SERVER_IP = '127.0.0.1'
SERVER_PORT = 20102
COOKIE_SECRET = "TASTY_COOKIES123"
COOKIE_SECRET = 'TASTY_COOKIES123'
INITIAL_SEQ = 1337
@ -22,115 +23,116 @@ INITIAL_SEQ = 1337
# converting the hex digest to an integer
# The cookie is then this result modulo 2^32 to fit the 32-bit field
def generate_syn_cookie(client_ip: str, client_port: int, server_secret: str):
hash_input = f"{client_ip}{client_port}{server_secret}".encode()
hash_input = f'{client_ip}{client_port}{server_secret}'.encode()
return int(hashlib.sha256(hash_input).hexdigest(), 16) % (2**32)
def get_initial_syn(ip, port, ack) -> Packet:
ip = IP(dst=ip)
syn = TCP(sport=SERVER_PORT, dport=port, flags="SA", seq=INITIAL_SEQ, ack=ack)
syn = TCP(sport=SERVER_PORT, dport=port, flags='SA', seq=INITIAL_SEQ, ack=ack)
return ip / syn
def get_rst(ip, port, ack) -> Packet:
ip = IP(dst=ip)
syn = TCP(sport=SERVER_PORT, dport=port, flags="R", seq=INITIAL_SEQ, ack=ack)
syn = TCP(sport=SERVER_PORT, dport=port, flags='R', seq=INITIAL_SEQ, ack=ack)
return ip / syn
def handle_packet(packet: Packet):
print("Received a packet on the server:", packet.summary())
if packet.haslayer(TCP) and packet[TCP].dport == SERVER_PORT:
if "F" in packet[TCP].flags or "R" in packet[TCP].flags:
print("Received FIN or Reset packet:", packet.summary())
if 'F' in packet[TCP].flags or 'R' in packet[TCP].flags:
print('Received FIN or Reset packet:', packet.summary())
if (packet[IP].src, packet[TCP].sport) in TCP_CLIENTS:
del TCP_CLIENTS[(packet[IP].src, packet[TCP].sport)]
return
print("Received packet:", packet.summary())
print('Received packet:', packet.summary())
# Extract the TCP layer
tcp_layer = packet[TCP]
src_ip = packet[IP].src
src_port = tcp_layer.sport
seq = packet[TCP].seq
ack = packet[TCP].ack
expected_cookie = generate_syn_cookie(SERVER_IP, SERVER_PORT, COOKIE_SECRET)
if (src_ip, src_port) not in TCP_CLIENTS:
print("New client:", src_ip, src_port, seq)
print('New client:', src_ip, src_port, seq)
# first packet from client to initiate handshake
if (not "S" in packet[TCP].flags) or (
not packet[TCP].seq == expected_cookie
):
print(f"Invalid cookie {seq}, expected {expected_cookie}")
if (not 'S' in packet[TCP].flags) or (not packet[TCP].seq == expected_cookie):
print(f'Invalid cookie {seq}, expected {expected_cookie}')
rst = get_rst(src_ip, src_port, seq)
send(rst)
else:
else:
TCP_CLIENTS[(src_ip, src_port)] = 1
initial_syn = get_initial_syn(src_ip, src_port, seq)
print(f"Cookie {expected_cookie} and packet is correct")
print(f"Sending packet: {initial_syn.summary()}")
print(f'Cookie {expected_cookie} and packet is correct')
print(f'Sending packet: {initial_syn.summary()}')
send(initial_syn)
else:
if (
("S" in packet[TCP].flags)
or (not seq == expected_cookie)
or (not ack == INITIAL_SEQ)
):
print(f"Invalid cookie {seq}, expected {expected_cookie}")
if ('S' in packet[TCP].flags):
print("S in flag")
if (not ack == INITIAL_SEQ):
print(ack)
print("acak and seq different")
if (not seq == expected_cookie):
print("seq cookie")
if ('S' in packet[TCP].flags) or (not seq == expected_cookie) or (not ack == INITIAL_SEQ):
print(f'Invalid cookie {seq}, expected {expected_cookie}')
rst = get_rst(src_ip, src_port, seq)
send(rst)
else:
print(f"Cookie {expected_cookie} and packet is again correct")
flag = subprocess.check_output("flag").decode()
print(f'Cookie {expected_cookie} and packet is again correct')
flag = "ALL GOOD BROTHER"
ip = IP(dst=src_ip)
syn_ack = (
TCP(
sport=SERVER_PORT,
dport=src_port,
flags="A",
seq=ack,
ack=seq,
)
/ flag
)
syn_ack = TCP(
sport=SERVER_PORT,
dport=src_port,
flags='A',
seq=ack,
ack=seq,
) / flag
send(ip / syn_ack)
del TCP_CLIENTS[(src_ip, src_port)]
# Function to start the packet sniffing
def start_sniffing():
print("Starting TCP server on port:", SERVER_PORT)
print('Starting TCP server on port:', SERVER_PORT)
sniff(
filter=f"tcp port {SERVER_PORT}",
filter=f'tcp port {SERVER_PORT}',
prn=handle_packet,
store=False,
monitor=True,
iface="lo",
iface='lo',
)
# Run the server in a separate thread
def main():
conf.use_pcap = False
print("Server is starting...") # Added print statement
server_thread = threading.Thread(target=start_sniffing)
server_thread.start()
if __name__ == "__main__":
if __name__ == '__main__':
logging.basicConfig(
level=logging.INFO,
format="%(asctime)s %(levelname)s [%(module)s:%(lineno)d] %(message)s",
format='%(asctime)s %(levelname)s [%(module)s:%(lineno)d] %(message)s',
)
# "INFO:asyncio:poll took 25.960 seconds" is annyoing
logging.getLogger("asyncio").setLevel(logging.WARNING)
logging.getLogger('asyncio').setLevel(logging.WARNING)
main()