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| spaceship_name = b"my_ship"
access_code = b"my_code"
md5_hash = hashlib.md5(spaceship_name + access_code).digest()
des = DES.new(md5_hash[0:8], DES.MODE_ECB)
enc = DES.new(md5_hash[0:8], DES.MODE_ECB)
def extract_hash(packet):
hash = bytes(packet[0x08:0x18])
check = packet[0:0x08] + b"\x00"*0x10 + des.decrypt(packet[0x18:])
if hash == hashlib.md5(check).digest():
log.success(f"hash check PASS")
log.warning(f"Packet: {check.hex()}")
else:
log.warning(f"hash check FAIL")
log.warning(f"packet: {packet.hex()}")
log.warning(f"Packet: {check.hex()}")
log.warning(f"hash: {hash.hex()}")
log.warning(f"Hash: {hashlib.md5(check).hexdigest()}")
def reg_spaceship():
io.recvuntil(b"spaceship name: ")
io.sendline(spaceship_name)
io.recvuntil(b"access code: ")
io.sendline(access_code)
io.recvuntil(b"enrolled!")
log.info(f"{md5_hash=}")
def auth(message):
io.recvuntil(b"entry...")
f1 = 0x01
f2 = 0x05
f3 = 0x01
f4 = 0
f5 = len(message)
f6 = libc.rand() & 0xff
payload = flat(
p8(f1),
p8(f2),
p8(f3),
p8(0x00),
p8(f4),
p8(0x00),
p8(f5),
p8(f6),
cyclic(0x10),
message
)
io.send(payload)
log.info(f"{payload=}")
io.recvline()
def calc_entropy(sign_bytes):
log.info(f"{sign_bytes.hex()=}")
entropy = bytearray([(~i & 0xff) for i in des.decrypt(sign_bytes)[::-1]])
log.info(f"{entropy.hex()=}")
return entropy
def sign(entropy):
io.recvuntil(b"Validating signature...")
f1 = 0x02
f2 = 0x4c
f3 = 0x01
f4 = 2
f5 = 8
f6 = libc.rand() & 0xff
msg = (bytearray([i^f6 for i in entropy]))
payload = flat(
p8(f1),
p8(f2),
p8(f3),
p8(0x00),
p8(f4),
p8(0x00),
p8(f5),
p8(f6),
b"\x00"*0x10,
msg
)
log.warning(f"packet: {payload.hex()}")
sign_hash = hashlib.md5(payload).digest()
payload = flat(
p8(f1),
p8(f2),
p8(f3),
p8(0x00),
p8(f4),
p8(0x00),
p8(f5),
p8(f6),
sign_hash,
enc.encrypt(msg)
)
log.warning(f"Packet: {payload.hex()}")
extract_hash(payload)
log.info(f"{payload=}")
if entropy == bytearray(i^f6 for i in des.decrypt(payload[0x18:])):
log.success(f"entropy check")
else:
log.warning("entropy fail")
io.send(payload)
delay = 0
authenticated = False
while delay <= 10 and not authenticated:
log.info(f"{delay=}")
io = start()
time_x = int(time.time() + delay)
libc.srand(time_x)
log.info(f"seeding with time: {time_x}")
delay += 1
io.recvuntil(b"Welcome to the intelligent portal in space!")
reg_spaceship()
io.recvuntil(b"special way!")
auth(b"")
msg = io.recvline()
log.info(msg)
if b"authenticated" in msg:
authenticated = True
log.success(f"authenticated!!!")
else:
log.warning(f"not authorised :(")
io.close()
continue
io.recvuntil(b"Leaking signature...")
io.recvline()
signature = io.recvn(0x20)
log.info([hex(i) for i in signature])
if signature[7] == (libc.rand() & 0xff):
log.success("seed matches!")
else:
log.warning("seed doesn't match")
extract_hash(signature)
entropy = calc_entropy(signature[:0x18])
log.info(f"{entropy=}")
sign(entropy)
io.recvuntil(b"coordinate...\n")
flag_packet = io.recvuntil(b"Coordinate", drop=True)
log.info([hex(i) for i in flag_packet])
extract_hash(flag_packet)
dec = DES.new(entropy, DES.MODE_ECB)
log.success(dec.decrypt(flag_packet[0x18:]))
io.recvline()
io.interactive()
|
