def build_extend_cell(handshake_type: str, x_bytes: bytes, gx_bytes: bytes, circ_id: int, onion_key, hop2_ip, hop2_port) -> Cell:
"""
The method used to build a Extend/Extend2 cell
:param handshake_type: The handshake type. TAP or ntor.
:param x_bytes: The diffie hellman private key as a bytes object
:param gx_bytes: The diffie hellman public key as a bytes object
:param circ_id: The circuit ID
:param onion_key: The onion key of the next hop used in hybrid_encrypt method
:param lspec: The link specifier as a string
:return: The extend Cell object
"""
client_h_data = CoreCryptoRSA.hybrid_encrypt(gx_bytes, onion_key)
nspec = 1 # Always keep this 1 to avoid going to hell
lspec = bytearray(IPv4Address(hop2_ip).packed) + pack('!H', int(hop2_port))
extend_cell_payload = RelayExtendPayload(nspec,
RelayExtendPayload.LSTYPE_ENUM['TLS_TCP_IPV4'],
RelayExtendPayload.LSTYPE_LSLEN_ENUM['TLS_TCP_IPV4'],
lspec,
CreateCellPayload.CREATE_HANDSHAKE_TYPE[handshake_type],
CreateCellPayload.CREATE_HANDSHAKE_LEN[handshake_type],
client_h_data)
relay_cell_payload = RelayCellPayload(RelayCellPayload.RELAY_CMD_ENUM['RELAY_EXTEND2'], 0, 0, b'', Cell.PAYLOAD_LEN - 11, extend_cell_payload)
relay_extend_cell = Cell(circ_id, Cell.CMD_ENUM['RELAY'], Cell.PAYLOAD_LEN, relay_cell_payload)
return relay_extend_cell
def parse_encoded_extend_cell(cell_bytes: bytes) -> Cell:
cell_tuple = Parser.parse_basic_cell(cell_bytes)
relay_cell_payload_tuple = Parser.parse_encoded_relay_cell(cell_bytes)
part_fmt_str1 = '=BBB'
part_tuple1 = unpack(part_fmt_str1, relay_cell_payload_tuple[5][0:3])
part_fmt_str2 = '=BBB' + str(part_tuple1[2]) + 's' + 'HH'
part_tuple2 = unpack(
part_fmt_str2,
relay_cell_payload_tuple[5][0:(3 + part_tuple1[2] + 2 + 2)])
fmt_str = '=BBB' + str(part_tuple1[2]) + 's' + 'HH' + str(
part_tuple2[5]) + 's'
relay_extend_payload_tuple = unpack(
fmt_str, relay_cell_payload_tuple[5][0:(3 + part_tuple1[2] + 2 +
2 + part_tuple2[5])])
h_data_fmt_str = '=' + str(CC.PK_PAD_LEN) + 's' + str(
CC.KEY_LEN) + 's' + str(
CC.PK_ENC_LEN - CC.PK_PAD_LEN - CC.KEY_LEN) + 's' + str(
CC.DH_LEN -
(CC.PK_ENC_LEN - CC.PK_PAD_LEN - CC.KEY_LEN)) + 's'
h_data_tuple = unpack(h_data_fmt_str, relay_extend_payload_tuple[6])
h_data = TapCHData(h_data_tuple[0], h_data_tuple[1], h_data_tuple[2],
h_data_tuple[3])
relay_extend_payload = RelayExtendPayload(
relay_extend_payload_tuple[0], relay_extend_payload_tuple[1],
relay_extend_payload_tuple[2], relay_extend_payload_tuple[3],
relay_extend_payload_tuple[4], relay_extend_payload_tuple[5],
h_data)
relay_cell_payload = RelayCellPayload(relay_cell_payload_tuple[0],
relay_cell_payload_tuple[1],
relay_cell_payload_tuple[2],
relay_cell_payload_tuple[3],
relay_cell_payload_tuple[4],
relay_extend_payload)
extend_cell = Cell(cell_tuple[0], cell_tuple[1], cell_tuple[2],
relay_cell_payload)
return extend_cell