def build_extended_cell(y, gy, streamID: int, circ_id: int, gx: str, recognized) -> Cell:
"""
The method to build the extended Cell object
:param y:
:param gy:
:param streamID:
:param circ_id:
:param gx:
:param recognized:
:return: The Extended Cell
"""
gxy = CoreCryptoDH.compute_dh_shared_key(y, gx)
kdf_dict = CoreCryptoRSA.kdf_tor(gxy)
server_h_data = TapSHData(gy, kdf_dict['KH'])
# Construct extended2 payload
extended_cell_payload_relay = RelayExtendedPayload(RelayExtendedPayload.TAP_S_HANDSHAKE_LEN, server_h_data)
# Calculate digest from the extended2 payload
payload_dict = {
'HLEN': extended_cell_payload_relay.HLEN,
'HDATA': extended_cell_payload_relay.HDATA
}
digest = CoreCryptoMisc.calculate_digest(payload_dict)
# Construct the Relay cell with extended2 payload which is the payload for the Cell class
extended_cell_payload = RelayCellPayload(RelayCellPayload.RELAY_CMD_ENUM['EXTENDED2'], recognized, streamID,
digest, Cell.PAYLOAD_LEN - 11, extended_cell_payload_relay)
# Construct the actual cell
extended_cell = Cell(circ_id, Cell.CMD_ENUM['RELAY'], Cell.PAYLOAD_LEN, extended_cell_payload)
return extended_cell
def process_create_cell(cell: Cell, private_onion_key, y_bytes: bytes) -> (bytes, Dict): """ Process the create cell and return the g^x (public key of sender) :param y_bytes: The private DH key generated by the router node in bytes :param cell: The Create Cell Object :param private_onion_key: The private key of the receiver which will be used in hybrid decrypt :return: g^x as bytes object """ create_cell_payload = cell.PAYLOAD gx_bytes = CoreCryptoRSA.hybrid_decrypt(create_cell_payload.HDATA, private_onion_key) gxy = CoreCryptoDH.compute_dh_shared_key(gx_bytes, y_bytes) kdf_dict = CoreCryptoRSA.kdf_tor(gxy) return gx_bytes, kdf_dict
def build_created_cell(y_bytes: bytes, gy_bytes: bytes, circ_id: int, gx_bytes: bytes) -> Cell: """ The method used to build a created/created2 cell object :param y_bytes: The diffie hellman private key bytes of the receiver :param gy_bytes: The diffie hellman public key bytes of the receiver :param circ_id: The circuit ID :param gx_bytes: The diffie hellman public key bytes of the sender :return: The created Cell object """ gxy = CoreCryptoDH.compute_dh_shared_key(gx_bytes, y_bytes) kdf_dict = CoreCryptoRSA.kdf_tor(gxy) server_h_data = TapSHData(gy_bytes, kdf_dict['KH']) created_cell_payload = CreatedCellPayload(CreatedCellPayload.TAP_S_HANDSHAKE_LEN, server_h_data) created_cell = Cell(circ_id, Cell.CMD_ENUM['CREATED2'], Cell.PAYLOAD_LEN, created_cell_payload) return created_cell
def process_created_cell(cell: Cell, required_circ_id: int, x_bytes: bytes):
"""
The method to process a created cell and return the kdf_dict that will be used after DH handshake
:param cell: The Created Cell Object
:param required_circ_id: The circuit ID that is expected
:param x_bytes: The private key of the sender in bytes
:return: The KDF Dict
"""
if cell.CIRCID == required_circ_id:
created_h_data = cell.PAYLOAD.HDATA
gy_bytes = created_h_data.GY
gxy = CoreCryptoDH.compute_dh_shared_key(gy_bytes, x_bytes)
kdf_dict = CoreCryptoRSA.kdf_tor(gxy)
if created_h_data.KH == kdf_dict['KH']:
print("Handshake successful!")
return kdf_dict
else:
return None
else:
return None
def process_extended_cell(cell: Cell, required_circ_id: int, x_bytes: bytes):
"""
The processing functions for created and extended cells return
dictionaries created by kdf_tor() function.
For verifying KH, the kdf_dict has to be accessed. This is added
to the 'extended' cell handling and similar changes have been made
in the parsing and processing of 'created' cells
"""
if cell.CIRCID == required_circ_id:
extended_h_data = cell.PAYLOAD.Data.HDATA
gy_bytes = extended_h_data.GY
gxy = CoreCryptoDH.compute_dh_shared_key(gy_bytes, x_bytes)
kdf_dict = CoreCryptoRSA.kdf_tor(gxy)
if extended_h_data.KH == kdf_dict['KH']:
print("Handshake successful!")
return kdf_dict
else:
return None
else:
return None