mirror of
https://github.com/aljazceru/python-teos.git
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151 lines
6.6 KiB
Python
151 lines
6.6 KiB
Python
from uuid import uuid4
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from queue import Queue
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from threading import Thread
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.serialization import load_pem_private_key
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from cryptography.hazmat.primitives.asymmetric import ec
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from pisa.logger import Logger
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from pisa.cleaner import Cleaner
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from pisa.conf import EXPIRY_DELTA, MAX_APPOINTMENTS, PISA_SECRET_KEY
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from pisa.responder import Responder
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from pisa.block_processor import BlockProcessor
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from pisa.utils.zmq_subscriber import ZMQHandler
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logger = Logger("Watcher")
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class Watcher:
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def __init__(self, db_manager, responder=None, max_appointments=MAX_APPOINTMENTS):
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self.appointments = dict()
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self.locator_uuid_map = dict()
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self.block_queue = None
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self.asleep = True
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self.max_appointments = max_appointments
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self.zmq_subscriber = None
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if not isinstance(responder, Responder):
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self.responder = Responder(db_manager)
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self.db_manager = db_manager
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if PISA_SECRET_KEY is None:
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raise ValueError("No signing key provided. Please fix your pisa.conf")
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else:
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with open(PISA_SECRET_KEY, "r") as key_file:
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secret_key_pem = key_file.read().encode("utf-8")
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self.signing_key = load_pem_private_key(secret_key_pem, password=None, backend=default_backend())
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def sign_appointment(self, appointment):
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data = appointment.to_json().encode("utf-8")
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return self.signing_key.sign(data, ec.ECDSA(hashes.SHA256()))
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def add_appointment(self, appointment):
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# Rationale:
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# The Watcher will analyze every received block looking for appointment matches. If there is no work
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# to do the watcher can go sleep (if appointments = {} then asleep = True) otherwise for every received block
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# the watcher will get the list of transactions and compare it with the list of appointments.
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# If the watcher is awake, every new appointment will just be added to the appointment list until
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# max_appointments is reached.
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if len(self.appointments) < self.max_appointments:
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# Appointments are identified by the locator: the sha256 of commitment txid (H(tx_id)).
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# Two different nodes may ask for appointments using the same commitment txid, what will result in a
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# collision in our appointments structure (and may be an attack surface). In order to avoid such collisions
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# we will identify every appointment with a uuid
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uuid = uuid4().hex
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self.appointments[uuid] = appointment
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if appointment.locator in self.locator_uuid_map:
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self.locator_uuid_map[appointment.locator].append(uuid)
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else:
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self.locator_uuid_map[appointment.locator] = [uuid]
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if self.asleep:
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self.asleep = False
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self.block_queue = Queue()
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zmq_thread = Thread(target=self.do_subscribe)
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watcher = Thread(target=self.do_watch)
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zmq_thread.start()
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watcher.start()
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logger.info("Waking up")
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self.db_manager.store_watcher_appointment(uuid, appointment.to_json())
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appointment_added = True
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logger.info("New appointment accepted.", locator=appointment.locator)
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signature = self.sign_appointment(appointment)
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else:
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appointment_added = False
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signature = None
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logger.info("Maximum appointments reached, appointment rejected.", locator=appointment.locator)
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return appointment_added, signature
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def do_subscribe(self):
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self.zmq_subscriber = ZMQHandler(parent="Watcher")
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self.zmq_subscriber.handle(self.block_queue)
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def do_watch(self):
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while len(self.appointments) > 0:
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block_hash = self.block_queue.get()
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logger.info("New block received", block_hash=block_hash)
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block = BlockProcessor.get_block(block_hash)
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if block is not None:
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txids = block.get('tx')
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logger.info("List of transactions.", txids=txids)
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expired_appointments = [uuid for uuid, appointment in self.appointments.items()
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if block["height"] > appointment.end_time + EXPIRY_DELTA]
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Cleaner.delete_expired_appointment(expired_appointments, self.appointments, self.locator_uuid_map,
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self.db_manager)
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potential_matches = BlockProcessor.get_potential_matches(txids, self.locator_uuid_map)
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matches = BlockProcessor.get_matches(potential_matches, self.locator_uuid_map, self.appointments)
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for locator, uuid, dispute_txid, justice_txid, justice_rawtx in matches:
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# Errors decrypting the Blob will result in a None justice_txid
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if justice_txid is not None:
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logger.info("Notifying responder and deleting appointment.", justice_txid=justice_txid,
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locator=locator, uuid=uuid)
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self.responder.add_response(uuid, dispute_txid, justice_txid, justice_rawtx,
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self.appointments[uuid].end_time, block_hash)
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# Delete the appointment
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appointment = self.appointments.pop(uuid)
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# If there was only one appointment that matches the locator we can delete the whole list
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if len(self.locator_uuid_map[locator]) == 1:
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self.locator_uuid_map.pop(locator)
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else:
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# Otherwise we just delete the appointment that matches locator:appointment_pos
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self.locator_uuid_map[locator].remove(uuid)
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# DISCUSS: instead of deleting the appointment, we will mark it as triggered and delete it from both
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# the watcher's and responder's db after fulfilled
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# Update appointment in the db
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appointment["triggered"] = True
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self.db_manager.store_watcher_appointment(uuid, appointment.to_json())
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# Register the last processed block for the watcher
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self.db_manager.store_last_block_watcher(block_hash)
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# Go back to sleep if there are no more appointments
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self.asleep = True
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self.zmq_subscriber.terminate = True
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logger.error("No more pending appointments, going back to sleep")
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