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d7c89ddc91
The decryption for the `EncryptedBlob` using AES-GCM-128 (the only cipher available atm) raises an `InvalidTag` exception. This was not properly captured by the watcher making it crash. This behavior was already discovered during the `EncryptedBlob` unit testing and left to be fixed in the `Watcher` unit testing. However, making the EncryptedBlob raise such an exception may not be a good practice, since other ciphers may run into different exceptions. Therefore, the `EncryptedBlob` has been modified to return None upon facing a decryption issue, the `BlockProcessor` will detect that and return a None justice_txm and justice_txid. Upon receiving a None `justice_txid` the `Watcher` will delete the appointment without notifiying the `Responder`.
120 lines
5.0 KiB
Python
120 lines
5.0 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 pisa.logger import Logger
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from pisa.cleaner import Cleaner
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from pisa.conf import EXPIRY_DELTA
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from pisa.responder import Responder
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from pisa.conf import MAX_APPOINTMENTS
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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, 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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self.responder = Responder()
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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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appointment_added = True
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logger.info("New appointment accepted.", locator=appointment.locator)
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else:
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appointment_added = False
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logger.info("Maximum appointments reached, appointment rejected.", locator=appointment.locator)
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return appointment_added
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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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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)
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# Delete the appointment
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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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# ToDo: #9-add-data-persistence
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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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# ToDo: #9-add-data-persistence
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self.locator_uuid_map[locator].remove(uuid)
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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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