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https://github.com/aljazceru/python-teos.git
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refactors project structure
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Sergi Delgado Segura
177
pisa/watcher.py
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177
pisa/watcher.py
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from binascii import hexlify, unhexlify
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from queue import Queue
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from threading import Thread
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from pisa.responder import Responder
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from pisa.zmq_subscriber import ZMQHandler
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from pisa.utils.authproxy import AuthServiceProxy, JSONRPCException
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from hashlib import sha256
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from pisa.conf import BTC_RPC_USER, BTC_RPC_PASSWD, BTC_RPC_HOST, BTC_RPC_PORT, MAX_APPOINTMENTS, EXPIRY_DELTA
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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.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, debug, logging):
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# DISCUSS: about validation of input data
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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), we use lists to avoid that.
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if not self.appointments.get(appointment.locator):
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self.appointments[appointment.locator] = []
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self.appointments[appointment.locator].append(appointment)
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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, args=[self.block_queue, debug, logging])
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watcher = Thread(target=self.do_watch, args=[debug, logging])
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zmq_thread.start()
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watcher.start()
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if debug:
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logging.info("[Watcher] waking up!")
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appointment_added = True
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if debug:
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logging.info('[Watcher] new appointment accepted (locator = {})'.format(appointment.locator))
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else:
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appointment_added = False
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if debug:
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logging.info('[Watcher] maximum appointments reached, appointment rejected (locator = {})'
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.format(appointment.locator))
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return appointment_added
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def do_subscribe(self, block_queue, debug, logging):
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self.zmq_subscriber = ZMQHandler(parent='Watcher')
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self.zmq_subscriber.handle(block_queue, debug, logging)
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def do_watch(self, debug, logging):
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bitcoin_cli = AuthServiceProxy("http://%s:%s@%s:%d" % (BTC_RPC_USER, BTC_RPC_PASSWD, BTC_RPC_HOST,
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BTC_RPC_PORT))
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while len(self.appointments) > 0:
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block_hash = self.block_queue.get()
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try:
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block = bitcoin_cli.getblock(block_hash)
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txids = block.get('tx')
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potential_locators = {sha256(unhexlify(txid)).hexdigest(): txid for txid in txids}
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if debug:
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logging.info("[Watcher] new block received {}".format(block_hash))
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logging.info("[Watcher] list of transactions: {}".format(txids))
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# Delete expired appointments
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to_delete = {}
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for locator in self.appointments:
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for appointment in self.appointments[locator]:
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if block["height"] > appointment.end_time + EXPIRY_DELTA:
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# Get the appointment index and add the appointment to the deletion list
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appointment_pos = self.appointments[locator].index(appointment)
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if locator in to_delete:
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to_delete[locator].append(appointment_pos)
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else:
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to_delete[locator] = [appointment_pos]
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for locator, indexes in to_delete.items():
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if len(indexes) == len(self.appointments[locator]):
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if debug:
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logging.info("[Watcher] end time reached with no match! Deleting appointment {}"
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.format(locator))
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del self.appointments[locator]
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else:
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for i in indexes:
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if debug:
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logging.info("[Watcher] end time reached with no match! Deleting appointment {}:{}"
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.format(locator, i))
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del self.appointments[locator][i]
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# Check is any of the tx_ids in the received block is an actual match
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potential_matches = {}
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for locator in self.appointments.keys():
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if locator in potential_locators:
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# This is locator:txid
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potential_matches[locator] = potential_locators[locator]
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if debug:
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if len(potential_matches) > 0:
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logging.info("[Watcher] list of potential matches: {}".format(potential_matches))
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else:
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logging.info("[Watcher] no potential matches found")
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matches = self.check_potential_matches(potential_matches, bitcoin_cli, debug, logging)
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for locator, appointment_pos, dispute_txid, justice_txid, justice_rawtx in matches:
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if debug:
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logging.info("[Watcher] notifying responder about {} and deleting appointment {}:{}".format(
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justice_txid, locator, appointment_pos))
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self.responder.add_response(dispute_txid, justice_txid, justice_rawtx,
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self.appointments[locator][appointment_pos].end_time, debug, logging)
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# If there was only one appointment that matches the locator we can delete the whole list
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# DISCUSS: We may want to use locks before adding / removing appointment
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if len(self.appointments[locator]) == 1:
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del self.appointments[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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del self.appointments[locator][appointment_pos]
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except JSONRPCException as e:
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if debug:
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logging.error("[Watcher] JSONRPCException. Error code {}".format(e))
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continue
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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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if debug:
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logging.error("[Watcher] no more pending appointments, going back to sleep")
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def check_potential_matches(self, potential_matches, bitcoin_cli, debug, logging):
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matches = []
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for locator, dispute_txid in potential_matches.items():
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for appointment_pos, appointment in enumerate(self.appointments.get(locator)):
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try:
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justice_rawtx = appointment.encrypted_blob.decrypt(unhexlify(dispute_txid), debug, logging)
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justice_rawtx = hexlify(justice_rawtx).decode()
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justice_txid = bitcoin_cli.decoderawtransaction(justice_rawtx).get('txid')
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matches.append((locator, appointment_pos, dispute_txid, justice_txid, justice_rawtx))
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if debug:
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logging.info("[Watcher] match found for {}:{}! {}".format(locator, appointment_pos,
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justice_txid))
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except JSONRPCException as e:
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# Tx decode failed returns error code -22, maybe we should be more strict here. Leaving it simple
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# for the POC
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if debug:
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logging.error("[Watcher] can't build transaction from decoded data. Error code {}".format(e))
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continue
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return matches
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