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electrum/electrum/plugins/watchtower/watchtower.py

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Python

#!/usr/bin/env python
#
# Electrum - Lightweight Bitcoin Client
# Copyright (C) 2023 The Electrum Developers
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import asyncio
import os
from typing import TYPE_CHECKING
from typing import Dict
from electrum.util import log_exceptions, random_shuffled_copy
from electrum.plugin import BasePlugin
from electrum.sql_db import SqlDB, sql
from electrum.transaction import Transaction, match_script_against_template
from electrum.network import Network
from electrum.address_synchronizer import AddressSynchronizer, TX_HEIGHT_LOCAL
from electrum.wallet_db import WalletDB
from electrum.lnutil import WITNESS_TEMPLATE_RECEIVED_HTLC, WITNESS_TEMPLATE_OFFERED_HTLC
from electrum.logging import Logger
from electrum.util import EventListener, event_listener
from .server import WatchTowerServer
if TYPE_CHECKING:
from electrum.simple_config import SimpleConfig
class WatchtowerPlugin(BasePlugin):
def __init__(self, parent, config: 'SimpleConfig', name):
BasePlugin.__init__(self, parent, config, name)
self.config = config
self.network = Network.get_instance()
if self.network is None:
return
self.watchtower = WatchTower(self.network)
asyncio.ensure_future(self.watchtower.start_watching())
if watchtower_port := self.config.WATCHTOWER_SERVER_PORT:
self.server = WatchTowerServer(self.watchtower, self.network, watchtower_port)
asyncio.run_coroutine_threadsafe(self.network.taskgroup.spawn(self.server.run), self.network.asyncio_loop)
class WatchTower(Logger, EventListener):
def __init__(self, network: 'Network'):
Logger.__init__(self)
self.config = network.config
wallet_db = WalletDB('', storage=None, upgrade=True)
self.adb = AddressSynchronizer(wallet_db, self.config, name=self.diagnostic_name())
self.adb.start_network(network)
self.callbacks = {} # address -> lambda function
self.register_callbacks()
# status gets populated when we run
self.channel_status = {}
self.network = network
self.sweepstore = SweepStore(os.path.join(self.config.path, "watchtower_db"), network)
def remove_callback(self, address):
self.callbacks.pop(address, None)
def add_callback(self, address, callback):
self.adb.add_address(address)
self.callbacks[address] = callback
@event_listener
async def on_event_blockchain_updated(self, *args):
await self.trigger_callbacks()
@event_listener
async def on_event_wallet_updated(self, wallet):
# called if we add local tx
if wallet.adb != self.adb:
return
await self.trigger_callbacks()
@event_listener
async def on_event_adb_added_verified_tx(self, adb, tx_hash):
if adb != self.adb:
return
await self.trigger_callbacks()
@event_listener
async def on_event_adb_set_up_to_date(self, adb):
if adb != self.adb:
return
await self.trigger_callbacks()
@log_exceptions
async def trigger_callbacks(self):
if not self.adb.synchronizer:
self.logger.info("synchronizer not set yet")
return
for address, callback in list(self.callbacks.items()):
await callback()
async def stop(self):
self.unregister_callbacks()
await self.adb.stop()
def add_channel(self, outpoint: str, address: str) -> None:
callback = lambda: self.check_onchain_situation(address, outpoint)
self.add_callback(address, callback)
def diagnostic_name(self):
return "watchtower"
@log_exceptions
async def start_watching(self):
# I need to watch the addresses from sweepstore
lst = await self.sweepstore.list_channels()
for outpoint, address in random_shuffled_copy(lst):
self.add_channel(outpoint, address)
async def check_onchain_situation(self, address, funding_outpoint):
# early return if address has not been added yet
if not self.adb.is_mine(address):
return
# inspect_tx_candidate might have added new addresses, in which case we return early
closing_txid = self.adb.get_spender(funding_outpoint)
if closing_txid:
closing_tx = self.adb.get_transaction(closing_txid)
if closing_tx:
keep_watching = await self.sweep_commitment_transaction(funding_outpoint, closing_tx)
else:
self.logger.info(f"channel {funding_outpoint} closed by {closing_txid}. still waiting for tx itself...")
keep_watching = True
else:
keep_watching = True
if not keep_watching:
await self.unwatch_channel(address, funding_outpoint)
def inspect_tx_candidate(self, outpoint, n: int) -> Dict[str, str]:
"""
returns a dict of spenders for a transaction of interest.
subscribes to addresses as a side effect.
n==0 => outpoint is a channel funding.
n==1 => outpoint is a commitment or close output: to_local, to_remote or first-stage htlc
n==2 => outpoint is a second-stage htlc
"""
prev_txid, index = outpoint.split(':')
spender_txid = self.adb.db.get_spent_outpoint(prev_txid, int(index))
result = {outpoint:spender_txid}
if n == 0:
if spender_txid is None:
self.channel_status[outpoint] = 'open'
elif not self.adb.is_deeply_mined(spender_txid):
self.channel_status[outpoint] = 'closed (%d)' % self.adb.get_tx_height(spender_txid).conf
else:
self.channel_status[outpoint] = 'closed (deep)'
if spender_txid is None:
return result
spender_tx = self.adb.get_transaction(spender_txid)
if n == 1:
# if tx input is not a first-stage HTLC, we can stop recursion
# FIXME: this is not true for anchor channels
if len(spender_tx.inputs()) != 1:
return result
o = spender_tx.inputs()[0]
witness = o.witness_elements()
if not witness:
# This can happen if spender_tx is a local unsigned tx in the wallet history, e.g.:
# channel is coop-closed, outpoint is for our coop-close output, and spender_tx is an
# arbitrary wallet-spend.
return result
redeem_script = witness[-1]
if match_script_against_template(redeem_script, WITNESS_TEMPLATE_OFFERED_HTLC):
#self.logger.info(f"input script matches offered htlc {redeem_script.hex()}")
pass
elif match_script_against_template(redeem_script, WITNESS_TEMPLATE_RECEIVED_HTLC):
#self.logger.info(f"input script matches received htlc {redeem_script.hex()}")
pass
else:
return result
for i, o in enumerate(spender_tx.outputs()):
if o.address is None:
continue
if not self.adb.is_mine(o.address):
self.adb.add_address(o.address)
elif n < 2:
r = self.inspect_tx_candidate(spender_txid + ':%d' % i, n + 1)
result.update(r)
return result
async def sweep_commitment_transaction(self, funding_outpoint: str, closing_tx: Transaction) -> bool:
assert closing_tx
spenders = self.inspect_tx_candidate(funding_outpoint, 0)
keep_watching = not self.adb.is_deeply_mined(closing_tx.txid())
for prevout, spender in spenders.items():
if spender is not None:
keep_watching |= not self.adb.is_deeply_mined(spender)
continue
sweep_txns = await self.sweepstore.get_sweep_tx(funding_outpoint, prevout)
for tx in sweep_txns:
await self.broadcast_or_log(funding_outpoint, tx)
keep_watching = True
return keep_watching
async def broadcast_or_log(self, funding_outpoint: str, tx: Transaction):
height = self.adb.get_tx_height(tx.txid()).height
if height != TX_HEIGHT_LOCAL:
return
try:
txid = await self.network.broadcast_transaction(tx)
except Exception as e:
self.logger.info(f'broadcast failure: txid={tx.txid()}, funding_outpoint={funding_outpoint}: {repr(e)}')
else:
self.logger.info(f'broadcast success: txid={tx.txid()}, funding_outpoint={funding_outpoint}')
return txid
async def get_ctn(self, outpoint, addr):
if addr not in self.callbacks.keys():
self.logger.info(f'watching new channel: {outpoint} {addr}')
self.add_channel(outpoint, addr)
return await self.sweepstore.get_ctn(outpoint, addr)
def get_num_tx(self, outpoint):
async def f():
return await self.sweepstore.get_num_tx(outpoint)
return self.network.run_from_another_thread(f())
def list_sweep_tx(self):
async def f():
return await self.sweepstore.list_sweep_tx()
return self.network.run_from_another_thread(f())
def list_channels(self):
async def f():
return await self.sweepstore.list_channels()
return self.network.run_from_another_thread(f())
async def unwatch_channel(self, address, funding_outpoint):
await self.sweepstore.remove_sweep_tx(funding_outpoint)
await self.sweepstore.remove_channel(funding_outpoint)
create_sweep_txs="""
CREATE TABLE IF NOT EXISTS sweep_txs (
funding_outpoint VARCHAR(34) NOT NULL,
ctn INTEGER NOT NULL,
prevout VARCHAR(34),
tx VARCHAR
)"""
create_channel_info="""
CREATE TABLE IF NOT EXISTS channel_info (
outpoint VARCHAR(34) NOT NULL,
address VARCHAR(32),
PRIMARY KEY(outpoint)
)"""
class SweepStore(SqlDB):
def __init__(self, path, network):
super().__init__(network.asyncio_loop, path)
def create_database(self):
c = self.conn.cursor()
c.execute(create_channel_info)
c.execute(create_sweep_txs)
self.conn.commit()
@sql
def get_sweep_tx(self, funding_outpoint, prevout):
c = self.conn.cursor()
c.execute("SELECT tx FROM sweep_txs WHERE funding_outpoint=? AND prevout=?", (funding_outpoint, prevout))
return [Transaction(r[0].hex()) for r in c.fetchall()]
@sql
def list_sweep_tx(self):
c = self.conn.cursor()
c.execute("SELECT funding_outpoint FROM sweep_txs")
return set([r[0] for r in c.fetchall()])
@sql
def add_sweep_tx(self, funding_outpoint, ctn, prevout, raw_tx):
c = self.conn.cursor()
assert Transaction(raw_tx).is_complete()
c.execute("""INSERT INTO sweep_txs (funding_outpoint, ctn, prevout, tx) VALUES (?,?,?,?)""", (funding_outpoint, ctn, prevout, bytes.fromhex(raw_tx)))
self.conn.commit()
@sql
def get_num_tx(self, funding_outpoint):
c = self.conn.cursor()
c.execute("SELECT count(*) FROM sweep_txs WHERE funding_outpoint=?", (funding_outpoint,))
return int(c.fetchone()[0])
@sql
def get_ctn(self, outpoint, addr):
if not self._has_channel(outpoint):
self._add_channel(outpoint, addr)
c = self.conn.cursor()
c.execute("SELECT max(ctn) FROM sweep_txs WHERE funding_outpoint=?", (outpoint,))
return int(c.fetchone()[0] or 0)
@sql
def remove_sweep_tx(self, funding_outpoint):
c = self.conn.cursor()
c.execute("DELETE FROM sweep_txs WHERE funding_outpoint=?", (funding_outpoint,))
self.conn.commit()
def _add_channel(self, outpoint, address):
c = self.conn.cursor()
c.execute("INSERT INTO channel_info (address, outpoint) VALUES (?,?)", (address, outpoint))
self.conn.commit()
@sql
def remove_channel(self, outpoint):
c = self.conn.cursor()
c.execute("DELETE FROM channel_info WHERE outpoint=?", (outpoint,))
self.conn.commit()
def _has_channel(self, outpoint):
c = self.conn.cursor()
c.execute("SELECT * FROM channel_info WHERE outpoint=?", (outpoint,))
r = c.fetchone()
return r is not None
@sql
def get_address(self, outpoint):
c = self.conn.cursor()
c.execute("SELECT address FROM channel_info WHERE outpoint=?", (outpoint,))
r = c.fetchone()
return r[0] if r else None
@sql
def list_channels(self):
c = self.conn.cursor()
c.execute("SELECT outpoint, address FROM channel_info")
return [(r[0], r[1]) for r in c.fetchall()]