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electrum/electrum/submarine_swaps.py
SomberNight af6a1f3d01 swaps: use longer final_cltv_delta for client-normal-swap 
This gives more time for the client to come back online.

see https://github.com/spesmilo/electrum/issues/8940

- re note on submarine_swaps.py#L53:
  lnpeer.Peer.maybe_fulfill_htlc only checks against MIN_FINAL_CLTV_DELTA_ACCEPTED(=144),
  so this increased cltv_delta is not enforced when receiving the htlc on ln.
  It is put in the invoice, so the sender is supposed to honour it ofc.
  It would be nice to enforce it (make the check in maybe_fulfill_htlc dependent on
  what was in the invoice).
2024-03-12 14:20:52 +00:00

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import asyncio
import json
import os
from typing import TYPE_CHECKING, Optional, Dict, Union, Sequence, Tuple
from decimal import Decimal
import math
import time
import attr
import aiohttp
from . import lnutil
from .crypto import sha256, hash_160
from .ecc import ECPrivkey
from .bitcoin import (script_to_p2wsh, opcodes, p2wsh_nested_script, push_script,
is_segwit_address, construct_witness)
from .transaction import PartialTxInput, PartialTxOutput, PartialTransaction, Transaction, TxInput, TxOutpoint
from .transaction import script_GetOp, match_script_against_template, OPPushDataGeneric, OPPushDataPubkey
from .util import log_exceptions, BelowDustLimit, OldTaskGroup
from .lnutil import REDEEM_AFTER_DOUBLE_SPENT_DELAY
from .bitcoin import dust_threshold, DummyAddress
from .logging import Logger
from .lnutil import hex_to_bytes
from .lnaddr import lndecode
from .json_db import StoredObject, stored_in
from . import constants
from .address_synchronizer import TX_HEIGHT_LOCAL
from .i18n import _
from .bitcoin import construct_script
from .crypto import ripemd
from .invoices import Invoice
from .network import TxBroadcastServerReturnedError
from .lnonion import OnionRoutingFailure, OnionFailureCode
if TYPE_CHECKING:
from .network import Network
from .wallet import Abstract_Wallet
from .lnwatcher import LNWalletWatcher
from .lnworker import LNWallet
from .lnchannel import Channel
from .simple_config import SimpleConfig
CLAIM_FEE_SIZE = 136
LOCKUP_FEE_SIZE = 153 # assuming 1 output, 2 outputs
MIN_LOCKTIME_DELTA = 60
LOCKTIME_DELTA_REFUND = 70
MAX_LOCKTIME_DELTA = 100
MIN_FINAL_CLTV_DELTA_FOR_CLIENT = 3 * 144 # note: put in invoice, but is not enforced by receiver in lnpeer.py
assert MIN_LOCKTIME_DELTA <= LOCKTIME_DELTA_REFUND <= MAX_LOCKTIME_DELTA
assert MAX_LOCKTIME_DELTA < lnutil.MIN_FINAL_CLTV_DELTA_ACCEPTED
assert MAX_LOCKTIME_DELTA < lnutil.MIN_FINAL_CLTV_DELTA_FOR_INVOICE
assert MAX_LOCKTIME_DELTA < MIN_FINAL_CLTV_DELTA_FOR_CLIENT
# The script of the reverse swaps has one extra check in it to verify
# that the length of the preimage is 32. This is required because in
# the reverse swaps the preimage is generated by the user and to
# settle the hold invoice, you need a preimage with 32 bytes . If that
# check wasn't there the user could generate a preimage with a
# different length which would still allow for claiming the onchain
# coins but the invoice couldn't be settled
WITNESS_TEMPLATE_REVERSE_SWAP = [
opcodes.OP_SIZE,
OPPushDataGeneric(None),
opcodes.OP_EQUAL,
opcodes.OP_IF,
opcodes.OP_HASH160,
OPPushDataGeneric(lambda x: x == 20),
opcodes.OP_EQUALVERIFY,
OPPushDataPubkey,
opcodes.OP_ELSE,
opcodes.OP_DROP,
OPPushDataGeneric(None),
opcodes.OP_CHECKLOCKTIMEVERIFY,
opcodes.OP_DROP,
OPPushDataPubkey,
opcodes.OP_ENDIF,
opcodes.OP_CHECKSIG
]
def check_reverse_redeem_script(
*,
redeem_script: str,
lockup_address: str,
payment_hash: bytes,
locktime: int,
refund_pubkey: bytes = None,
claim_pubkey: bytes = None,
) -> None:
redeem_script = bytes.fromhex(redeem_script)
parsed_script = [x for x in script_GetOp(redeem_script)]
if not match_script_against_template(redeem_script, WITNESS_TEMPLATE_REVERSE_SWAP):
raise Exception("rswap check failed: scriptcode does not match template")
if script_to_p2wsh(redeem_script.hex()) != lockup_address:
raise Exception("rswap check failed: inconsistent scriptcode and address")
if ripemd(payment_hash) != parsed_script[5][1]:
raise Exception("rswap check failed: our preimage not in script")
if claim_pubkey and claim_pubkey != parsed_script[7][1]:
raise Exception("rswap check failed: our pubkey not in script")
if refund_pubkey and refund_pubkey != parsed_script[13][1]:
raise Exception("rswap check failed: our pubkey not in script")
if locktime != int.from_bytes(parsed_script[10][1], byteorder='little'):
raise Exception("rswap check failed: inconsistent locktime and script")
class SwapServerError(Exception):
def __str__(self):
return _("The swap server errored or is unreachable.")
def now():
return int(time.time())
@stored_in('submarine_swaps')
@attr.s
class SwapData(StoredObject):
is_reverse = attr.ib(type=bool) # for whoever is running code (PoV of client or server)
locktime = attr.ib(type=int)
onchain_amount = attr.ib(type=int) # in sats
lightning_amount = attr.ib(type=int) # in sats
redeem_script = attr.ib(type=bytes, converter=hex_to_bytes)
preimage = attr.ib(type=Optional[bytes], converter=hex_to_bytes)
prepay_hash = attr.ib(type=Optional[bytes], converter=hex_to_bytes)
privkey = attr.ib(type=bytes, converter=hex_to_bytes)
lockup_address = attr.ib(type=str)
receive_address = attr.ib(type=str)
funding_txid = attr.ib(type=Optional[str])
spending_txid = attr.ib(type=Optional[str])
is_redeemed = attr.ib(type=bool)
_funding_prevout = None # type: Optional[TxOutpoint] # for RBF
_payment_hash = None
@property
def payment_hash(self) -> bytes:
return self._payment_hash
def create_claim_tx(
*,
txin: PartialTxInput,
witness_script: bytes,
address: str,
amount_sat: int,
locktime: int,
) -> PartialTransaction:
"""Create tx to either claim successful reverse-swap,
or to get refunded for timed-out forward-swap.
"""
txin.script_sig = b''
txin.witness_script = witness_script
txout = PartialTxOutput.from_address_and_value(address, amount_sat)
tx = PartialTransaction.from_io([txin], [txout], version=2, locktime=locktime)
tx.set_rbf(True)
return tx
class SwapManager(Logger):
network: Optional['Network'] = None
lnwatcher: Optional['LNWalletWatcher'] = None
def __init__(self, *, wallet: 'Abstract_Wallet', lnworker: 'LNWallet'):
Logger.__init__(self)
self.normal_fee = 0
self.lockup_fee = 0
self.claim_fee = 0 # part of the boltz prococol, not used by Electrum
self.percentage = 0
self._min_amount = None
self._max_amount = None
self.wallet = wallet
self.lnworker = lnworker
self.taskgroup = None
self.dummy_address = DummyAddress.SWAP
self.swaps = self.wallet.db.get_dict('submarine_swaps') # type: Dict[str, SwapData]
self._swaps_by_funding_outpoint = {} # type: Dict[TxOutpoint, SwapData]
self._swaps_by_lockup_address = {} # type: Dict[str, SwapData]
for payment_hash_hex, swap in self.swaps.items():
payment_hash = bytes.fromhex(payment_hash_hex)
swap._payment_hash = payment_hash
self._add_or_reindex_swap(swap)
if not swap.is_reverse and not swap.is_redeemed:
self.lnworker.register_hold_invoice(payment_hash, self.hold_invoice_callback)
self.prepayments = {} # type: Dict[bytes, bytes] # fee_rhash -> rhash
for k, swap in self.swaps.items():
if swap.prepay_hash is not None:
self.prepayments[swap.prepay_hash] = bytes.fromhex(k)
# api url
self.api_url = wallet.config.SWAPSERVER_URL
# init default min & max
self.init_min_max_values()
def start_network(self, *, network: 'Network', lnwatcher: 'LNWalletWatcher'):
assert network
assert lnwatcher
assert self.network is None, "already started"
self.network = network
self.lnwatcher = lnwatcher
for k, swap in self.swaps.items():
if swap.is_redeemed:
continue
self.add_lnwatcher_callback(swap)
self.taskgroup = OldTaskGroup()
asyncio.run_coroutine_threadsafe(self.main_loop(), self.network.asyncio_loop)
async def main_loop(self):
self.logger.info("starting taskgroup.")
try:
async with self.taskgroup as group:
await group.spawn(self.pay_pending_invoices())
except Exception as e:
self.logger.exception("taskgroup died.")
finally:
self.logger.info("taskgroup stopped.")
async def stop(self):
await self.taskgroup.cancel_remaining()
async def pay_invoice(self, key):
self.logger.info(f'trying to pay invoice {key}')
self.invoices_to_pay[key] = 1000000000000 # lock
try:
invoice = self.wallet.get_invoice(key)
success, log = await self.lnworker.pay_invoice(invoice.lightning_invoice, attempts=10)
except Exception as e:
self.logger.info(f'exception paying {key}, will not retry')
self.invoices_to_pay.pop(key, None)
return
if not success:
self.logger.info(f'failed to pay {key}, will retry in 10 minutes')
self.invoices_to_pay[key] = now() + 600
else:
self.logger.info(f'paid invoice {key}')
self.invoices_to_pay.pop(key, None)
async def pay_pending_invoices(self):
self.invoices_to_pay = {}
while True:
await asyncio.sleep(5)
for key, not_before in list(self.invoices_to_pay.items()):
if now() < not_before:
continue
await self.taskgroup.spawn(self.pay_invoice(key))
def cancel_normal_swap(self, swap: SwapData):
""" we must not have broadcast the funding tx """
if swap.funding_txid is not None:
self.logger.info(f'cannot cancel swap {swap.payment_hash.hex()}: already funded')
return
self._fail_swap(swap, 'user cancelled')
def _fail_swap(self, swap: SwapData, reason: str):
self.logger.info(f'failing swap {swap.payment_hash.hex()}: {reason}')
if not swap.is_reverse and swap.payment_hash in self.lnworker.hold_invoice_callbacks:
self.lnworker.unregister_hold_invoice(swap.payment_hash)
payment_secret = self.lnworker.get_payment_secret(swap.payment_hash)
payment_key = swap.payment_hash + payment_secret
e = OnionRoutingFailure(code=OnionFailureCode.INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS, data=b'')
self.lnworker.save_forwarding_failure(payment_key.hex(), failure_message=e)
self.lnwatcher.remove_callback(swap.lockup_address)
if swap.funding_txid is None:
self.swaps.pop(swap.payment_hash.hex())
@log_exceptions
async def _claim_swap(self, swap: SwapData) -> None:
assert self.network
assert self.lnwatcher
if not self.lnwatcher.adb.is_up_to_date():
return
current_height = self.network.get_local_height()
remaining_time = swap.locktime - current_height
txos = self.lnwatcher.adb.get_addr_outputs(swap.lockup_address)
for txin in txos.values():
if swap.is_reverse and txin.value_sats() < swap.onchain_amount:
# amount too low, we must not reveal the preimage
continue
break
else:
# swap not funded.
txin = None
# if it is a normal swap, we might have double spent the funding tx
# in that case we need to fail the HTLCs
if remaining_time <= 0:
self._fail_swap(swap, 'expired')
if txin:
# the swap is funded
swap.funding_txid = txin.prevout.txid.hex()
swap._funding_prevout = txin.prevout
self._add_or_reindex_swap(swap) # to update _swaps_by_funding_outpoint
funding_height = self.lnwatcher.adb.get_tx_height(txin.prevout.txid.hex())
spent_height = txin.spent_height
if spent_height is not None:
swap.spending_txid = txin.spent_txid
if spent_height > 0:
if current_height - spent_height > REDEEM_AFTER_DOUBLE_SPENT_DELAY:
self.logger.info(f'stop watching swap {swap.lockup_address}')
self.lnwatcher.remove_callback(swap.lockup_address)
swap.is_redeemed = True
elif spent_height == TX_HEIGHT_LOCAL:
if funding_height.conf > 0 or (swap.is_reverse and self.wallet.config.LIGHTNING_ALLOW_INSTANT_SWAPS):
tx = self.lnwatcher.adb.get_transaction(txin.spent_txid)
try:
await self.network.broadcast_transaction(tx)
except TxBroadcastServerReturnedError:
self.logger.info(f'error broadcasting claim tx {txin.spent_txid}')
elif funding_height.height == TX_HEIGHT_LOCAL:
# the funding tx was double spent.
# this will remove both funding and child (spending tx) from adb
self.lnwatcher.adb.remove_transaction(swap.funding_txid)
swap.funding_txid = None
swap.spending_txid = None
else:
# spending tx is in mempool
pass
if not swap.is_reverse:
if swap.preimage is None and spent_height is not None:
# extract the preimage, add it to lnwatcher
tx = self.lnwatcher.adb.get_transaction(txin.spent_txid)
preimage = tx.inputs()[0].witness_elements()[1]
if sha256(preimage) == swap.payment_hash:
swap.preimage = preimage
self.logger.info(f'found preimage: {preimage.hex()}')
self.lnworker.preimages[swap.payment_hash.hex()] = preimage.hex()
# note: we must check the payment secret before we broadcast the funding tx
else:
# refund tx
if spent_height > 0:
self._fail_swap(swap, 'refund tx confirmed')
return
if remaining_time > 0:
# too early for refund
return
else:
if swap.preimage is None:
swap.preimage = self.lnworker.get_preimage(swap.payment_hash)
if swap.preimage is None:
if funding_height.conf <= 0:
return
key = swap.payment_hash.hex()
if remaining_time <= MIN_LOCKTIME_DELTA:
if key in self.invoices_to_pay:
# fixme: should consider cltv of ln payment
self.logger.info(f'locktime too close {key} {remaining_time}')
self.invoices_to_pay.pop(key, None)
return
if key not in self.invoices_to_pay:
self.invoices_to_pay[key] = 0
return
if self.network.config.TEST_SWAPSERVER_REFUND:
# for testing: do not create claim tx
return
if spent_height is not None:
return
try:
tx = self._create_and_sign_claim_tx(txin=txin, swap=swap, config=self.wallet.config)
except BelowDustLimit:
self.logger.info('utxo value below dust threshold')
return
self.logger.info(f'adding claim tx {tx.txid()}')
self.wallet.adb.add_transaction(tx)
swap.spending_txid = tx.txid()
def get_claim_fee(self):
return self.get_fee(CLAIM_FEE_SIZE)
def get_fee(self, size):
# note: 'size' is in vbytes
return self._get_fee(size=size, config=self.wallet.config)
@classmethod
def _get_fee(cls, *, size, config: 'SimpleConfig'):
return config.estimate_fee(size, allow_fallback_to_static_rates=True)
def get_swap(self, payment_hash: bytes) -> Optional[SwapData]:
# for history
swap = self.swaps.get(payment_hash.hex())
if swap:
return swap
payment_hash = self.prepayments.get(payment_hash)
if payment_hash:
return self.swaps.get(payment_hash.hex())
def add_lnwatcher_callback(self, swap: SwapData) -> None:
callback = lambda: self._claim_swap(swap)
self.lnwatcher.add_callback(swap.lockup_address, callback)
async def hold_invoice_callback(self, payment_hash: bytes) -> None:
# note: this assumes the wallet has been unlocked
key = payment_hash.hex()
if key in self.swaps:
swap = self.swaps[key]
if swap.funding_txid is None:
password = self.wallet.get_unlocked_password()
for batch_rbf in [True, False]:
tx = self.create_funding_tx(swap, None, password=password, batch_rbf=batch_rbf)
try:
await self.broadcast_funding_tx(swap, tx)
except TxBroadcastServerReturnedError:
continue
break
def create_normal_swap(self, *, lightning_amount_sat: int, payment_hash: bytes, their_pubkey: bytes = None):
""" server method """
assert lightning_amount_sat
locktime = self.network.get_local_height() + LOCKTIME_DELTA_REFUND
our_privkey = os.urandom(32)
our_pubkey = ECPrivkey(our_privkey).get_public_key_bytes(compressed=True)
onchain_amount_sat = self._get_recv_amount(lightning_amount_sat, is_reverse=True) # what the client is going to receive
redeem_script = construct_script(
WITNESS_TEMPLATE_REVERSE_SWAP,
{1:32, 5:ripemd(payment_hash), 7:their_pubkey, 10:locktime, 13:our_pubkey}
)
swap, invoice, prepay_invoice = self.add_normal_swap(
redeem_script=redeem_script,
locktime=locktime,
onchain_amount_sat=onchain_amount_sat,
lightning_amount_sat=lightning_amount_sat,
payment_hash=payment_hash,
our_privkey=our_privkey,
prepay=True,
)
self.lnworker.register_hold_invoice(payment_hash, self.hold_invoice_callback)
return swap, invoice, prepay_invoice
def add_normal_swap(
self, *,
redeem_script: str,
locktime: int, # onchain
onchain_amount_sat: int,
lightning_amount_sat: int,
payment_hash: bytes,
our_privkey: bytes,
prepay: bool,
channels: Optional[Sequence['Channel']] = None,
min_final_cltv_expiry_delta: Optional[int] = None,
) -> Tuple[SwapData, str, str]:
"""creates a hold invoice"""
if prepay:
prepay_amount_sat = self.get_claim_fee() * 2
invoice_amount_sat = lightning_amount_sat - prepay_amount_sat
else:
invoice_amount_sat = lightning_amount_sat
_, invoice = self.lnworker.get_bolt11_invoice(
payment_hash=payment_hash,
amount_msat=invoice_amount_sat * 1000,
message='Submarine swap',
expiry=300,
fallback_address=None,
channels=channels,
min_final_cltv_expiry_delta=min_final_cltv_expiry_delta,
)
# add payment info to lnworker
self.lnworker.add_payment_info_for_hold_invoice(payment_hash, invoice_amount_sat)
if prepay:
prepay_hash = self.lnworker.create_payment_info(amount_msat=prepay_amount_sat*1000)
_, prepay_invoice = self.lnworker.get_bolt11_invoice(
payment_hash=prepay_hash,
amount_msat=prepay_amount_sat * 1000,
message='Submarine swap mining fees',
expiry=300,
fallback_address=None,
channels=channels,
min_final_cltv_expiry_delta=min_final_cltv_expiry_delta,
)
self.lnworker.bundle_payments([payment_hash, prepay_hash])
self.prepayments[prepay_hash] = payment_hash
else:
prepay_invoice = None
prepay_hash = None
lockup_address = script_to_p2wsh(redeem_script)
receive_address = self.wallet.get_receiving_address()
swap = SwapData(
redeem_script = bytes.fromhex(redeem_script),
locktime = locktime,
privkey = our_privkey,
preimage = None,
prepay_hash = prepay_hash,
lockup_address = lockup_address,
onchain_amount = onchain_amount_sat,
receive_address = receive_address,
lightning_amount = lightning_amount_sat,
is_reverse = False,
is_redeemed = False,
funding_txid = None,
spending_txid = None,
)
swap._payment_hash = payment_hash
self._add_or_reindex_swap(swap)
self.add_lnwatcher_callback(swap)
return swap, invoice, prepay_invoice
def create_reverse_swap(self, *, lightning_amount_sat: int, their_pubkey: bytes) -> SwapData:
""" server method. """
assert lightning_amount_sat is not None
locktime = self.network.get_local_height() + LOCKTIME_DELTA_REFUND
privkey = os.urandom(32)
our_pubkey = ECPrivkey(privkey).get_public_key_bytes(compressed=True)
onchain_amount_sat = self._get_send_amount(lightning_amount_sat, is_reverse=False)
preimage = os.urandom(32)
payment_hash = sha256(preimage)
redeem_script = construct_script(
WITNESS_TEMPLATE_REVERSE_SWAP,
{1:32, 5:ripemd(payment_hash), 7:our_pubkey, 10:locktime, 13:their_pubkey}
)
swap = self.add_reverse_swap(
redeem_script=redeem_script,
locktime=locktime,
privkey=privkey,
preimage=preimage,
payment_hash=payment_hash,
prepay_hash=None,
onchain_amount_sat=onchain_amount_sat,
lightning_amount_sat=lightning_amount_sat)
return swap
def add_reverse_swap(
self,
*,
redeem_script: str,
locktime: int, # onchain
privkey: bytes,
lightning_amount_sat: int,
onchain_amount_sat: int,
preimage: bytes,
payment_hash: bytes,
prepay_hash: Optional[bytes] = None,
) -> SwapData:
lockup_address = script_to_p2wsh(redeem_script)
receive_address = self.wallet.get_receiving_address()
swap = SwapData(
redeem_script = bytes.fromhex(redeem_script),
locktime = locktime,
privkey = privkey,
preimage = preimage,
prepay_hash = prepay_hash,
lockup_address = lockup_address,
onchain_amount = onchain_amount_sat,
receive_address = receive_address,
lightning_amount = lightning_amount_sat,
is_reverse = True,
is_redeemed = False,
funding_txid = None,
spending_txid = None,
)
if prepay_hash:
self.prepayments[prepay_hash] = payment_hash
swap._payment_hash = payment_hash
self._add_or_reindex_swap(swap)
self.add_lnwatcher_callback(swap)
return swap
def add_invoice(self, invoice: str, pay_now: bool = False) -> None:
invoice = Invoice.from_bech32(invoice)
key = invoice.rhash
payment_hash = bytes.fromhex(key)
assert key in self.swaps
swap = self.swaps[key]
assert swap.lightning_amount == int(invoice.get_amount_sat())
self.wallet.save_invoice(invoice)
if pay_now:
# check that we have the preimage
assert sha256(swap.preimage) == payment_hash
assert swap.spending_txid is None
self.invoices_to_pay[key] = 0
async def normal_swap(
self,
*,
lightning_amount_sat: int,
expected_onchain_amount_sat: int,
password,
tx: PartialTransaction = None,
channels = None,
) -> Optional[str]:
"""send on-chain BTC, receive on Lightning
Old (removed) flow:
- User generates an LN invoice with RHASH, and knows preimage.
- User creates on-chain output locked to RHASH.
- Server pays LN invoice. User reveals preimage.
- Server spends the on-chain output using preimage.
cltv safety requirement: (onchain_locktime > LN_locktime), otherwise server is vulnerable
New flow:
- User requests swap
- Server creates preimage, sends RHASH to user
- User creates hold invoice, sends it to server
- Server sends HTLC, user holds it
- User creates on-chain output locked to RHASH
- Server spends the on-chain output using preimage (revealing the preimage)
- User fulfills HTLC using preimage
cltv safety requirement: (onchain_locktime < LN_locktime), otherwise client is vulnerable
"""
assert self.network
assert self.lnwatcher
swap, invoice = await self.request_normal_swap(
lightning_amount_sat=lightning_amount_sat,
expected_onchain_amount_sat=expected_onchain_amount_sat,
channels=channels,
)
tx = self.create_funding_tx(swap, tx, password=password)
return await self.wait_for_htlcs_and_broadcast(swap=swap, invoice=invoice, tx=tx)
async def request_normal_swap(
self,
*,
lightning_amount_sat: int,
expected_onchain_amount_sat: int,
channels: Optional[Sequence['Channel']] = None,
) -> Tuple[SwapData, str]:
refund_privkey = os.urandom(32)
refund_pubkey = ECPrivkey(refund_privkey).get_public_key_bytes(compressed=True)
self.logger.info('requesting preimage hash for swap')
request_data = {
"invoiceAmount": lightning_amount_sat,
"refundPublicKey": refund_pubkey.hex()
}
response = await self.network.async_send_http_on_proxy(
'post',
self.api_url + '/createnormalswap',
json=request_data,
timeout=30)
data = json.loads(response)
payment_hash = bytes.fromhex(data["preimageHash"])
zeroconf = data["acceptZeroConf"]
onchain_amount = data["expectedAmount"]
locktime = data["timeoutBlockHeight"]
lockup_address = data["address"]
redeem_script = data["redeemScript"]
# verify redeem_script is built with our pubkey and preimage
check_reverse_redeem_script(
redeem_script=redeem_script,
lockup_address=lockup_address,
payment_hash=payment_hash,
locktime=locktime,
refund_pubkey=refund_pubkey,
)
# check that onchain_amount is not more than what we estimated
if onchain_amount > expected_onchain_amount_sat:
raise Exception(f"fswap check failed: onchain_amount is more than what we estimated: "
f"{onchain_amount} > {expected_onchain_amount_sat}")
# verify that they are not locking up funds for too long
if locktime - self.network.get_local_height() > MAX_LOCKTIME_DELTA:
raise Exception("fswap check failed: locktime too far in future")
swap, invoice, _ = self.add_normal_swap(
redeem_script=redeem_script,
locktime=locktime,
lightning_amount_sat=lightning_amount_sat,
onchain_amount_sat=onchain_amount,
payment_hash=payment_hash,
our_privkey=refund_privkey,
prepay=False,
channels=channels,
# When the client is doing a normal swap, we create a ln-invoice with larger than usual final_cltv_delta.
# If the user goes offline after broadcasting the funding tx (but before it is mined and
# the server claims it), they need to come back online before the held ln-htlc expires (see #8940).
# If the held ln-htlc expires, and the funding tx got confirmed, the server will have claimed the onchain
# funds, and the ln-htlc will be timed out onchain (and channel force-closed). i.e. the user loses the swap
# amount. Increasing the final_cltv_delta the user puts in the invoice extends this critical window.
min_final_cltv_expiry_delta=MIN_FINAL_CLTV_DELTA_FOR_CLIENT,
)
return swap, invoice
async def wait_for_htlcs_and_broadcast(
self,
*,
swap: SwapData,
invoice: str,
tx: Transaction,
) -> Optional[str]:
payment_hash = swap.payment_hash
refund_pubkey = ECPrivkey(swap.privkey).get_public_key_bytes(compressed=True)
async def callback(payment_hash):
await self.broadcast_funding_tx(swap, tx)
self.lnworker.register_hold_invoice(payment_hash, callback)
# send invoice to server and wait for htlcs
request_data = {
"preimageHash": payment_hash.hex(),
"invoice": invoice,
"refundPublicKey": refund_pubkey.hex(),
}
response = await self.network.async_send_http_on_proxy(
'post',
self.api_url + '/addswapinvoice',
json=request_data,
timeout=30)
data = json.loads(response)
# wait for funding tx
lnaddr = lndecode(invoice)
while swap.funding_txid is None and not lnaddr.is_expired():
await asyncio.sleep(0.1)
return swap.funding_txid
def create_funding_tx(
self,
swap: SwapData,
tx: Optional[PartialTransaction],
*,
password,
batch_rbf: Optional[bool] = None,
) -> PartialTransaction:
# create funding tx
# note: rbf must not decrease payment
# this is taken care of in wallet._is_rbf_allowed_to_touch_tx_output
if tx is None:
funding_output = PartialTxOutput.from_address_and_value(swap.lockup_address, swap.onchain_amount)
tx = self.wallet.create_transaction(
outputs=[funding_output],
rbf=True,
password=password,
batch_rbf=batch_rbf,
)
else:
tx.replace_output_address(DummyAddress.SWAP, swap.lockup_address)
tx.set_rbf(True)
self.wallet.sign_transaction(tx, password)
return tx
@log_exceptions
async def request_swap_for_tx(self, tx: 'PartialTransaction') -> Optional[Tuple[SwapData, str, PartialTransaction]]:
for o in tx.outputs():
if o.address == self.dummy_address:
change_amount = o.value
break
else:
return
await self.get_pairs()
lightning_amount_sat = self.get_recv_amount(change_amount, is_reverse=False)
swap, invoice = await self.request_normal_swap(
lightning_amount_sat = lightning_amount_sat,
expected_onchain_amount_sat=change_amount)
tx.replace_output_address(DummyAddress.SWAP, swap.lockup_address)
return swap, invoice, tx
@log_exceptions
async def broadcast_funding_tx(self, swap: SwapData, tx: Transaction) -> None:
swap.funding_txid = tx.txid()
await self.network.broadcast_transaction(tx)
async def reverse_swap(
self,
*,
lightning_amount_sat: int,
expected_onchain_amount_sat: int,
channels: Optional[Sequence['Channel']] = None,
) -> Optional[str]:
"""send on Lightning, receive on-chain
- User generates preimage, RHASH. Sends RHASH to server.
- Server creates an LN invoice for RHASH.
- User pays LN invoice - except server needs to hold the HTLC as preimage is unknown.
- Server creates on-chain output locked to RHASH.
- User spends on-chain output, revealing preimage.
- Server fulfills HTLC using preimage.
Note: expected_onchain_amount_sat is BEFORE deducting the on-chain claim tx fee.
"""
assert self.network
assert self.lnwatcher
privkey = os.urandom(32)
our_pubkey = ECPrivkey(privkey).get_public_key_bytes(compressed=True)
preimage = os.urandom(32)
payment_hash = sha256(preimage)
request_data = {
"type": "reversesubmarine",
"pairId": "BTC/BTC",
"orderSide": "buy",
"invoiceAmount": lightning_amount_sat,
"preimageHash": payment_hash.hex(),
"claimPublicKey": our_pubkey.hex()
}
response = await self.network.async_send_http_on_proxy(
'post',
self.api_url + '/createswap',
json=request_data,
timeout=30)
data = json.loads(response)
invoice = data['invoice']
fee_invoice = data.get('minerFeeInvoice')
lockup_address = data['lockupAddress']
redeem_script = data['redeemScript']
locktime = data['timeoutBlockHeight']
onchain_amount = data["onchainAmount"]
response_id = data['id']
# verify redeem_script is built with our pubkey and preimage
check_reverse_redeem_script(
redeem_script=redeem_script,
lockup_address=lockup_address,
payment_hash=payment_hash,
locktime=locktime,
refund_pubkey=None,
claim_pubkey=our_pubkey,
)
# check that the onchain amount is what we expected
if onchain_amount < expected_onchain_amount_sat:
raise Exception(f"rswap check failed: onchain_amount is less than what we expected: "
f"{onchain_amount} < {expected_onchain_amount_sat}")
# verify that we will have enough time to get our tx confirmed
if locktime - self.network.get_local_height() <= MIN_LOCKTIME_DELTA:
raise Exception("rswap check failed: locktime too close")
# verify invoice payment_hash
lnaddr = self.lnworker._check_invoice(invoice)
invoice_amount = int(lnaddr.get_amount_sat())
if lnaddr.paymenthash != payment_hash:
raise Exception("rswap check failed: inconsistent RHASH and invoice")
# check that the lightning amount is what we requested
if fee_invoice:
fee_lnaddr = self.lnworker._check_invoice(fee_invoice)
invoice_amount += fee_lnaddr.get_amount_sat()
prepay_hash = fee_lnaddr.paymenthash
else:
prepay_hash = None
if int(invoice_amount) != lightning_amount_sat:
raise Exception(f"rswap check failed: invoice_amount ({invoice_amount}) "
f"not what we requested ({lightning_amount_sat})")
# save swap data to wallet file
swap = self.add_reverse_swap(
redeem_script=redeem_script,
locktime=locktime,
privkey=privkey,
preimage=preimage,
payment_hash=payment_hash,
prepay_hash=prepay_hash,
onchain_amount_sat=onchain_amount,
lightning_amount_sat=lightning_amount_sat)
# initiate fee payment.
if fee_invoice:
asyncio.ensure_future(self.lnworker.pay_invoice(fee_invoice))
# we return if we detect funding
async def wait_for_funding(swap):
while swap.funding_txid is None:
await asyncio.sleep(1)
# initiate main payment
tasks = [asyncio.create_task(self.lnworker.pay_invoice(invoice, channels=channels)), asyncio.create_task(wait_for_funding(swap))]
await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
return swap.funding_txid
def _add_or_reindex_swap(self, swap: SwapData) -> None:
if swap.payment_hash.hex() not in self.swaps:
self.swaps[swap.payment_hash.hex()] = swap
if swap._funding_prevout:
self._swaps_by_funding_outpoint[swap._funding_prevout] = swap
self._swaps_by_lockup_address[swap.lockup_address] = swap
def init_pairs(self) -> None:
""" for server """
self.percentage = 0.5
self._min_amount = 20000
self._max_amount = 10000000
self.normal_fee = self.get_fee(CLAIM_FEE_SIZE)
self.lockup_fee = self.get_fee(LOCKUP_FEE_SIZE)
self.claim_fee = self.get_fee(CLAIM_FEE_SIZE)
async def get_pairs(self) -> None:
"""Might raise SwapServerError."""
from .network import Network
try:
response = await Network.async_send_http_on_proxy(
'get',
self.api_url + '/getpairs',
timeout=30)
except aiohttp.ClientError as e:
self.logger.error(f"Swap server errored: {e!r}")
raise SwapServerError() from e
# we assume server response is well-formed; otherwise let an exception propagate to the crash reporter
pairs = json.loads(response)
# cache data to disk
with open(self.pairs_filename(), 'w', encoding='utf-8') as f:
f.write(json.dumps(pairs))
fees = pairs['pairs']['BTC/BTC']['fees']
self.percentage = fees['percentage']
self.normal_fee = fees['minerFees']['baseAsset']['normal']
self.lockup_fee = fees['minerFees']['baseAsset']['reverse']['lockup']
self.claim_fee = fees['minerFees']['baseAsset']['reverse']['claim']
limits = pairs['pairs']['BTC/BTC']['limits']
self._min_amount = limits['minimal']
self._max_amount = limits['maximal']
assert pairs.get('htlcFirst') is True
def pairs_filename(self):
return os.path.join(self.wallet.config.path, 'swap_pairs')
def init_min_max_values(self):
# use default values if we never requested pairs
try:
with open(self.pairs_filename(), 'r', encoding='utf-8') as f:
pairs = json.loads(f.read())
limits = pairs['pairs']['BTC/BTC']['limits']
self._min_amount = limits['minimal']
self._max_amount = limits['maximal']
except Exception:
self._min_amount = 10000
self._max_amount = 10000000
def get_max_amount(self):
return self._max_amount
def get_min_amount(self):
return self._min_amount
def check_invoice_amount(self, x):
return x >= self.get_min_amount() and x <= self.get_max_amount()
def _get_recv_amount(self, send_amount: Optional[int], *, is_reverse: bool) -> Optional[int]:
"""For a given swap direction and amount we send, returns how much we will receive.
Note: in the reverse direction, the mining fee for the on-chain claim tx is NOT accounted for.
In the reverse direction, the result matches what the swap server returns as response["onchainAmount"].
"""
if send_amount is None:
return
x = Decimal(send_amount)
percentage = Decimal(self.percentage)
if is_reverse:
if not self.check_invoice_amount(x):
return
# see/ref:
# https://github.com/BoltzExchange/boltz-backend/blob/e7e2d30f42a5bea3665b164feb85f84c64d86658/lib/service/Service.ts#L948
percentage_fee = math.ceil(percentage * x / 100)
base_fee = self.lockup_fee
x -= percentage_fee + base_fee
x = math.floor(x)
if x < dust_threshold():
return
else:
x -= self.normal_fee
percentage_fee = math.ceil(x * percentage / (100 + percentage))
x -= percentage_fee
if not self.check_invoice_amount(x):
return
x = int(x)
return x
def _get_send_amount(self, recv_amount: Optional[int], *, is_reverse: bool) -> Optional[int]:
"""For a given swap direction and amount we want to receive, returns how much we will need to send.
Note: in the reverse direction, the mining fee for the on-chain claim tx is NOT accounted for.
In the forward direction, the result matches what the swap server returns as response["expectedAmount"].
"""
if not recv_amount:
return
x = Decimal(recv_amount)
percentage = Decimal(self.percentage)
if is_reverse:
# see/ref:
# https://github.com/BoltzExchange/boltz-backend/blob/e7e2d30f42a5bea3665b164feb85f84c64d86658/lib/service/Service.ts#L928
# https://github.com/BoltzExchange/boltz-backend/blob/e7e2d30f42a5bea3665b164feb85f84c64d86658/lib/service/Service.ts#L958
base_fee = self.lockup_fee
x += base_fee
x = math.ceil(x / ((100 - percentage) / 100))
if not self.check_invoice_amount(x):
return
else:
if not self.check_invoice_amount(x):
return
# see/ref:
# https://github.com/BoltzExchange/boltz-backend/blob/e7e2d30f42a5bea3665b164feb85f84c64d86658/lib/service/Service.ts#L708
# https://github.com/BoltzExchange/boltz-backend/blob/e7e2d30f42a5bea3665b164feb85f84c64d86658/lib/rates/FeeProvider.ts#L90
percentage_fee = math.ceil(percentage * x / 100)
x += percentage_fee + self.normal_fee
x = int(x)
return x
def get_recv_amount(self, send_amount: Optional[int], *, is_reverse: bool) -> Optional[int]:
# first, add percentage fee
recv_amount = self._get_recv_amount(send_amount, is_reverse=is_reverse)
# sanity check calculation can be inverted
if recv_amount is not None:
inverted_send_amount = self._get_send_amount(recv_amount, is_reverse=is_reverse)
# accept off-by ones as amt_rcv = recv_amt(send_amt(amt_rcv)) only up to +-1
if abs(send_amount - inverted_send_amount) > 1:
raise Exception(f"calc-invert-sanity-check failed. is_reverse={is_reverse}. "
f"send_amount={send_amount} -> recv_amount={recv_amount} -> inverted_send_amount={inverted_send_amount}")
# second, add on-chain claim tx fee
if is_reverse and recv_amount is not None:
recv_amount -= self.get_claim_fee()
return recv_amount
def get_send_amount(self, recv_amount: Optional[int], *, is_reverse: bool) -> Optional[int]:
# first, add on-chain claim tx fee
if is_reverse and recv_amount is not None:
recv_amount += self.get_claim_fee()
# second, add percentage fee
send_amount = self._get_send_amount(recv_amount, is_reverse=is_reverse)
# sanity check calculation can be inverted
if send_amount is not None:
inverted_recv_amount = self._get_recv_amount(send_amount, is_reverse=is_reverse)
if recv_amount != inverted_recv_amount:
raise Exception(f"calc-invert-sanity-check failed. is_reverse={is_reverse}. "
f"recv_amount={recv_amount} -> send_amount={send_amount} -> inverted_recv_amount={inverted_recv_amount}")
return send_amount
def get_swap_by_funding_tx(self, tx: Transaction) -> Optional[SwapData]:
if len(tx.outputs()) != 1:
return False
prevout = TxOutpoint(txid=bytes.fromhex(tx.txid()), out_idx=0)
return self._swaps_by_funding_outpoint.get(prevout)
def get_swap_by_claim_tx(self, tx: Transaction) -> Optional[SwapData]:
txin = tx.inputs()[0]
return self.get_swap_by_claim_txin(txin)
def get_swap_by_claim_txin(self, txin: TxInput) -> Optional[SwapData]:
return self._swaps_by_funding_outpoint.get(txin.prevout)
def is_lockup_address_for_a_swap(self, addr: str) -> bool:
return bool(self._swaps_by_lockup_address.get(addr))
def add_txin_info(self, txin: PartialTxInput) -> None:
"""Add some info to a claim txin.
note: even without signing, this is useful for tx size estimation.
"""
swap = self.get_swap_by_claim_txin(txin)
if not swap:
return
preimage = swap.preimage if swap.is_reverse else 0
witness_script = swap.redeem_script
txin.script_sig = b''
txin.witness_script = witness_script
sig_dummy = b'\x00' * 71 # DER-encoded ECDSA sig, with low S and low R
witness = [sig_dummy, preimage, witness_script]
txin.witness_sizehint = len(bytes.fromhex(construct_witness(witness)))
@classmethod
def sign_tx(cls, tx: PartialTransaction, swap: SwapData) -> None:
preimage = swap.preimage if swap.is_reverse else 0
witness_script = swap.redeem_script
txin = tx.inputs()[0]
assert len(tx.inputs()) == 1, f"expected 1 input for swap claim tx. found {len(tx.inputs())}"
assert txin.prevout.txid.hex() == swap.funding_txid
txin.script_sig = b''
txin.witness_script = witness_script
sig = bytes.fromhex(tx.sign_txin(0, swap.privkey))
witness = [sig, preimage, witness_script]
txin.witness = bytes.fromhex(construct_witness(witness))
@classmethod
def _create_and_sign_claim_tx(
cls,
*,
txin: PartialTxInput,
swap: SwapData,
config: 'SimpleConfig',
) -> PartialTransaction:
# FIXME the mining fee should depend on swap.is_reverse.
# the txs are not the same size...
amount_sat = txin.value_sats() - cls._get_fee(size=CLAIM_FEE_SIZE, config=config)
if amount_sat < dust_threshold():
raise BelowDustLimit()
if swap.is_reverse: # successful reverse swap
locktime = 0
# preimage will be set in sign_tx
else: # timing out forward swap
locktime = swap.locktime
tx = create_claim_tx(
txin=txin,
witness_script=swap.redeem_script,
address=swap.receive_address,
amount_sat=amount_sat,
locktime=locktime,
)
cls.sign_tx(tx, swap)
return tx
def max_amount_forward_swap(self) -> Optional[int]:
""" returns None if we cannot swap """
max_swap_amt_ln = self.get_max_amount()
max_recv_amt_ln = int(self.lnworker.num_sats_can_receive())
max_amt_ln = int(min(max_swap_amt_ln, max_recv_amt_ln))
max_amt_oc = self.get_send_amount(max_amt_ln, is_reverse=False) or 0
min_amt_oc = self.get_send_amount(self.get_min_amount(), is_reverse=False) or 0
return max_amt_oc if max_amt_oc >= min_amt_oc else None
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