ln: cooperative close with remote peer initiating

electrum/lnbase.py

@@ -291,6 +291,7 @@ class Peer(PrintError):
         self.commitment_signed = defaultdict(asyncio.Queue)
         self.announcement_signatures = defaultdict(asyncio.Queue)
         self.update_fail_htlc = defaultdict(asyncio.Queue)
+        self.closing_signed = defaultdict(asyncio.Queue)
         self.localfeatures = (0x08 if request_initial_sync else 0)
         self.invoices = lnworker.invoices
         self.attempted_route = {}
@@ -393,7 +394,7 @@ class Peer(PrintError):
             self._sn = 0
         return o
 
-    def process_message(self, message):
+    async def process_message(self, message):
         message_type, payload = decode_msg(message)
         #self.print_error("Received '%s'" % message_type.upper())
         try:
@@ -404,6 +405,9 @@ class Peer(PrintError):
         # raw message is needed to check signature
         if message_type=='node_announcement':
             payload['raw'] = message
+        if asyncio.iscoroutinefunction(f):
+            await f(payload)
+        else:
             f(payload)
 
     def on_error(self, payload):
@@ -451,7 +455,7 @@ class Peer(PrintError):
         self.send_message(gen_msg("init", gflen=0, lflen=1, localfeatures=self.localfeatures))
         # read init
         msg = await self.read_message()
-        self.process_message(msg)
+        await self.process_message(msg)
         self.initialized.set_result(True)
 
     @aiosafe
@@ -462,7 +466,7 @@ class Peer(PrintError):
         while True:
             self.ping_if_required()
             msg = await self.read_message()
-            self.process_message(msg)
+            await self.process_message(msg)
 
     def close_and_cleanup(self):
         try:
@@ -1076,3 +1080,31 @@ class Peer(PrintError):
         if feerate_per_kvbyte is None:
             feerate_per_kvbyte = FEERATE_FALLBACK_STATIC_FEE
         return max(253, feerate_per_kvbyte // 4)
+
+    def on_closing_signed(self, payload):
+        chan_id = payload["channel_id"]
+        if chan_id not in self.closing_signed: raise Exception("Got unknown closing_signed")
+        self.closing_signed[chan_id].put_nowait(payload)
+
+    async def on_shutdown(self, payload):
+        # length of scripts allowed in BOLT-02
+        if int.from_bytes(payload['len'], 'big') not in (3+20+2, 2+20+1, 2+20, 2+32):
+            raise Exception('scriptpubkey length in received shutdown message invalid: ' + str(payload['len']))
+
+        chan = self.channels[payload['channel_id']]
+        scriptpubkey = bfh(bitcoin.address_to_script(chan.sweep_address))
+        self.send_message(gen_msg('shutdown', channel_id=chan.channel_id, len=len(scriptpubkey), scriptpubkey=scriptpubkey))
+
+        signature, fee = chan.make_closing_tx(scriptpubkey, payload['scriptpubkey'])
+        self.send_message(gen_msg('closing_signed', channel_id=chan.channel_id, fee_satoshis=fee, signature=signature))
+
+        while chan.get_state() != 'CLOSED':
+            try:
+                closing_signed = await asyncio.wait_for(self.closing_signed[chan.channel_id].get(), 1)
+            except asyncio.TimeoutError:
+                pass
+            else:
+                fee = closing_signed['fee_satoshis']
+                signature, _ = chan.make_closing_tx(scriptpubkey, payload['scriptpubkey'], fee_sat=fee)
+                self.send_message(gen_msg('closing_signed', channel_id=chan.channel_id, fee_satoshis=fee, signature=signature))
+        self.print_error('REMOTE PEER CLOSED CHANNEL')

electrum/lnhtlc.py

@@ -3,9 +3,10 @@ from collections import namedtuple
 import binascii
 import json
 from enum import Enum, auto
+from typing import Optional
 
 from .util import bfh, PrintError, bh2u
-from .bitcoin import Hash
+from .bitcoin import Hash, TYPE_SCRIPT
 from .bitcoin import redeem_script_to_address
 from .crypto import sha256
 from . import ecc
@@ -15,8 +16,7 @@ from .lnutil import secret_to_pubkey, derive_privkey, derive_pubkey, derive_blin
 from .lnutil import sign_and_get_sig_string
 from .lnutil import make_htlc_tx_with_open_channel, make_commitment, make_received_htlc, make_offered_htlc
 from .lnutil import HTLC_TIMEOUT_WEIGHT, HTLC_SUCCESS_WEIGHT
-from .lnutil import funding_output_script, extract_ctn_from_tx_and_chan
-from .lnutil import LOCAL, REMOTE, SENT, RECEIVED, HTLCOwner
+from .lnutil import funding_output_script, LOCAL, REMOTE, HTLCOwner, make_closing_tx, make_outputs
 from .transaction import Transaction
 
 
@@ -730,3 +730,26 @@ class HTLCStateMachine(PrintError):
             for_us,
             chan.constraints.is_initiator,
             htlcs=htlcs)
+
+    def make_closing_tx(self, local_script: bytes, remote_script: bytes, fee_sat: Optional[int] = None) -> (bytes, int):
+        if fee_sat is None:
+            fee_sat = self.pending_local_fee
+
+        _, outputs = make_outputs(fee_sat * 1000, True,
+                self.local_state.amount_msat,
+                self.remote_state.amount_msat,
+                (TYPE_SCRIPT, bh2u(local_script)),
+                (TYPE_SCRIPT, bh2u(remote_script)),
+                [], self.local_config.dust_limit_sat)
+
+        closing_tx = make_closing_tx(self.local_config.multisig_key.pubkey,
+                self.remote_config.multisig_key.pubkey,
+                self.local_config.payment_basepoint.pubkey,
+                self.remote_config.payment_basepoint.pubkey,
+                # TODO hardcoded we_are_initiator:
+                True, *self.funding_outpoint, self.constraints.capacity,
+                outputs)
+
+        der_sig = bfh(closing_tx.sign_txin(0, self.local_config.multisig_key.privkey))
+        sig = ecc.sig_string_from_der_sig(der_sig[:-1])
+        return sig, fee_sat

electrum/lnutil.py

@@ -1,7 +1,7 @@
 from enum import IntFlag
 import json
 from collections import namedtuple
-from typing import NamedTuple
+from typing import NamedTuple, List, Tuple
 
 from .util import bfh, bh2u, inv_dict
 from .crypto import sha256
@@ -270,24 +270,15 @@ def make_htlc_tx_with_open_channel(chan, pcp, for_us, we_receive, amount_msat, c
     htlc_tx = make_htlc_tx(cltv_expiry, inputs=htlc_tx_inputs, output=htlc_tx_output)
     return htlc_tx
 
-
-def make_commitment(ctn, local_funding_pubkey, remote_funding_pubkey,
-                    remote_payment_pubkey, payment_basepoint,
-                    remote_payment_basepoint, revocation_pubkey,
-                    delayed_pubkey, to_self_delay, funding_txid,
-                    funding_pos, funding_sat, local_amount, remote_amount,
-                    dust_limit_sat, local_feerate, for_us, we_are_initiator,
-                    htlcs):
-
+def make_funding_input(local_funding_pubkey: bytes, remote_funding_pubkey: bytes,
+        payment_basepoint: bytes, remote_payment_basepoint: bytes, we_are_initiator: bool,
+        funding_pos: int, funding_txid: bytes, funding_sat: int):
     pubkeys = sorted([bh2u(local_funding_pubkey), bh2u(remote_funding_pubkey)])
     payments = [payment_basepoint, remote_payment_basepoint]
     if not we_are_initiator:
         payments.reverse()
-    obs = get_obscured_ctn(ctn, *payments)
-    locktime = (0x20 << 24) + (obs & 0xffffff)
-    sequence = (0x80 << 24) + (obs >> 24)
     # commitment tx input
-    c_inputs = [{
+    c_input = {
         'type': 'p2wsh',
         'x_pubkeys': pubkeys,
         'signatures': [None, None],
@@ -296,19 +287,15 @@ def make_commitment(ctn, local_funding_pubkey, remote_funding_pubkey,
         'prevout_hash': funding_txid,
         'value': funding_sat,
         'coinbase': False,
-        'sequence': sequence
-    }]
-    # commitment tx outputs
-    local_address = make_commitment_output_to_local_address(revocation_pubkey, to_self_delay, delayed_pubkey)
-    remote_address = make_commitment_output_to_remote_address(remote_payment_pubkey)
-    # TODO trim htlc outputs here while also considering 2nd stage htlc transactions
-    fee = local_feerate * overall_weight(len(htlcs))
-    fee = fee // 1000 * 1000
-    we_pay_fee = for_us == we_are_initiator
-    to_local_amt = local_amount - (fee if we_pay_fee else 0)
-    to_local = TxOutput(bitcoin.TYPE_ADDRESS, local_address, to_local_amt // 1000)
-    to_remote_amt = remote_amount - (fee if not we_pay_fee else 0)
-    to_remote = TxOutput(bitcoin.TYPE_ADDRESS, remote_address, to_remote_amt // 1000)
+    }
+    return c_input, payments
+
+def make_outputs(fee_msat: int, we_pay_fee: bool, local_amount: int, remote_amount: int,
+        local_tupl, remote_tupl, htlcs: List[Tuple[bytes, int]], dust_limit_sat: int) -> Tuple[List[TxOutput], List[TxOutput]]:
+    to_local_amt = local_amount - (fee_msat if we_pay_fee else 0)
+    to_local = TxOutput(*local_tupl, to_local_amt // 1000)
+    to_remote_amt = remote_amount - (fee_msat if not we_pay_fee else 0)
+    to_remote = TxOutput(*remote_tupl, to_remote_amt // 1000)
     c_outputs = [to_local, to_remote]
     for script, msat_amount in htlcs:
         c_outputs += [TxOutput(bitcoin.TYPE_ADDRESS,
@@ -317,6 +304,37 @@ def make_commitment(ctn, local_funding_pubkey, remote_funding_pubkey,
 
     # trim outputs
     c_outputs_filtered = list(filter(lambda x:x[2]>= dust_limit_sat, c_outputs))
+    return c_outputs, c_outputs_filtered
+
+
+def make_commitment(ctn, local_funding_pubkey, remote_funding_pubkey,
+                    remote_payment_pubkey, payment_basepoint,
+                    remote_payment_basepoint, revocation_pubkey,
+                    delayed_pubkey, to_self_delay, funding_txid,
+                    funding_pos, funding_sat, local_amount, remote_amount,
+                    dust_limit_sat, local_feerate, for_us, we_are_initiator,
+                    htlcs):
+    c_input, payments = make_funding_input(local_funding_pubkey, remote_funding_pubkey,
+        payment_basepoint, remote_payment_basepoint, we_are_initiator, funding_pos,
+        funding_txid, funding_sat)
+    obs = get_obscured_ctn(ctn, *payments)
+    locktime = (0x20 << 24) + (obs & 0xffffff)
+    sequence = (0x80 << 24) + (obs >> 24)
+    c_input['sequence'] = sequence
+
+    c_inputs = [c_input]
+
+    # commitment tx outputs
+    local_address = make_commitment_output_to_local_address(revocation_pubkey, to_self_delay, delayed_pubkey)
+    remote_address = make_commitment_output_to_remote_address(remote_payment_pubkey)
+    # TODO trim htlc outputs here while also considering 2nd stage htlc transactions
+    fee = local_feerate * overall_weight(len(htlcs))
+    fee = fee // 1000 * 1000
+    we_pay_fee = for_us == we_are_initiator
+
+    c_outputs, c_outputs_filtered = make_outputs(fee, we_pay_fee, local_amount, remote_amount,
+        (bitcoin.TYPE_ADDRESS, local_address), (bitcoin.TYPE_ADDRESS, remote_address), htlcs, dust_limit_sat)
+
     assert sum(x[2] for x in c_outputs) <= funding_sat
 
     # create commitment tx
@@ -445,3 +463,14 @@ SENT = HTLCOwner.SENT
 RECEIVED = HTLCOwner.RECEIVED
 LOCAL = HTLCOwner.LOCAL
 REMOTE = HTLCOwner.REMOTE
+
+def make_closing_tx(local_funding_pubkey: bytes, remote_funding_pubkey: bytes,
+        payment_basepoint: bytes, remote_payment_basepoint: bytes, we_are_initiator: bool,
+        funding_txid: bytes, funding_pos: int, funding_sat: int, outputs: List[TxOutput]):
+    c_input, payments = make_funding_input(local_funding_pubkey, remote_funding_pubkey,
+        payment_basepoint, remote_payment_basepoint, we_are_initiator, funding_pos,
+        funding_txid, funding_sat)
+    c_input['sequence'] = 0xFFFF_FFFF
+    tx = Transaction.from_io([c_input], outputs, locktime=0, version=2)
+    tx.BIP_LI01_sort()
+    return tx

electrum/lnworker.py

@@ -218,7 +218,8 @@ class LNWorker(PrintError):
 
     def list_channels(self):
         with self.lock:
-            return [str(x) for x in self.channels]
+            # we output the funding_outpoint instead of the channel_id because lnd uses channel_point (funding outpoint) to identify channels
+            return [(chan.funding_outpoint.to_str(), chan.get_state()) for channel_id, chan in self.channels.items()]
 
     def close_channel(self, chan_id):
         chan = self.channels[chan_id]