lnpeer+wallet: use channel type for channel open

* channel_type is put into storage, serialized as int and
  deserialized as ChannelType
* check for static_remotekey is done via channel type

electrum/json_db.py

@@ -98,7 +98,7 @@ class StoredDict(dict):
             if not self.db or self.db._should_convert_to_stored_dict(key):
                 v = StoredDict(v, self.db, self.path + [key])
         # convert_value is called depth-first
-        if isinstance(v, dict) or isinstance(v, str):
+        if isinstance(v, dict) or isinstance(v, str) or isinstance(v, int):
             if self.db:
                 v = self.db._convert_value(self.path, key, v)
         # set parent of StoredObject

electrum/lnchannel.py

@@ -52,7 +52,8 @@ from .lnutil import (Outpoint, LocalConfig, RemoteConfig, Keypair, OnlyPubkeyKey
                      ScriptHtlc, PaymentFailure, calc_fees_for_commitment_tx, RemoteMisbehaving, make_htlc_output_witness_script,
                      ShortChannelID, map_htlcs_to_ctx_output_idxs, LNPeerAddr,
                      fee_for_htlc_output, offered_htlc_trim_threshold_sat,
-                     received_htlc_trim_threshold_sat, make_commitment_output_to_remote_address)
+                     received_htlc_trim_threshold_sat, make_commitment_output_to_remote_address,
+                     ChannelType)
 from .lnsweep import create_sweeptxs_for_our_ctx, create_sweeptxs_for_their_ctx
 from .lnsweep import create_sweeptx_for_their_revoked_htlc, SweepInfo
 from .lnhtlc import HTLCManager
@@ -709,7 +710,8 @@ class Channel(AbstractChannel):
         return chan_ann
 
     def is_static_remotekey_enabled(self) -> bool:
-        return bool(self.storage.get('static_remotekey_enabled'))
+        channel_type = ChannelType(self.storage.get('channel_type'))
+        return bool(channel_type & ChannelType.OPTION_STATIC_REMOTEKEY)
 
     def get_wallet_addresses_channel_might_want_reserved(self) -> Sequence[str]:
         ret = []
@@ -925,6 +927,7 @@ class Channel(AbstractChannel):
         Action must be initiated by LOCAL.
         Finally, the next remote ctx becomes the latest remote ctx.
         """
+        # TODO: when more channel types are supported, this method should depend on channel type
         next_remote_ctn = self.get_next_ctn(REMOTE)
         self.logger.info(f"sign_next_commitment {next_remote_ctn}")
 
@@ -966,6 +969,7 @@ class Channel(AbstractChannel):
         If all checks pass, the next local ctx becomes the latest local ctx.
         """
         # TODO in many failure cases below, we should "fail" the channel (force-close)
+        # TODO: when more channel types are supported, this method should depend on channel type
         next_local_ctn = self.get_next_ctn(LOCAL)
         self.logger.info(f"receive_new_commitment. ctn={next_local_ctn}, len(htlc_sigs)={len(htlc_sigs)}")
 

electrum/lnpeer.py

@@ -42,7 +42,7 @@ from .lnutil import (Outpoint, LocalConfig, RECEIVED, UpdateAddHtlc, ChannelConf
                      LightningPeerConnectionClosed, HandshakeFailed,
                      RemoteMisbehaving, ShortChannelID,
                      IncompatibleLightningFeatures, derive_payment_secret_from_payment_preimage,
-                     UpfrontShutdownScriptViolation)
+                     UpfrontShutdownScriptViolation, ChannelType)
 from .lnutil import FeeUpdate, channel_id_from_funding_tx
 from .lntransport import LNTransport, LNTransportBase
 from .lnmsg import encode_msg, decode_msg, UnknownOptionalMsgType
@@ -508,6 +508,9 @@ class Peer(Logger):
     def is_static_remotekey(self):
         return self.features.supports(LnFeatures.OPTION_STATIC_REMOTEKEY_OPT)
 
+    def is_channel_type(self):
+        return self.features.supports(LnFeatures.OPTION_CHANNEL_TYPE_OPT)
+
     def is_upfront_shutdown_script(self):
         return self.features.supports(LnFeatures.OPTION_UPFRONT_SHUTDOWN_SCRIPT_OPT)
 
@@ -525,16 +528,15 @@ class Peer(Logger):
         self.logger.info(f"upfront shutdown script received: {upfront_shutdown_script}")
         return upfront_shutdown_script
 
-    def make_local_config(self, funding_sat: int, push_msat: int, initiator: HTLCOwner) -> LocalConfig:
+    def make_local_config(self, funding_sat: int, push_msat: int, initiator: HTLCOwner, channel_type: ChannelType) -> LocalConfig:
         channel_seed = os.urandom(32)
         initial_msat = funding_sat * 1000 - push_msat if initiator == LOCAL else push_msat
 
-        static_remotekey = None
         # sending empty bytes as the upfront_shutdown_script will give us the
         # flexibility to decide an address at closing time
         upfront_shutdown_script = b''
 
-        if self.is_static_remotekey():
+        if channel_type & channel_type.OPTION_STATIC_REMOTEKEY:
             wallet = self.lnworker.wallet
             assert wallet.txin_type == 'p2wpkh'
             addr = wallet.get_new_sweep_address_for_channel()
@@ -610,7 +612,24 @@ class Peer(Logger):
             raise Exception('Not a trampoline node: ' + str(self.their_features))
 
         feerate = self.lnworker.current_feerate_per_kw()
-        local_config = self.make_local_config(funding_sat, push_msat, LOCAL)
+        # we set a channel type for internal bookkeeping
+        open_channel_tlvs = {}
+        if self.their_features.supports(LnFeatures.OPTION_STATIC_REMOTEKEY_OPT):
+            our_channel_type = ChannelType(ChannelType.OPTION_STATIC_REMOTEKEY)
+        else:
+            our_channel_type = ChannelType(0)
+        # if option_channel_type is negotiated: MUST set channel_type
+        if self.is_channel_type():
+            # if it includes channel_type: MUST set it to a defined type representing the type it wants.
+            open_channel_tlvs['channel_type'] = {
+                'type': our_channel_type.to_bytes_minimal()
+            }
+
+        local_config = self.make_local_config(funding_sat, push_msat, LOCAL, our_channel_type)
+        # if it includes open_channel_tlvs: MUST include upfront_shutdown_script.
+        open_channel_tlvs['upfront_shutdown_script'] = {
+            'shutdown_scriptpubkey': local_config.upfront_shutdown_script
+        }
 
         # for the first commitment transaction
         per_commitment_secret_first = get_per_commitment_secret_from_seed(
@@ -639,10 +658,7 @@ class Peer(Logger):
             channel_flags=0x00,  # not willing to announce channel
             channel_reserve_satoshis=local_config.reserve_sat,
             htlc_minimum_msat=local_config.htlc_minimum_msat,
-            open_channel_tlvs={
-                'upfront_shutdown_script':
-                    {'shutdown_scriptpubkey': local_config.upfront_shutdown_script}
-            }
+            open_channel_tlvs=open_channel_tlvs,
         )
 
         # <- accept_channel
@@ -657,6 +673,15 @@ class Peer(Logger):
         upfront_shutdown_script = self.upfront_shutdown_script_from_payload(
             payload, 'accept')
 
+        accept_channel_tlvs = payload.get('accept_channel_tlvs')
+        their_channel_type = accept_channel_tlvs.get('channel_type') if accept_channel_tlvs else None
+        if their_channel_type:
+            their_channel_type = ChannelType.from_bytes(their_channel_type['type'], byteorder='big').discard_unknown_and_check()
+            # if channel_type is set, and channel_type was set in open_channel,
+            # and they are not equal types: MUST reject the channel.
+            if open_channel_tlvs.get('channel_type') is not None and their_channel_type != our_channel_type:
+                raise Exception("Channel type is not the one that we sent.")
+
         remote_config = RemoteConfig(
             payment_basepoint=OnlyPubkeyKeypair(payload['payment_basepoint']),
             multisig_key=OnlyPubkeyKeypair(payload["funding_pubkey"]),
@@ -672,7 +697,7 @@ class Peer(Logger):
             htlc_minimum_msat=payload['htlc_minimum_msat'],
             next_per_commitment_point=remote_per_commitment_point,
             current_per_commitment_point=None,
-            upfront_shutdown_script=upfront_shutdown_script
+            upfront_shutdown_script=upfront_shutdown_script,
         )
         ChannelConfig.cross_validate_params(
             local_config=local_config,
@@ -721,7 +746,7 @@ class Peer(Logger):
             funding_txn_minimum_depth=funding_txn_minimum_depth
         )
         storage = self.create_channel_storage(
-            channel_id, outpoint, local_config, remote_config, constraints)
+            channel_id, outpoint, local_config, remote_config, constraints, our_channel_type)
         chan = Channel(
             storage,
             sweep_address=self.lnworker.sweep_address,
@@ -752,7 +777,7 @@ class Peer(Logger):
         self.lnworker.add_new_channel(chan)
         return chan, funding_tx
 
-    def create_channel_storage(self, channel_id, outpoint, local_config, remote_config, constraints):
+    def create_channel_storage(self, channel_id, outpoint, local_config, remote_config, constraints, channel_type):
         chan_dict = {
             "node_id": self.pubkey.hex(),
             "channel_id": channel_id.hex(),
@@ -769,7 +794,7 @@ class Peer(Logger):
             "fail_htlc_reasons": {},  # htlc_id -> onion_packet
             "unfulfilled_htlcs": {},  # htlc_id -> error_bytes, failure_message
             "revocation_store": {},
-            "static_remotekey_enabled": self.is_static_remotekey(), # stored because it cannot be "downgraded", per BOLT2
+            "channel_type": channel_type,
         }
         return StoredDict(chan_dict, self.lnworker.db if self.lnworker else None, [])
 
@@ -793,7 +818,21 @@ class Peer(Logger):
         push_msat = payload['push_msat']
         feerate = payload['feerate_per_kw']  # note: we are not validating this
         temp_chan_id = payload['temporary_channel_id']
-        local_config = self.make_local_config(funding_sat, push_msat, REMOTE)
+
+        open_channel_tlvs = payload.get('open_channel_tlvs')
+        channel_type = open_channel_tlvs.get('channel_type') if open_channel_tlvs else None
+        # The receiving node MAY fail the channel if:
+        # option_channel_type was negotiated but the message doesn't include a channel_type
+        if self.is_channel_type() and channel_type is None:
+            raise Exception("sender has advertized option_channel_type, but hasn't sent the channel type")
+        # MUST fail the channel if it supports channel_type,
+        # channel_type was set, and the type is not suitable.
+        elif self.is_channel_type() and channel_type is not None:
+            channel_type = ChannelType.from_bytes(channel_type['type'], byteorder='big').discard_unknown_and_check()
+            if not channel_type.complies_with_features(self.features):
+                raise Exception("sender has sent a channel type we don't support")
+
+        local_config = self.make_local_config(funding_sat, push_msat, REMOTE, channel_type)
 
         upfront_shutdown_script = self.upfront_shutdown_script_from_payload(
             payload, 'open')
@@ -836,6 +875,17 @@ class Peer(Logger):
         per_commitment_point_first = secret_to_pubkey(
             int.from_bytes(per_commitment_secret_first, 'big'))
         min_depth = 3
+        accept_channel_tlvs = {
+            'upfront_shutdown_script': {
+                'shutdown_scriptpubkey': local_config.upfront_shutdown_script
+            },
+        }
+        # The sender: if it sets channel_type: MUST set it to the channel_type from open_channel
+        if self.is_channel_type():
+            accept_channel_tlvs['channel_type'] = {
+                'type': channel_type.to_bytes_minimal()
+            }
+
         self.send_message(
             'accept_channel',
             temporary_channel_id=temp_chan_id,
@@ -852,10 +902,7 @@ class Peer(Logger):
             delayed_payment_basepoint=local_config.delayed_basepoint.pubkey,
             htlc_basepoint=local_config.htlc_basepoint.pubkey,
             first_per_commitment_point=per_commitment_point_first,
-            accept_channel_tlvs={
-                'upfront_shutdown_script':
-                    {'shutdown_scriptpubkey': local_config.upfront_shutdown_script}
-            }
+            accept_channel_tlvs=accept_channel_tlvs,
         )
 
         # <- funding created
@@ -872,7 +919,7 @@ class Peer(Logger):
         )
         outpoint = Outpoint(funding_txid, funding_idx)
         chan_dict = self.create_channel_storage(
-            channel_id, outpoint, local_config, remote_config, constraints)
+            channel_id, outpoint, local_config, remote_config, constraints, channel_type)
         chan = Channel(
             chan_dict,
             sweep_address=self.lnworker.sweep_address,

electrum/lnutil.py

@@ -1169,6 +1169,7 @@ LN_FEATURES_IMPLEMENTED = (
         | LnFeatures.BASIC_MPP_OPT | LnFeatures.BASIC_MPP_REQ
         | LnFeatures.OPTION_TRAMPOLINE_ROUTING_OPT | LnFeatures.OPTION_TRAMPOLINE_ROUTING_REQ
         | LnFeatures.OPTION_SHUTDOWN_ANYSEGWIT_OPT | LnFeatures.OPTION_SHUTDOWN_ANYSEGWIT_REQ
+        | LnFeatures.OPTION_CHANNEL_TYPE_OPT | LnFeatures.OPTION_CHANNEL_TYPE_REQ
 )
 
 

electrum/lnworker.py

@@ -167,7 +167,7 @@ BASE_FEATURES = LnFeatures(0)\
     | LnFeatures.OPTION_STATIC_REMOTEKEY_OPT\
     | LnFeatures.VAR_ONION_OPT\
     | LnFeatures.PAYMENT_SECRET_OPT\
-    | LnFeatures.OPTION_UPFRONT_SHUTDOWN_SCRIPT_OPT
+    | LnFeatures.OPTION_UPFRONT_SHUTDOWN_SCRIPT_OPT\
 
 # we do not want to receive unrequested gossip (see lnpeer.maybe_save_remote_update)
 LNWALLET_FEATURES = BASE_FEATURES\
@@ -177,10 +177,11 @@ LNWALLET_FEATURES = BASE_FEATURES\
     | LnFeatures.BASIC_MPP_OPT\
     | LnFeatures.OPTION_TRAMPOLINE_ROUTING_OPT\
     | LnFeatures.OPTION_SHUTDOWN_ANYSEGWIT_OPT\
+    | LnFeatures.OPTION_CHANNEL_TYPE_OPT\
 
 LNGOSSIP_FEATURES = BASE_FEATURES\
     | LnFeatures.GOSSIP_QUERIES_OPT\
-    | LnFeatures.GOSSIP_QUERIES_REQ
+    | LnFeatures.GOSSIP_QUERIES_REQ\
 
 
 class LNWorker(Logger, NetworkRetryManager[LNPeerAddr]):

electrum/tests/test_lnchannel.py

@@ -107,6 +107,7 @@ def create_channel_state(funding_txid, funding_index, funding_sat, is_initiator,
             'fail_htlc_reasons': {},
             'unfulfilled_htlcs': {},
             'revocation_store': {},
+            'channel_type': lnutil.ChannelType.OPTION_STATIC_REMOTEKEY
     }
     return StoredDict(state, None, [])
 

electrum/tests/test_lnpeer.py

@@ -138,6 +138,7 @@ class MockLNWallet(Logger, NetworkRetryManager[LNPeerAddr]):
         self.features |= LnFeatures.VAR_ONION_OPT
         self.features |= LnFeatures.PAYMENT_SECRET_OPT
         self.features |= LnFeatures.OPTION_TRAMPOLINE_ROUTING_OPT
+        self.features |= LnFeatures.OPTION_CHANNEL_TYPE_OPT
         self.pending_payments = defaultdict(asyncio.Future)
         for chan in chans:
             chan.lnworker = self

electrum/wallet_db.py

@@ -1377,6 +1377,8 @@ class WalletDB(JsonDB):
             v = ChannelConstraints(**v)
         elif key == 'funding_outpoint':
             v = Outpoint(**v)
+        elif key == 'channel_type':
+            v = ChannelType(v)
         return v
 
     def _should_convert_to_stored_dict(self, key) -> bool: