Implement Anchor channel event handling

When Anchor outputs need to be spent LDK will generate
`BumpTransactionEvent`s. Here, we add the corresponding event-handling
and PSBT-signing support.

Author: tnull

src/builder.rs

@@ -693,12 +693,11 @@ fn build_with_store_internal(
 	// for inbound channels.
 	let mut user_config = UserConfig::default();
 	user_config.channel_handshake_limits.force_announced_channel_preference = false;
-
-	if !config.trusted_peers_0conf.is_empty() {
-		// Manually accept inbound channels if we expect 0conf channel requests, avoid
-		// generating the events otherwise.
-		user_config.manually_accept_inbound_channels = true;
-	}
+	user_config.manually_accept_inbound_channels = true;
+	// Note the channel_handshake_config will be overwritten in `connect_open_channel`, but we
+	// still set a default here.
+	user_config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx =
+		config.anchor_channels_config.is_some();
 
 	if liquidity_source_config.and_then(|lsc| lsc.lsps2_service.as_ref()).is_some() {
 		// Generally allow claiming underpaying HTLCs as the LSP will skim off some fee. We'll

src/event.rs

@@ -1,7 +1,8 @@
 use crate::types::{DynStore, Sweeper, Wallet};
 
 use crate::{
-	hex_utils, ChannelManager, Config, Error, NetworkGraph, PeerInfo, PeerStore, UserChannelId,
+	hex_utils, BumpTransactionEventHandler, ChannelManager, Config, Error, NetworkGraph, PeerInfo,
+	PeerStore, UserChannelId,
 };
 
 use crate::connection::ConnectionManager;
@@ -15,9 +16,10 @@ use crate::io::{
 	EVENT_QUEUE_PERSISTENCE_KEY, EVENT_QUEUE_PERSISTENCE_PRIMARY_NAMESPACE,
 	EVENT_QUEUE_PERSISTENCE_SECONDARY_NAMESPACE,
 };
-use crate::logger::{log_error, log_info, Logger};
+use crate::logger::{log_debug, log_error, log_info, Logger};
 
 use lightning::chain::chaininterface::ConfirmationTarget;
+use lightning::events::bump_transaction::BumpTransactionEvent;
 use lightning::events::{ClosureReason, PaymentPurpose};
 use lightning::events::{Event as LdkEvent, PaymentFailureReason};
 use lightning::impl_writeable_tlv_based_enum;
@@ -317,6 +319,7 @@ where
 {
 	event_queue: Arc<EventQueue<L>>,
 	wallet: Arc<Wallet>,
+	bump_tx_event_handler: Arc<BumpTransactionEventHandler>,
 	channel_manager: Arc<ChannelManager>,
 	connection_manager: Arc<ConnectionManager<L>>,
 	output_sweeper: Arc<Sweeper>,
@@ -333,15 +336,17 @@ where
 	L::Target: Logger,
 {
 	pub fn new(
-		event_queue: Arc<EventQueue<L>>, wallet: Arc<Wallet>, channel_manager: Arc<ChannelManager>,
-		connection_manager: Arc<ConnectionManager<L>>, output_sweeper: Arc<Sweeper>,
-		network_graph: Arc<NetworkGraph>, payment_store: Arc<PaymentStore<L>>,
-		peer_store: Arc<PeerStore<L>>, runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
-		logger: L, config: Arc<Config>,
+		event_queue: Arc<EventQueue<L>>, wallet: Arc<Wallet>,
+		bump_tx_event_handler: Arc<BumpTransactionEventHandler>,
+		channel_manager: Arc<ChannelManager>, connection_manager: Arc<ConnectionManager<L>>,
+		output_sweeper: Arc<Sweeper>, network_graph: Arc<NetworkGraph>,
+		payment_store: Arc<PaymentStore<L>>, peer_store: Arc<PeerStore<L>>,
+		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>, logger: L, config: Arc<Config>,
 	) -> Self {
 		Self {
 			event_queue,
 			wallet,
+			bump_tx_event_handler,
 			channel_manager,
 			connection_manager,
 			output_sweeper,
@@ -1018,7 +1023,6 @@ where
 			},
 			LdkEvent::DiscardFunding { .. } => {},
 			LdkEvent::HTLCIntercepted { .. } => {},
-			LdkEvent::BumpTransaction(_) => {},
 			LdkEvent::InvoiceRequestFailed { payment_id } => {
 				log_error!(
 					self.logger,
@@ -1062,6 +1066,35 @@ where
 					});
 				}
 			},
+			LdkEvent::BumpTransaction(bte) => {
+				let (channel_id, counterparty_node_id) = match bte {
+					BumpTransactionEvent::ChannelClose {
+						ref channel_id,
+						ref counterparty_node_id,
+						..
+					} => (channel_id, counterparty_node_id),
+					BumpTransactionEvent::HTLCResolution {
+						ref channel_id,
+						ref counterparty_node_id,
+						..
+					} => (channel_id, counterparty_node_id),
+				};
+
+				if let Some(anchor_channels_config) = self.config.anchor_channels_config.as_ref() {
+					if anchor_channels_config
+						.trusted_peers_no_reserve
+						.contains(counterparty_node_id)
+					{
+						log_debug!(self.logger,
+								"Ignoring BumpTransactionEvent for channel {} due to trusted counterparty {}",
+								channel_id, counterparty_node_id
+							);
+						return;
+					}
+				}
+
+				self.bump_tx_event_handler.handle_event(&bte);
+			},
 		}
 	}
 }

src/lib.rs

@@ -133,14 +133,15 @@ use payment::store::PaymentStore;
 use payment::{Bolt11Payment, Bolt12Payment, OnchainPayment, PaymentDetails, SpontaneousPayment};
 use peer_store::{PeerInfo, PeerStore};
 use types::{
-	Broadcaster, ChainMonitor, ChannelManager, DynStore, FeeEstimator, KeysManager, NetworkGraph,
-	PeerManager, Router, Scorer, Sweeper, Wallet,
+	Broadcaster, BumpTransactionEventHandler, ChainMonitor, ChannelManager, DynStore, FeeEstimator,
+	KeysManager, NetworkGraph, PeerManager, Router, Scorer, Sweeper, Wallet,
 };
 pub use types::{ChannelDetails, PeerDetails, UserChannelId};
 
 use logger::{log_error, log_info, log_trace, FilesystemLogger, Logger};
 
 use lightning::chain::{BestBlock, Confirm};
+use lightning::events::bump_transaction::Wallet as LdkWallet;
 use lightning::ln::channelmanager::PaymentId;
 use lightning::ln::msgs::SocketAddress;
 
@@ -620,9 +621,17 @@ impl Node {
 			}
 		});
 
+		let bump_tx_event_handler = Arc::new(BumpTransactionEventHandler::new(
+			Arc::clone(&self.tx_broadcaster),
+			Arc::new(LdkWallet::new(Arc::clone(&self.wallet), Arc::clone(&self.logger))),
+			Arc::clone(&self.keys_manager),
+			Arc::clone(&self.logger),
+		));
+
 		let event_handler = Arc::new(EventHandler::new(
 			Arc::clone(&self.event_queue),
 			Arc::clone(&self.wallet),
+			bump_tx_event_handler,
 			Arc::clone(&self.channel_manager),
 			Arc::clone(&self.connection_manager),
 			Arc::clone(&self.output_sweeper),

src/types.rs

@@ -135,6 +135,14 @@ pub(crate) type Sweeper = OutputSweeper<
 	Arc<KeysManager>,
 >;
 
+pub(crate) type BumpTransactionEventHandler =
+	lightning::events::bump_transaction::BumpTransactionEventHandler<
+		Arc<Broadcaster>,
+		Arc<lightning::events::bump_transaction::Wallet<Arc<Wallet>, Arc<FilesystemLogger>>>,
+		Arc<KeysManager>,
+		Arc<FilesystemLogger>,
+	>;
+
 /// A local, potentially user-provided, identifier of a channel.
 ///
 /// By default, this will be randomly generated for the user to ensure local uniqueness.

src/wallet.rs

@@ -4,6 +4,7 @@ use crate::Error;
 
 use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
 
+use lightning::events::bump_transaction::{Utxo, WalletSource};
 use lightning::ln::msgs::{DecodeError, UnsignedGossipMessage};
 use lightning::ln::script::ShutdownScript;
 use lightning::sign::{
@@ -19,8 +20,14 @@ use bdk::wallet::AddressIndex;
 use bdk::FeeRate;
 use bdk::{SignOptions, SyncOptions};
 
+use bitcoin::address::{Payload, WitnessVersion};
 use bitcoin::bech32::u5;
+use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
 use bitcoin::blockdata::locktime::absolute::LockTime;
+use bitcoin::hash_types::WPubkeyHash;
+use bitcoin::hashes::Hash;
+use bitcoin::key::XOnlyPublicKey;
+use bitcoin::psbt::PartiallySignedTransaction;
 use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1::ecdsa::{RecoverableSignature, Signature};
 use bitcoin::secp256k1::{PublicKey, Scalar, Secp256k1, SecretKey, Signing};
@@ -242,6 +249,123 @@ where
 	}
 }
 
+impl<D, B: Deref, E: Deref, L: Deref> WalletSource for Wallet<D, B, E, L>
+where
+	D: BatchDatabase,
+	B::Target: BroadcasterInterface,
+	E::Target: FeeEstimator,
+	L::Target: Logger,
+{
+	fn list_confirmed_utxos(&self) -> Result<Vec<Utxo>, ()> {
+		let locked_wallet = self.inner.lock().unwrap();
+		let mut utxos = Vec::new();
+		let confirmed_txs: Vec<bdk::TransactionDetails> = locked_wallet
+			.list_transactions(false)
+			.map_err(|e| {
+				log_error!(self.logger, "Failed to retrieve transactions from wallet: {}", e);
+			})?
+			.into_iter()
+			.filter(|t| t.confirmation_time.is_some())
+			.collect();
+		let unspent_confirmed_utxos = locked_wallet
+			.list_unspent()
+			.map_err(|e| {
+				log_error!(
+					self.logger,
+					"Failed to retrieve unspent transactions from wallet: {}",
+					e
+				);
+			})?
+			.into_iter()
+			.filter(|u| confirmed_txs.iter().find(|t| t.txid == u.outpoint.txid).is_some());
+
+		for u in unspent_confirmed_utxos {
+			let payload = Payload::from_script(&u.txout.script_pubkey).map_err(|e| {
+				log_error!(self.logger, "Failed to retrieve script payload: {}", e);
+			})?;
+
+			match payload {
+				Payload::WitnessProgram(program) => match program.version() {
+					WitnessVersion::V0 if program.program().len() == 20 => {
+						let wpkh =
+							WPubkeyHash::from_slice(program.program().as_bytes()).map_err(|e| {
+								log_error!(self.logger, "Failed to retrieve script payload: {}", e);
+							})?;
+						let utxo = Utxo::new_v0_p2wpkh(u.outpoint, u.txout.value, &wpkh);
+						utxos.push(utxo);
+					},
+					WitnessVersion::V1 => {
+						XOnlyPublicKey::from_slice(program.program().as_bytes()).map_err(|e| {
+							log_error!(self.logger, "Failed to retrieve script payload: {}", e);
+						})?;
+
+						let utxo = Utxo {
+							outpoint: u.outpoint,
+							output: TxOut {
+								value: u.txout.value,
+								script_pubkey: ScriptBuf::new_witness_program(&program),
+							},
+							satisfaction_weight: 1 /* empty script_sig */ * WITNESS_SCALE_FACTOR as u64 +
+								1 /* witness items */ + 1 /* schnorr sig len */ + 64, /* schnorr sig */
+						};
+						utxos.push(utxo);
+					},
+					_ => {
+						log_error!(
+							self.logger,
+							"Unexpected witness version or length. Version: {}, Length: {}",
+							program.version(),
+							program.program().len()
+						);
+					},
+				},
+				_ => {
+					log_error!(
+						self.logger,
+						"Tried to use a non-witness script. This must never happen."
+					);
+					panic!("Tried to use a non-witness script. This must never happen.");
+				},
+			}
+		}
+
+		Ok(utxos)
+	}
+
+	fn get_change_script(&self) -> Result<ScriptBuf, ()> {
+		let locked_wallet = self.inner.lock().unwrap();
+		let address_info = locked_wallet.get_address(AddressIndex::LastUnused).map_err(|e| {
+			log_error!(self.logger, "Failed to retrieve new address from wallet: {}", e);
+		})?;
+
+		Ok(address_info.address.script_pubkey())
+	}
+
+	fn sign_psbt(&self, mut psbt: PartiallySignedTransaction) -> Result<Transaction, ()> {
+		let locked_wallet = self.inner.lock().unwrap();
+
+		// While BDK populates both `witness_utxo` and `non_witness_utxo` fields, LDK does not. As
+		// BDK by default doesn't trust the witness UTXO to account for the Segwit bug, we must
+		// disable it here as otherwise we fail to sign.
+		let mut sign_options = SignOptions::default();
+		sign_options.trust_witness_utxo = true;
+
+		match locked_wallet.sign(&mut psbt, sign_options) {
+			Ok(_finalized) => {
+				// BDK will fail to finalize for all LDK-provided inputs of the PSBT. Unfortunately
+				// we can't check more fine grained if it succeeded for all the other inputs here,
+				// so we just ignore the returned `finalized` bool.
+			},
+			Err(err) => {
+				log_error!(self.logger, "Failed to sign transaction: {}", err);
+				return Err(());
+			},
+		}
+
+		Ok(psbt.extract_tx())
+	}
+}
+
 /// Similar to [`KeysManager`], but overrides the destination and shutdown scripts so they are
 /// directly spendable by the BDK wallet.
 pub struct WalletKeysManager<D, B: Deref, E: Deref, L: Deref>
@@ -407,11 +531,10 @@ where
 		})?;
 
 		match address.payload {
-			bitcoin::address::Payload::WitnessProgram(program) => {
-				ShutdownScript::new_witness_program(&program).map_err(|e| {
+			Payload::WitnessProgram(program) => ShutdownScript::new_witness_program(&program)
+				.map_err(|e| {
 					log_error!(self.logger, "Invalid shutdown script: {:?}", e);
-				})
-			},
+				}),
 			_ => {
 				log_error!(
 					self.logger,