Change WalletSource::sign_tx to sign_psbt

Author: benthecarman

lightning/src/events/bump_transaction.rs

@@ -35,6 +35,7 @@ use bitcoin::{OutPoint, PubkeyHash, Sequence, ScriptBuf, Transaction, TxIn, TxOu
 use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
 use bitcoin::blockdata::locktime::absolute::LockTime;
 use bitcoin::consensus::Encodable;
+use bitcoin::psbt::PartiallySignedTransaction;
 use bitcoin::secp256k1;
 use bitcoin::secp256k1::Secp256k1;
 use bitcoin::secp256k1::ecdsa::Signature;
@@ -343,7 +344,10 @@ pub trait CoinSelectionSource {
 	) -> Result<CoinSelection, ()>;
 	/// Signs and provides the full witness for all inputs within the transaction known to the
 	/// trait (i.e., any provided via [`CoinSelectionSource::select_confirmed_utxos`]).
-	fn sign_tx(&self, tx: Transaction) -> Result<Transaction, ()>;
+	///
+	/// If your wallet does not support signing PSBTs you can call `psbt.extract_tx()` to get the
+	/// unsigned transaction and then sign it with your wallet.
+	fn sign_psbt(&self, tx: PartiallySignedTransaction) -> Result<Transaction, ()>;
 }
 
 /// An alternative to [`CoinSelectionSource`] that can be implemented and used along [`Wallet`] to
@@ -357,7 +361,10 @@ pub trait WalletSource {
 	/// Signs and provides the full [`TxIn::script_sig`] and [`TxIn::witness`] for all inputs within
 	/// the transaction known to the wallet (i.e., any provided via
 	/// [`WalletSource::list_confirmed_utxos`]).
-	fn sign_tx(&self, tx: Transaction) -> Result<Transaction, ()>;
+	///
+	/// If your wallet does not support signing PSBTs you can call `psbt.extract_tx()` to get the
+	/// unsigned transaction and then sign it with your wallet.
+	fn sign_psbt(&self, psbt: PartiallySignedTransaction) -> Result<Transaction, ()>;
 }
 
 /// A wrapper over [`WalletSource`] that implements [`CoinSelection`] by preferring UTXOs that would
@@ -504,8 +511,8 @@ where
 			.or_else(|_| do_coin_selection(true, true))
 	}
 
-	fn sign_tx(&self, tx: Transaction) -> Result<Transaction, ()> {
-		self.source.sign_tx(tx)
+	fn sign_psbt(&self, psbt: PartiallySignedTransaction) -> Result<Transaction, ()> {
+		self.source.sign_psbt(psbt)
 	}
 }
 
@@ -549,16 +556,16 @@ where
 	}
 
 	/// Updates a transaction with the result of a successful coin selection attempt.
-	fn process_coin_selection(&self, tx: &mut Transaction, mut coin_selection: CoinSelection) {
-		for utxo in coin_selection.confirmed_utxos.drain(..) {
+	fn process_coin_selection(&self, tx: &mut Transaction, coin_selection: &CoinSelection) {
+		for utxo in coin_selection.confirmed_utxos.iter() {
 			tx.input.push(TxIn {
 				previous_output: utxo.outpoint,
 				script_sig: ScriptBuf::new(),
 				sequence: Sequence::ZERO,
 				witness: Witness::new(),
 			});
 		}
-		if let Some(change_output) = coin_selection.change_output.take() {
+		if let Some(change_output) = coin_selection.change_output.clone() {
 			tx.output.push(change_output);
 		} else if tx.output.is_empty() {
 			// We weren't provided a change output, likely because the input set was a perfect
@@ -613,15 +620,28 @@ where
 		let total_input_amount = must_spend_amount +
 			coin_selection.confirmed_utxos.iter().map(|utxo| utxo.output.value).sum::<u64>();
 
-		self.process_coin_selection(&mut anchor_tx, coin_selection);
+		self.process_coin_selection(&mut anchor_tx, &coin_selection);
 		let anchor_txid = anchor_tx.txid();
 
+		// construct psbt
+		let mut anchor_psbt = PartiallySignedTransaction::from_unsigned_tx(anchor_tx.clone()).unwrap();
+		// add witness_utxo to anchor input
+		anchor_psbt.inputs[0].witness_utxo = Some(anchor_descriptor.previous_utxo());
+		// add witness_utxo to remaining inputs
+		for (idx, utxo) in coin_selection.confirmed_utxos.into_iter().enumerate() {
+			// add 1 to skip the anchor input
+			let index = idx + 1;
+			debug_assert_eq!(anchor_psbt.unsigned_tx.input[index].previous_output, utxo.outpoint);
+			anchor_psbt.inputs[index].witness_utxo = Some(utxo.output);
+		}
+
 		debug_assert_eq!(anchor_tx.output.len(), 1);
 		#[cfg(debug_assertions)]
 		let unsigned_tx_weight = anchor_tx.weight().to_wu() - (anchor_tx.input.len() as u64 * EMPTY_SCRIPT_SIG_WEIGHT);
 
 		log_debug!(self.logger, "Signing anchor transaction {}", anchor_txid);
-		anchor_tx = self.utxo_source.sign_tx(anchor_tx)?;
+		debug_assert!(anchor_psbt.inputs.iter().all(|i| i.witness_utxo.is_some()));
+		anchor_tx = self.utxo_source.sign_psbt(anchor_psbt)?;
 
 		let signer = anchor_descriptor.derive_channel_signer(&self.signer_provider);
 		let anchor_sig = signer.sign_holder_anchor_input(&anchor_tx, 0, &self.secp)?;
@@ -701,13 +721,29 @@ where
 		let total_input_amount = must_spend_amount +
 			coin_selection.confirmed_utxos.iter().map(|utxo| utxo.output.value).sum::<u64>();
 
-		self.process_coin_selection(&mut htlc_tx, coin_selection);
+		self.process_coin_selection(&mut htlc_tx, &coin_selection);
+
+		// construct psbt
+		let mut htlc_psbt = PartiallySignedTransaction::from_unsigned_tx(htlc_tx.clone()).unwrap();
+		// add witness_utxo to htlc inputs
+		for (i, htlc_descriptor) in htlc_descriptors.iter().enumerate() {
+			debug_assert_eq!(htlc_psbt.unsigned_tx.input[i].previous_output, htlc_descriptor.outpoint());
+			htlc_psbt.inputs[i].witness_utxo = Some(htlc_descriptor.previous_utxo(&self.secp));
+		}
+		// add witness_utxo to remaining inputs
+		for (idx, utxo) in coin_selection.confirmed_utxos.into_iter().enumerate() {
+			// offset to skip the htlc inputs
+			let index = idx + htlc_descriptors.len();
+			debug_assert_eq!(htlc_psbt.unsigned_tx.input[index].previous_output, utxo.outpoint);
+			htlc_psbt.inputs[index].witness_utxo = Some(utxo.output);
+		}
 
 		#[cfg(debug_assertions)]
 		let unsigned_tx_weight = htlc_tx.weight().to_wu() - (htlc_tx.input.len() as u64 * EMPTY_SCRIPT_SIG_WEIGHT);
 
 		log_debug!(self.logger, "Signing HTLC transaction {}", htlc_tx.txid());
-		htlc_tx = self.utxo_source.sign_tx(htlc_tx)?;
+		debug_assert!(htlc_psbt.inputs.iter().all(|i| i.witness_utxo.is_some()));
+		htlc_tx = self.utxo_source.sign_psbt(htlc_psbt)?;
 
 		let mut signers = BTreeMap::new();
 		for (idx, htlc_descriptor) in htlc_descriptors.iter().enumerate() {

lightning/src/util/test_utils.rs

@@ -71,6 +71,7 @@ use crate::sign::{InMemorySigner, Recipient, EntropySource, NodeSigner, SignerPr
 
 #[cfg(feature = "std")]
 use std::time::{SystemTime, UNIX_EPOCH};
+use bitcoin::psbt::PartiallySignedTransaction;
 use bitcoin::Sequence;
 
 pub fn pubkey(byte: u8) -> PublicKey {
@@ -1410,7 +1411,8 @@ impl WalletSource for TestWalletSource {
 		Ok(ScriptBuf::new_p2pkh(&public_key.pubkey_hash()))
 	}
 
-	fn sign_tx(&self, mut tx: Transaction) -> Result<Transaction, ()> {
+	fn sign_psbt(&self, mut psbt: PartiallySignedTransaction) -> Result<Transaction, ()> {
+		let mut tx = psbt.extract_tx();
 		let utxos = self.utxos.borrow();
 		for i in 0..tx.input.len() {
 			if let Some(utxo) = utxos.iter().find(|utxo| utxo.outpoint == tx.input[i].previous_output) {