Merge pull request lightningdevkit#1165 from lightning-signer/2021-11-fix-anchors

Fix countersignatory (to_remote) output redeemscript when anchors enabled

Author: TheBlueMatt

lightning/src/ln/chan_utils.rs

@@ -608,6 +608,17 @@ pub fn build_htlc_transaction(commitment_txid: &Txid, feerate_per_kw: u32, conte
 	}
 }
 
+/// Gets the witnessScript for the to_remote output when anchors are enabled.
+#[inline]
+pub(crate) fn get_to_countersignatory_with_anchors_redeemscript(payment_point: &PublicKey) -> Script {
+	Builder::new()
+		.push_slice(&payment_point.serialize()[..])
+		.push_opcode(opcodes::all::OP_CHECKSIGVERIFY)
+		.push_int(1)
+		.push_opcode(opcodes::all::OP_CSV)
+		.into_script()
+}
+
 /// Gets the witnessScript for an anchor output from the funding public key.
 /// The witness in the spending input must be:
 /// <BIP 143 funding_signature>
@@ -1130,7 +1141,11 @@ impl CommitmentTransaction {
 		let mut txouts: Vec<(TxOut, Option<&mut HTLCOutputInCommitment>)> = Vec::new();
 
 		if to_countersignatory_value_sat > 0 {
-			let script = script_for_p2wpkh(&countersignatory_pubkeys.payment_point);
+			let script = if opt_anchors {
+			    get_to_countersignatory_with_anchors_redeemscript(&countersignatory_pubkeys.payment_point).to_v0_p2wsh()
+			} else {
+			    get_p2wpkh_redeemscript(&countersignatory_pubkeys.payment_point)
+			};
 			txouts.push((
 				TxOut {
 					script_pubkey: script.clone(),
@@ -1424,7 +1439,7 @@ pub fn get_commitment_transaction_number_obscure_factor(
 		| ((res[31] as u64) << 0 * 8)
 }
 
-fn script_for_p2wpkh(key: &PublicKey) -> Script {
+fn get_p2wpkh_redeemscript(key: &PublicKey) -> Script {
 	Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
 		.push_slice(&WPubkeyHash::hash(&key.serialize())[..])
 		.into_script()
@@ -1435,7 +1450,7 @@ mod tests {
 	use super::CounterpartyCommitmentSecrets;
 	use ::{hex, chain};
 	use prelude::*;
-	use ln::chan_utils::{CommitmentTransaction, TxCreationKeys, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, HTLCOutputInCommitment};
+	use ln::chan_utils::{get_to_countersignatory_with_anchors_redeemscript, get_p2wpkh_redeemscript, CommitmentTransaction, TxCreationKeys, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, HTLCOutputInCommitment};
 	use bitcoin::secp256k1::{PublicKey, SecretKey, Secp256k1};
 	use util::test_utils;
 	use chain::keysinterface::{KeysInterface, BaseSign};
@@ -1478,6 +1493,7 @@ mod tests {
 			&mut htlcs_with_aux, &channel_parameters.as_holder_broadcastable()
 		);
 		assert_eq!(tx.built.transaction.output.len(), 2);
+		assert_eq!(tx.built.transaction.output[1].script_pubkey, get_p2wpkh_redeemscript(&counterparty_pubkeys.payment_point));
 
 		// Generate broadcaster and counterparty outputs as well as two anchors
 		let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
@@ -1489,6 +1505,7 @@ mod tests {
 			&mut htlcs_with_aux, &channel_parameters.as_holder_broadcastable()
 		);
 		assert_eq!(tx.built.transaction.output.len(), 4);
+		assert_eq!(tx.built.transaction.output[3].script_pubkey, get_to_countersignatory_with_anchors_redeemscript(&counterparty_pubkeys.payment_point).to_v0_p2wsh());
 
 		// Generate broadcaster output and anchor
 		let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(