Add InMemorySigner::overwrite_channel_parameters

Builds of `CommitmentTransaction` now query a `ChannelSigner` for the
script pubkey to use in the `to_remote` output of the commitment
transaction. So we need to overwrite the `ChannelTransactionParameters`
of a `ChannelSigner` anytime we want to build a new commitment
transaction with a different set of features.

This is feature is only used in tests, so we cfg-gate it behind the
test flag.

Author: tankyleo

lightning/src/ln/chan_utils.rs

@@ -1896,7 +1896,7 @@ pub fn get_commitment_transaction_number_obscure_factor(
 mod tests {
 	use super::{CounterpartyCommitmentSecrets, ChannelPublicKeys};
 	use crate::chain;
-	use crate::ln::chan_utils::{get_counterparty_payment_script, get_htlc_redeemscript, get_to_countersignatory_with_anchors_redeemscript, CommitmentTransaction, TxCreationKeys, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, HTLCOutputInCommitment};
+	use crate::ln::chan_utils::{get_htlc_redeemscript, get_to_countersignatory_with_anchors_redeemscript, CommitmentTransaction, TxCreationKeys, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, HTLCOutputInCommitment};
 	use bitcoin::secp256k1::{PublicKey, SecretKey, Secp256k1};
 	use crate::util::test_utils;
 	use crate::sign::{ChannelSigner, SignerProvider};
@@ -1906,6 +1906,7 @@ mod tests {
 	use crate::types::payment::PaymentHash;
 	use bitcoin::PublicKey as BitcoinPublicKey;
 	use crate::types::features::ChannelTypeFeatures;
+	use crate::util::test_channel_signer::TestChannelSigner;
 
 	#[allow(unused_imports)]
 	use crate::prelude::*;
@@ -1919,6 +1920,7 @@ mod tests {
 		htlcs_with_aux: Vec<(HTLCOutputInCommitment, ())>,
 		channel_parameters: ChannelTransactionParameters,
 		counterparty_pubkeys: ChannelPublicKeys,
+		signer: TestChannelSigner,
 	}
 
 	impl TestCommitmentTxBuilder {
@@ -1927,15 +1929,13 @@ mod tests {
 			let seed = [42; 32];
 			let network = Network::Testnet;
 			let keys_provider = test_utils::TestKeysInterface::new(&seed, network);
-			let signer = keys_provider.derive_channel_signer(3000, keys_provider.generate_channel_keys_id(false, 1_000_000, 0));
+			let mut signer = keys_provider.derive_channel_signer(3000, keys_provider.generate_channel_keys_id(false, 1_000_000, 0));
 			let counterparty_signer = keys_provider.derive_channel_signer(3000, keys_provider.generate_channel_keys_id(true, 1_000_000, 1));
-			let delayed_payment_base = &signer.pubkeys().delayed_payment_basepoint;
 			let per_commitment_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("1f1e1d1c1b1a191817161514131211100f0e0d0c0b0a09080706050403020100").unwrap()[..]).unwrap();
 			let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);
-			let htlc_basepoint = &signer.pubkeys().htlc_basepoint;
-			let holder_pubkeys = signer.pubkeys();
+			let holder_pubkeys = signer.pubkeys().clone();
 			let counterparty_pubkeys = counterparty_signer.pubkeys().clone();
-			let keys = TxCreationKeys::derive_new(&secp_ctx, &per_commitment_point, delayed_payment_base, htlc_basepoint, &counterparty_pubkeys.revocation_basepoint, &counterparty_pubkeys.htlc_basepoint);
+			let keys = TxCreationKeys::from_channel_static_keys(&per_commitment_point, &holder_pubkeys, &counterparty_pubkeys, &secp_ctx);
 			let channel_parameters = ChannelTransactionParameters {
 				holder_pubkeys: holder_pubkeys.clone(),
 				holder_selected_contest_delay: 0,
@@ -1944,6 +1944,7 @@ mod tests {
 				funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
 				channel_type_features: ChannelTypeFeatures::only_static_remote_key(),
 			};
+			signer.provide_channel_parameters(&channel_parameters);
 			let htlcs_with_aux = Vec::new();
 
 			Self {
@@ -1955,12 +1956,12 @@ mod tests {
 				htlcs_with_aux,
 				channel_parameters,
 				counterparty_pubkeys,
+				signer,
 			}
 		}
 
 		fn build(&mut self, to_broadcaster_sats: u64, to_countersignatory_sats: u64) -> CommitmentTransaction {
-			let channel_parameters = self.channel_parameters.as_holder_broadcastable();
-			let counterparty_payment_script = get_counterparty_payment_script(&channel_parameters.channel_type_features(), &channel_parameters.countersignatory_pubkeys().payment_point);
+			let counterparty_payment_script = self.signer.get_counterparty_payment_script(false);
 			let counterparty_txout = TxOut {
 				script_pubkey: counterparty_payment_script,
 				value: Amount::from_sat(to_countersignatory_sats),
@@ -1972,9 +1973,14 @@ mod tests {
 				self.holder_funding_pubkey.clone(),
 				self.counterparty_funding_pubkey.clone(),
 				self.keys.clone(), self.feerate_per_kw,
-				&mut self.htlcs_with_aux, &channel_parameters,
+				&mut self.htlcs_with_aux, &self.channel_parameters.as_holder_broadcastable(),
 			)
 		}
+
+		fn overwrite_channel_features(&mut self, channel_type_features: ChannelTypeFeatures) {
+			self.channel_parameters.channel_type_features = channel_type_features;
+			self.signer.overwrite_channel_parameters(&self.channel_parameters);
+		}
 	}
 
 	#[test]
@@ -1987,7 +1993,7 @@ mod tests {
 		assert_eq!(tx.built.transaction.output[1].script_pubkey, bitcoin::address::Address::p2wpkh(&CompressedPublicKey(builder.counterparty_pubkeys.payment_point), Network::Testnet).script_pubkey());
 
 		// Generate broadcaster and counterparty outputs as well as two anchors
-		builder.channel_parameters.channel_type_features = ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies();
+		builder.overwrite_channel_features(ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies());
 		let tx = builder.build(1000, 2000);
 		assert_eq!(tx.built.transaction.output.len(), 4);
 		assert_eq!(tx.built.transaction.output[3].script_pubkey, get_to_countersignatory_with_anchors_redeemscript(&builder.counterparty_pubkeys.payment_point).to_p2wsh());
@@ -2017,7 +2023,7 @@ mod tests {
 		};
 
 		// Generate broadcaster output and received and offered HTLC outputs,  w/o anchors
-		builder.channel_parameters.channel_type_features = ChannelTypeFeatures::only_static_remote_key();
+		builder.overwrite_channel_features(ChannelTypeFeatures::only_static_remote_key());
 		builder.htlcs_with_aux = vec![(received_htlc.clone(), ()), (offered_htlc.clone(), ())];
 		let tx = builder.build(3000, 0);
 		let keys = &builder.keys.clone();
@@ -2030,7 +2036,7 @@ mod tests {
 				   "0020215d61bba56b19e9eadb6107f5a85d7f99c40f65992443f69229c290165bc00d");
 
 		// Generate broadcaster output and received and offered HTLC outputs,  with anchors
-		builder.channel_parameters.channel_type_features = ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies();
+		builder.overwrite_channel_features(ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies());
 		builder.htlcs_with_aux = vec![(received_htlc.clone(), ()), (offered_htlc.clone(), ())];
 		let tx = builder.build(3000, 0);
 		assert_eq!(tx.built.transaction.output.len(), 5);

lightning/src/ln/channel.rs

@@ -10917,19 +10917,17 @@ mod tests {
 		macro_rules! test_commitment {
 			( $counterparty_sig_hex: expr, $sig_hex: expr, $tx_hex: expr, $($remain:tt)* ) => {
 				chan.context.channel_transaction_parameters.channel_type_features = ChannelTypeFeatures::only_static_remote_key();
-				let mut holder_signer = keys_provider.derive_channel_signer(chan.context.channel_value_satoshis, chan.context.channel_keys_id);
-				holder_signer.provide_channel_parameters(&chan.context.channel_transaction_parameters);
-				chan.context.holder_signer = ChannelSignerType::Ecdsa(holder_signer);
+				let mut_signer = chan.context.holder_signer.as_mut_ecdsa().unwrap();
+				mut_signer.overwrite_channel_parameters(&chan.context.channel_transaction_parameters);
 				test_commitment_common!($counterparty_sig_hex, $sig_hex, $tx_hex, &ChannelTypeFeatures::only_static_remote_key(), $($remain)*);
 			};
 		}
 
 		macro_rules! test_commitment_with_anchors {
 			( $counterparty_sig_hex: expr, $sig_hex: expr, $tx_hex: expr, $($remain:tt)* ) => {
 				chan.context.channel_transaction_parameters.channel_type_features = ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies();
-				let mut holder_signer = keys_provider.derive_channel_signer(chan.context.channel_value_satoshis, chan.context.channel_keys_id);
-				holder_signer.provide_channel_parameters(&chan.context.channel_transaction_parameters);
-				chan.context.holder_signer = ChannelSignerType::Ecdsa(holder_signer);
+				let mut_signer = chan.context.holder_signer.as_mut_ecdsa().unwrap();
+				mut_signer.overwrite_channel_parameters(&chan.context.channel_transaction_parameters);
 				test_commitment_common!($counterparty_sig_hex, $sig_hex, $tx_hex, &ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies(), $($remain)*);
 			};
 		}

lightning/src/sign/mod.rs

@@ -1334,6 +1334,14 @@ impl InMemorySigner {
 			witness_script.as_bytes(),
 		]))
 	}
+
+	#[cfg(test)]
+	pub(crate) fn overwrite_channel_parameters(
+		&mut self, channel_parameters: &ChannelTransactionParameters,
+	) {
+		assert!(channel_parameters.is_populated(), "Channel parameters must be fully populated");
+		self.channel_parameters = Some(channel_parameters.clone());
+	}
 }
 
 impl EntropySource for InMemorySigner {

lightning/src/util/test_channel_signer.rs

@@ -162,6 +162,11 @@ impl TestChannelSigner {
 	fn is_signer_available(&self, signer_op: SignerOp) -> bool {
 		!self.get_enforcement_state().disabled_signer_ops.contains(&signer_op)
 	}
+
+	#[cfg(test)]
+	pub(crate) fn overwrite_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
+		self.inner.overwrite_channel_parameters(channel_parameters)
+	}
 }
 
 impl ChannelSigner for TestChannelSigner {