Use SINGLE|ACP sighash on signatures from peer in 0FC channels

Co-authored-by: Matt Corallo <[email protected]>

Author: tankyleo

lightning/src/ln/chan_utils.rs

@@ -869,7 +869,9 @@ pub fn build_htlc_input_witness(
 	local_sig: &Signature, remote_sig: &Signature, preimage: &Option<PaymentPreimage>,
 	redeem_script: &Script, channel_type_features: &ChannelTypeFeatures,
 ) -> Witness {
-	let remote_sighash_type = if channel_type_features.supports_anchors_zero_fee_htlc_tx() {
+	let remote_sighash_type = if channel_type_features.supports_anchors_zero_fee_htlc_tx()
+		|| channel_type_features.supports_anchor_zero_fee_commitments()
+	{
 		EcdsaSighashType::SinglePlusAnyoneCanPay
 	} else {
 		EcdsaSighashType::All

lightning/src/ln/channel.rs

@@ -4671,7 +4671,9 @@ where
 
 			let htlc_redeemscript =
 				chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
-			let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx()
+			let channel_type = funding.get_channel_type();
+			let htlc_sighashtype = if channel_type.supports_anchors_zero_fee_htlc_tx()
+				|| channel_type.supports_anchor_zero_fee_commitments()
 			{
 				EcdsaSighashType::SinglePlusAnyoneCanPay
 			} else {

lightning/src/sign/mod.rs

@@ -1472,7 +1472,9 @@ impl EcdsaChannelSigner for InMemorySigner {
 				&keys.revocation_key,
 			);
 			let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, chan_type, &keys);
-			let htlc_sighashtype = if chan_type.supports_anchors_zero_fee_htlc_tx() {
+			let htlc_sighashtype = if chan_type.supports_anchors_zero_fee_htlc_tx()
+				|| chan_type.supports_anchor_zero_fee_commitments()
+			{
 				EcdsaSighashType::SinglePlusAnyoneCanPay
 			} else {
 				EcdsaSighashType::All

lightning/src/util/test_channel_signer.rs

@@ -386,7 +386,9 @@ impl EcdsaChannelSigner for TestChannelSigner {
 			let channel_parameters =
 				&htlc_descriptor.channel_derivation_parameters.transaction_parameters;
 			let channel_type_features = &channel_parameters.channel_type_features;
-			let sighash_type = if channel_type_features.supports_anchors_zero_fee_htlc_tx() {
+			let sighash_type = if channel_type_features.supports_anchors_zero_fee_htlc_tx()
+				|| channel_type_features.supports_anchor_zero_fee_commitments()
+			{
 				EcdsaSighashType::SinglePlusAnyoneCanPay
 			} else {
 				EcdsaSighashType::All