Add ChannelSigner::spend_holder_anchor_input

lightning/src/events/bump_transaction.rs

@@ -687,8 +687,7 @@ where
 			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)?;
-			anchor_tx.input[0].witness = anchor_descriptor.tx_input_witness(&anchor_sig);
+			anchor_tx = signer.spend_holder_anchor_input(&anchor_tx, 0, &self.secp)?;
 
 			#[cfg(debug_assertions)] {
 				let signed_tx_weight = anchor_tx.weight().to_wu();

lightning/src/sign/mod.rs

@@ -964,6 +964,11 @@ pub trait ChannelSigner {
 
 	/// Get the counterparty anchor output of a commit tx
 	fn get_counterparty_anchor_txout(&self, is_holder_tx: bool) -> Option<TxOut>;
+
+	/// Spend the holder anchor input
+	fn spend_holder_anchor_input(
+		&self, anchor_tx: &Transaction, input_idx: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+	) -> Result<Transaction, ()>;
 }
 
 /// Specifies the recipient of an invoice.
@@ -1891,6 +1896,18 @@ impl ChannelSigner for InMemorySigner {
 			None
 		}
 	}
+
+	fn spend_holder_anchor_input(
+		&self, anchor_tx: &Transaction, input_idx: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+	) -> Result<Transaction, ()> {
+		let anchor_sig =
+			EcdsaChannelSigner::sign_holder_anchor_input(self, anchor_tx, input_idx, secp_ctx)?;
+		let mut tx = anchor_tx.clone();
+		let funding_pubkey = self.pubkeys().funding_pubkey;
+		let witness = chan_utils::build_anchor_input_witness(&funding_pubkey, &anchor_sig);
+		tx.input[0].witness = witness;
+		Ok(tx)
+	}
 }
 
 const MISSING_PARAMS_ERR: &'static str =

lightning/src/util/test_channel_signer.rs

@@ -365,6 +365,12 @@ impl ChannelSigner for TestChannelSigner {
 	fn get_counterparty_anchor_txout(&self, is_holder_tx: bool) -> Option<TxOut> {
 		self.inner.get_counterparty_anchor_txout(is_holder_tx)
 	}
+
+	fn spend_holder_anchor_input(
+		&self, anchor_tx: &Transaction, input_idx: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+	) -> Result<Transaction, ()> {
+		self.inner.spend_holder_anchor_input(anchor_tx, input_idx, secp_ctx)
+	}
 }
 
 impl EcdsaChannelSigner for TestChannelSigner {