f - rotate funding pubkey

Author: jkczyz

lightning/src/ln/channel.rs

@@ -2253,14 +2253,10 @@ impl FundingScope {
 		debug_assert!(post_value_to_self_msat_signed >= 0);
 		let post_value_to_self_msat = post_value_to_self_msat_signed as u64;
 
+		// Rotate the pubkeys using the prev_funding_txid as a tweak
 		let prev_funding_txid = prev_funding.get_funding_txid();
-		// Update the splicing 'tweak', this will rotate the keys in the signer
-		let holder_pubkeys = match &context.holder_signer {
-			ChannelSignerType::Ecdsa(ecdsa) => ecdsa.pubkeys(prev_funding_txid, &context.secp_ctx),
-			// TODO (taproot|arik)
-			#[cfg(taproot)]
-			_ => todo!(),
-		};
+		let holder_pubkeys = context.holder_pubkeys(prev_funding_txid);
+
 		let channel_parameters = &prev_funding.channel_transaction_parameters;
 		let mut post_channel_transaction_parameters = ChannelTransactionParameters {
 			holder_pubkeys,
@@ -2280,7 +2276,7 @@ impl FundingScope {
 			.pubkeys
 			.funding_pubkey = counterparty_funding_pubkey;
 
-		// New reserve values are based on the new channel value, and v2-specific
+		// New reserve values are based on the new channel value and are v2-specific
 		let counterparty_selected_channel_reserve_satoshis = Some(get_v2_channel_reserve_satoshis(
 			post_channel_value,
 			context.counterparty_dust_limit_satoshis,
@@ -3759,6 +3755,16 @@ where
 		return &mut self.holder_signer;
 	}
 
+	/// Returns holder pubkeys to use for the channel.
+	fn holder_pubkeys(&self, prev_funding_txid: Option<Txid>) -> ChannelPublicKeys {
+		match &self.holder_signer {
+			ChannelSignerType::Ecdsa(ecdsa) => ecdsa.pubkeys(prev_funding_txid, &self.secp_ctx),
+			// TODO (taproot|arik)
+			#[cfg(taproot)]
+			_ => todo!(),
+		}
+	}
+
 	/// Only allowed immediately after deserialization if get_outbound_scid_alias returns 0,
 	/// indicating we were written by LDK prior to 0.0.106 which did not set outbound SCID aliases
 	/// or prior to any channel actions during `Channel` initialization.
@@ -10405,9 +10411,10 @@ where
 	fn get_splice_init(
 		&self, our_funding_contribution_satoshis: i64, funding_feerate_per_kw: u32, locktime: u32,
 	) -> msgs::SpliceInit {
-		// TODO(splicing): The exisiting pubkey is reused, but a new one should be generated. See #3542.
-		// Note that channel_keys_id is supposed NOT to change
-		let funding_pubkey = self.funding.get_holder_pubkeys().funding_pubkey.clone();
+		// Rotate the pubkeys using the prev_funding_txid as a tweak
+		let prev_funding_txid = self.funding.get_funding_txid();
+		let funding_pubkey = self.context.holder_pubkeys(prev_funding_txid).funding_pubkey;
+
 		msgs::SpliceInit {
 			channel_id: self.context.channel_id,
 			funding_contribution_satoshis: our_funding_contribution_satoshis,

lightning/src/ln/splicing_tests.rs

@@ -43,7 +43,7 @@ fn test_v1_splice_in() {
 	assert_eq!(channel_id.to_string(), expected_funded_channel_id);
 
 	let expected_initiator_funding_key =
-		"03c21e841cbc0b48197d060c71e116c185fa0ac281b7d0aa5924f535154437ca3b";
+		"020abf01c18d5a2543124a12150d698ebf3a8e17df9993521151a49e115678ceea";
 	let expected_acceptor_funding_key =
 		"039481c28b904cbe12681e79937373fc76245c1b29871028ae60ba3152162c319b";