Cache HTLC per_commitment_point in descriptor

[rust-lightning] / lightning / src / events / bump_transaction.rs

diff --git a/lightning/src/events/bump_transaction.rs b/lightning/src/events/bump_transaction.rs
index edb146ba2159f9579dc36aff8789277e040221bb..0e3152d7b0a4c848c2fe5a4a6f07cd37f83db5cd 100644 (file)
--- a/lightning/src/events/bump_transaction.rs
+++ b/lightning/src/events/bump_transaction.rs
@@ -93,6 +93,12 @@ pub struct HTLCDescriptor {
        pub commitment_txid: Txid,
        /// The number of the commitment transaction in which the HTLC output lives.
        pub per_commitment_number: u64,
+       /// The key tweak corresponding to the number of the commitment transaction in which the HTLC
+       /// output lives. This tweak is applied to all the basepoints for both parties in the channel to
+       /// arrive at unique keys per commitment.
+       ///
+       /// See <https://github.com/lightning/bolts/blob/master/03-transactions.md#keys> for more info.
+       pub per_commitment_point: PublicKey,
        /// The details of the HTLC as it appears in the commitment transaction.
        pub htlc: HTLCOutputInCommitment,
        /// The preimage, if `Some`, to claim the HTLC output with. If `None`, the timeout path must be
@@ -111,17 +117,15 @@ impl HTLCDescriptor {
 
        /// Returns the delayed output created as a result of spending the HTLC output in the commitment
        /// transaction.
-       pub fn tx_output<C: secp256k1::Signing + secp256k1::Verification>(
-               &self, per_commitment_point: &PublicKey, secp: &Secp256k1<C>
-       ) -> TxOut {
+       pub fn tx_output<C: secp256k1::Signing + secp256k1::Verification>(&self, secp: &Secp256k1<C>) -> TxOut {
                let channel_params = self.channel_parameters.as_holder_broadcastable();
                let broadcaster_keys = channel_params.broadcaster_pubkeys();
                let counterparty_keys = channel_params.countersignatory_pubkeys();
                let broadcaster_delayed_key = chan_utils::derive_public_key(
-                       secp, per_commitment_point, &broadcaster_keys.delayed_payment_basepoint
+                       secp, &self.per_commitment_point, &broadcaster_keys.delayed_payment_basepoint
                );
                let counterparty_revocation_key = chan_utils::derive_public_revocation_key(
-                       secp, per_commitment_point, &counterparty_keys.revocation_basepoint
+                       secp, &self.per_commitment_point, &counterparty_keys.revocation_basepoint
                );
                chan_utils::build_htlc_output(
                        0 /* feerate_per_kw */, channel_params.contest_delay(), &self.htlc,
@@ -130,20 +134,18 @@ impl HTLCDescriptor {
        }
 
        /// Returns the witness script of the HTLC output in the commitment transaction.
-       pub fn witness_script<C: secp256k1::Signing + secp256k1::Verification>(
-               &self, per_commitment_point: &PublicKey, secp: &Secp256k1<C>
-       ) -> Script {
+       pub fn witness_script<C: secp256k1::Signing + secp256k1::Verification>(&self, secp: &Secp256k1<C>) -> Script {
                let channel_params = self.channel_parameters.as_holder_broadcastable();
                let broadcaster_keys = channel_params.broadcaster_pubkeys();
                let counterparty_keys = channel_params.countersignatory_pubkeys();
                let broadcaster_htlc_key = chan_utils::derive_public_key(
-                       secp, per_commitment_point, &broadcaster_keys.htlc_basepoint
+                       secp, &self.per_commitment_point, &broadcaster_keys.htlc_basepoint
                );
                let counterparty_htlc_key = chan_utils::derive_public_key(
-                       secp, per_commitment_point, &counterparty_keys.htlc_basepoint
+                       secp, &self.per_commitment_point, &counterparty_keys.htlc_basepoint
                );
                let counterparty_revocation_key = chan_utils::derive_public_revocation_key(
-                       secp, per_commitment_point, &counterparty_keys.revocation_basepoint
+                       secp, &self.per_commitment_point, &counterparty_keys.revocation_basepoint
                );
                chan_utils::get_htlc_redeemscript_with_explicit_keys(
                        &self.htlc, &ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies(), &broadcaster_htlc_key, &counterparty_htlc_key,
@@ -696,15 +698,12 @@ where
                let mut signers = HashMap::new();
                let mut must_spend = Vec::with_capacity(htlc_descriptors.len());
                for htlc_descriptor in htlc_descriptors {
-                       let signer = signers.entry(htlc_descriptor.channel_keys_id)
+                       signers.entry(htlc_descriptor.channel_keys_id)
                                .or_insert_with(||
                                        self.signer_provider.derive_channel_signer(
                                                htlc_descriptor.channel_value_satoshis, htlc_descriptor.channel_keys_id,
                                        )
                                );
-                       let per_commitment_point = signer.get_per_commitment_point(
-                               htlc_descriptor.per_commitment_number, &self.secp
-                       );
 
                        let htlc_input = htlc_descriptor.unsigned_tx_input();
                        must_spend.push(Input {
@@ -716,7 +715,7 @@ where
                                },
                        });
                        tx.input.push(htlc_input);
-                       let htlc_output = htlc_descriptor.tx_output(&per_commitment_point, &self.secp);
+                       let htlc_output = htlc_descriptor.tx_output(&self.secp);
                        tx.output.push(htlc_output);
                }
 
@@ -743,10 +742,7 @@ where
                        let htlc_sig = signer.sign_holder_htlc_transaction(
                                &htlc_tx, idx, htlc_descriptor, &self.secp
                        )?;
-                       let per_commitment_point = signer.get_per_commitment_point(
-                               htlc_descriptor.per_commitment_number, &self.secp
-                       );
-                       let witness_script = htlc_descriptor.witness_script(&per_commitment_point, &self.secp);
+                       let witness_script = htlc_descriptor.witness_script(&self.secp);
                        htlc_tx.input[idx].witness = htlc_descriptor.tx_input_witness(&htlc_sig, &witness_script);
                }