Cache remote basepoint and remote_csv in new OnchainTxHandler::RemoteTxCache

Used in next commits to avoid passing script between ChannelMonitor
and OnchainTxHandler. ChannelMonitor duplicata will be removed
in future commits.

Author: Antoine Riard

lightning/src/ln/channelmonitor.rs

@@ -1064,7 +1064,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		let our_channel_close_key_hash = Hash160::hash(&shutdown_pubkey.serialize());
 		let shutdown_script = Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&our_channel_close_key_hash[..]).into_script();
 
-		let mut onchain_tx_handler = OnchainTxHandler::new(destination_script.clone(), keys.clone(), their_to_self_delay, logger.clone());
+		let mut onchain_tx_handler = OnchainTxHandler::new(destination_script.clone(), keys.clone(), their_to_self_delay, their_delayed_payment_base_key.clone(), their_htlc_base_key.clone(), our_to_self_delay, logger.clone());
 
 		let local_tx_sequence = initial_local_commitment_tx.unsigned_tx.input[0].sequence as u64;
 		let local_tx_locktime = initial_local_commitment_tx.unsigned_tx.lock_time as u64;
@@ -1099,8 +1099,8 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 			current_remote_commitment_txid: None,
 			prev_remote_commitment_txid: None,
 
-			their_htlc_base_key: their_htlc_base_key.clone(),
-			their_delayed_payment_base_key: their_delayed_payment_base_key.clone(),
+			their_htlc_base_key: *their_htlc_base_key,
+			their_delayed_payment_base_key: *their_delayed_payment_base_key,
 			funding_redeemscript,
 			channel_value_satoshis: channel_value_satoshis,
 			their_cur_revocation_points: None,

lightning/src/ln/onchaintx.rs

@@ -11,6 +11,7 @@ use bitcoin::util::bip143;
 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
 
 use secp256k1::{Secp256k1, Signature};
+use secp256k1::key::PublicKey;
 use secp256k1;
 
 use ln::msgs::DecodeError;
@@ -48,6 +49,13 @@ enum OnchainEvent {
 	}
 }
 
+/// Cache remote basepoint to compute any transaction on
+/// remote outputs, either justice or preimage/timeout transactions.
+struct RemoteTxCache {
+	remote_delayed_payment_base_key: PublicKey,
+	remote_htlc_base_key: PublicKey
+}
+
 /// Higher-level cache structure needed to re-generate bumped claim txn if needed
 #[derive(Clone, PartialEq)]
 pub struct ClaimTxBumpMaterial {
@@ -195,6 +203,8 @@ pub struct OnchainTxHandler<ChanSigner: ChannelKeys> {
 	prev_local_commitment: Option<LocalCommitmentTransaction>,
 	prev_local_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,
 	local_csv: u16,
+	remote_tx_cache: RemoteTxCache,
+	remote_csv: u16,
 
 	key_storage: ChanSigner,
 
@@ -241,6 +251,10 @@ impl<ChanSigner: ChannelKeys + Writeable> OnchainTxHandler<ChanSigner> {
 
 		self.local_csv.write(writer)?;
 
+		self.remote_tx_cache.remote_delayed_payment_base_key.write(writer)?;
+		self.remote_tx_cache.remote_htlc_base_key.write(writer)?;
+		self.remote_csv.write(writer)?;
+
 		self.key_storage.write(writer)?;
 
 		writer.write_all(&byte_utils::be64_to_array(self.pending_claim_requests.len() as u64))?;
@@ -289,6 +303,16 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 
 		let local_csv = Readable::read(reader)?;
 
+		let remote_tx_cache = {
+			let remote_delayed_payment_base_key = Readable::read(reader)?;
+			let remote_htlc_base_key = Readable::read(reader)?;
+			RemoteTxCache {
+				remote_delayed_payment_base_key,
+				remote_htlc_base_key,
+			}
+		};
+		let remote_csv = Readable::read(reader)?;
+
 		let key_storage = Readable::read(reader)?;
 
 		let pending_claim_requests_len: u64 = Readable::read(reader)?;
@@ -341,6 +365,8 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 			prev_local_commitment,
 			prev_local_htlc_sigs,
 			local_csv,
+			remote_tx_cache,
+			remote_csv,
 			key_storage,
 			claimable_outpoints,
 			pending_claim_requests,
@@ -352,17 +378,24 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 }
 
 impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
-	pub(super) fn new(destination_script: Script, keys: ChanSigner, local_csv: u16, logger: Arc<Logger>) -> Self {
+	pub(super) fn new(destination_script: Script, keys: ChanSigner, local_csv: u16, remote_delayed_payment_base_key: PublicKey, remote_htlc_base_key: PublicKey, remote_csv: u16, logger: Arc<Logger>) -> Self {
 
 		let key_storage = keys;
 
+		let remote_tx_cache = RemoteTxCache {
+			remote_delayed_payment_base_key,
+			remote_htlc_base_key,
+		};
+
 		OnchainTxHandler {
 			destination_script,
 			local_commitment: None,
 			local_htlc_sigs: None,
 			prev_local_commitment: None,
 			prev_local_htlc_sigs: None,
 			local_csv,
+			remote_tx_cache,
+			remote_csv,
 			key_storage,
 			pending_claim_requests: HashMap::new(),
 			claimable_outpoints: HashMap::new(),