From 6296eb1c5f607251b09188f2073d4c35bc394d24 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Fri, 7 Feb 2020 17:48:46 -0500
Subject: [PATCH] Track counterparty's commitment secrets in Channel directly.

In the process of removing a local ChannelMonitor in each Channel,
we need to track our counterpartys' commitment secrets so that we
can check them locally instead of calling our channel monitor to
do that work for us.
---
 lightning/src/ln/channel.rs | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index d9805933..5a1e6f26 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -20,7 +20,7 @@ use ln::msgs;
 use ln::msgs::{DecodeError, OptionalField, DataLossProtect};
 use ln::channelmonitor::ChannelMonitor;
 use ln::channelmanager::{PendingHTLCStatus, HTLCSource, HTLCFailReason, HTLCFailureMsg, PendingHTLCInfo, RAACommitmentOrder, PaymentPreimage, PaymentHash, BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
-use ln::chan_utils::{LocalCommitmentTransaction, TxCreationKeys, HTLCOutputInCommitment, HTLC_SUCCESS_TX_WEIGHT, HTLC_TIMEOUT_TX_WEIGHT, make_funding_redeemscript, ChannelPublicKeys};
+use ln::chan_utils::{CounterpartyCommitmentSecrets, LocalCommitmentTransaction, TxCreationKeys, HTLCOutputInCommitment, HTLC_SUCCESS_TX_WEIGHT, HTLC_TIMEOUT_TX_WEIGHT, make_funding_redeemscript, ChannelPublicKeys};
 use ln::chan_utils;
 use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
 use chain::transaction::OutPoint;
@@ -348,6 +348,7 @@ pub(super) struct Channel<ChanSigner: ChannelKeys> {
 	their_shutdown_scriptpubkey: Option<Script>,
 
 	channel_monitor: ChannelMonitor<ChanSigner>,
+	commitment_secrets: CounterpartyCommitmentSecrets,
 
 	network_sync: UpdateStatus,
 
@@ -523,6 +524,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			their_shutdown_scriptpubkey: None,
 
 			channel_monitor: channel_monitor,
+			commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
 			network_sync: UpdateStatus::Fresh,
 
@@ -743,6 +745,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			their_shutdown_scriptpubkey,
 
 			channel_monitor: channel_monitor,
+			commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
 			network_sync: UpdateStatus::Fresh,
 
@@ -1451,7 +1454,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			// channel.
 			return Err(ChannelError::Close("Received funding_created after we got the channel!"));
 		}
-		if self.channel_monitor.get_min_seen_secret() != (1 << 48) ||
+		if self.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
 				self.cur_remote_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
 				self.cur_local_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
 			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
@@ -1493,7 +1496,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		if self.channel_state & !(ChannelState::MonitorUpdateFailed as u32) != ChannelState::FundingCreated as u32 {
 			return Err(ChannelError::Close("Received funding_signed in strange state!"));
 		}
-		if self.channel_monitor.get_min_seen_secret() != (1 << 48) ||
+		if self.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
 				self.cur_remote_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER - 1 ||
 				self.cur_local_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
 			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
@@ -2002,8 +2005,10 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 				return Err(ChannelError::Close("Got a revoke commitment secret which didn't correspond to their current pubkey"));
 			}
 		}
+		self.commitment_secrets.provide_secret(self.cur_remote_commitment_transaction_number + 1, msg.per_commitment_secret)
+			.map_err(|_| ChannelError::Close("Previous secrets did not match new one"))?;
 		self.channel_monitor.provide_secret(self.cur_remote_commitment_transaction_number + 1, msg.per_commitment_secret)
-			.map_err(|e| ChannelError::Close(e.0))?;
+			.unwrap();
 
 		if self.channel_state & ChannelState::AwaitingRemoteRevoke as u32 == 0 {
 			// Our counterparty seems to have burned their coins to us (by revoking a state when we
@@ -3198,7 +3203,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		if self.channel_state != (ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32) {
 			panic!("Tried to get a funding_created messsage at a time other than immediately after initial handshake completion (or tried to get funding_created twice)");
 		}
-		if self.channel_monitor.get_min_seen_secret() != (1 << 48) ||
+		if self.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
 				self.cur_remote_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
 				self.cur_local_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
 			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
@@ -3277,7 +3282,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		assert_eq!(self.channel_state & ChannelState::PeerDisconnected as u32, ChannelState::PeerDisconnected as u32);
 		assert_ne!(self.cur_remote_commitment_transaction_number, INITIAL_COMMITMENT_NUMBER);
 		let data_loss_protect = if self.cur_remote_commitment_transaction_number + 1 < INITIAL_COMMITMENT_NUMBER {
-			let remote_last_secret = self.channel_monitor.get_secret(self.cur_remote_commitment_transaction_number + 2).unwrap();
+			let remote_last_secret = self.commitment_secrets.get_secret(self.cur_remote_commitment_transaction_number + 2).unwrap();
 			log_trace!(self, "Enough info to generate a Data Loss Protect with per_commitment_secret {}", log_bytes!(remote_last_secret));
 			OptionalField::Present(DataLossProtect {
 				your_last_per_commitment_secret: remote_last_secret,
@@ -3835,6 +3840,8 @@ impl<ChanSigner: ChannelKeys + Writeable> Writeable for Channel<ChanSigner> {
 
 		write_option!(self.their_shutdown_scriptpubkey);
 
+		self.commitment_secrets.write(writer)?;
+
 		self.channel_monitor.write_for_disk(writer)?;
 		Ok(())
 	}
@@ -3984,6 +3991,8 @@ impl<R : ::std::io::Read, ChanSigner: ChannelKeys + Readable<R>> ReadableArgs<R,
 		let their_node_id = Readable::read(reader)?;
 
 		let their_shutdown_scriptpubkey = Readable::read(reader)?;
+		let commitment_secrets = Readable::read(reader)?;
+
 		let (monitor_last_block, channel_monitor) = ReadableArgs::read(reader, logger.clone())?;
 		// We drop the ChannelMonitor's last block connected hash cause we don't actually bother
 		// doing full block connection operations on the internal ChannelMonitor copies
@@ -4059,6 +4068,7 @@ impl<R : ::std::io::Read, ChanSigner: ChannelKeys + Readable<R>> ReadableArgs<R,
 			their_shutdown_scriptpubkey,
 
 			channel_monitor,
+			commitment_secrets,
 
 			network_sync: UpdateStatus::Fresh,
 
-- 
2.30.2