Enable monitor to rebuild initial counterparty commitment tx
[rust-lightning] / lightning / src / chain / channelmonitor.rs
index 3f26bdf2832c393e6cf99976149f9cf28a003ccb..0c207fa8b17429b32e31f1eda65ea0270dcdad82 100644 (file)
@@ -33,10 +33,11 @@ use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
 use bitcoin::secp256k1::{SecretKey, PublicKey};
 use bitcoin::secp256k1;
 
+use crate::ln::channel::INITIAL_COMMITMENT_NUMBER;
 use crate::ln::{PaymentHash, PaymentPreimage};
 use crate::ln::msgs::DecodeError;
 use crate::ln::chan_utils;
-use crate::ln::chan_utils::{CounterpartyCommitmentSecrets, HTLCOutputInCommitment, HTLCClaim, ChannelTransactionParameters, HolderCommitmentTransaction};
+use crate::ln::chan_utils::{CommitmentTransaction, CounterpartyCommitmentSecrets, HTLCOutputInCommitment, HTLCClaim, ChannelTransactionParameters, HolderCommitmentTransaction, TxCreationKeys};
 use crate::ln::channelmanager::{HTLCSource, SentHTLCId};
 use crate::chain;
 use crate::chain::{BestBlock, WatchedOutput};
@@ -502,6 +503,9 @@ pub(crate) enum ChannelMonitorUpdateStep {
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
                commitment_number: u64,
                their_per_commitment_point: PublicKey,
+               feerate_per_kw: Option<u32>,
+               to_broadcaster_value_sat: Option<u64>,
+               to_countersignatory_value_sat: Option<u64>,
        },
        PaymentPreimage {
                payment_preimage: PaymentPreimage,
@@ -544,8 +548,11 @@ impl_writeable_tlv_based_enum_upgradable!(ChannelMonitorUpdateStep,
        },
        (1, LatestCounterpartyCommitmentTXInfo) => {
                (0, commitment_txid, required),
+               (1, feerate_per_kw, option),
                (2, commitment_number, required),
+               (3, to_broadcaster_value_sat, option),
                (4, their_per_commitment_point, required),
+               (5, to_countersignatory_value_sat, option),
                (6, htlc_outputs, required_vec),
        },
        (2, PaymentPreimage) => {
@@ -882,6 +889,14 @@ pub(crate) struct ChannelMonitorImpl<Signer: WriteableEcdsaChannelSigner> {
 
        /// The node_id of our counterparty
        counterparty_node_id: Option<PublicKey>,
+
+       /// Initial counterparty commmitment data needed to recreate the commitment tx
+       /// in the persistence pipeline for third-party watchtowers. This will only be present on
+       /// monitors created after 0.0.117.
+       ///
+       /// Ordering of tuple data: (their_per_commitment_point, feerate_per_kw, to_broadcaster_sats,
+       /// to_countersignatory_sats)
+       initial_counterparty_commitment_info: Option<(PublicKey, u32, u64, u64)>,
 }
 
 /// Transaction outputs to watch for on-chain spends.
@@ -1072,6 +1087,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for ChannelMonitorImpl<Signe
                        (11, self.confirmed_commitment_tx_counterparty_output, option),
                        (13, self.spendable_txids_confirmed, required_vec),
                        (15, self.counterparty_fulfilled_htlcs, required),
+                       (17, self.initial_counterparty_commitment_info, option),
                });
 
                Ok(())
@@ -1222,6 +1238,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 
                        best_block,
                        counterparty_node_id: Some(counterparty_node_id),
+                       initial_counterparty_commitment_info: None,
                })
        }
 
@@ -1230,11 +1247,31 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
                self.inner.lock().unwrap().provide_secret(idx, secret)
        }
 
+       /// A variant of `Self::provide_latest_counterparty_commitment_tx` used to provide
+       /// additional information to the monitor to store in order to recreate the initial
+       /// counterparty commitment transaction during persistence (mainly for use in third-party
+       /// watchtowers).
+       ///
+       /// This is used to provide the counterparty commitment information directly to the monitor
+       /// before the initial persistence of a new channel.
+       pub(crate) fn provide_initial_counterparty_commitment_tx<L: Deref>(
+               &self, txid: Txid, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
+               commitment_number: u64, their_cur_per_commitment_point: PublicKey, feerate_per_kw: u32,
+               to_broadcaster_value_sat: u64, to_countersignatory_value_sat: u64, logger: &L,
+       )
+       where L::Target: Logger
+       {
+               self.inner.lock().unwrap().provide_initial_counterparty_commitment_tx(txid,
+                       htlc_outputs, commitment_number, their_cur_per_commitment_point, feerate_per_kw,
+                       to_broadcaster_value_sat, to_countersignatory_value_sat, logger);
+       }
+
        /// Informs this monitor of the latest counterparty (ie non-broadcastable) commitment transaction.
        /// The monitor watches for it to be broadcasted and then uses the HTLC information (and
        /// possibly future revocation/preimage information) to claim outputs where possible.
        /// We cache also the mapping hash:commitment number to lighten pruning of old preimages by watchtowers.
-       pub(crate) fn provide_latest_counterparty_commitment_tx<L: Deref>(
+       #[cfg(test)]
+       fn provide_latest_counterparty_commitment_tx<L: Deref>(
                &self,
                txid: Txid,
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
@@ -1370,6 +1407,45 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
                ret
        }
 
+       /// Gets the counterparty's initial commitment transaction. The returned commitment
+       /// transaction is unsigned. This is intended to be called during the initial persistence of
+       /// the monitor (inside an implementation of [`Persist::persist_new_channel`]), to allow for
+       /// watchtowers in the persistence pipeline to have enough data to form justice transactions.
+       ///
+       /// This is similar to [`Self::counterparty_commitment_txs_from_update`], except
+       /// that for the initial commitment transaction, we don't have a corresponding update.
+       ///
+       /// This will only return `Some` for channel monitors that have been created after upgrading
+       /// to LDK 0.0.117+.
+       ///
+       /// [`Persist::persist_new_channel`]: crate::chain::chainmonitor::Persist::persist_new_channel
+       pub fn initial_counterparty_commitment_tx(&self) -> Option<CommitmentTransaction> {
+               self.inner.lock().unwrap().initial_counterparty_commitment_tx()
+       }
+
+       /// Gets all of the counterparty commitment transactions provided by the given update. This
+       /// may be empty if the update doesn't include any new counterparty commitments. Returned
+       /// commitment transactions are unsigned.
+       ///
+       /// This is provided so that watchtower clients in the persistence pipeline are able to build
+       /// justice transactions for each counterparty commitment upon each update. It's intended to be
+       /// used within an implementation of [`Persist::update_persisted_channel`], which is provided
+       /// with a monitor and an update.
+       ///
+       /// It is expected that a watchtower client may use this method to retrieve the latest counterparty
+       /// commitment transaction(s), and then hold the necessary data until a later update in which
+       /// the monitor has been updated with the corresponding revocation data, at which point the
+       /// monitor can sign the justice transaction.
+       ///
+       /// This will only return a non-empty list for monitor updates that have been created after
+       /// upgrading to LDK 0.0.117+. Note that no restriction lies on the monitors themselves, which
+       /// may have been created prior to upgrading.
+       ///
+       /// [`Persist::update_persisted_channel`]: crate::chain::chainmonitor::Persist::update_persisted_channel
+       pub fn counterparty_commitment_txs_from_update(&self, update: &ChannelMonitorUpdate) -> Vec<CommitmentTransaction> {
+               self.inner.lock().unwrap().counterparty_commitment_txs_from_update(update)
+       }
+
        pub(crate) fn get_min_seen_secret(&self) -> u64 {
                self.inner.lock().unwrap().get_min_seen_secret()
        }
@@ -2226,6 +2302,25 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
                Ok(())
        }
 
+       pub(crate) fn provide_initial_counterparty_commitment_tx<L: Deref>(
+               &mut self, txid: Txid, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
+               commitment_number: u64, their_per_commitment_point: PublicKey, feerate_per_kw: u32,
+               to_broadcaster_value: u64, to_countersignatory_value: u64, logger: &L
+       )
+       where L::Target: Logger
+       {
+               self.initial_counterparty_commitment_info = Some((their_per_commitment_point.clone(),
+                       feerate_per_kw, to_broadcaster_value, to_countersignatory_value));
+
+               #[cfg(debug_assertions)] {
+                       let rebuilt_commitment_tx = self.initial_counterparty_commitment_tx().unwrap();
+                       debug_assert_eq!(rebuilt_commitment_tx.trust().txid(), txid);
+               }
+
+               self.provide_latest_counterparty_commitment_tx(txid, htlc_outputs, commitment_number,
+                               their_per_commitment_point, logger);
+       }
+
        pub(crate) fn provide_latest_counterparty_commitment_tx<L: Deref>(&mut self, txid: Txid, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>, commitment_number: u64, their_per_commitment_point: PublicKey, logger: &L) where L::Target: Logger {
                // TODO: Encrypt the htlc_outputs data with the single-hash of the commitment transaction
                // so that a remote monitor doesn't learn anything unless there is a malicious close.
@@ -2471,7 +2566,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
                                                ret = Err(());
                                        }
                                }
-                               ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { commitment_txid, htlc_outputs, commitment_number, their_per_commitment_point } => {
+                               ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { commitment_txid, htlc_outputs, commitment_number, their_per_commitment_point, .. } => {
                                        log_trace!(logger, "Updating ChannelMonitor with latest counterparty commitment transaction info");
                                        self.provide_latest_counterparty_commitment_tx(*commitment_txid, htlc_outputs.clone(), *commitment_number, *their_per_commitment_point, logger)
                                },
@@ -2543,6 +2638,10 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
                        }
                }
 
+               #[cfg(debug_assertions)] {
+                       self.counterparty_commitment_txs_from_update(updates);
+               }
+
                // If the updates succeeded and we were in an already closed channel state, then there's no
                // need to refuse any updates we expect to receive afer seeing a confirmed commitment.
                if ret.is_ok() && updates.update_id == CLOSED_CHANNEL_UPDATE_ID && self.latest_update_id == updates.update_id {
@@ -2651,6 +2750,66 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
                ret
        }
 
+       pub(crate) fn initial_counterparty_commitment_tx(&mut self) -> Option<CommitmentTransaction> {
+               let (their_per_commitment_point, feerate_per_kw, to_broadcaster_value,
+                       to_countersignatory_value) = self.initial_counterparty_commitment_info?;
+               let htlc_outputs = vec![];
+
+               let commitment_tx = self.build_counterparty_commitment_tx(INITIAL_COMMITMENT_NUMBER,
+                       &their_per_commitment_point, to_broadcaster_value, to_countersignatory_value,
+                       feerate_per_kw, htlc_outputs);
+               Some(commitment_tx)
+       }
+
+       fn build_counterparty_commitment_tx(
+               &self, commitment_number: u64, their_per_commitment_point: &PublicKey,
+               to_broadcaster_value: u64, to_countersignatory_value: u64, feerate_per_kw: u32,
+               mut nondust_htlcs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>
+       ) -> CommitmentTransaction {
+               let broadcaster_keys = &self.onchain_tx_handler.channel_transaction_parameters
+                       .counterparty_parameters.as_ref().unwrap().pubkeys;
+               let countersignatory_keys =
+                       &self.onchain_tx_handler.channel_transaction_parameters.holder_pubkeys;
+
+               let broadcaster_funding_key = broadcaster_keys.funding_pubkey;
+               let countersignatory_funding_key = countersignatory_keys.funding_pubkey;
+               let keys = TxCreationKeys::from_channel_static_keys(&their_per_commitment_point,
+                       &broadcaster_keys, &countersignatory_keys, &self.onchain_tx_handler.secp_ctx);
+               let channel_parameters =
+                       &self.onchain_tx_handler.channel_transaction_parameters.as_counterparty_broadcastable();
+
+               CommitmentTransaction::new_with_auxiliary_htlc_data(commitment_number,
+                       to_broadcaster_value, to_countersignatory_value, broadcaster_funding_key,
+                       countersignatory_funding_key, keys, feerate_per_kw, &mut nondust_htlcs,
+                       channel_parameters)
+       }
+
+       pub(crate) fn counterparty_commitment_txs_from_update(&self, update: &ChannelMonitorUpdate) -> Vec<CommitmentTransaction> {
+               update.updates.iter().filter_map(|update| {
+                       match update {
+                               &ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { commitment_txid,
+                                       ref htlc_outputs, commitment_number, their_per_commitment_point,
+                                       feerate_per_kw: Some(feerate_per_kw),
+                                       to_broadcaster_value_sat: Some(to_broadcaster_value),
+                                       to_countersignatory_value_sat: Some(to_countersignatory_value) } => {
+
+                                       let nondust_htlcs = htlc_outputs.iter().filter_map(|(htlc, _)| {
+                                               htlc.transaction_output_index.map(|_| (htlc.clone(), None))
+                                       }).collect::<Vec<_>>();
+
+                                       let commitment_tx = self.build_counterparty_commitment_tx(commitment_number,
+                                                       &their_per_commitment_point, to_broadcaster_value,
+                                                       to_countersignatory_value, feerate_per_kw, nondust_htlcs);
+
+                                       debug_assert_eq!(commitment_tx.trust().txid(), commitment_txid);
+
+                                       Some(commitment_tx)
+                               },
+                               _ => None,
+                       }
+               }).collect()
+       }
+
        /// Can only fail if idx is < get_min_seen_secret
        fn get_secret(&self, idx: u64) -> Option<[u8; 32]> {
                self.commitment_secrets.get_secret(idx)
@@ -3365,7 +3524,8 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
                                OnchainEvent::MaturingOutput { descriptor } => {
                                        log_debug!(logger, "Descriptor {} has got enough confirmations to be passed upstream", log_spendable!(descriptor));
                                        self.pending_events.push(Event::SpendableOutputs {
-                                               outputs: vec![descriptor]
+                                               outputs: vec![descriptor],
+                                               channel_id: Some(self.funding_info.0.to_channel_id()),
                                        });
                                        self.spendable_txids_confirmed.push(entry.txid);
                                },
@@ -4112,6 +4272,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
                let mut confirmed_commitment_tx_counterparty_output = None;
                let mut spendable_txids_confirmed = Some(Vec::new());
                let mut counterparty_fulfilled_htlcs = Some(HashMap::new());
+               let mut initial_counterparty_commitment_info = None;
                read_tlv_fields!(reader, {
                        (1, funding_spend_confirmed, option),
                        (3, htlcs_resolved_on_chain, optional_vec),
@@ -4121,6 +4282,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
                        (11, confirmed_commitment_tx_counterparty_output, option),
                        (13, spendable_txids_confirmed, optional_vec),
                        (15, counterparty_fulfilled_htlcs, option),
+                       (17, initial_counterparty_commitment_info, option),
                });
 
                Ok((best_block.block_hash(), ChannelMonitor::from_impl(ChannelMonitorImpl {
@@ -4176,6 +4338,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 
                        best_block,
                        counterparty_node_id,
+                       initial_counterparty_commitment_info,
                })))
        }
 }