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Merge pull request lightningdevkit#2623 from wpaulino/htlc-claim-rece…
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…ive-preimage-after-close

Claim HTLCs with preimage from currently confirmed commitment
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@TheBlueMatt
TheBlueMatt committed Sep 29, 2023
2 parents 5e871a7 + d82e6ba commit fbc86cb
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Showing 2 changed files with 180 additions and 12 deletions.
53 changes: 42 additions & 11 deletions lightning/src/chain/channelmonitor.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2503,6 +2503,18 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
{
self.payment_preimages.insert(payment_hash.clone(), payment_preimage.clone());

let confirmed_spend_txid = self.funding_spend_confirmed.or_else(|| {
self.onchain_events_awaiting_threshold_conf.iter().find_map(|event| match event.event {
OnchainEvent::FundingSpendConfirmation { .. } => Some(event.txid),
_ => None,
})
});
let confirmed_spend_txid = if let Some(txid) = confirmed_spend_txid {
txid
} else {
return;
};

// If the channel is force closed, try to claim the output from this preimage.
// First check if a counterparty commitment transaction has been broadcasted:
macro_rules! claim_htlcs {
Expand All @@ -2512,14 +2524,24 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
}
}
if let Some(txid) = self.current_counterparty_commitment_txid {
if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
claim_htlcs!(*commitment_number, txid);
if txid == confirmed_spend_txid {
if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
claim_htlcs!(*commitment_number, txid);
} else {
debug_assert!(false);
log_error!(logger, "Detected counterparty commitment tx on-chain without tracking commitment number");
}
return;
}
}
if let Some(txid) = self.prev_counterparty_commitment_txid {
if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
claim_htlcs!(*commitment_number, txid);
if txid == confirmed_spend_txid {
if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
claim_htlcs!(*commitment_number, txid);
} else {
debug_assert!(false);
log_error!(logger, "Detected counterparty commitment tx on-chain without tracking commitment number");
}
return;
}
}
Expand All @@ -2530,13 +2552,22 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
// *we* sign a holder commitment transaction, not when e.g. a watchtower broadcasts one of our
// holder commitment transactions.
if self.broadcasted_holder_revokable_script.is_some() {
// Assume that the broadcasted commitment transaction confirmed in the current best
// block. Even if not, its a reasonable metric for the bump criteria on the HTLC
// transactions.
let (claim_reqs, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
self.onchain_tx_handler.update_claims_view_from_requests(claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
if let Some(ref tx) = self.prev_holder_signed_commitment_tx {
let (claim_reqs, _) = self.get_broadcasted_holder_claims(&tx, self.best_block.height());
let holder_commitment_tx = if self.current_holder_commitment_tx.txid == confirmed_spend_txid {
Some(&self.current_holder_commitment_tx)
} else if let Some(prev_holder_commitment_tx) = &self.prev_holder_signed_commitment_tx {
if prev_holder_commitment_tx.txid == confirmed_spend_txid {
Some(prev_holder_commitment_tx)
} else {
None
}
} else {
None
};
if let Some(holder_commitment_tx) = holder_commitment_tx {
// Assume that the broadcasted commitment transaction confirmed in the current best
// block. Even if not, its a reasonable metric for the bump criteria on the HTLC
// transactions.
let (claim_reqs, _) = self.get_broadcasted_holder_claims(&holder_commitment_tx, self.best_block.height());
self.onchain_tx_handler.update_claims_view_from_requests(claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
}
}
Expand Down
139 changes: 138 additions & 1 deletion lightning/src/ln/reorg_tests.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,11 @@

//! Further functional tests which test blockchain reorganizations.

use crate::chain::chaininterface::LowerBoundedFeeEstimator;
use crate::chain::channelmonitor::{ANTI_REORG_DELAY, LATENCY_GRACE_PERIOD_BLOCKS};
use crate::chain::transaction::OutPoint;
use crate::chain::Confirm;
use crate::events::{Event, MessageSendEventsProvider, ClosureReason, HTLCDestination};
use crate::events::{Event, MessageSendEventsProvider, ClosureReason, HTLCDestination, MessageSendEvent};
use crate::ln::msgs::{ChannelMessageHandler, Init};
use crate::util::test_utils;
use crate::util::ser::Writeable;
Expand Down Expand Up @@ -617,3 +618,139 @@ fn test_to_remote_after_local_detection() {
do_test_to_remote_after_local_detection(ConnectStyle::TransactionsFirstReorgsOnlyTip);
do_test_to_remote_after_local_detection(ConnectStyle::FullBlockViaListen);
}

#[test]
fn test_htlc_preimage_claim_holder_commitment_after_counterparty_commitment_reorg() {
// We detect a counterparty commitment confirm onchain, followed by a reorg and a confirmation
// of a holder commitment. Then, if we learn of the preimage for an HTLC in both commitments,
// test that we only claim the currently confirmed commitment.
let chanmon_cfgs = create_chanmon_cfgs(2);
let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None, None]);
let nodes = create_network(2, &node_cfgs, &node_chanmgrs);

let (_, _, chan_id, funding_tx) = create_announced_chan_between_nodes(&nodes, 0, 1);

// Route an HTLC which we will claim onchain with the preimage.
let (payment_preimage, payment_hash, ..) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);

// Force close with the latest counterparty commitment, confirm it, and reorg it with the latest
// holder commitment.
nodes[0].node.force_close_broadcasting_latest_txn(&chan_id, &nodes[1].node.get_our_node_id()).unwrap();
check_closed_broadcast(&nodes[0], 1, true);
check_added_monitors(&nodes[0], 1);
check_closed_event(&nodes[0], 1, ClosureReason::HolderForceClosed, false, &[nodes[1].node.get_our_node_id()], 100000);

nodes[1].node.force_close_broadcasting_latest_txn(&chan_id, &nodes[0].node.get_our_node_id()).unwrap();
check_closed_broadcast(&nodes[1], 1, true);
check_added_monitors(&nodes[1], 1);
check_closed_event(&nodes[1], 1, ClosureReason::HolderForceClosed, false, &[nodes[0].node.get_our_node_id()], 100000);

let mut txn = nodes[0].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
let commitment_tx_a = txn.pop().unwrap();
check_spends!(commitment_tx_a, funding_tx);

let mut txn = nodes[1].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
let commitment_tx_b = txn.pop().unwrap();
check_spends!(commitment_tx_b, funding_tx);

mine_transaction(&nodes[0], &commitment_tx_a);
mine_transaction(&nodes[1], &commitment_tx_a);

disconnect_blocks(&nodes[0], 1);
disconnect_blocks(&nodes[1], 1);

mine_transaction(&nodes[0], &commitment_tx_b);
mine_transaction(&nodes[1], &commitment_tx_b);

// Provide the preimage now, such that we only claim from the holder commitment (since it's
// currently confirmed) and not the counterparty's.
get_monitor!(nodes[1], chan_id).provide_payment_preimage(
&payment_hash, &payment_preimage, &nodes[1].tx_broadcaster,
&LowerBoundedFeeEstimator(nodes[1].fee_estimator), &nodes[1].logger
);

let mut txn = nodes[1].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
let htlc_success_tx = txn.pop().unwrap();
check_spends!(htlc_success_tx, commitment_tx_b);
}

#[test]
fn test_htlc_preimage_claim_prev_counterparty_commitment_after_current_counterparty_commitment_reorg() {
// We detect a counterparty commitment confirm onchain, followed by a reorg and a
// confirmation of the previous (still unrevoked) counterparty commitment. Then, if we learn
// of the preimage for an HTLC in both commitments, test that we only claim the currently
// confirmed commitment.
let chanmon_cfgs = create_chanmon_cfgs(2);
let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None, None]);
let nodes = create_network(2, &node_cfgs, &node_chanmgrs);

let (_, _, chan_id, funding_tx) = create_announced_chan_between_nodes(&nodes, 0, 1);

// Route an HTLC which we will claim onchain with the preimage.
let (payment_preimage, payment_hash, ..) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);

// Obtain the current commitment, which will become the previous after a fee update.
let prev_commitment_a = &get_local_commitment_txn!(nodes[0], chan_id)[0];

*nodes[0].fee_estimator.sat_per_kw.lock().unwrap() *= 4;
nodes[0].node.timer_tick_occurred();
check_added_monitors(&nodes[0], 1);
let mut msg_events = nodes[0].node.get_and_clear_pending_msg_events();
assert_eq!(msg_events.len(), 1);
let (update_fee, commit_sig) = if let MessageSendEvent::UpdateHTLCs { node_id, mut updates } = msg_events.pop().unwrap() {
assert_eq!(node_id, nodes[1].node.get_our_node_id());
(updates.update_fee.take().unwrap(), updates.commitment_signed)
} else {
panic!("Unexpected message send event");
};

// Handle the fee update on the other side, but don't send the last RAA such that the previous
// commitment is still valid (unrevoked).
nodes[1].node().handle_update_fee(&nodes[0].node.get_our_node_id(), &update_fee);
let _last_revoke_and_ack = commitment_signed_dance!(nodes[1], nodes[0], commit_sig, false, true, false, true);

// Force close with the latest commitment, confirm it, and reorg it with the previous commitment.
nodes[0].node.force_close_broadcasting_latest_txn(&chan_id, &nodes[1].node.get_our_node_id()).unwrap();
check_closed_broadcast(&nodes[0], 1, true);
check_added_monitors(&nodes[0], 1);
check_closed_event(&nodes[0], 1, ClosureReason::HolderForceClosed, false, &[nodes[1].node.get_our_node_id()], 100000);

let mut txn = nodes[0].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
let current_commitment_a = txn.pop().unwrap();
assert_ne!(current_commitment_a.txid(), prev_commitment_a.txid());
check_spends!(current_commitment_a, funding_tx);

mine_transaction(&nodes[0], &current_commitment_a);
mine_transaction(&nodes[1], &current_commitment_a);

check_closed_broadcast(&nodes[1], 1, true);
check_added_monitors(&nodes[1], 1);
check_closed_event(&nodes[1], 1, ClosureReason::CommitmentTxConfirmed, false, &[nodes[0].node.get_our_node_id()], 100000);

disconnect_blocks(&nodes[0], 1);
disconnect_blocks(&nodes[1], 1);

mine_transaction(&nodes[0], &prev_commitment_a);
mine_transaction(&nodes[1], &prev_commitment_a);

// Provide the preimage now, such that we only claim from the previous commitment (since it's
// currently confirmed) and not the latest.
get_monitor!(nodes[1], chan_id).provide_payment_preimage(
&payment_hash, &payment_preimage, &nodes[1].tx_broadcaster,
&LowerBoundedFeeEstimator(nodes[1].fee_estimator), &nodes[1].logger
);

let mut txn = nodes[1].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
let htlc_preimage_tx = txn.pop().unwrap();
check_spends!(htlc_preimage_tx, prev_commitment_a);
// Make sure it was indeed a preimage claim and not a revocation claim since the previous
// commitment (still unrevoked) is the currently confirmed closing transaction.
assert_eq!(htlc_preimage_tx.input[0].witness.second_to_last().unwrap(), &payment_preimage.0[..]);
}

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