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merged 2 commits into from
Oct 10, 2025
Merged

Only claim HTLCs with matching payment hash upon preimage monitor update #4154

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2fbaf96
Rustfmt get_counterparty_output_claim_info
wpaulino Oct 7, 2025
46f0d31
Only claim HTLCs with matching payment hash upon preimage monitor update
wpaulino Oct 7, 2025
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171 changes: 120 additions & 51 deletions lightning/src/chain/channelmonitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3823,7 +3823,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
// First check if a counterparty commitment transaction has been broadcasted:
macro_rules! claim_htlcs {
($commitment_number: expr, $txid: expr, $htlcs: expr) => {
let (htlc_claim_reqs, _) = self.get_counterparty_output_claim_info(funding_spent, $commitment_number, $txid, None, $htlcs, confirmed_spend_height);
let htlc_claim_reqs = self.get_counterparty_output_claims_for_preimage(*payment_preimage, funding_spent, $commitment_number, $txid, $htlcs, confirmed_spend_height);
let conf_target = self.closure_conf_target();
self.onchain_tx_handler.update_claims_view_from_requests(
htlc_claim_reqs, self.best_block.height, self.best_block.height, broadcaster,
Expand Down Expand Up @@ -4722,7 +4722,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
(htlc, htlc_source.as_ref().map(|htlc_source| htlc_source.as_ref()))
), logger);
let (htlc_claim_reqs, counterparty_output_info) =
self.get_counterparty_output_claim_info(funding_spent, commitment_number, commitment_txid, Some(commitment_tx), per_commitment_option, Some(height));
self.get_counterparty_output_claim_info(funding_spent, commitment_number, commitment_txid, commitment_tx, per_commitment_claimable_data, Some(height));
to_counterparty_output_info = counterparty_output_info;
for req in htlc_claim_reqs {
claimable_outpoints.push(req);
Expand All @@ -4732,87 +4732,156 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitorImpl<Signer> {
(claimable_outpoints, to_counterparty_output_info)
}

fn get_point_for_commitment_number(&self, commitment_number: u64) -> Option<PublicKey> {
let per_commitment_points = &self.their_cur_per_commitment_points?;

// If the counterparty commitment tx is the latest valid state, use their latest
// per-commitment point
if per_commitment_points.0 == commitment_number {
Some(per_commitment_points.1)
} else if let Some(point) = per_commitment_points.2.as_ref() {
// If counterparty commitment tx is the state previous to the latest valid state, use
// their previous per-commitment point (non-atomicity of revocation means it's valid for
// them to temporarily have two valid commitment txns from our viewpoint)
if per_commitment_points.0 == commitment_number + 1 {
Some(*point)
} else {
None
}
} else {
None
}
}

fn get_counterparty_output_claims_for_preimage(
&self, preimage: PaymentPreimage, funding_spent: &FundingScope, commitment_number: u64,
commitment_txid: Txid,
per_commitment_option: Option<&Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>>,
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Wondering if we can be more aggressive and remove the Option here - we have this data at all places where this is called. If not, we lose funds, and we should panic ? Also applies to get_point_for_commitment_number.

confirmation_height: Option<u32>,
) -> Vec<PackageTemplate> {
let per_commitment_claimable_data = match per_commitment_option {
Some(outputs) => outputs,
None => return Vec::new(),
};
let per_commitment_point = match self.get_point_for_commitment_number(commitment_number) {
Some(point) => point,
None => return Vec::new(),
};

let matching_payment_hash = PaymentHash::from(preimage);
per_commitment_claimable_data
.iter()
.filter_map(|(htlc, _)| {
if let Some(transaction_output_index) = htlc.transaction_output_index {
if htlc.offered && htlc.payment_hash == matching_payment_hash {
let htlc_data = PackageSolvingData::CounterpartyOfferedHTLCOutput(
CounterpartyOfferedHTLCOutput::build(
per_commitment_point,
preimage,
htlc.clone(),
funding_spent.channel_parameters.clone(),
confirmation_height,
),
);
Some(PackageTemplate::build_package(
commitment_txid,
transaction_output_index,
htlc_data,
htlc.cltv_expiry,
))
} else {
None
}
} else {
None
}
})
.collect()
}

/// Returns the HTLC claim package templates and the counterparty output info
#[rustfmt::skip]
fn get_counterparty_output_claim_info(
&self, funding_spent: &FundingScope, commitment_number: u64, commitment_txid: Txid,
tx: Option<&Transaction>,
per_commitment_option: Option<&Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>>,
tx: &Transaction,
per_commitment_claimable_data: &[(HTLCOutputInCommitment, Option<Box<HTLCSource>>)],
confirmation_height: Option<u32>,
) -> (Vec<PackageTemplate>, CommitmentTxCounterpartyOutputInfo) {
let mut claimable_outpoints = Vec::new();
let mut to_counterparty_output_info: CommitmentTxCounterpartyOutputInfo = None;

let per_commitment_claimable_data = match per_commitment_option {
Some(outputs) => outputs,
None => return (claimable_outpoints, to_counterparty_output_info),
};
let per_commitment_points = match self.their_cur_per_commitment_points {
Some(points) => points,
let per_commitment_point = match self.get_point_for_commitment_number(commitment_number) {
Some(point) => point,
None => return (claimable_outpoints, to_counterparty_output_info),
};

let per_commitment_point =
// If the counterparty commitment tx is the latest valid state, use their latest
// per-commitment point
if per_commitment_points.0 == commitment_number { &per_commitment_points.1 }
else if let Some(point) = per_commitment_points.2.as_ref() {
// If counterparty commitment tx is the state previous to the latest valid state, use
// their previous per-commitment point (non-atomicity of revocation means it's valid for
// them to temporarily have two valid commitment txns from our viewpoint)
if per_commitment_points.0 == commitment_number + 1 {
point
} else { return (claimable_outpoints, to_counterparty_output_info); }
} else { return (claimable_outpoints, to_counterparty_output_info); };

if let Some(transaction) = tx {
let revocation_pubkey = RevocationKey::from_basepoint(
&self.onchain_tx_handler.secp_ctx, &self.holder_revocation_basepoint, &per_commitment_point);

let delayed_key = DelayedPaymentKey::from_basepoint(&self.onchain_tx_handler.secp_ctx, &self.counterparty_commitment_params.counterparty_delayed_payment_base_key, &per_commitment_point);

let revokeable_p2wsh = chan_utils::get_revokeable_redeemscript(&revocation_pubkey,
self.counterparty_commitment_params.on_counterparty_tx_csv,
&delayed_key).to_p2wsh();
for (idx, outp) in transaction.output.iter().enumerate() {
if outp.script_pubkey == revokeable_p2wsh {
to_counterparty_output_info =
Some((idx.try_into().expect("Can't have > 2^32 outputs"), outp.value));
}
let revocation_pubkey = RevocationKey::from_basepoint(
&self.onchain_tx_handler.secp_ctx,
&self.holder_revocation_basepoint,
&per_commitment_point,
);
let delayed_key = DelayedPaymentKey::from_basepoint(
&self.onchain_tx_handler.secp_ctx,
&self.counterparty_commitment_params.counterparty_delayed_payment_base_key,
&per_commitment_point,
);
let revokeable_p2wsh = chan_utils::get_revokeable_redeemscript(
&revocation_pubkey,
self.counterparty_commitment_params.on_counterparty_tx_csv,
&delayed_key,
)
.to_p2wsh();
for (idx, outp) in tx.output.iter().enumerate() {
if outp.script_pubkey == revokeable_p2wsh {
to_counterparty_output_info =
Some((idx.try_into().expect("Can't have > 2^32 outputs"), outp.value));
}
}

for &(ref htlc, _) in per_commitment_claimable_data.iter() {
for &(ref htlc, _) in per_commitment_claimable_data.iter() {
if let Some(transaction_output_index) = htlc.transaction_output_index {
if let Some(transaction) = tx {
if transaction_output_index as usize >= transaction.output.len() ||
transaction.output[transaction_output_index as usize].value != htlc.to_bitcoin_amount() {
// per_commitment_data is corrupt or our commitment signing key leaked!
return (claimable_outpoints, to_counterparty_output_info);
}
if transaction_output_index as usize >= tx.output.len()
|| tx.output[transaction_output_index as usize].value
!= htlc.to_bitcoin_amount()
{
// per_commitment_data is corrupt or our commitment signing key leaked!
return (claimable_outpoints, to_counterparty_output_info);
}
let preimage = if htlc.offered { if let Some((p, _)) = self.payment_preimages.get(&htlc.payment_hash) { Some(*p) } else { None } } else { None };
let preimage = if htlc.offered {
if let Some((p, _)) = self.payment_preimages.get(&htlc.payment_hash) {
Some(*p)
} else {
None
}
} else {
None
};
if preimage.is_some() || !htlc.offered {
let counterparty_htlc_outp = if htlc.offered {
PackageSolvingData::CounterpartyOfferedHTLCOutput(
CounterpartyOfferedHTLCOutput::build(
*per_commitment_point, preimage.unwrap(),
per_commitment_point,
preimage.unwrap(),
htlc.clone(),
funding_spent.channel_parameters.clone(),
confirmation_height,
)
),
)
} else {
PackageSolvingData::CounterpartyReceivedHTLCOutput(
CounterpartyReceivedHTLCOutput::build(
*per_commitment_point,
per_commitment_point,
htlc.clone(),
funding_spent.channel_parameters.clone(),
confirmation_height,
)
),
)
};
let counterparty_package = PackageTemplate::build_package(commitment_txid, transaction_output_index, counterparty_htlc_outp, htlc.cltv_expiry);
let counterparty_package = PackageTemplate::build_package(
commitment_txid,
transaction_output_index,
counterparty_htlc_outp,
htlc.cltv_expiry,
);
claimable_outpoints.push(counterparty_package);
}
}
Expand Down
82 changes: 82 additions & 0 deletions lightning/src/ln/monitor_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3836,3 +3836,85 @@ fn test_lost_timeout_monitor_events() {
do_test_lost_timeout_monitor_events(CommitmentType::LocalWithLastHTLC, false, true);
do_test_lost_timeout_monitor_events(CommitmentType::LocalWithLastHTLC, true, true);
}

#[test]
fn test_ladder_preimage_htlc_claims() {
// Tests that when we learn of a preimage via a monitor update we only claim HTLCs with the
// corresponding payment hash. This test is a reproduction of a scenario that happened in
// production where the second HTLC claim also included the first HTLC (even though it was
// already claimed) resulting in an invalid claim transaction.
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]);
let mut nodes = create_network(2, &node_cfgs, &node_chanmgrs);

let node_id_0 = nodes[0].node.get_our_node_id();
let node_id_1 = nodes[1].node.get_our_node_id();

let (_, _, channel_id, _) = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1_000_000, 0);

let (payment_preimage1, payment_hash1, _, _) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);
let (payment_preimage2, payment_hash2, _, _) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);

nodes[0].node.force_close_broadcasting_latest_txn(&channel_id, &node_id_1, "test".to_string()).unwrap();
check_added_monitors(&nodes[0], 1);
check_closed_broadcast(&nodes[0], 1, true);
let reason = ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(true), message: "test".to_string() };
check_closed_event(&nodes[0], 1, reason, false, &[node_id_1], 1_000_000);

let commitment_tx = {
let mut txn = nodes[0].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
txn.remove(0)
};
mine_transaction(&nodes[0], &commitment_tx);
mine_transaction(&nodes[1], &commitment_tx);

check_closed_broadcast(&nodes[1], 1, true);
check_added_monitors(&nodes[1], 1);
check_closed_event(&nodes[1], 1, ClosureReason::CommitmentTxConfirmed, false, &[node_id_0], 1_000_000);

nodes[1].node.claim_funds(payment_preimage1);
expect_payment_claimed!(&nodes[1], payment_hash1, 1_000_000);
check_added_monitors(&nodes[1], 1);

let (htlc1, htlc_claim_tx1) = {
let mut txn = nodes[1].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1);
let htlc_claim_tx = txn.remove(0);
assert_eq!(htlc_claim_tx.input.len(), 1);
check_spends!(htlc_claim_tx, commitment_tx);
(htlc_claim_tx.input[0].previous_output, htlc_claim_tx)
};
mine_transaction(&nodes[0], &htlc_claim_tx1);
mine_transaction(&nodes[1], &htlc_claim_tx1);

connect_blocks(&nodes[0], ANTI_REORG_DELAY - 1);
connect_blocks(&nodes[1], ANTI_REORG_DELAY - 1);

expect_payment_sent(&nodes[0], payment_preimage1, None, true, false);
check_added_monitors(&nodes[0], 1);

nodes[1].node.claim_funds(payment_preimage2);
expect_payment_claimed!(&nodes[1], payment_hash2, 1_000_000);
check_added_monitors(&nodes[1], 1);

let (htlc2, htlc_claim_tx2) = {
let mut txn = nodes[1].tx_broadcaster.txn_broadcast();
assert_eq!(txn.len(), 1, "{:?}", txn.iter().map(|tx| tx.compute_txid()).collect::<Vec<_>>());
let htlc_claim_tx = txn.remove(0);
assert_eq!(htlc_claim_tx.input.len(), 1);
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Add coverage for the case where at this point we should claim multiple outputs on the commit tx ? I'm thinking of the MPP case. The actual code does this correctly.

check_spends!(htlc_claim_tx, commitment_tx);
(htlc_claim_tx.input[0].previous_output, htlc_claim_tx)
};
assert_ne!(htlc1, htlc2);

mine_transaction(&nodes[0], &htlc_claim_tx2);
mine_transaction(&nodes[1], &htlc_claim_tx2);

connect_blocks(&nodes[0], ANTI_REORG_DELAY - 1);
connect_blocks(&nodes[1], ANTI_REORG_DELAY - 1);

expect_payment_sent(&nodes[0], payment_preimage2, None, true, false);
check_added_monitors(&nodes[0], 1);
}