Make ChannelSigner solely responsible for validating commitment sigs#3878

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tankyleo wants to merge 2 commits into from
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Make ChannelSigner solely responsible for validating commitment sigs #3878

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b3773a7
Make `ChannelSigner` solely responsible for validating commitment sigs
tankyleo Jun 21, 2025
4005d59
Remove format skips in channel holder commitment validation functions
tankyleo Jun 21, 2025
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295 changes: 165 additions & 130 deletions lightning/src/ln/channel.rs
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Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

fn received_msg(&self) -> &'static str;

#[rustfmt::skip]
fn check_counterparty_commitment_signature<L: Deref>(
&self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
let funding_script = self.funding().get_funding_redeemscript();

let commitment_data = self.context().build_commitment_transaction(self.funding(),
holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
true, false, logger);
let initial_commitment_tx = commitment_data.tx;
let trusted_tx = initial_commitment_tx.trust();
let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
// They sign the holder commitment transaction...
log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
encode::serialize_hex(&funding_script), &self.context().channel_id());
secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

Ok(initial_commitment_tx)
}

#[rustfmt::skip]
fn initial_commitment_signed<L: Deref>(
&mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
best_block: BestBlock, signer_provider: &SP, logger: &L,
) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
&mut self, channel_id: ChannelId, counterparty_signature: Signature,
holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
signer_provider: &SP, logger: &L,
) -> Result<
(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
ChannelError,
>
where
L::Target: Logger
L::Target: Logger,
{
let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
Ok(res) => res,
Err(ChannelError::Close(e)) => {
// TODO(dual_funding): Update for V2 established channels.
if !self.funding().is_outbound() {
self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
}
return Err(ChannelError::Close(e));
},
Err(e) => {
// The only error we know how to handle is ChannelError::Close, so we fall over here
// to make sure we don't continue with an inconsistent state.
panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
}
};
let context = self.context();
let commitment_data = context.build_commitment_transaction(self.funding(),
context.cur_counterparty_commitment_transaction_number,
&context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
let counterparty_initial_commitment_tx = commitment_data.tx;
let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
&context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

let initial_commitment_tx = context
.build_commitment_transaction(
self.funding(),
holder_commitment_point.transaction_number(),
&holder_commitment_point.current_point(),
true,
false,
logger,
)
.tx;
let holder_commitment_tx = HolderCommitmentTransaction::new(
initial_commitment_tx,
counterparty_signature,
Vec::new(),
&self.funding().get_holder_pubkeys().funding_pubkey,
&self.funding().counterparty_funding_pubkey()
&self.funding().counterparty_funding_pubkey(),
);

if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
log_trace!(
logger,
"Validating {} commitment in channel {}",
self.received_msg(),
context.channel_id()
);
if context
.holder_signer
.as_ref()
.validate_holder_commitment(
&self.funding().channel_transaction_parameters,
&holder_commitment_tx,
Vec::new(),
&context.secp_ctx,
)
.is_err()
{
if !self.funding().is_outbound() {
self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
}
return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
}

let commitment_data = context.build_commitment_transaction(
self.funding(),
context.cur_counterparty_commitment_transaction_number,
&context.counterparty_cur_commitment_point.unwrap(),
false,
false,
logger,
);
let counterparty_initial_commitment_tx = commitment_data.tx;
let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

log_trace!(
logger,
"Initial counterparty tx for channel {} is: txid {} tx {}",
&context.channel_id(),
counterparty_initial_bitcoin_tx.txid,
encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
);

// Now that we're past error-generating stuff, update our local state:

let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
if !is_v2_established {
if context.is_batch_funding() {
context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
context.channel_state = ChannelState::AwaitingChannelReady(
AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
);
} else {
context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
context.channel_state =
ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
}
}
if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
if holder_commitment_point
.advance(&context.holder_signer, &context.secp_ctx, logger)
.is_err()
{
// We only fail to advance our commitment point/number if we're currently
// waiting for our signer to unblock and provide a commitment point.
// We cannot send accept_channel/open_channel before this has occurred, so if we
// err here by the time we receive funding_created/funding_signed, something has gone wrong.
debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
debug_assert!(
false,
"We should be ready to advance our commitment point by the time we receive {}",
self.received_msg()
);
return Err(ChannelError::close(
"Failed to advance holder commitment point".to_owned(),
));
}

let context = self.context();
let funding = self.funding();
let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
let obscure_factor = get_commitment_transaction_number_obscure_factor(
&funding.get_holder_pubkeys().payment_point,
&funding.get_counterparty_pubkeys().payment_point,
funding.is_outbound(),
);
let shutdown_script =
context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
// TODO(RBF): When implementing RBF, the funding_txo passed here must only update
// ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
let channel_monitor = ChannelMonitor::new(
context.secp_ctx.clone(), monitor_signer, shutdown_script,
funding.get_holder_selected_contest_delay(), &context.destination_script,
&funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
context.secp_ctx.clone(),
monitor_signer,
shutdown_script,
funding.get_holder_selected_contest_delay(),
&context.destination_script,
&funding.channel_transaction_parameters,
funding.is_outbound(),
obscure_factor,
holder_commitment_tx,
best_block,
context.counterparty_node_id,
context.channel_id(),
);
channel_monitor.provide_initial_counterparty_commitment_tx(
counterparty_initial_commitment_tx.clone(), logger,
counterparty_initial_commitment_tx.clone(),
logger,
);

self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
Ok(())
}

#[rustfmt::skip]
fn validate_commitment_signed<L: Deref>(
&self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
msg: &msgs::CommitmentSigned, logger: &L,
) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
where
L::Target: Logger,
{
let funding_script = funding.get_funding_redeemscript();
let commitment_data = self.build_commitment_transaction(
funding,
holder_commitment_point.transaction_number(),
&holder_commitment_point.current_point(),
true,
false,
logger,
);

let commitment_data = self.build_commitment_transaction(funding,
holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
true, false, logger);
let commitment_txid = {
let trusted_tx = commitment_data.tx.trust();
let bitcoin_tx = trusted_tx.built_transaction();
let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
log_bytes!(msg.signature.serialize_compact()[..]),
log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
}
bitcoin_tx.txid
};
if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
return Err(ChannelError::close(format!(
"Got wrong number of HTLC signatures ({}) from remote. It must be {}",
msg.htlc_signatures.len(),
commitment_data.tx.nondust_htlcs().len()
)));
}

let holder_commitment_tx = HolderCommitmentTransaction::new(
commitment_data.tx,
msg.signature,
msg.htlc_signatures.clone(),
&funding.get_holder_pubkeys().funding_pubkey,
funding.counterparty_funding_pubkey(),
);

log_trace!(
logger,
"Validating commitment_signed commitment in channel {}",
self.channel_id()
);
self.holder_signer
.as_ref()
.validate_holder_commitment(
&funding.channel_transaction_parameters,
&holder_commitment_tx,
commitment_data.outbound_htlc_preimages,
&self.secp_ctx,
)
.map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

// If our counterparty updated the channel fee in this commitment transaction, check that
// they can actually afford the new fee now.
let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
update_state == FeeUpdateState::RemoteAnnounced
} else { false };
} else {
false
};
if update_fee {
debug_assert!(!funding.is_outbound());
let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
let counterparty_reserve_we_require_msat =
funding.holder_selected_channel_reserve_satoshis * 1000;
if commitment_data.stats.remote_balance_before_fee_anchors_msat
< commitment_data.stats.total_fee_sat * 1000
+ commitment_data.stats.total_anchors_sat * 1000
+ counterparty_reserve_we_require_msat
{
return Err(ChannelError::close(
"Funding remote cannot afford proposed new fee".to_owned(),
));
}
}
#[cfg(any(test, fuzzing))]
{
if funding.is_outbound() {
let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
let projected_commit_tx_info =
funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
*funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
if let Some(info) = projected_commit_tx_info {
let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
let total_pending_htlcs = self.pending_inbound_htlcs.len()
+ self.pending_outbound_htlcs.len()
+ self.holding_cell_htlc_updates.len();
if info.total_pending_htlcs == total_pending_htlcs
&& info.next_holder_htlc_id == self.next_holder_htlc_id
&& info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
&& info.feerate == self.feerate_per_kw {
assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
}
&& info.feerate == self.feerate_per_kw
{
assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
}
}
}
}

if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
}

let holder_keys = commitment_data.tx.trust().keys();
let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
let mut nondust_htlc_sources =
Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
let mut dust_htlcs = Vec::with_capacity(
commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
);
for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
if let Some(_) = htlc.transaction_output_index {
let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
&holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
}
if htlc.offered {
if let Some(source) = source_opt.take() {
nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
}

let holder_commitment_tx = HolderCommitmentTransaction::new(
commitment_data.tx,
msg.signature,
msg.htlc_signatures.clone(),
&funding.get_holder_pubkeys().funding_pubkey,
funding.counterparty_funding_pubkey()
);

self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
.map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

Ok(LatestHolderCommitmentTXInfo {
commitment_tx: holder_commitment_tx,
htlc_outputs: dust_htlcs,
Expand Down
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Make ChannelSigner solely responsible for validating commitment sigs#3878

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tankyleo
wants to merge
2
commits into

from

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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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Make ChannelSigner solely responsible for validating commitment sigs#3878

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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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Make ChannelSigner solely responsible for validating commitment sigs#3878

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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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Make ChannelSigner solely responsible for validating commitment sigs#3878

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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Make ChannelSigner solely responsible for validating commitment sigs#3878

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tankyleo
wants to merge
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commits into

from

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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Make ChannelSigner solely responsible for validating commitment sigs#3878

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Make ChannelSigner solely responsible for validating commitment sigs
#3878
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b3773a7

Make `ChannelSigner` solely responsible for validating commitment sigs


tankyleo Jun 21, 2025
4005d59

Remove format skips in channel holder commitment validation functions


tankyleo Jun 21, 2025

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295 changes: 165 additions & 130 deletions
lightning/src/ln/channel.rs

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Original file line numberDiff line numberDiff line change
Expand Up@@ -21,10 +21,9 @@ use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::sha256d::Hash as Sha256d;
use bitcoin::hashes::Hash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{ecdsa::Signature, Secp256k1};
use bitcoin::secp256k1::{PublicKey, SecretKey};
use bitcoin::{secp256k1, sighash};
use bitcoin::secp256k1::{
	self, constants::PUBLIC_KEY_SIZE, ecdsa::Signature, PublicKey, Secp256k1, SecretKey,
};

use crate::chain::chaininterface::{
	fee_for_weight, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator,
Expand DownExpand Up@@ -2512,75 +2511,80 @@ where

	fn received_msg(&self) -> &'static str;

	#[rustfmt::skip]
	fn check_counterparty_commitment_signature<L: Deref>(
 &self, sig: &Signature, holder_commitment_point: &HolderCommitmentPoint, logger: &L
	) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
 let funding_script = self.funding().get_funding_redeemscript();

 let commitment_data = self.context().build_commitment_transaction(self.funding(),
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let initial_commitment_tx = commitment_data.tx;
 let trusted_tx = initial_commitment_tx.trust();
 let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
 let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
 // They sign the holder commitment transaction...
 log_trace!(logger, "Checking {} tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
 self.received_msg(), log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.funding().counterparty_funding_pubkey().serialize()),
 encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
 encode::serialize_hex(&funding_script), &self.context().channel_id());
 secp_check!(self.context().secp_ctx.verify_ecdsa(&sighash, sig, self.funding().counterparty_funding_pubkey()), format!("Invalid {} signature from peer", self.received_msg()));

 Ok(initial_commitment_tx)
	}

	#[rustfmt::skip]
	fn initial_commitment_signed<L: Deref>(
 &mut self, channel_id: ChannelId, counterparty_signature: Signature, holder_commitment_point: &mut HolderCommitmentPoint,
 best_block: BestBlock, signer_provider: &SP, logger: &L,
	) -> Result<(ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction), ChannelError>
 &mut self, channel_id: ChannelId, counterparty_signature: Signature,
 holder_commitment_point: &mut HolderCommitmentPoint, best_block: BestBlock,
 signer_provider: &SP, logger: &L,
	) -> Result<
 (ChannelMonitor<<SP::Target as SignerProvider>::EcdsaSigner>, CommitmentTransaction),
 ChannelError,
	>
	where
 L::Target: Logger
 L::Target: Logger,
	{
 let initial_commitment_tx = match self.check_counterparty_commitment_signature(&counterparty_signature, holder_commitment_point, logger) {
 Ok(res) => res,
 Err(ChannelError::Close(e)) => {
 // TODO(dual_funding): Update for V2 established channels.
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::Close(e));
 },
 Err(e) => {
 // The only error we know how to handle is ChannelError::Close, so we fall over here
 // to make sure we don't continue with an inconsistent state.
 panic!("unexpected error type from check_counterparty_commitment_signature {:?}", e);
 }
 };
 let context = self.context();
 let commitment_data = context.build_commitment_transaction(self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(), false, false, logger);
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));

 let initial_commitment_tx = context
 .build_commitment_transaction(
 self.funding(),
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 )
 .tx;
 let holder_commitment_tx = HolderCommitmentTransaction::new(
 initial_commitment_tx,
 counterparty_signature,
 Vec::new(),
 &self.funding().get_holder_pubkeys().funding_pubkey,
 &self.funding().counterparty_funding_pubkey()
 &self.funding().counterparty_funding_pubkey(),
 );

 if context.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, Vec::new()).is_err() {
 log_trace!(
 logger,
 "Validating {} commitment in channel {}",
 self.received_msg(),
 context.channel_id()
 );
 if context
 .holder_signer
 .as_ref()
 .validate_holder_commitment(
 &self.funding().channel_transaction_parameters,
 &holder_commitment_tx,
 Vec::new(),
 &context.secp_ctx,
 )
 .is_err()
 {
 if !self.funding().is_outbound() {
 self.funding_mut().channel_transaction_parameters.funding_outpoint = None;
 }
 return Err(ChannelError::close("Failed to validate our commitment".to_owned()));
 }

 let commitment_data = context.build_commitment_transaction(
 self.funding(),
 context.cur_counterparty_commitment_transaction_number,
 &context.counterparty_cur_commitment_point.unwrap(),
 false,
 false,
 logger,
 );
 let counterparty_initial_commitment_tx = commitment_data.tx;
 let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
 let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();

 log_trace!(
 logger,
 "Initial counterparty tx for channel {} is: txid {} tx {}",
 &context.channel_id(),
 counterparty_initial_bitcoin_tx.txid,
 encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction)
 );

 // Now that we're past error-generating stuff, update our local state:

 let is_v2_established = self.is_v2_established();
Expand All@@ -2590,35 +2594,61 @@ where
 assert!(!context.channel_state.is_monitor_update_in_progress()); // We have not had any monitor(s) yet to fail update!
 if !is_v2_established {
 if context.is_batch_funding() {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::WAITING_FOR_BATCH);
 context.channel_state = ChannelState::AwaitingChannelReady(
 AwaitingChannelReadyFlags::WAITING_FOR_BATCH,
 );
 } else {
 context.channel_state = ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 context.channel_state =
 ChannelState::AwaitingChannelReady(AwaitingChannelReadyFlags::new());
 }
 }
 if holder_commitment_point.advance(&context.holder_signer, &context.secp_ctx, logger).is_err() {
 if holder_commitment_point
 .advance(&context.holder_signer, &context.secp_ctx, logger)
 .is_err()
 {
 // We only fail to advance our commitment point/number if we're currently
 // waiting for our signer to unblock and provide a commitment point.
 // We cannot send accept_channel/open_channel before this has occurred, so if we
 // err here by the time we receive funding_created/funding_signed, something has gone wrong.
 debug_assert!(false, "We should be ready to advance our commitment point by the time we receive {}", self.received_msg());
 return Err(ChannelError::close("Failed to advance holder commitment point".to_owned()));
 debug_assert!(
 false,
 "We should be ready to advance our commitment point by the time we receive {}",
 self.received_msg()
 );
 return Err(ChannelError::close(
 "Failed to advance holder commitment point".to_owned(),
 ));
 }

 let context = self.context();
 let funding = self.funding();
 let obscure_factor = get_commitment_transaction_number_obscure_factor(&funding.get_holder_pubkeys().payment_point, &funding.get_counterparty_pubkeys().payment_point, funding.is_outbound());
 let shutdown_script = context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let obscure_factor = get_commitment_transaction_number_obscure_factor(
 &funding.get_holder_pubkeys().payment_point,
 &funding.get_counterparty_pubkeys().payment_point,
 funding.is_outbound(),
 );
 let shutdown_script =
 context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
 let monitor_signer = signer_provider.derive_channel_signer(context.channel_keys_id);
 // TODO(RBF): When implementing RBF, the funding_txo passed here must only update
 // ChannelMonitorImp::first_confirmed_funding_txo during channel establishment, not splicing
 let channel_monitor = ChannelMonitor::new(
 context.secp_ctx.clone(), monitor_signer, shutdown_script,
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
 context.secp_ctx.clone(),
 monitor_signer,
 shutdown_script,
 funding.get_holder_selected_contest_delay(),
 &context.destination_script,
 &funding.channel_transaction_parameters,
 funding.is_outbound(),
 obscure_factor,
 holder_commitment_tx,
 best_block,
 context.counterparty_node_id,
 context.channel_id(),
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(), logger,
 counterparty_initial_commitment_tx.clone(),
 logger,
 );

 self.context_mut().cur_counterparty_commitment_transaction_number -= 1;
Expand DownExpand Up@@ -4199,86 +4229,102 @@ where
 Ok(())
	}

	#[rustfmt::skip]
	fn validate_commitment_signed<L: Deref>(
 &self, funding: &FundingScope, holder_commitment_point: &HolderCommitmentPoint,
 msg: &msgs::CommitmentSigned, logger: &L,
	) -> Result<LatestHolderCommitmentTXInfo, ChannelError>
	where
 L::Target: Logger,
	{
 let funding_script = funding.get_funding_redeemscript();
 let commitment_data = self.build_commitment_transaction(
 funding,
 holder_commitment_point.transaction_number(),
 &holder_commitment_point.current_point(),
 true,
 false,
 logger,
 );

 let commitment_data = self.build_commitment_transaction(funding,
 holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(),
 true, false, logger);
 let commitment_txid = {
 let trusted_tx = commitment_data.tx.trust();
 let bitcoin_tx = trusted_tx.built_transaction();
 let sighash = bitcoin_tx.get_sighash_all(&funding_script, funding.get_value_satoshis());

 log_trace!(logger, "Checking commitment tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}",
 log_bytes!(msg.signature.serialize_compact()[..]),
 log_bytes!(funding.counterparty_funding_pubkey().serialize()), encode::serialize_hex(&bitcoin_tx.transaction),
 log_bytes!(sighash[..]), encode::serialize_hex(&funding_script), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &funding.counterparty_funding_pubkey()) {
 return Err(ChannelError::close("Invalid commitment tx signature from peer".to_owned()));
 }
 bitcoin_tx.txid
 };
 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!(
 "Got wrong number of HTLC signatures ({}) from remote. It must be {}",
 msg.htlc_signatures.len(),
 commitment_data.tx.nondust_htlcs().len()
 )));
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey(),
 );

 log_trace!(
 logger,
 "Validating commitment_signed commitment in channel {}",
 self.channel_id()
 );
 self.holder_signer
 .as_ref()
 .validate_holder_commitment(
 &funding.channel_transaction_parameters,
 &holder_commitment_tx,
 commitment_data.outbound_htlc_preimages,
 &self.secp_ctx,
 )
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 // If our counterparty updated the channel fee in this commitment transaction, check that
 // they can actually afford the new fee now.
 let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
 update_state == FeeUpdateState::RemoteAnnounced
 } else { false };
 } else {
 false
 };
 if update_fee {
 debug_assert!(!funding.is_outbound());
 let counterparty_reserve_we_require_msat = funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat < commitment_data.stats.total_fee_sat * 1000 + commitment_data.stats.total_anchors_sat * 1000 + counterparty_reserve_we_require_msat {
 return Err(ChannelError::close("Funding remote cannot afford proposed new fee".to_owned()));
 let counterparty_reserve_we_require_msat =
 funding.holder_selected_channel_reserve_satoshis * 1000;
 if commitment_data.stats.remote_balance_before_fee_anchors_msat
 < commitment_data.stats.total_fee_sat * 1000
 + commitment_data.stats.total_anchors_sat * 1000
 + counterparty_reserve_we_require_msat
 {
 return Err(ChannelError::close(
 "Funding remote cannot afford proposed new fee".to_owned(),
 ));
 }
 }
 #[cfg(any(test, fuzzing))]
 {
 if funding.is_outbound() {
 let projected_commit_tx_info = funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 let projected_commit_tx_info =
 funding.next_local_commitment_tx_fee_info_cached.lock().unwrap().take();
 *funding.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
 if let Some(info) = projected_commit_tx_info {
 let total_pending_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len()
 let total_pending_htlcs = self.pending_inbound_htlcs.len()
 + self.pending_outbound_htlcs.len()
 + self.holding_cell_htlc_updates.len();
 if info.total_pending_htlcs == total_pending_htlcs
 && info.next_holder_htlc_id == self.next_holder_htlc_id
 && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
 && info.feerate == self.feerate_per_kw {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 && info.feerate == self.feerate_per_kw
 {
 assert_eq!(commitment_data.stats.total_fee_sat, info.fee / 1000);
 }
 }
 }
 }

 if msg.htlc_signatures.len() != commitment_data.tx.nondust_htlcs().len() {
 return Err(ChannelError::close(format!("Got wrong number of HTLC signatures ({}) from remote. It must be {}", msg.htlc_signatures.len(), commitment_data.tx.nondust_htlcs().len())));
 }

 let holder_keys = commitment_data.tx.trust().keys();
 let mut nondust_htlc_sources = Vec::with_capacity(commitment_data.tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(commitment_data.htlcs_included.len() - commitment_data.tx.nondust_htlcs().len());
 for (idx, (htlc, mut source_opt)) in commitment_data.htlcs_included.into_iter().enumerate() {
 let mut nondust_htlc_sources =
 Vec::with_capacity(holder_commitment_tx.nondust_htlcs().len());
 let mut dust_htlcs = Vec::with_capacity(
 commitment_data.htlcs_included.len() - holder_commitment_tx.nondust_htlcs().len(),
 );
 for (htlc, mut source_opt) in commitment_data.htlcs_included.into_iter() {
 if let Some(_) = htlc.transaction_output_index {
 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_data.tx.feerate_per_kw(),
 funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, funding.get_channel_type(),
 &holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);

 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, funding.get_channel_type(), &holder_keys);
 let htlc_sighashtype = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
 let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
 log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
 log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
 encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
 if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
 return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
 }
 if htlc.offered {
 if let Some(source) = source_opt.take() {
 nondust_htlc_sources.push(source.clone());
Expand All@@ -4292,17 +4338,6 @@ where
 debug_assert!(source_opt.is_none(), "HTLCSource should have been put somewhere");
 }

 let holder_commitment_tx = HolderCommitmentTransaction::new(
 commitment_data.tx,
 msg.signature,
 msg.htlc_signatures.clone(),
 &funding.get_holder_pubkeys().funding_pubkey,
 funding.counterparty_funding_pubkey()
 );

 self.holder_signer.as_ref().validate_holder_commitment(&holder_commitment_tx, commitment_data.outbound_htlc_preimages)
 .map_err(|_| ChannelError::close("Failed to validate our commitment".to_owned()))?;

 Ok(LatestHolderCommitmentTXInfo {
 commitment_tx: holder_commitment_tx,
 htlc_outputs: dust_htlcs,
Expand Down
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