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tankyleotankyleo
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Remove explicit per-commitment key derivations from channel objects
Channel objects should not impose a particular per-commitment derivation scheme on the builders of commitment transactions. This will make it easier to enable custom derivations in the future. Instead of building `TxCreationKeys` explicitly, the function `TrustedCommitmentTransaction::keys` should be used when the keys of the commitment transaction are needed. We do that in this commit.
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‎lightning/src/ln/channel.rs

Lines changed: 21 additions & 59 deletions
Original file line numberDiff line numberDiff line change
@@ -40,7 +40,7 @@ use crate::ln::script::{self, ShutdownScript};
4040
use crate::ln::channel_state::{ChannelShutdownState, CounterpartyForwardingInfo, InboundHTLCDetails, InboundHTLCStateDetails, OutboundHTLCDetails, OutboundHTLCStateDetails};
4141
use crate::ln::channelmanager::{self, OpenChannelMessage, PendingHTLCStatus, HTLCSource, SentHTLCId, HTLCFailureMsg, PendingHTLCInfo, RAACommitmentOrder, PaymentClaimDetails, BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA, MAX_LOCAL_BREAKDOWN_TIMEOUT};
4242
use crate::ln::chan_utils::{
43-
CounterpartyCommitmentSecrets, TxCreationKeys, HTLCOutputInCommitment, htlc_success_tx_weight,
43+
CounterpartyCommitmentSecrets, HTLCOutputInCommitment, htlc_success_tx_weight,
4444
htlc_timeout_tx_weight, ChannelPublicKeys, CommitmentTransaction,
4545
HolderCommitmentTransaction, ChannelTransactionParameters,
4646
CounterpartyChannelTransactionParameters, max_htlcs,
@@ -2045,8 +2045,7 @@ trait InitialRemoteCommitmentReceiver<SP: Deref> where SP::Target: SignerProvide
20452045
) -> Result<CommitmentTransaction, ChannelError> where L::Target: Logger {
20462046
let funding_script = self.funding().get_funding_redeemscript();
20472047

2048-
let keys = self.context().build_holder_transaction_keys(&self.funding(), holder_commitment_point.current_point());
2049-
let initial_commitment_tx = self.context().build_commitment_transaction(self.funding(), holder_commitment_point.transaction_number(), &keys, true, false, logger).tx;
2048+
let initial_commitment_tx = self.context().build_commitment_transaction(self.funding(), holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(), true, false, logger).tx;
20502049
let trusted_tx = initial_commitment_tx.trust();
20512050
let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
20522051
let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.funding().get_value_satoshis());
@@ -2083,8 +2082,7 @@ trait InitialRemoteCommitmentReceiver<SP: Deref> where SP::Target: SignerProvide
20832082
}
20842083
};
20852084
let context = self.context();
2086-
let counterparty_keys = context.build_remote_transaction_keys(self.funding());
2087-
let counterparty_initial_commitment_tx = context.build_commitment_transaction(self.funding(), context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
2085+
let counterparty_initial_commitment_tx = context.build_commitment_transaction(self.funding(), context.cur_counterparty_commitment_transaction_number, &context.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
20882086
let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
20892087
let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
20902088

@@ -3483,9 +3481,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
34833481
{
34843482
let funding_script = funding.get_funding_redeemscript();
34853483

3486-
let keys = self.build_holder_transaction_keys(funding, holder_commitment_point.current_point());
3487-
3488-
let commitment_stats = self.build_commitment_transaction(funding, holder_commitment_point.transaction_number(), &keys, true, false, logger);
3484+
let commitment_stats = self.build_commitment_transaction(funding, holder_commitment_point.transaction_number(), &holder_commitment_point.current_point(), true, false, logger);
34893485
let commitment_txid = {
34903486
let trusted_tx = commitment_stats.tx.trust();
34913487
let bitcoin_tx = trusted_tx.built_transaction();
@@ -3553,19 +3549,20 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
35533549

35543550
let mut nondust_htlc_sources = Vec::with_capacity(htlcs_cloned.len());
35553551
let mut htlcs_and_sigs = Vec::with_capacity(htlcs_cloned.len());
3552+
let holder_keys = commitment_stats.tx.trust().keys();
35563553
for (idx, (htlc, mut source_opt)) in htlcs_cloned.drain(..).enumerate() {
35573554
if let Some(_) = htlc.transaction_output_index {
35583555
let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_stats.feerate_per_kw,
35593556
funding.get_counterparty_selected_contest_delay().unwrap(), &htlc, &self.channel_type,
3560-
&keys.broadcaster_delayed_payment_key, &keys.revocation_key);
3557+
&holder_keys.broadcaster_delayed_payment_key, &holder_keys.revocation_key);
35613558

3562-
let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &self.channel_type, &keys);
3559+
let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &self.channel_type, &holder_keys);
35633560
let htlc_sighashtype = if self.channel_type.supports_anchors_zero_fee_htlc_tx() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
35643561
let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).p2wsh_signature_hash(0, &htlc_redeemscript, htlc.to_bitcoin_amount(), htlc_sighashtype).unwrap()[..]);
35653562
log_trace!(logger, "Checking HTLC tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} in channel {}.",
3566-
log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(keys.countersignatory_htlc_key.to_public_key().serialize()),
3563+
log_bytes!(msg.htlc_signatures[idx].serialize_compact()[..]), log_bytes!(holder_keys.countersignatory_htlc_key.to_public_key().serialize()),
35673564
encode::serialize_hex(&htlc_tx), log_bytes!(htlc_sighash[..]), encode::serialize_hex(&htlc_redeemscript), &self.channel_id());
3568-
if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &keys.countersignatory_htlc_key.to_public_key()) {
3565+
if let Err(_) = self.secp_ctx.verify_ecdsa(&htlc_sighash, &msg.htlc_signatures[idx], &holder_keys.countersignatory_htlc_key.to_public_key()) {
35693566
return Err(ChannelError::close("Invalid HTLC tx signature from peer".to_owned()));
35703567
}
35713568
if !separate_nondust_htlc_sources {
@@ -3614,7 +3611,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
36143611
/// generated by the peer which proposed adding the HTLCs, and thus we need to understand both
36153612
/// which peer generated this transaction and "to whom" this transaction flows.
36163613
#[inline]
3617-
fn build_commitment_transaction<L: Deref>(&self, funding: &FundingScope, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool, logger: &L) -> CommitmentStats
3614+
fn build_commitment_transaction<L: Deref>(&self, funding: &FundingScope, commitment_number: u64, per_commitment_point: &PublicKey, local: bool, generated_by_local: bool, logger: &L) -> CommitmentStats
36183615
where L::Target: Logger
36193616
{
36203617
let mut included_dust_htlcs: Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)> = Vec::new();
@@ -3816,7 +3813,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
38163813
if local { funding.channel_transaction_parameters.as_holder_broadcastable() }
38173814
else { funding.channel_transaction_parameters.as_counterparty_broadcastable() };
38183815
let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(commitment_number,
3819-
&keys.per_commitment_point,
3816+
per_commitment_point,
38203817
value_to_a as u64,
38213818
value_to_b as u64,
38223819
feerate_per_kw,
@@ -3842,32 +3839,6 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
38423839
}
38433840
}
38443841

3845-
#[inline]
3846-
/// Creates a set of keys for build_commitment_transaction to generate a transaction which our
3847-
/// counterparty will sign (ie DO NOT send signatures over a transaction created by this to
3848-
/// our counterparty!)
3849-
/// The result is a transaction which we can revoke broadcastership of (ie a "local" transaction)
3850-
/// TODO Some magic rust shit to compile-time check this?
3851-
fn build_holder_transaction_keys(&self, funding: &FundingScope, per_commitment_point: PublicKey) -> TxCreationKeys {
3852-
let delayed_payment_base = &funding.get_holder_pubkeys().delayed_payment_basepoint;
3853-
let htlc_basepoint = &funding.get_holder_pubkeys().htlc_basepoint;
3854-
let counterparty_pubkeys = funding.get_counterparty_pubkeys();
3855-
3856-
TxCreationKeys::derive_new(&self.secp_ctx, &per_commitment_point, delayed_payment_base, htlc_basepoint, &counterparty_pubkeys.revocation_basepoint, &counterparty_pubkeys.htlc_basepoint)
3857-
}
3858-
3859-
#[inline]
3860-
/// Creates a set of keys for build_commitment_transaction to generate a transaction which we
3861-
/// will sign and send to our counterparty.
3862-
/// If an Err is returned, it is a ChannelError::Close (for get_funding_created)
3863-
fn build_remote_transaction_keys(&self, funding: &FundingScope) -> TxCreationKeys {
3864-
let revocation_basepoint = &funding.get_holder_pubkeys().revocation_basepoint;
3865-
let htlc_basepoint = &funding.get_holder_pubkeys().htlc_basepoint;
3866-
let counterparty_pubkeys = funding.get_counterparty_pubkeys();
3867-
3868-
TxCreationKeys::derive_new(&self.secp_ctx, &self.counterparty_cur_commitment_point.unwrap(), &counterparty_pubkeys.delayed_payment_basepoint, &counterparty_pubkeys.htlc_basepoint, revocation_basepoint, htlc_basepoint)
3869-
}
3870-
38713842
pub fn get_feerate_sat_per_1000_weight(&self) -> u32 {
38723843
self.feerate_per_kw
38733844
}
@@ -4650,9 +4621,8 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
46504621
SP::Target: SignerProvider,
46514622
L::Target: Logger
46524623
{
4653-
let counterparty_keys = self.build_remote_transaction_keys(funding);
46544624
let counterparty_initial_commitment_tx = self.build_commitment_transaction(
4655-
funding, self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
4625+
funding, self.cur_counterparty_commitment_transaction_number, &self.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
46564626
match self.holder_signer {
46574627
// TODO (taproot|arik): move match into calling method for Taproot
46584628
ChannelSignerType::Ecdsa(ref ecdsa) => {
@@ -6365,8 +6335,7 @@ impl<SP: Deref> FundedChannel<SP> where
63656335
// Before proposing a feerate update, check that we can actually afford the new fee.
63666336
let dust_exposure_limiting_feerate = self.context.get_dust_exposure_limiting_feerate(&fee_estimator);
63676337
let htlc_stats = self.context.get_pending_htlc_stats(Some(feerate_per_kw), dust_exposure_limiting_feerate);
6368-
let keys = self.context.build_holder_transaction_keys(&self.funding, self.holder_commitment_point.current_point());
6369-
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.holder_commitment_point.transaction_number(), &keys, true, true, logger);
6338+
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.holder_commitment_point.transaction_number(), &self.holder_commitment_point.current_point(), true, true, logger);
63706339
let buffer_fee_msat = commit_tx_fee_sat(feerate_per_kw, commitment_stats.num_nondust_htlcs + htlc_stats.on_holder_tx_outbound_holding_cell_htlcs_count as usize + CONCURRENT_INBOUND_HTLC_FEE_BUFFER as usize, self.context.get_channel_type()) * 1000;
63716340
let holder_balance_msat = commitment_stats.local_balance_msat - htlc_stats.outbound_holding_cell_msat;
63726341
if holder_balance_msat < buffer_fee_msat + self.funding.counterparty_selected_channel_reserve_satoshis.unwrap() * 1000 {
@@ -6679,8 +6648,7 @@ impl<SP: Deref> FundedChannel<SP> where
66796648
self.holder_commitment_point.try_resolve_pending(&self.context.holder_signer, &self.context.secp_ctx, logger);
66806649
}
66816650
let funding_signed = if self.context.signer_pending_funding && !self.funding.is_outbound() {
6682-
let counterparty_keys = self.context.build_remote_transaction_keys(&self.funding);
6683-
let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number + 1, &counterparty_keys, false, false, logger).tx;
6651+
let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number + 1, &self.context.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
66846652
self.context.get_funding_signed_msg(&self.funding.channel_transaction_parameters, logger, counterparty_initial_commitment_tx)
66856653
} else { None };
66866654
// Provide a `channel_ready` message if we need to, but only if we're _not_ still pending
@@ -8753,8 +8721,7 @@ impl<SP: Deref> FundedChannel<SP> where
87538721
-> (Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)>, CommitmentTransaction)
87548722
where L::Target: Logger
87558723
{
8756-
let counterparty_keys = self.context.build_remote_transaction_keys(&self.funding);
8757-
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, true, logger);
8724+
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &self.context.counterparty_cur_commitment_point.unwrap(), false, true, logger);
87588725
let counterparty_commitment_tx = commitment_stats.tx;
87598726

87608727
#[cfg(any(test, fuzzing))]
@@ -8785,8 +8752,7 @@ impl<SP: Deref> FundedChannel<SP> where
87858752
#[cfg(any(test, fuzzing))]
87868753
self.build_commitment_no_state_update(logger);
87878754

8788-
let counterparty_keys = self.context.build_remote_transaction_keys(&self.funding);
8789-
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, true, logger);
8755+
let commitment_stats = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &self.context.counterparty_cur_commitment_point.unwrap(), false, true, logger);
87908756
let counterparty_commitment_txid = commitment_stats.tx.trust().txid();
87918757

87928758
match &self.context.holder_signer {
@@ -8814,6 +8780,7 @@ impl<SP: Deref> FundedChannel<SP> where
88148780
&counterparty_commitment_txid, encode::serialize_hex(&self.funding.get_funding_redeemscript()),
88158781
log_bytes!(signature.serialize_compact()[..]), &self.context.channel_id());
88168782

8783+
let counterparty_keys = commitment_stats.tx.trust().keys();
88178784
for (ref htlc_sig, ref htlc) in htlc_signatures.iter().zip(htlcs) {
88188785
log_trace!(logger, "Signed remote HTLC tx {} with redeemscript {} with pubkey {} -> {} in channel {}",
88198786
encode::serialize_hex(&chan_utils::build_htlc_transaction(&counterparty_commitment_txid, commitment_stats.feerate_per_kw, self.funding.get_holder_selected_contest_delay(), htlc, &self.context.channel_type, &counterparty_keys.broadcaster_delayed_payment_key, &counterparty_keys.revocation_key)),
@@ -9270,8 +9237,7 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
92709237

92719238
/// Only allowed after [`FundingScope::channel_transaction_parameters`] is set.
92729239
fn get_funding_created_msg<L: Deref>(&mut self, logger: &L) -> Option<msgs::FundingCreated> where L::Target: Logger {
9273-
let counterparty_keys = self.context.build_remote_transaction_keys(&self.funding);
9274-
let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
9240+
let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(&self.funding, self.context.cur_counterparty_commitment_transaction_number, &self.context.counterparty_cur_commitment_point.unwrap(), false, false, logger).tx;
92759241
let signature = match &self.context.holder_signer {
92769242
// TODO (taproot|arik): move match into calling method for Taproot
92779243
ChannelSignerType::Ecdsa(ecdsa) => {
@@ -11835,7 +11801,7 @@ mod tests {
1183511801
use bitcoin::secp256k1::Message;
1183611802
use crate::sign::{ChannelDerivationParameters, HTLCDescriptor, ecdsa::EcdsaChannelSigner};
1183711803
use crate::types::payment::PaymentPreimage;
11838-
use crate::ln::channel::{HTLCOutputInCommitment ,TxCreationKeys};
11804+
use crate::ln::channel::HTLCOutputInCommitment;
1183911805
use crate::ln::channel_keys::{DelayedPaymentBasepoint, HtlcBasepoint};
1184011806
use crate::ln::chan_utils::{ChannelPublicKeys, HolderCommitmentTransaction, CounterpartyChannelTransactionParameters};
1184111807
use crate::util::logger::Logger;
@@ -11903,11 +11869,6 @@ mod tests {
1190311869
// build_commitment_transaction.
1190411870
let per_commitment_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("1f1e1d1c1b1a191817161514131211100f0e0d0c0b0a09080706050403020100").unwrap()[..]).unwrap();
1190511871
let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);
11906-
let directed_params = chan.funding.channel_transaction_parameters.as_holder_broadcastable();
11907-
let keys = TxCreationKeys::from_channel_static_keys(
11908-
&per_commitment_point, directed_params.broadcaster_pubkeys(),
11909-
directed_params.countersignatory_pubkeys(), &secp_ctx,
11910-
);
1191111872

1191211873
macro_rules! test_commitment {
1191311874
( $counterparty_sig_hex: expr, $sig_hex: expr, $tx_hex: expr, $($remain:tt)* ) => {
@@ -11928,7 +11889,7 @@ mod tests {
1192811889
$( { $htlc_idx: expr, $counterparty_htlc_sig_hex: expr, $htlc_sig_hex: expr, $htlc_tx_hex: expr } ), *
1192911890
} ) => { {
1193011891
let (commitment_tx, htlcs): (_, Vec<HTLCOutputInCommitment>) = {
11931-
let mut commitment_stats = chan.context.build_commitment_transaction(&chan.funding, 0xffffffffffff - 42, &keys, true, false, &logger);
11892+
let mut commitment_stats = chan.context.build_commitment_transaction(&chan.funding, 0xffffffffffff - 42, &per_commitment_point, true, false, &logger);
1193211893

1193311894
let htlcs = commitment_stats.htlcs_included.drain(..)
1193411895
.filter_map(|(htlc, _)| if htlc.transaction_output_index.is_some() { Some(htlc) } else { None })
@@ -11976,6 +11937,7 @@ mod tests {
1197611937
let remote_signature = Signature::from_der(&<Vec<u8>>::from_hex($counterparty_htlc_sig_hex).unwrap()[..]).unwrap();
1197711938

1197811939
let ref htlc = htlcs[$htlc_idx];
11940+
let keys = commitment_tx.trust().keys();
1197911941
let mut htlc_tx = chan_utils::build_htlc_transaction(&unsigned_tx.txid, chan.context.feerate_per_kw,
1198011942
chan.funding.get_counterparty_selected_contest_delay().unwrap(),
1198111943
&htlc, $opt_anchors, &keys.broadcaster_delayed_payment_key, &keys.revocation_key);

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