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Use sign_holder_htlc_transaction to sign non-anchors holder HTLCs #2667

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Merged
merged 6 commits into from
Oct 20, 2023
Merged

Use sign_holder_htlc_transaction to sign non-anchors holder HTLCs #2667

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9510e29
Support signing non-anchors HTLCs with HTLCDescriptor
wpaulino Oct 13, 2023
5958604
Provide missing derivation parameters to OnchainTxHandler
wpaulino Oct 13, 2023
03ec746
Use sign_holder_htlc_transaction to sign non-anchors holder HTLCs
wpaulino Oct 13, 2023
a9d9d26
Remove caching of holder HTLC signatures
wpaulino Oct 13, 2023
aae4e7c
Don't sign holder HTLCs along with holder commitments
wpaulino Oct 13, 2023
b06a652
Move HTLCDescriptor to sign module
wpaulino Oct 16, 2023
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14 changes: 8 additions & 6 deletions lightning/src/chain/channelmonitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,15 +42,15 @@ use crate::chain;
use crate::chain::{BestBlock, WatchedOutput};
use crate::chain::chaininterface::{BroadcasterInterface, FeeEstimator, LowerBoundedFeeEstimator};
use crate::chain::transaction::{OutPoint, TransactionData};
use crate::sign::{SpendableOutputDescriptor, StaticPaymentOutputDescriptor, DelayedPaymentOutputDescriptor, WriteableEcdsaChannelSigner, SignerProvider, EntropySource};
use crate::sign::{ChannelDerivationParameters, HTLCDescriptor, SpendableOutputDescriptor, StaticPaymentOutputDescriptor, DelayedPaymentOutputDescriptor, WriteableEcdsaChannelSigner, SignerProvider, EntropySource};
use crate::chain::onchaintx::{ClaimEvent, OnchainTxHandler};
use crate::chain::package::{CounterpartyOfferedHTLCOutput, CounterpartyReceivedHTLCOutput, HolderFundingOutput, HolderHTLCOutput, PackageSolvingData, PackageTemplate, RevokedOutput, RevokedHTLCOutput};
use crate::chain::Filter;
use crate::util::logger::Logger;
use crate::util::ser::{Readable, ReadableArgs, RequiredWrapper, MaybeReadable, UpgradableRequired, Writer, Writeable, U48};
use crate::util::byte_utils;
use crate::events::{Event, EventHandler};
use crate::events::bump_transaction::{ChannelDerivationParameters, AnchorDescriptor, HTLCDescriptor, BumpTransactionEvent};
use crate::events::bump_transaction::{AnchorDescriptor, BumpTransactionEvent};

use crate::prelude::*;
use core::{cmp, mem};
Expand Down Expand Up @@ -1172,9 +1172,10 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
(holder_commitment_tx, trusted_tx.commitment_number())
};

let onchain_tx_handler =
OnchainTxHandler::new(destination_script.clone(), keys,
channel_parameters.clone(), initial_holder_commitment_tx, secp_ctx);
let onchain_tx_handler = OnchainTxHandler::new(
channel_value_satoshis, channel_keys_id, destination_script.clone(), keys,
channel_parameters.clone(), initial_holder_commitment_tx, secp_ctx
);

let mut outputs_to_watch = HashMap::new();
outputs_to_watch.insert(funding_info.0.txid, vec![(funding_info.0.index as u32, funding_info.1.clone())]);
Expand Down Expand Up @@ -2835,6 +2836,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
per_commitment_point: self.onchain_tx_handler.signer.get_per_commitment_point(
htlc.per_commitment_number, &self.onchain_tx_handler.secp_ctx,
),
feerate_per_kw: 0,
htlc: htlc.htlc,
preimage: htlc.preimage,
counterparty_sig: htlc.counterparty_sig,
Expand Down Expand Up @@ -3354,7 +3356,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
continue;
}
} else { None };
if let Some(htlc_tx) = self.onchain_tx_handler.unsafe_get_fully_signed_htlc_tx(
if let Some(htlc_tx) = self.onchain_tx_handler.get_fully_signed_htlc_tx(
&::bitcoin::OutPoint { txid, vout }, &preimage) {
holder_transactions.push(htlc_tx);
}
Expand Down
155 changes: 57 additions & 98 deletions lightning/src/chain/onchaintx.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,14 +23,13 @@ use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
use bitcoin::secp256k1;

use crate::chain::chaininterface::compute_feerate_sat_per_1000_weight;
use crate::sign::{ChannelSigner, EntropySource, SignerProvider};
use crate::sign::{ChannelDerivationParameters, HTLCDescriptor, ChannelSigner, EntropySource, SignerProvider, WriteableEcdsaChannelSigner};
use crate::ln::msgs::DecodeError;
use crate::ln::PaymentPreimage;
use crate::ln::chan_utils::{self, ChannelTransactionParameters, HTLCOutputInCommitment, HolderCommitmentTransaction};
use crate::chain::ClaimId;
use crate::chain::chaininterface::{ConfirmationTarget, FeeEstimator, BroadcasterInterface, LowerBoundedFeeEstimator};
use crate::chain::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER};
use crate::sign::WriteableEcdsaChannelSigner;
use crate::chain::package::{PackageSolvingData, PackageTemplate};
use crate::util::logger::Logger;
use crate::util::ser::{Readable, ReadableArgs, MaybeReadable, UpgradableRequired, Writer, Writeable, VecWriter};
Expand Down Expand Up @@ -215,14 +214,11 @@ pub(crate) enum OnchainClaim {
/// do RBF bumping if possible.
#[derive(Clone)]
pub struct OnchainTxHandler<ChannelSigner: WriteableEcdsaChannelSigner> {
channel_value_satoshis: u64,
channel_keys_id: [u8; 32],
destination_script: Script,
holder_commitment: HolderCommitmentTransaction,
// holder_htlc_sigs and prev_holder_htlc_sigs are in the order as they appear in the commitment
// transaction outputs (hence the Option<>s inside the Vec). The first usize is the index in
// the set of HTLCs in the HolderCommitmentTransaction.
holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,
prev_holder_commitment: Option<HolderCommitmentTransaction>,
prev_holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,

pub(super) signer: ChannelSigner,
pub(crate) channel_transaction_parameters: ChannelTransactionParameters,
Expand Down Expand Up @@ -276,11 +272,11 @@ pub struct OnchainTxHandler<ChannelSigner: WriteableEcdsaChannelSigner> {
impl<ChannelSigner: WriteableEcdsaChannelSigner> PartialEq for OnchainTxHandler<ChannelSigner> {
fn eq(&self, other: &Self) -> bool {
// `signer`, `secp_ctx`, and `pending_claim_events` are excluded on purpose.
self.destination_script == other.destination_script &&
self.channel_value_satoshis == other.channel_value_satoshis &&
self.channel_keys_id == other.channel_keys_id &&
self.destination_script == other.destination_script &&
self.holder_commitment == other.holder_commitment &&
self.holder_htlc_sigs == other.holder_htlc_sigs &&
self.prev_holder_commitment == other.prev_holder_commitment &&
self.prev_holder_htlc_sigs == other.prev_holder_htlc_sigs &&
self.channel_transaction_parameters == other.channel_transaction_parameters &&
self.pending_claim_requests == other.pending_claim_requests &&
self.claimable_outpoints == other.claimable_outpoints &&
Expand All @@ -298,9 +294,9 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>

self.destination_script.write(writer)?;
self.holder_commitment.write(writer)?;
self.holder_htlc_sigs.write(writer)?;
None::<Option<Vec<Option<(usize, Signature)>>>>.write(writer)?; // holder_htlc_sigs
self.prev_holder_commitment.write(writer)?;
self.prev_holder_htlc_sigs.write(writer)?;
None::<Option<Vec<Option<(usize, Signature)>>>>.write(writer)?; // prev_holder_htlc_sigs

self.channel_transaction_parameters.write(writer)?;

Expand Down Expand Up @@ -355,9 +351,9 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
let destination_script = Readable::read(reader)?;

let holder_commitment = Readable::read(reader)?;
let holder_htlc_sigs = Readable::read(reader)?;
let _holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>> = Readable::read(reader)?;
let prev_holder_commitment = Readable::read(reader)?;
let prev_holder_htlc_sigs = Readable::read(reader)?;
let _prev_holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>> = Readable::read(reader)?;

let channel_parameters = Readable::read(reader)?;

Expand Down Expand Up @@ -418,11 +414,11 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());

Ok(OnchainTxHandler {
channel_value_satoshis,
channel_keys_id,
destination_script,
holder_commitment,
holder_htlc_sigs,
prev_holder_commitment,
prev_holder_htlc_sigs,
signer,
channel_transaction_parameters: channel_parameters,
claimable_outpoints,
Expand All @@ -436,13 +432,17 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
}

impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner> {
pub(crate) fn new(destination_script: Script, signer: ChannelSigner, channel_parameters: ChannelTransactionParameters, holder_commitment: HolderCommitmentTransaction, secp_ctx: Secp256k1<secp256k1::All>) -> Self {
pub(crate) fn new(
channel_value_satoshis: u64, channel_keys_id: [u8; 32], destination_script: Script,
signer: ChannelSigner, channel_parameters: ChannelTransactionParameters,
holder_commitment: HolderCommitmentTransaction, secp_ctx: Secp256k1<secp256k1::All>
) -> Self {
OnchainTxHandler {
channel_value_satoshis,
channel_keys_id,
destination_script,
holder_commitment,
holder_htlc_sigs: None,
prev_holder_commitment: None,
prev_holder_htlc_sigs: None,
signer,
channel_transaction_parameters: channel_parameters,
pending_claim_requests: HashMap::new(),
Expand Down Expand Up @@ -1088,39 +1088,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>

pub(crate) fn provide_latest_holder_tx(&mut self, tx: HolderCommitmentTransaction) {
self.prev_holder_commitment = Some(replace(&mut self.holder_commitment, tx));
self.holder_htlc_sigs = None;
}

// Normally holder HTLCs are signed at the same time as the holder commitment tx. However,
// in some configurations, the holder commitment tx has been signed and broadcast by a
// ChannelMonitor replica, so we handle that case here.
fn sign_latest_holder_htlcs(&mut self) {
if self.holder_htlc_sigs.is_none() {
let (_sig, sigs) = self.signer.sign_holder_commitment_and_htlcs(&self.holder_commitment, &self.secp_ctx).expect("sign holder commitment");
self.holder_htlc_sigs = Some(Self::extract_holder_sigs(&self.holder_commitment, sigs));
}
}

// Normally only the latest commitment tx and HTLCs need to be signed. However, in some
// configurations we may have updated our holder commitment but a replica of the ChannelMonitor
// broadcast the previous one before we sync with it. We handle that case here.
fn sign_prev_holder_htlcs(&mut self) {
if self.prev_holder_htlc_sigs.is_none() {
if let Some(ref holder_commitment) = self.prev_holder_commitment {
let (_sig, sigs) = self.signer.sign_holder_commitment_and_htlcs(holder_commitment, &self.secp_ctx).expect("sign previous holder commitment");
self.prev_holder_htlc_sigs = Some(Self::extract_holder_sigs(holder_commitment, sigs));
}
}
}

fn extract_holder_sigs(holder_commitment: &HolderCommitmentTransaction, sigs: Vec<Signature>) -> Vec<Option<(usize, Signature)>> {
let mut ret = Vec::new();
for (htlc_idx, (holder_sig, htlc)) in sigs.iter().zip(holder_commitment.htlcs().iter()).enumerate() {
let tx_idx = htlc.transaction_output_index.unwrap();
if ret.len() <= tx_idx as usize { ret.resize(tx_idx as usize + 1, None); }
ret[tx_idx as usize] = Some((htlc_idx, holder_sig.clone()));
}
ret
}

pub(crate) fn get_unsigned_holder_commitment_tx(&self) -> &Transaction {
Expand All @@ -1132,48 +1099,54 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
// before providing a initial commitment transaction. For outbound channel, init ChannelMonitor at Channel::funding_signed, there is nothing
// to monitor before.
pub(crate) fn get_fully_signed_holder_tx(&mut self, funding_redeemscript: &Script) -> Transaction {
let (sig, htlc_sigs) = self.signer.sign_holder_commitment_and_htlcs(&self.holder_commitment, &self.secp_ctx).expect("signing holder commitment");
self.holder_htlc_sigs = Some(Self::extract_holder_sigs(&self.holder_commitment, htlc_sigs));
let sig = self.signer.sign_holder_commitment(&self.holder_commitment, &self.secp_ctx).expect("signing holder commitment");
self.holder_commitment.add_holder_sig(funding_redeemscript, sig)
}

#[cfg(any(test, feature="unsafe_revoked_tx_signing"))]
pub(crate) fn get_fully_signed_copy_holder_tx(&mut self, funding_redeemscript: &Script) -> Transaction {
let (sig, htlc_sigs) = self.signer.unsafe_sign_holder_commitment_and_htlcs(&self.holder_commitment, &self.secp_ctx).expect("sign holder commitment");
self.holder_htlc_sigs = Some(Self::extract_holder_sigs(&self.holder_commitment, htlc_sigs));
let sig = self.signer.unsafe_sign_holder_commitment(&self.holder_commitment, &self.secp_ctx).expect("sign holder commitment");
self.holder_commitment.add_holder_sig(funding_redeemscript, sig)
}

pub(crate) fn get_fully_signed_htlc_tx(&mut self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>) -> Option<Transaction> {
let mut htlc_tx = None;
let commitment_txid = self.holder_commitment.trust().txid();
// Check if the HTLC spends from the current holder commitment
if commitment_txid == outp.txid {
self.sign_latest_holder_htlcs();
if let &Some(ref htlc_sigs) = &self.holder_htlc_sigs {
let &(ref htlc_idx, ref htlc_sig) = htlc_sigs[outp.vout as usize].as_ref().unwrap();
let trusted_tx = self.holder_commitment.trust();
let counterparty_htlc_sig = self.holder_commitment.counterparty_htlc_sigs[*htlc_idx];
htlc_tx = Some(trusted_tx
.get_signed_htlc_tx(&self.channel_transaction_parameters.as_holder_broadcastable(), *htlc_idx, &counterparty_htlc_sig, htlc_sig, preimage));
}
}
// If the HTLC doesn't spend the current holder commitment, check if it spends the previous one
if htlc_tx.is_none() && self.prev_holder_commitment.is_some() {
let commitment_txid = self.prev_holder_commitment.as_ref().unwrap().trust().txid();
if commitment_txid == outp.txid {
self.sign_prev_holder_htlcs();
if let &Some(ref htlc_sigs) = &self.prev_holder_htlc_sigs {
let &(ref htlc_idx, ref htlc_sig) = htlc_sigs[outp.vout as usize].as_ref().unwrap();
let holder_commitment = self.prev_holder_commitment.as_ref().unwrap();
let trusted_tx = holder_commitment.trust();
let counterparty_htlc_sig = holder_commitment.counterparty_htlc_sigs[*htlc_idx];
htlc_tx = Some(trusted_tx
.get_signed_htlc_tx(&self.channel_transaction_parameters.as_holder_broadcastable(), *htlc_idx, &counterparty_htlc_sig, htlc_sig, preimage));
}
let get_signed_htlc_tx = |holder_commitment: &HolderCommitmentTransaction| {
let trusted_tx = holder_commitment.trust();
if trusted_tx.txid() != outp.txid {
return None;
}
}
htlc_tx
let (htlc_idx, htlc) = trusted_tx.htlcs().iter().enumerate()
.find(|(_, htlc)| htlc.transaction_output_index.unwrap() == outp.vout)
.unwrap();
let counterparty_htlc_sig = holder_commitment.counterparty_htlc_sigs[htlc_idx];
let mut htlc_tx = trusted_tx.build_unsigned_htlc_tx(
&self.channel_transaction_parameters.as_holder_broadcastable(), htlc_idx, preimage,
);

let htlc_descriptor = HTLCDescriptor {
channel_derivation_parameters: ChannelDerivationParameters {
value_satoshis: self.channel_value_satoshis,
keys_id: self.channel_keys_id,
transaction_parameters: self.channel_transaction_parameters.clone(),
},
commitment_txid: trusted_tx.txid(),
per_commitment_number: trusted_tx.commitment_number(),
per_commitment_point: trusted_tx.per_commitment_point(),
feerate_per_kw: trusted_tx.feerate_per_kw(),
htlc: htlc.clone(),
preimage: preimage.clone(),
counterparty_sig: counterparty_htlc_sig.clone(),
};
let htlc_sig = self.signer.sign_holder_htlc_transaction(&htlc_tx, 0, &htlc_descriptor, &self.secp_ctx).unwrap();
htlc_tx.input[0].witness = trusted_tx.build_htlc_input_witness(
htlc_idx, &counterparty_htlc_sig, &htlc_sig, preimage,
);
Some(htlc_tx)
};

// Check if the HTLC spends from the current holder commitment first, or the previous.
get_signed_htlc_tx(&self.holder_commitment)
.or_else(|| self.prev_holder_commitment.as_ref().and_then(|prev_holder_commitment| get_signed_htlc_tx(prev_holder_commitment)))
}

pub(crate) fn generate_external_htlc_claim(
Expand Down Expand Up @@ -1209,18 +1182,4 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
pub(crate) fn channel_type_features(&self) -> &ChannelTypeFeatures {
&self.channel_transaction_parameters.channel_type_features
}

#[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
pub(crate) fn unsafe_get_fully_signed_htlc_tx(&mut self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>) -> Option<Transaction> {
let latest_had_sigs = self.holder_htlc_sigs.is_some();
let prev_had_sigs = self.prev_holder_htlc_sigs.is_some();
let ret = self.get_fully_signed_htlc_tx(outp, preimage);
if !latest_had_sigs {
self.holder_htlc_sigs = None;
}
if !prev_had_sigs {
self.prev_holder_htlc_sigs = None;
}
ret
}
}
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