Merge pull request #2641 from alexanderwiederin/2585-preflight-test-coverage
[rust-lightning] / lightning / src / chain / onchaintx.rs
index 42cfb91bd0a87c1c2ebad8d6eac5d3a151160159..5aba6593834cf3a37848fe1c9763e6b5f6de7f3a 100644 (file)
 //! OnchainTxHandler objects are fully-part of ChannelMonitor and encapsulates all
 //! building, tracking, bumping and notifications functions.
 
-#[cfg(anchors)]
 use bitcoin::PackedLockTime;
 use bitcoin::blockdata::transaction::Transaction;
 use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
 use bitcoin::blockdata::script::Script;
-use bitcoin::hashes::Hash;
-#[cfg(anchors)]
-use bitcoin::hashes::HashEngine;
-#[cfg(anchors)]
+use bitcoin::hashes::{Hash, HashEngine};
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hash_types::{Txid, BlockHash};
 use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
 use bitcoin::secp256k1;
 
-use crate::sign::{ChannelSigner, EntropySource, SignerProvider};
+use crate::chain::chaininterface::compute_feerate_sat_per_1000_weight;
+use crate::sign::{ChannelDerivationParameters, HTLCDescriptor, ChannelSigner, EntropySource, SignerProvider, WriteableEcdsaChannelSigner};
 use crate::ln::msgs::DecodeError;
 use crate::ln::PaymentPreimage;
-#[cfg(anchors)]
-use crate::ln::chan_utils::{self, HTLCOutputInCommitment};
-use crate::ln::chan_utils::{ChannelTransactionParameters, HolderCommitmentTransaction};
+use crate::ln::chan_utils::{self, ChannelTransactionParameters, HTLCOutputInCommitment, HolderCommitmentTransaction};
 use crate::chain::ClaimId;
-#[cfg(anchors)]
-use crate::chain::chaininterface::ConfirmationTarget;
-use crate::chain::chaininterface::{FeeEstimator, BroadcasterInterface, LowerBoundedFeeEstimator};
+use crate::chain::chaininterface::{ConfirmationTarget, FeeEstimator, BroadcasterInterface, LowerBoundedFeeEstimator};
 use crate::chain::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER};
-use crate::sign::WriteableEcdsaChannelSigner;
-#[cfg(anchors)]
-use crate::chain::package::PackageSolvingData;
-use crate::chain::package::PackageTemplate;
+use crate::chain::package::{PackageSolvingData, PackageTemplate};
 use crate::util::logger::Logger;
 use crate::util::ser::{Readable, ReadableArgs, MaybeReadable, UpgradableRequired, Writer, Writeable, VecWriter};
 
@@ -50,7 +40,6 @@ use alloc::collections::BTreeMap;
 use core::cmp;
 use core::ops::Deref;
 use core::mem::replace;
-#[cfg(anchors)]
 use core::mem::swap;
 use crate::ln::features::ChannelTypeFeatures;
 
@@ -60,7 +49,7 @@ const MAX_ALLOC_SIZE: usize = 64*1024;
 /// transaction causing it.
 ///
 /// Used to determine when the on-chain event can be considered safe from a chain reorganization.
-#[derive(PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 struct OnchainEventEntry {
        txid: Txid,
        height: u32,
@@ -80,7 +69,7 @@ impl OnchainEventEntry {
 
 /// Events for claims the [`OnchainTxHandler`] has generated. Once the events are considered safe
 /// from a chain reorg, the [`OnchainTxHandler`] will act accordingly.
-#[derive(PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 enum OnchainEvent {
        /// A pending request has been claimed by a transaction spending the exact same set of outpoints
        /// as the request. This claim can either be ours or from the counterparty. Once the claiming
@@ -181,8 +170,8 @@ impl Writeable for Option<Vec<Option<(usize, Signature)>>> {
        }
 }
 
-#[cfg(anchors)]
 /// The claim commonly referred to as the pre-signed second-stage HTLC transaction.
+#[derive(Clone, PartialEq, Eq)]
 pub(crate) struct ExternalHTLCClaim {
        pub(crate) commitment_txid: Txid,
        pub(crate) per_commitment_number: u64,
@@ -193,7 +182,7 @@ pub(crate) struct ExternalHTLCClaim {
 
 // Represents the different types of claims for which events are yielded externally to satisfy said
 // claims.
-#[cfg(anchors)]
+#[derive(Clone, PartialEq, Eq)]
 pub(crate) enum ClaimEvent {
        /// Event yielded to signal that the commitment transaction fee must be bumped to claim any
        /// encumbered funds and proceed to HTLC resolution, if any HTLCs exist.
@@ -216,7 +205,6 @@ pub(crate) enum ClaimEvent {
 pub(crate) enum OnchainClaim {
        /// A finalized transaction pending confirmation spending the output to claim.
        Tx(Transaction),
-       #[cfg(anchors)]
        /// An event yielded externally to signal additional inputs must be added to a transaction
        /// pending confirmation spending the output to claim.
        Event(ClaimEvent),
@@ -224,15 +212,13 @@ pub(crate) enum OnchainClaim {
 
 /// OnchainTxHandler receives claiming requests, aggregates them if it's sound, broadcast and
 /// 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,
@@ -263,7 +249,6 @@ pub struct OnchainTxHandler<ChannelSigner: WriteableEcdsaChannelSigner> {
        //      - A channel has been force closed by broadcasting the holder's latest commitment transaction
        //      - A block being connected/disconnected
        //      - Learning the preimage for an HTLC we can claim onchain
-       #[cfg(anchors)]
        pending_claim_events: Vec<(ClaimId, ClaimEvent)>,
 
        // Used to link outpoints claimed in a connected block to a pending claim request. The keys
@@ -287,11 +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 &&
@@ -309,9 +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)?;
 
@@ -366,9 +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)?;
 
@@ -429,18 +414,17 @@ 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,
                        locktimed_packages,
                        pending_claim_requests,
                        onchain_events_awaiting_threshold_conf,
-                       #[cfg(anchors)]
                        pending_claim_events: Vec::new(),
                        secp_ctx,
                })
@@ -448,20 +432,23 @@ 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(),
                        claimable_outpoints: HashMap::new(),
                        locktimed_packages: BTreeMap::new(),
                        onchain_events_awaiting_threshold_conf: Vec::new(),
-                       #[cfg(anchors)]
                        pending_claim_events: Vec::new(),
                        secp_ctx,
                }
@@ -475,7 +462,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                self.holder_commitment.to_broadcaster_value_sat()
        }
 
-       #[cfg(anchors)]
        pub(crate) fn get_and_clear_pending_claim_events(&mut self) -> Vec<(ClaimId, ClaimEvent)> {
                let mut events = Vec::new();
                swap(&mut events, &mut self.pending_claim_events);
@@ -516,7 +502,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                                                        log_info!(logger, "{} onchain {}", log_start, log_tx!(tx));
                                                        broadcaster.broadcast_transactions(&[&tx]);
                                                },
-                                               #[cfg(anchors)]
                                                OnchainClaim::Event(event) => {
                                                        let log_start = if bumped_feerate { "Yielding fee-bumped" } else { "Replaying" };
                                                        log_info!(logger, "{} onchain event to spend inputs {:?}", log_start,
@@ -593,25 +578,22 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                // didn't receive confirmation of it before, or not enough reorg-safe depth on top of it).
                let new_timer = cached_request.get_height_timer(cur_height);
                if cached_request.is_malleable() {
-                       #[cfg(anchors)]
-                       { // Attributes are not allowed on if expressions on our current MSRV of 1.41.
-                               if cached_request.requires_external_funding() {
-                                       let target_feerate_sat_per_1000_weight = cached_request.compute_package_feerate(
-                                               fee_estimator, ConfirmationTarget::HighPriority, force_feerate_bump
-                                       );
-                                       if let Some(htlcs) = cached_request.construct_malleable_package_with_external_funding(self) {
-                                               return Some((
-                                                       new_timer,
-                                                       target_feerate_sat_per_1000_weight as u64,
-                                                       OnchainClaim::Event(ClaimEvent::BumpHTLC {
-                                                               target_feerate_sat_per_1000_weight,
-                                                               htlcs,
-                                                               tx_lock_time: PackedLockTime(cached_request.package_locktime(cur_height)),
-                                                       }),
-                                               ));
-                                       } else {
-                                               return None;
-                                       }
+                       if cached_request.requires_external_funding() {
+                               let target_feerate_sat_per_1000_weight = cached_request.compute_package_feerate(
+                                       fee_estimator, ConfirmationTarget::OnChainSweep, force_feerate_bump
+                               );
+                               if let Some(htlcs) = cached_request.construct_malleable_package_with_external_funding(self) {
+                                       return Some((
+                                               new_timer,
+                                               target_feerate_sat_per_1000_weight as u64,
+                                               OnchainClaim::Event(ClaimEvent::BumpHTLC {
+                                                       target_feerate_sat_per_1000_weight,
+                                                       htlcs,
+                                                       tx_lock_time: PackedLockTime(cached_request.package_locktime(cur_height)),
+                                               }),
+                                       ));
+                               } else {
+                                       return None;
                                }
                        }
 
@@ -633,9 +615,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                        // Untractable packages cannot have their fees bumped through Replace-By-Fee. Some
                        // packages may support fee bumping through Child-Pays-For-Parent, indicated by those
                        // which require external funding.
-                       #[cfg(not(anchors))]
-                       let inputs = cached_request.inputs();
-                       #[cfg(anchors)]
                        let mut inputs = cached_request.inputs();
                        debug_assert_eq!(inputs.len(), 1);
                        let tx = match cached_request.finalize_untractable_package(self, logger) {
@@ -645,13 +624,28 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                        if !cached_request.requires_external_funding() {
                                return Some((new_timer, 0, OnchainClaim::Tx(tx)));
                        }
-                       #[cfg(anchors)]
                        return inputs.find_map(|input| match input {
                                // Commitment inputs with anchors support are the only untractable inputs supported
                                // thus far that require external funding.
-                               PackageSolvingData::HolderFundingOutput(..) => {
+                               PackageSolvingData::HolderFundingOutput(output) => {
                                        debug_assert_eq!(tx.txid(), self.holder_commitment.trust().txid(),
                                                "Holder commitment transaction mismatch");
+
+                                       let conf_target = ConfirmationTarget::OnChainSweep;
+                                       let package_target_feerate_sat_per_1000_weight = cached_request
+                                               .compute_package_feerate(fee_estimator, conf_target, force_feerate_bump);
+                                       if let Some(input_amount_sat) = output.funding_amount {
+                                               let fee_sat = input_amount_sat - tx.output.iter().map(|output| output.value).sum::<u64>();
+                                               let commitment_tx_feerate_sat_per_1000_weight =
+                                                       compute_feerate_sat_per_1000_weight(fee_sat, tx.weight() as u64);
+                                               if commitment_tx_feerate_sat_per_1000_weight >= package_target_feerate_sat_per_1000_weight {
+                                                       log_debug!(logger, "Pre-signed {} already has feerate {} sat/kW above required {} sat/kW",
+                                                               log_tx!(tx), commitment_tx_feerate_sat_per_1000_weight,
+                                                               package_target_feerate_sat_per_1000_weight);
+                                                       return Some((new_timer, 0, OnchainClaim::Tx(tx.clone())));
+                                               }
+                                       }
+
                                        // We'll locate an anchor output we can spend within the commitment transaction.
                                        let funding_pubkey = &self.channel_transaction_parameters.holder_pubkeys.funding_pubkey;
                                        match chan_utils::get_anchor_output(&tx, funding_pubkey) {
@@ -659,9 +653,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                                                Some((idx, _)) => {
                                                        // TODO: Use a lower confirmation target when both our and the
                                                        // counterparty's latest commitment don't have any HTLCs present.
-                                                       let conf_target = ConfirmationTarget::HighPriority;
-                                                       let package_target_feerate_sat_per_1000_weight = cached_request
-                                                               .compute_package_feerate(fee_estimator, conf_target, force_feerate_bump);
                                                        Some((
                                                                new_timer,
                                                                package_target_feerate_sat_per_1000_weight as u64,
@@ -765,13 +756,15 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                        ) {
                                req.set_timer(new_timer);
                                req.set_feerate(new_feerate);
+                               // Once a pending claim has an id assigned, it remains fixed until the claim is
+                               // satisfied, regardless of whether the claim switches between different variants of
+                               // `OnchainClaim`.
                                let claim_id = match claim {
                                        OnchainClaim::Tx(tx) => {
                                                log_info!(logger, "Broadcasting onchain {}", log_tx!(tx));
                                                broadcaster.broadcast_transactions(&[&tx]);
                                                ClaimId(tx.txid().into_inner())
                                        },
-                                       #[cfg(anchors)]
                                        OnchainClaim::Event(claim_event) => {
                                                log_info!(logger, "Yielding onchain event to spend inputs {:?}", req.outpoints());
                                                let claim_id = match claim_event {
@@ -886,14 +879,12 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                                                                // input(s) that already have a confirmed spend. If such spend is
                                                                // reorged out of the chain, then we'll attempt to re-spend the
                                                                // inputs once we see it.
-                                                               #[cfg(anchors)] {
-                                                                       #[cfg(debug_assertions)] {
-                                                                               let existing = self.pending_claim_events.iter()
-                                                                                       .filter(|entry| entry.0 == *claim_id).count();
-                                                                               assert!(existing == 0 || existing == 1);
-                                                                       }
-                                                                       self.pending_claim_events.retain(|entry| entry.0 != *claim_id);
+                                                               #[cfg(debug_assertions)] {
+                                                                       let existing = self.pending_claim_events.iter()
+                                                                               .filter(|entry| entry.0 == *claim_id).count();
+                                                                       assert!(existing == 0 || existing == 1);
                                                                }
+                                                               self.pending_claim_events.retain(|entry| entry.0 != *claim_id);
                                                        }
                                                }
                                                break; //No need to iterate further, either tx is our or their
@@ -930,14 +921,12 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                                                                        outpoint, log_bytes!(claim_id.0));
                                                                self.claimable_outpoints.remove(outpoint);
                                                        }
-                                                       #[cfg(anchors)] {
-                                                               #[cfg(debug_assertions)] {
-                                                                       let num_existing = self.pending_claim_events.iter()
-                                                                               .filter(|entry| entry.0 == claim_id).count();
-                                                                       assert!(num_existing == 0 || num_existing == 1);
-                                                               }
-                                                               self.pending_claim_events.retain(|(id, _)| *id != claim_id);
+                                                       #[cfg(debug_assertions)] {
+                                                               let num_existing = self.pending_claim_events.iter()
+                                                                       .filter(|entry| entry.0 == claim_id).count();
+                                                               assert!(num_existing == 0 || num_existing == 1);
                                                        }
+                                                       self.pending_claim_events.retain(|(id, _)| *id != claim_id);
                                                }
                                        },
                                        OnchainEvent::ContentiousOutpoint { package } => {
@@ -969,7 +958,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                                                log_info!(logger, "Broadcasting RBF-bumped onchain {}", log_tx!(bump_tx));
                                                broadcaster.broadcast_transactions(&[&bump_tx]);
                                        },
-                                       #[cfg(anchors)]
                                        OnchainClaim::Event(claim_event) => {
                                                log_info!(logger, "Yielding RBF-bumped onchain event to spend inputs {:?}", request.outpoints());
                                                #[cfg(debug_assertions)] {
@@ -1055,7 +1043,6 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
                                                log_info!(logger, "Broadcasting onchain {}", log_tx!(bump_tx));
                                                broadcaster.broadcast_transactions(&[&bump_tx]);
                                        },
-                                       #[cfg(anchors)]
                                        OnchainClaim::Event(claim_event) => {
                                                log_info!(logger, "Yielding onchain event after reorg to spend inputs {:?}", request.outpoints());
                                                #[cfg(debug_assertions)] {
@@ -1101,91 +1088,67 @@ 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 {
+               &self.holder_commitment.trust().built_transaction().transaction
        }
 
        //TODO: getting lastest holder transactions should be infallible and result in us "force-closing the channel", but we may
-       // have empty holder commitment transaction if a ChannelMonitor is asked to force-close just after Channel::get_outbound_funding_created,
+       // have empty holder commitment transaction if a ChannelMonitor is asked to force-close just after OutboundV1Channel::get_funding_created,
        // 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)))
        }
 
-       #[cfg(anchors)]
        pub(crate) fn generate_external_htlc_claim(
                &self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>
        ) -> Option<ExternalHTLCClaim> {
@@ -1219,18 +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
-       }
 }