Merge pull request #2101 from TheBlueMatt/2023-03-one-less-sig
[rust-lightning] / lightning / src / chain / package.rs
index 20507c3f942278974905ab878e3a5f4c4c828f49..e8886e5a2aa49958fcac012529a3ae4160348230 100644 (file)
@@ -20,20 +20,23 @@ use bitcoin::hash_types::Txid;
 
 use bitcoin::secp256k1::{SecretKey,PublicKey};
 
-use ln::PaymentPreimage;
-use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment};
-use ln::chan_utils;
-use ln::msgs::DecodeError;
-use chain::chaininterface::{FeeEstimator, ConfirmationTarget, MIN_RELAY_FEE_SAT_PER_1000_WEIGHT};
-use chain::keysinterface::Sign;
-use chain::onchaintx::OnchainTxHandler;
-use util::byte_utils;
-use util::logger::Logger;
-use util::ser::{Readable, Writer, Writeable};
-
-use io;
-use prelude::*;
+use crate::ln::PaymentPreimage;
+use crate::ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment};
+use crate::ln::chan_utils;
+use crate::ln::msgs::DecodeError;
+use crate::chain::chaininterface::{FeeEstimator, ConfirmationTarget, MIN_RELAY_FEE_SAT_PER_1000_WEIGHT};
+use crate::chain::keysinterface::WriteableEcdsaChannelSigner;
+#[cfg(anchors)]
+use crate::chain::onchaintx::ExternalHTLCClaim;
+use crate::chain::onchaintx::OnchainTxHandler;
+use crate::util::logger::Logger;
+use crate::util::ser::{Readable, Writer, Writeable};
+
+use crate::io;
+use crate::prelude::*;
 use core::cmp;
+#[cfg(anchors)]
+use core::convert::TryInto;
 use core::mem;
 use core::ops::Deref;
 use bitcoin::{PackedLockTime, Sequence, Witness};
@@ -200,11 +203,11 @@ impl CounterpartyOfferedHTLCOutput {
 
 impl_writeable_tlv_based!(CounterpartyOfferedHTLCOutput, {
        (0, per_commitment_point, required),
-       (1, opt_anchors, option),
        (2, counterparty_delayed_payment_base_key, required),
        (4, counterparty_htlc_base_key, required),
        (6, preimage, required),
        (8, htlc, required),
+       (10, opt_anchors, option),
 });
 
 /// A struct to describe a HTLC output on a counterparty commitment transaction.
@@ -238,10 +241,10 @@ impl CounterpartyReceivedHTLCOutput {
 
 impl_writeable_tlv_based!(CounterpartyReceivedHTLCOutput, {
        (0, per_commitment_point, required),
-       (1, opt_anchors, option),
        (2, counterparty_delayed_payment_base_key, required),
        (4, counterparty_htlc_base_key, required),
        (6, htlc, required),
+       (8, opt_anchors, option),
 });
 
 /// A struct to describe a HTLC output on holder commitment transaction.
@@ -251,33 +254,41 @@ impl_writeable_tlv_based!(CounterpartyReceivedHTLCOutput, {
 #[derive(Clone, PartialEq, Eq)]
 pub(crate) struct HolderHTLCOutput {
        preimage: Option<PaymentPreimage>,
-       amount: u64,
+       amount_msat: u64,
        /// Defaults to 0 for HTLC-Success transactions, which have no expiry
        cltv_expiry: u32,
+       opt_anchors: Option<()>,
 }
 
 impl HolderHTLCOutput {
-       pub(crate) fn build_offered(amount: u64, cltv_expiry: u32) -> Self {
+       pub(crate) fn build_offered(amount_msat: u64, cltv_expiry: u32, opt_anchors: bool) -> Self {
                HolderHTLCOutput {
                        preimage: None,
-                       amount,
+                       amount_msat,
                        cltv_expiry,
+                       opt_anchors: if opt_anchors { Some(()) } else { None } ,
                }
        }
 
-       pub(crate) fn build_accepted(preimage: PaymentPreimage, amount: u64) -> Self {
+       pub(crate) fn build_accepted(preimage: PaymentPreimage, amount_msat: u64, opt_anchors: bool) -> Self {
                HolderHTLCOutput {
                        preimage: Some(preimage),
-                       amount,
+                       amount_msat,
                        cltv_expiry: 0,
+                       opt_anchors: if opt_anchors { Some(()) } else { None } ,
                }
        }
+
+       fn opt_anchors(&self) -> bool {
+               self.opt_anchors.is_some()
+       }
 }
 
 impl_writeable_tlv_based!(HolderHTLCOutput, {
-       (0, amount, required),
+       (0, amount_msat, required),
        (2, cltv_expiry, required),
-       (4, preimage, option)
+       (4, preimage, option),
+       (6, opt_anchors, option)
 });
 
 /// A struct to describe the channel output on the funding transaction.
@@ -307,7 +318,7 @@ impl HolderFundingOutput {
 
 impl_writeable_tlv_based!(HolderFundingOutput, {
        (0, funding_redeemscript, required),
-       (1, opt_anchors, option),
+       (2, opt_anchors, option),
        (3, funding_amount, option),
 });
 
@@ -332,10 +343,10 @@ impl PackageSolvingData {
                        PackageSolvingData::RevokedHTLCOutput(ref outp) => outp.amount,
                        PackageSolvingData::CounterpartyOfferedHTLCOutput(ref outp) => outp.htlc.amount_msat / 1000,
                        PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => outp.htlc.amount_msat / 1000,
-                       // Note: Currently, amounts of holder outputs spending witnesses aren't used
-                       // as we can't malleate spending package to increase their feerate. This
-                       // should change with the remaining anchor output patchset.
-                       PackageSolvingData::HolderHTLCOutput(..) => unreachable!(),
+                       PackageSolvingData::HolderHTLCOutput(ref outp) => {
+                               debug_assert!(outp.opt_anchors());
+                               outp.amount_msat / 1000
+                       },
                        PackageSolvingData::HolderFundingOutput(ref outp) => {
                                debug_assert!(outp.opt_anchors());
                                outp.funding_amount.unwrap()
@@ -344,18 +355,23 @@ impl PackageSolvingData {
                amt
        }
        fn weight(&self) -> usize {
-               let weight = match self {
-                       PackageSolvingData::RevokedOutput(ref outp) => { outp.weight as usize },
-                       PackageSolvingData::RevokedHTLCOutput(ref outp) => { outp.weight as usize },
-                       PackageSolvingData::CounterpartyOfferedHTLCOutput(ref outp) => { weight_offered_htlc(outp.opt_anchors()) as usize },
-                       PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => { weight_received_htlc(outp.opt_anchors()) as usize },
-                       // Note: Currently, weights of holder outputs spending witnesses aren't used
-                       // as we can't malleate spending package to increase their feerate. This
-                       // should change with the remaining anchor output patchset.
-                       PackageSolvingData::HolderHTLCOutput(..) => { unreachable!() },
-                       PackageSolvingData::HolderFundingOutput(..) => { unreachable!() },
-               };
-               weight
+               match self {
+                       PackageSolvingData::RevokedOutput(ref outp) => outp.weight as usize,
+                       PackageSolvingData::RevokedHTLCOutput(ref outp) => outp.weight as usize,
+                       PackageSolvingData::CounterpartyOfferedHTLCOutput(ref outp) => weight_offered_htlc(outp.opt_anchors()) as usize,
+                       PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => weight_received_htlc(outp.opt_anchors()) as usize,
+                       PackageSolvingData::HolderHTLCOutput(ref outp) => {
+                               debug_assert!(outp.opt_anchors());
+                               if outp.preimage.is_none() {
+                                       weight_offered_htlc(true) as usize
+                               } else {
+                                       weight_received_htlc(true) as usize
+                               }
+                       },
+                       // Since HolderFundingOutput maps to an untractable package that is already signed, its
+                       // weight can be determined from the transaction itself.
+                       PackageSolvingData::HolderFundingOutput(..) => unreachable!(),
+               }
        }
        fn is_compatible(&self, input: &PackageSolvingData) -> bool {
                match self {
@@ -376,85 +392,90 @@ impl PackageSolvingData {
                        _ => { mem::discriminant(self) == mem::discriminant(&input) }
                }
        }
-       fn finalize_input<Signer: Sign>(&self, bumped_tx: &mut Transaction, i: usize, onchain_handler: &mut OnchainTxHandler<Signer>) -> bool {
+       fn finalize_input<Signer: WriteableEcdsaChannelSigner>(&self, bumped_tx: &mut Transaction, i: usize, onchain_handler: &mut OnchainTxHandler<Signer>) -> bool {
                match self {
                        PackageSolvingData::RevokedOutput(ref outp) => {
-                               if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
-                                       let witness_script = chan_utils::get_revokeable_redeemscript(&chan_keys.revocation_key, outp.on_counterparty_tx_csv, &chan_keys.broadcaster_delayed_payment_key);
-                                       //TODO: should we panic on signer failure ?
-                                       if let Ok(sig) = onchain_handler.signer.sign_justice_revoked_output(&bumped_tx, i, outp.amount, &outp.per_commitment_key, &onchain_handler.secp_ctx) {
-                                               let mut ser_sig = sig.serialize_der().to_vec();
-                                               ser_sig.push(EcdsaSighashType::All as u8);
-                                               bumped_tx.input[i].witness.push(ser_sig);
-                                               bumped_tx.input[i].witness.push(vec!(1));
-                                               bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
-                                       } else { return false; }
-                               }
+                               let chan_keys = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint);
+                               let witness_script = chan_utils::get_revokeable_redeemscript(&chan_keys.revocation_key, outp.on_counterparty_tx_csv, &chan_keys.broadcaster_delayed_payment_key);
+                               //TODO: should we panic on signer failure ?
+                               if let Ok(sig) = onchain_handler.signer.sign_justice_revoked_output(&bumped_tx, i, outp.amount, &outp.per_commitment_key, &onchain_handler.secp_ctx) {
+                                       let mut ser_sig = sig.serialize_der().to_vec();
+                                       ser_sig.push(EcdsaSighashType::All as u8);
+                                       bumped_tx.input[i].witness.push(ser_sig);
+                                       bumped_tx.input[i].witness.push(vec!(1));
+                                       bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
+                               } else { return false; }
                        },
                        PackageSolvingData::RevokedHTLCOutput(ref outp) => {
-                               if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
-                                       let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, onchain_handler.opt_anchors(), &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
-                                       //TODO: should we panic on signer failure ?
-                                       if let Ok(sig) = onchain_handler.signer.sign_justice_revoked_htlc(&bumped_tx, i, outp.amount, &outp.per_commitment_key, &outp.htlc, &onchain_handler.secp_ctx) {
-                                               let mut ser_sig = sig.serialize_der().to_vec();
-                                               ser_sig.push(EcdsaSighashType::All as u8);
-                                               bumped_tx.input[i].witness.push(ser_sig);
-                                               bumped_tx.input[i].witness.push(chan_keys.revocation_key.clone().serialize().to_vec());
-                                               bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
-                                       } else { return false; }
-                               }
+                               let chan_keys = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint);
+                               let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, onchain_handler.opt_anchors(), &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
+                               //TODO: should we panic on signer failure ?
+                               if let Ok(sig) = onchain_handler.signer.sign_justice_revoked_htlc(&bumped_tx, i, outp.amount, &outp.per_commitment_key, &outp.htlc, &onchain_handler.secp_ctx) {
+                                       let mut ser_sig = sig.serialize_der().to_vec();
+                                       ser_sig.push(EcdsaSighashType::All as u8);
+                                       bumped_tx.input[i].witness.push(ser_sig);
+                                       bumped_tx.input[i].witness.push(chan_keys.revocation_key.clone().serialize().to_vec());
+                                       bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
+                               } else { return false; }
                        },
                        PackageSolvingData::CounterpartyOfferedHTLCOutput(ref outp) => {
-                               if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
-                                       let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, onchain_handler.opt_anchors(), &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
-
-                                       if let Ok(sig) = onchain_handler.signer.sign_counterparty_htlc_transaction(&bumped_tx, i, &outp.htlc.amount_msat / 1000, &outp.per_commitment_point, &outp.htlc, &onchain_handler.secp_ctx) {
-                                               let mut ser_sig = sig.serialize_der().to_vec();
-                                               ser_sig.push(EcdsaSighashType::All as u8);
-                                               bumped_tx.input[i].witness.push(ser_sig);
-                                               bumped_tx.input[i].witness.push(outp.preimage.0.to_vec());
-                                               bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
-                                       }
+                               let chan_keys = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint);
+                               let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, onchain_handler.opt_anchors(), &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
+
+                               if let Ok(sig) = onchain_handler.signer.sign_counterparty_htlc_transaction(&bumped_tx, i, &outp.htlc.amount_msat / 1000, &outp.per_commitment_point, &outp.htlc, &onchain_handler.secp_ctx) {
+                                       let mut ser_sig = sig.serialize_der().to_vec();
+                                       ser_sig.push(EcdsaSighashType::All as u8);
+                                       bumped_tx.input[i].witness.push(ser_sig);
+                                       bumped_tx.input[i].witness.push(outp.preimage.0.to_vec());
+                                       bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
                                }
                        },
                        PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => {
-                               if let Ok(chan_keys) = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint) {
-                                       let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, onchain_handler.opt_anchors(), &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
-
-                                       bumped_tx.lock_time = PackedLockTime(outp.htlc.cltv_expiry); // Right now we don't aggregate time-locked transaction, if we do we should set lock_time before to avoid breaking hash computation
-                                       if let Ok(sig) = onchain_handler.signer.sign_counterparty_htlc_transaction(&bumped_tx, i, &outp.htlc.amount_msat / 1000, &outp.per_commitment_point, &outp.htlc, &onchain_handler.secp_ctx) {
-                                               let mut ser_sig = sig.serialize_der().to_vec();
-                                               ser_sig.push(EcdsaSighashType::All as u8);
-                                               bumped_tx.input[i].witness.push(ser_sig);
-                                               // Due to BIP146 (MINIMALIF) this must be a zero-length element to relay.
-                                               bumped_tx.input[i].witness.push(vec![]);
-                                               bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
-                                       }
+                               let chan_keys = TxCreationKeys::derive_new(&onchain_handler.secp_ctx, &outp.per_commitment_point, &outp.counterparty_delayed_payment_base_key, &outp.counterparty_htlc_base_key, &onchain_handler.signer.pubkeys().revocation_basepoint, &onchain_handler.signer.pubkeys().htlc_basepoint);
+                               let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&outp.htlc, onchain_handler.opt_anchors(), &chan_keys.broadcaster_htlc_key, &chan_keys.countersignatory_htlc_key, &chan_keys.revocation_key);
+
+                               if let Ok(sig) = onchain_handler.signer.sign_counterparty_htlc_transaction(&bumped_tx, i, &outp.htlc.amount_msat / 1000, &outp.per_commitment_point, &outp.htlc, &onchain_handler.secp_ctx) {
+                                       let mut ser_sig = sig.serialize_der().to_vec();
+                                       ser_sig.push(EcdsaSighashType::All as u8);
+                                       bumped_tx.input[i].witness.push(ser_sig);
+                                       // Due to BIP146 (MINIMALIF) this must be a zero-length element to relay.
+                                       bumped_tx.input[i].witness.push(vec![]);
+                                       bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
                                }
                        },
                        _ => { panic!("API Error!"); }
                }
                true
        }
-       fn get_finalized_tx<Signer: Sign>(&self, outpoint: &BitcoinOutPoint, onchain_handler: &mut OnchainTxHandler<Signer>) -> Option<Transaction> {
+       fn get_finalized_tx<Signer: WriteableEcdsaChannelSigner>(&self, outpoint: &BitcoinOutPoint, onchain_handler: &mut OnchainTxHandler<Signer>) -> Option<Transaction> {
                match self {
-                       PackageSolvingData::HolderHTLCOutput(ref outp) => { return onchain_handler.get_fully_signed_htlc_tx(outpoint, &outp.preimage); }
-                       PackageSolvingData::HolderFundingOutput(ref outp) => { return Some(onchain_handler.get_fully_signed_holder_tx(&outp.funding_redeemscript)); }
+                       PackageSolvingData::HolderHTLCOutput(ref outp) => {
+                               debug_assert!(!outp.opt_anchors());
+                               return onchain_handler.get_fully_signed_htlc_tx(outpoint, &outp.preimage);
+                       }
+                       PackageSolvingData::HolderFundingOutput(ref outp) => {
+                               return Some(onchain_handler.get_fully_signed_holder_tx(&outp.funding_redeemscript));
+                       }
                        _ => { panic!("API Error!"); }
                }
        }
-       fn absolute_tx_timelock(&self, output_conf_height: u32) -> u32 {
-               // Get the absolute timelock at which this output can be spent given the height at which
-               // this output was confirmed. We use `output_conf_height + 1` as a safe default as we can
-               // be confirmed in the next block and transactions with time lock `current_height + 1`
-               // always propagate.
+       fn absolute_tx_timelock(&self, current_height: u32) -> u32 {
+               // We use `current_height + 1` as our default locktime to discourage fee sniping and because
+               // transactions with it always propagate.
                let absolute_timelock = match self {
-                       PackageSolvingData::RevokedOutput(_) => output_conf_height + 1,
-                       PackageSolvingData::RevokedHTLCOutput(_) => output_conf_height + 1,
-                       PackageSolvingData::CounterpartyOfferedHTLCOutput(_) => output_conf_height + 1,
-                       PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => cmp::max(outp.htlc.cltv_expiry, output_conf_height + 1),
-                       PackageSolvingData::HolderHTLCOutput(ref outp) => cmp::max(outp.cltv_expiry, output_conf_height + 1),
-                       PackageSolvingData::HolderFundingOutput(_) => output_conf_height + 1,
+                       PackageSolvingData::RevokedOutput(_) => current_height + 1,
+                       PackageSolvingData::RevokedHTLCOutput(_) => current_height + 1,
+                       PackageSolvingData::CounterpartyOfferedHTLCOutput(_) => current_height + 1,
+                       PackageSolvingData::CounterpartyReceivedHTLCOutput(ref outp) => cmp::max(outp.htlc.cltv_expiry, current_height + 1),
+                       // HTLC timeout/success transactions rely on a fixed timelock due to the counterparty's
+                       // signature.
+                       PackageSolvingData::HolderHTLCOutput(ref outp) => {
+                               if outp.preimage.is_some() {
+                                       debug_assert_eq!(outp.cltv_expiry, 0);
+                               }
+                               outp.cltv_expiry
+                       },
+                       PackageSolvingData::HolderFundingOutput(_) => current_height + 1,
                };
                absolute_timelock
        }
@@ -548,6 +569,9 @@ impl PackageTemplate {
        pub(crate) fn outpoints(&self) -> Vec<&BitcoinOutPoint> {
                self.inputs.iter().map(|(o, _)| o).collect()
        }
+       pub(crate) fn inputs(&self) -> impl ExactSizeIterator<Item = &PackageSolvingData> {
+               self.inputs.iter().map(|(_, i)| i)
+       }
        pub(crate) fn split_package(&mut self, split_outp: &BitcoinOutPoint) -> Option<PackageTemplate> {
                match self.malleability {
                        PackageMalleability::Malleable => {
@@ -611,16 +635,43 @@ impl PackageTemplate {
        }
        /// Gets the amount of all outptus being spent by this package, only valid for malleable
        /// packages.
-       fn package_amount(&self) -> u64 {
+       pub(crate) fn package_amount(&self) -> u64 {
                let mut amounts = 0;
                for (_, outp) in self.inputs.iter() {
                        amounts += outp.amount();
                }
                amounts
        }
-       pub(crate) fn package_timelock(&self) -> u32 {
-               self.inputs.iter().map(|(_, outp)| outp.absolute_tx_timelock(self.height_original))
-                       .max().expect("There must always be at least one output to spend in a PackageTemplate")
+       pub(crate) fn package_locktime(&self, current_height: u32) -> u32 {
+               let locktime = self.inputs.iter().map(|(_, outp)| outp.absolute_tx_timelock(current_height))
+                       .max().expect("There must always be at least one output to spend in a PackageTemplate");
+
+               // If we ever try to aggregate a `HolderHTLCOutput`s with another output type, we'll likely
+               // end up with an incorrect transaction locktime since the counterparty has included it in
+               // its HTLC signature. This should never happen unless we decide to aggregate outputs across
+               // different channel commitments.
+               #[cfg(debug_assertions)] {
+                       if self.inputs.iter().any(|(_, outp)|
+                               if let PackageSolvingData::HolderHTLCOutput(outp) = outp {
+                                       outp.preimage.is_some()
+                               } else {
+                                       false
+                               }
+                       ) {
+                               debug_assert_eq!(locktime, 0);
+                       };
+                       for timeout_htlc_expiry in self.inputs.iter().filter_map(|(_, outp)|
+                               if let PackageSolvingData::HolderHTLCOutput(outp) = outp {
+                                       if outp.preimage.is_none() {
+                                               Some(outp.cltv_expiry)
+                                       } else { None }
+                               } else { None }
+                       ) {
+                               debug_assert_eq!(locktime, timeout_htlc_expiry);
+                       }
+               }
+
+               locktime
        }
        pub(crate) fn package_weight(&self, destination_script: &Script) -> usize {
                let mut inputs_weight = 0;
@@ -636,47 +687,66 @@ impl PackageTemplate {
                let output_weight = (8 + 1 + destination_script.len()) * WITNESS_SCALE_FACTOR;
                inputs_weight + witnesses_weight + transaction_weight + output_weight
        }
-       pub(crate) fn finalize_package<L: Deref, Signer: Sign>(&self, onchain_handler: &mut OnchainTxHandler<Signer>, value: u64, destination_script: Script, logger: &L) -> Option<Transaction>
-               where L::Target: Logger,
-       {
-               match self.malleability {
-                       PackageMalleability::Malleable => {
-                               let mut bumped_tx = Transaction {
-                                       version: 2,
-                                       lock_time: PackedLockTime::ZERO,
-                                       input: vec![],
-                                       output: vec![TxOut {
-                                               script_pubkey: destination_script,
-                                               value,
-                                       }],
-                               };
-                               for (outpoint, _) in self.inputs.iter() {
-                                       bumped_tx.input.push(TxIn {
-                                               previous_output: *outpoint,
-                                               script_sig: Script::new(),
-                                               sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
-                                               witness: Witness::new(),
+       #[cfg(anchors)]
+       pub(crate) fn construct_malleable_package_with_external_funding<Signer: WriteableEcdsaChannelSigner>(
+               &self, onchain_handler: &mut OnchainTxHandler<Signer>,
+       ) -> Option<Vec<ExternalHTLCClaim>> {
+               debug_assert!(self.requires_external_funding());
+               let mut htlcs: Option<Vec<ExternalHTLCClaim>> = None;
+               for (previous_output, input) in &self.inputs {
+                       match input {
+                               PackageSolvingData::HolderHTLCOutput(ref outp) => {
+                                       debug_assert!(outp.opt_anchors());
+                                       onchain_handler.generate_external_htlc_claim(&previous_output, &outp.preimage).map(|htlc| {
+                                               htlcs.get_or_insert_with(|| Vec::with_capacity(self.inputs.len())).push(htlc);
                                        });
                                }
-                               for (i, (outpoint, out)) in self.inputs.iter().enumerate() {
-                                       log_debug!(logger, "Adding claiming input for outpoint {}:{}", outpoint.txid, outpoint.vout);
-                                       if !out.finalize_input(&mut bumped_tx, i, onchain_handler) { return None; }
-                               }
-                               log_debug!(logger, "Finalized transaction {} ready to broadcast", bumped_tx.txid());
-                               return Some(bumped_tx);
-                       },
-                       PackageMalleability::Untractable => {
-                               debug_assert_eq!(value, 0, "value is ignored for non-malleable packages, should be zero to ensure callsites are correct");
-                               if let Some((outpoint, outp)) = self.inputs.first() {
-                                       if let Some(final_tx) = outp.get_finalized_tx(outpoint, onchain_handler) {
-                                               log_debug!(logger, "Adding claiming input for outpoint {}:{}", outpoint.txid, outpoint.vout);
-                                               log_debug!(logger, "Finalized transaction {} ready to broadcast", final_tx.txid());
-                                               return Some(final_tx);
-                                       }
-                                       return None;
-                               } else { panic!("API Error: Package must not be inputs empty"); }
-                       },
+                               _ => debug_assert!(false, "Expected HolderHTLCOutputs to not be aggregated with other input types"),
+                       }
+               }
+               htlcs
+       }
+       pub(crate) fn finalize_malleable_package<L: Deref, Signer: WriteableEcdsaChannelSigner>(
+               &self, current_height: u32, onchain_handler: &mut OnchainTxHandler<Signer>, value: u64,
+               destination_script: Script, logger: &L
+       ) -> Option<Transaction> where L::Target: Logger {
+               debug_assert!(self.is_malleable());
+               let mut bumped_tx = Transaction {
+                       version: 2,
+                       lock_time: PackedLockTime(self.package_locktime(current_height)),
+                       input: vec![],
+                       output: vec![TxOut {
+                               script_pubkey: destination_script,
+                               value,
+                       }],
+               };
+               for (outpoint, _) in self.inputs.iter() {
+                       bumped_tx.input.push(TxIn {
+                               previous_output: *outpoint,
+                               script_sig: Script::new(),
+                               sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
+                               witness: Witness::new(),
+                       });
+               }
+               for (i, (outpoint, out)) in self.inputs.iter().enumerate() {
+                       log_debug!(logger, "Adding claiming input for outpoint {}:{}", outpoint.txid, outpoint.vout);
+                       if !out.finalize_input(&mut bumped_tx, i, onchain_handler) { return None; }
                }
+               log_debug!(logger, "Finalized transaction {} ready to broadcast", bumped_tx.txid());
+               Some(bumped_tx)
+       }
+       pub(crate) fn finalize_untractable_package<L: Deref, Signer: WriteableEcdsaChannelSigner>(
+               &self, onchain_handler: &mut OnchainTxHandler<Signer>, logger: &L,
+       ) -> Option<Transaction> where L::Target: Logger {
+               debug_assert!(!self.is_malleable());
+               if let Some((outpoint, outp)) = self.inputs.first() {
+                       if let Some(final_tx) = outp.get_finalized_tx(outpoint, onchain_handler) {
+                               log_debug!(logger, "Adding claiming input for outpoint {}:{}", outpoint.txid, outpoint.vout);
+                               log_debug!(logger, "Finalized transaction {} ready to broadcast", final_tx.txid());
+                               return Some(final_tx);
+                       }
+                       return None;
+               } else { panic!("API Error: Package must not be inputs empty"); }
        }
        /// In LN, output claimed are time-sensitive, which means we have to spend them before reaching some timelock expiration. At in-channel
        /// output detection, we generate a first version of a claim tx and associate to it a height timer. A height timer is an absolute block
@@ -714,14 +784,50 @@ impl PackageTemplate {
                }
                None
        }
+
+       #[cfg(anchors)]
+       /// Computes a feerate based on the given confirmation target. If a previous feerate was used,
+       /// and the new feerate is below it, we'll use a 25% increase of the previous feerate instead of
+       /// the new one.
+       pub(crate) fn compute_package_feerate<F: Deref>(
+               &self, fee_estimator: &LowerBoundedFeeEstimator<F>, conf_target: ConfirmationTarget,
+       ) -> u32 where F::Target: FeeEstimator {
+               let feerate_estimate = fee_estimator.bounded_sat_per_1000_weight(conf_target);
+               if self.feerate_previous != 0 {
+                       // If old feerate inferior to actual one given back by Fee Estimator, use it to compute new fee...
+                       if feerate_estimate as u64 > self.feerate_previous {
+                               feerate_estimate
+                       } else {
+                               // ...else just increase the previous feerate by 25% (because that's a nice number)
+                               (self.feerate_previous + (self.feerate_previous / 4)).try_into().unwrap_or(u32::max_value())
+                       }
+               } else {
+                       feerate_estimate
+               }
+       }
+
+       /// Determines whether a package contains an input which must have additional external inputs
+       /// attached to help the spending transaction reach confirmation.
+       pub(crate) fn requires_external_funding(&self) -> bool {
+               self.inputs.iter().find(|input| match input.1 {
+                       PackageSolvingData::HolderFundingOutput(ref outp) => outp.opt_anchors(),
+                       PackageSolvingData::HolderHTLCOutput(ref outp) => outp.opt_anchors(),
+                       _ => false,
+               }).is_some()
+       }
+
        pub (crate) fn build_package(txid: Txid, vout: u32, input_solving_data: PackageSolvingData, soonest_conf_deadline: u32, aggregable: bool, height_original: u32) -> Self {
                let malleability = match input_solving_data {
-                       PackageSolvingData::RevokedOutput(..) => { PackageMalleability::Malleable },
-                       PackageSolvingData::RevokedHTLCOutput(..) => { PackageMalleability::Malleable },
-                       PackageSolvingData::CounterpartyOfferedHTLCOutput(..) => { PackageMalleability::Malleable },
-                       PackageSolvingData::CounterpartyReceivedHTLCOutput(..) => { PackageMalleability::Malleable },
-                       PackageSolvingData::HolderHTLCOutput(..) => { PackageMalleability::Untractable },
-                       PackageSolvingData::HolderFundingOutput(..) => { PackageMalleability::Untractable },
+                       PackageSolvingData::RevokedOutput(..) => PackageMalleability::Malleable,
+                       PackageSolvingData::RevokedHTLCOutput(..) => PackageMalleability::Malleable,
+                       PackageSolvingData::CounterpartyOfferedHTLCOutput(..) => PackageMalleability::Malleable,
+                       PackageSolvingData::CounterpartyReceivedHTLCOutput(..) => PackageMalleability::Malleable,
+                       PackageSolvingData::HolderHTLCOutput(ref outp) => if outp.opt_anchors() {
+                               PackageMalleability::Malleable
+                       } else {
+                               PackageMalleability::Untractable
+                       },
+                       PackageSolvingData::HolderFundingOutput(..) => PackageMalleability::Untractable,
                };
                let mut inputs = Vec::with_capacity(1);
                inputs.push((BitcoinOutPoint { txid, vout }, input_solving_data));
@@ -739,7 +845,7 @@ impl PackageTemplate {
 
 impl Writeable for PackageTemplate {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
-               writer.write_all(&byte_utils::be64_to_array(self.inputs.len() as u64))?;
+               writer.write_all(&(self.inputs.len() as u64).to_be_bytes())?;
                for (ref outpoint, ref rev_outp) in self.inputs.iter() {
                        outpoint.write(writer)?;
                        rev_outp.write(writer)?;
@@ -769,7 +875,11 @@ impl Readable for PackageTemplate {
                                PackageSolvingData::RevokedHTLCOutput(..) => { (PackageMalleability::Malleable, true) },
                                PackageSolvingData::CounterpartyOfferedHTLCOutput(..) => { (PackageMalleability::Malleable, true) },
                                PackageSolvingData::CounterpartyReceivedHTLCOutput(..) => { (PackageMalleability::Malleable, false) },
-                               PackageSolvingData::HolderHTLCOutput(..) => { (PackageMalleability::Untractable, false) },
+                               PackageSolvingData::HolderHTLCOutput(ref outp) => if outp.opt_anchors() {
+                                       (PackageMalleability::Malleable, outp.preimage.is_some())
+                               } else {
+                                       (PackageMalleability::Untractable, false)
+                               },
                                PackageSolvingData::HolderFundingOutput(..) => { (PackageMalleability::Untractable, false) },
                        }
                } else { return Err(DecodeError::InvalidValue); };
@@ -876,10 +986,10 @@ fn feerate_bump<F: Deref, L: Deref>(predicted_weight: usize, input_amounts: u64,
 
 #[cfg(test)]
 mod tests {
-       use chain::package::{CounterpartyOfferedHTLCOutput, CounterpartyReceivedHTLCOutput, HolderHTLCOutput, PackageTemplate, PackageSolvingData, RevokedOutput, WEIGHT_REVOKED_OUTPUT, weight_offered_htlc, weight_received_htlc};
-       use chain::Txid;
-       use ln::chan_utils::HTLCOutputInCommitment;
-       use ln::{PaymentPreimage, PaymentHash};
+       use crate::chain::package::{CounterpartyOfferedHTLCOutput, CounterpartyReceivedHTLCOutput, HolderHTLCOutput, PackageTemplate, PackageSolvingData, RevokedOutput, WEIGHT_REVOKED_OUTPUT, weight_offered_htlc, weight_received_htlc};
+       use crate::chain::Txid;
+       use crate::ln::chan_utils::HTLCOutputInCommitment;
+       use crate::ln::{PaymentPreimage, PaymentHash};
 
        use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
        use bitcoin::blockdata::script::Script;
@@ -929,7 +1039,7 @@ mod tests {
                () => {
                        {
                                let preimage = PaymentPreimage([2;32]);
-                               PackageSolvingData::HolderHTLCOutput(HolderHTLCOutput::build_accepted(preimage, 0))
+                               PackageSolvingData::HolderHTLCOutput(HolderHTLCOutput::build_accepted(preimage, 0, false))
                        }
                }
        }