Batch-sign local HTLC txn with a well-doc'd API, returning sigs
[rust-lightning] / lightning / src / ln / onchaintx.rs
index 02dc2ebc50b69644db51374219def8137151d3ec..6b5da67c1a526de38c7905694f4dde9063278b34 100644 (file)
@@ -10,19 +10,20 @@ use bitcoin::util::bip143;
 
 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
 
-use secp256k1::Secp256k1;
+use secp256k1::{Secp256k1, Signature};
 use secp256k1;
 
 use ln::msgs::DecodeError;
 use ln::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER, InputMaterial, ClaimRequest};
-use ln::chan_utils::HTLCType;
+use ln::channelmanager::PaymentPreimage;
+use ln::chan_utils::{HTLCType, LocalCommitmentTransaction};
 use chain::chaininterface::{FeeEstimator, BroadcasterInterface, ConfirmationTarget, MIN_RELAY_FEE_SAT_PER_1000_WEIGHT};
 use chain::keysinterface::ChannelKeys;
 use util::logger::Logger;
 use util::ser::{ReadableArgs, Readable, Writer, Writeable};
 use util::byte_utils;
 
-use std::collections::{HashMap, hash_map, HashSet};
+use std::collections::{HashMap, hash_map};
 use std::sync::Arc;
 use std::cmp;
 use std::ops::Deref;
@@ -52,7 +53,7 @@ enum OnchainEvent {
 pub struct ClaimTxBumpMaterial {
        // At every block tick, used to check if pending claiming tx is taking too
        // much time for confirmation and we need to bump it.
-       height_timer: u32,
+       height_timer: Option<u32>,
        // Tracked in case of reorg to wipe out now-superflous bump material
        feerate_previous: u64,
        // Soonest timelocks among set of outpoints claimed, used to compute
@@ -64,7 +65,7 @@ pub struct ClaimTxBumpMaterial {
 
 impl Writeable for ClaimTxBumpMaterial  {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
-               writer.write_all(&byte_utils::be32_to_array(self.height_timer))?;
+               self.height_timer.write(writer)?;
                writer.write_all(&byte_utils::be64_to_array(self.feerate_previous))?;
                writer.write_all(&byte_utils::be32_to_array(self.soonest_timelock))?;
                writer.write_all(&byte_utils::be64_to_array(self.per_input_material.len() as u64))?;
@@ -136,11 +137,64 @@ macro_rules! subtract_high_prio_fee {
        }
 }
 
+impl Readable for Option<Vec<Option<(usize, Signature)>>> {
+       fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+               match Readable::read(reader)? {
+                       0u8 => Ok(None),
+                       1u8 => {
+                               let vlen: u64 = Readable::read(reader)?;
+                               let mut ret = Vec::with_capacity(cmp::min(vlen as usize, MAX_ALLOC_SIZE / ::std::mem::size_of::<Option<(usize, Signature)>>()));
+                               for _ in 0..vlen {
+                                       ret.push(match Readable::read(reader)? {
+                                               0u8 => None,
+                                               1u8 => Some((<u64 as Readable>::read(reader)? as usize, Readable::read(reader)?)),
+                                               _ => return Err(DecodeError::InvalidValue)
+                                       });
+                               }
+                               Ok(Some(ret))
+                       },
+                       _ => Err(DecodeError::InvalidValue),
+               }
+       }
+}
+
+impl Writeable for Option<Vec<Option<(usize, Signature)>>> {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+               match self {
+                       &Some(ref vec) => {
+                               1u8.write(writer)?;
+                               (vec.len() as u64).write(writer)?;
+                               for opt in vec.iter() {
+                                       match opt {
+                                               &Some((ref idx, ref sig)) => {
+                                                       1u8.write(writer)?;
+                                                       (*idx as u64).write(writer)?;
+                                                       sig.write(writer)?;
+                                               },
+                                               &None => 0u8.write(writer)?,
+                                       }
+                               }
+                       },
+                       &None => 0u8.write(writer)?,
+               }
+               Ok(())
+       }
+}
+
 
 /// OnchainTxHandler receives claiming requests, aggregates them if it's sound, broadcast and
 /// do RBF bumping if possible.
 pub struct OnchainTxHandler<ChanSigner: ChannelKeys> {
        destination_script: Script,
+       local_commitment: Option<LocalCommitmentTransaction>,
+       // local_htlc_sigs and prev_local_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 LocalCommitmentTransaction (including those which do not appear in
+       // the commitment transaction).
+       local_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,
+       prev_local_commitment: Option<LocalCommitmentTransaction>,
+       prev_local_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,
+       local_csv: u16,
 
        key_storage: ChanSigner,
 
@@ -180,6 +234,12 @@ pub struct OnchainTxHandler<ChanSigner: ChannelKeys> {
 impl<ChanSigner: ChannelKeys + Writeable> OnchainTxHandler<ChanSigner> {
        pub(crate) fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                self.destination_script.write(writer)?;
+               self.local_commitment.write(writer)?;
+               self.local_htlc_sigs.write(writer)?;
+               self.prev_local_commitment.write(writer)?;
+               self.prev_local_htlc_sigs.write(writer)?;
+
+               self.local_csv.write(writer)?;
 
                self.key_storage.write(writer)?;
 
@@ -222,6 +282,13 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
        fn read<R: ::std::io::Read>(reader: &mut R, logger: Arc<Logger>) -> Result<Self, DecodeError> {
                let destination_script = Readable::read(reader)?;
 
+               let local_commitment = Readable::read(reader)?;
+               let local_htlc_sigs = Readable::read(reader)?;
+               let prev_local_commitment = Readable::read(reader)?;
+               let prev_local_htlc_sigs = Readable::read(reader)?;
+
+               let local_csv = Readable::read(reader)?;
+
                let key_storage = Readable::read(reader)?;
 
                let pending_claim_requests_len: u64 = Readable::read(reader)?;
@@ -269,6 +336,11 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 
                Ok(OnchainTxHandler {
                        destination_script,
+                       local_commitment,
+                       local_htlc_sigs,
+                       prev_local_commitment,
+                       prev_local_htlc_sigs,
+                       local_csv,
                        key_storage,
                        claimable_outpoints,
                        pending_claim_requests,
@@ -280,12 +352,17 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 }
 
 impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
-       pub(super) fn new(destination_script: Script, keys: ChanSigner, logger: Arc<Logger>) -> Self {
+       pub(super) fn new(destination_script: Script, keys: ChanSigner, local_csv: u16, logger: Arc<Logger>) -> Self {
 
                let key_storage = keys;
 
                OnchainTxHandler {
                        destination_script,
+                       local_commitment: None,
+                       local_htlc_sigs: None,
+                       prev_local_commitment: None,
+                       prev_local_htlc_sigs: None,
+                       local_csv,
                        key_storage,
                        pending_claim_requests: HashMap::new(),
                        claimable_outpoints: HashMap::new(),
@@ -342,7 +419,7 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 
        /// Lightning security model (i.e being able to redeem/timeout HTLC or penalize coutnerparty onchain) lays on the assumption of claim transactions getting confirmed before timelock expiration
        /// (CSV or CLTV following cases). In case of high-fee spikes, claim tx may stuck in the mempool, so you need to bump its feerate quickly using Replace-By-Fee or Child-Pay-For-Parent.
-       fn generate_claim_tx<F: Deref>(&self, height: u32, cached_claim_datas: &ClaimTxBumpMaterial, fee_estimator: F) -> Option<(u32, u64, Transaction)>
+       fn generate_claim_tx<F: Deref>(&mut self, height: u32, cached_claim_datas: &ClaimTxBumpMaterial, fee_estimator: F) -> Option<(Option<u32>, u64, Transaction)>
                where F::Target: FeeEstimator
        {
                if cached_claim_datas.per_input_material.len() == 0 { return None } // But don't prune pending claiming request yet, we may have to resurrect HTLCs
@@ -407,9 +484,10 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 
                // Compute new height timer to decide when we need to regenerate a new bumped version of the claim tx (if we
                // didn't receive confirmation of it before, or not enough reorg-safe depth on top of it).
-               let new_timer = Self::get_height_timer(height, cached_claim_datas.soonest_timelock);
+               let new_timer = Some(Self::get_height_timer(height, cached_claim_datas.soonest_timelock));
                let mut inputs_witnesses_weight = 0;
                let mut amt = 0;
+               let mut dynamic_fee = true;
                for per_outp_material in cached_claim_datas.per_input_material.values() {
                        match per_outp_material {
                                &InputMaterial::Revoked { ref witness_script, ref is_htlc, ref amount, .. } => {
@@ -420,72 +498,96 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
                                        inputs_witnesses_weight += Self::get_witnesses_weight(if preimage.is_some() { &[InputDescriptors::OfferedHTLC] } else { &[InputDescriptors::ReceivedHTLC] });
                                        amt += *amount;
                                },
-                               &InputMaterial::LocalHTLC { .. } => { return None; }
-                       }
-               }
-
-               let predicted_weight = bumped_tx.get_weight() + inputs_witnesses_weight;
-               let mut new_feerate;
-               // If old feerate is 0, first iteration of this claim, use normal fee calculation
-               if cached_claim_datas.feerate_previous != 0 {
-                       if let Some((new_fee, feerate)) = RBF_bump!(amt, cached_claim_datas.feerate_previous, fee_estimator, predicted_weight as u64) {
-                               // If new computed fee is superior at the whole claimable amount burn all in fees
-                               if new_fee > amt {
-                                       bumped_tx.output[0].value = 0;
-                               } else {
-                                       bumped_tx.output[0].value = amt - new_fee;
+                               &InputMaterial::LocalHTLC { .. } => {
+                                       dynamic_fee = false;
+                               },
+                               &InputMaterial::Funding { .. } => {
+                                       dynamic_fee = false;
                                }
-                               new_feerate = feerate;
-                       } else { return None; }
-               } else {
-                       if subtract_high_prio_fee!(self, fee_estimator, amt, predicted_weight, new_feerate) {
-                               bumped_tx.output[0].value = amt;
-                       } else { return None; }
+                       }
                }
-               assert!(new_feerate != 0);
-
-               for (i, (outp, per_outp_material)) in cached_claim_datas.per_input_material.iter().enumerate() {
-                       match per_outp_material {
-                               &InputMaterial::Revoked { ref witness_script, ref pubkey, ref key, ref is_htlc, ref amount } => {
-                                       let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
-                                       let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[i], &witness_script, *amount)[..]);
-                                       let sig = self.secp_ctx.sign(&sighash, &key);
-                                       bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
-                                       bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
-                                       if *is_htlc {
-                                               bumped_tx.input[i].witness.push(pubkey.unwrap().clone().serialize().to_vec());
+               if dynamic_fee {
+                       let predicted_weight = bumped_tx.get_weight() + inputs_witnesses_weight;
+                       let mut new_feerate;
+                       // If old feerate is 0, first iteration of this claim, use normal fee calculation
+                       if cached_claim_datas.feerate_previous != 0 {
+                               if let Some((new_fee, feerate)) = RBF_bump!(amt, cached_claim_datas.feerate_previous, fee_estimator, predicted_weight as u64) {
+                                       // If new computed fee is superior at the whole claimable amount burn all in fees
+                                       if new_fee > amt {
+                                               bumped_tx.output[0].value = 0;
                                        } else {
-                                               bumped_tx.input[i].witness.push(vec!(1));
+                                               bumped_tx.output[0].value = amt - new_fee;
                                        }
-                                       bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
-                                       log_trace!(self, "Going to broadcast Penalty Transaction {} claiming revoked {} output {} from {} with new feerate {}...", bumped_tx.txid(), if !is_htlc { "to_local" } else if HTLCType::scriptlen_to_htlctype(witness_script.len()) == Some(HTLCType::OfferedHTLC) { "offered" } else if HTLCType::scriptlen_to_htlctype(witness_script.len()) == Some(HTLCType::AcceptedHTLC) { "received" } else { "" }, outp.vout, outp.txid, new_feerate);
-                               },
-                               &InputMaterial::RemoteHTLC { ref witness_script, ref key, ref preimage, ref amount, ref locktime } => {
-                                       if !preimage.is_some() { bumped_tx.lock_time = *locktime }; // Right now we don't aggregate time-locked transaction, if we do we should set lock_time before to avoid breaking hash computation
-                                       let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
-                                       let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[i], &witness_script, *amount)[..]);
-                                       let sig = self.secp_ctx.sign(&sighash, &key);
-                                       bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
-                                       bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
-                                       if let &Some(preimage) = preimage {
-                                               bumped_tx.input[i].witness.push(preimage.clone().0.to_vec());
-                                       } else {
-                                               bumped_tx.input[i].witness.push(vec![0]);
+                                       new_feerate = feerate;
+                               } else { return None; }
+                       } else {
+                               if subtract_high_prio_fee!(self, fee_estimator, amt, predicted_weight, new_feerate) {
+                                       bumped_tx.output[0].value = amt;
+                               } else { return None; }
+                       }
+                       assert!(new_feerate != 0);
+
+                       for (i, (outp, per_outp_material)) in cached_claim_datas.per_input_material.iter().enumerate() {
+                               match per_outp_material {
+                                       &InputMaterial::Revoked { ref witness_script, ref pubkey, ref key, ref is_htlc, ref amount } => {
+                                               let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
+                                               let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[i], &witness_script, *amount)[..]);
+                                               let sig = self.secp_ctx.sign(&sighash, &key);
+                                               bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
+                                               bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
+                                               if *is_htlc {
+                                                       bumped_tx.input[i].witness.push(pubkey.unwrap().clone().serialize().to_vec());
+                                               } else {
+                                                       bumped_tx.input[i].witness.push(vec!(1));
+                                               }
+                                               bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
+                                               log_trace!(self, "Going to broadcast Penalty Transaction {} claiming revoked {} output {} from {} with new feerate {}...", bumped_tx.txid(), if !is_htlc { "to_local" } else if HTLCType::scriptlen_to_htlctype(witness_script.len()) == Some(HTLCType::OfferedHTLC) { "offered" } else if HTLCType::scriptlen_to_htlctype(witness_script.len()) == Some(HTLCType::AcceptedHTLC) { "received" } else { "" }, outp.vout, outp.txid, new_feerate);
+                                       },
+                                       &InputMaterial::RemoteHTLC { ref witness_script, ref key, ref preimage, ref amount, ref locktime } => {
+                                               if !preimage.is_some() { bumped_tx.lock_time = *locktime }; // Right now we don't aggregate time-locked transaction, if we do we should set lock_time before to avoid breaking hash computation
+                                               let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
+                                               let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[i], &witness_script, *amount)[..]);
+                                               let sig = self.secp_ctx.sign(&sighash, &key);
+                                               bumped_tx.input[i].witness.push(sig.serialize_der().to_vec());
+                                               bumped_tx.input[i].witness[0].push(SigHashType::All as u8);
+                                               if let &Some(preimage) = preimage {
+                                                       bumped_tx.input[i].witness.push(preimage.clone().0.to_vec());
+                                               } else {
+                                                       bumped_tx.input[i].witness.push(vec![]);
+                                               }
+                                               bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
+                                               log_trace!(self, "Going to broadcast Claim Transaction {} claiming remote {} htlc output {} from {} with new feerate {}...", bumped_tx.txid(), if preimage.is_some() { "offered" } else { "received" }, outp.vout, outp.txid, new_feerate);
+                                       },
+                                       _ => unreachable!()
+                               }
+                       }
+                       log_trace!(self, "...with timer {}", new_timer.unwrap());
+                       assert!(predicted_weight >= bumped_tx.get_weight());
+                       return Some((new_timer, new_feerate, bumped_tx))
+               } else {
+                       for (_, (outp, per_outp_material)) in cached_claim_datas.per_input_material.iter().enumerate() {
+                               match per_outp_material {
+                                       &InputMaterial::LocalHTLC { ref preimage, ref amount } => {
+                                               let htlc_tx = self.get_fully_signed_htlc_tx(outp, preimage);
+                                               if let Some(htlc_tx) = htlc_tx {
+                                                       let feerate = (amount - htlc_tx.output[0].value) * 1000 / htlc_tx.get_weight() as u64;
+                                                       // Timer set to $NEVER given we can't bump tx without anchor outputs
+                                                       log_trace!(self, "Going to broadcast Local HTLC-{} claiming HTLC output {} from {}...", if preimage.is_some() { "Success" } else { "Timeout" }, outp.vout, outp.txid);
+                                                       return Some((None, feerate, htlc_tx));
+                                               }
+                                               return None;
+                                       },
+                                       &InputMaterial::Funding { ref funding_redeemscript } => {
+                                               let signed_tx = self.get_fully_signed_local_tx(funding_redeemscript).unwrap();
+                                               // Timer set to $NEVER given we can't bump tx without anchor outputs
+                                               log_trace!(self, "Going to broadcast Local Transaction {} claiming funding output {} from {}...", signed_tx.txid(), outp.vout, outp.txid);
+                                               return Some((None, self.local_commitment.as_ref().unwrap().feerate_per_kw, signed_tx));
                                        }
-                                       bumped_tx.input[i].witness.push(witness_script.clone().into_bytes());
-                                       log_trace!(self, "Going to broadcast Claim Transaction {} claiming remote {} htlc output {} from {} with new feerate {}...", bumped_tx.txid(), if preimage.is_some() { "offered" } else { "received" }, outp.vout, outp.txid, new_feerate);
-                               },
-                               &InputMaterial::LocalHTLC { .. } => {
-                                       //TODO : Given that Local Commitment Transaction and HTLC-Timeout/HTLC-Success are counter-signed by peer, we can't
-                                       // RBF them. Need a Lightning specs change and package relay modification :
-                                       // https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-November/016518.html
-                                       return None;
+                                       _ => unreachable!()
                                }
                        }
                }
-               log_trace!(self, "...with timer {}", new_timer);
-               assert!(predicted_weight >= bumped_tx.get_weight());
-               Some((new_timer, new_feerate, bumped_tx))
+               None
        }
 
        pub(super) fn block_connected<B: Deref, F: Deref>(&mut self, txn_matched: &[&Transaction], claimable_outpoints: Vec<ClaimRequest>, height: u32, broadcaster: B, fee_estimator: F)
@@ -519,23 +621,23 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 
                // Generate claim transactions and track them to bump if necessary at
                // height timer expiration (i.e in how many blocks we're going to take action).
-               for claim in new_claims {
-                       let mut claim_material = ClaimTxBumpMaterial { height_timer: 0, feerate_previous: 0, soonest_timelock: claim.0, per_input_material: claim.1.clone() };
+               for (soonest_timelock, claim) in new_claims.drain(..) {
+                       let mut claim_material = ClaimTxBumpMaterial { height_timer: None, feerate_previous: 0, soonest_timelock, per_input_material: claim };
                        if let Some((new_timer, new_feerate, tx)) = self.generate_claim_tx(height, &claim_material, &*fee_estimator) {
                                claim_material.height_timer = new_timer;
                                claim_material.feerate_previous = new_feerate;
                                let txid = tx.txid();
-                               self.pending_claim_requests.insert(txid, claim_material);
-                               for k in claim.1.keys() {
+                               for k in claim_material.per_input_material.keys() {
                                        log_trace!(self, "Registering claiming request for {}:{}", k.txid, k.vout);
                                        self.claimable_outpoints.insert(k.clone(), (txid, height));
                                }
+                               self.pending_claim_requests.insert(txid, claim_material);
                                log_trace!(self, "Broadcast onchain {}", log_tx!(tx));
                                broadcaster.broadcast_transaction(&tx);
                        }
                }
 
-               let mut bump_candidates = HashSet::new();
+               let mut bump_candidates = HashMap::new();
                for tx in txn_matched {
                        // Scan all input to verify is one of the outpoint spent is of interest for us
                        let mut claimed_outputs_material = Vec::new();
@@ -592,7 +694,7 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
                                                        }
                                                        //TODO: recompute soonest_timelock to avoid wasting a bit on fees
                                                        if at_least_one_drop {
-                                                               bump_candidates.insert(first_claim_txid_height.0.clone());
+                                                               bump_candidates.insert(first_claim_txid_height.0.clone(), claim_material.clone());
                                                        }
                                                }
                                                break; //No need to iterate further, either tx is our or their
@@ -638,27 +740,23 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 
                // Check if any pending claim request must be rescheduled
                for (first_claim_txid, ref claim_data) in self.pending_claim_requests.iter() {
-                       if claim_data.height_timer == height {
-                               bump_candidates.insert(*first_claim_txid);
+                       if let Some(h) = claim_data.height_timer {
+                               if h == height {
+                                       bump_candidates.insert(*first_claim_txid, (*claim_data).clone());
+                               }
                        }
                }
 
                // Build, bump and rebroadcast tx accordingly
                log_trace!(self, "Bumping {} candidates", bump_candidates.len());
-               for first_claim_txid in bump_candidates.iter() {
-                       if let Some((new_timer, new_feerate)) = {
-                               if let Some(claim_material) = self.pending_claim_requests.get(first_claim_txid) {
-                                       if let Some((new_timer, new_feerate, bump_tx)) = self.generate_claim_tx(height, &claim_material, &*fee_estimator) {
-                                               log_trace!(self, "Broadcast onchain {}", log_tx!(bump_tx));
-                                               broadcaster.broadcast_transaction(&bump_tx);
-                                               Some((new_timer, new_feerate))
-                                       } else { None }
-                               } else { unreachable!(); }
-                       } {
+               for (first_claim_txid, claim_material) in bump_candidates.iter() {
+                       if let Some((new_timer, new_feerate, bump_tx)) = self.generate_claim_tx(height, &claim_material, &*fee_estimator) {
+                               log_trace!(self, "Broadcast onchain {}", log_tx!(bump_tx));
+                               broadcaster.broadcast_transaction(&bump_tx);
                                if let Some(claim_material) = self.pending_claim_requests.get_mut(first_claim_txid) {
                                        claim_material.height_timer = new_timer;
                                        claim_material.feerate_previous = new_feerate;
-                               } else { unreachable!(); }
+                               }
                        }
                }
        }
@@ -709,4 +807,123 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
                        self.pending_claim_requests.remove(&req);
                }
        }
+
+       pub(super) fn provide_latest_local_tx(&mut self, tx: LocalCommitmentTransaction) -> Result<(), ()> {
+               // To prevent any unsafe state discrepancy between offchain and onchain, once local
+               // commitment transaction has been signed due to an event (either block height for
+               // HTLC-timeout or channel force-closure), don't allow any further update of local
+               // commitment transaction view to avoid delivery of revocation secret to counterparty
+               // for the aformentionned signed transaction.
+               if let Some(ref local_commitment) = self.local_commitment {
+                       if local_commitment.has_local_sig() { return Err(()) }
+               }
+               if self.local_htlc_sigs.is_some() || self.prev_local_htlc_sigs.is_some() {
+                       return Err(());
+               }
+               self.prev_local_commitment = self.local_commitment.take();
+               self.local_commitment = Some(tx);
+               Ok(())
+       }
+
+       fn sign_latest_local_htlcs(&mut self) {
+               if let Some(ref local_commitment) = self.local_commitment {
+                       if let Ok(sigs) = self.key_storage.sign_local_commitment_htlc_transactions(local_commitment, self.local_csv, &self.secp_ctx) {
+                               self.local_htlc_sigs = Some(Vec::new());
+                               let ret = self.local_htlc_sigs.as_mut().unwrap();
+                               for (htlc_idx, (local_sig, &(ref htlc, _))) in sigs.iter().zip(local_commitment.per_htlc.iter()).enumerate() {
+                                       if let Some(tx_idx) = htlc.transaction_output_index {
+                                               if ret.len() <= tx_idx as usize { ret.resize(tx_idx as usize + 1, None); }
+                                               ret[tx_idx as usize] = Some((htlc_idx, local_sig.expect("Did not receive a signature for a non-dust HTLC")));
+                                       } else {
+                                               assert!(local_sig.is_none(), "Received a signature for a dust HTLC");
+                                       }
+                               }
+                       }
+               }
+       }
+       fn sign_prev_local_htlcs(&mut self) {
+               if let Some(ref local_commitment) = self.prev_local_commitment {
+                       if let Ok(sigs) = self.key_storage.sign_local_commitment_htlc_transactions(local_commitment, self.local_csv, &self.secp_ctx) {
+                               self.prev_local_htlc_sigs = Some(Vec::new());
+                               let ret = self.prev_local_htlc_sigs.as_mut().unwrap();
+                               for (htlc_idx, (local_sig, &(ref htlc, _))) in sigs.iter().zip(local_commitment.per_htlc.iter()).enumerate() {
+                                       if let Some(tx_idx) = htlc.transaction_output_index {
+                                               if ret.len() <= tx_idx as usize { ret.resize(tx_idx as usize + 1, None); }
+                                               ret[tx_idx as usize] = Some((htlc_idx, local_sig.expect("Did not receive a signature for a non-dust HTLC")));
+                                       } else {
+                                               assert!(local_sig.is_none(), "Received a signature for a dust HTLC");
+                                       }
+                               }
+                       }
+               }
+       }
+
+       //TODO: getting lastest local transactions should be infaillible and result in us "force-closing the channel", but we may
+       // have empty local commitment transaction if a ChannelMonitor is asked to force-close just after Channel::get_outbound_funding_created,
+       // before providing a initial commitment transaction. For outbound channel, init ChannelMonitor at Channel::funding_signed, there is nothing
+       // to monitor before.
+       pub(super) fn get_fully_signed_local_tx(&mut self, funding_redeemscript: &Script) -> Option<Transaction> {
+               if let Some(ref mut local_commitment) = self.local_commitment {
+                       match self.key_storage.sign_local_commitment(local_commitment, &self.secp_ctx) {
+                               Ok(sig) => local_commitment.add_local_sig(funding_redeemscript, sig),
+                               Err(_) => return None,
+                       }
+                       return Some(local_commitment.with_valid_witness().clone());
+               }
+               None
+       }
+
+       #[cfg(test)]
+       pub(super) fn get_fully_signed_copy_local_tx(&mut self, funding_redeemscript: &Script) -> Option<Transaction> {
+               if let Some(ref mut local_commitment) = self.local_commitment {
+                       let mut local_commitment = local_commitment.clone();
+                       match self.key_storage.sign_local_commitment(&local_commitment, &self.secp_ctx) {
+                               Ok(sig) => local_commitment.add_local_sig(funding_redeemscript, sig),
+                               Err(_) => return None,
+                       }
+                       return Some(local_commitment.with_valid_witness().clone());
+               }
+               None
+       }
+
+       pub(super) fn get_fully_signed_htlc_tx(&mut self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>) -> Option<Transaction> {
+               let mut htlc_tx = None;
+               if self.local_commitment.is_some() {
+                       let commitment_txid = self.local_commitment.as_ref().unwrap().txid();
+                       if commitment_txid == outp.txid {
+                               self.sign_latest_local_htlcs();
+                               if let &Some(ref htlc_sigs) = &self.local_htlc_sigs {
+                                       let &(ref htlc_idx, ref htlc_sig) = htlc_sigs[outp.vout as usize].as_ref().unwrap();
+                                       htlc_tx = Some(self.local_commitment.as_ref().unwrap()
+                                               .get_signed_htlc_tx(*htlc_idx, htlc_sig, preimage, self.local_csv));
+                               }
+                       }
+               }
+               if self.prev_local_commitment.is_some() {
+                       let commitment_txid = self.prev_local_commitment.as_ref().unwrap().txid();
+                       if commitment_txid == outp.txid {
+                               self.sign_prev_local_htlcs();
+                               if let &Some(ref htlc_sigs) = &self.prev_local_htlc_sigs {
+                                       let &(ref htlc_idx, ref htlc_sig) = htlc_sigs[outp.vout as usize].as_ref().unwrap();
+                                       htlc_tx = Some(self.prev_local_commitment.as_ref().unwrap()
+                                               .get_signed_htlc_tx(*htlc_idx, htlc_sig, preimage, self.local_csv));
+                               }
+                       }
+               }
+               htlc_tx
+       }
+
+       #[cfg(test)]
+       pub(super) fn unsafe_get_fully_signed_htlc_tx(&mut self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>) -> Option<Transaction> {
+               let latest_had_sigs = self.local_htlc_sigs.is_some();
+               let prev_had_sigs = self.prev_local_htlc_sigs.is_some();
+               let ret = self.get_fully_signed_htlc_tx(outp, preimage);
+               if !latest_had_sigs {
+                       self.local_htlc_sigs = None;
+               }
+               if !prev_had_sigs {
+                       self.prev_local_htlc_sigs = None;
+               }
+               ret
+       }
 }