From e9ac2b1669bf9f3c44de89f67f5d549280065ea3 Mon Sep 17 00:00:00 2001 From: Wilmer Paulino Date: Wed, 31 Aug 2022 11:35:55 -0700 Subject: [PATCH] Generate ClaimEvent for HolderFundingOutput inputs from anchor channels --- lightning/src/chain/onchaintx.rs | 122 ++++++++++++++++++++++++++++--- lightning/src/chain/package.rs | 52 +++++++++++-- lightning/src/ln/chan_utils.rs | 9 +++ 3 files changed, 165 insertions(+), 18 deletions(-) diff --git a/lightning/src/chain/onchaintx.rs b/lightning/src/chain/onchaintx.rs index f79a8775..c8874b7a 100644 --- a/lightning/src/chain/onchaintx.rs +++ b/lightning/src/chain/onchaintx.rs @@ -23,10 +23,16 @@ use bitcoin::secp256k1; use ln::msgs::DecodeError; use ln::PaymentPreimage; +#[cfg(anchors)] +use ln::chan_utils; use ln::chan_utils::{ChannelTransactionParameters, HolderCommitmentTransaction}; +#[cfg(anchors)] +use chain::chaininterface::ConfirmationTarget; use chain::chaininterface::{FeeEstimator, BroadcasterInterface, LowerBoundedFeeEstimator}; use chain::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER}; use chain::keysinterface::{Sign, KeysInterface}; +#[cfg(anchors)] +use chain::package::PackageSolvingData; use chain::package::PackageTemplate; use util::logger::Logger; use util::ser::{Readable, ReadableArgs, MaybeReadable, Writer, Writeable, VecWriter}; @@ -162,11 +168,28 @@ impl Writeable for Option>> { } } +// Represents the different types of claims for which events are yielded externally to satisfy said +// claims. +#[cfg(anchors)] +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. + BumpCommitment { + package_target_feerate_sat_per_1000_weight: u32, + commitment_tx: Transaction, + anchor_output_idx: u32, + }, +} + /// Represents the different ways an output can be claimed (i.e., spent to an address under our /// control) onchain. 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), } /// OnchainTxHandler receives claiming requests, aggregates them if it's sound, broadcast and @@ -199,6 +222,8 @@ pub struct OnchainTxHandler { pub(crate) pending_claim_requests: HashMap, #[cfg(not(test))] pending_claim_requests: HashMap, + #[cfg(anchors)] + pending_claim_events: HashMap, // Used to link outpoints claimed in a connected block to a pending claim request. // Key is outpoint than monitor parsing has detected we have keys/scripts to claim @@ -348,6 +373,8 @@ impl<'a, K: KeysInterface> ReadableArgs<&'a K> for OnchainTxHandler { locktimed_packages, pending_claim_requests, onchain_events_awaiting_threshold_conf, + #[cfg(anchors)] + pending_claim_events: HashMap::new(), secp_ctx, }) } @@ -367,6 +394,8 @@ impl OnchainTxHandler { claimable_outpoints: HashMap::new(), locktimed_packages: BTreeMap::new(), onchain_events_awaiting_threshold_conf: Vec::new(), + #[cfg(anchors)] + pending_claim_events: HashMap::new(), secp_ctx, } @@ -380,10 +409,14 @@ impl OnchainTxHandler { self.holder_commitment.to_broadcaster_value_sat() } - /// 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. - /// Panics if there are signing errors, because signing operations in reaction to on-chain events - /// are not expected to fail, and if they do, we may lose funds. + /// Lightning security model (i.e being able to redeem/timeout HTLC or penalize counterparty + /// 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 get stuck + /// in the mempool, so you need to bump its feerate quickly using Replace-By-Fee or + /// Child-Pay-For-Parent. + /// + /// Panics if there are signing errors, because signing operations in reaction to on-chain + /// events are not expected to fail, and if they do, we may lose funds. fn generate_claim(&mut self, cur_height: u32, cached_request: &PackageTemplate, fee_estimator: &LowerBoundedFeeEstimator, logger: &L) -> Option<(Option, u64, OnchainClaim)> where F::Target: FeeEstimator, L::Target: Logger, @@ -405,12 +438,60 @@ impl OnchainTxHandler { return Some((new_timer, new_feerate, OnchainClaim::Tx(transaction))) } } else { - // 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. - if let Some(transaction) = cached_request.finalize_untractable_package(self, logger) { - return Some((None, 0, OnchainClaim::Tx(transaction))); + // 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) { + Some(tx) => tx, + None => return None, + }; + if !cached_request.requires_external_funding() { + return Some((None, 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(..) => { + debug_assert_eq!(tx.txid(), self.holder_commitment.trust().txid(), + "Holder commitment transaction mismatch"); + // 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) { + // An anchor output was found, so we should yield a funding event externally. + 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); + Some(( + new_timer, + package_target_feerate_sat_per_1000_weight as u64, + OnchainClaim::Event(ClaimEvent::BumpCommitment { + package_target_feerate_sat_per_1000_weight, + commitment_tx: tx.clone(), + anchor_output_idx: idx, + }), + )) + }, + // An anchor output was not found. There's nothing we can do other than + // attempt to broadcast the transaction with its current fee rate and hope + // it confirms. This is essentially the same behavior as a commitment + // transaction without anchor outputs. + None => Some((None, 0, OnchainClaim::Tx(tx.clone()))), + } + }, + _ => { + debug_assert!(false, "Only HolderFundingOutput inputs should be untractable and require external funding"); + None + }, + }); } None } @@ -490,6 +571,15 @@ impl OnchainTxHandler { broadcaster.broadcast_transaction(&tx); tx.txid() }, + #[cfg(anchors)] + OnchainClaim::Event(claim_event) => { + log_info!(logger, "Yielding onchain event to spend inputs {:?}", req.outpoints()); + let txid = match claim_event { + ClaimEvent::BumpCommitment { ref commitment_tx, .. } => commitment_tx.txid(), + }; + self.pending_claim_events.insert(txid, claim_event); + txid + }, }; for k in req.outpoints() { log_info!(logger, "Registering claiming request for {}:{}", k.txid, k.vout); @@ -587,6 +677,8 @@ impl OnchainTxHandler { for outpoint in request.outpoints() { log_debug!(logger, "Removing claim tracking for {} due to maturation of claim tx {}.", outpoint, claim_request); self.claimable_outpoints.remove(&outpoint); + #[cfg(anchors)] + self.pending_claim_events.remove(&claim_request); } } }, @@ -619,6 +711,11 @@ impl OnchainTxHandler { log_info!(logger, "Broadcasting RBF-bumped onchain {}", log_tx!(bump_tx)); broadcaster.broadcast_transaction(&bump_tx); }, + #[cfg(anchors)] + OnchainClaim::Event(claim_event) => { + log_info!(logger, "Yielding RBF-bumped onchain event to spend inputs {:?}", request.outpoints()); + self.pending_claim_events.insert(*first_claim_txid, claim_event); + }, } if let Some(request) = self.pending_claim_requests.get_mut(first_claim_txid) { request.set_timer(new_timer); @@ -681,7 +778,7 @@ impl OnchainTxHandler { self.onchain_events_awaiting_threshold_conf.push(entry); } } - for (_, request) in bump_candidates.iter_mut() { + for (_first_claim_txid_height, request) in bump_candidates.iter_mut() { if let Some((new_timer, new_feerate, bump_claim)) = self.generate_claim(height, &request, fee_estimator, &&*logger) { request.set_timer(new_timer); request.set_feerate(new_feerate); @@ -690,6 +787,11 @@ impl OnchainTxHandler { log_info!(logger, "Broadcasting onchain {}", log_tx!(bump_tx)); broadcaster.broadcast_transaction(&bump_tx); }, + #[cfg(anchors)] + OnchainClaim::Event(claim_event) => { + log_info!(logger, "Yielding onchain event after reorg to spend inputs {:?}", request.outpoints()); + self.pending_claim_events.insert(_first_claim_txid_height.0, claim_event); + }, } } } diff --git a/lightning/src/chain/package.rs b/lightning/src/chain/package.rs index 866ff66b..5aa55fb1 100644 --- a/lightning/src/chain/package.rs +++ b/lightning/src/chain/package.rs @@ -34,6 +34,8 @@ use util::ser::{Readable, Writer, Writeable}; use io; use prelude::*; use core::cmp; +#[cfg(anchors)] +use core::convert::TryInto; use core::mem; use core::ops::Deref; use bitcoin::{PackedLockTime, Sequence, Witness}; @@ -548,6 +550,9 @@ impl PackageTemplate { pub(crate) fn outpoints(&self) -> Vec<&BitcoinOutPoint> { self.inputs.iter().map(|(o, _)| o).collect() } + pub(crate) fn inputs(&self) -> impl ExactSizeIterator { + self.inputs.iter().map(|(_, i)| i) + } pub(crate) fn split_package(&mut self, split_outp: &BitcoinOutPoint) -> Option { match self.malleability { PackageMalleability::Malleable => { @@ -611,7 +616,7 @@ 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(); @@ -637,7 +642,7 @@ impl PackageTemplate { inputs_weight + witnesses_weight + transaction_weight + output_weight } pub(crate) fn finalize_malleable_package( - &self, onchain_handler: &mut OnchainTxHandler, value: u64, destination_script: Script, logger: &L, + &self, onchain_handler: &mut OnchainTxHandler, value: u64, destination_script: Script, logger: &L ) -> Option where L::Target: Logger { debug_assert!(self.is_malleable()); let mut bumped_tx = Transaction { @@ -713,14 +718,45 @@ 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( + &self, fee_estimator: &LowerBoundedFeeEstimator, 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(), + _ => 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(..) => PackageMalleability::Untractable, + PackageSolvingData::HolderFundingOutput(..) => PackageMalleability::Untractable, }; let mut inputs = Vec::with_capacity(1); inputs.push((BitcoinOutPoint { txid, vout }, input_solving_data)); diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs index 69ca4fb8..e1bceb3c 100644 --- a/lightning/src/ln/chan_utils.rs +++ b/lightning/src/ln/chan_utils.rs @@ -727,6 +727,15 @@ pub fn get_anchor_redeemscript(funding_pubkey: &PublicKey) -> Script { .into_script() } +#[cfg(anchors)] +/// Locates the output with an anchor script paying to `funding_pubkey` within `commitment_tx`. +pub(crate) fn get_anchor_output<'a>(commitment_tx: &'a Transaction, funding_pubkey: &PublicKey) -> Option<(u32, &'a TxOut)> { + let anchor_script = chan_utils::get_anchor_redeemscript(funding_pubkey).to_v0_p2wsh(); + commitment_tx.output.iter().enumerate() + .find(|(_, txout)| txout.script_pubkey == anchor_script) + .map(|(idx, txout)| (idx as u32, txout)) +} + /// Per-channel data used to build transactions in conjunction with the per-commitment data (CommitmentTransaction). /// The fields are organized by holder/counterparty. /// -- 2.30.2