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Gracefully handle fee-larger-than-claimed-value in ChannelMonitor #341

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Jul 1, 2019
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Gracefully handle fee-larger-than-claimed-value in ChannelMonitor #341

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75 changes: 58 additions & 17 deletions src/ln/channelmonitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -411,6 +411,38 @@ pub struct ChannelMonitor {
logger: Arc<Logger>,
}

macro_rules! subtract_high_prio_fee {
($self: ident, $fee_estimator: expr, $value: expr, $predicted_weight: expr, $spent_txid: expr) => {
{
let mut fee = $fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) * $predicted_weight / 1000;
if $value <= fee {
fee = $fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Normal) * $predicted_weight / 1000;
if $value <= fee {
fee = $fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background) * $predicted_weight / 1000;
if $value <= fee {
log_error!($self, "Failed to generate an on-chain punishment tx spending {} as even low priority fee ({} sat) was more than the entire claim balance ({} sat)",
$spent_txid, fee, $value);
false
} else {
log_warn!($self, "Used low priority fee for on-chain punishment tx spending {} as high priority fee was more than the entire claim balance ({} sat)",
$spent_txid, $value);
$value -= fee;
true
}
} else {
log_warn!($self, "Used medium priority fee for on-chain punishment tx spending {} as high priority fee was more than the entire claim balance ({} sat)",
$spent_txid, $value);
$value -= fee;
true
}
} else {
$value -= fee;
true
}
}
}
}

#[cfg(any(test, feature = "fuzztarget"))]
/// Used only in testing and fuzztarget to check serialization roundtrips don't change the
/// underlying object
Expand Down Expand Up @@ -1200,11 +1232,12 @@ impl ChannelMonitor {
}),
};
let predicted_weight = single_htlc_tx.get_weight() + Self::get_witnesses_weight(&[if htlc.offered { InputDescriptors::RevokedOfferedHTLC } else { InputDescriptors::RevokedReceivedHTLC }]);
single_htlc_tx.output[0].value -= fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) * predicted_weight / 1000;
let sighash_parts = bip143::SighashComponents::new(&single_htlc_tx);
sign_input!(sighash_parts, single_htlc_tx.input[0], Some(idx), htlc.amount_msat / 1000);
assert!(predicted_weight >= single_htlc_tx.get_weight());
txn_to_broadcast.push(single_htlc_tx);
if subtract_high_prio_fee!(self, fee_estimator, single_htlc_tx.output[0].value, predicted_weight, tx.txid()) {
let sighash_parts = bip143::SighashComponents::new(&single_htlc_tx);
sign_input!(sighash_parts, single_htlc_tx.input[0], Some(idx), htlc.amount_msat / 1000);
assert!(predicted_weight >= single_htlc_tx.get_weight());
txn_to_broadcast.push(single_htlc_tx);
}
}
}
}
Expand Down Expand Up @@ -1254,7 +1287,10 @@ impl ChannelMonitor {
output: outputs,
};
let predicted_weight = spend_tx.get_weight() + Self::get_witnesses_weight(&input_descriptors[..]);
spend_tx.output[0].value -= fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) * predicted_weight / 1000;

if !subtract_high_prio_fee!(self, fee_estimator, spend_tx.output[0].value, predicted_weight, tx.txid()) {
return (txn_to_broadcast, (commitment_txid, watch_outputs), spendable_outputs, htlc_updated);
}

let mut values_drain = values.drain(..);
let sighash_parts = bip143::SighashComponents::new(&spend_tx);
Expand Down Expand Up @@ -1423,15 +1459,16 @@ impl ChannelMonitor {
}),
};
let predicted_weight = single_htlc_tx.get_weight() + Self::get_witnesses_weight(&[if htlc.offered { InputDescriptors::OfferedHTLC } else { InputDescriptors::ReceivedHTLC }]);
single_htlc_tx.output[0].value -= fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) * predicted_weight / 1000;
let sighash_parts = bip143::SighashComponents::new(&single_htlc_tx);
sign_input!(sighash_parts, single_htlc_tx.input[0], htlc.amount_msat / 1000, payment_preimage.0.to_vec());
assert!(predicted_weight >= single_htlc_tx.get_weight());
spendable_outputs.push(SpendableOutputDescriptor::StaticOutput {
outpoint: BitcoinOutPoint { txid: single_htlc_tx.txid(), vout: 0 },
output: single_htlc_tx.output[0].clone(),
});
txn_to_broadcast.push(single_htlc_tx);
if subtract_high_prio_fee!(self, fee_estimator, single_htlc_tx.output[0].value, predicted_weight, tx.txid()) {
let sighash_parts = bip143::SighashComponents::new(&single_htlc_tx);
sign_input!(sighash_parts, single_htlc_tx.input[0], htlc.amount_msat / 1000, payment_preimage.0.to_vec());
assert!(predicted_weight >= single_htlc_tx.get_weight());
spendable_outputs.push(SpendableOutputDescriptor::StaticOutput {
outpoint: BitcoinOutPoint { txid: single_htlc_tx.txid(), vout: 0 },
output: single_htlc_tx.output[0].clone(),
});
txn_to_broadcast.push(single_htlc_tx);
}
}
}
if !htlc.offered {
Expand Down Expand Up @@ -1475,7 +1512,9 @@ impl ChannelMonitor {
output: outputs,
};
let predicted_weight = spend_tx.get_weight() + Self::get_witnesses_weight(&input_descriptors[..]);
spend_tx.output[0].value -= fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) * predicted_weight / 1000;
if !subtract_high_prio_fee!(self, fee_estimator, spend_tx.output[0].value, predicted_weight, tx.txid()) {
return (txn_to_broadcast, (commitment_txid, watch_outputs), spendable_outputs, htlc_updated);
}

let mut values_drain = values.drain(..);
let sighash_parts = bip143::SighashComponents::new(&spend_tx);
Expand Down Expand Up @@ -1561,7 +1600,9 @@ impl ChannelMonitor {
output: outputs,
};
let predicted_weight = spend_tx.get_weight() + Self::get_witnesses_weight(&[InputDescriptors::RevokedOutput]);
spend_tx.output[0].value -= fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) * predicted_weight / 1000;
if !subtract_high_prio_fee!(self, fee_estimator, spend_tx.output[0].value, predicted_weight, tx.txid()) {
return (None, None);
}

let sighash_parts = bip143::SighashComponents::new(&spend_tx);

Expand Down