Merge pull request #341 from TheBlueMatt/2019-06-fuzz-crash-fee-sub

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

diff --git a/src/ln/channelmonitor.rs b/src/ln/channelmonitor.rs
index e1d960e5130baaff7a7622f24e01c6d785efe4a0..37fcf2db223df83c042c8e6d82b3d8d8de5806cf 100644 (file)
--- a/src/ln/channelmonitor.rs
+++ b/src/ln/channelmonitor.rs
@@ -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
@@ -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);
+                                                       }
                                                }
                                        }
                                }
@@ -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);
@@ -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 {
@@ -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);
@@ -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);