Implement fail backward in case of detection of revoked tx

Add test_commitment_revoked_fail_backward

Close #137

Author: Antoine Riard

src/ln/channelmanager.rs

@@ -2147,6 +2147,10 @@ impl ChainListener for ChannelManager {
 						hash_to_remove.push((None, htlc_with_hash.clone()));
 					} else if tx.input.len() > 0 && tx.input[0].witness.len() == 3 && tx.input[0].witness[2].len() == 138 && payment_hash160 == tx.input[0].witness[2][69..89] {
 						hash_to_remove.push((None, htlc_with_hash.clone()));
+					} else if let Some(hashs) = self.monitor.is_revoked_tx(&tx) {
+						for hash in hashs {
+							hash_to_remove.push((None, hash));
+						}
 					}
 				}
 			}
@@ -4544,6 +4548,54 @@ mod tests {
 		assert_eq!(node_txn[2].clone().input[0].witness.last().unwrap().len(), 133);
 	}
 
+	#[test]
+	fn test_commitment_revoked_fail_backward() {
+		// Test that in case of a revoked commitment tx, we detect the resolution of output by justice tx
+		// and fail backward accordingly.
+
+		let nodes = create_network(3);
+
+		// Create some initial channels
+		create_announced_chan_between_nodes(&nodes, 0, 1);
+		let chan_2 = create_announced_chan_between_nodes(&nodes, 1, 2);
+
+		// Rebalance the network a bit by relaying one payment through all the channels...
+		send_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 8000000);
+		send_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 8000000);
+
+		let (payment_preimage, _payment_hash) = route_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 3000000);
+		// Get the will-be-revoked local txn from nodes[2]
+		let revoked_local_txn = nodes[2].node.channel_state.lock().unwrap().by_id.get(&chan_2.2).unwrap().last_local_commitment_txn.clone();
+		// Revoke the old state
+		claim_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], payment_preimage);
+
+		route_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 3000000);
+
+		let header = BlockHeader { version: 0x20000000, prev_blockhash: Default::default(), merkle_root: Default::default(), time: 42, bits: 42, nonce: 42};
+		nodes[1].chain_monitor.block_connected_with_filtering(&Block { header, txdata: vec![revoked_local_txn[0].clone()] }, 1);
+		{
+			let mut added_monitors = nodes[1].chan_monitor.added_monitors.lock().unwrap();
+			assert_eq!(added_monitors.len(), 1);
+			added_monitors.clear();
+		}
+		let events = nodes[1].node.get_and_clear_pending_events();
+		assert_eq!(events.len(), 2);
+		match events[0] {
+			Event::UpdateHTLCs { ref node_id, updates: msgs::CommitmentUpdate { ref update_add_htlcs, ref update_fail_htlcs, ref update_fulfill_htlcs, ref update_fail_malformed_htlcs, .. } } => {
+				assert!(update_add_htlcs.is_empty());
+				assert!(!update_fail_htlcs.is_empty());
+				assert!(update_fulfill_htlcs.is_empty());
+				assert!(update_fail_malformed_htlcs.is_empty());
+				assert_eq!(nodes[0].node.get_our_node_id(), *node_id);
+			},
+			_ => panic!("Unexpected event"),
+		}
+		match events[1] {
+			Event::BroadcastChannelUpdate { msg: msgs::ChannelUpdate { .. } } => {},
+			_ => panic!("Unexpected event"),
+		}
+	}
+
 	#[test]
 	fn test_htlc_ignore_latest_remote_commitment() {
 		// Test that HTLC transactions spending the latest remote commitment transaction are simply

src/ln/channelmonitor.rs

@@ -70,6 +70,9 @@ pub trait ManyChannelMonitor: Send + Sync {
 	/// ChainWatchInterfaces such that the provided monitor receives block_connected callbacks with
 	/// any spends of it.
 	fn add_update_monitor(&self, funding_txo: OutPoint, monitor: ChannelMonitor) -> Result<(), ChannelMonitorUpdateErr>;
+	/// In case of revoked commitment tx broadcasted by remote, we need to get current htlc offered to them on their
+	/// last valid commitment tx to fail backward inbound htlcs in others channels belonging to payment route
+	fn is_revoked_tx(&self, tx: &Transaction) -> Option<Vec<[u8;32]>>;
 }
 
 /// A simple implementation of a ManyChannelMonitor and ChainListener. Can be used to create a
@@ -139,6 +142,7 @@ impl<Key : Send + cmp::Eq + hash::Hash + 'static> SimpleManyChannelMonitor<Key>
 		monitors.insert(key, monitor);
 		Ok(())
 	}
+
 }
 
 impl ManyChannelMonitor for SimpleManyChannelMonitor<OutPoint> {
@@ -148,6 +152,20 @@ impl ManyChannelMonitor for SimpleManyChannelMonitor<OutPoint> {
 			Err(_) => Err(ChannelMonitorUpdateErr::PermanentFailure),
 		}
 	}
+
+	fn is_revoked_tx(&self, tx: &Transaction) -> Option<Vec<[u8;32]>> {
+		let monitors = self.monitors.lock().unwrap();
+		let mut hash_to_remove = Vec::new();
+		for monitor in monitors.iter() {
+			if let Some(mut hashs) = monitor.1.is_revoked_tx(tx) {
+				hash_to_remove.append(&mut hashs);
+			}
+		}
+		if hash_to_remove.len() > 0 {
+			return Some(hash_to_remove)
+		}
+		None
+	}
 }
 
 /// If an HTLC expires within this many blocks, don't try to claim it in a shared transaction,
@@ -1265,6 +1283,26 @@ impl ChannelMonitor {
 		}
 		false
 	}
+
+	pub(crate) fn is_revoked_tx(&self, tx: &Transaction) -> Option<Vec<[u8;32]>> {
+		let mut hash_to_remove = Vec::new();
+		if tx.input.len() > 0 {
+			let commitment_number = 0xffffffffffff - ((((tx.input[0].sequence as u64 & 0xffffff) << 3*8) | (tx.lock_time as u64 & 0xffffff)) ^ self.commitment_transaction_number_obscure_factor);
+			if commitment_number >= self.get_min_seen_secret() {
+				if let Some(ref local_commitment_tx) = self.current_local_signed_commitment_tx {
+					for &(ref htlc_output, _, _) in &local_commitment_tx.htlc_outputs {
+						if htlc_output.offered {
+							hash_to_remove.push(htlc_output.payment_hash.clone());
+						}
+					}
+					if hash_to_remove.len() > 0 {
+						return Some(hash_to_remove);
+					}
+				}
+			}
+		}
+		None
+	}
 }
 
 impl<R: ::std::io::Read> Readable<R> for ChannelMonitor {

src/util/test_utils.rs

@@ -59,6 +59,10 @@ impl channelmonitor::ManyChannelMonitor for TestChannelMonitor {
 		self.added_monitors.lock().unwrap().push((funding_txo, monitor.clone()));
 		self.simple_monitor.add_update_monitor(funding_txo, monitor)
 	}
+
+	fn is_revoked_tx(&self, tx: &Transaction) -> Option<Vec<[u8;32]>> {
+		return self.simple_monitor.is_revoked_tx(tx);
+	}
 }
 
 pub struct TestBroadcaster {