Generate shutdown script at channel close
authorJeffrey Czyz <jkczyz@gmail.com>
Mon, 26 Jul 2021 18:04:44 +0000 (14:04 -0400)
committerJeffrey Czyz <jkczyz@gmail.com>
Sat, 31 Jul 2021 05:13:35 +0000 (00:13 -0500)
When a shutdown script is omitted from open_channel or accept_channel,
it must be provided when sending shutdown. Generate the shutdown script
at channel closing time in this case rather at channel opening.

This requires producing a ChannelMonitorUpdate with the shutdown script
since it is no longer known at ChannelMonitor creation.

lightning/src/chain/channelmonitor.rs
lightning/src/ln/channel.rs
lightning/src/ln/channelmanager.rs
lightning/src/ln/functional_tests.rs

index d57d50c613ba43d4dd64c2b9d84d66ff463a9f22..4bad06cde297371f3405801436c3e3ef24108fce 100644 (file)
@@ -434,6 +434,9 @@ pub(crate) enum ChannelMonitorUpdateStep {
                /// think we've fallen behind!
                should_broadcast: bool,
        },
+       ShutdownScript {
+               scriptpubkey: Script,
+       },
 }
 
 impl_writeable_tlv_based_enum!(ChannelMonitorUpdateStep,
@@ -457,6 +460,9 @@ impl_writeable_tlv_based_enum!(ChannelMonitorUpdateStep,
        (4, ChannelForceClosed) => {
                (0, should_broadcast, required),
        },
+       (5, ShutdownScript) => {
+               (0, scriptpubkey, required),
+       },
 ;);
 
 /// A ChannelMonitor handles chain events (blocks connected and disconnected) and generates
@@ -1431,7 +1437,13 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                                // shouldn't print the scary warning above.
                                                log_info!(logger, "Channel off-chain state closed after we broadcasted our latest commitment transaction.");
                                        }
-                               }
+                               },
+                               ChannelMonitorUpdateStep::ShutdownScript { scriptpubkey } => {
+                                       log_trace!(logger, "Updating ChannelMonitor with shutdown script");
+                                       if let Some(shutdown_script) = self.shutdown_script.replace(scriptpubkey.clone()) {
+                                               panic!("Attempted to replace shutdown script {} with {}", shutdown_script, scriptpubkey);
+                                       }
+                               },
                        }
                }
                self.latest_update_id = updates.update_id;
index f6313c075de444d62088d44dc35d6dc48f4a9b84..b22f3756b0c63c95edd0e65699f9136874e8f71d 100644 (file)
@@ -595,6 +595,12 @@ impl<Signer: Sign> Channel<Signer> {
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_provider.get_secure_random_bytes());
 
+               let shutdown_scriptpubkey = if config.channel_options.commit_upfront_shutdown_pubkey {
+                       Some(keys_provider.get_shutdown_scriptpubkey())
+               } else {
+                       None
+               };
+
                Ok(Channel {
                        user_id,
                        config: config.channel_options.clone(),
@@ -607,7 +613,7 @@ impl<Signer: Sign> Channel<Signer> {
                        latest_monitor_update_id: 0,
 
                        holder_signer,
-                       shutdown_scriptpubkey: Some(keys_provider.get_shutdown_scriptpubkey()),
+                       shutdown_scriptpubkey,
                        destination_script: keys_provider.get_destination_script(),
 
                        cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
@@ -840,6 +846,12 @@ impl<Signer: Sign> Channel<Signer> {
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_provider.get_secure_random_bytes());
 
+               let shutdown_scriptpubkey = if config.channel_options.commit_upfront_shutdown_pubkey {
+                       Some(keys_provider.get_shutdown_scriptpubkey())
+               } else {
+                       None
+               };
+
                let chan = Channel {
                        user_id,
                        config: local_config,
@@ -851,7 +863,7 @@ impl<Signer: Sign> Channel<Signer> {
                        latest_monitor_update_id: 0,
 
                        holder_signer,
-                       shutdown_scriptpubkey: Some(keys_provider.get_shutdown_scriptpubkey()),
+                       shutdown_scriptpubkey,
                        destination_script: keys_provider.get_destination_script(),
 
                        cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
@@ -1196,6 +1208,7 @@ impl<Signer: Sign> Channel<Signer> {
                        }, ()));
                }
 
+               assert!(self.shutdown_scriptpubkey.is_some());
                if value_to_self as u64 > self.holder_dust_limit_satoshis {
                        txouts.push((TxOut {
                                script_pubkey: self.get_closing_scriptpubkey(),
@@ -3082,6 +3095,7 @@ impl<Signer: Sign> Channel<Signer> {
                self.channel_state &= !(ChannelState::PeerDisconnected as u32);
 
                let shutdown_msg = if self.channel_state & (ChannelState::LocalShutdownSent as u32) != 0 {
+                       assert!(self.shutdown_scriptpubkey.is_some());
                        Some(msgs::Shutdown {
                                channel_id: self.channel_id,
                                scriptpubkey: self.get_closing_scriptpubkey(),
@@ -3193,6 +3207,7 @@ impl<Signer: Sign> Channel<Signer> {
                if self.feerate_per_kw > proposed_feerate {
                        proposed_feerate = self.feerate_per_kw;
                }
+               assert!(self.shutdown_scriptpubkey.is_some());
                let tx_weight = self.get_closing_transaction_weight(Some(&self.get_closing_scriptpubkey()), Some(self.counterparty_shutdown_scriptpubkey.as_ref().unwrap()));
                let proposed_total_fee_satoshis = proposed_feerate as u64 * tx_weight / 1000;
 
@@ -3211,8 +3226,12 @@ impl<Signer: Sign> Channel<Signer> {
                })
        }
 
-       pub fn shutdown<F: Deref>(&mut self, fee_estimator: &F, their_features: &InitFeatures, msg: &msgs::Shutdown) -> Result<(Option<msgs::Shutdown>, Option<msgs::ClosingSigned>, Vec<(HTLCSource, PaymentHash)>), ChannelError>
-               where F::Target: FeeEstimator
+       pub fn shutdown<F: Deref, K: Deref>(
+               &mut self, fee_estimator: &F, keys_provider: &K, their_features: &InitFeatures, msg: &msgs::Shutdown
+       ) -> Result<(Option<msgs::Shutdown>, Option<msgs::ClosingSigned>, Option<ChannelMonitorUpdate>, Vec<(HTLCSource, PaymentHash)>), ChannelError>
+       where
+               F::Target: FeeEstimator,
+               K::Target: KeysInterface<Signer = Signer>
        {
                if self.channel_state & (ChannelState::PeerDisconnected as u32) == ChannelState::PeerDisconnected as u32 {
                        return Err(ChannelError::Close("Peer sent shutdown when we needed a channel_reestablish".to_owned()));
@@ -3262,23 +3281,36 @@ impl<Signer: Sign> Channel<Signer> {
                                _ => true
                        }
                });
+
                // If we have any LocalAnnounced updates we'll probably just get back a update_fail_htlc
                // immediately after the commitment dance, but we can send a Shutdown cause we won't send
                // any further commitment updates after we set LocalShutdownSent.
-
-               let shutdown = if (self.channel_state & ChannelState::LocalShutdownSent as u32) == ChannelState::LocalShutdownSent as u32 {
-                       None
-               } else {
+               let send_shutdown = (self.channel_state & ChannelState::LocalShutdownSent as u32) != ChannelState::LocalShutdownSent as u32;
+               let monitor_update = match self.shutdown_scriptpubkey {
+                       Some(_) => None,
+                       None => {
+                               assert!(send_shutdown);
+                               self.shutdown_scriptpubkey = Some(keys_provider.get_shutdown_scriptpubkey());
+                               self.latest_monitor_update_id += 1;
+                               Some(ChannelMonitorUpdate {
+                                       update_id: self.latest_monitor_update_id,
+                                       updates: vec![ChannelMonitorUpdateStep::ShutdownScript {
+                                               scriptpubkey: self.get_closing_scriptpubkey(),
+                                       }],
+                               })
+                       },
+               };
+               let shutdown = if send_shutdown {
                        Some(msgs::Shutdown {
                                channel_id: self.channel_id,
                                scriptpubkey: self.get_closing_scriptpubkey(),
                        })
-               };
+               } else { None };
 
                self.channel_state |= ChannelState::LocalShutdownSent as u32;
                self.update_time_counter += 1;
 
-               Ok((shutdown, self.maybe_propose_first_closing_signed(fee_estimator), dropped_outbound_htlcs))
+               Ok((shutdown, self.maybe_propose_first_closing_signed(fee_estimator), monitor_update, dropped_outbound_htlcs))
        }
 
        fn build_signed_closing_transaction(&self, tx: &mut Transaction, counterparty_sig: &Signature, sig: &Signature) {
@@ -3353,6 +3385,7 @@ impl<Signer: Sign> Channel<Signer> {
 
                macro_rules! propose_new_feerate {
                        ($new_feerate: expr) => {
+                               assert!(self.shutdown_scriptpubkey.is_some());
                                let tx_weight = self.get_closing_transaction_weight(Some(&self.get_closing_scriptpubkey()), Some(self.counterparty_shutdown_scriptpubkey.as_ref().unwrap()));
                                let (closing_tx, used_total_fee) = self.build_closing_transaction($new_feerate as u64 * tx_weight / 1000, false);
                                let sig = self.holder_signer
@@ -3851,7 +3884,10 @@ impl<Signer: Sign> Channel<Signer> {
                        htlc_basepoint: keys.htlc_basepoint,
                        first_per_commitment_point,
                        channel_flags: if self.config.announced_channel {1} else {0},
-                       shutdown_scriptpubkey: OptionalField::Present(if self.config.commit_upfront_shutdown_pubkey { self.get_closing_scriptpubkey() } else { Builder::new().into_script() })
+                       shutdown_scriptpubkey: OptionalField::Present(match &self.shutdown_scriptpubkey {
+                               Some(script) => script.clone().into_inner(),
+                               None => Builder::new().into_script(),
+                       }),
                }
        }
 
@@ -3884,7 +3920,10 @@ impl<Signer: Sign> Channel<Signer> {
                        delayed_payment_basepoint: keys.delayed_payment_basepoint,
                        htlc_basepoint: keys.htlc_basepoint,
                        first_per_commitment_point,
-                       shutdown_scriptpubkey: OptionalField::Present(if self.config.commit_upfront_shutdown_pubkey { self.get_closing_scriptpubkey() } else { Builder::new().into_script() })
+                       shutdown_scriptpubkey: OptionalField::Present(match &self.shutdown_scriptpubkey {
+                               Some(script) => script.clone().into_inner(),
+                               None => Builder::new().into_script(),
+                       }),
                }
        }
 
@@ -4392,7 +4431,8 @@ impl<Signer: Sign> Channel<Signer> {
 
        /// Begins the shutdown process, getting a message for the remote peer and returning all
        /// holding cell HTLCs for payment failure.
-       pub fn get_shutdown(&mut self) -> Result<(msgs::Shutdown, Vec<(HTLCSource, PaymentHash)>), APIError> {
+       pub fn get_shutdown<K: Deref>(&mut self, keys_provider: &K) -> Result<(msgs::Shutdown, Option<ChannelMonitorUpdate>, Vec<(HTLCSource, PaymentHash)>), APIError>
+       where K::Target: KeysInterface<Signer = Signer> {
                for htlc in self.pending_outbound_htlcs.iter() {
                        if let OutboundHTLCState::LocalAnnounced(_) = htlc.state {
                                return Err(APIError::APIMisuseError{err: "Cannot begin shutdown with pending HTLCs. Process pending events first".to_owned()});
@@ -4411,7 +4451,16 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(APIError::ChannelUnavailable{err: "Cannot begin shutdown while peer is disconnected or we're waiting on a monitor update, maybe force-close instead?".to_owned()});
                }
 
-               let closing_script = self.get_closing_scriptpubkey();
+               let monitor_update = if self.shutdown_scriptpubkey.is_none() {
+                       self.shutdown_scriptpubkey = Some(keys_provider.get_shutdown_scriptpubkey());
+                       self.latest_monitor_update_id += 1;
+                       Some(ChannelMonitorUpdate {
+                               update_id: self.latest_monitor_update_id,
+                               updates: vec![ChannelMonitorUpdateStep::ShutdownScript {
+                                       scriptpubkey: self.get_closing_scriptpubkey(),
+                               }],
+                       })
+               } else { None };
 
                // From here on out, we may not fail!
                if self.channel_state < ChannelState::FundingSent as u32 {
@@ -4437,8 +4486,8 @@ impl<Signer: Sign> Channel<Signer> {
 
                Ok((msgs::Shutdown {
                        channel_id: self.channel_id,
-                       scriptpubkey: closing_script,
-               }, dropped_outbound_htlcs))
+                       scriptpubkey: self.get_closing_scriptpubkey(),
+               }, monitor_update, dropped_outbound_htlcs))
        }
 
        /// Gets the latest commitment transaction and any dependent transactions for relay (forcing
index f4caa3edfe43fd317750adac832525ec5e5a149c..0ce337f608d32706b601ad53bb2f2012cbb0e85c 100644 (file)
@@ -1256,11 +1256,17 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        let channel_state = &mut *channel_state_lock;
                        match channel_state.by_id.entry(channel_id.clone()) {
                                hash_map::Entry::Occupied(mut chan_entry) => {
-                                       let (shutdown_msg, failed_htlcs) = chan_entry.get_mut().get_shutdown()?;
+                                       let (shutdown_msg, monitor_update, failed_htlcs) = chan_entry.get_mut().get_shutdown(&self.keys_manager)?;
                                        channel_state.pending_msg_events.push(events::MessageSendEvent::SendShutdown {
                                                node_id: chan_entry.get().get_counterparty_node_id(),
                                                msg: shutdown_msg
                                        });
+                                       if let Some(monitor_update) = monitor_update {
+                                               if let Err(_) = self.chain_monitor.update_channel(chan_entry.get().get_funding_txo().unwrap(), monitor_update) {
+                                                       // TODO: How should this be handled?
+                                                       unimplemented!();
+                                               }
+                                       }
                                        if chan_entry.get().is_shutdown() {
                                                if let Some(short_id) = chan_entry.get().get_short_channel_id() {
                                                        channel_state.short_to_id.remove(&short_id);
@@ -3159,7 +3165,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        if chan_entry.get().get_counterparty_node_id() != *counterparty_node_id {
                                                return Err(MsgHandleErrInternal::send_err_msg_no_close("Got a message for a channel from the wrong node!".to_owned(), msg.channel_id));
                                        }
-                                       let (shutdown, closing_signed, dropped_htlcs) = try_chan_entry!(self, chan_entry.get_mut().shutdown(&self.fee_estimator, &their_features, &msg), channel_state, chan_entry);
+                                       let (shutdown, closing_signed, monitor_update, dropped_htlcs) = try_chan_entry!(self, chan_entry.get_mut().shutdown(&self.fee_estimator, &self.keys_manager, &their_features, &msg), channel_state, chan_entry);
                                        if let Some(msg) = shutdown {
                                                channel_state.pending_msg_events.push(events::MessageSendEvent::SendShutdown {
                                                        node_id: counterparty_node_id.clone(),
@@ -3172,6 +3178,12 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                        msg,
                                                });
                                        }
+                                       if let Some(monitor_update) = monitor_update {
+                                               if let Err(_) = self.chain_monitor.update_channel(chan_entry.get().get_funding_txo().unwrap(), monitor_update) {
+                                                       // TODO: How should this be handled?
+                                                       unimplemented!();
+                                               }
+                                       }
                                        if chan_entry.get().is_shutdown() {
                                                if let Some(short_id) = chan_entry.get().get_short_channel_id() {
                                                        channel_state.short_to_id.remove(&short_id);
index 9c71e070bed3b6c91821bee68c435723d69b32ad..21f871fa8d3376405c973e3cd4b7a5607a368171 100644 (file)
@@ -7474,9 +7474,9 @@ fn test_upfront_shutdown_script() {
        let flags_no = InitFeatures::known().clear_upfront_shutdown_script();
        let chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1000000, 1000000, flags_no, flags.clone());
        nodes[0].node.close_channel(&OutPoint { txid: chan.3.txid(), index: 0 }.to_channel_id()).unwrap();
-       let mut node_1_shutdown = get_event_msg!(nodes[0], MessageSendEvent::SendShutdown, nodes[1].node.get_our_node_id());
-       node_1_shutdown.scriptpubkey = Builder::new().push_opcode(opcodes::all::OP_RETURN).into_script().to_p2sh();
+       let node_1_shutdown = get_event_msg!(nodes[0], MessageSendEvent::SendShutdown, nodes[1].node.get_our_node_id());
        nodes[1].node.handle_shutdown(&nodes[0].node.get_our_node_id(), &InitFeatures::known(), &node_1_shutdown);
+       check_added_monitors!(nodes[1], 1);
        let events = nodes[1].node.get_and_clear_pending_msg_events();
        assert_eq!(events.len(), 1);
        match events[0] {
@@ -7488,8 +7488,8 @@ fn test_upfront_shutdown_script() {
        // channel smoothly, opt-out is from channel initiator here
        let chan = create_announced_chan_between_nodes_with_value(&nodes, 1, 0, 1000000, 1000000, flags.clone(), flags.clone());
        nodes[1].node.close_channel(&OutPoint { txid: chan.3.txid(), index: 0 }.to_channel_id()).unwrap();
-       let mut node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());
-       node_0_shutdown.scriptpubkey = Builder::new().push_opcode(opcodes::all::OP_RETURN).into_script().to_p2sh();
+       check_added_monitors!(nodes[1], 1);
+       let node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());
        nodes[0].node.handle_shutdown(&nodes[1].node.get_our_node_id(), &InitFeatures::known(), &node_0_shutdown);
        let events = nodes[0].node.get_and_clear_pending_msg_events();
        assert_eq!(events.len(), 1);
@@ -7502,8 +7502,8 @@ fn test_upfront_shutdown_script() {
        //// channel smoothly
        let chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1000000, 1000000, flags.clone(), flags.clone());
        nodes[1].node.close_channel(&OutPoint { txid: chan.3.txid(), index: 0 }.to_channel_id()).unwrap();
-       let mut node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());
-       node_0_shutdown.scriptpubkey = Builder::new().push_opcode(opcodes::all::OP_RETURN).into_script().to_p2sh();
+       check_added_monitors!(nodes[1], 1);
+       let node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());
        nodes[0].node.handle_shutdown(&nodes[1].node.get_our_node_id(), &InitFeatures::known(), &node_0_shutdown);
        let events = nodes[0].node.get_and_clear_pending_msg_events();
        assert_eq!(events.len(), 2);
@@ -7607,6 +7607,7 @@ fn test_segwit_v0_shutdown_script() {
 
        let chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1000000, 1000000, InitFeatures::known(), InitFeatures::known());
        nodes[1].node.close_channel(&OutPoint { txid: chan.3.txid(), index: 0 }.to_channel_id()).unwrap();
+       check_added_monitors!(nodes[1], 1);
 
        // Use a segwit v0 script supported even without opt_shutdown_anysegwit
        let mut node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());
@@ -7677,6 +7678,7 @@ fn test_unsupported_anysegwit_shutdown_script() {
        let node_features = InitFeatures::known().clear_shutdown_anysegwit();
        let chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1000000, 1000000, InitFeatures::known(), node_features.clone());
        nodes[1].node.close_channel(&OutPoint { txid: chan.3.txid(), index: 0 }.to_channel_id()).unwrap();
+       check_added_monitors!(nodes[1], 1);
 
        // Use a non-v0 segwit script supported by opt_shutdown_anysegwit
        let mut node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());
@@ -7711,6 +7713,7 @@ fn test_invalid_shutdown_script() {
 
        let chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1000000, 1000000, InitFeatures::known(), InitFeatures::known());
        nodes[1].node.close_channel(&OutPoint { txid: chan.3.txid(), index: 0 }.to_channel_id()).unwrap();
+       check_added_monitors!(nodes[1], 1);
 
        // Use a segwit v0 script with an unsupported witness program
        let mut node_0_shutdown = get_event_msg!(nodes[1], MessageSendEvent::SendShutdown, nodes[0].node.get_our_node_id());