smite-ir: add RecvShutdown operation

smite-ir/src/mutators/operation_param.rs

@@ -122,6 +122,7 @@ fn mutate_operation(op: &mut Operation, rng: &mut impl Rng) -> bool {
         | Operation::RecvAcceptChannel
         | Operation::RecvFundingSigned
         | Operation::RecvChannelReady
+        | Operation::RecvShutdown
         | Operation::BroadcastTransaction
         | Operation::LookupShortChannelId => {
             unreachable!("is_param_mutable returned true for {op:?}")

smite-ir/src/operation.rs

@@ -228,6 +228,17 @@ pub enum Operation {
     /// point unknown) and its funding transaction has enough confirmations for
     /// the target to have sent `channel_ready`.
     RecvChannelReady,
+    /// Receive and parse the target's `shutdown` in reply to ours.
+    /// Produces the target's `scriptpubkey` (`Bytes`), or empty `Bytes` if no
+    /// `shutdown` was received.
+    ///
+    /// This is a no-op unless the channel is tracked and the target has not
+    /// replied yet. A `warning` the target may send instead of replying is
+    /// accepted.
+    ///
+    /// Inputs (1):
+    ///   0: `SentShutdown` from the `SendShutdown` being answered
+    RecvShutdown,
     /// Mines the given number of blocks on the Bitcoin network.
     MineBlocks(u8),
     /// Sign wallet inputs of the transaction and broadcast it via `bitcoin-cli`.
@@ -556,6 +567,7 @@ impl fmt::Display for Operation {
             Self::RecvAcceptChannel => write!(f, "RecvAcceptChannel"),
             Self::RecvFundingSigned => write!(f, "RecvFundingSigned"),
             Self::RecvChannelReady => write!(f, "RecvChannelReady()"),
+            Self::RecvShutdown => write!(f, "RecvShutdown"),
             Self::MineBlocks(v) => write!(f, "MineBlocks({v})"),
             Self::BroadcastTransaction => write!(f, "BroadcastTransaction"),
             Self::LookupShortChannelId => write!(f, "LookupShortChannelId"),
@@ -579,7 +591,9 @@ impl Operation {
             Self::LoadForwardingFee(_) => Some(VariableType::ForwardingFee),
             Self::LoadU16(_) => Some(VariableType::U16),
             Self::LoadU8(_) => Some(VariableType::U8),
-            Self::LoadBytes(_) | Self::LoadShutdownScript(_) => Some(VariableType::Bytes),
+            Self::LoadBytes(_) | Self::LoadShutdownScript(_) | Self::RecvShutdown => {
+                Some(VariableType::Bytes)
+            }
             Self::LoadFeatures(_) | Self::LoadChannelType(_) => Some(VariableType::Features),
             Self::LoadPrivateKey(_) => Some(VariableType::PrivateKey),
             Self::LoadChannelId(_) | Self::RecvFundingSigned => Some(VariableType::ChannelId),
@@ -718,6 +732,7 @@ impl Operation {
             ],
             Self::RecvAcceptChannel => vec![VariableType::SentOpenChannel],
             Self::RecvFundingSigned => vec![VariableType::SentFundingCreated],
+            Self::RecvShutdown => vec![VariableType::SentShutdown],
             Self::BroadcastTransaction | Self::LookupShortChannelId => {
                 vec![VariableType::FundingTransaction]
             }
@@ -763,6 +778,7 @@ impl Operation {
             | Self::SendShutdown
             | Self::RecvFundingSigned
             | Self::RecvChannelReady
+            | Self::RecvShutdown
             | Self::MineBlocks(_)
             | Self::BroadcastTransaction
             | Self::LookupShortChannelId => vec![],
@@ -812,6 +828,7 @@ impl Operation {
             | Self::RecvAcceptChannel
             | Self::RecvFundingSigned
             | Self::RecvChannelReady
+            | Self::RecvShutdown
             | Self::MineBlocks(_)
             | Self::BroadcastTransaction => true,
         }
@@ -866,6 +883,7 @@ impl Operation {
             | Self::RecvAcceptChannel
             | Self::RecvFundingSigned
             | Self::RecvChannelReady
+            | Self::RecvShutdown
             | Self::MineBlocks(_)
             | Self::BroadcastTransaction
             | Self::LookupShortChannelId => false,
@@ -919,6 +937,7 @@ impl Operation {
             | Self::RecvAcceptChannel
             | Self::RecvFundingSigned
             | Self::RecvChannelReady
+            | Self::RecvShutdown
             | Self::BroadcastTransaction
             | Self::LookupShortChannelId => false,
         }

smite-ir/src/tests.rs

@@ -570,7 +570,7 @@ fn display_send_and_recv_channel_ready_program() {
 }
 
 #[test]
-fn display_send_shutdown_program() {
+fn display_send_and_recv_shutdown_program() {
     let instructions = vec![
         Instruction {
             operation: Operation::LoadChannelId([0xcd; 32]),
@@ -584,6 +584,10 @@ fn display_send_shutdown_program() {
             operation: Operation::SendShutdown,
             inputs: vec![0, 1],
         },
+        Instruction {
+            operation: Operation::RecvShutdown,
+            inputs: vec![2],
+        },
     ];
 
     let program = Program { instructions };
@@ -596,6 +600,7 @@ fn display_send_shutdown_program() {
         format!("v0 = LoadChannelId(0x{cid_hex})"),
         format!("v1 = LoadShutdownScript(P2wpkh(0x{spk_hex}))"),
         "v2 = SendShutdown(v0, v1)".into(),
+        "v3 = RecvShutdown(v2)".into(),
     ];
     assert_eq!(lines.len(), expected.len(), "line count mismatch");
     for (i, (got, want)) in lines.iter().zip(expected.iter()).enumerate() {

smite-ir/src/variable.rs

@@ -4,7 +4,7 @@
 //! The serialized program stores data only in [`Operation`] literals.
 
 use bitcoin::secp256k1::PublicKey;
-use smite::bolt::{AcceptChannel, ChannelId, OpenChannel, ShortChannelId};
+use smite::bolt::{AcceptChannel, ChannelId, OpenChannel, ShortChannelId, Shutdown};
 use smite::channel_tx::FundingTransaction;
 
 const CHAIN_HASH_SIZE: usize = 32;
@@ -60,7 +60,7 @@ pub enum Variable {
     SentFundingCreated,
     /// `shutdown` has been sent, so the counterparty's `shutdown` may now be
     /// received.
-    SentShutdown,
+    SentShutdown(Shutdown),
 }
 
 impl Variable {
@@ -88,7 +88,7 @@ impl Variable {
             Self::FundingTransaction(_) => VariableType::FundingTransaction,
             Self::SentOpenChannel => VariableType::SentOpenChannel,
             Self::SentFundingCreated => VariableType::SentFundingCreated,
-            Self::SentShutdown => VariableType::SentShutdown,
+            Self::SentShutdown(_) => VariableType::SentShutdown,
         }
     }
 }

smite-scenarios/src/executor.rs

@@ -11,7 +11,7 @@ use smite::bolt::{
     AcceptChannel, AnnouncementSignatures, ChannelAnnouncement, ChannelId, ChannelReady,
     ChannelReadyTlvs, ChannelUpdate, Features, FromMessage, FundingCreated, FundingSigned, Message,
     MessageType, NodeAnnouncement, OpenChannel, OpenChannelTlvs, Pong, ShortChannelId, Shutdown,
-    TemporaryChannelId,
+    TemporaryChannelId, is_standard_shutdown_script,
 };
 use smite::channel_tx::{
     ChannelConfig, ChannelPartyConfig, ChannelState, FundingTransaction, HolderIdentity, Side,
@@ -484,14 +484,14 @@ impl<C: Connection, B: BitcoinRpc, R: TargetRpc> Executor<C, B, R> {
 
                 Operation::SendShutdown => {
                     let sd = build_shutdown(&variables, &instr.inputs);
-                    let encoded = Message::Shutdown(sd).encode();
+                    let encoded = Message::Shutdown(sd.clone()).encode();
                     log::debug!(
                         "[{:?}] SendShutdown: {} bytes",
                         start.elapsed(),
                         encoded.len()
                     );
                     self.conn.send_message(&encoded)?;
-                    Some(Variable::SentShutdown)
+                    Some(Variable::SentShutdown(sd))
                 }
 
                 Operation::RecvAcceptChannel => {
@@ -538,6 +538,40 @@ impl<C: Connection, B: BitcoinRpc, R: TargetRpc> Executor<C, B, R> {
                     None
                 }
 
+                Operation::RecvShutdown => {
+                    let Variable::SentShutdown(sent) = consume_affine(
+                        &mut variables,
+                        instr.inputs[0],
+                        instr.operation.input_types()[0],
+                    ) else {
+                        unreachable!("consume_affine checked the variable type");
+                    };
+                    // TODO: we only expect `shutdown` when all HTLCs are resolved, else this is a
+                    // no-op.
+                    let reply = if is_shutdown_expected(&self.channel_states, sent.channel_id) {
+                        log::debug!("[{:?}] RecvShutdown: waiting", start.elapsed());
+                        let reply = recv_shutdown_reply(
+                            &mut self.conn,
+                            &sent,
+                            &self.context.negotiated_features,
+                        )?;
+                        log::debug!("[{:?}] RecvShutdown: received", start.elapsed());
+                        reply
+                    } else {
+                        None
+                    };
+                    match reply {
+                        Some(sd) => {
+                            self.channel_states
+                                .get_mut(&sent.channel_id)
+                                .expect("is_shutdown_expected guarantees a tracked channel")
+                                .counterparty_shutdown_received = true;
+                            Some(Variable::Bytes(sd.scriptpubkey))
+                        }
+                        None => Some(Variable::Bytes(Vec::new())),
+                    }
+                }
+
                 Operation::MineBlocks(v) => {
                     // Clear the private mempool and mine the requested blocks,
                     // adding those transactions to the first block.
@@ -681,8 +715,12 @@ define_resolver!(
 );
 
 /// Consumes an affine variable, leaving its slot void so it cannot be used
-/// again.
-fn consume_affine(variables: &mut [Option<Variable>], index: usize, expected: VariableType) {
+/// again, and returns it.
+fn consume_affine(
+    variables: &mut [Option<Variable>],
+    index: usize,
+    expected: VariableType,
+) -> Variable {
     assert!(
         expected.is_affine(),
         "consume_affine called with non-affine type {expected:?}; voiding the slot would break later reads"
@@ -691,7 +729,9 @@ fn consume_affine(variables: &mut [Option<Variable>], index: usize, expected: Va
     if actual != expected {
         type_mismatch(index, expected, actual);
     }
-    variables[index] = None;
+    variables[index]
+        .take()
+        .expect("resolve checked the slot is not void")
 }
 
 // -- Operation handlers --
@@ -1247,6 +1287,60 @@ fn is_channel_ready_expected(
     })
 }
 
+/// Returns `true` if the target still owes us a `shutdown` response on the given channel.
+fn is_shutdown_expected(
+    channel_states: &HashMap<ChannelId, ChannelState>,
+    channel_id: ChannelId,
+) -> bool {
+    // TODO: we don't know for sure if the target will reply because if a target didn't reply with
+    // `channel_ready` yet, it MAY reply with `shutdown` (but doesn't have to)
+    // TODO: once the target has replied, a duplicate `shutdown` from it goes unread here
+    channel_states
+        .get(&channel_id)
+        .is_some_and(|state| !state.counterparty_shutdown_received)
+}
+
+/// Receives the target's reply to our `shutdown`, or `None` if it sent a
+/// `warning` for our channel instead, which BOLT 2 allows when our
+/// `scriptpubkey` is non-standard.
+///
+/// # Errors
+///
+/// Returns [`ExecuteError::UnexpectedMessage`] if the received message is
+/// neither a `shutdown` nor such a `warning`, or is a `shutdown` for another
+/// channel. That may answer a `shutdown` we sent there earlier, which we can't
+/// check against the `shutdown` we sent on this channel.
+fn recv_shutdown_reply(
+    conn: &mut impl Connection,
+    sent: &Shutdown,
+    negotiated_features: &Features,
+) -> Result<Option<Shutdown>, ExecuteError> {
+    let may_warn = !is_standard_shutdown_script(&sent.scriptpubkey, negotiated_features);
+    match recv_non_ping(conn, RECV_IDLE_TIMEOUT)? {
+        Message::Shutdown(sd) if sd.channel_id == sent.channel_id => Ok(Some(sd)),
+        Message::Shutdown(sd) => {
+            log::debug!(
+                "received shutdown on {} while waiting on {}",
+                sd.channel_id,
+                sent.channel_id
+            );
+            Err(ExecuteError::UnexpectedMessage {
+                expected: MessageType::SHUTDOWN,
+                got: MessageType::SHUTDOWN,
+            })
+        }
+        Message::Warning(w)
+            if may_warn && (w.channel_id == sent.channel_id || w.channel_id == ChannelId::ALL) =>
+        {
+            Ok(None)
+        }
+        other => Err(ExecuteError::UnexpectedMessage {
+            expected: MessageType::SHUTDOWN,
+            got: other.msg_type(),
+        }),
+    }
+}
+
 /// Records a sent `open_channel`, keyed by `temporary_channel_id`, so the
 /// funding flow can build commitments from the values actually put on the wire.
 ///