_ Git - rust-lightning/blob - lightning/src/ln/interactivetxs.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 use crate::io_extras::sink;
  11 use crate::prelude::*;
  12 use core::ops::Deref;
  13
  14 use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
  15 use bitcoin::consensus::Encodable;
  16 use bitcoin::policy::MAX_STANDARD_TX_WEIGHT;
  17 use bitcoin::{
  18         absolute::LockTime as AbsoluteLockTime, OutPoint, Sequence, Transaction, TxIn, TxOut,
  19 };
  20
  21 use crate::chain::chaininterface::fee_for_weight;
  22 use crate::events::bump_transaction::{BASE_INPUT_WEIGHT, EMPTY_SCRIPT_SIG_WEIGHT};
  23 use crate::ln::channel::TOTAL_BITCOIN_SUPPLY_SATOSHIS;
  24 use crate::ln::msgs::SerialId;
  25 use crate::ln::{msgs, ChannelId};
  26 use crate::sign::EntropySource;
  27 use crate::util::ser::TransactionU16LenLimited;
  28
  29 /// The number of received `tx_add_input` messages during a negotiation at which point the
  30 /// negotiation MUST be failed.
  31 const MAX_RECEIVED_TX_ADD_INPUT_COUNT: u16 = 4096;
  32
  33 /// The number of received `tx_add_output` messages during a negotiation at which point the
  34 /// negotiation MUST be failed.
  35 const MAX_RECEIVED_TX_ADD_OUTPUT_COUNT: u16 = 4096;
  36
  37 /// The number of inputs or outputs that the state machine can have, before it MUST fail the
  38 /// negotiation.
  39 const MAX_INPUTS_OUTPUTS_COUNT: usize = 252;
  40
  41 trait SerialIdExt {
  42         fn is_for_initiator(&self) -> bool;
  43         fn is_for_non_initiator(&self) -> bool;
  44 }
  45
  46 impl SerialIdExt for SerialId {
  47         fn is_for_initiator(&self) -> bool {
  48                 self % 2 == 0
  49         }
  50
  51         fn is_for_non_initiator(&self) -> bool {
  52                 !self.is_for_initiator()
  53         }
  54 }
  55
  56 #[derive(Debug, Clone, PartialEq)]
  57 pub enum AbortReason {
  58         InvalidStateTransition,
  59         UnexpectedCounterpartyMessage,
  60         ReceivedTooManyTxAddInputs,
  61         ReceivedTooManyTxAddOutputs,
  62         IncorrectInputSequenceValue,
  63         IncorrectSerialIdParity,
  64         SerialIdUnknown,
  65         DuplicateSerialId,
  66         PrevTxOutInvalid,
  67         ExceededMaximumSatsAllowed,
  68         ExceededNumberOfInputsOrOutputs,
  69         TransactionTooLarge,
  70         BelowDustLimit,
  71         InvalidOutputScript,
  72         InsufficientFees,
  73         OutputsValueExceedsInputsValue,
  74         InvalidTx,
  75 }
  76
  77 #[derive(Debug)]
  78 pub struct TxInputWithPrevOutput {
  79         input: TxIn,
  80         prev_output: TxOut,
  81 }
  82
  83 #[derive(Debug)]
  84 struct NegotiationContext {
  85         holder_is_initiator: bool,
  86         received_tx_add_input_count: u16,
  87         received_tx_add_output_count: u16,
  88         inputs: HashMap<SerialId, TxInputWithPrevOutput>,
  89         prevtx_outpoints: HashSet<OutPoint>,
  90         outputs: HashMap<SerialId, TxOut>,
  91         tx_locktime: AbsoluteLockTime,
  92         feerate_sat_per_kw: u32,
  93 }
  94
  95 impl NegotiationContext {
  96         fn is_serial_id_valid_for_counterparty(&self, serial_id: &SerialId) -> bool {
  97                 // A received `SerialId`'s parity must match the role of the counterparty.
  98                 self.holder_is_initiator == serial_id.is_for_non_initiator()
  99         }
 100
 101         fn total_input_and_output_count(&self) -> usize {
 102                 self.inputs.len().saturating_add(self.outputs.len())
 103         }
 104
 105         fn counterparty_inputs_contributed(
 106                 &self,
 107         ) -> impl Iterator<Item = &TxInputWithPrevOutput> + Clone {
 108                 self.inputs
 109                         .iter()
 110                         .filter(move |(serial_id, _)| self.is_serial_id_valid_for_counterparty(serial_id))
 111                         .map(|(_, input_with_prevout)| input_with_prevout)
 112         }
 113
 114         fn counterparty_outputs_contributed(&self) -> impl Iterator<Item = &TxOut> + Clone {
 115                 self.outputs
 116                         .iter()
 117                         .filter(move |(serial_id, _)| self.is_serial_id_valid_for_counterparty(serial_id))
 118                         .map(|(_, output)| output)
 119         }
 120
 121         fn received_tx_add_input(&mut self, msg: &msgs::TxAddInput) -> Result<(), AbortReason> {
 122                 // The interactive-txs spec calls for us to fail negotiation if the `prevtx` we receive is
 123                 // invalid. However, we would not need to account for this explicit negotiation failure
 124                 // mode here since `PeerManager` would already disconnect the peer if the `prevtx` is
 125                 // invalid; implicitly ending the negotiation.
 126
 127                 if !self.is_serial_id_valid_for_counterparty(&msg.serial_id) {
 128                         // The receiving node:
 129                         //  - MUST fail the negotiation if:
 130                         //     - the `serial_id` has the wrong parity
 131                         return Err(AbortReason::IncorrectSerialIdParity);
 132                 }
 133
 134                 self.received_tx_add_input_count += 1;
 135                 if self.received_tx_add_input_count > MAX_RECEIVED_TX_ADD_INPUT_COUNT {
 136                         // The receiving node:
 137                         //  - MUST fail the negotiation if:
 138                         //     - if has received 4096 `tx_add_input` messages during this negotiation
 139                         return Err(AbortReason::ReceivedTooManyTxAddInputs);
 140                 }
 141
 142                 if msg.sequence >= 0xFFFFFFFE {
 143                         // The receiving node:
 144                         //  - MUST fail the negotiation if:
 145                         //    - `sequence` is set to `0xFFFFFFFE` or `0xFFFFFFFF`
 146                         return Err(AbortReason::IncorrectInputSequenceValue);
 147                 }
 148
 149                 let transaction = msg.prevtx.as_transaction();
 150                 let txid = transaction.txid();
 151
 152                 if let Some(tx_out) = transaction.output.get(msg.prevtx_out as usize) {
 153                         if !tx_out.script_pubkey.is_witness_program() {
 154                                 // The receiving node:
 155                                 //  - MUST fail the negotiation if:
 156                                 //     - the `scriptPubKey` is not a witness program
 157                                 return Err(AbortReason::PrevTxOutInvalid);
 158                         }
 159
 160                         if !self.prevtx_outpoints.insert(OutPoint { txid, vout: msg.prevtx_out }) {
 161                                 // The receiving node:
 162                                 //  - MUST fail the negotiation if:
 163                                 //     - the `prevtx` and `prevtx_vout` are identical to a previously added
 164                                 //       (and not removed) input's
 165                                 return Err(AbortReason::PrevTxOutInvalid);
 166                         }
 167                 } else {
 168                         // The receiving node:
 169                         //  - MUST fail the negotiation if:
 170                         //     - `prevtx_vout` is greater or equal to the number of outputs on `prevtx`
 171                         return Err(AbortReason::PrevTxOutInvalid);
 172                 }
 173
 174                 let prev_out = if let Some(prev_out) = transaction.output.get(msg.prevtx_out as usize) {
 175                         prev_out.clone()
 176                 } else {
 177                         return Err(AbortReason::PrevTxOutInvalid);
 178                 };
 179                 match self.inputs.entry(msg.serial_id) {
 180                         hash_map::Entry::Occupied(_) => {
 181                                 // The receiving node:
 182                                 //  - MUST fail the negotiation if:
 183                                 //    - the `serial_id` is already included in the transaction
 184                                 Err(AbortReason::DuplicateSerialId)
 185                         },
 186                         hash_map::Entry::Vacant(entry) => {
 187                                 let prev_outpoint = OutPoint { txid, vout: msg.prevtx_out };
 188                                 entry.insert(TxInputWithPrevOutput {
 189                                         input: TxIn {
 190                                                 previous_output: prev_outpoint,
 191                                                 sequence: Sequence(msg.sequence),
 192                                                 ..Default::default()
 193                                         },
 194                                         prev_output: prev_out,
 195                                 });
 196                                 self.prevtx_outpoints.insert(prev_outpoint);
 197                                 Ok(())
 198                         },
 199                 }
 200         }
 201
 202         fn received_tx_remove_input(&mut self, msg: &msgs::TxRemoveInput) -> Result<(), AbortReason> {
 203                 if !self.is_serial_id_valid_for_counterparty(&msg.serial_id) {
 204                         return Err(AbortReason::IncorrectSerialIdParity);
 205                 }
 206
 207                 self.inputs
 208                         .remove(&msg.serial_id)
 209                         // The receiving node:
 210                         //  - MUST fail the negotiation if:
 211                         //    - the input or output identified by the `serial_id` was not added by the sender
 212                         //    - the `serial_id` does not correspond to a currently added input
 213                         .ok_or(AbortReason::SerialIdUnknown)
 214                         .map(|_| ())
 215         }
 216
 217         fn received_tx_add_output(&mut self, msg: &msgs::TxAddOutput) -> Result<(), AbortReason> {
 218                 // The receiving node:
 219                 //  - MUST fail the negotiation if:
 220                 //     - the serial_id has the wrong parity
 221                 if !self.is_serial_id_valid_for_counterparty(&msg.serial_id) {
 222                         return Err(AbortReason::IncorrectSerialIdParity);
 223                 }
 224
 225                 self.received_tx_add_output_count += 1;
 226                 if self.received_tx_add_output_count > MAX_RECEIVED_TX_ADD_OUTPUT_COUNT {
 227                         // The receiving node:
 228                         //  - MUST fail the negotiation if:
 229                         //     - if has received 4096 `tx_add_output` messages during this negotiation
 230                         return Err(AbortReason::ReceivedTooManyTxAddOutputs);
 231                 }
 232
 233                 if msg.sats < msg.script.dust_value().to_sat() {
 234                         // The receiving node:
 235                         // - MUST fail the negotiation if:
 236                         //              - the sats amount is less than the dust_limit
 237                         return Err(AbortReason::BelowDustLimit);
 238                 }
 239
 240                 // Check that adding this output would not cause the total output value to exceed the total
 241                 // bitcoin supply.
 242                 let mut outputs_value: u64 = 0;
 243                 for output in self.outputs.iter() {
 244                         outputs_value = outputs_value.saturating_add(output.1.value);
 245                 }
 246                 if outputs_value.saturating_add(msg.sats) > TOTAL_BITCOIN_SUPPLY_SATOSHIS {
 247                         // The receiving node:
 248                         // - MUST fail the negotiation if:
 249                         //              - the sats amount is greater than 2,100,000,000,000,000 (TOTAL_BITCOIN_SUPPLY_SATOSHIS)
 250                         return Err(AbortReason::ExceededMaximumSatsAllowed);
 251                 }
 252
 253                 // The receiving node:
 254                 //   - MUST accept P2WSH, P2WPKH, P2TR scripts
 255                 //   - MAY fail the negotiation if script is non-standard
 256                 //
 257                 // We can actually be a bit looser than the above as only witness version 0 has special
 258                 // length-based standardness constraints to match similar consensus rules. All witness scripts
 259                 // with witness versions V1 and up are always considered standard. Yes, the scripts can be
 260                 // anyone-can-spend-able, but if our counterparty wants to add an output like that then it's none
 261                 // of our concern really ¯\_(ツ)_/¯
 262                 //
 263                 // TODO: The last check would be simplified when https://github.com/rust-bitcoin/rust-bitcoin/commit/1656e1a09a1959230e20af90d20789a4a8f0a31b
 264                 // hits the next release of rust-bitcoin.
 265                 if !(msg.script.is_v0_p2wpkh()
 266                         || msg.script.is_v0_p2wsh()
 267                         || (msg.script.is_witness_program()
 268                                 && msg.script.witness_version().map(|v| v.to_num() >= 1).unwrap_or(false)))
 269                 {
 270                         return Err(AbortReason::InvalidOutputScript);
 271                 }
 272
 273                 match self.outputs.entry(msg.serial_id) {
 274                         hash_map::Entry::Occupied(_) => {
 275                                 // The receiving node:
 276                                 //  - MUST fail the negotiation if:
 277                                 //    - the `serial_id` is already included in the transaction
 278                                 Err(AbortReason::DuplicateSerialId)
 279                         },
 280                         hash_map::Entry::Vacant(entry) => {
 281                                 entry.insert(TxOut { value: msg.sats, script_pubkey: msg.script.clone() });
 282                                 Ok(())
 283                         },
 284                 }
 285         }
 286
 287         fn received_tx_remove_output(&mut self, msg: &msgs::TxRemoveOutput) -> Result<(), AbortReason> {
 288                 if !self.is_serial_id_valid_for_counterparty(&msg.serial_id) {
 289                         return Err(AbortReason::IncorrectSerialIdParity);
 290                 }
 291                 if self.outputs.remove(&msg.serial_id).is_some() {
 292                         Ok(())
 293                 } else {
 294                         // The receiving node:
 295                         //  - MUST fail the negotiation if:
 296                         //    - the input or output identified by the `serial_id` was not added by the sender
 297                         //    - the `serial_id` does not correspond to a currently added input
 298                         Err(AbortReason::SerialIdUnknown)
 299                 }
 300         }
 301
 302         fn sent_tx_add_input(&mut self, msg: &msgs::TxAddInput) {
 303                 let tx = msg.prevtx.as_transaction();
 304                 let input = TxIn {
 305                         previous_output: OutPoint { txid: tx.txid(), vout: msg.prevtx_out },
 306                         sequence: Sequence(msg.sequence),
 307                         ..Default::default()
 308                 };
 309                 debug_assert!((msg.prevtx_out as usize) < tx.output.len());
 310                 let prev_output = &tx.output[msg.prevtx_out as usize];
 311                 self.prevtx_outpoints.insert(input.previous_output);
 312                 self.inputs.insert(
 313                         msg.serial_id,
 314                         TxInputWithPrevOutput { input, prev_output: prev_output.clone() },
 315                 );
 316         }
 317
 318         fn sent_tx_add_output(&mut self, msg: &msgs::TxAddOutput) {
 319                 self.outputs
 320                         .insert(msg.serial_id, TxOut { value: msg.sats, script_pubkey: msg.script.clone() });
 321         }
 322
 323         fn sent_tx_remove_input(&mut self, msg: &msgs::TxRemoveInput) {
 324                 self.inputs.remove(&msg.serial_id);
 325         }
 326
 327         fn sent_tx_remove_output(&mut self, msg: &msgs::TxRemoveOutput) {
 328                 self.outputs.remove(&msg.serial_id);
 329         }
 330
 331         fn build_transaction(self) -> Result<Transaction, AbortReason> {
 332                 // The receiving node:
 333                 // MUST fail the negotiation if:
 334
 335                 // - the peer's total input satoshis is less than their outputs
 336                 let mut counterparty_inputs_value: u64 = 0;
 337                 let mut counterparty_outputs_value: u64 = 0;
 338                 for input in self.counterparty_inputs_contributed() {
 339                         counterparty_inputs_value =
 340                                 counterparty_inputs_value.saturating_add(input.prev_output.value);
 341                 }
 342                 for output in self.counterparty_outputs_contributed() {
 343                         counterparty_outputs_value = counterparty_outputs_value.saturating_add(output.value);
 344                 }
 345                 if counterparty_inputs_value < counterparty_outputs_value {
 346                         return Err(AbortReason::OutputsValueExceedsInputsValue);
 347                 }
 348
 349                 // - there are more than 252 inputs
 350                 // - there are more than 252 outputs
 351                 if self.inputs.len() > MAX_INPUTS_OUTPUTS_COUNT
 352                         || self.outputs.len() > MAX_INPUTS_OUTPUTS_COUNT
 353                 {
 354                         return Err(AbortReason::ExceededNumberOfInputsOrOutputs);
 355                 }
 356
 357                 // TODO: How do we enforce their fees cover the witness without knowing its expected length?
 358                 const INPUT_WEIGHT: u64 = BASE_INPUT_WEIGHT + EMPTY_SCRIPT_SIG_WEIGHT;
 359
 360                 // - the peer's paid feerate does not meet or exceed the agreed feerate (based on the minimum fee).
 361                 let counterparty_output_weight_contributed: u64 = self
 362                         .counterparty_outputs_contributed()
 363                         .map(|output| {
 364                                 (8 /* value */ + output.script_pubkey.consensus_encode(&mut sink()).unwrap() as u64)
 365                                         * WITNESS_SCALE_FACTOR as u64
 366                         })
 367                         .sum();
 368                 let counterparty_weight_contributed = counterparty_output_weight_contributed
 369                         + self.counterparty_inputs_contributed().count() as u64 * INPUT_WEIGHT;
 370                 let counterparty_fees_contributed =
 371                         counterparty_inputs_value.saturating_sub(counterparty_outputs_value);
 372                 let mut required_counterparty_contribution_fee =
 373                         fee_for_weight(self.feerate_sat_per_kw, counterparty_weight_contributed);
 374                 if !self.holder_is_initiator {
 375                         // if is the non-initiator:
 376                         //      - the initiator's fees do not cover the common fields (version, segwit marker + flag,
 377                         //              input count, output count, locktime)
 378                         let tx_common_fields_weight =
 379                         (4 /* version */ + 4 /* locktime */ + 1 /* input count */ + 1 /* output count */) *
 380                             WITNESS_SCALE_FACTOR as u64 + 2 /* segwit marker + flag */;
 381                         let tx_common_fields_fee =
 382                                 fee_for_weight(self.feerate_sat_per_kw, tx_common_fields_weight);
 383                         required_counterparty_contribution_fee += tx_common_fields_fee;
 384                 }
 385                 if counterparty_fees_contributed < required_counterparty_contribution_fee {
 386                         return Err(AbortReason::InsufficientFees);
 387                 }
 388
 389                 // Inputs and outputs must be sorted by serial_id
 390                 let mut inputs = self.inputs.into_iter().collect::<Vec<_>>();
 391                 let mut outputs = self.outputs.into_iter().collect::<Vec<_>>();
 392                 inputs.sort_unstable_by_key(|(serial_id, _)| *serial_id);
 393                 outputs.sort_unstable_by_key(|(serial_id, _)| *serial_id);
 394
 395                 let tx_to_validate = Transaction {
 396                         version: 2,
 397                         lock_time: self.tx_locktime,
 398                         input: inputs.into_iter().map(|(_, input)| input.input).collect(),
 399                         output: outputs.into_iter().map(|(_, output)| output).collect(),
 400                 };
 401                 if tx_to_validate.weight().to_wu() > MAX_STANDARD_TX_WEIGHT as u64 {
 402                         return Err(AbortReason::TransactionTooLarge);
 403                 }
 404
 405                 Ok(tx_to_validate)
 406         }
 407 }
 408
 409 // The interactive transaction construction protocol allows two peers to collaboratively build a
 410 // transaction for broadcast.
 411 //
 412 // The protocol is turn-based, so we define different states here that we store depending on whose
 413 // turn it is to send the next message. The states are defined so that their types ensure we only
 414 // perform actions (only send messages) via defined state transitions that do not violate the
 415 // protocol.
 416 //
 417 // An example of a full negotiation and associated states follows:
 418 //
 419 //     +------------+                         +------------------+---- Holder state after message sent/received ----+
 420 //     |            |--(1)- tx_add_input ---->|                  |                  SentChangeMsg                   +
 421 //     |            |<-(2)- tx_complete ------|                  |                ReceivedTxComplete                +
 422 //     |            |--(3)- tx_add_output --->|                  |                  SentChangeMsg                   +
 423 //     |            |<-(4)- tx_complete ------|                  |                ReceivedTxComplete                +
 424 //     |            |--(5)- tx_add_input ---->|                  |                  SentChangeMsg                   +
 425 //     |   Holder   |<-(6)- tx_add_input -----|   Counterparty   |                ReceivedChangeMsg                 +
 426 //     |            |--(7)- tx_remove_output >|                  |                  SentChangeMsg                   +
 427 //     |            |<-(8)- tx_add_output ----|                  |                ReceivedChangeMsg                 +
 428 //     |            |--(9)- tx_complete ----->|                  |                  SentTxComplete                  +
 429 //     |            |<-(10) tx_complete ------|                  |                NegotiationComplete               +
 430 //     +------------+                         +------------------+--------------------------------------------------+
 431
 432 /// Negotiation states that can send & receive `tx_(add|remove)_(input|output)` and `tx_complete`
 433 trait State {}
 434
 435 /// Category of states where we have sent some message to the counterparty, and we are waiting for
 436 /// a response.
 437 trait SentMsgState: State {
 438         fn into_negotiation_context(self) -> NegotiationContext;
 439 }
 440
 441 /// Category of states that our counterparty has put us in after we receive a message from them.
 442 trait ReceivedMsgState: State {
 443         fn into_negotiation_context(self) -> NegotiationContext;
 444 }
 445
 446 // This macro is a helper for implementing the above state traits for various states subsequently
 447 // defined below the macro.
 448 macro_rules! define_state {
 449         (SENT_MSG_STATE, $state: ident, $doc: expr) => {
 450                 define_state!($state, NegotiationContext, $doc);
 451                 impl SentMsgState for $state {
 452                         fn into_negotiation_context(self) -> NegotiationContext {
 453                                 self.0
 454                         }
 455                 }
 456         };
 457         (RECEIVED_MSG_STATE, $state: ident, $doc: expr) => {
 458                 define_state!($state, NegotiationContext, $doc);
 459                 impl ReceivedMsgState for $state {
 460                         fn into_negotiation_context(self) -> NegotiationContext {
 461                                 self.0
 462                         }
 463                 }
 464         };
 465         ($state: ident, $inner: ident, $doc: expr) => {
 466                 #[doc = $doc]
 467                 #[derive(Debug)]
 468                 struct $state($inner);
 469                 impl State for $state {}
 470         };
 471 }
 472
 473 define_state!(
 474         SENT_MSG_STATE,
 475         SentChangeMsg,
 476         "We have sent a message to the counterparty that has affected our negotiation state."
 477 );
 478 define_state!(
 479         SENT_MSG_STATE,
 480         SentTxComplete,
 481         "We have sent a `tx_complete` message and are awaiting the counterparty's."
 482 );
 483 define_state!(
 484         RECEIVED_MSG_STATE,
 485         ReceivedChangeMsg,
 486         "We have received a message from the counterparty that has affected our negotiation state."
 487 );
 488 define_state!(
 489         RECEIVED_MSG_STATE,
 490         ReceivedTxComplete,
 491         "We have received a `tx_complete` message and the counterparty is awaiting ours."
 492 );
 493 define_state!(NegotiationComplete, Transaction, "We have exchanged consecutive `tx_complete` messages with the counterparty and the transaction negotiation is complete.");
 494 define_state!(
 495         NegotiationAborted,
 496         AbortReason,
 497         "The negotiation has failed and cannot be continued."
 498 );
 499
 500 type StateTransitionResult<S> = Result<S, AbortReason>;
 501
 502 trait StateTransition<NewState: State, TransitionData> {
 503         fn transition(self, data: TransitionData) -> StateTransitionResult<NewState>;
 504 }
 505
 506 // This macro helps define the legal transitions between the states above by implementing
 507 // the `StateTransition` trait for each of the states that follow this declaration.
 508 macro_rules! define_state_transitions {
 509         (SENT_MSG_STATE, [$(DATA $data: ty, TRANSITION $transition: ident),+]) => {
 510                 $(
 511                         impl<S: SentMsgState> StateTransition<ReceivedChangeMsg, $data> for S {
 512                                 fn transition(self, data: $data) -> StateTransitionResult<ReceivedChangeMsg> {
 513                                         let mut context = self.into_negotiation_context();
 514                                         context.$transition(data)?;
 515                                         Ok(ReceivedChangeMsg(context))
 516                                 }
 517                         }
 518                  )*
 519         };
 520         (RECEIVED_MSG_STATE, [$(DATA $data: ty, TRANSITION $transition: ident),+]) => {
 521                 $(
 522                         impl<S: ReceivedMsgState> StateTransition<SentChangeMsg, $data> for S {
 523                                 fn transition(self, data: $data) -> StateTransitionResult<SentChangeMsg> {
 524                                         let mut context = self.into_negotiation_context();
 525                                         context.$transition(data);
 526                                         Ok(SentChangeMsg(context))
 527                                 }
 528                         }
 529                  )*
 530         };
 531         (TX_COMPLETE, $from_state: ident, $tx_complete_state: ident) => {
 532                 impl StateTransition<NegotiationComplete, &msgs::TxComplete> for $tx_complete_state {
 533                         fn transition(self, _data: &msgs::TxComplete) -> StateTransitionResult<NegotiationComplete> {
 534                                 let context = self.into_negotiation_context();
 535                                 let tx = context.build_transaction()?;
 536                                 Ok(NegotiationComplete(tx))
 537                         }
 538                 }
 539
 540                 impl StateTransition<$tx_complete_state, &msgs::TxComplete> for $from_state {
 541                         fn transition(self, _data: &msgs::TxComplete) -> StateTransitionResult<$tx_complete_state> {
 542                                 Ok($tx_complete_state(self.into_negotiation_context()))
 543                         }
 544                 }
 545         };
 546 }
 547
 548 // State transitions when we have sent our counterparty some messages and are waiting for them
 549 // to respond.
 550 define_state_transitions!(SENT_MSG_STATE, [
 551         DATA &msgs::TxAddInput, TRANSITION received_tx_add_input,
 552         DATA &msgs::TxRemoveInput, TRANSITION received_tx_remove_input,
 553         DATA &msgs::TxAddOutput, TRANSITION received_tx_add_output,
 554         DATA &msgs::TxRemoveOutput, TRANSITION received_tx_remove_output
 555 ]);
 556 // State transitions when we have received some messages from our counterparty and we should
 557 // respond.
 558 define_state_transitions!(RECEIVED_MSG_STATE, [
 559         DATA &msgs::TxAddInput, TRANSITION sent_tx_add_input,
 560         DATA &msgs::TxRemoveInput, TRANSITION sent_tx_remove_input,
 561         DATA &msgs::TxAddOutput, TRANSITION sent_tx_add_output,
 562         DATA &msgs::TxRemoveOutput, TRANSITION sent_tx_remove_output
 563 ]);
 564 define_state_transitions!(TX_COMPLETE, SentChangeMsg, ReceivedTxComplete);
 565 define_state_transitions!(TX_COMPLETE, ReceivedChangeMsg, SentTxComplete);
 566
 567 #[derive(Debug)]
 568 enum StateMachine {
 569         Indeterminate,
 570         SentChangeMsg(SentChangeMsg),
 571         ReceivedChangeMsg(ReceivedChangeMsg),
 572         SentTxComplete(SentTxComplete),
 573         ReceivedTxComplete(ReceivedTxComplete),
 574         NegotiationComplete(NegotiationComplete),
 575         NegotiationAborted(NegotiationAborted),
 576 }
 577
 578 impl Default for StateMachine {
 579         fn default() -> Self {
 580                 Self::Indeterminate
 581         }
 582 }
 583
 584 // The `StateMachine` internally executes the actual transition between two states and keeps
 585 // track of the current state. This macro defines _how_ those state transitions happen to
 586 // update the internal state.
 587 macro_rules! define_state_machine_transitions {
 588         ($transition: ident, $msg: ty, [$(FROM $from_state: ident, TO $to_state: ident),+]) => {
 589                 fn $transition(self, msg: $msg) -> StateMachine {
 590                         match self {
 591                                 $(
 592                                         Self::$from_state(s) => match s.transition(msg) {
 593                                                 Ok(new_state) => StateMachine::$to_state(new_state),
 594                                                 Err(abort_reason) => StateMachine::NegotiationAborted(NegotiationAborted(abort_reason)),
 595                                         }
 596                                  )*
 597                                 _ => StateMachine::NegotiationAborted(NegotiationAborted(AbortReason::UnexpectedCounterpartyMessage)),
 598                         }
 599                 }
 600         };
 601 }
 602
 603 impl StateMachine {
 604         fn new(feerate_sat_per_kw: u32, is_initiator: bool, tx_locktime: AbsoluteLockTime) -> Self {
 605                 let context = NegotiationContext {
 606                         tx_locktime,
 607                         holder_is_initiator: is_initiator,
 608                         received_tx_add_input_count: 0,
 609                         received_tx_add_output_count: 0,
 610                         inputs: new_hash_map(),
 611                         prevtx_outpoints: new_hash_set(),
 612                         outputs: new_hash_map(),
 613                         feerate_sat_per_kw,
 614                 };
 615                 if is_initiator {
 616                         Self::ReceivedChangeMsg(ReceivedChangeMsg(context))
 617                 } else {
 618                         Self::SentChangeMsg(SentChangeMsg(context))
 619                 }
 620         }
 621
 622         // TxAddInput
 623         define_state_machine_transitions!(sent_tx_add_input, &msgs::TxAddInput, [
 624                 FROM ReceivedChangeMsg, TO SentChangeMsg,
 625                 FROM ReceivedTxComplete, TO SentChangeMsg
 626         ]);
 627         define_state_machine_transitions!(received_tx_add_input, &msgs::TxAddInput, [
 628                 FROM SentChangeMsg, TO ReceivedChangeMsg,
 629                 FROM SentTxComplete, TO ReceivedChangeMsg
 630         ]);
 631
 632         // TxAddOutput
 633         define_state_machine_transitions!(sent_tx_add_output, &msgs::TxAddOutput, [
 634                 FROM ReceivedChangeMsg, TO SentChangeMsg,
 635                 FROM ReceivedTxComplete, TO SentChangeMsg
 636         ]);
 637         define_state_machine_transitions!(received_tx_add_output, &msgs::TxAddOutput, [
 638                 FROM SentChangeMsg, TO ReceivedChangeMsg,
 639                 FROM SentTxComplete, TO ReceivedChangeMsg
 640         ]);
 641
 642         // TxRemoveInput
 643         define_state_machine_transitions!(sent_tx_remove_input, &msgs::TxRemoveInput, [
 644                 FROM ReceivedChangeMsg, TO SentChangeMsg,
 645                 FROM ReceivedTxComplete, TO SentChangeMsg
 646         ]);
 647         define_state_machine_transitions!(received_tx_remove_input, &msgs::TxRemoveInput, [
 648                 FROM SentChangeMsg, TO ReceivedChangeMsg,
 649                 FROM SentTxComplete, TO ReceivedChangeMsg
 650         ]);
 651
 652         // TxRemoveOutput
 653         define_state_machine_transitions!(sent_tx_remove_output, &msgs::TxRemoveOutput, [
 654                 FROM ReceivedChangeMsg, TO SentChangeMsg,
 655                 FROM ReceivedTxComplete, TO SentChangeMsg
 656         ]);
 657         define_state_machine_transitions!(received_tx_remove_output, &msgs::TxRemoveOutput, [
 658                 FROM SentChangeMsg, TO ReceivedChangeMsg,
 659                 FROM SentTxComplete, TO ReceivedChangeMsg
 660         ]);
 661
 662         // TxComplete
 663         define_state_machine_transitions!(sent_tx_complete, &msgs::TxComplete, [
 664                 FROM ReceivedChangeMsg, TO SentTxComplete,
 665                 FROM ReceivedTxComplete, TO NegotiationComplete
 666         ]);
 667         define_state_machine_transitions!(received_tx_complete, &msgs::TxComplete, [
 668                 FROM SentChangeMsg, TO ReceivedTxComplete,
 669                 FROM SentTxComplete, TO NegotiationComplete
 670         ]);
 671 }
 672
 673 pub struct InteractiveTxConstructor {
 674         state_machine: StateMachine,
 675         channel_id: ChannelId,
 676         inputs_to_contribute: Vec<(SerialId, TxIn, TransactionU16LenLimited)>,
 677         outputs_to_contribute: Vec<(SerialId, TxOut)>,
 678 }
 679
 680 pub enum InteractiveTxMessageSend {
 681         TxAddInput(msgs::TxAddInput),
 682         TxAddOutput(msgs::TxAddOutput),
 683         TxComplete(msgs::TxComplete),
 684 }
 685
 686 // This macro executes a state machine transition based on a provided action.
 687 macro_rules! do_state_transition {
 688         ($self: ident, $transition: ident, $msg: expr) => {{
 689                 let state_machine = core::mem::take(&mut $self.state_machine);
 690                 $self.state_machine = state_machine.$transition($msg);
 691                 match &$self.state_machine {
 692                         StateMachine::NegotiationAborted(state) => Err(state.0.clone()),
 693                         _ => Ok(()),
 694                 }
 695         }};
 696 }
 697
 698 fn generate_holder_serial_id<ES: Deref>(entropy_source: &ES, is_initiator: bool) -> SerialId
 699 where
 700         ES::Target: EntropySource,
 701 {
 702         let rand_bytes = entropy_source.get_secure_random_bytes();
 703         let mut serial_id_bytes = [0u8; 8];
 704         serial_id_bytes.copy_from_slice(&rand_bytes[..8]);
 705         let mut serial_id = u64::from_be_bytes(serial_id_bytes);
 706         if serial_id.is_for_initiator() != is_initiator {
 707                 serial_id ^= 1;
 708         }
 709         serial_id
 710 }
 711
 712 pub enum HandleTxCompleteValue {
 713         SendTxMessage(InteractiveTxMessageSend),
 714         SendTxComplete(InteractiveTxMessageSend, Transaction),
 715         NegotiationComplete(Transaction),
 716 }
 717
 718 impl InteractiveTxConstructor {
 719         /// Instantiates a new `InteractiveTxConstructor`.
 720         ///
 721         /// A tuple is returned containing the newly instantiate `InteractiveTxConstructor` and optionally
 722         /// an initial wrapped `Tx_` message which the holder needs to send to the counterparty.
 723         pub fn new<ES: Deref>(
 724                 entropy_source: &ES, channel_id: ChannelId, feerate_sat_per_kw: u32, is_initiator: bool,
 725                 funding_tx_locktime: AbsoluteLockTime,
 726                 inputs_to_contribute: Vec<(TxIn, TransactionU16LenLimited)>,
 727                 outputs_to_contribute: Vec<TxOut>,
 728         ) -> (Self, Option<InteractiveTxMessageSend>)
 729         where
 730                 ES::Target: EntropySource,
 731         {
 732                 let state_machine =
 733                         StateMachine::new(feerate_sat_per_kw, is_initiator, funding_tx_locktime);
 734                 let mut inputs_to_contribute: Vec<(SerialId, TxIn, TransactionU16LenLimited)> =
 735                         inputs_to_contribute
 736                                 .into_iter()
 737                                 .map(|(input, tx)| {
 738                                         let serial_id = generate_holder_serial_id(entropy_source, is_initiator);
 739                                         (serial_id, input, tx)
 740                                 })
 741                                 .collect();
 742                 // We'll sort by the randomly generated serial IDs, effectively shuffling the order of the inputs
 743                 // as the user passed them to us to avoid leaking any potential categorization of transactions
 744                 // before we pass any of the inputs to the counterparty.
 745                 inputs_to_contribute.sort_unstable_by_key(|(serial_id, _, _)| *serial_id);
 746                 let mut outputs_to_contribute: Vec<(SerialId, TxOut)> = outputs_to_contribute
 747                         .into_iter()
 748                         .map(|output| {
 749                                 let serial_id = generate_holder_serial_id(entropy_source, is_initiator);
 750                                 (serial_id, output)
 751                         })
 752                         .collect();
 753                 // In the same manner and for the same rationale as the inputs above, we'll shuffle the outputs.
 754                 outputs_to_contribute.sort_unstable_by_key(|(serial_id, _)| *serial_id);
 755                 let mut constructor =
 756                         Self { state_machine, channel_id, inputs_to_contribute, outputs_to_contribute };
 757                 let message_send = if is_initiator {
 758                         match constructor.maybe_send_message() {
 759                                 Ok(msg_send) => Some(msg_send),
 760                                 Err(_) => {
 761                                         debug_assert!(
 762                                                 false,
 763                                                 "We should always be able to start our state machine successfully"
 764                                         );
 765                                         None
 766                                 },
 767                         }
 768                 } else {
 769                         None
 770                 };
 771                 (constructor, message_send)
 772         }
 773
 774         fn maybe_send_message(&mut self) -> Result<InteractiveTxMessageSend, AbortReason> {
 775                 // We first attempt to send inputs we want to add, then outputs. Once we are done sending
 776                 // them both, then we always send tx_complete.
 777                 if let Some((serial_id, input, prevtx)) = self.inputs_to_contribute.pop() {
 778                         let msg = msgs::TxAddInput {
 779                                 channel_id: self.channel_id,
 780                                 serial_id,
 781                                 prevtx,
 782                                 prevtx_out: input.previous_output.vout,
 783                                 sequence: input.sequence.to_consensus_u32(),
 784                         };
 785                         do_state_transition!(self, sent_tx_add_input, &msg)?;
 786                         Ok(InteractiveTxMessageSend::TxAddInput(msg))
 787                 } else if let Some((serial_id, output)) = self.outputs_to_contribute.pop() {
 788                         let msg = msgs::TxAddOutput {
 789                                 channel_id: self.channel_id,
 790                                 serial_id,
 791                                 sats: output.value,
 792                                 script: output.script_pubkey,
 793                         };
 794                         do_state_transition!(self, sent_tx_add_output, &msg)?;
 795                         Ok(InteractiveTxMessageSend::TxAddOutput(msg))
 796                 } else {
 797                         let msg = msgs::TxComplete { channel_id: self.channel_id };
 798                         do_state_transition!(self, sent_tx_complete, &msg)?;
 799                         Ok(InteractiveTxMessageSend::TxComplete(msg))
 800                 }
 801         }
 802
 803         pub fn handle_tx_add_input(
 804                 &mut self, msg: &msgs::TxAddInput,
 805         ) -> Result<InteractiveTxMessageSend, AbortReason> {
 806                 do_state_transition!(self, received_tx_add_input, msg)?;
 807                 self.maybe_send_message()
 808         }
 809
 810         pub fn handle_tx_remove_input(
 811                 &mut self, msg: &msgs::TxRemoveInput,
 812         ) -> Result<InteractiveTxMessageSend, AbortReason> {
 813                 do_state_transition!(self, received_tx_remove_input, msg)?;
 814                 self.maybe_send_message()
 815         }
 816
 817         pub fn handle_tx_add_output(
 818                 &mut self, msg: &msgs::TxAddOutput,
 819         ) -> Result<InteractiveTxMessageSend, AbortReason> {
 820                 do_state_transition!(self, received_tx_add_output, msg)?;
 821                 self.maybe_send_message()
 822         }
 823
 824         pub fn handle_tx_remove_output(
 825                 &mut self, msg: &msgs::TxRemoveOutput,
 826         ) -> Result<InteractiveTxMessageSend, AbortReason> {
 827                 do_state_transition!(self, received_tx_remove_output, msg)?;
 828                 self.maybe_send_message()
 829         }
 830
 831         pub fn handle_tx_complete(
 832                 &mut self, msg: &msgs::TxComplete,
 833         ) -> Result<HandleTxCompleteValue, AbortReason> {
 834                 do_state_transition!(self, received_tx_complete, msg)?;
 835                 match &self.state_machine {
 836                         StateMachine::ReceivedTxComplete(_) => {
 837                                 let msg_send = self.maybe_send_message()?;
 838                                 match &self.state_machine {
 839                                         StateMachine::NegotiationComplete(s) => {
 840                                                 Ok(HandleTxCompleteValue::SendTxComplete(msg_send, s.0.clone()))
 841                                         },
 842                                         StateMachine::SentChangeMsg(_) => {
 843                                                 Ok(HandleTxCompleteValue::SendTxMessage(msg_send))
 844                                         }, // We either had an input or output to contribute.
 845                                         _ => {
 846                                                 debug_assert!(false, "We cannot transition to any other states after receiving `tx_complete` and responding");
 847                                                 Err(AbortReason::InvalidStateTransition)
 848                                         },
 849                                 }
 850                         },
 851                         StateMachine::NegotiationComplete(s) => {
 852                                 Ok(HandleTxCompleteValue::NegotiationComplete(s.0.clone()))
 853                         },
 854                         _ => {
 855                                 debug_assert!(
 856                                         false,
 857                                         "We cannot transition to any other states after receiving `tx_complete`"
 858                                 );
 859                                 Err(AbortReason::InvalidStateTransition)
 860                         },
 861                 }
 862         }
 863 }
 864
 865 #[cfg(test)]
 866 mod tests {
 867         use crate::chain::chaininterface::FEERATE_FLOOR_SATS_PER_KW;
 868         use crate::ln::channel::TOTAL_BITCOIN_SUPPLY_SATOSHIS;
 869         use crate::ln::interactivetxs::{
 870                 generate_holder_serial_id, AbortReason, HandleTxCompleteValue, InteractiveTxConstructor,
 871                 InteractiveTxMessageSend, MAX_INPUTS_OUTPUTS_COUNT, MAX_RECEIVED_TX_ADD_INPUT_COUNT,
 872                 MAX_RECEIVED_TX_ADD_OUTPUT_COUNT,
 873         };
 874         use crate::ln::ChannelId;
 875         use crate::sign::EntropySource;
 876         use crate::util::atomic_counter::AtomicCounter;
 877         use crate::util::ser::TransactionU16LenLimited;
 878         use bitcoin::blockdata::opcodes;
 879         use bitcoin::blockdata::script::Builder;
 880         use bitcoin::{
 881                 absolute::LockTime as AbsoluteLockTime, OutPoint, Sequence, Transaction, TxIn, TxOut,
 882         };
 883         use core::ops::Deref;
 884
 885         // A simple entropy source that works based on an atomic counter.
 886         struct TestEntropySource(AtomicCounter);
 887         impl EntropySource for TestEntropySource {
 888                 fn get_secure_random_bytes(&self) -> [u8; 32] {
 889                         let mut res = [0u8; 32];
 890                         let increment = self.0.get_increment();
 891                         for i in 0..32 {
 892                                 // Rotate the increment value by 'i' bits to the right, to avoid clashes
 893                                 // when `generate_local_serial_id` does a parity flip on consecutive calls for the
 894                                 // same party.
 895                                 let rotated_increment = increment.rotate_right(i as u32);
 896                                 res[i] = (rotated_increment & 0xff) as u8;
 897                         }
 898                         res
 899                 }
 900         }
 901
 902         // An entropy source that deliberately returns you the same seed every time. We use this
 903         // to test if the constructor would catch inputs/outputs that are attempting to be added
 904         // with duplicate serial ids.
 905         struct DuplicateEntropySource;
 906         impl EntropySource for DuplicateEntropySource {
 907                 fn get_secure_random_bytes(&self) -> [u8; 32] {
 908                         let mut res = [0u8; 32];
 909                         let count = 1u64;
 910                         res[0..8].copy_from_slice(&count.to_be_bytes());
 911                         res
 912                 }
 913         }
 914
 915         #[derive(Debug, PartialEq, Eq)]
 916         enum ErrorCulprit {
 917                 NodeA,
 918                 NodeB,
 919                 // Some error values are only checked at the end of the negotiation and are not easy to attribute
 920                 // to a particular party. Both parties would indicate an `AbortReason` in this case.
 921                 // e.g. Exceeded max inputs and outputs after negotiation.
 922                 Indeterminate,
 923         }
 924
 925         struct TestSession {
 926                 inputs_a: Vec<(TxIn, TransactionU16LenLimited)>,
 927                 outputs_a: Vec<TxOut>,
 928                 inputs_b: Vec<(TxIn, TransactionU16LenLimited)>,
 929                 outputs_b: Vec<TxOut>,
 930                 expect_error: Option<(AbortReason, ErrorCulprit)>,
 931         }
 932
 933         fn do_test_interactive_tx_constructor(session: TestSession) {
 934                 let entropy_source = TestEntropySource(AtomicCounter::new());
 935                 do_test_interactive_tx_constructor_internal(session, &&entropy_source);
 936         }
 937
 938         fn do_test_interactive_tx_constructor_with_entropy_source<ES: Deref>(
 939                 session: TestSession, entropy_source: ES,
 940         ) where
 941                 ES::Target: EntropySource,
 942         {
 943                 do_test_interactive_tx_constructor_internal(session, &entropy_source);
 944         }
 945
 946         fn do_test_interactive_tx_constructor_internal<ES: Deref>(
 947                 session: TestSession, entropy_source: &ES,
 948         ) where
 949                 ES::Target: EntropySource,
 950         {
 951                 let channel_id = ChannelId(entropy_source.get_secure_random_bytes());
 952                 let tx_locktime = AbsoluteLockTime::from_height(1337).unwrap();
 953
 954                 let (mut constructor_a, first_message_a) = InteractiveTxConstructor::new(
 955                         entropy_source,
 956                         channel_id,
 957                         FEERATE_FLOOR_SATS_PER_KW * 10,
 958                         true,
 959                         tx_locktime,
 960                         session.inputs_a,
 961                         session.outputs_a,
 962                 );
 963                 let (mut constructor_b, first_message_b) = InteractiveTxConstructor::new(
 964                         entropy_source,
 965                         channel_id,
 966                         FEERATE_FLOOR_SATS_PER_KW * 10,
 967                         false,
 968                         tx_locktime,
 969                         session.inputs_b,
 970                         session.outputs_b,
 971                 );
 972
 973                 let handle_message_send =
 974                         |msg: InteractiveTxMessageSend, for_constructor: &mut InteractiveTxConstructor| {
 975                                 match msg {
 976                                         InteractiveTxMessageSend::TxAddInput(msg) => for_constructor
 977                                                 .handle_tx_add_input(&msg)
 978                                                 .map(|msg_send| (Some(msg_send), None)),
 979                                         InteractiveTxMessageSend::TxAddOutput(msg) => for_constructor
 980                                                 .handle_tx_add_output(&msg)
 981                                                 .map(|msg_send| (Some(msg_send), None)),
 982                                         InteractiveTxMessageSend::TxComplete(msg) => {
 983                                                 for_constructor.handle_tx_complete(&msg).map(|value| match value {
 984                                                         HandleTxCompleteValue::SendTxMessage(msg_send) => {
 985                                                                 (Some(msg_send), None)
 986                                                         },
 987                                                         HandleTxCompleteValue::SendTxComplete(msg_send, tx) => {
 988                                                                 (Some(msg_send), Some(tx))
 989                                                         },
 990                                                         HandleTxCompleteValue::NegotiationComplete(tx) => (None, Some(tx)),
 991                                                 })
 992                                         },
 993                                 }
 994                         };
 995
 996                 assert!(first_message_b.is_none());
 997                 let mut message_send_a = first_message_a;
 998                 let mut message_send_b = None;
 999                 let mut final_tx_a = None;
1000                 let mut final_tx_b = None;
1001                 while final_tx_a.is_none() || final_tx_b.is_none() {
1002                         if let Some(message_send_a) = message_send_a.take() {
1003                                 match handle_message_send(message_send_a, &mut constructor_b) {
1004                                         Ok((msg_send, final_tx)) => {
1005                                                 message_send_b = msg_send;
1006                                                 final_tx_b = final_tx;
1007                                         },
1008                                         Err(abort_reason) => {
1009                                                 let error_culprit = match abort_reason {
1010                                                         AbortReason::ExceededNumberOfInputsOrOutputs => {
1011                                                                 ErrorCulprit::Indeterminate
1012                                                         },
1013                                                         _ => ErrorCulprit::NodeA,
1014                                                 };
1015                                                 assert_eq!(Some((abort_reason, error_culprit)), session.expect_error);
1016                                                 assert!(message_send_b.is_none());
1017                                                 return;
1018                                         },
1019                                 }
1020                         }
1021                         if let Some(message_send_b) = message_send_b.take() {
1022                                 match handle_message_send(message_send_b, &mut constructor_a) {
1023                                         Ok((msg_send, final_tx)) => {
1024                                                 message_send_a = msg_send;
1025                                                 final_tx_a = final_tx;
1026                                         },
1027                                         Err(abort_reason) => {
1028                                                 let error_culprit = match abort_reason {
1029                                                         AbortReason::ExceededNumberOfInputsOrOutputs => {
1030                                                                 ErrorCulprit::Indeterminate
1031                                                         },
1032                                                         _ => ErrorCulprit::NodeB,
1033                                                 };
1034                                                 assert_eq!(Some((abort_reason, error_culprit)), session.expect_error);
1035                                                 assert!(message_send_a.is_none());
1036                                                 return;
1037                                         },
1038                                 }
1039                         }
1040                 }
1041                 assert!(message_send_a.is_none());
1042                 assert!(message_send_b.is_none());
1043                 assert_eq!(final_tx_a, final_tx_b);
1044                 assert!(session.expect_error.is_none());
1045         }
1046
1047         fn generate_tx(values: &[u64]) -> Transaction {
1048                 generate_tx_with_locktime(values, 1337)
1049         }
1050
1051         fn generate_tx_with_locktime(values: &[u64], locktime: u32) -> Transaction {
1052                 Transaction {
1053                         version: 2,
1054                         lock_time: AbsoluteLockTime::from_height(locktime).unwrap(),
1055                         input: vec![TxIn { ..Default::default() }],
1056                         output: values
1057                                 .iter()
1058                                 .map(|value| TxOut {
1059                                         value: *value,
1060                                         script_pubkey: Builder::new()
1061                                                 .push_opcode(opcodes::OP_TRUE)
1062                                                 .into_script()
1063                                                 .to_v0_p2wsh(),
1064                                 })
1065                                 .collect(),
1066                 }
1067         }
1068
1069         fn generate_inputs(values: &[u64]) -> Vec<(TxIn, TransactionU16LenLimited)> {
1070                 let tx = generate_tx(values);
1071                 let txid = tx.txid();
1072                 tx.output
1073                         .iter()
1074                         .enumerate()
1075                         .map(|(idx, _)| {
1076                                 let input = TxIn {
1077                                         previous_output: OutPoint { txid, vout: idx as u32 },
1078                                         script_sig: Default::default(),
1079                                         sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
1080                                         witness: Default::default(),
1081                                 };
1082                                 (input, TransactionU16LenLimited::new(tx.clone()).unwrap())
1083                         })
1084                         .collect()
1085         }
1086
1087         fn generate_outputs(values: &[u64]) -> Vec<TxOut> {
1088                 values
1089                         .iter()
1090                         .map(|value| TxOut {
1091                                 value: *value,
1092                                 script_pubkey: Builder::new()
1093                                         .push_opcode(opcodes::OP_TRUE)
1094                                         .into_script()
1095                                         .to_v0_p2wsh(),
1096                         })
1097                         .collect()
1098         }
1099
1100         fn generate_fixed_number_of_inputs(count: u16) -> Vec<(TxIn, TransactionU16LenLimited)> {
1101                 // Generate transactions with a total `count` number of outputs such that no transaction has a
1102                 // serialized length greater than u16::MAX.
1103                 let max_outputs_per_prevtx = 1_500;
1104                 let mut remaining = count;
1105                 let mut inputs: Vec<(TxIn, TransactionU16LenLimited)> = Vec::with_capacity(count as usize);
1106
1107                 while remaining > 0 {
1108                         let tx_output_count = remaining.min(max_outputs_per_prevtx);
1109                         remaining -= tx_output_count;
1110
1111                         // Use unique locktime for each tx so outpoints are different across transactions
1112                         let tx = generate_tx_with_locktime(
1113                                 &vec![1_000_000; tx_output_count as usize],
1114                                 (1337 + remaining).into(),
1115                         );
1116                         let txid = tx.txid();
1117
1118                         let mut temp: Vec<(TxIn, TransactionU16LenLimited)> = tx
1119                                 .output
1120                                 .iter()
1121                                 .enumerate()
1122                                 .map(|(idx, _)| {
1123                                         let input = TxIn {
1124                                                 previous_output: OutPoint { txid, vout: idx as u32 },
1125                                                 script_sig: Default::default(),
1126                                                 sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
1127                                                 witness: Default::default(),
1128                                         };
1129                                         (input, TransactionU16LenLimited::new(tx.clone()).unwrap())
1130                                 })
1131                                 .collect();
1132
1133                         inputs.append(&mut temp);
1134                 }
1135
1136                 inputs
1137         }
1138
1139         fn generate_fixed_number_of_outputs(count: u16) -> Vec<TxOut> {
1140                 // Set a constant value for each TxOut
1141                 generate_outputs(&vec![1_000_000; count as usize])
1142         }
1143
1144         fn generate_non_witness_output(value: u64) -> TxOut {
1145                 TxOut {
1146                         value,
1147                         script_pubkey: Builder::new().push_opcode(opcodes::OP_TRUE).into_script().to_p2sh(),
1148                 }
1149         }
1150
1151         #[test]
1152         fn test_interactive_tx_constructor() {
1153                 // No contributions.
1154                 do_test_interactive_tx_constructor(TestSession {
1155                         inputs_a: vec![],
1156                         outputs_a: vec![],
1157                         inputs_b: vec![],
1158                         outputs_b: vec![],
1159                         expect_error: Some((AbortReason::InsufficientFees, ErrorCulprit::NodeA)),
1160                 });
1161                 // Single contribution, no initiator inputs.
1162                 do_test_interactive_tx_constructor(TestSession {
1163                         inputs_a: vec![],
1164                         outputs_a: generate_outputs(&[1_000_000]),
1165                         inputs_b: vec![],
1166                         outputs_b: vec![],
1167                         expect_error: Some((AbortReason::OutputsValueExceedsInputsValue, ErrorCulprit::NodeA)),
1168                 });
1169                 // Single contribution, no initiator outputs.
1170                 do_test_interactive_tx_constructor(TestSession {
1171                         inputs_a: generate_inputs(&[1_000_000]),
1172                         outputs_a: vec![],
1173                         inputs_b: vec![],
1174                         outputs_b: vec![],
1175                         expect_error: None,
1176                 });
1177                 // Single contribution, insufficient fees.
1178                 do_test_interactive_tx_constructor(TestSession {
1179                         inputs_a: generate_inputs(&[1_000_000]),
1180                         outputs_a: generate_outputs(&[1_000_000]),
1181                         inputs_b: vec![],
1182                         outputs_b: vec![],
1183                         expect_error: Some((AbortReason::InsufficientFees, ErrorCulprit::NodeA)),
1184                 });
1185                 // Initiator contributes sufficient fees, but non-initiator does not.
1186                 do_test_interactive_tx_constructor(TestSession {
1187                         inputs_a: generate_inputs(&[1_000_000]),
1188                         outputs_a: vec![],
1189                         inputs_b: generate_inputs(&[100_000]),
1190                         outputs_b: generate_outputs(&[100_000]),
1191                         expect_error: Some((AbortReason::InsufficientFees, ErrorCulprit::NodeB)),
1192                 });
1193                 // Multi-input-output contributions from both sides.
1194                 do_test_interactive_tx_constructor(TestSession {
1195                         inputs_a: generate_inputs(&[1_000_000, 1_000_000]),
1196                         outputs_a: generate_outputs(&[1_000_000, 200_000]),
1197                         inputs_b: generate_inputs(&[1_000_000, 500_000]),
1198                         outputs_b: generate_outputs(&[1_000_000, 400_000]),
1199                         expect_error: None,
1200                 });
1201
1202                 // Prevout from initiator is not a witness program
1203                 let non_segwit_output_tx = {
1204                         let mut tx = generate_tx(&[1_000_000]);
1205                         tx.output.push(TxOut {
1206                                 script_pubkey: Builder::new()
1207                                         .push_opcode(opcodes::all::OP_RETURN)
1208                                         .into_script()
1209                                         .to_p2sh(),
1210                                 ..Default::default()
1211                         });
1212
1213                         TransactionU16LenLimited::new(tx).unwrap()
1214                 };
1215                 let non_segwit_input = TxIn {
1216                         previous_output: OutPoint {
1217                                 txid: non_segwit_output_tx.as_transaction().txid(),
1218                                 vout: 1,
1219                         },
1220                         sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
1221                         ..Default::default()
1222                 };
1223                 do_test_interactive_tx_constructor(TestSession {
1224                         inputs_a: vec![(non_segwit_input, non_segwit_output_tx)],
1225                         outputs_a: vec![],
1226                         inputs_b: vec![],
1227                         outputs_b: vec![],
1228                         expect_error: Some((AbortReason::PrevTxOutInvalid, ErrorCulprit::NodeA)),
1229                 });
1230
1231                 // Invalid input sequence from initiator.
1232                 let tx = TransactionU16LenLimited::new(generate_tx(&[1_000_000])).unwrap();
1233                 let invalid_sequence_input = TxIn {
1234                         previous_output: OutPoint { txid: tx.as_transaction().txid(), vout: 0 },
1235                         ..Default::default()
1236                 };
1237                 do_test_interactive_tx_constructor(TestSession {
1238                         inputs_a: vec![(invalid_sequence_input, tx.clone())],
1239                         outputs_a: generate_outputs(&[1_000_000]),
1240                         inputs_b: vec![],
1241                         outputs_b: vec![],
1242                         expect_error: Some((AbortReason::IncorrectInputSequenceValue, ErrorCulprit::NodeA)),
1243                 });
1244                 // Duplicate prevout from initiator.
1245                 let duplicate_input = TxIn {
1246                         previous_output: OutPoint { txid: tx.as_transaction().txid(), vout: 0 },
1247                         sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
1248                         ..Default::default()
1249                 };
1250                 do_test_interactive_tx_constructor(TestSession {
1251                         inputs_a: vec![(duplicate_input.clone(), tx.clone()), (duplicate_input, tx.clone())],
1252                         outputs_a: generate_outputs(&[1_000_000]),
1253                         inputs_b: vec![],
1254                         outputs_b: vec![],
1255                         expect_error: Some((AbortReason::PrevTxOutInvalid, ErrorCulprit::NodeA)),
1256                 });
1257                 // Non-initiator uses same prevout as initiator.
1258                 let duplicate_input = TxIn {
1259                         previous_output: OutPoint { txid: tx.as_transaction().txid(), vout: 0 },
1260                         sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
1261                         ..Default::default()
1262                 };
1263                 do_test_interactive_tx_constructor(TestSession {
1264                         inputs_a: vec![(duplicate_input.clone(), tx.clone())],
1265                         outputs_a: generate_outputs(&[1_000_000]),
1266                         inputs_b: vec![(duplicate_input.clone(), tx.clone())],
1267                         outputs_b: vec![],
1268                         expect_error: Some((AbortReason::PrevTxOutInvalid, ErrorCulprit::NodeB)),
1269                 });
1270                 // Initiator sends too many TxAddInputs
1271                 do_test_interactive_tx_constructor(TestSession {
1272                         inputs_a: generate_fixed_number_of_inputs(MAX_RECEIVED_TX_ADD_INPUT_COUNT + 1),
1273                         outputs_a: vec![],
1274                         inputs_b: vec![],
1275                         outputs_b: vec![],
1276                         expect_error: Some((AbortReason::ReceivedTooManyTxAddInputs, ErrorCulprit::NodeA)),
1277                 });
1278                 // Attempt to queue up two inputs with duplicate serial ids. We use a deliberately bad
1279                 // entropy source, `DuplicateEntropySource` to simulate this.
1280                 do_test_interactive_tx_constructor_with_entropy_source(
1281                         TestSession {
1282                                 inputs_a: generate_fixed_number_of_inputs(2),
1283                                 outputs_a: vec![],
1284                                 inputs_b: vec![],
1285                                 outputs_b: vec![],
1286                                 expect_error: Some((AbortReason::DuplicateSerialId, ErrorCulprit::NodeA)),
1287                         },
1288                         &DuplicateEntropySource,
1289                 );
1290                 // Initiator sends too many TxAddOutputs.
1291                 do_test_interactive_tx_constructor(TestSession {
1292                         inputs_a: vec![],
1293                         outputs_a: generate_fixed_number_of_outputs(MAX_RECEIVED_TX_ADD_OUTPUT_COUNT + 1),
1294                         inputs_b: vec![],
1295                         outputs_b: vec![],
1296                         expect_error: Some((AbortReason::ReceivedTooManyTxAddOutputs, ErrorCulprit::NodeA)),
1297                 });
1298                 // Initiator sends an output below dust value.
1299                 do_test_interactive_tx_constructor(TestSession {
1300                         inputs_a: vec![],
1301                         outputs_a: generate_outputs(&[1]),
1302                         inputs_b: vec![],
1303                         outputs_b: vec![],
1304                         expect_error: Some((AbortReason::BelowDustLimit, ErrorCulprit::NodeA)),
1305                 });
1306                 // Initiator sends an output above maximum sats allowed.
1307                 do_test_interactive_tx_constructor(TestSession {
1308                         inputs_a: vec![],
1309                         outputs_a: generate_outputs(&[TOTAL_BITCOIN_SUPPLY_SATOSHIS + 1]),
1310                         inputs_b: vec![],
1311                         outputs_b: vec![],
1312                         expect_error: Some((AbortReason::ExceededMaximumSatsAllowed, ErrorCulprit::NodeA)),
1313                 });
1314                 // Initiator sends an output without a witness program.
1315                 do_test_interactive_tx_constructor(TestSession {
1316                         inputs_a: vec![],
1317                         outputs_a: vec![generate_non_witness_output(1_000_000)],
1318                         inputs_b: vec![],
1319                         outputs_b: vec![],
1320                         expect_error: Some((AbortReason::InvalidOutputScript, ErrorCulprit::NodeA)),
1321                 });
1322                 // Attempt to queue up two outputs with duplicate serial ids. We use a deliberately bad
1323                 // entropy source, `DuplicateEntropySource` to simulate this.
1324                 do_test_interactive_tx_constructor_with_entropy_source(
1325                         TestSession {
1326                                 inputs_a: vec![],
1327                                 outputs_a: generate_fixed_number_of_outputs(2),
1328                                 inputs_b: vec![],
1329                                 outputs_b: vec![],
1330                                 expect_error: Some((AbortReason::DuplicateSerialId, ErrorCulprit::NodeA)),
1331                         },
1332                         &DuplicateEntropySource,
1333                 );
1334
1335                 // Peer contributed more output value than inputs
1336                 do_test_interactive_tx_constructor(TestSession {
1337                         inputs_a: generate_inputs(&[100_000]),
1338                         outputs_a: generate_outputs(&[1_000_000]),
1339                         inputs_b: vec![],
1340                         outputs_b: vec![],
1341                         expect_error: Some((AbortReason::OutputsValueExceedsInputsValue, ErrorCulprit::NodeA)),
1342                 });
1343
1344                 // Peer contributed more than allowed number of inputs.
1345                 do_test_interactive_tx_constructor(TestSession {
1346                         inputs_a: generate_fixed_number_of_inputs(MAX_INPUTS_OUTPUTS_COUNT as u16 + 1),
1347                         outputs_a: vec![],
1348                         inputs_b: vec![],
1349                         outputs_b: vec![],
1350                         expect_error: Some((
1351                                 AbortReason::ExceededNumberOfInputsOrOutputs,
1352                                 ErrorCulprit::Indeterminate,
1353                         )),
1354                 });
1355                 // Peer contributed more than allowed number of outputs.
1356                 do_test_interactive_tx_constructor(TestSession {
1357                         inputs_a: generate_inputs(&[TOTAL_BITCOIN_SUPPLY_SATOSHIS]),
1358                         outputs_a: generate_fixed_number_of_outputs(MAX_INPUTS_OUTPUTS_COUNT as u16 + 1),
1359                         inputs_b: vec![],
1360                         outputs_b: vec![],
1361                         expect_error: Some((
1362                                 AbortReason::ExceededNumberOfInputsOrOutputs,
1363                                 ErrorCulprit::Indeterminate,
1364                         )),
1365                 });
1366         }
1367
1368         #[test]
1369         fn test_generate_local_serial_id() {
1370                 let entropy_source = TestEntropySource(AtomicCounter::new());
1371
1372                 // Initiators should have even serial id, non-initiators should have odd serial id.
1373                 assert_eq!(generate_holder_serial_id(&&entropy_source, true) % 2, 0);
1374                 assert_eq!(generate_holder_serial_id(&&entropy_source, false) % 2, 1)
1375         }
1376 }