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BtcSwapTx: remove utxo field, update struct methods
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The BtcSwapTx methods are updated to use all available
inputs, where appropriate.
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@ok300
ok300 committed Sep 16, 2024
1 parent d68cb62 commit 3587e3c
Showing 1 changed file with 106 additions and 93 deletions.
199 changes: 106 additions & 93 deletions src/swaps/bitcoin.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -500,13 +500,9 @@ pub struct BtcSwapTx {
pub kind: SwapTxKind, // These fields needs to be public to do manual creation in IT.
pub swap_script: BtcSwapScript,
pub output_address: Address,
/// The first utxo for the script_pubkey, in (Outpoint, Amount) format
pub utxo: (OutPoint, TxOut),

/// All utxos for the script_pubkey of this swap:
/// - the initial lockup utxo, if not yet refunded claimed or refunded
/// TODO: how to reflect this in utxo field above? Optional?
/// - any further utxos, if not yet refunded
/// All utxos for the script_pubkey of this swap, at this point in time:
/// - the initial lockup utxo, if not yet spent (claimed or refunded)
/// - any further utxos, if not yet spent
pub utxos: Vec<(OutPoint, TxOut)>,
}

Expand Down Expand Up @@ -549,7 +545,6 @@ impl BtcSwapTx {
kind: SwapTxKind::Claim,
swap_script,
output_address: address.assume_checked(),
utxo: utxo.clone(),
utxos: vec![utxo], // When claiming, we only consider the first utxo
})
} else {
Expand Down Expand Up @@ -585,29 +580,34 @@ impl BtcSwapTx {
return Err(Error::Address("Address validation failed".to_string()));
};

let utxo_infos = swap_script.fetch_utxos(&network_config)?;
let utxo_info = match swap_script.fetch_utxo(&network_config) {
Ok(r) => r,
Err(_) => swap_script.fetch_lockup_utxo_boltz(
&network_config,
&boltz_url,
&swap_id,
SwapTxKind::Refund,
)?,
let utxos_temp = swap_script.fetch_utxos(&network_config)?;
let utxos_final = match utxos_temp.is_empty() {
true => {
let lockup_utxo_info = swap_script.fetch_lockup_utxo_boltz(
&network_config,
&boltz_url,
&swap_id,
SwapTxKind::Refund,
)?;

match lockup_utxo_info {
Some(r) => vec![r],
None => vec![],
}
}
false => utxos_temp,
};

if let Some(utxo) = utxo_info {
Ok(BtcSwapTx {
match utxos_final.is_empty() {
true => Err(Error::Protocol(
"No Bitcoin UTXO detected for this script".to_string(),
)),
false => Ok(BtcSwapTx {
kind: SwapTxKind::Refund,
swap_script,
output_address: address.assume_checked(),
utxo,
utxos: utxo_infos,
})
} else {
Err(Error::Protocol(
"No Bitcoin UTXO detected for this script".to_string(),
))
utxos: utxos_final,
}),
}
}

Expand Down Expand Up @@ -692,8 +692,12 @@ impl BtcSwapTx {
)));
};

// For claim, we only consider 1 utxo
let utxo = self.utxos.first().ok_or(Error::Protocol(
"No Bitcoin UTXO detected for this script".to_string(),
))?;
let txin = TxIn {
previous_output: self.utxo.0,
previous_output: utxo.0,
sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
script_sig: ScriptBuf::new(),
witness: Witness::new(),
Expand All @@ -703,7 +707,7 @@ impl BtcSwapTx {

let txout = TxOut {
script_pubkey: destination_spk,
value: Amount::from_sat(self.utxo.1.value.to_sat() - absolute_fees),
value: Amount::from_sat(utxo.1.value.to_sat() - absolute_fees),
};

let mut claim_tx = Transaction {
Expand All @@ -728,7 +732,7 @@ impl BtcSwapTx {
let claim_tx_taproot_hash = SighashCache::new(claim_tx.clone())
.taproot_key_spend_signature_hash(
0,
&Prevouts::All(&[&self.utxo.1]),
&Prevouts::All(&[&utxo.1]),
bitcoin::TapSighashType::Default,
)?;

Expand Down Expand Up @@ -844,7 +848,7 @@ impl BtcSwapTx {

let sighash = SighashCache::new(claim_tx.clone()).taproot_script_spend_signature_hash(
0,
&Prevouts::All(&[&self.utxo.1]),
&Prevouts::All(&[&utxo.1]),
leaf_hash,
TapSighashType::Default,
)?;
Expand Down Expand Up @@ -897,33 +901,6 @@ impl BtcSwapTx {
));
}

// let unsigned_input: TxIn = TxIn {
// sequence: Sequence::ZERO, // enables absolute locktime
// previous_output: self.utxo.0,
// script_sig: ScriptBuf::new(),
// witness: Witness::new(),
// };
let utxos_amount = self
.utxos
.iter()
.fold(Amount::ZERO, |acc, (_, txo)| acc + txo.value);
let output_amount: Amount = utxos_amount - Amount::from_sat(absolute_fees);
let output: TxOut = TxOut {
script_pubkey: self.output_address.script_pubkey(),
value: output_amount,
};

let inputs = self
.utxos
.iter()
.map(|(outpoint, _txo)| TxIn {
previous_output: outpoint.clone(),
script_sig: ScriptBuf::new(),
sequence: Sequence::MAX,
witness: Witness::new(),
})
.collect();

let lock_time = match self
.swap_script
.refund_script()
Expand Down Expand Up @@ -952,27 +929,56 @@ impl BtcSwapTx {
}
};

let mut refund_tx = Transaction {
version: Version::TWO,
lock_time,
input: inputs,
output: vec![output],
let build_refund_tx_from_utxos = |utxos: &Vec<(OutPoint, TxOut)>| {
let utxos_amount = utxos
.iter()
.fold(Amount::ZERO, |acc, (_, txo)| acc + txo.value);
let output_amount: Amount = utxos_amount - Amount::from_sat(absolute_fees);
let output: TxOut = TxOut {
script_pubkey: self.output_address.script_pubkey(),
value: output_amount,
};

let unsigned_inputs = self
.utxos
.iter()
.map(|(outpoint, _txo)| TxIn {
previous_output: outpoint.clone(),
script_sig: ScriptBuf::new(),
sequence: Sequence::MAX,
witness: Witness::new(),
})
.collect();

Transaction {
version: Version::TWO,
lock_time,
input: unsigned_inputs,
output: vec![output],
}
};

let secp = Secp256k1::new();

if let Some(Cooperative {
let refund_tx = if let Some(Cooperative {
boltz_api, swap_id, ..
}) = is_cooperative
{
// Start the Musig session
refund_tx.lock_time = LockTime::ZERO; // No locktime for cooperative spend

// For cooperative refund, we only consider 1 utxo (the first)
let utxo = self.utxos.first().cloned().ok_or(Error::Protocol(
"No Bitcoin UTXO detected for this script".to_string(),
))?;
let mut refund_tx_cooperative = build_refund_tx_from_utxos(&vec![utxo.clone()]);

refund_tx_cooperative.lock_time = LockTime::ZERO; // No locktime for cooperative spend

// Step 1: Get the sighash
let refund_tx_taproot_hash = SighashCache::new(refund_tx.clone())
let refund_tx_taproot_hash = SighashCache::new(refund_tx_cooperative.clone())
.taproot_key_spend_signature_hash(
0,
&Prevouts::All(&[&self.utxo.1]),
&Prevouts::All(&[&utxo.1]),
bitcoin::TapSighashType::Default,
)?;

Expand Down Expand Up @@ -1005,7 +1011,7 @@ impl BtcSwapTx {
)?;

// Step 7: Get boltz's partial sig
let refund_tx_hex = serialize(&refund_tx).to_lower_hex_string();
let refund_tx_hex = serialize(&refund_tx_cooperative).to_lower_hex_string();
let partial_sig_resp = match self.swap_script.swap_type {
SwapType::Chain => {
boltz_api.get_chain_partial_sig(&swap_id, &pub_nonce, &refund_tx_hex)
Expand Down Expand Up @@ -1062,48 +1068,55 @@ impl BtcSwapTx {

let mut witness = Witness::new();
witness.push(final_schnorr_sig.to_vec());
refund_tx_cooperative.input[0].witness = witness;

refund_tx.input[0].witness = witness;
refund_tx_cooperative
} else {
refund_tx.input[0].sequence = Sequence::ZERO;
let mut refund_tx_non_cooperative = build_refund_tx_from_utxos(&self.utxos);

let leaf_hash =
TapLeafHash::from_script(&self.swap_script.refund_script(), LeafVersion::TapScript);

let sighash = SighashCache::new(refund_tx.clone())
.taproot_script_spend_signature_hash(
0,
&Prevouts::All(&[&self.utxo.1]),
leaf_hash,
TapSighashType::Default,
)?;

let msg = Message::from_digest_slice(sighash.as_byte_array())?;

let sig = Secp256k1::new().sign_schnorr(&msg, &keys);

let final_sig = Signature {
sig,
hash_ty: TapSighashType::Default,
};

let control_block = self
.swap_script
.taproot_spendinfo()?
.control_block(&(
self.swap_script.refund_script().clone(),
LeafVersion::TapScript,
))
.expect("Control block calculation failed");
.ok_or(Error::Protocol(
"Control block calculation failed".to_string(),
))?;

let mut witness = Witness::new();
for input_index in 0..refund_tx_non_cooperative.input.len() {
refund_tx_non_cooperative.input[input_index].sequence = Sequence::ZERO;

witness.push(final_sig.to_vec());
witness.push(self.swap_script.refund_script().as_bytes());
witness.push(control_block.serialize());
let sighash = SighashCache::new(refund_tx_non_cooperative.clone())
.taproot_script_spend_signature_hash(
input_index,
&Prevouts::All(&[&self.utxos[input_index].1]),
leaf_hash,
TapSighashType::Default,
)?;

refund_tx.input[0].witness = witness;
}
let msg = Message::from_digest_slice(sighash.as_byte_array())?;

let sig = Secp256k1::new().sign_schnorr(&msg, &keys);

let final_sig = Signature {
sig,
hash_ty: TapSighashType::Default,
};

let mut witness = Witness::new();
witness.push(final_sig.to_vec());
witness.push(self.swap_script.refund_script().as_bytes());
witness.push(control_block.serialize());
refund_tx_non_cooperative.input[input_index].witness = witness;
}

refund_tx_non_cooperative
};

Ok(refund_tx)
}
Expand Down

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