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fuzzamoto-ir: implement BuildPayToBareMulti #129

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1 change: 1 addition & 0 deletions doc/src/design/ir.md
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Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,7 @@ containing the correctly serialized transactions `v15` and `v30`.
| `BuildPayToScriptHash` | Creates a P2SH script. |
| `BuildOpReturnScripts`| Creates an OP_RETURN script. |
| `BuildPayToAnchor` | Creates a P2A (pay-to-anchor) script for CPFP. |
| `BuildPayToBareMulti` | Creates a bare m-of-n multisig script. |
| **Witness stack**| **Construct a witness stack.** |
| `BeginWitnessStack`| Begins building a witness stack. |
| `AddWitness` | Adds an item to the witness stack. |
Expand Down
139 changes: 138 additions & 1 deletion fuzzamoto-ir/src/compiler.rs
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Expand Up @@ -191,6 +191,11 @@ enum SigningRequest {
private_key_var: usize,
sighash_var: usize,
},
BareMulti {
required: u8,
private_keys: Vec<[u8; 32]>,
sighash_var: usize,
},
Taproot {
spend_info_var: Option<usize>,
selected_leaf: Option<TaprootLeaf>,
Expand Down Expand Up @@ -424,6 +429,7 @@ impl Compiler {
| Operation::BuildPayToPubKey
| Operation::BuildPayToPubKeyHash
| Operation::BuildPayToWitnessPubKeyHash
| Operation::BuildPayToBareMulti { .. }
| Operation::BuildPayToTaproot => {
self.handle_script_building_operations(instruction)?;
}
Expand Down Expand Up @@ -1054,6 +1060,49 @@ impl Compiler {
requires_signing: None,
});
}
Operation::BuildPayToBareMulti {
required,
private_keys,
} => {
let _sighash_flags_var = self.get_input::<u8>(&instruction.inputs, 0)?;
let sighash_var = instruction
.inputs
.first()
.copied()
.ok_or(CompilerError::IncorrectNumberOfInputs)?;
let n = u8::try_from(private_keys.len()).map_err(|_| {
CompilerError::MiscError("too many keys in bare multisig".to_string())
})?;
if n == 0 {
return Err(CompilerError::MiscError(
"bare multisig requires at least one private key".to_string(),
));
}
let required_clamped = (*required).min(n).max(1);

let mut spk_builder = ScriptBuf::builder().push_int(i64::from(required_clamped));
for sk_bytes in private_keys {
let pk = PrivateKey::from_slice(sk_bytes, NetworkKind::Main).map_err(|_| {
CompilerError::MiscError("invalid bare multisig private key".to_string())
})?;
spk_builder = spk_builder.push_key(&pk.public_key(&self.secp_ctx));
}
let script_pubkey = spk_builder
.push_int(i64::from(n))
.push_opcode(bitcoin::opcodes::all::OP_CHECKMULTISIG)
.into_script();

self.append_variable(Scripts {
script_pubkey: script_pubkey.into(),
script_sig: vec![],
witness: Witness { stack: Vec::new() },
requires_signing: Some(SigningRequest::BareMulti {
required: required_clamped,
private_keys: private_keys.clone(),
sighash_var,
}),
});
}
Operation::BuildPayToScriptHash => {
let script = self.get_input::<Vec<u8>>(&instruction.inputs, 0)?;
let witness_var = self.get_input::<Witness>(&instruction.inputs, 1)?;
Expand Down Expand Up @@ -2198,6 +2247,43 @@ impl Compiler {
_ => {}
}
}
SigningRequest::BareMulti {
required,
private_keys,
sighash_var,
} => {
let sighash_flag = *self.get_variable::<u8>(*sighash_var).unwrap();
let sighash_type =
EcdsaSighashType::from_consensus(u32::from(sighash_flag));

// scriptPubKey is already on the txo; use it for signing
let script_code = Script::from_bytes(&txo_var.scripts.script_pubkey);

// Collect `required` signatures (first `required` keys)
let mut sig_script_builder =
ScriptBuf::builder().push_opcode(bitcoin::opcodes::OP_0);

for sk_bytes in private_keys.iter().take(*required as usize) {
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if let Ok(hash) = cache.legacy_signature_hash(
idx,
script_code,
u32::from(sighash_flag),
) {
let signature = ecdsa::Signature {
signature: self.secp_ctx.sign_ecdsa(
&secp256k1::Message::from_digest(*hash.as_byte_array()),
&SecretKey::from_slice(sk_bytes.as_slice()).unwrap(),
),
sighash_type,
};
sig_script_builder = sig_script_builder.push_slice(
PushBytesBuf::try_from(signature.to_vec()).unwrap(),
);
}
}

tx_var.tx.input[idx].script_sig = sig_script_builder.into_script();
}
SigningRequest::Taproot {
spend_info_var,
selected_leaf,
Expand Down Expand Up @@ -2331,7 +2417,8 @@ impl Compiler {
mod tests {
use super::*;
use crate::{
IndexedVariable, Operation, Program, ProgramBuilder, ProgramContext, TaprootLeafSpec,
IndexedVariable, Instruction, Operation, Program, ProgramBuilder, ProgramContext,
TaprootLeafSpec,
};
use bitcoin::{
Transaction, consensus::Decodable, opcodes::all::OP_PUSHNUM_1, taproot::LeafVersion,
Expand Down Expand Up @@ -2636,6 +2723,56 @@ mod tests {
assert_eq!(&control_block[33..], &HIDDEN_HASH);
}

#[test]
fn compile_bare_multisig_without_sighash_input_returns_error() {
let program = Program::unchecked_new(
test_context(),
vec![Instruction {
inputs: vec![],
operation: Operation::BuildPayToBareMulti {
required: 1,
private_keys: vec![[1u8; 32]],
},
}],
);

let mut compiler = Compiler::new();
let err = compiler
.compile(&program)
.expect_err("expected compile error");
assert!(matches!(err, CompilerError::IncorrectNumberOfInputs));
}

#[test]
fn compile_bare_multisig_without_private_keys_returns_error() {
let program = Program::unchecked_new(
test_context(),
vec![
Instruction {
inputs: vec![],
operation: Operation::LoadSigHashFlags(0),
},
Instruction {
inputs: vec![0],
operation: Operation::BuildPayToBareMulti {
required: 1,
private_keys: vec![],
},
},
],
);

let mut compiler = Compiler::new();
let err = compiler
.compile(&program)
.expect_err("expected compile error");
assert!(matches!(
err,
CompilerError::MiscError(ref msg)
if msg == "bare multisig requires at least one private key"
));
}

fn build_annex_program(annex: Vec<u8>) -> Program {
let mut builder = ProgramBuilder::new(ProgramContext {
num_nodes: 1,
Expand Down
25 changes: 24 additions & 1 deletion fuzzamoto-ir/src/generators/tx.rs
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Expand Up @@ -21,18 +21,20 @@ enum OutputType {
PayToPubKeyHash,
PayToWitnessPubKeyHash,
PayToTaproot,
PayToBareMulti,
OpReturn,
}

fn get_random_output_type<R: RngCore>(rng: &mut R) -> OutputType {
match rng.gen_range(0..8) {
match rng.gen_range(0..9) {
0 => OutputType::PayToWitnessScriptHash,
1 => OutputType::PayToAnchor,
2 => OutputType::PayToScriptHash,
3 => OutputType::PayToPubKey,
4 => OutputType::PayToPubKeyHash,
5 => OutputType::PayToWitnessPubKeyHash,
6 => OutputType::PayToTaproot,
7 => OutputType::PayToBareMulti,
_ => OutputType::OpReturn,
}
}
Expand Down Expand Up @@ -114,6 +116,7 @@ fn build_outputs<R: RngCore>(
)
}
OutputType::PayToTaproot => build_taproot_scripts(builder, rng),
OutputType::PayToBareMulti => build_bare_multi_scripts(builder, rng),
};

let amount_var =
Expand Down Expand Up @@ -546,6 +549,26 @@ fn random_merkle_path<R: RngCore>(rng: &mut R) -> Vec<[u8; 32]> {
(0..depth).map(|_| random_node_hash(rng)).collect()
}

fn build_bare_multi_scripts<R: RngCore>(
builder: &mut ProgramBuilder,
rng: &mut R,
) -> IndexedVariable {
let n = rng.gen_range(1u8..=3u8);
let required = rng.gen_range(1u8..=n);
let private_keys: Vec<[u8; 32]> = (0..n).map(|_| gen_secret_key_bytes(rng)).collect();

let sighash_flags_var =
builder.force_append_expect_output(vec![], &Operation::LoadSigHashFlags(0));

builder.force_append_expect_output(
vec![sighash_flags_var.index],
&Operation::BuildPayToBareMulti {
required,
private_keys,
},
)
}

fn gen_secret_key_bytes<R: RngCore>(rng: &mut R) -> [u8; 32] {
loop {
let mut secret = [0u8; 32];
Expand Down
4 changes: 3 additions & 1 deletion fuzzamoto-ir/src/instruction.rs
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Expand Up @@ -69,7 +69,8 @@ impl Instruction {
| Operation::LoadTaprootAnnex { .. }
| Operation::BuildPayToTaproot
| Operation::TaprootScriptsUseAnnex
| Operation::TaprootTxoUseAnnex => true,
| Operation::TaprootTxoUseAnnex
| Operation::BuildPayToBareMulti { .. } => true,
_ => false,
}
}
Expand Down Expand Up @@ -163,6 +164,7 @@ impl Instruction {
| Operation::TakeCoinbaseTxo
| Operation::TaprootScriptsUseAnnex
| Operation::TaprootTxoUseAnnex
| Operation::BuildPayToBareMulti { .. }
| Operation::TakeTxo => true,

Operation::Nop { .. }
Expand Down
33 changes: 33 additions & 0 deletions fuzzamoto-ir/src/mutators/operation.rs
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Expand Up @@ -318,6 +318,39 @@ impl<R: RngCore, M: OperationByteMutator> Mutator<R> for OperationMutator<M> {
self.byte_array_mutator.mutate_bytes(bytes);
Operation::LoadBytes(bytes.clone()) // TODO this clone is not needed
}
Operation::BuildPayToBareMulti {
required,
private_keys,
} => {
let n = private_keys.len() as u8;
let new_required = if n > 0 {
rng.gen_range(1..=n)
} else {
*required
};
let mut new_keys = private_keys.clone();
if !new_keys.is_empty() {
let idx = rng.gen_range(0..new_keys.len());
let mut key_bytes: Vec<u8> = new_keys[idx].into();
let mut valid_key = false;
for _ in 1..=10 {
self.byte_array_mutator.mutate_bytes(&mut key_bytes);
key_bytes.resize(32, 0);
if PrivateKey::from_slice(&key_bytes, NetworkKind::Main).is_ok() {
valid_key = true;
break;
}
}
if !valid_key {
key_bytes = vec![0x1u8; 32];
}
new_keys[idx] = key_bytes.try_into().unwrap();
}
Operation::BuildPayToBareMulti {
required: new_required,
private_keys: new_keys,
}
}
op => op.clone(),
};

Expand Down
27 changes: 26 additions & 1 deletion fuzzamoto-ir/src/operation.rs
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Expand Up @@ -106,7 +106,7 @@ pub enum Operation {
BuildRawScripts,
BuildPayToWitnessScriptHash,
// TODO: BuildPayToTaproot,
// TODO: BuildPayToBareMulti, BeginMultiSig, EndMultiSig
// TODO: BeginMultiSig, EndMultiSig
BuildPayToPubKey,
BuildPayToPubKeyHash,
BuildPayToWitnessPubKeyHash,
Expand All @@ -119,6 +119,15 @@ pub enum Operation {
BeginPrefillTransactions,
AddPrefillTx,
EndPrefillTransactions,

BuildPayToBareMulti {
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/// m-of-n: number of required signatures (1..=n)
required: u8,
/// Private keys for each pubkey in the script
private_keys: Vec<[u8; 32]>,
},
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// cmpctblock building operations
BuildCompactBlock,

// filterload building operations
Expand Down Expand Up @@ -217,6 +226,17 @@ impl fmt::Display for Operation {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Operation::Nop { .. } => write!(f, "Nop"),
Operation::BuildPayToBareMulti {
required,
private_keys,
} => {
write!(
f,
"BuildPayToBareMulti({}-of-{})",
required,
private_keys.len()
)
}
Operation::LoadBytes(bytes) => write!(
f,
"LoadBytes(\"{}\")",
Expand Down Expand Up @@ -575,6 +595,7 @@ impl Operation {
| Operation::Probe
| Operation::TaprootScriptsUseAnnex
| Operation::TaprootTxoUseAnnex
| Operation::BuildPayToBareMulti { .. }
| Operation::BuildTaprootTree { .. } => false,
}
}
Expand Down Expand Up @@ -741,6 +762,7 @@ impl Operation {
| Operation::BuildCoinbaseTxInput
| Operation::AddCoinbaseTxOutput
| Operation::SendBlockTxn
| Operation::BuildPayToBareMulti { .. }
| Operation::Probe => false,
}
}
Expand Down Expand Up @@ -797,6 +819,7 @@ impl Operation {
Operation::LoadConnectionType(_) => vec![Variable::ConnectionType],
Operation::LoadDuration(_) => vec![Variable::Duration],
Operation::LoadAddr(_) => vec![Variable::AddrRecord],
Operation::BuildPayToBareMulti { .. } => vec![Variable::Scripts],
Operation::LoadBlockHeight(_) => vec![Variable::BlockHeight],
Operation::LoadCompactFilterType(_) => vec![Variable::CompactFilterType],
Operation::SendRawMessage => vec![],
Expand Down Expand Up @@ -981,6 +1004,7 @@ impl Operation {
Variable::Scripts,
Variable::ConstAmount,
],
Operation::BuildPayToBareMulti { .. } => vec![Variable::SigHashFlags],
Operation::TakeTxo => vec![Variable::ConstTx],
Operation::TakeCoinbaseTxo => vec![Variable::ConstCoinbaseTx],
Operation::AddWitness => vec![Variable::MutWitnessStack, Variable::Bytes],
Expand Down Expand Up @@ -1155,6 +1179,7 @@ impl Operation {
| Operation::BuildOpReturnScripts
| Operation::BuildPayToAnchor
| Operation::BuildPayToTaproot
| Operation::BuildPayToBareMulti { .. }
| Operation::BuildPayToPubKey
| Operation::BuildPayToPubKeyHash
| Operation::BuildPayToWitnessPubKeyHash
Expand Down
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