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feat: Validate coinbase outputs (#158)
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Co-authored-by: Maciej Kamiński <[email protected]>
Co-authored-by: Michael Zaikin <[email protected]>
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@manlikeHB @maciejka @m-kus
3 people authored Sep 14, 2024
1 parent 6a18368 commit 89c8055
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Showing 2 changed files with 241 additions and 7 deletions.
9 changes: 8 additions & 1 deletion packages/consensus/src/validation/block.cairo
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,14 @@ pub fn compute_and_validate_tx_data(
let tx_bytes_segwit = @tx.encode_with_witness(tx_bytes_legacy);

let txid = double_sha256_byte_array(tx_bytes_legacy);
let wtxid = double_sha256_byte_array(tx_bytes_segwit);

/// The wTXID for the coinbase transaction must be set to all zeros. This is because it's
/// eventually going to contain the commitment inside it
/// see https://learnmeabitcoin.com/technical/transaction/wtxid/#commitment
let mut wtxid = Default::default();
if i != 0 {
wtxid = double_sha256_byte_array(tx_bytes_segwit);
}

// tx_byte_segwit represents all the bytes in the transaction, so the bytes in the segwit
// fields are tx_byte_segwit - tx_byte_legacy.
Expand Down
239 changes: 233 additions & 6 deletions packages/consensus/src/validation/coinbase.cairo
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Original file line number Diff line number Diff line change
Expand Up @@ -2,15 +2,19 @@
//!
//! https://learnmeabitcoin.com/technical/mining/coinbase-transaction/

use crate::types::transaction::{Transaction, TxIn};
use utils::{bit_shifts::shr, hash::Digest};
use crate::types::transaction::{Transaction, TxIn, TxOut};
use utils::{
bit_shifts::shr, hash::{Digest, DigestIntoByteArray}, sha256::{double_sha256_byte_array}
};

const BIP_34_BLOCK_HEIGHT: u32 = 227_836;
const BIP_141_BLOCK_HEIGHT: u32 = 481_824;
const WTNS_PK_SCRIPT_LEN: u32 = 38;
const WTNS_PK_SCRIPT_PREFIX: felt252 = 116705705699821; // 0x6a24aa21a9ed

/// Validates coinbase transaction.
pub fn validate_coinbase(
tx: @Transaction, total_fees: u64, block_height: u32, _wtxid_commitment: Digest,
tx: @Transaction, total_fees: u64, block_height: u32, wtxid_root: Digest,
) -> Result<(), ByteArray> {
// Ensure there is exactly one coinbase input
if (*tx.inputs).len() != 1 {
Expand All @@ -30,7 +34,13 @@ pub fn validate_coinbase(
let block_reward = compute_block_reward(block_height);
assert(total_output_amount <= total_fees + block_reward, 'total output > block rwd + fees');

// TODO: validate BIP-141 segwit output
// validate BIP-141 segwit output
if block_height >= BIP_141_BLOCK_HEIGHT {
if *tx.is_segwit {
// calculate expected wtxid commitment and validate segwit output
validate_coinbase_outputs(*tx.outputs, calculate_wtxid_commitment(wtxid_root))?;
}
}

Result::Ok(())
}
Expand Down Expand Up @@ -105,14 +115,68 @@ fn compute_block_reward(block_height: u32) -> u64 {
shr(5000000000_u64, (block_height / 210000_u32))
}

/// Calculate wtxid commitment
fn calculate_wtxid_commitment(wtxid_root: Digest) -> Digest {
// construct witness reserved value
// 0000000000000000000000000000000000000000000000000000000000000000
let witness_value_bytes: ByteArray =
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";

// convert wtxid_root to ByteArray
let wtxid_root_bytes: ByteArray = wtxid_root.into();

// concat (witness root hash | witness reserved value)
let res = ByteArrayTrait::concat(@wtxid_root_bytes, @witness_value_bytes);

double_sha256_byte_array(@res)
}

/// validate segwit output (BIP-141)
fn validate_coinbase_outputs(
mut outputs: Span<TxOut>, wtxid_commitment: Digest
) -> Result<(), ByteArray> {
let mut is_wtxid_commitment_present: bool = false;

// construct expected witness script combining prefix and wtxid commitment
let mut expected_witness_script: ByteArray = "";
expected_witness_script.append_word(WTNS_PK_SCRIPT_PREFIX, 6);
expected_witness_script.append(@wtxid_commitment.into());

while let Option::Some(output) = outputs.pop_back() {
let pk_script = *output.pk_script;

// check for pk_script with at least 38 bytes commitment length
if pk_script.len() >= WTNS_PK_SCRIPT_LEN {
// extract witness script containing wtxid commitment
let mut extracted_witness_script: ByteArray = "";
for i in 0..WTNS_PK_SCRIPT_LEN {
extracted_witness_script.append_byte(pk_script[i]);
};

// compare expected and extracted witness script
if expected_witness_script == extracted_witness_script {
is_wtxid_commitment_present = true;
break;
}
}
};

if !is_wtxid_commitment_present {
return Result::Err("No wtxid commitment found");
}

Result::Ok(())
}

#[cfg(test)]
mod tests {
use crate::types::transaction::{TxIn, TxOut, Transaction, OutPoint};
use utils::hex::from_hex;
use super::{
compute_block_reward, validate_coinbase, validate_coinbase_input,
validate_coinbase_sig_script, validate_coinbase_witness
validate_coinbase_sig_script, validate_coinbase_witness, validate_coinbase_outputs,
calculate_wtxid_commitment
};
use utils::{hex::{from_hex, hex_to_hash_rev}, hash::Digest};

// Ref implementation here:
// https://github.com/bitcoin/bitcoin/blob/0f68a05c084bef3e53e3f549c403bc90b1db319c/src/test/validation_tests.cpp#L24
Expand Down Expand Up @@ -424,4 +488,167 @@ mod tests {
.span();
validate_coinbase_witness(witness).unwrap();
}

#[test]
fn test_validate_coinbase_outputs_with_no_wtxid_commitment() {
let outputs = array![
TxOut {
value: 625107042,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000000000000000"
),
cached: false
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000000000000000"
),
cached: false
}
]
.span();

let wtxid_commitment = Digest {
value: [
0x10109f4b,
0x82aa3ed7,
0xec9d02a2,
0xa9024647,
0x8b3308c8,
0xb85daf62,
0xfe501d58,
0xd05727a4
]
};

validate_coinbase_outputs(outputs, wtxid_commitment).unwrap_err();
}

#[test]
fn test_validate_coinbase_outputs() {
let outputs = array![
TxOut {
value: 625107042,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000000000000000"
),
cached: false
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"6a24aa21a9ed6502e8637ba29cd8a820021915339c7341223d571e5e8d66edd83786d387e715"
),
cached: false
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000000000000000"
),
cached: false
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000000000000000"
),
cached: false
}
]
.span();

let wtxid_commitment: Digest = hex_to_hash_rev(
"15e787d38637d8ed668d5e1e573d2241739c3315190220a8d89ca27b63e80265"
);

validate_coinbase_outputs(outputs, wtxid_commitment).unwrap();
}

#[test]
fn test_calculate_wtxid_commitment() {
let witness_root_hash: Digest = hex_to_hash_rev(
"f2db1fa411685843d0b5ece37cacb7df882a64f13a68df1d2aaa8c8a869aeedb"
);

let expected_wtxid_commitment = from_hex(
"6502e8637ba29cd8a820021915339c7341223d571e5e8d66edd83786d387e715"
);

assert_eq!(
(calculate_wtxid_commitment(witness_root_hash)).into(), expected_wtxid_commitment
);
}

#[test]
fn test_validate_coinbase_with_segwit_tx() {
let tx = Transaction {
version: 1,
is_segwit: true,
inputs: array![
TxIn {
script: @from_hex(
"0320a107046f0a385a632f4254432e434f4d2ffabe6d6dbdd0ee86f9a1badfd0aa1b3c9dac8d90840cf973f7b2590d6c9adde1a6e0974a010000000000000001283da9a172020000000000"
),
sequence: 4294967295,
previous_output: OutPoint {
txid: 0x0_u256.into(),
vout: 0xffffffff_u32,
data: Default::default(),
block_height: Default::default(),
block_time: Default::default(),
is_coinbase: false,
},
witness: array![
from_hex("0000000000000000000000000000000000000000000000000000000000000000")
]
.span(),
}
]
.span(),
outputs: array![
TxOut {
value: 0_u64,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000"
),
cached: false,
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"6a24aa21a9ed6502e8637ba29cd8a820021915339c7341223d571e5e8d66edd83786d387e715"
),
cached: false,
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000"
),
cached: false,
},
TxOut {
value: 0_u64,
pk_script: @from_hex(
"0000000000000000000000000000000000000000000000000000000000000000"
),
cached: false,
}
]
.span(),
lock_time: 0
};

let total_fees = 0_u64;
let block_height = 500_000;

let wtxid_root_hash: Digest = hex_to_hash_rev(
"f2db1fa411685843d0b5ece37cacb7df882a64f13a68df1d2aaa8c8a869aeedb"
);

validate_coinbase(@tx, total_fees, block_height, wtxid_root_hash).unwrap();
}
}

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