blocktools.py

#!/usr/bin/env python3
# Copyright (c) 2015-2017 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Utilities for manipulating blocks and transactions."""

from .address import (
    key_to_p2sh_p2wpkh,
    key_to_p2wpkh,
    script_to_p2sh_p2wsh,
    script_to_p2wsh,
)
from .messages import (
    CBlock,
    COIN,
    COutPoint,
    CTransaction,
    CTxIn,
    CTxInWitness,
    CTxOut,
    FromHex,
    ToHex,
    bytes_to_hex_str,
    hash256,
    hex_str_to_bytes,
    ser_string,
    ser_uint256,
    sha256,
    uint256_from_str,
)
from .script import (
    CScript,
    OP_0,
    OP_1,
    OP_CHECKMULTISIG,
    OP_CHECKSIG,
    OP_RETURN,
    OP_TRUE,
    hash160,
)
from .util import assert_equal

# From BIP141
WITNESS_COMMITMENT_HEADER = b"\xaa\x21\xa9\xed"

def create_block(hashprev, coinbase, ntime=None):
    """Create a block (with regtest difficulty)."""
    block = CBlock()
    if ntime is None:
        import time
        block.nTime = int(time.time() + 600)
    else:
        block.nTime = ntime
    block.hashPrevBlock = hashprev
    block.nBits = 0x207fffff  # difficulty retargeting is disabled in REGTEST chainparams
    block.vtx.append(coinbase)
    block.hashMerkleRoot = block.calc_merkle_root()
    block.calc_sha256()
    return block

def get_witness_script(witness_root, witness_nonce):
    witness_commitment = uint256_from_str(hash256(ser_uint256(witness_root) + ser_uint256(witness_nonce)))
    output_data = WITNESS_COMMITMENT_HEADER + ser_uint256(witness_commitment)
    return CScript([OP_RETURN, output_data])

def add_witness_commitment(block, nonce=0):
    """Add a witness commitment to the block's coinbase transaction.

    According to BIP141, blocks with witness rules active must commit to the
    hash of all in-block transactions including witness."""
    # First calculate the merkle root of the block's
    # transactions, with witnesses.
    witness_nonce = nonce
    witness_root = block.calc_witness_merkle_root()
    # witness_nonce should go to coinbase witness.
    block.vtx[0].wit.vtxinwit = [CTxInWitness()]
    block.vtx[0].wit.vtxinwit[0].scriptWitness.stack = [ser_uint256(witness_nonce)]

    # witness commitment is the last OP_RETURN output in coinbase
    block.vtx[0].vout.append(CTxOut(0, get_witness_script(witness_root, witness_nonce)))
    block.vtx[0].rehash()
    block.hashMerkleRoot = block.calc_merkle_root()
    block.rehash()

def serialize_script_num(value):
    r = bytearray(0)
    if value == 0:
        return r
    neg = value < 0
    absvalue = -value if neg else value
    while (absvalue):
        r.append(int(absvalue & 0xff))
        absvalue >>= 8
    if r[-1] & 0x80:
        r.append(0x80 if neg else 0)
    elif neg:
        r[-1] |= 0x80
    return r

def create_coinbase(height, pubkey=None):
    """Create a coinbase transaction, assuming no miner fees.

    If pubkey is passed in, the coinbase output will be a P2PK output;
    otherwise an anyone-can-spend output."""
    coinbase = CTransaction()
    coinbase.vin.append(CTxIn(COutPoint(0, 0xffffffff),
                        ser_string(serialize_script_num(height)), 0xffffffff))
    coinbaseoutput = CTxOut()
    coinbaseoutput.nValue = 50 * COIN
    halvings = int(height / 150)  # regtest
    coinbaseoutput.nValue >>= halvings
    if (pubkey is not None):
        coinbaseoutput.scriptPubKey = CScript([pubkey, OP_CHECKSIG])
    else:
        coinbaseoutput.scriptPubKey = CScript([OP_TRUE])
    coinbase.vout = [coinbaseoutput]
    coinbase.calc_sha256()
    return coinbase

def create_transaction(prevtx, n, sig, value, script_pub_key=CScript()):
    """Create a transaction.

    If the script_pub_key is not specified, make it anyone-can-spend."""
    tx = CTransaction()
    assert(n < len(prevtx.vout))
    tx.vin.append(CTxIn(COutPoint(prevtx.sha256, n), sig, 0xffffffff))
    tx.vout.append(CTxOut(value, script_pub_key))
    tx.calc_sha256()
    return tx

def get_legacy_sigopcount_block(block, accurate=True):
    count = 0
    for tx in block.vtx:
        count += get_legacy_sigopcount_tx(tx, accurate)
    return count

def get_legacy_sigopcount_tx(tx, accurate=True):
    count = 0
    for i in tx.vout:
        count += i.scriptPubKey.GetSigOpCount(accurate)
    for j in tx.vin:
        # scriptSig might be of type bytes, so convert to CScript for the moment
        count += CScript(j.scriptSig).GetSigOpCount(accurate)
    return count

def witness_script(use_p2wsh, pubkey):
    """Create a scriptPubKey for a pay-to-wtiness TxOut.

    This is either a P2WPKH output for the given pubkey, or a P2WSH output of a
    1-of-1 multisig for the given pubkey. Returns the hex encoding of the
    scriptPubKey."""
    if not use_p2wsh:
        # P2WPKH instead
        pubkeyhash = hash160(hex_str_to_bytes(pubkey))
        pkscript = CScript([OP_0, pubkeyhash])
    else:
        # 1-of-1 multisig
        witness_program = CScript([OP_1, hex_str_to_bytes(pubkey), OP_1, OP_CHECKMULTISIG])
        scripthash = sha256(witness_program)
        pkscript = CScript([OP_0, scripthash])
    return bytes_to_hex_str(pkscript)

def create_witness_tx(node, use_p2wsh, utxo, pubkey, encode_p2sh, amount):
    """Return a transaction (in hex) that spends the given utxo to a segwit output.

    Optionally wrap the segwit output using P2SH."""
    if use_p2wsh:
        program = CScript([OP_1, hex_str_to_bytes(pubkey), OP_1, OP_CHECKMULTISIG])
        addr = script_to_p2sh_p2wsh(program) if encode_p2sh else script_to_p2wsh(program)
    else:
        addr = key_to_p2sh_p2wpkh(pubkey) if encode_p2sh else key_to_p2wpkh(pubkey)
    if not encode_p2sh:
        assert_equal(node.getaddressinfo(addr)['scriptPubKey'], witness_script(use_p2wsh, pubkey))
    return node.createrawtransaction([utxo], {addr: amount})

def send_to_witness(use_p2wsh, node, utxo, pubkey, encode_p2sh, amount, sign=True, insert_redeem_script=""):
    """Create a transaction spending a given utxo to a segwit output.

    The output corresponds to the given pubkey: use_p2wsh determines whether to
    use P2WPKH or P2WSH; encode_p2sh determines whether to wrap in P2SH.
    sign=True will have the given node sign the transaction.
    insert_redeem_script will be added to the scriptSig, if given."""
    tx_to_witness = create_witness_tx(node, use_p2wsh, utxo, pubkey, encode_p2sh, amount)
    if (sign):
        signed = node.signrawtransactionwithwallet(tx_to_witness)
        assert("errors" not in signed or len(["errors"]) == 0)
        return node.sendrawtransaction(signed["hex"])
    else:
        if (insert_redeem_script):
            tx = FromHex(CTransaction(), tx_to_witness)
            tx.vin[0].scriptSig += CScript([hex_str_to_bytes(insert_redeem_script)])
            tx_to_witness = ToHex(tx)

    return node.sendrawtransaction(tx_to_witness)