script.py

#!/usr/bin/env python3
# Copyright (c) 2015-2022 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Functionality to build scripts, as well as signature hash functions.

This file is modified from python-BGLlib.
"""

from collections import namedtuple
import struct
import unittest

from .key import TaggedHash, tweak_add_pubkey, compute_xonly_pubkey

from .messages import (
    CTransaction,
    CTxOut,
    hash256,
    keccak256,
    ser_string,
    ser_uint256,
    sha256,
    uint256_from_str,
)

from .crypto.ripemd160 import ripemd160

MAX_SCRIPT_ELEMENT_SIZE = 520
MAX_PUBKEYS_PER_MULTI_A = 512
LOCKTIME_THRESHOLD = 500000000
ANNEX_TAG = 0x50

LEAF_VERSION_TAPSCRIPT = 0xc0

def hash160(s):
    return ripemd160(sha256(s))

def bn2vch(v):
    """Convert number to BGL-specific little endian format."""
    # We need v.bit_length() bits, plus a sign bit for every nonzero number.
    n_bits = v.bit_length() + (v != 0)
    # The number of bytes for that is:
    n_bytes = (n_bits + 7) // 8
    # Convert number to absolute value + sign in top bit.
    encoded_v = 0 if v == 0 else abs(v) | ((v < 0) << (n_bytes * 8 - 1))
    # Serialize to bytes
    return encoded_v.to_bytes(n_bytes, 'little')

class CScriptOp(int):
    """A single script opcode"""
    __slots__ = ()

    @staticmethod
    def encode_op_pushdata(d):
        """Encode a PUSHDATA op, returning bytes"""
        if len(d) < 0x4c:
            return b'' + bytes([len(d)]) + d # OP_PUSHDATA
        elif len(d) <= 0xff:
            return b'\x4c' + bytes([len(d)]) + d # OP_PUSHDATA1
        elif len(d) <= 0xffff:
            return b'\x4d' + struct.pack(b'<H', len(d)) + d # OP_PUSHDATA2
        elif len(d) <= 0xffffffff:
            return b'\x4e' + struct.pack(b'<I', len(d)) + d # OP_PUSHDATA4
        else:
            raise ValueError("Data too long to encode in a PUSHDATA op")

    @staticmethod
    def encode_op_n(n):
        """Encode a small integer op, returning an opcode"""
        if not (0 <= n <= 16):
            raise ValueError('Integer must be in range 0 <= n <= 16, got %d' % n)

        if n == 0:
            return OP_0
        else:
            return CScriptOp(OP_1 + n-1)

    def decode_op_n(self):
        """Decode a small integer opcode, returning an integer"""
        if self == OP_0:
            return 0

        if not (self == OP_0 or OP_1 <= self <= OP_16):
            raise ValueError('op %r is not an OP_N' % self)

        return int(self - OP_1+1)

    def is_small_int(self):
        """Return true if the op pushes a small integer to the stack"""
        if 0x51 <= self <= 0x60 or self == 0:
            return True
        else:
            return False

    def __str__(self):
        return repr(self)

    def __repr__(self):
        if self in OPCODE_NAMES:
            return OPCODE_NAMES[self]
        else:
            return 'CScriptOp(0x%x)' % self

    def __new__(cls, n):
        try:
            return _opcode_instances[n]
        except IndexError:
            assert len(_opcode_instances) == n
            _opcode_instances.append(super().__new__(cls, n))
            return _opcode_instances[n]

OPCODE_NAMES: dict[CScriptOp, str] = {}
_opcode_instances: list[CScriptOp] = []

# Populate opcode instance table
for n in range(0xff+1):
    CScriptOp(n)


# push value
OP_0 = CScriptOp(0x00)
OP_FALSE = OP_0
OP_PUSHDATA1 = CScriptOp(0x4c)
OP_PUSHDATA2 = CScriptOp(0x4d)
OP_PUSHDATA4 = CScriptOp(0x4e)
OP_1NEGATE = CScriptOp(0x4f)
OP_RESERVED = CScriptOp(0x50)
OP_1 = CScriptOp(0x51)
OP_TRUE=OP_1
OP_2 = CScriptOp(0x52)
OP_3 = CScriptOp(0x53)
OP_4 = CScriptOp(0x54)
OP_5 = CScriptOp(0x55)
OP_6 = CScriptOp(0x56)
OP_7 = CScriptOp(0x57)
OP_8 = CScriptOp(0x58)
OP_9 = CScriptOp(0x59)
OP_10 = CScriptOp(0x5a)
OP_11 = CScriptOp(0x5b)
OP_12 = CScriptOp(0x5c)
OP_13 = CScriptOp(0x5d)
OP_14 = CScriptOp(0x5e)
OP_15 = CScriptOp(0x5f)
OP_16 = CScriptOp(0x60)

# control
OP_NOP = CScriptOp(0x61)
OP_VER = CScriptOp(0x62)
OP_IF = CScriptOp(0x63)
OP_NOTIF = CScriptOp(0x64)
OP_VERIF = CScriptOp(0x65)
OP_VERNOTIF = CScriptOp(0x66)
OP_ELSE = CScriptOp(0x67)
OP_ENDIF = CScriptOp(0x68)
OP_VERIFY = CScriptOp(0x69)
OP_RETURN = CScriptOp(0x6a)

# stack ops
OP_TOALTSTACK = CScriptOp(0x6b)
OP_FROMALTSTACK = CScriptOp(0x6c)
OP_2DROP = CScriptOp(0x6d)
OP_2DUP = CScriptOp(0x6e)
OP_3DUP = CScriptOp(0x6f)
OP_2OVER = CScriptOp(0x70)
OP_2ROT = CScriptOp(0x71)
OP_2SWAP = CScriptOp(0x72)
OP_IFDUP = CScriptOp(0x73)
OP_DEPTH = CScriptOp(0x74)
OP_DROP = CScriptOp(0x75)
OP_DUP = CScriptOp(0x76)
OP_NIP = CScriptOp(0x77)
OP_OVER = CScriptOp(0x78)
OP_PICK = CScriptOp(0x79)
OP_ROLL = CScriptOp(0x7a)
OP_ROT = CScriptOp(0x7b)
OP_SWAP = CScriptOp(0x7c)
OP_TUCK = CScriptOp(0x7d)

# splice ops
OP_CAT = CScriptOp(0x7e)
OP_SUBSTR = CScriptOp(0x7f)
OP_LEFT = CScriptOp(0x80)
OP_RIGHT = CScriptOp(0x81)
OP_SIZE = CScriptOp(0x82)

# bit logic
OP_INVERT = CScriptOp(0x83)
OP_AND = CScriptOp(0x84)
OP_OR = CScriptOp(0x85)
OP_XOR = CScriptOp(0x86)
OP_EQUAL = CScriptOp(0x87)
OP_EQUALVERIFY = CScriptOp(0x88)
OP_RESERVED1 = CScriptOp(0x89)
OP_RESERVED2 = CScriptOp(0x8a)

# numeric
OP_1ADD = CScriptOp(0x8b)
OP_1SUB = CScriptOp(0x8c)
OP_2MUL = CScriptOp(0x8d)
OP_2DIV = CScriptOp(0x8e)
OP_NEGATE = CScriptOp(0x8f)
OP_ABS = CScriptOp(0x90)
OP_NOT = CScriptOp(0x91)
OP_0NOTEQUAL = CScriptOp(0x92)

OP_ADD = CScriptOp(0x93)
OP_SUB = CScriptOp(0x94)
OP_MUL = CScriptOp(0x95)
OP_DIV = CScriptOp(0x96)
OP_MOD = CScriptOp(0x97)
OP_LSHIFT = CScriptOp(0x98)
OP_RSHIFT = CScriptOp(0x99)

OP_BOOLAND = CScriptOp(0x9a)
OP_BOOLOR = CScriptOp(0x9b)
OP_NUMEQUAL = CScriptOp(0x9c)
OP_NUMEQUALVERIFY = CScriptOp(0x9d)
OP_NUMNOTEQUAL = CScriptOp(0x9e)
OP_LESSTHAN = CScriptOp(0x9f)
OP_GREATERTHAN = CScriptOp(0xa0)
OP_LESSTHANOREQUAL = CScriptOp(0xa1)
OP_GREATERTHANOREQUAL = CScriptOp(0xa2)
OP_MIN = CScriptOp(0xa3)
OP_MAX = CScriptOp(0xa4)

OP_WITHIN = CScriptOp(0xa5)

# crypto
OP_RIPEMD160 = CScriptOp(0xa6)
OP_SHA1 = CScriptOp(0xa7)
OP_SHA256 = CScriptOp(0xa8)
OP_HASH160 = CScriptOp(0xa9)
OP_HASH256 = CScriptOp(0xaa)
OP_CODESEPARATOR = CScriptOp(0xab)
OP_CHECKSIG = CScriptOp(0xac)
OP_CHECKSIGVERIFY = CScriptOp(0xad)
OP_CHECKMULTISIG = CScriptOp(0xae)
OP_CHECKMULTISIGVERIFY = CScriptOp(0xaf)

# expansion
OP_NOP1 = CScriptOp(0xb0)
OP_CHECKLOCKTIMEVERIFY = CScriptOp(0xb1)
OP_CHECKSEQUENCEVERIFY = CScriptOp(0xb2)
OP_NOP4 = CScriptOp(0xb3)
OP_NOP5 = CScriptOp(0xb4)
OP_NOP6 = CScriptOp(0xb5)
OP_NOP7 = CScriptOp(0xb6)
OP_NOP8 = CScriptOp(0xb7)
OP_NOP9 = CScriptOp(0xb8)
OP_NOP10 = CScriptOp(0xb9)

# BIP 342 opcodes (Tapscript)
OP_CHECKSIGADD = CScriptOp(0xba)

OP_INVALIDOPCODE = CScriptOp(0xff)

OPCODE_NAMES.update({
    OP_0: 'OP_0',
    OP_PUSHDATA1: 'OP_PUSHDATA1',
    OP_PUSHDATA2: 'OP_PUSHDATA2',
    OP_PUSHDATA4: 'OP_PUSHDATA4',
    OP_1NEGATE: 'OP_1NEGATE',
    OP_RESERVED: 'OP_RESERVED',
    OP_1: 'OP_1',
    OP_2: 'OP_2',
    OP_3: 'OP_3',
    OP_4: 'OP_4',
    OP_5: 'OP_5',
    OP_6: 'OP_6',
    OP_7: 'OP_7',
    OP_8: 'OP_8',
    OP_9: 'OP_9',
    OP_10: 'OP_10',
    OP_11: 'OP_11',
    OP_12: 'OP_12',
    OP_13: 'OP_13',
    OP_14: 'OP_14',
    OP_15: 'OP_15',
    OP_16: 'OP_16',
    OP_NOP: 'OP_NOP',
    OP_VER: 'OP_VER',
    OP_IF: 'OP_IF',
    OP_NOTIF: 'OP_NOTIF',
    OP_VERIF: 'OP_VERIF',
    OP_VERNOTIF: 'OP_VERNOTIF',
    OP_ELSE: 'OP_ELSE',
    OP_ENDIF: 'OP_ENDIF',
    OP_VERIFY: 'OP_VERIFY',
    OP_RETURN: 'OP_RETURN',
    OP_TOALTSTACK: 'OP_TOALTSTACK',
    OP_FROMALTSTACK: 'OP_FROMALTSTACK',
    OP_2DROP: 'OP_2DROP',
    OP_2DUP: 'OP_2DUP',
    OP_3DUP: 'OP_3DUP',
    OP_2OVER: 'OP_2OVER',
    OP_2ROT: 'OP_2ROT',
    OP_2SWAP: 'OP_2SWAP',
    OP_IFDUP: 'OP_IFDUP',
    OP_DEPTH: 'OP_DEPTH',
    OP_DROP: 'OP_DROP',
    OP_DUP: 'OP_DUP',
    OP_NIP: 'OP_NIP',
    OP_OVER: 'OP_OVER',
    OP_PICK: 'OP_PICK',
    OP_ROLL: 'OP_ROLL',
    OP_ROT: 'OP_ROT',
    OP_SWAP: 'OP_SWAP',
    OP_TUCK: 'OP_TUCK',
    OP_CAT: 'OP_CAT',
    OP_SUBSTR: 'OP_SUBSTR',
    OP_LEFT: 'OP_LEFT',
    OP_RIGHT: 'OP_RIGHT',
    OP_SIZE: 'OP_SIZE',
    OP_INVERT: 'OP_INVERT',
    OP_AND: 'OP_AND',
    OP_OR: 'OP_OR',
    OP_XOR: 'OP_XOR',
    OP_EQUAL: 'OP_EQUAL',
    OP_EQUALVERIFY: 'OP_EQUALVERIFY',
    OP_RESERVED1: 'OP_RESERVED1',
    OP_RESERVED2: 'OP_RESERVED2',
    OP_1ADD: 'OP_1ADD',
    OP_1SUB: 'OP_1SUB',
    OP_2MUL: 'OP_2MUL',
    OP_2DIV: 'OP_2DIV',
    OP_NEGATE: 'OP_NEGATE',
    OP_ABS: 'OP_ABS',
    OP_NOT: 'OP_NOT',
    OP_0NOTEQUAL: 'OP_0NOTEQUAL',
    OP_ADD: 'OP_ADD',
    OP_SUB: 'OP_SUB',
    OP_MUL: 'OP_MUL',
    OP_DIV: 'OP_DIV',
    OP_MOD: 'OP_MOD',
    OP_LSHIFT: 'OP_LSHIFT',
    OP_RSHIFT: 'OP_RSHIFT',
    OP_BOOLAND: 'OP_BOOLAND',
    OP_BOOLOR: 'OP_BOOLOR',
    OP_NUMEQUAL: 'OP_NUMEQUAL',
    OP_NUMEQUALVERIFY: 'OP_NUMEQUALVERIFY',
    OP_NUMNOTEQUAL: 'OP_NUMNOTEQUAL',
    OP_LESSTHAN: 'OP_LESSTHAN',
    OP_GREATERTHAN: 'OP_GREATERTHAN',
    OP_LESSTHANOREQUAL: 'OP_LESSTHANOREQUAL',
    OP_GREATERTHANOREQUAL: 'OP_GREATERTHANOREQUAL',
    OP_MIN: 'OP_MIN',
    OP_MAX: 'OP_MAX',
    OP_WITHIN: 'OP_WITHIN',
    OP_RIPEMD160: 'OP_RIPEMD160',
    OP_SHA1: 'OP_SHA1',
    OP_SHA256: 'OP_SHA256',
    OP_HASH160: 'OP_HASH160',
    OP_HASH256: 'OP_HASH256',
    OP_CODESEPARATOR: 'OP_CODESEPARATOR',
    OP_CHECKSIG: 'OP_CHECKSIG',
    OP_CHECKSIGVERIFY: 'OP_CHECKSIGVERIFY',
    OP_CHECKMULTISIG: 'OP_CHECKMULTISIG',
    OP_CHECKMULTISIGVERIFY: 'OP_CHECKMULTISIGVERIFY',
    OP_NOP1: 'OP_NOP1',
    OP_CHECKLOCKTIMEVERIFY: 'OP_CHECKLOCKTIMEVERIFY',
    OP_CHECKSEQUENCEVERIFY: 'OP_CHECKSEQUENCEVERIFY',
    OP_NOP4: 'OP_NOP4',
    OP_NOP5: 'OP_NOP5',
    OP_NOP6: 'OP_NOP6',
    OP_NOP7: 'OP_NOP7',
    OP_NOP8: 'OP_NOP8',
    OP_NOP9: 'OP_NOP9',
    OP_NOP10: 'OP_NOP10',
    OP_CHECKSIGADD: 'OP_CHECKSIGADD',
    OP_INVALIDOPCODE: 'OP_INVALIDOPCODE',
})

class CScriptInvalidError(Exception):
    """Base class for CScript exceptions"""
    pass

class CScriptTruncatedPushDataError(CScriptInvalidError):
    """Invalid pushdata due to truncation"""
    def __init__(self, msg, data):
        self.data = data
        super().__init__(msg)


# This is used, eg, for blockchain heights in coinbase scripts (bip34)
class CScriptNum:
    __slots__ = ("value",)

    def __init__(self, d=0):
        self.value = d

    @staticmethod
    def encode(obj):
        r = bytearray(0)
        if obj.value == 0:
            return bytes(r)
        neg = obj.value < 0
        absvalue = -obj.value if neg else obj.value
        while (absvalue):
            r.append(absvalue & 0xff)
            absvalue >>= 8
        if r[-1] & 0x80:
            r.append(0x80 if neg else 0)
        elif neg:
            r[-1] |= 0x80
        return bytes([len(r)]) + r

    @staticmethod
    def decode(vch):
        result = 0
        # We assume valid push_size and minimal encoding
        value = vch[1:]
        if len(value) == 0:
            return result
        for i, byte in enumerate(value):
            result |= int(byte) << 8*i
        if value[-1] >= 0x80:
            # Mask for all but the highest result bit
            num_mask = (2**(len(value)*8) - 1) >> 1
            result &= num_mask
            result *= -1
        return result


class CScript(bytes):
    """Serialized script

    A bytes subclass, so you can use this directly whenever bytes are accepted.
    Note that this means that indexing does *not* work - you'll get an index by
    byte rather than opcode. This format was chosen for efficiency so that the
    general case would not require creating a lot of little CScriptOP objects.

    iter(script) however does iterate by opcode.
    """
    __slots__ = ()

    @classmethod
    def __coerce_instance(cls, other):
        # Coerce other into bytes
        if isinstance(other, CScriptOp):
            other = bytes([other])
        elif isinstance(other, CScriptNum):
            if (other.value == 0):
                other = bytes([CScriptOp(OP_0)])
            else:
                other = CScriptNum.encode(other)
        elif isinstance(other, int):
            if 0 <= other <= 16:
                other = bytes([CScriptOp.encode_op_n(other)])
            elif other == -1:
                other = bytes([OP_1NEGATE])
            else:
                other = CScriptOp.encode_op_pushdata(bn2vch(other))
        elif isinstance(other, (bytes, bytearray)):
            other = CScriptOp.encode_op_pushdata(other)
        return other

    def __add__(self, other):
        # add makes no sense for a CScript()
        raise NotImplementedError

    def join(self, iterable):
        # join makes no sense for a CScript()
        raise NotImplementedError

    def __new__(cls, value=b''):
        if isinstance(value, bytes) or isinstance(value, bytearray):
            return super().__new__(cls, value)
        else:
            def coerce_iterable(iterable):
                for instance in iterable:
                    yield cls.__coerce_instance(instance)
            # Annoyingly on both python2 and python3 bytes.join() always
            # returns a bytes instance even when subclassed.
            return super().__new__(cls, b''.join(coerce_iterable(value)))

    def raw_iter(self):
        """Raw iteration

        Yields tuples of (opcode, data, sop_idx) so that the different possible
        PUSHDATA encodings can be accurately distinguished, as well as
        determining the exact opcode byte indexes. (sop_idx)
        """
        i = 0
        while i < len(self):
            sop_idx = i
            opcode = self[i]
            i += 1

            if opcode > OP_PUSHDATA4:
                yield (opcode, None, sop_idx)
            else:
                datasize = None
                pushdata_type = None
                if opcode < OP_PUSHDATA1:
                    pushdata_type = 'PUSHDATA(%d)' % opcode
                    datasize = opcode

                elif opcode == OP_PUSHDATA1:
                    pushdata_type = 'PUSHDATA1'
                    if i >= len(self):
                        raise CScriptInvalidError('PUSHDATA1: missing data length')
                    datasize = self[i]
                    i += 1

                elif opcode == OP_PUSHDATA2:
                    pushdata_type = 'PUSHDATA2'
                    if i + 1 >= len(self):
                        raise CScriptInvalidError('PUSHDATA2: missing data length')
                    datasize = self[i] + (self[i+1] << 8)
                    i += 2

                elif opcode == OP_PUSHDATA4:
                    pushdata_type = 'PUSHDATA4'
                    if i + 3 >= len(self):
                        raise CScriptInvalidError('PUSHDATA4: missing data length')
                    datasize = self[i] + (self[i+1] << 8) + (self[i+2] << 16) + (self[i+3] << 24)
                    i += 4

                else:
                    assert False # shouldn't happen


                data = bytes(self[i:i+datasize])

                # Check for truncation
                if len(data) < datasize:
                    raise CScriptTruncatedPushDataError('%s: truncated data' % pushdata_type, data)

                i += datasize

                yield (opcode, data, sop_idx)

    def __iter__(self):
        """'Cooked' iteration

        Returns either a CScriptOP instance, an integer, or bytes, as
        appropriate.

        See raw_iter() if you need to distinguish the different possible
        PUSHDATA encodings.
        """
        for (opcode, data, sop_idx) in self.raw_iter():
            if data is not None:
                yield data
            else:
                opcode = CScriptOp(opcode)

                if opcode.is_small_int():
                    yield opcode.decode_op_n()
                else:
                    yield CScriptOp(opcode)

    def __repr__(self):
        def _repr(o):
            if isinstance(o, bytes):
                return "x('%s')" % o.hex()
            else:
                return repr(o)

        ops = []
        i = iter(self)
        while True:
            op = None
            try:
                op = _repr(next(i))
            except CScriptTruncatedPushDataError as err:
                op = '%s...<ERROR: %s>' % (_repr(err.data), err)
                break
            except CScriptInvalidError as err:
                op = '<ERROR: %s>' % err
                break
            except StopIteration:
                break
            finally:
                if op is not None:
                    ops.append(op)

        return "CScript([%s])" % ', '.join(ops)

    def GetSigOpCount(self, fAccurate):
        """Get the SigOp count.

        fAccurate - Accurately count CHECKMULTISIG, see BIP16 for details.

        Note that this is consensus-critical.
        """
        n = 0
        lastOpcode = OP_INVALIDOPCODE
        for (opcode, data, sop_idx) in self.raw_iter():
            if opcode in (OP_CHECKSIG, OP_CHECKSIGVERIFY):
                n += 1
            elif opcode in (OP_CHECKMULTISIG, OP_CHECKMULTISIGVERIFY):
                if fAccurate and (OP_1 <= lastOpcode <= OP_16):
                    n += opcode.decode_op_n()
                else:
                    n += 20
            lastOpcode = opcode
        return n

    def IsWitnessProgram(self):
        """A witness program is any valid CScript that consists of a 1-byte
            push opcode followed by a data push between 2 and 40 bytes."""
        return ((4 <= len(self) <= 42) and
                (self[0] == OP_0 or (OP_1 <= self[0] <= OP_16)) and
                (self[1] + 2 == len(self)))


SIGHASH_DEFAULT = 0 # Taproot-only default, semantics same as SIGHASH_ALL
SIGHASH_ALL = 1
SIGHASH_NONE = 2
SIGHASH_SINGLE = 3
SIGHASH_ANYONECANPAY = 0x80

def FindAndDelete(script, sig):
    """Consensus critical, see FindAndDelete() in Satoshi codebase"""
    r = b''
    last_sop_idx = sop_idx = 0
    skip = True
    for (opcode, data, sop_idx) in script.raw_iter():
        if not skip:
            r += script[last_sop_idx:sop_idx]
        last_sop_idx = sop_idx
        if script[sop_idx:sop_idx + len(sig)] == sig:
            skip = True
        else:
            skip = False
    if not skip:
        r += script[last_sop_idx:]
    return CScript(r)

def LegacySignatureMsg(script, txTo, inIdx, hashtype):
    """Preimage of the signature hash, if it exists.

    Returns either (None, err) to indicate error (which translates to sighash 1),
    or (msg, None).
    """

    if inIdx >= len(txTo.vin):
        return (None, "inIdx %d out of range (%d)" % (inIdx, len(txTo.vin)))
    txtmp = CTransaction(txTo)

    for txin in txtmp.vin:
        txin.scriptSig = b''
    txtmp.vin[inIdx].scriptSig = FindAndDelete(script, CScript([OP_CODESEPARATOR]))

    if (hashtype & 0x1f) == SIGHASH_NONE:
        txtmp.vout = []

        for i in range(len(txtmp.vin)):
            if i != inIdx:
                txtmp.vin[i].nSequence = 0

    elif (hashtype & 0x1f) == SIGHASH_SINGLE:
        outIdx = inIdx
        if outIdx >= len(txtmp.vout):
            return (None, "outIdx %d out of range (%d)" % (outIdx, len(txtmp.vout)))

        tmp = txtmp.vout[outIdx]
        txtmp.vout = []
        for _ in range(outIdx):
            txtmp.vout.append(CTxOut(-1))
        txtmp.vout.append(tmp)

        for i in range(len(txtmp.vin)):
            if i != inIdx:
                txtmp.vin[i].nSequence = 0

    if hashtype & SIGHASH_ANYONECANPAY:
        tmp = txtmp.vin[inIdx]
        txtmp.vin = []
        txtmp.vin.append(tmp)

    s = txtmp.serialize_without_witness()
    s += struct.pack(b"<I", hashtype)

    return (s, None)

def LegacySignatureHash(*args, **kwargs):
    """Consensus-correct SignatureHash

    Returns (hash, err) to precisely match the consensus-critical behavior of
    the SIGHASH_SINGLE bug. (inIdx is *not* checked for validity)
    """

    HASH_ONE = b'\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
    msg, err = LegacySignatureMsg(*args, **kwargs)
    if msg is None:
        return (HASH_ONE, err)
    else:
        return (keccak256(msg), err)

def sign_input_legacy(tx, input_index, input_scriptpubkey, privkey, sighash_type=SIGHASH_ALL):
    """Add legacy ECDSA signature for a given transaction input. Note that the signature
       is prepended to the scriptSig field, i.e. additional data pushes necessary for more
       complex spends than P2PK (e.g. pubkey for P2PKH) can be already set before."""
    (sighash, err) = LegacySignatureHash(input_scriptpubkey, tx, input_index, sighash_type)
    assert err is None
    der_sig = privkey.sign_ecdsa(sighash)
    tx.vin[input_index].scriptSig = bytes(CScript([der_sig + bytes([sighash_type])])) + tx.vin[input_index].scriptSig
    tx.rehash()

# TODO: Allow cached hashPrevouts/hashSequence/hashOutputs to be provided.
# Performance optimization probably not necessary for python tests, however.
# Note that this corresponds to sigversion == 1 in EvalScript, which is used
# for version 0 witnesses.
def SegwitV0SignatureMsg(script, txTo, inIdx, hashtype, amount):

    hashPrevouts = 0
    hashSequence = 0
    hashOutputs = 0

    if not (hashtype & SIGHASH_ANYONECANPAY):
        serialize_prevouts = bytes()
        for i in txTo.vin:
            serialize_prevouts += i.prevout.serialize()
        hashPrevouts = uint256_from_str(keccak256(serialize_prevouts))

    if (not (hashtype & SIGHASH_ANYONECANPAY) and (hashtype & 0x1f) != SIGHASH_SINGLE and (hashtype & 0x1f) != SIGHASH_NONE):
        serialize_sequence = bytes()
        for i in txTo.vin:
            serialize_sequence += struct.pack("<I", i.nSequence)
        hashSequence = uint256_from_str(keccak256(serialize_sequence))

    if ((hashtype & 0x1f) != SIGHASH_SINGLE and (hashtype & 0x1f) != SIGHASH_NONE):
        serialize_outputs = bytes()
        for o in txTo.vout:
            serialize_outputs += o.serialize()
        hashOutputs = uint256_from_str(keccak256(serialize_outputs))
    elif ((hashtype & 0x1f) == SIGHASH_SINGLE and inIdx < len(txTo.vout)):
        serialize_outputs = txTo.vout[inIdx].serialize()
        hashOutputs = uint256_from_str(keccak256(serialize_outputs))

    ss = bytes()
    ss += txTo.version.to_bytes(4, "little")
    ss += ser_uint256(hashPrevouts)
    ss += ser_uint256(hashSequence)
    ss += txTo.vin[inIdx].prevout.serialize()
    ss += ser_string(script)
    ss += struct.pack("<q", amount)
    ss += struct.pack("<I", txTo.vin[inIdx].nSequence)
    ss += ser_uint256(hashOutputs)
    ss += txTo.nLockTime.to_bytes(4, "little")
    ss += struct.pack("<I", hashtype)
    return ss

def SegwitV0SignatureHash(*args, **kwargs):
    return keccak256(SegwitV0SignatureMsg(*args, **kwargs))

class TestFrameworkScript(unittest.TestCase):
    def test_bn2vch(self):
        self.assertEqual(bn2vch(0), bytes([]))
        self.assertEqual(bn2vch(1), bytes([0x01]))
        self.assertEqual(bn2vch(-1), bytes([0x81]))
        self.assertEqual(bn2vch(0x7F), bytes([0x7F]))
        self.assertEqual(bn2vch(-0x7F), bytes([0xFF]))
        self.assertEqual(bn2vch(0x80), bytes([0x80, 0x00]))
        self.assertEqual(bn2vch(-0x80), bytes([0x80, 0x80]))
        self.assertEqual(bn2vch(0xFF), bytes([0xFF, 0x00]))
        self.assertEqual(bn2vch(-0xFF), bytes([0xFF, 0x80]))
        self.assertEqual(bn2vch(0x100), bytes([0x00, 0x01]))
        self.assertEqual(bn2vch(-0x100), bytes([0x00, 0x81]))
        self.assertEqual(bn2vch(0x7FFF), bytes([0xFF, 0x7F]))
        self.assertEqual(bn2vch(-0x8000), bytes([0x00, 0x80, 0x80]))
        self.assertEqual(bn2vch(-0x7FFFFF), bytes([0xFF, 0xFF, 0xFF]))
        self.assertEqual(bn2vch(0x80000000), bytes([0x00, 0x00, 0x00, 0x80, 0x00]))
        self.assertEqual(bn2vch(-0x80000000), bytes([0x00, 0x00, 0x00, 0x80, 0x80]))
        self.assertEqual(bn2vch(0xFFFFFFFF), bytes([0xFF, 0xFF, 0xFF, 0xFF, 0x00]))
        self.assertEqual(bn2vch(123456789), bytes([0x15, 0xCD, 0x5B, 0x07]))
        self.assertEqual(bn2vch(-54321), bytes([0x31, 0xD4, 0x80]))

    def test_cscriptnum_encoding(self):
        # round-trip negative and multi-byte CScriptNums
        values = [0, 1, -1, -2, 127, 128, -255, 256, (1 << 15) - 1, -(1 << 16), (1 << 24) - 1, (1 << 31), 1 - (1 << 32), 1 << 40, 1500, -1500]
        for value in values:
            self.assertEqual(CScriptNum.decode(CScriptNum.encode(CScriptNum(value))), value)

def BIP341_sha_prevouts(txTo):
    return keccak256(b"".join(i.prevout.serialize() for i in txTo.vin))

def BIP341_sha_amounts(spent_utxos):
    return keccak256(b"".join(struct.pack("<q", u.nValue) for u in spent_utxos))

def BIP341_sha_scriptpubkeys(spent_utxos):
    return keccak256(b"".join(ser_string(u.scriptPubKey) for u in spent_utxos))

def BIP341_sha_sequences(txTo):
    return keccak256(b"".join(struct.pack("<I", i.nSequence) for i in txTo.vin))

def BIP341_sha_outputs(txTo):
    return keccak256(b"".join(o.serialize() for o in txTo.vout))

def TaprootSignatureMsg(txTo, spent_utxos, hash_type, input_index = 0, scriptpath = False, script = CScript(), codeseparator_pos = -1, annex = None, leaf_ver = LEAF_VERSION_TAPSCRIPT):
    assert (len(txTo.vin) == len(spent_utxos))
    assert (input_index < len(txTo.vin))
    out_type = SIGHASH_ALL if hash_type == 0 else hash_type & 3
    in_type = hash_type & SIGHASH_ANYONECANPAY
    spk = spent_utxos[input_index].scriptPubKey
    ss = bytes([0, hash_type]) # epoch, hash_type
    ss += txTo.version.to_bytes(4, "little")
    ss += txTo.nLockTime.to_bytes(4, "little")
    if in_type != SIGHASH_ANYONECANPAY:
        ss += BIP341_sha_prevouts(txTo)
        ss += BIP341_sha_amounts(spent_utxos)
        ss += BIP341_sha_scriptpubkeys(spent_utxos)
        ss += BIP341_sha_sequences(txTo)
    if out_type == SIGHASH_ALL:
        ss += BIP341_sha_outputs(txTo)
    spend_type = 0
    if annex is not None:
        spend_type |= 1
    if (scriptpath):
        spend_type |= 2
    ss += bytes([spend_type])
    if in_type == SIGHASH_ANYONECANPAY:
        ss += txTo.vin[input_index].prevout.serialize()
        ss += struct.pack("<q", spent_utxos[input_index].nValue)
        ss += ser_string(spk)
        ss += struct.pack("<I", txTo.vin[input_index].nSequence)
    else:
        ss += struct.pack("<I", input_index)
    if (spend_type & 1):
        ss += sha256(ser_string(annex))
    if out_type == SIGHASH_SINGLE:
        if input_index < len(txTo.vout):
            ss += sha256(txTo.vout[input_index].serialize())
        else:
            ss += bytes(0 for _ in range(32))
    if (scriptpath):
        ss += TaggedHash("TapLeaf", bytes([leaf_ver]) + ser_string(script))
        ss += bytes([0])
        ss += struct.pack("<i", codeseparator_pos)
    assert len(ss) ==  175 - (in_type == SIGHASH_ANYONECANPAY) * 49 - (out_type != SIGHASH_ALL and out_type != SIGHASH_SINGLE) * 32 + (annex is not None) * 32 + scriptpath * 37
    return ss

def TaprootSignatureHash(*args, **kwargs):
    return TaggedHash("TapSighash", TaprootSignatureMsg(*args, **kwargs))

def taproot_tree_helper(scripts):
    if len(scripts) == 0:
        return ([], bytes())
    if len(scripts) == 1:
        # One entry: treat as a leaf
        script = scripts[0]
        assert not callable(script)
        if isinstance(script, list):
            return taproot_tree_helper(script)
        assert isinstance(script, tuple)
        version = LEAF_VERSION_TAPSCRIPT
        name = script[0]
        code = script[1]
        if len(script) == 3:
            version = script[2]
        assert version & 1 == 0
        assert isinstance(code, bytes)
        h = TaggedHash("TapLeaf", bytes([version]) + ser_string(code))
        if name is None:
            return ([], h)
        return ([(name, version, code, bytes(), h)], h)
    elif len(scripts) == 2 and callable(scripts[1]):
        # Two entries, and the right one is a function
        left, left_h = taproot_tree_helper(scripts[0:1])
        right_h = scripts[1](left_h)
        left = [(name, version, script, control + right_h, leaf) for name, version, script, control, leaf in left]
        right = []
    else:
        # Two or more entries: descend into each side
        split_pos = len(scripts) // 2
        left, left_h = taproot_tree_helper(scripts[0:split_pos])
        right, right_h = taproot_tree_helper(scripts[split_pos:])
        left = [(name, version, script, control + right_h, leaf) for name, version, script, control, leaf in left]
        right = [(name, version, script, control + left_h, leaf) for name, version, script, control, leaf in right]
    if right_h < left_h:
        right_h, left_h = left_h, right_h
    h = TaggedHash("TapBranch", left_h + right_h)
    return (left + right, h)

# A TaprootInfo object has the following fields:
# - scriptPubKey: the scriptPubKey (witness v1 CScript)
# - internal_pubkey: the internal pubkey (32 bytes)
# - negflag: whether the pubkey in the scriptPubKey was negated from internal_pubkey+tweak*G (bool).
# - tweak: the tweak (32 bytes)
# - leaves: a dict of name -> TaprootLeafInfo objects for all known leaves
# - merkle_root: the script tree's Merkle root, or bytes() if no leaves are present
TaprootInfo = namedtuple("TaprootInfo", "scriptPubKey,internal_pubkey,negflag,tweak,leaves,merkle_root,output_pubkey")

# A TaprootLeafInfo object has the following fields:
# - script: the leaf script (CScript or bytes)
# - version: the leaf version (0xc0 for BIP342 tapscript)
# - merklebranch: the merkle branch to use for this leaf (32*N bytes)
TaprootLeafInfo = namedtuple("TaprootLeafInfo", "script,version,merklebranch,leaf_hash")

def taproot_construct(pubkey, scripts=None, treat_internal_as_infinity=False):
    """Construct a tree of Taproot spending conditions

    pubkey: a 32-byte xonly pubkey for the internal pubkey (bytes)
    scripts: a list of items; each item is either:
             - a (name, CScript or bytes, leaf version) tuple
             - a (name, CScript or bytes) tuple (defaulting to leaf version 0xc0)
             - another list of items (with the same structure)
             - a list of two items; the first of which is an item itself, and the
               second is a function. The function takes as input the Merkle root of the
               first item, and produces a (fictitious) partner to hash with.

    Returns: a TaprootInfo object
    """
    if scripts is None:
        scripts = []

    ret, h = taproot_tree_helper(scripts)
    tweak = TaggedHash("TapTweak", pubkey + h)
    if treat_internal_as_infinity:
        tweaked, negated = compute_xonly_pubkey(tweak)
    else:
        tweaked, negated = tweak_add_pubkey(pubkey, tweak)
    leaves = dict((name, TaprootLeafInfo(script, version, merklebranch, leaf)) for name, version, script, merklebranch, leaf in ret)
    return TaprootInfo(CScript([OP_1, tweaked]), pubkey, negated + 0, tweak, leaves, h, tweaked)

def is_op_success(o):
    return o == 0x50 or o == 0x62 or o == 0x89 or o == 0x8a or o == 0x8d or o == 0x8e or (o >= 0x7e and o <= 0x81) or (o >= 0x83 and o <= 0x86) or (o >= 0x95 and o <= 0x99) or (o >= 0xbb and o <= 0xfe)