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-bitcoinlib.
"""

from collections import namedtuple
import struct
import unittest
from typing import List, Dict

from .key import TaggedHash, tweak_add_pubkey, compute_xonly_pubkey

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

from .ripemd160 import ripemd160

MAX_SCRIPT_ELEMENT_SIZE = 520
MAX_PUBKEYS_PER_MULTI_A = 999
LOCKTIME_THRESHOLD = 500000000
ANNEX_TAG = 0x50

LEAF_VERSION_TAPSCRIPT = 0xc0

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

def bn2vch(v):
    """Convert number to bitcoin-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


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 (hash256(msg), err)

# 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(hash256(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(hash256(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(hash256(serialize_outputs))
    elif ((hashtype & 0x1f) == SIGHASH_SINGLE and inIdx < len(txTo.vout)):
        serialize_outputs = txTo.vout[inIdx].serialize()
        hashOutputs = uint256_from_str(hash256(serialize_outputs))

    ss = bytes()
    ss += struct.pack("<i", txTo.nVersion)
    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 += struct.pack("<i", txTo.nLockTime)
    ss += struct.pack("<I", hashtype)
    return ss

def SegwitV0SignatureHash(*args, **kwargs):
    return hash256(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 sha256(b"".join(i.prevout.serialize() for i in txTo.vin))

def BIP341_sha_amounts(spent_utxos):
    return sha256(b"".join(struct.pack("<q", u.nValue) for u in spent_utxos))

def BIP341_sha_scriptpubkeys(spent_utxos):
    return sha256(b"".join(ser_string(u.scriptPubKey) for u in spent_utxos))

def BIP341_sha_sequences(txTo):
    return sha256(b"".join(struct.pack("<I", i.nSequence) for i in txTo.vin))

def BIP341_sha_outputs(txTo):
    return sha256(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 += struct.pack("<i", txTo.nVersion)
    ss += struct.pack("<I", txTo.nLockTime)
    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)