Differential D10276 Diff 30408 test/functional/test_framework/txtools.py

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test/functional/test_framework/txtools.py

	#!/usr/bin/env python3			#!/usr/bin/env python3
	import random			import random
				import sys
				import unittest

	from .cdefs import MAX_TXOUT_PUBKEY_SCRIPT, MIN_TX_SIZE			from .cdefs import MIN_TX_SIZE
	from .messages import CTransaction, CTxOut, FromHex, ToHex			from .messages import CTransaction, CTxOut, FromHex, ToHex
	from .script import OP_RETURN, CScript			from .script import OP_RETURN, CScript

				MAX_OP_RETURN_PAYLOAD = 220
				VOUT_VALUE_SIZE = 8

	def pad_tx(tx, pad_to_size=MIN_TX_SIZE):
				def get_random_bytes(size: int) -> bytes:
				if sys.version_info >= (3, 9, 0):
				return random.randbytes(size)
				# slower workaround
				if not size:
				return b''
				return bytes.fromhex(f"{random.randrange(2*(8size)):0{2*size}x}")


				def pad_tx(tx: CTransaction, pad_to_size: int = MIN_TX_SIZE):
	"""			"""
	Pad a transaction with op_return junk data until it is at least pad_to_size, or			Pad a transaction with op_return junk data until it is at least pad_to_size,
	leave it alone if it's already bigger than that.			or leave it alone if it's already bigger than that.

				This function attempts to make the tx to be exactly of size pad_to_size.

				There is one case in which this is not possible: when the requested size
				is less than the current size plus the minimum vout overhead of 10 bytes.
				To get an exact size, make you sure you pad to a size of at least 10 more
				bytes than the input transaction.
	"""			"""
	curr_size = len(tx.serialize())			curr_size = len(tx.serialize())
	if curr_size >= pad_to_size:
	# Bail early txn is already big enough
	return

	# This code attempts to pad a transaction with opreturn vouts such that
	# it will be exactly pad_to_size. In order to do this we have to create
	# vouts of size x (maximum OP_RETURN size - vout overhead), plus the final
	# one subsumes any runoff which would be less than vout overhead.
	#
	# There are two cases where this is not possible:
	# 1. The transaction size is between pad_to_size and pad_to_size - extrabytes
	# 2. The transaction is already greater than pad_to_size
	#
	# Visually:
	# \| .. x .. \| .. x .. \| .. x .. \| .. x + desired_size % x \|
	# VOUT_1 VOUT_2 VOUT_3 VOUT_4
	# txout.value + txout.pk_script bytes + op_return
	extra_bytes = 8 + 1 + 1
	required_padding = pad_to_size - curr_size			required_padding = pad_to_size - curr_size

	while required_padding > 0:			while required_padding > 0:
	# We need at least extra_bytes left over each time, or we can't			if required_padding <= 10:
	# subsume the final (and possibly undersized) iteration of the loop			# Smallest possible padding with an empty OP_RETURN vout:
	padding_len = min(required_padding,			# vout.value (8 bytes) + script length (1) + OP_RETURN (1)
	MAX_TXOUT_PUBKEY_SCRIPT - extra_bytes)
	assert padding_len >= 0, "Can't pad less than 0 bytes, trying {}".format(
	padding_len)
	# We will end up with less than 1 UTXO of bytes after this, add
	# them to this txn
	next_iteration_padding = required_padding - padding_len - extra_bytes
	if next_iteration_padding > 0 and next_iteration_padding < extra_bytes:
	padding_len += next_iteration_padding

	# If we're at exactly, or below, extra_bytes we don't want a 1 extra
	# byte padding
	if padding_len <= extra_bytes:
	tx.vout.append(CTxOut(0, CScript([OP_RETURN])))			tx.vout.append(CTxOut(0, CScript([OP_RETURN])))
	else:			break
	# Subtract the overhead for the TxOut
	padding_len -= extra_bytes			# The total padding size, for a payload < 0x4c, is:
	padding = random.randrange(			# vout.value (8 bytes) + script_length (1) + OP_RETURN (1) +
	1 << 8 * padding_len - 2, 1 << 8 * padding_len - 1)			# + data length (1) + data
	tx.vout.append(			data_size = required_padding - VOUT_VALUE_SIZE - 3
	CTxOut(0, CScript([OP_RETURN, padding])))			was_op_pushdata1_used = True

				script_operations = []
				if data_size <= 0x4c:
				was_op_pushdata1_used = False
				if data_size == 0x4c:
				# Adding one more byte to the data causes two more bytes to be
				# added to the tx size, because of the need for OP_PUSHDATA1.
				# So remove 10 bytes to add an empty OP_RETURN vout instead in
				# the next iteration.
				data_size -= 10
				elif MAX_OP_RETURN_PAYLOAD < data_size <= MAX_OP_RETURN_PAYLOAD + 10:
				# We require more than one VOUT, but the extra space needed is
				# less than the VOUT footprint. Remove 10 bytes from the current
				# data to avoid overpadding in next iteration.
				data_size -= 10
				elif data_size > MAX_OP_RETURN_PAYLOAD + 10:
				# Use a full OP_RETURN.
				data_size = MAX_OP_RETURN_PAYLOAD + 1

				if was_op_pushdata1_used:
				# OP_PUSHDATA1 adds 1 extra byte to the transaction size.
				data_size -= 1
				required_padding -= 1

				required_padding -= data_size + VOUT_VALUE_SIZE + 3

				script_operations += [
				OP_RETURN,
				get_random_bytes(data_size)
				]
				tx.vout.append(CTxOut(0, CScript(script_operations)))

	curr_size = len(tx.serialize())
	required_padding = pad_to_size - curr_size
	assert curr_size >= pad_to_size, "{} !>= {}".format(curr_size, pad_to_size)
	tx.rehash()			tx.rehash()


	def pad_raw_tx(rawtx_hex, min_size=MIN_TX_SIZE):			def pad_raw_tx(rawtx_hex, min_size=MIN_TX_SIZE):
	"""			"""
	Pad a raw transaction with OP_RETURN data until it reaches at least min_size			Pad a raw transaction with OP_RETURN data until it reaches at least min_size
	"""			"""
	tx = CTransaction()			tx = CTransaction()
	FromHex(tx, rawtx_hex)			FromHex(tx, rawtx_hex)
	pad_tx(tx, min_size)			pad_tx(tx, min_size)
	return ToHex(tx)			return ToHex(tx)


				class TestFrameworkScript(unittest.TestCase):
				def test_pad_raw_tx(self):
				raw_tx = (
				"0100000001dd22777f85ab958c065cabced6115c4a2604abb9a2273f0eedce14a"
				"55c7b1201000000000201510000000001ebf802950000000017a914da1745e9b5"
				"49bd0bfa1a569971c77eba30cd5a4b8700000000"
				)

				# Helper functions
				def rawtx_length(rawtx):
				return len(bytes.fromhex(rawtx))

				def test_size(requested_size, expected_size):
				self.assertEqual(
				rawtx_length(pad_raw_tx(raw_tx, requested_size)),
				expected_size)

				self.assertEqual(rawtx_length(raw_tx), 85)

				# The tx size is never reduced.
				for size in [-1, 0, 1, 83, 84, 85]:
				test_size(size, expected_size=85)

				# The first new VOUT is added as soon as the requested size is more
				# than the initial size. The next 9 sizes are overpadded to 95 bytes,
				# because a VOUT with an empty OP_RETURN is the minimum data we can
				# add.
				for size in [86, 87, 88, 89, 90, 91, 92, 93, 94]:
				test_size(requested_size=size,
				expected_size=95)

				# After that, the size is exactly as expected.
				for size in range(95, 1000):
				test_size(requested_size=size,
				expected_size=size)