bitcoin/test/functional/p2p_segwit.py

#!/usr/bin/env python3
# Copyright (c) 2016-2017 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Test segwit transactions and blocks on P2P network."""
from binascii import hexlify
import math
import random
import struct
import time

from test_framework.blocktools import create_block, create_coinbase, add_witness_commitment, get_witness_script, WITNESS_COMMITMENT_HEADER
from test_framework.key import CECKey, CPubKey
from test_framework.messages import (
    BIP125_SEQUENCE_NUMBER,
    CBlock,
    CBlockHeader,
    CInv,
    COutPoint,
    CTransaction,
    CTxIn,
    CTxInWitness,
    CTxOut,
    CTxWitness,
    MAX_BLOCK_BASE_SIZE,
    MSG_WITNESS_FLAG,
    NODE_NETWORK,
    NODE_WITNESS,
    msg_block,
    msg_getdata,
    msg_headers,
    msg_inv,
    msg_tx,
    msg_witness_block,
    msg_witness_tx,
    ser_uint256,
    ser_vector,
    sha256,
    uint256_from_str,
)
from test_framework.mininode import (
    P2PInterface,
    mininode_lock,
)
from test_framework.script import (
    CScript,
    CScriptNum,
    CScriptOp,
    OP_0,
    OP_1,
    OP_16,
    OP_2DROP,
    OP_CHECKMULTISIG,
    OP_CHECKSIG,
    OP_DROP,
    OP_DUP,
    OP_ELSE,
    OP_ENDIF,
    OP_EQUAL,
    OP_EQUALVERIFY,
    OP_HASH160,
    OP_IF,
    OP_RETURN,
    OP_TRUE,
    SIGHASH_ALL,
    SIGHASH_ANYONECANPAY,
    SIGHASH_NONE,
    SIGHASH_SINGLE,
    SegwitVersion1SignatureHash,
    SignatureHash,
    hash160,
)
from test_framework.test_framework import BitcoinTestFramework
from test_framework.util import (
    assert_equal,
    bytes_to_hex_str,
    connect_nodes,
    get_bip9_status,
    hex_str_to_bytes,
    sync_blocks,
    sync_mempools,
)

# The versionbit bit used to signal activation of SegWit
VB_WITNESS_BIT = 1
VB_PERIOD = 144
VB_TOP_BITS = 0x20000000

MAX_SIGOP_COST = 80000

class UTXO():
    """Used to keep track of anyone-can-spend outputs that we can use in the tests."""
    def __init__(self, sha256, n, value):
        self.sha256 = sha256
        self.n = n
        self.nValue = value

def get_p2pkh_script(pubkeyhash):
    """Get the script associated with a P2PKH."""
    return CScript([CScriptOp(OP_DUP), CScriptOp(OP_HASH160), pubkeyhash, CScriptOp(OP_EQUALVERIFY), CScriptOp(OP_CHECKSIG)])

def sign_p2pk_witness_input(script, tx_to, in_idx, hashtype, value, key):
    """Add signature for a P2PK witness program."""
    tx_hash = SegwitVersion1SignatureHash(script, tx_to, in_idx, hashtype, value)
    signature = key.sign(tx_hash) + chr(hashtype).encode('latin-1')
    tx_to.wit.vtxinwit[in_idx].scriptWitness.stack = [signature, script]
    tx_to.rehash()

def get_virtual_size(witness_block):
    """Calculate the virtual size of a witness block.

    Virtual size is base + witness/4."""
    base_size = len(witness_block.serialize(with_witness=False))
    total_size = len(witness_block.serialize(with_witness=True))
    # the "+3" is so we round up
    vsize = int((3 * base_size + total_size + 3) / 4)
    return vsize

def test_transaction_acceptance(rpc, p2p, tx, with_witness, accepted, reason=None):
    """Send a transaction to the node and check that it's accepted to the mempool

    - Submit the transaction over the p2p interface
    - use the getrawmempool rpc to check for acceptance."""
    tx_message = msg_tx(tx)
    if with_witness:
        tx_message = msg_witness_tx(tx)
    p2p.send_message(tx_message)
    p2p.sync_with_ping()
    assert_equal(tx.hash in rpc.getrawmempool(), accepted)
    if (reason is not None and not accepted):
        # Check the rejection reason as well.
        with mininode_lock:
            assert_equal(p2p.last_message["reject"].reason, reason)

def test_witness_block(rpc, p2p, block, accepted, with_witness=True, reason=None):
    """Send a block to the node and check that it's accepted

    - Submit the block over the p2p interface
    - use the getbestblockhash rpc to check for acceptance."""
    if with_witness:
        p2p.send_message(msg_witness_block(block))
    else:
        p2p.send_message(msg_block(block))
    p2p.sync_with_ping()
    assert_equal(rpc.getbestblockhash() == block.hash, accepted)
    if (reason is not None and not accepted):
        # Check the rejection reason as well.
        with mininode_lock:
            assert_equal(p2p.last_message["reject"].reason, reason)

class TestP2PConn(P2PInterface):
    def __init__(self):
        super().__init__()
        self.getdataset = set()

    def on_getdata(self, message):
        for inv in message.inv:
            self.getdataset.add(inv.hash)

    def announce_tx_and_wait_for_getdata(self, tx, timeout=60, success=True):
        with mininode_lock:
            self.last_message.pop("getdata", None)
        self.send_message(msg_inv(inv=[CInv(1, tx.sha256)]))
        if success:
            self.wait_for_getdata(timeout)
        else:
            time.sleep(timeout)
            assert not self.last_message.get("getdata")

    def announce_block_and_wait_for_getdata(self, block, use_header, timeout=60):
        with mininode_lock:
            self.last_message.pop("getdata", None)
            self.last_message.pop("getheaders", None)
        msg = msg_headers()
        msg.headers = [CBlockHeader(block)]
        if use_header:
            self.send_message(msg)
        else:
            self.send_message(msg_inv(inv=[CInv(2, block.sha256)]))
            self.wait_for_getheaders()
            self.send_message(msg)
        self.wait_for_getdata()

    def request_block(self, blockhash, inv_type, timeout=60):
        with mininode_lock:
            self.last_message.pop("block", None)
        self.send_message(msg_getdata(inv=[CInv(inv_type, blockhash)]))
        self.wait_for_block(blockhash, timeout)
        return self.last_message["block"].block

class SegWitTest(BitcoinTestFramework):
    def set_test_params(self):
        self.setup_clean_chain = True
        self.num_nodes = 3
        # This test tests SegWit both pre and post-activation, so use the normal BIP9 activation.
        self.extra_args = [["-whitelist=127.0.0.1", "-vbparams=segwit:0:999999999999"], ["-whitelist=127.0.0.1", "-acceptnonstdtxn=0", "-vbparams=segwit:0:999999999999"], ["-whitelist=127.0.0.1", "-vbparams=segwit:0:0"]]

    def setup_network(self):
        self.setup_nodes()
        connect_nodes(self.nodes[0], 1)
        connect_nodes(self.nodes[0], 2)
        self.sync_all()

    # Helper functions

    def build_next_block(self, version=4):
        """Build a block on top of node0's tip."""
        tip = self.nodes[0].getbestblockhash()
        height = self.nodes[0].getblockcount() + 1
        block_time = self.nodes[0].getblockheader(tip)["mediantime"] + 1
        block = create_block(int(tip, 16), create_coinbase(height), block_time)
        block.version = version
        block.rehash()
        return block

    def update_witness_block_with_transactions(self, block, tx_list, nonce=0):
        """Add list of transactions to block, adds witness commitment, then solves."""
        block.vtx.extend(tx_list)
        add_witness_commitment(block, nonce)
        block.solve()

    def run_test(self):
        # Setup the p2p connections and start up the network thread.
        # self.test_node sets NODE_WITNESS|NODE_NETWORK
        self.test_node = self.nodes[0].add_p2p_connection(TestP2PConn(), services=NODE_NETWORK | NODE_WITNESS)
        # self.old_node sets only NODE_NETWORK
        self.old_node = self.nodes[0].add_p2p_connection(TestP2PConn(), services=NODE_NETWORK)
        # self.std_node is for testing node1 (fRequireStandard=true)
        self.std_node = self.nodes[1].add_p2p_connection(TestP2PConn(), services=NODE_NETWORK | NODE_WITNESS)

        # Keep a place to store utxo's that can be used in later tests
        self.utxo = []

        # Test logic begins here
        self.test_node.wait_for_verack()

        self.log.info("Starting tests before segwit lock in:")

        self.test_witness_services()  # Verifies NODE_WITNESS
        self.test_non_witness_transaction()  # non-witness tx's are accepted
        self.test_unnecessary_witness_before_segwit_activation()
        self.test_v0_outputs_arent_spendable()
        self.test_block_relay(segwit_activated=False)

        # Advance to segwit being 'started'
        self.advance_to_segwit_started()
        sync_blocks(self.nodes)
        self.test_getblocktemplate_before_lockin()

        sync_blocks(self.nodes)

        # At lockin, nothing should change.
        self.log.info("Testing behavior post lockin, pre-activation")
        self.advance_to_segwit_lockin()

        # Retest unnecessary witnesses
        self.test_unnecessary_witness_before_segwit_activation()
        self.test_witness_tx_relay_before_segwit_activation()
        self.test_block_relay(segwit_activated=False)
        self.test_standardness_v0(segwit_activated=False)

        sync_blocks(self.nodes)

        # Now activate segwit
        self.log.info("Testing behavior after segwit activation")
        self.advance_to_segwit_active()

        sync_blocks(self.nodes)

        # Test P2SH witness handling again
        self.test_p2sh_witness(segwit_activated=True)
        self.test_witness_commitments()
        self.test_block_malleability()
        self.test_witness_block_size()
        self.test_submit_block()
        self.test_extra_witness_data()
        self.test_max_witness_push_length()
        self.test_max_witness_program_length()
        self.test_witness_input_length()
        self.test_block_relay(segwit_activated=True)
        self.test_tx_relay_after_segwit_activation()
        self.test_standardness_v0(segwit_activated=True)
        self.test_segwit_versions()
        self.test_premature_coinbase_witness_spend()
        self.test_uncompressed_pubkey()
        self.test_signature_version_1()
        self.test_non_standard_witness_blinding()
        self.test_non_standard_witness()
        sync_blocks(self.nodes)
        self.test_upgrade_after_activation(node_id=2)
        self.test_witness_sigops()

    # Individual tests

    def test_witness_services(self):
        self.log.info("Verifying NODE_WITNESS service bit")
        assert((self.test_node.nServices & NODE_WITNESS) != 0)

    def test_non_witness_transaction(self):
        """See if sending a regular transaction works, and create a utxo to use in later tests."""
        # Mine a block with an anyone-can-spend coinbase,
        # let it mature, then try to spend it.
        self.log.info("Testing non-witness transaction")
        block = self.build_next_block(version=1)
        block.solve()
        self.test_node.send_message(msg_block(block))
        self.test_node.sync_with_ping()  # make sure the block was processed
        txid = block.vtx[0].sha256

        self.nodes[0].generate(99)  # let the block mature

        # Create a transaction that spends the coinbase
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(txid, 0), b""))
        tx.vout.append(CTxOut(49 * 100000000, CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))
        tx.calc_sha256()

        # Check that serializing it with or without witness is the same
        # This is a sanity check of our testing framework.
        assert_equal(msg_tx(tx).serialize(), msg_witness_tx(tx).serialize())

        self.test_node.send_message(msg_witness_tx(tx))
        self.test_node.sync_with_ping()  # make sure the tx was processed
        assert(tx.hash in self.nodes[0].getrawmempool())
        # Save this transaction for later
        self.utxo.append(UTXO(tx.sha256, 0, 49 * 100000000))
        self.nodes[0].generate(1)

    def test_unnecessary_witness_before_segwit_activation(self):
        """Verify that blocks with witnesses are rejected before activation."""
        self.log.info("Testing behavior of unnecessary witnesses")
        # For now, rely on earlier tests to have created at least one utxo for
        # us to use
        assert(len(self.utxo) > 0)
        assert(get_bip9_status(self.nodes[0], 'segwit')['status'] != 'active')

        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, CScript([OP_TRUE])))
        tx.wit.vtxinwit.append(CTxInWitness())
        tx.wit.vtxinwit[0].scriptWitness.stack = [CScript([CScriptNum(1)])]

        # Verify the hash with witness differs from the txid
        # (otherwise our testing framework must be broken!)
        tx.rehash()
        assert(tx.sha256 != tx.calc_sha256(with_witness=True))

        # Construct a segwit-signaling block that includes the transaction.
        block = self.build_next_block(version=(VB_TOP_BITS | (1 << VB_WITNESS_BIT)))
        self.update_witness_block_with_transactions(block, [tx])
        # Sending witness data before activation is not allowed (anti-spam
        # rule).
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)
        # TODO: fix synchronization so we can test reject reason
        # Right now, bitcoind delays sending reject messages for blocks
        # until the future, making synchronization here difficult.
        # assert_equal(self.test_node.last_message["reject"].reason, "unexpected-witness")

        # But it should not be permanently marked bad...
        # Resend without witness information.
        self.test_node.send_message(msg_block(block))
        self.test_node.sync_with_ping()
        assert_equal(self.nodes[0].getbestblockhash(), block.hash)

        sync_blocks(self.nodes)

        # Update our utxo list; we spent the first entry.
        self.utxo.pop(0)
        self.utxo.append(UTXO(tx.sha256, 0, tx.vout[0].nValue))

    def test_block_relay(self, segwit_activated):
        """Test that block requests to NODE_WITNESS peer are with MSG_WITNESS_FLAG.

        This is true regardless of segwit activation.
        Also test that we don't ask for blocks from unupgraded peers."""
        self.log.info("Testing block relay")

        blocktype = 2 | MSG_WITNESS_FLAG

        # test_node has set NODE_WITNESS, so all getdata requests should be for
        # witness blocks.
        # Test announcing a block via inv results in a getdata, and that
        # announcing a version 4 or random VB block with a header results in a getdata
        block1 = self.build_next_block()
        block1.solve()

        self.test_node.announce_block_and_wait_for_getdata(block1, use_header=False)
        assert(self.test_node.last_message["getdata"].inv[0].type == blocktype)
        test_witness_block(self.nodes[0].rpc, self.test_node, block1, True)

        block2 = self.build_next_block(version=4)
        block2.solve()

        self.test_node.announce_block_and_wait_for_getdata(block2, use_header=True)
        assert(self.test_node.last_message["getdata"].inv[0].type == blocktype)
        test_witness_block(self.nodes[0].rpc, self.test_node, block2, True)

        block3 = self.build_next_block(version=(VB_TOP_BITS | (1 << 15)))
        block3.solve()
        self.test_node.announce_block_and_wait_for_getdata(block3, use_header=True)
        assert(self.test_node.last_message["getdata"].inv[0].type == blocktype)
        test_witness_block(self.nodes[0].rpc, self.test_node, block3, True)

        # Check that we can getdata for witness blocks or regular blocks,
        # and the right thing happens.
        if not segwit_activated:
            # Before activation, we should be able to request old blocks with
            # or without witness, and they should be the same.
            chain_height = self.nodes[0].getblockcount()
            # Pick 10 random blocks on main chain, and verify that getdata's
            # for MSG_BLOCK, MSG_WITNESS_BLOCK, and rpc getblock() are equal.
            all_heights = list(range(chain_height + 1))
            random.shuffle(all_heights)
            all_heights = all_heights[0:10]
            for height in all_heights:
                block_hash = self.nodes[0].getblockhash(height)
                rpc_block = self.nodes[0].getblock(block_hash, False)
                block_hash = int(block_hash, 16)
                block = self.test_node.request_block(block_hash, 2)
                wit_block = self.test_node.request_block(block_hash, 2 | MSG_WITNESS_FLAG)
                assert_equal(block.serialize(True), wit_block.serialize(True))
                assert_equal(block.serialize(), hex_str_to_bytes(rpc_block))
        else:
            # After activation, witness blocks and non-witness blocks should
            # be different.  Verify rpc getblock() returns witness blocks, while
            # getdata respects the requested type.
            block = self.build_next_block()
            self.update_witness_block_with_transactions(block, [])
            # This gives us a witness commitment.
            assert(len(block.vtx[0].wit.vtxinwit) == 1)
            assert(len(block.vtx[0].wit.vtxinwit[0].scriptWitness.stack) == 1)
            test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
            # Now try to retrieve it...
            rpc_block = self.nodes[0].getblock(block.hash, False)
            non_wit_block = self.test_node.request_block(block.sha256, 2)
            wit_block = self.test_node.request_block(block.sha256, 2 | MSG_WITNESS_FLAG)
            assert_equal(wit_block.serialize(True), hex_str_to_bytes(rpc_block))
            assert_equal(wit_block.serialize(False), non_wit_block.serialize())
            assert_equal(wit_block.serialize(True), block.serialize(True))

            # Test size, vsize, weight
            rpc_details = self.nodes[0].getblock(block.hash, True)
            assert_equal(rpc_details["size"], len(block.serialize(True)))
            assert_equal(rpc_details["strippedsize"], len(block.serialize(False)))
            weight = 3 * len(block.serialize(False)) + len(block.serialize(True))
            assert_equal(rpc_details["weight"], weight)

            # Upgraded node should not ask for blocks from unupgraded
            block4 = self.build_next_block(version=4)
            block4.solve()
            self.old_node.getdataset = set()

            # Blocks can be requested via direct-fetch (immediately upon processing the announcement)
            # or via parallel download (with an indeterminate delay from processing the announcement)
            # so to test that a block is NOT requested, we could guess a time period to sleep for,
            # and then check. We can avoid the sleep() by taking advantage of transaction getdata's
            # being processed after block getdata's, and announce a transaction as well,
            # and then check to see if that particular getdata has been received.
            # Since 0.14, inv's will only be responded to with a getheaders, so send a header
            # to announce this block.
            msg = msg_headers()
            msg.headers = [CBlockHeader(block4)]
            self.old_node.send_message(msg)
            self.old_node.announce_tx_and_wait_for_getdata(block4.vtx[0])
            assert(block4.sha256 not in self.old_node.getdataset)

    def test_v0_outputs_arent_spendable(self):
        """Test that v0 outputs aren't spendable before segwit activation.

        ~6 months after segwit activation, the SCRIPT_VERIFY_WITNESS flag was
        backdated so that it applies to all blocks, going back to the genesis
        block.

        Consequently, version 0 witness outputs are never spendable without
        witness, and so can't be spent before segwit activation (the point at which
        blocks are permitted to contain witnesses)."""

        self.log.info("Testing that v0 witness program outputs aren't spendable before activation")

        assert len(self.utxo), "self.utxo is empty"

        # Create two outputs, a p2wsh and p2sh-p2wsh
        witness_program = CScript([OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        p2sh_pubkey = hash160(script_pubkey)
        p2sh_script_pubkey = CScript([OP_HASH160, p2sh_pubkey, OP_EQUAL])

        value = self.utxo[0].nValue // 3

        tx = CTransaction()
        tx.vin = [CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b'')]
        tx.vout = [CTxOut(value, script_pubkey), CTxOut(value, p2sh_script_pubkey)]
        tx.vout.append(CTxOut(value, CScript([OP_TRUE])))
        tx.rehash()
        txid = tx.sha256

        # Add it to a block
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        # Verify that segwit isn't activated. A block serialized with witness
        # should be rejected prior to activation.
        test_witness_block(self.nodes[0], self.test_node, block, accepted=False, with_witness=True, reason=b'unexpected-witness')
        # Now send the block without witness. It should be accepted
        test_witness_block(self.nodes[0], self.test_node, block, accepted=True, with_witness=False)

        # Now try to spend the outputs. This should fail since SCRIPT_VERIFY_WITNESS is always enabled.
        p2wsh_tx = CTransaction()
        p2wsh_tx.vin = [CTxIn(COutPoint(txid, 0), b'')]
        p2wsh_tx.vout = [CTxOut(value, CScript([OP_TRUE]))]
        p2wsh_tx.wit.vtxinwit.append(CTxInWitness())
        p2wsh_tx.wit.vtxinwit[0].scriptWitness.stack = [CScript([OP_TRUE])]
        p2wsh_tx.rehash()

        p2sh_p2wsh_tx = CTransaction()
        p2sh_p2wsh_tx.vin = [CTxIn(COutPoint(txid, 1), CScript([script_pubkey]))]
        p2sh_p2wsh_tx.vout = [CTxOut(value, CScript([OP_TRUE]))]
        p2sh_p2wsh_tx.wit.vtxinwit.append(CTxInWitness())
        p2sh_p2wsh_tx.wit.vtxinwit[0].scriptWitness.stack = [CScript([OP_TRUE])]
        p2sh_p2wsh_tx.rehash()

        for tx in [p2wsh_tx, p2sh_p2wsh_tx]:

            block = self.build_next_block()
            self.update_witness_block_with_transactions(block, [tx])

            # When the block is serialized with a witness, the block will be rejected because witness
            # data isn't allowed in blocks that don't commit to witness data.
            test_witness_block(self.nodes[0], self.test_node, block, accepted=False, with_witness=True, reason=b'unexpected-witness')

            # When the block is serialized without witness, validation fails because the transaction is
            # invalid (transactions are always validated with SCRIPT_VERIFY_WITNESS so a segwit v0 transaction
            # without a witness is invalid).
            # Note: The reject reason for this failure could be
            # 'block-validation-failed' (if script check threads > 1) or
            # 'non-mandatory-script-verify-flag (Witness program was passed an
            # empty witness)' (otherwise).
            # TODO: support multiple acceptable reject reasons.
            test_witness_block(self.nodes[0], self.test_node, block, accepted=False, with_witness=False)

        self.utxo.pop(0)
        self.utxo.append(UTXO(txid, 2, value))

    def advance_to_segwit_started(self):
        """Mine enough blocks for segwit's vb state to be 'started'."""
        height = self.nodes[0].getblockcount()
        # Will need to rewrite the tests here if we are past the first period
        assert(height < VB_PERIOD - 1)
        # Genesis block is 'defined'.
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'defined')
        # Advance to end of period, status should now be 'started'
        self.nodes[0].generate(VB_PERIOD - height - 1)
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'started')

    def test_getblocktemplate_before_lockin(self):
        self.log.info("Testing getblocktemplate setting of segwit versionbit (before lockin)")
        # Node0 is segwit aware, node2 is not.
        for node in [self.nodes[0], self.nodes[2]]:
            gbt_results = node.getblocktemplate()
            block_version = gbt_results['version']
            # If we're not indicating segwit support, we will still be
            # signalling for segwit activation.
            assert_equal((block_version & (1 << VB_WITNESS_BIT) != 0), node == self.nodes[0])
            # If we don't specify the segwit rule, then we won't get a default
            # commitment.
            assert('default_witness_commitment' not in gbt_results)

        # Workaround:
        # Can either change the tip, or change the mempool and wait 5 seconds
        # to trigger a recomputation of getblocktemplate.
        txid = int(self.nodes[0].sendtoaddress(self.nodes[0].getnewaddress(), 1), 16)
        # Using mocktime lets us avoid sleep()
        sync_mempools(self.nodes)
        self.nodes[0].setmocktime(int(time.time()) + 10)
        self.nodes[2].setmocktime(int(time.time()) + 10)

        for node in [self.nodes[0], self.nodes[2]]:
            gbt_results = node.getblocktemplate({"rules": ["segwit"]})
            block_version = gbt_results['version']
            if node == self.nodes[2]:
                # If this is a non-segwit node, we should still not get a witness
                # commitment, nor a version bit signalling segwit.
                assert_equal(block_version & (1 << VB_WITNESS_BIT), 0)
                assert('default_witness_commitment' not in gbt_results)
            else:
                # For segwit-aware nodes, check the version bit and the witness
                # commitment are correct.
                assert(block_version & (1 << VB_WITNESS_BIT) != 0)
                assert('default_witness_commitment' in gbt_results)
                witness_commitment = gbt_results['default_witness_commitment']

                # Check that default_witness_commitment is present.
                witness_root = CBlock.get_merkle_root([ser_uint256(0),
                                                       ser_uint256(txid)])
                script = get_witness_script(witness_root, 0)
                assert_equal(witness_commitment, bytes_to_hex_str(script))

        # undo mocktime
        self.nodes[0].setmocktime(0)
        self.nodes[2].setmocktime(0)

    def advance_to_segwit_lockin(self):
        """Mine enough blocks to lock in segwit, but don't activate."""
        # TODO: we could verify that lockin only happens at the right threshold of
        # signalling blocks, rather than just at the right period boundary.

        height = self.nodes[0].getblockcount()
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'started')
        # Advance to end of period, and verify lock-in happens at the end
        self.nodes[0].generate(VB_PERIOD - 1)
        height = self.nodes[0].getblockcount()
        assert((height % VB_PERIOD) == VB_PERIOD - 2)
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'started')
        self.nodes[0].generate(1)
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'locked_in')

    def test_witness_tx_relay_before_segwit_activation(self):
        self.log.info("Testing relay of witness transactions")
        # Generate a transaction that doesn't require a witness, but send it
        # with a witness.  Should be rejected for premature-witness, but should
        # not be added to recently rejected list.
        assert(len(self.utxo))
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))
        tx.wit.vtxinwit.append(CTxInWitness())
        tx.wit.vtxinwit[0].scriptWitness.stack = [b'a']
        tx.rehash()

        tx_hash = tx.sha256
        tx_value = tx.vout[0].nValue

        # Verify that if a peer doesn't set nServices to include NODE_WITNESS,
        # the getdata is just for the non-witness portion.
        self.old_node.announce_tx_and_wait_for_getdata(tx)
        assert(self.old_node.last_message["getdata"].inv[0].type == 1)

        # Since we haven't delivered the tx yet, inv'ing the same tx from
        # a witness transaction ought not result in a getdata.
        self.test_node.announce_tx_and_wait_for_getdata(tx, timeout=2, success=False)

        # Delivering this transaction with witness should fail (no matter who
        # its from)
        assert_equal(len(self.nodes[0].getrawmempool()), 0)
        assert_equal(len(self.nodes[1].getrawmempool()), 0)
        test_transaction_acceptance(self.nodes[0].rpc, self.old_node, tx, with_witness=True, accepted=False)
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=True, accepted=False)

        # But eliminating the witness should fix it
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=False, accepted=True)

        # Cleanup: mine the first transaction and update utxo
        self.nodes[0].generate(1)
        assert_equal(len(self.nodes[0].getrawmempool()), 0)

        self.utxo.pop(0)
        self.utxo.append(UTXO(tx_hash, 0, tx_value))

    def test_standardness_v0(self, segwit_activated):
        """Test V0 txout standardness.

        V0 segwit outputs and inputs are always standard.
        V0 segwit inputs may only be mined after activation, but not before."""

        self.log.info("Testing standardness of v0 outputs (%s activation)" % ("after" if segwit_activated else "before"))
        assert(len(self.utxo))

        witness_program = CScript([OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        p2sh_pubkey = hash160(witness_program)
        p2sh_script_pubkey = CScript([OP_HASH160, p2sh_pubkey, OP_EQUAL])

        # First prepare a p2sh output (so that spending it will pass standardness)
        p2sh_tx = CTransaction()
        p2sh_tx.vin = [CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b"")]
        p2sh_tx.vout = [CTxOut(self.utxo[0].nValue - 1000, p2sh_script_pubkey)]
        p2sh_tx.rehash()

        # Mine it on test_node to create the confirmed output.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2sh_tx, with_witness=True, accepted=True)
        self.nodes[0].generate(1)
        sync_blocks(self.nodes)

        # Now test standardness of v0 P2WSH outputs.
        # Start by creating a transaction with two outputs.
        tx = CTransaction()
        tx.vin = [CTxIn(COutPoint(p2sh_tx.sha256, 0), CScript([witness_program]))]
        tx.vout = [CTxOut(p2sh_tx.vout[0].nValue - 10000, script_pubkey)]
        tx.vout.append(CTxOut(8000, script_pubkey))  # Might burn this later
        tx.vin[0].nSequence = BIP125_SEQUENCE_NUMBER  # Just to have the option to bump this tx from the mempool
        tx.rehash()

        # This is always accepted, since the mempool policy is to consider segwit as always active
        # and thus allow segwit outputs
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx, with_witness=True, accepted=True)

        # Now create something that looks like a P2PKH output. This won't be spendable.
        script_pubkey = CScript([OP_0, hash160(witness_hash)])
        tx2 = CTransaction()
        # tx was accepted, so we spend the second output.
        tx2.vin = [CTxIn(COutPoint(tx.sha256, 1), b"")]
        tx2.vout = [CTxOut(7000, script_pubkey)]
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
        tx2.rehash()

        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx2, with_witness=True, accepted=True)

        # Now update self.utxo for later tests.
        tx3 = CTransaction()
        # tx and tx2 were both accepted.  Don't bother trying to reclaim the
        # P2PKH output; just send tx's first output back to an anyone-can-spend.
        sync_mempools([self.nodes[0], self.nodes[1]])
        tx3.vin = [CTxIn(COutPoint(tx.sha256, 0), b"")]
        tx3.vout = [CTxOut(tx.vout[0].nValue - 1000, CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE]))]
        tx3.wit.vtxinwit.append(CTxInWitness())
        tx3.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
        tx3.rehash()
        if not segwit_activated:
            # Just check mempool acceptance, but don't add the transaction to the mempool, since witness is disallowed
            # in blocks and the tx is impossible to mine right now.
            assert_equal(self.nodes[0].testmempoolaccept([bytes_to_hex_str(tx3.serialize_with_witness())]), [{'txid': tx3.hash, 'allowed': True}])
            # Create the same output as tx3, but by replacing tx
            tx3_out = tx3.vout[0]
            tx3 = tx
            tx3.vout = [tx3_out]
            tx3.rehash()
            assert_equal(self.nodes[0].testmempoolaccept([bytes_to_hex_str(tx3.serialize_with_witness())]), [{'txid': tx3.hash, 'allowed': True}])
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx3, with_witness=True, accepted=True)

        self.nodes[0].generate(1)
        sync_blocks(self.nodes)
        self.utxo.pop(0)
        self.utxo.append(UTXO(tx3.sha256, 0, tx3.vout[0].nValue))
        assert_equal(len(self.nodes[1].getrawmempool()), 0)

    def advance_to_segwit_active(self):
        """Mine enough blocks to activate segwit."""
        # TODO: we could verify that activation only happens at the right threshold
        # of signalling blocks, rather than just at the right period boundary.

        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'locked_in')
        height = self.nodes[0].getblockcount()
        self.nodes[0].generate(VB_PERIOD - (height % VB_PERIOD) - 2)
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'locked_in')
        self.nodes[0].generate(1)
        assert_equal(get_bip9_status(self.nodes[0], 'segwit')['status'], 'active')

    def test_p2sh_witness(self, segwit_activated):
        """Test P2SH wrapped witness programs."""
        self.log.info("Testing P2SH witness transactions")

        assert(len(self.utxo))

        # Prepare the p2sh-wrapped witness output
        witness_program = CScript([OP_DROP, OP_TRUE])
        witness_hash = sha256(witness_program)
        p2wsh_pubkey = CScript([OP_0, witness_hash])
        p2sh_witness_hash = hash160(p2wsh_pubkey)
        script_pubkey = CScript([OP_HASH160, p2sh_witness_hash, OP_EQUAL])
        script_sig = CScript([p2wsh_pubkey])  # a push of the redeem script

        # Fund the P2SH output
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, script_pubkey))
        tx.rehash()

        # Verify mempool acceptance and block validity
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=False, accepted=True)
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True, with_witness=segwit_activated)
        sync_blocks(self.nodes)

        # Now test attempts to spend the output.
        spend_tx = CTransaction()
        spend_tx.vin.append(CTxIn(COutPoint(tx.sha256, 0), script_sig))
        spend_tx.vout.append(CTxOut(tx.vout[0].nValue - 1000, CScript([OP_TRUE])))
        spend_tx.rehash()

        # This transaction should not be accepted into the mempool pre- or
        # post-segwit.  Mempool acceptance will use SCRIPT_VERIFY_WITNESS which
        # will require a witness to spend a witness program regardless of
        # segwit activation.  Note that older bitcoind's that are not
        # segwit-aware would also reject this for failing CLEANSTACK.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, spend_tx, with_witness=False, accepted=False)

        # Try to put the witness script in the script_sig, should also fail.
        spend_tx.vin[0].script_sig = CScript([p2wsh_pubkey, b'a'])
        spend_tx.rehash()
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, spend_tx, with_witness=False, accepted=False)

        # Now put the witness script in the witness, should succeed after
        # segwit activates.
        spend_tx.vin[0].scriptSig = script_sig
        spend_tx.rehash()
        spend_tx.wit.vtxinwit.append(CTxInWitness())
        spend_tx.wit.vtxinwit[0].scriptWitness.stack = [b'a', witness_program]

        # Verify mempool acceptance
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, spend_tx, with_witness=True, accepted=segwit_activated)
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [spend_tx])

        # If we're after activation, then sending this with witnesses should be valid.
        # This no longer works before activation, because SCRIPT_VERIFY_WITNESS
        # is always set.
        # TODO: rewrite this test to make clear that it only works after activation.
        if segwit_activated:
            test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
        else:
            test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True, with_witness=False)

        # Update self.utxo
        self.utxo.pop(0)
        self.utxo.append(UTXO(spend_tx.sha256, 0, spend_tx.vout[0].nValue))

    def test_witness_commitments(self):
        """Test witness commitments.

        This test can only be run after segwit has activated."""

        self.log.info("Testing witness commitments")

        # First try a correct witness commitment.
        block = self.build_next_block()
        add_witness_commitment(block)
        block.solve()

        # Test the test -- witness serialization should be different
        assert(msg_witness_block(block).serialize() != msg_block(block).serialize())

        # This empty block should be valid.
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Try to tweak the nonce
        block_2 = self.build_next_block()
        add_witness_commitment(block_2, nonce=28)
        block_2.solve()

        # The commitment should have changed!
        assert(block_2.vtx[0].vout[-1] != block.vtx[0].vout[-1])

        # This should also be valid.
        test_witness_block(self.nodes[0].rpc, self.test_node, block_2, accepted=True)

        # Now test commitments with actual transactions
        assert (len(self.utxo) > 0)
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))

        # Let's construct a witness program
        witness_program = CScript([OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, script_pubkey))
        tx.rehash()

        # tx2 will spend tx1, and send back to a regular anyone-can-spend address
        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), b""))
        tx2.vout.append(CTxOut(tx.vout[0].nValue - 1000, witness_program))
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
        tx2.rehash()

        block_3 = self.build_next_block()
        self.update_witness_block_with_transactions(block_3, [tx, tx2], nonce=1)
        # Add an extra OP_RETURN output that matches the witness commitment template,
        # even though it has extra data after the incorrect commitment.
        # This block should fail.
        block_3.vtx[0].vout.append(CTxOut(0, CScript([OP_RETURN, WITNESS_COMMITMENT_HEADER + ser_uint256(2), 10])))
        block_3.vtx[0].rehash()
        block_3.hashMerkleRoot = block_3.calc_merkle_root()
        block_3.rehash()
        block_3.solve()

        test_witness_block(self.nodes[0].rpc, self.test_node, block_3, accepted=False)

        # Add a different commitment with different nonce, but in the
        # right location, and with some funds burned(!).
        # This should succeed (nValue shouldn't affect finding the
        # witness commitment).
        add_witness_commitment(block_3, nonce=0)
        block_3.vtx[0].vout[0].nValue -= 1
        block_3.vtx[0].vout[-1].nValue += 1
        block_3.vtx[0].rehash()
        block_3.hashMerkleRoot = block_3.calc_merkle_root()
        block_3.rehash()
        assert(len(block_3.vtx[0].vout) == 4)  # 3 OP_returns
        block_3.solve()
        test_witness_block(self.nodes[0].rpc, self.test_node, block_3, accepted=True)

        # Finally test that a block with no witness transactions can
        # omit the commitment.
        block_4 = self.build_next_block()
        tx3 = CTransaction()
        tx3.vin.append(CTxIn(COutPoint(tx2.sha256, 0), b""))
        tx3.vout.append(CTxOut(tx.vout[0].nValue - 1000, witness_program))
        tx3.rehash()
        block_4.vtx.append(tx3)
        block_4.hashMerkleRoot = block_4.calc_merkle_root()
        block_4.solve()
        test_witness_block(self.nodes[0].rpc, self.test_node, block_4, with_witness=False, accepted=True)

        # Update available utxo's for use in later test.
        self.utxo.pop(0)
        self.utxo.append(UTXO(tx3.sha256, 0, tx3.vout[0].nValue))

    def test_block_malleability(self):
        self.log.info("Testing witness block malleability")

        # Make sure that a block that has too big a virtual size
        # because of a too-large coinbase witness is not permanently
        # marked bad.
        block = self.build_next_block()
        add_witness_commitment(block)
        block.solve()

        block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.append(b'a' * 5000000)
        assert(get_virtual_size(block) > MAX_BLOCK_BASE_SIZE)

        # We can't send over the p2p network, because this is too big to relay
        # TODO: repeat this test with a block that can be relayed
        self.nodes[0].submitblock(bytes_to_hex_str(block.serialize(True)))

        assert(self.nodes[0].getbestblockhash() != block.hash)

        block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.pop()
        assert(get_virtual_size(block) < MAX_BLOCK_BASE_SIZE)
        self.nodes[0].submitblock(bytes_to_hex_str(block.serialize(True)))

        assert(self.nodes[0].getbestblockhash() == block.hash)

        # Now make sure that malleating the witness reserved value doesn't
        # result in a block permanently marked bad.
        block = self.build_next_block()
        add_witness_commitment(block)
        block.solve()

        # Change the nonce -- should not cause the block to be permanently
        # failed
        block.vtx[0].wit.vtxinwit[0].scriptWitness.stack = [ser_uint256(1)]
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Changing the witness reserved value doesn't change the block hash
        block.vtx[0].wit.vtxinwit[0].scriptWitness.stack = [ser_uint256(0)]
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

    def test_witness_block_size(self):
        self.log.info("Testing witness block size limit")
        # TODO: Test that non-witness carrying blocks can't exceed 1MB
        # Skipping this test for now; this is covered in p2p-fullblocktest.py

        # Test that witness-bearing blocks are limited at ceil(base + wit/4) <= 1MB.
        block = self.build_next_block()

        assert(len(self.utxo) > 0)

        # Create a P2WSH transaction.
        # The witness program will be a bunch of OP_2DROP's, followed by OP_TRUE.
        # This should give us plenty of room to tweak the spending tx's
        # virtual size.
        NUM_DROPS = 200  # 201 max ops per script!
        NUM_OUTPUTS = 50

        witness_program = CScript([OP_2DROP] * NUM_DROPS + [OP_TRUE])
        witness_hash = uint256_from_str(sha256(witness_program))
        script_pubkey = CScript([OP_0, ser_uint256(witness_hash)])

        prevout = COutPoint(self.utxo[0].sha256, self.utxo[0].n)
        value = self.utxo[0].nValue

        parent_tx = CTransaction()
        parent_tx.vin.append(CTxIn(prevout, b""))
        child_value = int(value / NUM_OUTPUTS)
        for i in range(NUM_OUTPUTS):
            parent_tx.vout.append(CTxOut(child_value, script_pubkey))
        parent_tx.vout[0].nValue -= 50000
        assert(parent_tx.vout[0].nValue > 0)
        parent_tx.rehash()

        child_tx = CTransaction()
        for i in range(NUM_OUTPUTS):
            child_tx.vin.append(CTxIn(COutPoint(parent_tx.sha256, i), b""))
        child_tx.vout = [CTxOut(value - 100000, CScript([OP_TRUE]))]
        for i in range(NUM_OUTPUTS):
            child_tx.wit.vtxinwit.append(CTxInWitness())
            child_tx.wit.vtxinwit[-1].scriptWitness.stack = [b'a' * 195] * (2 * NUM_DROPS) + [witness_program]
        child_tx.rehash()
        self.update_witness_block_with_transactions(block, [parent_tx, child_tx])

        vsize = get_virtual_size(block)
        additional_bytes = (MAX_BLOCK_BASE_SIZE - vsize) * 4
        i = 0
        while additional_bytes > 0:
            # Add some more bytes to each input until we hit MAX_BLOCK_BASE_SIZE+1
            extra_bytes = min(additional_bytes + 1, 55)
            block.vtx[-1].wit.vtxinwit[int(i / (2 * NUM_DROPS))].scriptWitness.stack[i % (2 * NUM_DROPS)] = b'a' * (195 + extra_bytes)
            additional_bytes -= extra_bytes
            i += 1

        block.vtx[0].vout.pop()  # Remove old commitment
        add_witness_commitment(block)
        block.solve()
        vsize = get_virtual_size(block)
        assert_equal(vsize, MAX_BLOCK_BASE_SIZE + 1)
        # Make sure that our test case would exceed the old max-network-message
        # limit
        assert(len(block.serialize(True)) > 2 * 1024 * 1024)

        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Now resize the second transaction to make the block fit.
        cur_length = len(block.vtx[-1].wit.vtxinwit[0].scriptWitness.stack[0])
        block.vtx[-1].wit.vtxinwit[0].scriptWitness.stack[0] = b'a' * (cur_length - 1)
        block.vtx[0].vout.pop()
        add_witness_commitment(block)
        block.solve()
        assert(get_virtual_size(block) == MAX_BLOCK_BASE_SIZE)

        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Update available utxo's
        self.utxo.pop(0)
        self.utxo.append(UTXO(block.vtx[-1].sha256, 0, block.vtx[-1].vout[0].nValue))

    def test_submit_block(self):
        """Test that submitblock adds the nonce automatically when possible."""
        block = self.build_next_block()

        # Try using a custom nonce and then don't supply it.
        # This shouldn't possibly work.
        add_witness_commitment(block, nonce=1)
        block.vtx[0].wit = CTxWitness()  # drop the nonce
        block.solve()
        self.nodes[0].submitblock(bytes_to_hex_str(block.serialize(True)))
        assert(self.nodes[0].getbestblockhash() != block.hash)

        # Now redo commitment with the standard nonce, but let bitcoind fill it in.
        add_witness_commitment(block, nonce=0)
        block.vtx[0].wit = CTxWitness()
        block.solve()
        self.nodes[0].submitblock(bytes_to_hex_str(block.serialize(True)))
        assert_equal(self.nodes[0].getbestblockhash(), block.hash)

        # This time, add a tx with non-empty witness, but don't supply
        # the commitment.
        block_2 = self.build_next_block()

        add_witness_commitment(block_2)

        block_2.solve()

        # Drop commitment and nonce -- submitblock should not fill in.
        block_2.vtx[0].vout.pop()
        block_2.vtx[0].wit = CTxWitness()

        self.nodes[0].submitblock(bytes_to_hex_str(block_2.serialize(True)))
        # Tip should not advance!
        assert(self.nodes[0].getbestblockhash() != block_2.hash)

    def test_extra_witness_data(self):
        """Test extra witness data in a transaction."""
        self.log.info("Testing extra witness data in tx")

        assert(len(self.utxo) > 0)

        block = self.build_next_block()

        witness_program = CScript([OP_DROP, OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        # First try extra witness data on a tx that doesn't require a witness
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 2000, script_pubkey))
        tx.vout.append(CTxOut(1000, CScript([OP_TRUE])))  # non-witness output
        tx.wit.vtxinwit.append(CTxInWitness())
        tx.wit.vtxinwit[0].scriptWitness.stack = [CScript([])]
        tx.rehash()
        self.update_witness_block_with_transactions(block, [tx])

        # Extra witness data should not be allowed.
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Try extra signature data.  Ok if we're not spending a witness output.
        block.vtx[1].wit.vtxinwit = []
        block.vtx[1].vin[0].scriptSig = CScript([OP_0])
        block.vtx[1].rehash()
        add_witness_commitment(block)
        block.solve()

        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Now try extra witness/signature data on an input that DOES require a
        # witness
        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), b""))  # witness output
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 1), b""))  # non-witness
        tx2.vout.append(CTxOut(tx.vout[0].nValue, CScript([OP_TRUE])))
        tx2.wit.vtxinwit.extend([CTxInWitness(), CTxInWitness()])
        tx2.wit.vtxinwit[0].scriptWitness.stack = [CScript([CScriptNum(1)]), CScript([CScriptNum(1)]), witness_program]
        tx2.wit.vtxinwit[1].scriptWitness.stack = [CScript([OP_TRUE])]

        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx2])

        # This has extra witness data, so it should fail.
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Now get rid of the extra witness, but add extra scriptSig data
        tx2.vin[0].scriptSig = CScript([OP_TRUE])
        tx2.vin[1].scriptSig = CScript([OP_TRUE])
        tx2.wit.vtxinwit[0].scriptWitness.stack.pop(0)
        tx2.wit.vtxinwit[1].scriptWitness.stack = []
        tx2.rehash()
        add_witness_commitment(block)
        block.solve()

        # This has extra signature data for a witness input, so it should fail.
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Now get rid of the extra scriptsig on the witness input, and verify
        # success (even with extra scriptsig data in the non-witness input)
        tx2.vin[0].scriptSig = b""
        tx2.rehash()
        add_witness_commitment(block)
        block.solve()

        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Update utxo for later tests
        self.utxo.pop(0)
        self.utxo.append(UTXO(tx2.sha256, 0, tx2.vout[0].nValue))

    def test_max_witness_push_length(self):
        """Test that witness stack can only allow up to 520 byte pushes."""
        self.log.info("Testing maximum witness push size")
        MAX_SCRIPT_ELEMENT_SIZE = 520
        assert(len(self.utxo))

        block = self.build_next_block()

        witness_program = CScript([OP_DROP, OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, script_pubkey))
        tx.rehash()

        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), b""))
        tx2.vout.append(CTxOut(tx.vout[0].nValue - 1000, CScript([OP_TRUE])))
        tx2.wit.vtxinwit.append(CTxInWitness())
        # First try a 521-byte stack element
        tx2.wit.vtxinwit[0].scriptWitness.stack = [b'a' * (MAX_SCRIPT_ELEMENT_SIZE + 1), witness_program]
        tx2.rehash()

        self.update_witness_block_with_transactions(block, [tx, tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Now reduce the length of the stack element
        tx2.wit.vtxinwit[0].scriptWitness.stack[0] = b'a' * (MAX_SCRIPT_ELEMENT_SIZE)

        add_witness_commitment(block)
        block.solve()
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Update the utxo for later tests
        self.utxo.pop()
        self.utxo.append(UTXO(tx2.sha256, 0, tx2.vout[0].nValue))

    def test_max_witness_program_length(self):
        """Test that witness outputs greater than 10kB can't be spent."""
        self.log.info("Testing maximum witness program length")
        assert(len(self.utxo))
        MAX_PROGRAM_LENGTH = 10000

        # This program is 19 max pushes (9937 bytes), then 64 more opcode-bytes.
        long_witness_program = CScript([b'a' * 520] * 19 + [OP_DROP] * 63 + [OP_TRUE])
        assert(len(long_witness_program) == MAX_PROGRAM_LENGTH + 1)
        long_witness_hash = sha256(long_witness_program)
        long_script_pubkey = CScript([OP_0, long_witness_hash])

        block = self.build_next_block()

        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, long_script_pubkey))
        tx.rehash()

        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), b""))
        tx2.vout.append(CTxOut(tx.vout[0].nValue - 1000, CScript([OP_TRUE])))
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [b'a'] * 44 + [long_witness_program]
        tx2.rehash()

        self.update_witness_block_with_transactions(block, [tx, tx2])

        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Try again with one less byte in the witness program
        witness_program = CScript([b'a' * 520] * 19 + [OP_DROP] * 62 + [OP_TRUE])
        assert(len(witness_program) == MAX_PROGRAM_LENGTH)
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        tx.vout[0] = CTxOut(tx.vout[0].nValue, script_pubkey)
        tx.rehash()
        tx2.vin[0].prevout.hash = tx.sha256
        tx2.wit.vtxinwit[0].scriptWitness.stack = [b'a'] * 43 + [witness_program]
        tx2.rehash()
        block.vtx = [block.vtx[0]]
        self.update_witness_block_with_transactions(block, [tx, tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        self.utxo.pop()
        self.utxo.append(UTXO(tx2.sha256, 0, tx2.vout[0].nValue))

    def test_witness_input_length(self):
        """Test that vin length must match vtxinwit length."""
        self.log.info("Testing witness input length")
        assert(len(self.utxo))

        witness_program = CScript([OP_DROP, OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        # Create a transaction that splits our utxo into many outputs
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        value = self.utxo[0].nValue
        for i in range(10):
            tx.vout.append(CTxOut(int(value / 10), script_pubkey))
        tx.vout[0].nValue -= 1000
        assert(tx.vout[0].nValue >= 0)

        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Try various ways to spend tx that should all break.
        # This "broken" transaction serializer will not normalize
        # the length of vtxinwit.
        class BrokenCTransaction(CTransaction):
            def serialize_with_witness(self):
                flags = 0
                if not self.wit.is_null():
                    flags |= 1
                r = b""
                r += struct.pack("<i", self.nVersion)
                if flags:
                    dummy = []
                    r += ser_vector(dummy)
                    r += struct.pack("<B", flags)
                r += ser_vector(self.vin)
                r += ser_vector(self.vout)
                if flags & 1:
                    r += self.wit.serialize()
                r += struct.pack("<I", self.nLockTime)
                return r

        tx2 = BrokenCTransaction()
        for i in range(10):
            tx2.vin.append(CTxIn(COutPoint(tx.sha256, i), b""))
        tx2.vout.append(CTxOut(value - 3000, CScript([OP_TRUE])))

        # First try using a too long vtxinwit
        for i in range(11):
            tx2.wit.vtxinwit.append(CTxInWitness())
            tx2.wit.vtxinwit[i].scriptWitness.stack = [b'a', witness_program]

        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Now try using a too short vtxinwit
        tx2.wit.vtxinwit.pop()
        tx2.wit.vtxinwit.pop()

        block.vtx = [block.vtx[0]]
        self.update_witness_block_with_transactions(block, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Now make one of the intermediate witnesses be incorrect
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[-1].scriptWitness.stack = [b'a', witness_program]
        tx2.wit.vtxinwit[5].scriptWitness.stack = [witness_program]

        block.vtx = [block.vtx[0]]
        self.update_witness_block_with_transactions(block, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Fix the broken witness and the block should be accepted.
        tx2.wit.vtxinwit[5].scriptWitness.stack = [b'a', witness_program]
        block.vtx = [block.vtx[0]]
        self.update_witness_block_with_transactions(block, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        self.utxo.pop()
        self.utxo.append(UTXO(tx2.sha256, 0, tx2.vout[0].nValue))

    def test_tx_relay_after_segwit_activation(self):
        """Test transaction relay after segwit activation.

        After segwit activates, verify that mempool:
        - rejects transactions with unnecessary/extra witnesses
        - accepts transactions with valid witnesses
        and that witness transactions are relayed to non-upgraded peers."""

        self.log.info("Testing relay of witness transactions")
        # Generate a transaction that doesn't require a witness, but send it
        # with a witness.  Should be rejected because we can't use a witness
        # when spending a non-witness output.
        assert(len(self.utxo))
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))
        tx.wit.vtxinwit.append(CTxInWitness())
        tx.wit.vtxinwit[0].scriptWitness.stack = [b'a']
        tx.rehash()

        tx_hash = tx.sha256

        # Verify that unnecessary witnesses are rejected.
        self.test_node.announce_tx_and_wait_for_getdata(tx)
        assert_equal(len(self.nodes[0].getrawmempool()), 0)
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=True, accepted=False)

        # Verify that removing the witness succeeds.
        self.test_node.announce_tx_and_wait_for_getdata(tx)
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=False, accepted=True)

        # Now try to add extra witness data to a valid witness tx.
        witness_program = CScript([OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])
        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx_hash, 0), b""))
        tx2.vout.append(CTxOut(tx.vout[0].nValue - 1000, script_pubkey))
        tx2.rehash()

        tx3 = CTransaction()
        tx3.vin.append(CTxIn(COutPoint(tx2.sha256, 0), b""))
        tx3.wit.vtxinwit.append(CTxInWitness())

        # Add too-large for IsStandard witness and check that it does not enter reject filter
        p2sh_program = CScript([OP_TRUE])
        p2sh_pubkey = hash160(p2sh_program)
        witness_program2 = CScript([b'a' * 400000])
        tx3.vout.append(CTxOut(tx2.vout[0].nValue - 1000, CScript([OP_HASH160, p2sh_pubkey, OP_EQUAL])))
        tx3.wit.vtxinwit[0].scriptWitness.stack = [witness_program2]
        tx3.rehash()

        # Node will not be blinded to the transaction
        self.std_node.announce_tx_and_wait_for_getdata(tx3)
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx3, True, False, b'tx-size')
        self.std_node.announce_tx_and_wait_for_getdata(tx3)
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx3, True, False, b'tx-size')

        # Remove witness stuffing, instead add extra witness push on stack
        tx3.vout[0] = CTxOut(tx2.vout[0].nValue - 1000, CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE]))
        tx3.wit.vtxinwit[0].scriptWitness.stack = [CScript([CScriptNum(1)]), witness_program]
        tx3.rehash()

        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx2, with_witness=True, accepted=True)
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx3, with_witness=True, accepted=False)

        # Get rid of the extra witness, and verify acceptance.
        tx3.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
        # Also check that old_node gets a tx announcement, even though this is
        # a witness transaction.
        self.old_node.wait_for_inv([CInv(1, tx2.sha256)])  # wait until tx2 was inv'ed
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx3, with_witness=True, accepted=True)
        self.old_node.wait_for_inv([CInv(1, tx3.sha256)])

        # Test that getrawtransaction returns correct witness information
        # hash, size, vsize
        raw_tx = self.nodes[0].getrawtransaction(tx3.hash, 1)
        assert_equal(int(raw_tx["hash"], 16), tx3.calc_sha256(True))
        assert_equal(raw_tx["size"], len(tx3.serialize_with_witness()))
        weight = len(tx3.serialize_with_witness()) + 3 * len(tx3.serialize_without_witness())
        vsize = math.ceil(weight / 4)
        assert_equal(raw_tx["vsize"], vsize)
        assert_equal(raw_tx["weight"], weight)
        assert_equal(len(raw_tx["vin"][0]["txinwitness"]), 1)
        assert_equal(raw_tx["vin"][0]["txinwitness"][0], hexlify(witness_program).decode('ascii'))
        assert(vsize != raw_tx["size"])

        # Cleanup: mine the transactions and update utxo for next test
        self.nodes[0].generate(1)
        assert_equal(len(self.nodes[0].getrawmempool()), 0)

        self.utxo.pop(0)
        self.utxo.append(UTXO(tx3.sha256, 0, tx3.vout[0].nValue))

    def test_segwit_versions(self):
        """Test validity of future segwit version transactions.

        Future segwit version transactions are non-standard, but valid in blocks.
        Can run this before and after segwit activation."""

        self.log.info("Testing standardness/consensus for segwit versions (0-16)")
        assert(len(self.utxo))
        num_tests = 17  # will test OP_0, OP1, ..., OP_16
        if (len(self.utxo) < num_tests):
            tx = CTransaction()
            tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
            split_value = (self.utxo[0].nValue - 4000) // num_tests
            for i in range(num_tests):
                tx.vout.append(CTxOut(split_value, CScript([OP_TRUE])))
            tx.rehash()
            block = self.build_next_block()
            self.update_witness_block_with_transactions(block, [tx])
            test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
            self.utxo.pop(0)
            for i in range(num_tests):
                self.utxo.append(UTXO(tx.sha256, i, split_value))

        sync_blocks(self.nodes)
        temp_utxo = []
        tx = CTransaction()
        count = 0
        witness_program = CScript([OP_TRUE])
        witness_hash = sha256(witness_program)
        assert_equal(len(self.nodes[1].getrawmempool()), 0)
        for version in list(range(OP_1, OP_16 + 1)) + [OP_0]:
            count += 1
            # First try to spend to a future version segwit script_pubkey.
            script_pubkey = CScript([CScriptOp(version), witness_hash])
            tx.vin = [CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b"")]
            tx.vout = [CTxOut(self.utxo[0].nValue - 1000, script_pubkey)]
            tx.rehash()
            test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx, with_witness=True, accepted=False)
            test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=True, accepted=True)
            self.utxo.pop(0)
            temp_utxo.append(UTXO(tx.sha256, 0, tx.vout[0].nValue))

        self.nodes[0].generate(1)  # Mine all the transactions
        sync_blocks(self.nodes)
        assert(len(self.nodes[0].getrawmempool()) == 0)

        # Finally, verify that version 0 -> version 1 transactions
        # are non-standard
        script_pubkey = CScript([CScriptOp(OP_1), witness_hash])
        tx2 = CTransaction()
        tx2.vin = [CTxIn(COutPoint(tx.sha256, 0), b"")]
        tx2.vout = [CTxOut(tx.vout[0].nValue - 1000, script_pubkey)]
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
        tx2.rehash()
        # Gets accepted to test_node, because standardness of outputs isn't
        # checked with fRequireStandard
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx2, with_witness=True, accepted=True)
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx2, with_witness=True, accepted=False)
        temp_utxo.pop()  # last entry in temp_utxo was the output we just spent
        temp_utxo.append(UTXO(tx2.sha256, 0, tx2.vout[0].nValue))

        # Spend everything in temp_utxo back to an OP_TRUE output.
        tx3 = CTransaction()
        total_value = 0
        for i in temp_utxo:
            tx3.vin.append(CTxIn(COutPoint(i.sha256, i.n), b""))
            tx3.wit.vtxinwit.append(CTxInWitness())
            total_value += i.nValue
        tx3.wit.vtxinwit[-1].scriptWitness.stack = [witness_program]
        tx3.vout.append(CTxOut(total_value - 1000, CScript([OP_TRUE])))
        tx3.rehash()
        # Spending a higher version witness output is not allowed by policy,
        # even with fRequireStandard=false.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx3, with_witness=True, accepted=False)
        self.test_node.sync_with_ping()
        with mininode_lock:
            assert(b"reserved for soft-fork upgrades" in self.test_node.last_message["reject"].reason)

        # Building a block with the transaction must be valid, however.
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx2, tx3])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
        sync_blocks(self.nodes)

        # Add utxo to our list
        self.utxo.append(UTXO(tx3.sha256, 0, tx3.vout[0].nValue))

    def test_premature_coinbase_witness_spend(self):
        self.log.info("Testing premature coinbase witness spend")
        block = self.build_next_block()
        # Change the output of the block to be a witness output.
        witness_program = CScript([OP_TRUE])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])
        block.vtx[0].vout[0].scriptPubKey = script_pubkey
        # This next line will rehash the coinbase and update the merkle
        # root, and solve.
        self.update_witness_block_with_transactions(block, [])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        spend_tx = CTransaction()
        spend_tx.vin = [CTxIn(COutPoint(block.vtx[0].sha256, 0), b"")]
        spend_tx.vout = [CTxOut(block.vtx[0].vout[0].nValue, witness_program)]
        spend_tx.wit.vtxinwit.append(CTxInWitness())
        spend_tx.wit.vtxinwit[0].scriptWitness.stack = [witness_program]
        spend_tx.rehash()

        # Now test a premature spend.
        self.nodes[0].generate(98)
        sync_blocks(self.nodes)
        block2 = self.build_next_block()
        self.update_witness_block_with_transactions(block2, [spend_tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block2, accepted=False)

        # Advancing one more block should allow the spend.
        self.nodes[0].generate(1)
        block2 = self.build_next_block()
        self.update_witness_block_with_transactions(block2, [spend_tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block2, accepted=True)
        sync_blocks(self.nodes)

    def test_uncompressed_pubkey(self):
        """Test uncompressed pubkey validity in segwit transactions.

        Uncompressed pubkeys are no longer supported in default relay policy,
        but (for now) are still valid in blocks."""

        self.log.info("Testing uncompressed pubkeys")
        # Segwit transactions using uncompressed pubkeys are not accepted
        # under default policy, but should still pass consensus.
        key = CECKey()
        key.set_secretbytes(b"9")
        key.set_compressed(False)
        pubkey = CPubKey(key.get_pubkey())
        assert_equal(len(pubkey), 65)  # This should be an uncompressed pubkey

        assert(len(self.utxo) > 0)
        utxo = self.utxo.pop(0)

        # Test 1: P2WPKH
        # First create a P2WPKH output that uses an uncompressed pubkey
        pubkeyhash = hash160(pubkey)
        script_pkh = CScript([OP_0, pubkeyhash])
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(utxo.sha256, utxo.n), b""))
        tx.vout.append(CTxOut(utxo.nValue - 1000, script_pkh))
        tx.rehash()

        # Confirm it in a block.
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Now try to spend it. Send it to a P2WSH output, which we'll
        # use in the next test.
        witness_program = CScript([pubkey, CScriptOp(OP_CHECKSIG)])
        witness_hash = sha256(witness_program)
        script_wsh = CScript([OP_0, witness_hash])

        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), b""))
        tx2.vout.append(CTxOut(tx.vout[0].nValue - 1000, script_wsh))
        script = get_p2pkh_script(pubkeyhash)
        sig_hash = SegwitVersion1SignatureHash(script, tx2, 0, SIGHASH_ALL, tx.vout[0].nValue)
        signature = key.sign(sig_hash) + b'\x01'  # 0x1 is SIGHASH_ALL
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [signature, pubkey]
        tx2.rehash()

        # Should fail policy test.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx2, True, False, b'non-mandatory-script-verify-flag (Using non-compressed keys in segwit)')
        # But passes consensus.
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Test 2: P2WSH
        # Try to spend the P2WSH output created in last test.
        # Send it to a P2SH(P2WSH) output, which we'll use in the next test.
        p2sh_witness_hash = hash160(script_wsh)
        script_p2sh = CScript([OP_HASH160, p2sh_witness_hash, OP_EQUAL])
        script_sig = CScript([script_wsh])

        tx3 = CTransaction()
        tx3.vin.append(CTxIn(COutPoint(tx2.sha256, 0), b""))
        tx3.vout.append(CTxOut(tx2.vout[0].nValue - 1000, script_p2sh))
        tx3.wit.vtxinwit.append(CTxInWitness())
        sign_p2pk_witness_input(witness_program, tx3, 0, SIGHASH_ALL, tx2.vout[0].nValue, key)

        # Should fail policy test.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx3, True, False, b'non-mandatory-script-verify-flag (Using non-compressed keys in segwit)')
        # But passes consensus.
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx3])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Test 3: P2SH(P2WSH)
        # Try to spend the P2SH output created in the last test.
        # Send it to a P2PKH output, which we'll use in the next test.
        script_pubkey = get_p2pkh_script(pubkeyhash)
        tx4 = CTransaction()
        tx4.vin.append(CTxIn(COutPoint(tx3.sha256, 0), script_sig))
        tx4.vout.append(CTxOut(tx3.vout[0].nValue - 1000, script_pubkey))
        tx4.wit.vtxinwit.append(CTxInWitness())
        sign_p2pk_witness_input(witness_program, tx4, 0, SIGHASH_ALL, tx3.vout[0].nValue, key)

        # Should fail policy test.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx4, True, False, b'non-mandatory-script-verify-flag (Using non-compressed keys in segwit)')
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx4])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Test 4: Uncompressed pubkeys should still be valid in non-segwit
        # transactions.
        tx5 = CTransaction()
        tx5.vin.append(CTxIn(COutPoint(tx4.sha256, 0), b""))
        tx5.vout.append(CTxOut(tx4.vout[0].nValue - 1000, CScript([OP_TRUE])))
        (sig_hash, err) = SignatureHash(script_pubkey, tx5, 0, SIGHASH_ALL)
        signature = key.sign(sig_hash) + b'\x01'  # 0x1 is SIGHASH_ALL
        tx5.vin[0].scriptSig = CScript([signature, pubkey])
        tx5.rehash()
        # Should pass policy and consensus.
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx5, True, True)
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx5])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
        self.utxo.append(UTXO(tx5.sha256, 0, tx5.vout[0].nValue))

    def test_signature_version_1(self):
        self.log.info("Testing segwit signature hash version 1")
        key = CECKey()
        key.set_secretbytes(b"9")
        pubkey = CPubKey(key.get_pubkey())

        witness_program = CScript([pubkey, CScriptOp(OP_CHECKSIG)])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        # First create a witness output for use in the tests.
        assert(len(self.utxo))
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, script_pubkey))
        tx.rehash()

        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=True, accepted=True)
        # Mine this transaction in preparation for following tests.
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
        sync_blocks(self.nodes)
        self.utxo.pop(0)

        # Test each hashtype
        prev_utxo = UTXO(tx.sha256, 0, tx.vout[0].nValue)
        for sigflag in [0, SIGHASH_ANYONECANPAY]:
            for hashtype in [SIGHASH_ALL, SIGHASH_NONE, SIGHASH_SINGLE]:
                hashtype |= sigflag
                block = self.build_next_block()
                tx = CTransaction()
                tx.vin.append(CTxIn(COutPoint(prev_utxo.sha256, prev_utxo.n), b""))
                tx.vout.append(CTxOut(prev_utxo.nValue - 1000, script_pubkey))
                tx.wit.vtxinwit.append(CTxInWitness())
                # Too-large input value
                sign_p2pk_witness_input(witness_program, tx, 0, hashtype, prev_utxo.nValue + 1, key)
                self.update_witness_block_with_transactions(block, [tx])
                test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

                # Too-small input value
                sign_p2pk_witness_input(witness_program, tx, 0, hashtype, prev_utxo.nValue - 1, key)
                block.vtx.pop()  # remove last tx
                self.update_witness_block_with_transactions(block, [tx])
                test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

                # Now try correct value
                sign_p2pk_witness_input(witness_program, tx, 0, hashtype, prev_utxo.nValue, key)
                block.vtx.pop()
                self.update_witness_block_with_transactions(block, [tx])
                test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

                prev_utxo = UTXO(tx.sha256, 0, tx.vout[0].nValue)

        # Test combinations of signature hashes.
        # Split the utxo into a lot of outputs.
        # Randomly choose up to 10 to spend, sign with different hashtypes, and
        # output to a random number of outputs.  Repeat num_tests times.
        # Ensure that we've tested a situation where we use SIGHASH_SINGLE with
        # an input index > number of outputs.
        num_tests = 500
        temp_utxos = []
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(prev_utxo.sha256, prev_utxo.n), b""))
        split_value = prev_utxo.nValue // num_tests
        for i in range(num_tests):
            tx.vout.append(CTxOut(split_value, script_pubkey))
        tx.wit.vtxinwit.append(CTxInWitness())
        sign_p2pk_witness_input(witness_program, tx, 0, SIGHASH_ALL, prev_utxo.nValue, key)
        for i in range(num_tests):
            temp_utxos.append(UTXO(tx.sha256, i, split_value))

        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        block = self.build_next_block()
        used_sighash_single_out_of_bounds = False
        for i in range(num_tests):
            # Ping regularly to keep the connection alive
            if (not i % 100):
                self.test_node.sync_with_ping()
            # Choose random number of inputs to use.
            num_inputs = random.randint(1, 10)
            # Create a slight bias for producing more utxos
            num_outputs = random.randint(1, 11)
            random.shuffle(temp_utxos)
            assert(len(temp_utxos) > num_inputs)
            tx = CTransaction()
            total_value = 0
            for i in range(num_inputs):
                tx.vin.append(CTxIn(COutPoint(temp_utxos[i].sha256, temp_utxos[i].n), b""))
                tx.wit.vtxinwit.append(CTxInWitness())
                total_value += temp_utxos[i].nValue
            split_value = total_value // num_outputs
            for i in range(num_outputs):
                tx.vout.append(CTxOut(split_value, script_pubkey))
            for i in range(num_inputs):
                # Now try to sign each input, using a random hashtype.
                anyonecanpay = 0
                if random.randint(0, 1):
                    anyonecanpay = SIGHASH_ANYONECANPAY
                hashtype = random.randint(1, 3) | anyonecanpay
                sign_p2pk_witness_input(witness_program, tx, i, hashtype, temp_utxos[i].nValue, key)
                if (hashtype == SIGHASH_SINGLE and i >= num_outputs):
                    used_sighash_single_out_of_bounds = True
            tx.rehash()
            for i in range(num_outputs):
                temp_utxos.append(UTXO(tx.sha256, i, split_value))
            temp_utxos = temp_utxos[num_inputs:]

            block.vtx.append(tx)

            # Test the block periodically, if we're close to maxblocksize
            if (get_virtual_size(block) > MAX_BLOCK_BASE_SIZE - 1000):
                self.update_witness_block_with_transactions(block, [])
                test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)
                block = self.build_next_block()

        if (not used_sighash_single_out_of_bounds):
            self.log.info("WARNING: this test run didn't attempt SIGHASH_SINGLE with out-of-bounds index value")
        # Test the transactions we've added to the block
        if (len(block.vtx) > 1):
            self.update_witness_block_with_transactions(block, [])
            test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        # Now test witness version 0 P2PKH transactions
        pubkeyhash = hash160(pubkey)
        script_pkh = CScript([OP_0, pubkeyhash])
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(temp_utxos[0].sha256, temp_utxos[0].n), b""))
        tx.vout.append(CTxOut(temp_utxos[0].nValue, script_pkh))
        tx.wit.vtxinwit.append(CTxInWitness())
        sign_p2pk_witness_input(witness_program, tx, 0, SIGHASH_ALL, temp_utxos[0].nValue, key)
        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), b""))
        tx2.vout.append(CTxOut(tx.vout[0].nValue, CScript([OP_TRUE])))

        script = get_p2pkh_script(pubkeyhash)
        sig_hash = SegwitVersion1SignatureHash(script, tx2, 0, SIGHASH_ALL, tx.vout[0].nValue)
        signature = key.sign(sig_hash) + b'\x01'  # 0x1 is SIGHASH_ALL

        # Check that we can't have a scriptSig
        tx2.vin[0].scriptSig = CScript([signature, pubkey])
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx, tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=False)

        # Move the signature to the witness.
        block.vtx.pop()
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [signature, pubkey]
        tx2.vin[0].scriptSig = b""
        tx2.rehash()

        self.update_witness_block_with_transactions(block, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        temp_utxos.pop(0)

        # Update self.utxos for later tests by creating two outputs
        # that consolidate all the coins in temp_utxos.
        output_value = sum(i.nValue for i in temp_utxos) // 2

        tx = CTransaction()
        index = 0
        # Just spend to our usual anyone-can-spend output
        tx.vout = [CTxOut(output_value, CScript([OP_TRUE]))] * 2
        for i in temp_utxos:
            # Use SIGHASH_ALL|SIGHASH_ANYONECANPAY so we can build up
            # the signatures as we go.
            tx.vin.append(CTxIn(COutPoint(i.sha256, i.n), b""))
            tx.wit.vtxinwit.append(CTxInWitness())
            sign_p2pk_witness_input(witness_program, tx, index, SIGHASH_ALL | SIGHASH_ANYONECANPAY, i.nValue, key)
            index += 1
        block = self.build_next_block()
        self.update_witness_block_with_transactions(block, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block, accepted=True)

        for i in range(len(tx.vout)):
            self.utxo.append(UTXO(tx.sha256, i, tx.vout[i].nValue))

    def test_non_standard_witness_blinding(self):
        self.log.info("Testing behavior of unnecessary witnesses in transactions does not blind the node for the transaction")
        assert (len(self.utxo) > 0)

        # Create a p2sh output -- this is so we can pass the standardness
        # rules (an anyone-can-spend OP_TRUE would be rejected, if not wrapped
        # in P2SH).
        p2sh_program = CScript([OP_TRUE])
        p2sh_pubkey = hash160(p2sh_program)
        script_pubkey = CScript([OP_HASH160, p2sh_pubkey, OP_EQUAL])

        # Now check that unnecessary witnesses can't be used to blind a node
        # to a transaction, eg by violating standardness checks.
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        tx.vout.append(CTxOut(self.utxo[0].nValue - 1000, script_pubkey))
        tx.rehash()
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, False, True)
        self.nodes[0].generate(1)
        sync_blocks(self.nodes)

        # We'll add an unnecessary witness to this transaction that would cause
        # it to be non-standard, to test that violating policy with a witness
        # doesn't blind a node to a transaction.  Transactions
        # rejected for having a witness shouldn't be added
        # to the rejection cache.
        tx2 = CTransaction()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, 0), CScript([p2sh_program])))
        tx2.vout.append(CTxOut(tx.vout[0].nValue - 1000, script_pubkey))
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[0].scriptWitness.stack = [b'a' * 400]
        tx2.rehash()
        # This will be rejected due to a policy check:
        # No witness is allowed, since it is not a witness program but a p2sh program
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx2, True, False, b'bad-witness-nonstandard')

        # If we send without witness, it should be accepted.
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, tx2, False, True)

        # Now create a new anyone-can-spend utxo for the next test.
        tx3 = CTransaction()
        tx3.vin.append(CTxIn(COutPoint(tx2.sha256, 0), CScript([p2sh_program])))
        tx3.vout.append(CTxOut(tx2.vout[0].nValue - 1000, CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))
        tx3.rehash()
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx2, False, True)
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx3, False, True)

        self.nodes[0].generate(1)
        sync_blocks(self.nodes)

        # Update our utxo list; we spent the first entry.
        self.utxo.pop(0)
        self.utxo.append(UTXO(tx3.sha256, 0, tx3.vout[0].nValue))

    def test_non_standard_witness(self):
        self.log.info("Testing detection of non-standard P2WSH witness")
        pad = chr(1).encode('latin-1')

        # Create scripts for tests
        scripts = []
        scripts.append(CScript([OP_DROP] * 100))
        scripts.append(CScript([OP_DROP] * 99))
        scripts.append(CScript([pad * 59] * 59 + [OP_DROP] * 60))
        scripts.append(CScript([pad * 59] * 59 + [OP_DROP] * 61))

        p2wsh_scripts = []

        assert(len(self.utxo))
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))

        # For each script, generate a pair of P2WSH and P2SH-P2WSH output.
        outputvalue = (self.utxo[0].nValue - 1000) // (len(scripts) * 2)
        for i in scripts:
            p2wsh = CScript([OP_0, sha256(i)])
            p2sh = hash160(p2wsh)
            p2wsh_scripts.append(p2wsh)
            tx.vout.append(CTxOut(outputvalue, p2wsh))
            tx.vout.append(CTxOut(outputvalue, CScript([OP_HASH160, p2sh, OP_EQUAL])))
        tx.rehash()
        txid = tx.sha256
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, tx, with_witness=False, accepted=True)

        self.nodes[0].generate(1)
        sync_blocks(self.nodes)

        # Creating transactions for tests
        p2wsh_txs = []
        p2sh_txs = []
        for i in range(len(scripts)):
            p2wsh_tx = CTransaction()
            p2wsh_tx.vin.append(CTxIn(COutPoint(txid, i * 2)))
            p2wsh_tx.vout.append(CTxOut(outputvalue - 5000, CScript([OP_0, hash160(hex_str_to_bytes(""))])))
            p2wsh_tx.wit.vtxinwit.append(CTxInWitness())
            p2wsh_tx.rehash()
            p2wsh_txs.append(p2wsh_tx)
            p2sh_tx = CTransaction()
            p2sh_tx.vin.append(CTxIn(COutPoint(txid, i * 2 + 1), CScript([p2wsh_scripts[i]])))
            p2sh_tx.vout.append(CTxOut(outputvalue - 5000, CScript([OP_0, hash160(hex_str_to_bytes(""))])))
            p2sh_tx.wit.vtxinwit.append(CTxInWitness())
            p2sh_tx.rehash()
            p2sh_txs.append(p2sh_tx)

        # Testing native P2WSH
        # Witness stack size, excluding witnessScript, over 100 is non-standard
        p2wsh_txs[0].wit.vtxinwit[0].scriptWitness.stack = [pad] * 101 + [scripts[0]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2wsh_txs[0], True, False, b'bad-witness-nonstandard')
        # Non-standard nodes should accept
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2wsh_txs[0], True, True)

        # Stack element size over 80 bytes is non-standard
        p2wsh_txs[1].wit.vtxinwit[0].scriptWitness.stack = [pad * 81] * 100 + [scripts[1]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2wsh_txs[1], True, False, b'bad-witness-nonstandard')
        # Non-standard nodes should accept
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2wsh_txs[1], True, True)
        # Standard nodes should accept if element size is not over 80 bytes
        p2wsh_txs[1].wit.vtxinwit[0].scriptWitness.stack = [pad * 80] * 100 + [scripts[1]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2wsh_txs[1], True, True)

        # witnessScript size at 3600 bytes is standard
        p2wsh_txs[2].wit.vtxinwit[0].scriptWitness.stack = [pad, pad, scripts[2]]
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2wsh_txs[2], True, True)
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2wsh_txs[2], True, True)

        # witnessScript size at 3601 bytes is non-standard
        p2wsh_txs[3].wit.vtxinwit[0].scriptWitness.stack = [pad, pad, pad, scripts[3]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2wsh_txs[3], True, False, b'bad-witness-nonstandard')
        # Non-standard nodes should accept
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2wsh_txs[3], True, True)

        # Repeating the same tests with P2SH-P2WSH
        p2sh_txs[0].wit.vtxinwit[0].scriptWitness.stack = [pad] * 101 + [scripts[0]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2sh_txs[0], True, False, b'bad-witness-nonstandard')
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2sh_txs[0], True, True)
        p2sh_txs[1].wit.vtxinwit[0].scriptWitness.stack = [pad * 81] * 100 + [scripts[1]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2sh_txs[1], True, False, b'bad-witness-nonstandard')
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2sh_txs[1], True, True)
        p2sh_txs[1].wit.vtxinwit[0].scriptWitness.stack = [pad * 80] * 100 + [scripts[1]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2sh_txs[1], True, True)
        p2sh_txs[2].wit.vtxinwit[0].scriptWitness.stack = [pad, pad, scripts[2]]
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2sh_txs[2], True, True)
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2sh_txs[2], True, True)
        p2sh_txs[3].wit.vtxinwit[0].scriptWitness.stack = [pad, pad, pad, scripts[3]]
        test_transaction_acceptance(self.nodes[1].rpc, self.std_node, p2sh_txs[3], True, False, b'bad-witness-nonstandard')
        test_transaction_acceptance(self.nodes[0].rpc, self.test_node, p2sh_txs[3], True, True)

        self.nodes[0].generate(1)  # Mine and clean up the mempool of non-standard node
        # Valid but non-standard transactions in a block should be accepted by standard node
        sync_blocks(self.nodes)
        assert_equal(len(self.nodes[0].getrawmempool()), 0)
        assert_equal(len(self.nodes[1].getrawmempool()), 0)

        self.utxo.pop(0)

    def test_upgrade_after_activation(self, node_id):
        """Test the behavior of starting up a segwit-aware node after the softfork has activated."""
        self.log.info("Testing software upgrade after softfork activation")

        assert(node_id != 0)  # node0 is assumed to be a segwit-active bitcoind

        # Make sure the nodes are all up
        sync_blocks(self.nodes)

        # Restart with the new binary
        self.stop_node(node_id)
        self.start_node(node_id, extra_args=["-vbparams=segwit:0:999999999999"])
        connect_nodes(self.nodes[0], node_id)

        sync_blocks(self.nodes)

        # Make sure that this peer thinks segwit has activated.
        assert(get_bip9_status(self.nodes[node_id], 'segwit')['status'] == "active")

        # Make sure this peer's blocks match those of node0.
        height = self.nodes[node_id].getblockcount()
        while height >= 0:
            block_hash = self.nodes[node_id].getblockhash(height)
            assert_equal(block_hash, self.nodes[0].getblockhash(height))
            assert_equal(self.nodes[0].getblock(block_hash), self.nodes[node_id].getblock(block_hash))
            height -= 1

    def test_witness_sigops(self):
        """Test sigop counting is correct inside witnesses."""
        self.log.info("Testing sigops limit")

        assert(len(self.utxo))

        # Keep this under MAX_OPS_PER_SCRIPT (201)
        witness_program = CScript([OP_TRUE, OP_IF, OP_TRUE, OP_ELSE] + [OP_CHECKMULTISIG] * 5 + [OP_CHECKSIG] * 193 + [OP_ENDIF])
        witness_hash = sha256(witness_program)
        script_pubkey = CScript([OP_0, witness_hash])

        sigops_per_script = 20 * 5 + 193 * 1
        # We'll produce 2 extra outputs, one with a program that would take us
        # over max sig ops, and one with a program that would exactly reach max
        # sig ops
        outputs = (MAX_SIGOP_COST // sigops_per_script) + 2
        extra_sigops_available = MAX_SIGOP_COST % sigops_per_script

        # We chose the number of checkmultisigs/checksigs to make this work:
        assert(extra_sigops_available < 100)  # steer clear of MAX_OPS_PER_SCRIPT

        # This script, when spent with the first
        # N(=MAX_SIGOP_COST//sigops_per_script) outputs of our transaction,
        # would push us just over the block sigop limit.
        witness_program_toomany = CScript([OP_TRUE, OP_IF, OP_TRUE, OP_ELSE] + [OP_CHECKSIG] * (extra_sigops_available + 1) + [OP_ENDIF])
        witness_hash_toomany = sha256(witness_program_toomany)
        script_pubkey_toomany = CScript([OP_0, witness_hash_toomany])

        # If we spend this script instead, we would exactly reach our sigop
        # limit (for witness sigops).
        witness_program_justright = CScript([OP_TRUE, OP_IF, OP_TRUE, OP_ELSE] + [OP_CHECKSIG] * (extra_sigops_available) + [OP_ENDIF])
        witness_hash_justright = sha256(witness_program_justright)
        script_pubkey_justright = CScript([OP_0, witness_hash_justright])

        # First split our available utxo into a bunch of outputs
        split_value = self.utxo[0].nValue // outputs
        tx = CTransaction()
        tx.vin.append(CTxIn(COutPoint(self.utxo[0].sha256, self.utxo[0].n), b""))
        for i in range(outputs):
            tx.vout.append(CTxOut(split_value, script_pubkey))
        tx.vout[-2].scriptPubKey = script_pubkey_toomany
        tx.vout[-1].scriptPubKey = script_pubkey_justright
        tx.rehash()

        block_1 = self.build_next_block()
        self.update_witness_block_with_transactions(block_1, [tx])
        test_witness_block(self.nodes[0].rpc, self.test_node, block_1, accepted=True)

        tx2 = CTransaction()
        # If we try to spend the first n-1 outputs from tx, that should be
        # too many sigops.
        total_value = 0
        for i in range(outputs - 1):
            tx2.vin.append(CTxIn(COutPoint(tx.sha256, i), b""))
            tx2.wit.vtxinwit.append(CTxInWitness())
            tx2.wit.vtxinwit[-1].scriptWitness.stack = [witness_program]
            total_value += tx.vout[i].nValue
        tx2.wit.vtxinwit[-1].scriptWitness.stack = [witness_program_toomany]
        tx2.vout.append(CTxOut(total_value, CScript([OP_TRUE])))
        tx2.rehash()

        block_2 = self.build_next_block()
        self.update_witness_block_with_transactions(block_2, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block_2, accepted=False)

        # Try dropping the last input in tx2, and add an output that has
        # too many sigops (contributing to legacy sigop count).
        checksig_count = (extra_sigops_available // 4) + 1
        script_pubkey_checksigs = CScript([OP_CHECKSIG] * checksig_count)
        tx2.vout.append(CTxOut(0, script_pubkey_checksigs))
        tx2.vin.pop()
        tx2.wit.vtxinwit.pop()
        tx2.vout[0].nValue -= tx.vout[-2].nValue
        tx2.rehash()
        block_3 = self.build_next_block()
        self.update_witness_block_with_transactions(block_3, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block_3, accepted=False)

        # If we drop the last checksig in this output, the tx should succeed.
        block_4 = self.build_next_block()
        tx2.vout[-1].scriptPubKey = CScript([OP_CHECKSIG] * (checksig_count - 1))
        tx2.rehash()
        self.update_witness_block_with_transactions(block_4, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block_4, accepted=True)

        # Reset the tip back down for the next test
        sync_blocks(self.nodes)
        for x in self.nodes:
            x.invalidateblock(block_4.hash)

        # Try replacing the last input of tx2 to be spending the last
        # output of tx
        block_5 = self.build_next_block()
        tx2.vout.pop()
        tx2.vin.append(CTxIn(COutPoint(tx.sha256, outputs - 1), b""))
        tx2.wit.vtxinwit.append(CTxInWitness())
        tx2.wit.vtxinwit[-1].scriptWitness.stack = [witness_program_justright]
        tx2.rehash()
        self.update_witness_block_with_transactions(block_5, [tx2])
        test_witness_block(self.nodes[0].rpc, self.test_node, block_5, accepted=True)

        # TODO: test p2sh sigop counting

if __name__ == '__main__':
    SegWitTest().main()