READ THE CODE

Inside Bitcoin

The code behind the network, with room to understand it.

Stable release v32.1bitcoin/bitcoin · f0de87f04062 ↗3,020 source files · 47.5 MB stored on the server440 file guides

Release published 2026-10-28 · Snapshot fetched 2026-11-01. Latest stable release at fetch time; development branches and Git history are excluded. Only the selected code window and visible folders load here.

5,349 bytes · SHA-256 fb797d56ba19e0f1… · View upstream ↗

1#!/usr/bin/env python3
2# Copyright (c) The Bitcoin Core developers
3# Distributed under the MIT software license, see the accompanying
4# file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6"""
7Test that an attacker can't degrade compact block relay by sending unsolicited
8mutated blocks to clear in-flight blocktxn requests from other honest peers.
9"""
10
11from test_framework.p2p import P2PInterface
12from test_framework.messages import (
13    BlockTransactions,
14    msg_cmpctblock,
15    msg_block,
16    msg_blocktxn,
17    msg_headers,
18    HeaderAndShortIDs,
19    msg_sendcmpct,
20)
21from test_framework.test_framework import BitcoinTestFramework
22from test_framework.blocktools import (
23    COINBASE_MATURITY,
24    create_block,
25    add_witness_commitment,
26    NORMAL_GBT_REQUEST_PARAMS,
27)
28from test_framework.util import assert_equal
29from test_framework.wallet import MiniWallet
30import copy
31
32class MutatedBlocksTest(BitcoinTestFramework):
33    def set_test_params(self):
34        self.setup_clean_chain = True
35        self.num_nodes = 1
36        self.extra_args = [
37            [
38                "-testactivationheight=segwit@1", # causes unconnected headers/blocks to not have segwit considered deployed
39            ],
40        ]
41
42    def run_test(self):
43        self.wallet = MiniWallet(self.nodes[0])
44        self.generate(self.wallet, COINBASE_MATURITY)
45
46        honest_relayer = self.nodes[0].add_outbound_p2p_connection(P2PInterface(), p2p_idx=0, connection_type="outbound-full-relay")
47        honest_relayer.send_and_ping(msg_sendcmpct())
48        attacker = self.nodes[0].add_p2p_connection(P2PInterface())
49
50        # Create new block with two transactions (coinbase + 1 self-transfer).
51        # The self-transfer transaction is needed to trigger a compact block
52        # `getblocktxn` roundtrip.
53        tx = self.wallet.create_self_transfer()["tx"]
54        block = create_block(tmpl=self.nodes[0].getblocktemplate(NORMAL_GBT_REQUEST_PARAMS), txlist=[tx])
55        add_witness_commitment(block)
56        block.solve()
57
58        # Create mutated version of the block by changing the transaction
59        # version on the self-transfer.
60        mutated_block = copy.deepcopy(block)
61        mutated_block.vtx[1].version = 4
62
63        # Send block header through the honest relayer
64        honest_relayer.send_without_ping(msg_headers([block]))
65        honest_relayer.wait_for_getdata([block.hash_int], timeout=30)
66
67        # Announce the new block via a compact block through the honest relayer
68        cmpctblock = HeaderAndShortIDs()
69        cmpctblock.initialize_from_block(block, use_witness=True)
70        honest_relayer.send_without_ping(msg_cmpctblock(cmpctblock.to_p2p()))
71
72        # Wait for a `getblocktxn` that attempts to fetch the self-transfer
73        def self_transfer_requested():
74            if not honest_relayer.last_message.get('getblocktxn'):
75                return False
76
77            get_block_txn = honest_relayer.last_message['getblocktxn']
78            return get_block_txn.block_txn_request.blockhash == block.hash_int and \
79                   get_block_txn.block_txn_request.indexes == [1]
80        honest_relayer.wait_until(self_transfer_requested, timeout=5)
81
82        # Block at height 101 should be the only one in flight from peer 0
83        peer_info_prior_to_attack = self.nodes[0].getpeerinfo()
84        assert_equal(peer_info_prior_to_attack[0]['id'], 0)
85        assert_equal([101], peer_info_prior_to_attack[0]["inflight"])
86
87        # Attempt to clear the honest relayer's download request by sending the
88        # mutated block (as the attacker).
89        with self.nodes[0].assert_debug_log(expected_msgs=["Block mutated: bad-txnmrklroot, hashMerkleRoot mismatch"]):
90            attacker.send_without_ping(msg_block(mutated_block))
91            # Attacker should get disconnected for sending a mutated block
92            attacker.wait_for_disconnect(timeout=5)
93
94        # Block at height 101 should *still* be the only block in-flight from
95        # peer 0
96        peer_info_after_attack = self.nodes[0].getpeerinfo()
97        assert_equal(peer_info_after_attack[0]['id'], 0)
98        assert_equal([101], peer_info_after_attack[0]["inflight"])
99
100        # The honest relayer should be able to complete relaying the block by
101        # sending the blocktxn that was requested.
102        block_txn = msg_blocktxn()
103        block_txn.block_transactions = BlockTransactions(blockhash=block.hash_int, transactions=[tx])
104        honest_relayer.send_and_ping(block_txn)
105        assert_equal(self.nodes[0].getbestblockhash(), block.hash_hex)
106
107        # Check that unexpected-witness mutation check doesn't trigger on a header that doesn't connect to anything
108        assert_equal(len(self.nodes[0].getpeerinfo()), 1)
109        attacker = self.nodes[0].add_p2p_connection(P2PInterface())
110        block_missing_prev = copy.deepcopy(block)
111        block_missing_prev.hashPrevBlock = 123
112        block_missing_prev.solve()
113
114        # Check that non-connecting block causes disconnect
115        assert_equal(len(self.nodes[0].getpeerinfo()), 2)
116        with self.nodes[0].assert_debug_log(expected_msgs=["AcceptBlock FAILED (prev-blk-not-found)"]):
117            attacker.send_without_ping(msg_block(block_missing_prev))
118            attacker.wait_for_disconnect(timeout=5)
119
120
121if __name__ == '__main__':
122    MutatedBlocksTest(__file__).main()
123

src/wallet/receive.cpp

src/wallet/coinselection.cpp

src/consensus/validation.h

src/primitives/transaction.cpp

src/script/descriptor.cpp

src/bitcoin-cli.cpp

src/rpc/blockchain.cpp

src/rpc/rawtransaction.cpp

src/init.cpp

src/crypto/sha256.cpp

src/consensus/merkle.h

src/consensus/tx_check.h

src/consensus/tx_verify.h

src/policy/feerate.h

src/policy/feerate.cpp

src/primitives/transaction_identifier.h

src/chainparamsbase.h

src/chainparamsbase.cpp

src/util/moneystr.cpp

src/crypto/ripemd160.h

src/crypto/sha1.h

src/crypto/sha512.h

src/crypto/hmac_sha256.h

src/crypto/hmac_sha512.h

src/crypto/hmac_sha256.cpp

src/crypto/hmac_sha512.cpp

src/crypto/hkdf_sha256_32.h

src/crypto/hkdf_sha256_32.cpp

src/support/cleanse.h

src/support/cleanse.cpp

src/crypto/siphash.cpp

src/crypto/muhash.h

src/crypto/chacha20.h

src/crypto/poly1305.h

src/crypto/chacha20poly1305.h

src/crypto/chacha20poly1305.cpp

src/util/chaintype.cpp

src/util/obfuscation.h

src/util/byte_units.h

src/util/overflow.h

src/blockencodings.cpp

src/net_permissions.cpp

src/policy/packages.cpp

src/policy/rbf.cpp

src/policy/truc_policy.cpp

src/policy/ephemeral_policy.cpp

src/policy/settings.cpp

src/policy/policy.cpp

src/node/transaction.cpp

src/node/coin.cpp

src/rpc/client.cpp

src/rpc/external_signer.cpp

src/rpc/request.cpp

src/rpc/server_util.cpp

src/rpc/fees.cpp

src/rpc/output_script.cpp

src/rpc/rawtransaction_util.cpp

src/rpc/rawtransaction_util.h

src/rpc/register.h

src/rpc/request.h

src/rpc/server_util.h

src/rpc/protocol.h

src/rpc/server.h

src/rpc/signmessage.cpp

src/rpc/txoutproof.cpp

src/rpc/util.cpp

src/rpc/util.h

src/wallet/rpc/addresses.cpp

src/wallet/rpc/backup.cpp

src/wallet/rpc/coins.cpp

src/wallet/rpc/encrypt.cpp

src/wallet/rpc/signmessage.cpp

src/wallet/rpc/util.cpp

src/wallet/rpc/util.h

src/wallet/coincontrol.cpp

src/wallet/coincontrol.h

src/wallet/context.cpp

src/wallet/context.h

src/wallet/crypter.cpp

src/wallet/crypter.h

src/wallet/db.cpp

src/wallet/export.cpp

src/wallet/external_signer_scriptpubkeyman.cpp

src/wallet/rpc/spend.cpp

src/wallet/rpc/transactions.cpp

src/wallet/rpc/wallet.cpp

src/wallet/feebumper.cpp

src/wallet/feebumper.h

src/index/base.h

src/index/base.cpp

src/index/txindex.h

src/index/txindex.cpp

src/index/txindex_key.h

src/index/txospenderindex.h

src/index/txospenderindex.cpp

src/index/blockfilterindex.h

src/index/blockfilterindex.cpp

src/index/coinstatsindex.h

src/index/coinstatsindex.cpp

src/index/db_key.h

src/index/disktxpos.h

src/kernel/chain.cpp

src/kernel/chain.h

src/kernel/checks.cpp

src/kernel/checks.h

src/kernel/context.cpp

src/kernel/context.h

src/kernel/cs_main.cpp

src/kernel/cs_main.h

src/kernel/disconnected_transactions.cpp

src/kernel/disconnected_transactions.h

src/kernel/mempool_removal_reason.cpp

src/kernel/mempool_removal_reason.h

src/kernel/coinstats.cpp

src/kernel/coinstats.h

src/kernel/chainparams.cpp

src/kernel/chainparams.h

src/wallet/sqlite.cpp

src/wallet/sqlite.h

src/wallet/transaction.cpp

src/wallet/transaction.h

src/wallet/dump.cpp

src/wallet/dump.h

src/wallet/init.cpp

src/wallet/walletutil.cpp

src/wallet/walletutil.h

src/wallet/wallettool.cpp

src/wallet/wallettool.h

src/wallet/export.h

src/wallet/migrate.cpp

src/wallet/migrate.h

src/wallet/db.h

src/wallet/walletdb.cpp

src/wallet/interfaces.cpp

src/wallet/scriptpubkeyman.cpp

src/wallet/scriptpubkeyman.h

src/kernel/bitcoinkernel.cpp

src/kernel/bitcoinkernel.h

src/kernel/bitcoinkernel_wrapper.h

src/node/chainstate.cpp

src/node/chainstate.h

src/node/blockstorage.cpp

src/node/blockstorage.h

src/node/mempool_persist.cpp

src/node/mempool_persist.h

src/node/utxo_snapshot.cpp

src/node/utxo_snapshot.h

src/node/kernel_notifications.cpp

src/node/kernel_notifications.h

src/node/blockmanager_args.cpp

src/kernel/blockmanager_opts.h

src/util/expected.cpp

src/policy/settings.h

src/util/types.h

src/kernel/messagestartchars.h

src/kernel/warning.h

src/util/exception.h

src/common/license_info.h

src/node/coins_view_args.h

src/node/database_args.h

src/util/batchpriority.h

src/util/ui_change_type.h

src/node/coins_view_args.cpp

src/node/peerman_args.h

src/util/serfloat.h

src/node/blockmanager_args.h

src/node/database_args.cpp

src/util/overloaded.h

src/interfaces/types.h

src/node/chainstatemanager_args.h

src/node/minisketchwrapper.h

src/util/macros.h

src/util/syserror.h

src/common/run_command.h

src/util/bytevectorhash.cpp

src/node/mempool_persist_args.cpp

src/util/exec.h

src/util/rbf.h

src/crypto/hex_base.h

src/node/mempool_persist_args.h

src/interfaces/echo.h

src/util/any.h

src/util/batchpriority.cpp

src/util/threadnames.h

src/node/coin.h

src/node/mempool_args.h

src/util/asmap.h

src/util/bytevectorhash.h

src/node/context.cpp

src/util/insert.h

src/util/readwritefile.h

src/node/peerman_args.cpp

src/node/interface_ui.cpp

src/interfaces/handler.h

src/node/mining_args.h

src/util/hasher.cpp

src/common/init.h

src/kernel/mempool_limits.h

src/common/system.h

src/crypto/sha3.h

src/util/threadinterrupt.cpp

src/node/protocol_version.h

src/util/exception.cpp

src/common/messages.h

src/node/connection_types.cpp

src/util/bip32.h

src/common/license_info.cpp

src/util/stdmutex.h

src/common/run_command.cpp

src/util/check.cpp

src/util/golombrice.h

src/node/types.h

src/node/timeoffsets.h

src/util/readwritefile.cpp

src/util/fastrange.h

src/util/signalinterrupt.h

src/util/task_runner.h

src/util/syserror.cpp

src/common/interfaces.cpp

src/common/types.h

src/util/threadinterrupt.h

src/kernel/chainstatemanager_opts.h

src/node/psbt.h

src/policy/ephemeral_policy.h

src/util/trace.h

src/common/url.cpp

src/kernel/mempool_options.h

src/util/serfloat.cpp

src/kernel/notifications_interface.h

src/node/timeoffsets.cpp

src/node/warnings.cpp

src/util/hash_type.h

src/crypto/hex_base.cpp

src/node/eviction.h

src/util/tokenbucket.h

src/crypto/aes.h

src/common/pcp.h

src/util/feefrac.cpp

src/node/transaction.h

src/util/threadnames.cpp

src/common/signmessage.h

src/util/exec.cpp

src/util/signalinterrupt.cpp

src/clientversion.cpp

src/common/signmessage.cpp

src/compat/assumptions.h

src/compat/byteswap.h

src/deploymentinfo.cpp

src/deploymentinfo.h

src/deploymentstatus.cpp

src/deploymentstatus.h

src/dummywallet.cpp

src/external_signer.h

src/init/bitcoin-gui.cpp

src/init/bitcoin-node.cpp

src/init/bitcoin-qt.cpp

src/init/bitcoin-wallet.cpp

src/init/bitcoind.cpp

src/init/common.h

src/interfaces/init.h

src/interfaces/ipc.h

src/key_io.h

src/logging/categories.h

src/logging/timer.h

src/mapport.h

src/musig.h

src/net_permissions.h

src/netgroup.h

src/netmessagemaker.h

src/node/chainstatemanager_args.cpp

src/node/connection_types.h

src/node/context.h

src/node/interface_ui.h

src/node/mempool_args.cpp

src/node/mining_args.cpp

src/node/minisketchwrapper.cpp

src/node/txreconciliation.h

src/policy/fees/estimator_args.cpp

src/policy/fees/estimator_args.h

src/policy/fees/estimator_man.cpp

src/policy/fees/estimator_man.h

src/policy/packages.h

src/policy/rbf.h

src/policy/truc_policy.h

src/pow.h

src/primitives/block.cpp

src/randomenv.h

src/rest.h

src/script/keyorigin.h

src/script/parsing.cpp

src/script/parsing.h

src/script/script_error.h

src/script/sigcache.cpp

src/script/sigcache.h

src/script/solver.h

src/script/verify_flags.h

src/semaphore_grant.h

src/signet.h

src/span.h

src/support/allocators/secure.h

src/support/allocators/zeroafterfree.h

src/util/tokenpipe.cpp

src/util/translation.h

src/util/vector.h

src/versionbits.h

src/versionbits_impl.h

src/wallet/external_signer_scriptpubkeyman.h

src/wallet/fees.h

src/wallet/load.h

src/wallet/receive.h

src/wallet/rpc/wallet.h

src/wallet/types.h

src/walletinitinterface.h

src/zmq/zmqabstractnotifier.cpp

Independent explanations by MyBitcoinExplorer. Not affiliated with or endorsed by Bitcoin Core. Guides are educational and do not replace the source or its tests.

Bitcoin Core source © its contributors, distributed under the MIT license. Original notices and bundled third-party licenses are retained in the source tree.