bitcoin/test/functional/feature_chain_tiebreaks.py
marcofleon 20ae9b98ea Extend functional test for setBlockIndexCandidates UB
Fix the from-disk subtest to use a separate node so it builds on a
clean genesis block, rather than the leftover chain from the
in-memory subtest.

Change from a two-way to a three-way block race. The UB in the old
LoadChainTip (mutating nSequenceId, a sort key, while the block is
in setBlockIndexCandidates) corrupts the internal tree structure,
resulting in a failed erase that leaves stale blocks in the set
alongside the tip. With only two competing blocks, this is caught
by libstdc++ but not by libc++. A three-way split triggers the bug
on both implementations.

To trigger CheckBlockIndex (where the crashing assertion is), replace
the restart loop with sending a new block after a single restart.
2026-03-04 20:13:53 +00:00

165 lines
6.1 KiB
Python
Executable File

#!/usr/bin/env python3
# Copyright (c) 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 that the correct active block is chosen in complex reorgs."""
from test_framework.blocktools import create_block
from test_framework.messages import CBlockHeader
from test_framework.p2p import P2PDataStore
from test_framework.test_framework import BitcoinTestFramework
from test_framework.util import assert_equal
class ChainTiebreaksTest(BitcoinTestFramework):
def set_test_params(self):
self.num_nodes = 2
self.setup_clean_chain = True
def setup_network(self):
self.setup_nodes()
@staticmethod
def send_headers(node, blocks):
"""Submit headers for blocks to node."""
for block in blocks:
# Use RPC rather than P2P, to prevent the message from being interpreted as a block
# announcement.
node.submitheader(hexdata=CBlockHeader(block).serialize().hex())
def test_chain_split_in_memory(self):
node = self.nodes[0]
# Add P2P connection to bitcoind
peer = node.add_p2p_connection(P2PDataStore())
self.log.info('Precomputing blocks')
#
# /- B3 -- B7
# B1 \- B8
# / \
# / \ B4 -- B9
# B0 \- B10
# \
# \ /- B5
# B2
# \- B6
#
blocks = []
# Construct B0, building off genesis.
start_height = node.getblockcount()
blocks.append(create_block(
hashprev=int(node.getbestblockhash(), 16),
tmpl={"height": start_height + 1}
))
blocks[-1].solve()
# Construct B1-B10.
for i in range(1, 11):
blocks.append(create_block(
hashprev=blocks[(i - 1) >> 1].hash_int,
tmpl={
"height": start_height + (i + 1).bit_length(),
# Make sure each block has a different hash.
"curtime": blocks[-1].nTime + 1,
}
))
blocks[-1].solve()
self.log.info('Make sure B0 is accepted normally')
peer.send_blocks_and_test([blocks[0]], node, success=True)
# B0 must be active chain now.
assert_equal(node.getbestblockhash(), blocks[0].hash_hex)
self.log.info('Send B1 and B2 headers, and then blocks in opposite order')
self.send_headers(node, blocks[1:3])
peer.send_blocks_and_test([blocks[2]], node, success=True)
peer.send_blocks_and_test([blocks[1]], node, success=False)
# B2 must be active chain now, as full data for B2 was received first.
assert_equal(node.getbestblockhash(), blocks[2].hash_hex)
self.log.info('Send all further headers in order')
self.send_headers(node, blocks[3:])
# B2 is still the active chain, headers don't change this.
assert_equal(node.getbestblockhash(), blocks[2].hash_hex)
self.log.info('Send blocks B7-B10')
peer.send_blocks_and_test([blocks[7]], node, success=False)
peer.send_blocks_and_test([blocks[8]], node, success=False)
peer.send_blocks_and_test([blocks[9]], node, success=False)
peer.send_blocks_and_test([blocks[10]], node, success=False)
# B2 is still the active chain, as B7-B10 have missing parents.
assert_equal(node.getbestblockhash(), blocks[2].hash_hex)
self.log.info('Send parents B3-B4 of B8-B10 in reverse order')
peer.send_blocks_and_test([blocks[4]], node, success=False, force_send=True)
peer.send_blocks_and_test([blocks[3]], node, success=False, force_send=True)
# B9 is now active. Despite B7 being received earlier, the missing parent.
assert_equal(node.getbestblockhash(), blocks[9].hash_hex)
self.log.info('Invalidate B9-B10')
node.invalidateblock(blocks[9].hash_hex)
node.invalidateblock(blocks[10].hash_hex)
# B7 is now active.
assert_equal(node.getbestblockhash(), blocks[7].hash_hex)
# Invalidate blocks to start fresh on the next test
node.invalidateblock(blocks[0].hash_hex)
def test_chain_split_from_disk(self):
node = self.nodes[1]
peer = node.add_p2p_connection(P2PDataStore())
self.generate(node, 1, sync_fun=self.no_op)
self.log.info('Precomputing blocks')
#
# /- A1
# /
# G -- B1 --- A2
# \
# \- A3
#
blocks = []
# Construct three equal-work blocks building from the tip.
start_height = node.getblockcount()
tip_block = node.getblock(node.getbestblockhash())
prev_time = tip_block["time"]
for i in range(0, 3):
blocks.append(create_block(
hashprev=int(tip_block["hash"], 16),
tmpl={"height": start_height + 1,
# Make sure each block has a different hash.
"curtime": prev_time + i + 1,
}
))
blocks[-1].solve()
# Send blocks and test that only the first one connects
self.log.info('Send A1, A2, and A3. Make sure that only the former connects')
peer.send_blocks_and_test([blocks[0]], node, success=True)
peer.send_blocks_and_test([blocks[1]], node, success=False)
peer.send_blocks_and_test([blocks[2]], node, success=False)
# Restart and send a new block
self.restart_node(1)
assert_equal(blocks[0].hash_hex, node.getbestblockhash())
peer = node.add_p2p_connection(P2PDataStore())
next_block = create_block(
hashprev=blocks[0].hash_int,
tmpl={"height": start_height + 2,
"curtime": prev_time + 10,
}
)
next_block.solve()
peer.send_blocks_and_test([next_block], node, success=True)
def run_test(self):
self.test_chain_split_in_memory()
self.test_chain_split_from_disk()
if __name__ == '__main__':
ChainTiebreaksTest(__file__).main()