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Merge bitcoin/bitcoin#35850: fuzz: Implement connect_block harness

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2777300c68 fuzz: Implement connect_block harness (Robin David)
40add915be test: Add reset to CuckooCache (Eugene Siegel)

Pull request description:

  Adds a fuzz target that directly calls `ConnectBlock` with `fJustCheck` set to true, so it hits block/transaction validation without writing undo data or updating the chainstate.

  This PR is essentially https://github.com/bitcoin/bitcoin/pull/34651 with some minor tweaks and style cleanups. Additional validation harnesses (e.g. https://github.com/bitcoin/bitcoin/pull/34895) could build on this test's setup.

ACKs for top commit:
  Crypt-iQ:
    ACK 2777300c68
  nervana21:
    tACK 2777300c68

Tree-SHA512: e2dc74154a6e29e0f3eaec9caeeec53d64bcc96adb0d1739281da97712dd931c3937eaf71f977bfc9c9330f26e35b3633f72788143b76e24e17c37b0a4258ba4
This commit is contained in:
merge-script
2026-08-27 10:24:55 +01:00
parent a24110cef7 2777300c68
commit 2224e4af6c
3 changed files with 490 additions and 1 deletions
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10
src/cuckoocache.h
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@@ -329,7 +329,7 @@ public:
/** setup initializes the container to store no more than new_size
* elements and no less than 2 elements.
*
* setup should only be called once.
* setup should only be called once. TestOnlyReset() is the exception.
*
* @param new_size the desired number of elements to store
* @returns the maximum number of elements storable
@@ -483,6 +483,14 @@ public:
}
return false;
}
/** Empty the cache and re-run setup(). */
void TestOnlyReset()
{
table.clear();
epoch_flags.clear();
setup(0);
}
};
} // namespace CuckooCache

1
src/test/fuzz/CMakeLists.txt
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@@ -30,6 +30,7 @@ add_executable(fuzz
cmpctblock.cpp
coins_view.cpp
coinscache_sim.cpp
connect_block.cpp
connman.cpp
crypto.cpp
crypto_aes256.cpp

480
src/test/fuzz/connect_block.cpp Normal file
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@@ -0,0 +1,480 @@
// Copyright (c) 2026-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <addresstype.h>
#include <chain.h>
#include <consensus/amount.h>
#include <consensus/merkle.h>
#include <node/kernel_notifications.h>
#include <node/mining_types.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <pubkey.h>
#include <script/interpreter.h>
#include <script/script.h>
#include <sync.h>
#include <test/fuzz/FuzzedDataProvider.h>
#include <test/fuzz/fuzz.h>
#include <test/fuzz/util.h>
#include <test/util/mining.h>
#include <test/util/script.h>
#include <test/util/setup_common.h>
#include <test/util/time.h>
#include <txmempool.h>
#include <uint256.h>
#include <validation.h>
#include <validationinterface.h>
#include <algorithm>
#include <cstdint>
#include <memory>
#include <utility>
#include <vector>
namespace {
TestingSetup* g_setup;
/** Vector of blocks to keep references to blocks (to enable fuzzing input to pick one to build upon) */
static std::vector<std::shared_ptr<CBlock>> g_blocks;
/** CTxIns for spending outputs, which can be unspent, already spent, or an immature coinbase. */
static std::vector<CTxIn> g_spend_candidate_txins;
/** Static P2SH_OP_TRUE script */
static const CScript P2SH_OP_TRUE = CScript() << OP_HASH160 << ToByteVector(ScriptHash(CScript() << OP_TRUE)) << OP_EQUAL;
/** Static P2SH_OP_TRUE unlock script */
static const CScript P2SH_OP_TRUE_UNLOCK = CScript() << MakeUCharSpan(CScript() << OP_TRUE);
/** Static TAPROOT_OP_TRUE script and its witness */
static CScript TAPROOT_OP_TRUE;
static std::vector<std::vector<uint8_t>> TAPROOT_OP_TRUE_WITNESS;
/**
* Initialize TAPROOT_OP_TRUE and TAPROOT_OP_TRUE_WITNESS static variables.
*/
static void InitTaprootScript()
{
uint256 merkle_tree_hash = ComputeTapleafHash(TAPROOT_LEAF_TAPSCRIPT, MakeUCharSpan(CScript() << OP_TRUE));
uint256 internal_key{std::vector<uint8_t>(32, 1)};
auto res = XOnlyPubKey(internal_key).CreateTapTweak(&merkle_tree_hash);
Assert(res.has_value());
auto control = ToByteVector(internal_key);
control.insert(control.begin(), TAPROOT_LEAF_TAPSCRIPT | (res->second ? 1 : 0));
TAPROOT_OP_TRUE = CScript() << OP_1 << ToByteVector(res->first);
TAPROOT_OP_TRUE_WITNESS.clear();
TAPROOT_OP_TRUE_WITNESS.emplace_back(ToByteVector(CScript() << OP_TRUE));
TAPROOT_OP_TRUE_WITNESS.emplace_back(std::move(control));
}
/**
* Given a transaction and an output index, create a CTxIn that can be
* used to spend it.
*/
static CTxIn GetSpendingScript(const CTransaction& tx, uint32_t vout_index)
{
Assert(vout_index < tx.vout.size());
const CTxOut& output = tx.vout[vout_index];
CTxIn res{COutPoint(tx.GetHash(), vout_index)};
if (output.scriptPubKey == P2WSH_OP_TRUE) {
res.scriptSig = CScript();
res.scriptWitness.stack.push_back(WITNESS_STACK_ELEM_OP_TRUE);
} else if (output.scriptPubKey == P2SH_OP_TRUE) {
res.scriptSig = P2SH_OP_TRUE_UNLOCK;
} else if (output.scriptPubKey == CScript()) {
res.scriptSig = CScript() << OP_TRUE;
} else if (output.scriptPubKey == TAPROOT_OP_TRUE) {
res.scriptSig = CScript();
res.scriptWitness.stack = TAPROOT_OP_TRUE_WITNESS;
}
return res;
}
/**
* Add a spend candidate CTxIn unless the output is unspendable.
*/
static void MaybeAddSpendCandidate(std::vector<CTxIn>& pool, const CTransaction& tx, uint32_t vout_index)
{
Assert(vout_index < tx.vout.size());
if (tx.vout[vout_index].scriptPubKey.IsUnspendable()) return;
pool.push_back(GetSpendingScript(tx, vout_index));
}
/**
* Read the block from the BlockManager and add it to g_blocks.
*/
static void LoadCurrentBlock(Chainstate& chainstate, CBlockIndex* current_block)
{
// Read the block from the BlockManager.
Assert(current_block->nHeight >= 0);
// Resize g_blocks if needed.
if (g_blocks.size() <= (size_t)current_block->nHeight) {
g_blocks.resize(current_block->nHeight + 1);
}
g_blocks[current_block->nHeight] = std::make_shared<CBlock>();
Assert(chainstate.m_blockman.ReadBlock(*g_blocks[current_block->nHeight], *current_block));
// Iterate all transaction outputs.
for (const auto& tx : g_blocks[current_block->nHeight]->vtx) {
for (uint32_t vout_index{0}; vout_index < tx->vout.size(); ++vout_index) {
MaybeAddSpendCandidate(g_spend_candidate_txins, *tx, vout_index);
}
}
}
/**
* Read the Chainstate object into g_blocks.
* Then fill g_spend_candidate_txins with inputs that can be tried by the target.
*/
static void LoadCurrentChain()
{
// Clear existing data.
g_blocks.clear();
g_spend_candidate_txins.clear();
{
LOCK(::cs_main);
// Retrieve the current chainstate.
auto& chainstate = Assert(g_setup->m_node.chainman)->ActiveChainstate();
// Make sure it contains a valid mempool.
Assert(chainstate.GetMempool());
// Traverse the chain from tip to genesis.
auto current_block = chainstate.m_chain.Tip();
while (current_block != nullptr) {
LoadCurrentBlock(chainstate, current_block);
// Move to previous block.
current_block = current_block->pprev;
}
}
// Reverse the order of g_spend_candidate_txins to have them in ascending order of
// block height.
std::reverse(g_spend_candidate_txins.begin(), g_spend_candidate_txins.end());
}
/**
* Reset the chainman in the testing setup object.
* Mine 2*COINBASE_MATURITY blocks to have spendable UTXOs.
* It is called once in the initialization function.
*/
void ResetChainman(TestingSetup& setup)
{
SetMockTime(setup.m_node.chainman->GetParams().GenesisBlock().Time());
setup.m_node.chainman.reset();
setup.m_node.notifications->m_shutdown_on_fatal_error = false;
setup.m_make_chainman();
setup.LoadVerifyActivateChainstate();
for (int i = 0; i < 2 * COINBASE_MATURITY; i++) {
node::BlockCreateOptions options;
options.coinbase_output_script = P2WSH_OP_TRUE;
MineBlock(setup.m_node, options);
}
setup.m_node.validation_signals->SyncWithValidationInterfaceQueue();
}
/** Create additional transactions in the mempool that spend
* coins from mature blocks. Otherwise the mined chain only contains
* coinbase transactions.
*/
void AddExtraTxsToMempool(TestingSetup& setup)
{
Assert(setup.m_node.chainman->ActiveChainstate().GetMempool()->size() == 0);
for (size_t i = 1; i <= 10; i++) {
CMutableTransaction ctx;
ctx.version = CTransaction::CURRENT_VERSION;
ctx.vin.resize(1);
// CTxIn is spendable as g_spend_candidate_txins comes from early blocks whose
// coinbases are mature.
ctx.vin[0] = g_spend_candidate_txins[i];
ctx.vout.resize(4);
// Arbitrarily create various outputs of different kinds in the same tx.
// P2WSH
ctx.vout[0].nValue = CAmount(15 * COIN);
ctx.vout[0].scriptPubKey = P2WSH_OP_TRUE;
// P2SH
ctx.vout[1].nValue = CAmount(15 * COIN);
ctx.vout[1].scriptPubKey = P2SH_OP_TRUE;
// Taproot
ctx.vout[2].nValue = CAmount(10 * COIN);
ctx.vout[2].scriptPubKey = TAPROOT_OP_TRUE;
// Empty script
ctx.vout[3].nValue = CAmount(10 * COIN);
ctx.vout[3].scriptPubKey = CScript();
LOCK(::cs_main);
// Add transaction to the mempool.
const MempoolAcceptResult ctx_result = setup.m_node.chainman->ProcessTransaction(MakeTransactionRef(ctx));
Assert(ctx_result.m_result_type == MempoolAcceptResult::ResultType::VALID);
Assert(setup.m_node.chainman->ActiveChainstate().GetMempool()->size() == i);
// Force the mempool to select this transaction even though its fee is zero.
setup.m_node.chainman->ActiveChainstate().GetMempool()->PrioritiseTransaction(ctx.GetHash(), COIN);
}
}
/** Initialize the chain for this target. */
static void initialize_connect_block()
{
// Instantiate REGTEST chain.
static auto testing_setup = MakeNoLogFileContext<TestingSetup>(
/*chain_type=*/ChainType::REGTEST, TestOpts{
.extra_args = {
"-minrelaytxfee=0",
"-acceptnonstdtxn",
},
});
g_setup = testing_setup.get();
// Reset the chainman in the testing setup object.
ResetChainman(*g_setup);
// Initialize Taproot script declared as static variables.
InitTaprootScript();
// Load the chain mined in ResetChainman in global variables g_blocks and
// g_spend_candidate_txins, to make them available to pick by the target.
LoadCurrentChain();
// Prepare multiple transactions for block 201. They spend coins
// from various coinbases that are now mature enough.
AddExtraTxsToMempool(*g_setup);
// Mine block 201, which contains the transactions added to the mempool.
node::BlockCreateOptions options;
options.coinbase_output_script = P2WSH_OP_TRUE;
MineBlock(g_setup->m_node, options);
Assert(g_setup->m_node.chainman->ActiveChainstate().GetMempool()->size() == 0);
// Load the 201st block into g_blocks.
LOCK(::cs_main);
auto& chainstate = Assert(g_setup->m_node.chainman)->ActiveChainstate();
auto current_block = chainstate.m_chain.Tip();
LoadCurrentBlock(chainstate, current_block);
}
/**
* Read one transaction from the fuzzing input through the FuzzedDataProvider.
* It is intended to leave more space to craft complex transactions, especially
* with various script types (P2SH, P2WSH, TAPROOT, NOSCRIPT).
* It is exclusively used by ConsumeBlock to read transactions inside a block.
*/
CTransactionRef ConsumeTransaction(FuzzedDataProvider& fuzzed_data_provider,
std::vector<CTxIn>& additional_txins,
bool coinbase = false,
int target_height = 0)
{
CMutableTransaction tx;
tx.version = fuzzed_data_provider.ConsumeBool() ?
CTransaction::CURRENT_VERSION :
fuzzed_data_provider.ConsumeIntegral<uint32_t>();
tx.nLockTime = fuzzed_data_provider.ConsumeBool() ?
0 :
fuzzed_data_provider.ConsumeIntegral<uint32_t>();
// Some harnesses want to explicitly read coinbase transactions from input.
if (coinbase) {
// vin size is hardcoded.
tx.vin.resize(1);
tx.vin[0].prevout.SetNull();
if (fuzzed_data_provider.ConsumeBool()) {
// 1/2 probability of a valid vin.
tx.vin[0].scriptSig = CScript() << target_height;
} else {
// Read arbitrary data from input as scriptSig.
auto script_sig = ConsumeRandomLengthByteVector<unsigned char>(fuzzed_data_provider, 100);
tx.vin[0].scriptSig.assign(script_sig.begin(), script_sig.end());
}
} else {
// Read a normal transaction, with up to 10 inputs.
int num_inputs = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 10);
tx.vin.resize(num_inputs);
for (int i = 0; i < num_inputs; i++) {
// Read an integer to choose a CTxIn or reuse one generated by the
// input. The content of the CTxIn is not read from the input per se.
uint32_t input_index = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(0, g_spend_candidate_txins.size() + additional_txins.size() - 1);
if (input_index < g_spend_candidate_txins.size()) {
// Pick it from the spend candidates.
tx.vin[i] = g_spend_candidate_txins[input_index];
} else {
// Pick it in the additional_txins set.
Assert((input_index - g_spend_candidate_txins.size()) < additional_txins.size());
tx.vin[i] = additional_txins[input_index - g_spend_candidate_txins.size()];
}
// Enable the fuzzer to mutate every CTxIn field after it is taken
// from the spend candidates.
if (fuzzed_data_provider.ConsumeBool()) {
tx.vin[i].nSequence = ConsumeSequence(fuzzed_data_provider);
}
if (fuzzed_data_provider.ConsumeBool()) {
tx.vin[i].prevout.n = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
}
if (fuzzed_data_provider.ConsumeBool()) {
tx.vin[i].prevout.hash = Txid::FromUint256(ConsumeUInt256(fuzzed_data_provider));
}
if (fuzzed_data_provider.ConsumeBool()) {
tx.vin[i].scriptSig = ConsumeScript(fuzzed_data_provider);
}
if (fuzzed_data_provider.ConsumeBool()) {
tx.vin[i].scriptWitness.stack.clear();
int num_wit = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 10);
for (int j = 0; j < num_wit; j++) {
tx.vin[i].scriptWitness.stack.push_back(ConsumeRandomLengthByteVector<unsigned char>(fuzzed_data_provider, 100));
}
}
}
}
// Read outputs.
int num_outputs = fuzzed_data_provider.ConsumeIntegralInRange<int>(1, 10);
tx.vout.resize(num_outputs);
for (int i = 0; i < num_outputs; i++) {
// Read CAmount to spend.
tx.vout[i].nValue = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-10, 50 * COIN + 10);
// Read scriptPubKey type into one of the valid types.
CallOneOf(
fuzzed_data_provider,
[&] {
// P2WSH
tx.vout[i].scriptPubKey = P2WSH_OP_TRUE;
},
[&] {
// P2SH
tx.vout[i].scriptPubKey = P2SH_OP_TRUE;
},
[&] {
// Taproot
tx.vout[i].scriptPubKey = TAPROOT_OP_TRUE;
},
[&] {
// Empty script
tx.vout[i].scriptPubKey = CScript();
},
[&] {
// Read arbitrary scriptPubKey.
tx.vout[i].scriptPubKey = ConsumeScript(fuzzed_data_provider);
});
}
// Create the shared pointer to the CTransaction object.
auto res = MakeTransactionRef(tx);
if (!coinbase) {
// Create spending scripts for CTxOuts so they can be spent in later
// transactions. Do it here as the transaction hash is definitive.
for (int i = 0; i < num_outputs; i++) {
MaybeAddSpendCandidate(additional_txins, *res, i);
}
}
return res;
}
/**
* Consume a block from the fuzzing input.
* It builds a block on top of the given prev_block.
*/
CBlock ConsumeBlock(FuzzedDataProvider& fuzzed_data_provider, const CBlock& prev_block, int target_height,
std::vector<CTxIn>& additional_txins)
{
CBlock block;
// Initialize header fields.
block.nVersion = g_blocks.back()->nVersion;
block.hashPrevBlock = prev_block.GetHash();
block.nTime = g_blocks.back()->nTime + 2;
block.nBits = g_blocks.back()->nBits;
// Give the fuzzer input the ability to mutate block header fields.
if (fuzzed_data_provider.ConsumeBool()) {
block.nVersion = fuzzed_data_provider.ConsumeIntegral<int32_t>();
}
if (fuzzed_data_provider.ConsumeBool()) {
block.hashPrevBlock = ConsumeUInt256(fuzzed_data_provider);
}
if (fuzzed_data_provider.ConsumeBool()) {
block.nTime = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
}
if (fuzzed_data_provider.ConsumeBool()) {
block.nBits = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
}
// Read the coinbase transaction from the input.
block.vtx.push_back(ConsumeTransaction(fuzzed_data_provider, additional_txins, true, target_height));
// Read up to num_tx transactions from the input.
int num_tx = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 5);
for (int i = 0; i < num_tx; i++) {
block.vtx.push_back(ConsumeTransaction(fuzzed_data_provider, additional_txins));
}
// Commit witness.
if (fuzzed_data_provider.ConsumeBool()) {
g_setup->m_node.chainman->GenerateCoinbaseCommitment(block, nullptr);
}
// Set hashMerkleRoot to expected value.
block.hashMerkleRoot = BlockMerkleRoot(block);
// Let the fuzzer mutate hashMerkleRoot.
if (fuzzed_data_provider.ConsumeBool()) {
block.hashMerkleRoot = ConsumeUInt256(fuzzed_data_provider);
}
// Read the nonce from the input.
block.nNonce = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
return block;
}
FUZZ_TARGET(connect_block, .init = initialize_connect_block)
{
SeedRandomStateForTest(SeedRand::ZEROS);
FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
FakeNodeClock clock{g_blocks.back()->Time() + 2s};
LOCK(::cs_main);
g_setup->m_node.chainman->m_validation_cache.m_script_execution_cache.TestOnlyReset();
Chainstate& active_chainstate = g_setup->m_node.chainman->ActiveChainstate();
CBlockIndex* active_tip = active_chainstate.m_chain.Tip();
Assert(active_tip->GetBlockHash() == g_blocks.back()->GetHash());
CCoinsViewCache active_coins(&active_chainstate.CoinsTip());
// Read a new block from the data provider.
std::vector<CTxIn> additional_txins;
CBlock block = ConsumeBlock(fuzzed_data_provider, *g_blocks.back(), active_tip->nHeight + 1, additional_txins);
// Duplicate a transaction (not the coinbase) from the previous block
// to hit the BIP30 check.
if (fuzzed_data_provider.ConsumeBool()) {
const auto& duplicates = g_blocks.back()->vtx;
block.vtx.push_back(duplicates[fuzzed_data_provider.ConsumeIntegralInRange<size_t>(1, duplicates.size() - 1)]);
}
// Compute new CBlockIndex object.
uint256 current_hash = block.GetHash();
CBlockIndex new_index(block);
new_index.pprev = active_tip;
new_index.nHeight = active_tip->nHeight + 1;
new_index.phashBlock = &current_hash;
// Try to connect the block.
BlockValidationState state;
bool connected = active_chainstate.ConnectBlock(block,
state,
&new_index,
active_coins,
/*fJustCheck=*/true);
Assert(connected == state.IsValid());
}
} // namespace