/root/bitcoin/src/test/fuzz/connect_block.cpp

Source
// 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 <set>
#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;
/** Set of block hashes in g_blocks */
static std::set<uint256> g_existing_block_hashes;
/** CTxIns for spending outputs (excluding OP_RETURN), 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 (if possible).
 */
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.size() >= 1 && output.scriptPubKey[0] == OP_RETURN)
        return res;

    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;
}


/**
 * Read the block from the BlockManager and add it to g_blocks and g_existing_block_hashes.
 */
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));
    // Update hash set.
    g_existing_block_hashes.insert(g_blocks[current_block->nHeight]->GetHash());

    // 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) {
            auto& vout = tx->vout[vout_index];
            // Do not keep OP_RETURN outputs as they are not spendable.
            if (vout.scriptPubKey.size() >= 1 && vout.scriptPubKey[0] == OP_RETURN) continue;
            // Create the CTxIn that can be used to spend this output.
            g_spend_candidate_txins.push_back(GetSpendingScript(*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_existing_block_hashes.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(Assert(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 201th 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();
        tx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL;
        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.
        switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 4)) {
        case 0:
            // P2WSH
            tx.vout[i].scriptPubKey = P2WSH_OP_TRUE;
            break;
        case 1:
            // P2SH
            tx.vout[i].scriptPubKey = P2SH_OP_TRUE;
            break;
        case 2:
            // Taproot
            tx.vout[i].scriptPubKey = TAPROOT_OP_TRUE;
            break;
        case 3:
            // Empty script
            tx.vout[i].scriptPubKey = CScript();
            break;
        default: {
            // Read arbitrary scriptPubKey.
            tx.vout[i].scriptPubKey = ConsumeScript(fuzzed_data_provider);
            break;
        }
        }
    }

    // Create the shared pointer to the CTransaction object.
    auto res = MakeTransactionRef(tx);

    if (!coinbase) {
        // Create spending scripts for all 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++) {
            additional_txins.emplace_back(GetSpendingScript(*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 (num_tx > 0) {
        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 and avoid reusing a setup block hash.
    block.nNonce = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
    while (g_existing_block_hashes.contains(block.GetHash())) {
        ++block.nNonce;
    }

    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);
    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);

    // 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

Coverage Report

Created: 2026-07-30 14:31

Line	Count	Source
1		// Copyright (c) 2026-present The Bitcoin Core developers
2		// Distributed under the MIT software license, see the accompanying
3		// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5		#include <addresstype.h>
6		#include <chain.h>
7		#include <consensus/amount.h>
8		#include <consensus/merkle.h>
9		#include <node/kernel_notifications.h>
10		#include <node/mining_types.h>
11		#include <primitives/block.h>
12		#include <primitives/transaction.h>
13		#include <pubkey.h>
14		#include <script/interpreter.h>
15		#include <script/script.h>
16		#include <sync.h>
17		#include <test/fuzz/FuzzedDataProvider.h>
18		#include <test/fuzz/fuzz.h>
19		#include <test/fuzz/util.h>
20		#include <test/util/mining.h>
21		#include <test/util/script.h>
22		#include <test/util/setup_common.h>
23		#include <test/util/time.h>
24		#include <txmempool.h>
25		#include <uint256.h>
26		#include <validation.h>
27		#include <validationinterface.h>
28
29		#include <algorithm>
30		#include <cstdint>
31		#include <memory>
32		#include <set>
33		#include <utility>
34		#include <vector>
35
36
37		namespace {
38
39		TestingSetup* g_setup;
40
41		/** Vector of blocks to keep references to blocks (to enable fuzzing input to pick one to build upon) */
42		static std::vector<std::shared_ptr<CBlock>> g_blocks;
43		/** Set of block hashes in g_blocks */
44		static std::set<uint256> g_existing_block_hashes;
45		/** CTxIns for spending outputs (excluding OP_RETURN), which can be unspent, already spent, or an immature coinbase. */
46		static std::vector<CTxIn> g_spend_candidate_txins;
47		/** Static P2SH_OP_TRUE script */
48		static const CScript P2SH_OP_TRUE = CScript() << OP_HASH160 << ToByteVector(ScriptHash(CScript() << OP_TRUE)) << OP_EQUAL;
49		/** Static P2SH_OP_TRUE unlock script */
50		static const CScript P2SH_OP_TRUE_UNLOCK = CScript() << MakeUCharSpan(CScript() << OP_TRUE);
51		/** Static TAPROOT_OP_TRUE script and its witness */
52		static CScript TAPROOT_OP_TRUE;
53		static std::vector<std::vector<uint8_t>> TAPROOT_OP_TRUE_WITNESS;
54
55		/**
56		* Initialize TAPROOT_OP_TRUE and TAPROOT_OP_TRUE_WITNESS static variables.
57		*/
58		static void InitTaprootScript()
59	0	{
60	0	uint256 merkle_tree_hash = ComputeTapleafHash(TAPROOT_LEAF_TAPSCRIPT, MakeUCharSpan(CScript() << OP_TRUE));
61	0	uint256 internal_key{std::vector<uint8_t>(32, 1)};
62	0	auto res = XOnlyPubKey(internal_key).CreateTapTweak(&merkle_tree_hash);
63	0	Assert(res.has_value());
64	0	auto control = ToByteVector(internal_key);
65	0	control.insert(control.begin(), TAPROOT_LEAF_TAPSCRIPT \| (res->second ? 1 : 0)); Branch (65:63): [True: 0, False: 0]
66
67	0	TAPROOT_OP_TRUE = CScript() << OP_1 << ToByteVector(res->first);
68	0	TAPROOT_OP_TRUE_WITNESS.clear();
69	0	TAPROOT_OP_TRUE_WITNESS.emplace_back(ToByteVector(CScript() << OP_TRUE));
70	0	TAPROOT_OP_TRUE_WITNESS.emplace_back(std::move(control));
71	0	}
72
73		/**
74		* Given a transaction and an output index, create a CTxIn that can be used to
75		* spend it (if possible).
76		*/
77		static CTxIn GetSpendingScript(const CTransaction& tx, uint32_t vout_index)
78	14.1k	{
79	14.1k	Assert(vout_index < tx.vout.size());
80	14.1k	const CTxOut& output = tx.vout[vout_index];
81
82	14.1k	CTxIn res{COutPoint(tx.GetHash(), vout_index)};
83	14.1k	if (output.scriptPubKey.size() >= 1 && output.scriptPubKey[0] == OP_RETURN) Branch (83:9): [True: 11.2k, False: 2.85k] Branch (83:44): [True: 57, False: 11.2k]
84	57	return res;
85
86	14.0k	if (output.scriptPubKey == P2WSH_OP_TRUE) { Branch (86:9): [True: 5.66k, False: 8.40k]
87	5.66k	res.scriptSig = CScript();
88	5.66k	res.scriptWitness.stack.push_back(WITNESS_STACK_ELEM_OP_TRUE);
89	8.40k	} else if (output.scriptPubKey == P2SH_OP_TRUE) { Branch (89:16): [True: 1.80k, False: 6.60k]
90	1.80k	res.scriptSig = P2SH_OP_TRUE_UNLOCK;
91	6.60k	} else if (output.scriptPubKey == CScript()) { Branch (91:16): [True: 2.85k, False: 3.75k]
92	2.85k	res.scriptSig = CScript() << OP_TRUE;
93	3.75k	} else if (output.scriptPubKey == TAPROOT_OP_TRUE) { Branch (93:16): [True: 1.88k, False: 1.86k]
94	1.88k	res.scriptSig = CScript();
95	1.88k	res.scriptWitness.stack = TAPROOT_OP_TRUE_WITNESS;
96	1.88k	}
97
98	14.0k	return res;
99	14.1k	}
100
101
102		/**
103		* Read the block from the BlockManager and add it to g_blocks and g_existing_block_hashes.
104		*/
105		static void LoadCurrentBlock(Chainstate& chainstate, CBlockIndex* current_block)
106	0	{
107		// Read the block from the BlockManager.
108	0	Assert(current_block->nHeight >= 0);
109		// Resize g_blocks if needed.
110	0	if (g_blocks.size() <= (size_t)current_block->nHeight) { Branch (110:9): [True: 0, False: 0]
111	0	g_blocks.resize(current_block->nHeight + 1);
112	0	}
113
114	0	g_blocks[current_block->nHeight] = std::make_shared<CBlock>();
115	0	Assert(chainstate.m_blockman.ReadBlock(g_blocks[current_block->nHeight], current_block));
116		// Update hash set.
117	0	g_existing_block_hashes.insert(g_blocks[current_block->nHeight]->GetHash());
118
119		// Iterate all transaction outputs.
120	0	for (const auto& tx : g_blocks[current_block->nHeight]->vtx) { Branch (120:25): [True: 0, False: 0]
121	0	for (uint32_t vout_index{0}; vout_index < tx->vout.size(); ++vout_index) { Branch (121:38): [True: 0, False: 0]
122	0	auto& vout = tx->vout[vout_index];
123		// Do not keep OP_RETURN outputs as they are not spendable.
124	0	if (vout.scriptPubKey.size() >= 1 && vout.scriptPubKey[0] == OP_RETURN) continue; Branch (124:17): [True: 0, False: 0] Branch (124:50): [True: 0, False: 0]
125		// Create the CTxIn that can be used to spend this output.
126	0	g_spend_candidate_txins.push_back(GetSpendingScript(*tx, vout_index));
127	0	}
128	0	}
129	0	}
130
131		/**
132		* Read the ChainState object into g_blocks.
133		* Then fill g_spend_candidate_txins with inputs that can be tried by the target.
134		*/
135		static void LoadCurrentChain()
136	0	{
137		// Clear existing data.
138	0	g_blocks.clear();
139	0	g_existing_block_hashes.clear();
140	0	g_spend_candidate_txins.clear();
141
142	0	{
143	0	LOCK(::cs_main);
144		// Retrieve the current chainstate.
145	0	auto& chainstate = Assert(g_setup->m_node.chainman)->ActiveChainstate();
146		// Make sure it contains a valid mempool.
147	0	Assert(chainstate.GetMempool());
148
149		// Traverse the chain from tip to genesis.
150	0	auto current_block = chainstate.m_chain.Tip();
151
152	0	while (current_block != nullptr) { Branch (152:16): [True: 0, False: 0]
153	0	LoadCurrentBlock(chainstate, current_block);
154		// Move to previous block.
155	0	current_block = current_block->pprev;
156	0	}
157	0	}
158
159		// Reverse the order of g_spend_candidate_txins to have them in ascending order of
160		// block height.
161	0	std::reverse(g_spend_candidate_txins.begin(), g_spend_candidate_txins.end());
162	0	}
163
164
165		/**
166		* Reset the chainman in the testing setup object.
167		* Mine 2*COINBASE_MATURITY blocks to have spendable UTXOs.
168		* It is called once in the initialization function.
169		*/
170		void ResetChainman(TestingSetup& setup)
171	0	{
172	0	SetMockTime(setup.m_node.chainman->GetParams().GenesisBlock().Time());
173	0	setup.m_node.chainman.reset();
174	0	setup.m_node.notifications->m_shutdown_on_fatal_error = false;
175	0	setup.m_make_chainman();
176	0	setup.LoadVerifyActivateChainstate();
177
178	0	for (int i = 0; i < 2 * COINBASE_MATURITY; i++) { Branch (178:21): [True: 0, False: 0]
179	0	node::BlockCreateOptions options;
180	0	options.coinbase_output_script = P2WSH_OP_TRUE;
181	0	MineBlock(setup.m_node, options);
182	0	}
183	0	setup.m_node.validation_signals->SyncWithValidationInterfaceQueue();
184	0	}
185
186		/** Create additional transactions in the mempool that spend
187		* coins from mature blocks. Otherwise the mined chain only contains
188		* coinbase transactions.
189		*/
190		void AddExtraTxsToMempool(TestingSetup& setup)
191	0	{
192	0	Assert(Assert(Assert(setup.m_node.chainman)->ActiveChainstate().GetMempool())->size() == 0);
193	0	for (size_t i = 1; i <= 10; i++) { Branch (193:24): [True: 0, False: 0]
194	0	CMutableTransaction ctx;
195	0	ctx.version = CTransaction::CURRENT_VERSION;
196	0	ctx.vin.resize(1);
197		// CTxIn is spendable as g_spend_candidate_txins comes from early blocks whose
198		// coinbases are mature.
199	0	ctx.vin[0] = g_spend_candidate_txins[i];
200	0	ctx.vout.resize(4);
201		// Arbitrarily create various outputs of different kinds in the same tx.
202		// P2WSH
203	0	ctx.vout[0].nValue = CAmount(15 * COIN);
204	0	ctx.vout[0].scriptPubKey = P2WSH_OP_TRUE;
205		// P2SH
206	0	ctx.vout[1].nValue = CAmount(15 * COIN);
207	0	ctx.vout[1].scriptPubKey = P2SH_OP_TRUE;
208		// Taproot
209	0	ctx.vout[2].nValue = CAmount(10 * COIN);
210	0	ctx.vout[2].scriptPubKey = TAPROOT_OP_TRUE;
211		// Empty script
212	0	ctx.vout[3].nValue = CAmount(10 * COIN);
213	0	ctx.vout[3].scriptPubKey = CScript();
214
215	0	LOCK(::cs_main);
216		// Add transaction to the mempool.
217	0	const MempoolAcceptResult ctx_result = setup.m_node.chainman->ProcessTransaction(MakeTransactionRef(ctx));
218	0	Assert(ctx_result.m_result_type == MempoolAcceptResult::ResultType::VALID);
219
220	0	Assert(setup.m_node.chainman->ActiveChainstate().GetMempool()->size() == i);
221		// Force the mempool to select this transaction even though its fee is zero.
222	0	setup.m_node.chainman->ActiveChainstate().GetMempool()->PrioritiseTransaction(ctx.GetHash(), COIN);
223	0	}
224	0	}
225
226		/** Initialize the chain for this target. */
227		static void initialize_connect_block()
228	0	{
229		// Instantiate REGTEST chain.
230	0	static auto testing_setup = MakeNoLogFileContext<TestingSetup>(
231	0	/chain_type=/ChainType::REGTEST, TestOpts{
232	0	.extra_args = {
233	0	"-minrelaytxfee=0",
234	0	"-acceptnonstdtxn",
235	0	},
236	0	});
237	0	g_setup = testing_setup.get();
238
239		// Reset the chainman in the testing setup object.
240	0	ResetChainman(*g_setup);
241
242		// Initialize Taproot script declared as static variables.
243	0	InitTaprootScript();
244
245		// Load the chain mined in ResetChainman in global variables g_blocks and
246		// g_spend_candidate_txins, to make them available to pick by the target.
247	0	LoadCurrentChain();
248
249		// Prepare multiple transactions for block 201. They spend coins
250		// from various coinbases that are now mature enough.
251	0	AddExtraTxsToMempool(*g_setup);
252		// Mine block 201, which contains the transactions added to the mempool.
253	0	node::BlockCreateOptions options;
254	0	options.coinbase_output_script = P2WSH_OP_TRUE;
255	0	MineBlock(g_setup->m_node, options);
256	0	Assert(g_setup->m_node.chainman->ActiveChainstate().GetMempool()->size() == 0);
257
258		// Load the 201th block into g_blocks.
259	0	LOCK(::cs_main);
260	0	auto& chainstate = Assert(g_setup->m_node.chainman)->ActiveChainstate();
261	0	auto current_block = chainstate.m_chain.Tip();
262	0	LoadCurrentBlock(chainstate, current_block);
263	0	}
264
265		/**
266		* Read one transaction from the fuzzing input through the FuzzedDataProvider.
267		* It is intended to leave more space to craft complex transactions, especially
268		* with various script types (P2SH, P2WSH, TAPROOT, NOSCRIPT).
269		* It is exclusively used by ConsumeBlock to read transactions inside a block.
270		*/
271		CTransactionRef ConsumeTransaction(FuzzedDataProvider& fuzzed_data_provider,
272		std::vector<CTxIn>& additional_txins,
273		bool coinbase = false,
274		int target_height = 0)
275	10.0k	{
276	10.0k	CMutableTransaction tx;
277	10.0k	tx.version = fuzzed_data_provider.ConsumeBool() ? Branch (277:18): [True: 6.61k, False: 3.41k]
278	6.61k	CTransaction::CURRENT_VERSION :
279	10.0k	fuzzed_data_provider.ConsumeIntegral<uint32_t>();
280	10.0k	tx.nLockTime = fuzzed_data_provider.ConsumeBool() ? Branch (280:20): [True: 5.92k, False: 4.09k]
281	5.92k	0 :
282	10.0k	fuzzed_data_provider.ConsumeIntegral<uint32_t>();
283
284		// Some harnesses want to explicitly read coinbase transactions from input.
285	10.0k	if (coinbase) { Branch (285:9): [True: 3.86k, False: 6.15k]
286		// vin size is hardcoded.
287	3.86k	tx.vin.resize(1);
288	3.86k	tx.vin[0].prevout.SetNull();
289	3.86k	tx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL;
290	3.86k	if (fuzzed_data_provider.ConsumeBool()) { Branch (290:13): [True: 3.54k, False: 321]
291		// 1/2 probability of a valid vin.
292	3.54k	tx.vin[0].scriptSig = CScript() << target_height;
293	3.54k	} else {
294		// Read arbitrary data from input as scriptSig.
295	321	auto script_sig = ConsumeRandomLengthByteVector<unsigned char>(fuzzed_data_provider, 100);
296	321	tx.vin[0].scriptSig.assign(script_sig.begin(), script_sig.end());
297	321	}
298	6.15k	} else {
299		// Read a normal transaction, with up to 10 inputs.
300	6.15k	int num_inputs = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 10);
301	6.15k	tx.vin.resize(num_inputs);
302	18.9k	for (int i = 0; i < num_inputs; i++) { Branch (302:25): [True: 12.8k, False: 6.15k]
303		// Read an integer to choose a CTxIn or reuse one generated by the
304		// input. The content of the CTxIn is not read from the input per se.
305	12.8k	uint32_t input_index = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(0, g_spend_candidate_txins.size() + additional_txins.size() - 1);
306	12.8k	if (input_index < g_spend_candidate_txins.size()) { Branch (306:17): [True: 12.1k, False: 646]
307		// Pick it from the spend candidates.
308	12.1k	tx.vin[i] = g_spend_candidate_txins[input_index];
309	12.1k	} else {
310		// Pick it in the additional_txins set.
311	646	Assert((input_index - g_spend_candidate_txins.size()) < additional_txins.size());
312	646	tx.vin[i] = additional_txins[input_index - g_spend_candidate_txins.size()];
313	646	}
314
315		// Enable the fuzzer to mutate every CTxIn field after it is taken
316		// from the spend candidates.
317	12.8k	if (fuzzed_data_provider.ConsumeBool()) { Branch (317:17): [True: 3.94k, False: 8.88k]
318	3.94k	tx.vin[i].nSequence = ConsumeSequence(fuzzed_data_provider);
319	3.94k	}
320	12.8k	if (fuzzed_data_provider.ConsumeBool()) { Branch (320:17): [True: 2.87k, False: 9.95k]
321	2.87k	tx.vin[i].prevout.n = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
322	2.87k	}
323	12.8k	if (fuzzed_data_provider.ConsumeBool()) { Branch (323:17): [True: 2.28k, False: 10.5k]
324	2.28k	tx.vin[i].prevout.hash = Txid::FromUint256(ConsumeUInt256(fuzzed_data_provider));
325	2.28k	}
326	12.8k	if (fuzzed_data_provider.ConsumeBool()) { Branch (326:17): [True: 4.77k, False: 8.06k]
327	4.77k	tx.vin[i].scriptSig = ConsumeScript(fuzzed_data_provider);
328	4.77k	}
329	12.8k	if (fuzzed_data_provider.ConsumeBool()) { Branch (329:17): [True: 1.64k, False: 11.1k]
330	1.64k	tx.vin[i].scriptWitness.stack.clear();
331	1.64k	int num_wit = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 10);
332	7.20k	for (int j = 0; j < num_wit; j++) { Branch (332:33): [True: 5.56k, False: 1.64k]
333	5.56k	tx.vin[i].scriptWitness.stack.push_back(ConsumeRandomLengthByteVector<unsigned char>(fuzzed_data_provider, 100));
334	5.56k	}
335	1.64k	}
336	12.8k	}
337	6.15k	}
338
339		// Read outputs.
340	10.0k	int num_outputs = fuzzed_data_provider.ConsumeIntegralInRange<int>(1, 10);
341	10.0k	tx.vout.resize(num_outputs);
342	34.0k	for (int i = 0; i < num_outputs; i++) { Branch (342:21): [True: 24.0k, False: 10.0k]
343		// Read CAmount to spend.
344	24.0k	tx.vout[i].nValue = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-10, 50 * COIN + 10);
345
346		// Read scriptPubKey type into one of the valid types.
347	24.0k	switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 4)) {
348	9.26k	case 0: Branch (348:9): [True: 9.26k, False: 14.7k]
349		// P2WSH
350	9.26k	tx.vout[i].scriptPubKey = P2WSH_OP_TRUE;
351	9.26k	break;
352	3.73k	case 1: Branch (352:9): [True: 3.73k, False: 20.3k]
353		// P2SH
354	3.73k	tx.vout[i].scriptPubKey = P2SH_OP_TRUE;
355	3.73k	break;
356	2.86k	case 2: Branch (356:9): [True: 2.86k, False: 21.1k]
357		// Taproot
358	2.86k	tx.vout[i].scriptPubKey = TAPROOT_OP_TRUE;
359	2.86k	break;
360	2.22k	case 3: Branch (360:9): [True: 2.22k, False: 21.8k]
361		// Empty script
362	2.22k	tx.vout[i].scriptPubKey = CScript();
363	2.22k	break;
364	5.96k	default: { Branch (364:9): [True: 5.96k, False: 18.0k]
365		// Read arbitrary scriptPubKey.
366	5.96k	tx.vout[i].scriptPubKey = ConsumeScript(fuzzed_data_provider);
367	5.96k	break;
368	0	}
369	24.0k	}
370	24.0k	}
371
372		// Create the shared pointer to the CTransaction object.
373	10.0k	auto res = MakeTransactionRef(tx);
374
375	10.0k	if (!coinbase) { Branch (375:9): [True: 6.15k, False: 3.86k]
376		// Create spending scripts for all CTxOuts so they can be spent in later
377		// transactions. Do it here as the transaction hash is definitive.
378	20.2k	for (int i = 0; i < num_outputs; i++) { Branch (378:25): [True: 14.1k, False: 6.15k]
379	14.1k	additional_txins.emplace_back(GetSpendingScript(*res, i));
380	14.1k	}
381	6.15k	}
382
383	10.0k	return res;
384	10.0k	}
385
386		/**
387		* Consume a block from the fuzzing input.
388		* It builds a block on top of the given prev_block.
389		*/
390		CBlock ConsumeBlock(FuzzedDataProvider& fuzzed_data_provider, const CBlock& prev_block, int target_height,
391		std::vector<CTxIn>& additional_txins)
392	3.86k	{
393	3.86k	CBlock block;
394
395		// Initialize header fields.
396	3.86k	block.nVersion = g_blocks.back()->nVersion;
397	3.86k	block.hashPrevBlock = prev_block.GetHash();
398	3.86k	block.nTime = g_blocks.back()->nTime + 2;
399	3.86k	block.nBits = g_blocks.back()->nBits;
400
401		// Give the fuzzer input the ability to mutate block header fields.
402	3.86k	if (fuzzed_data_provider.ConsumeBool()) { Branch (402:9): [True: 275, False: 3.59k]
403	275	block.nVersion = fuzzed_data_provider.ConsumeIntegral<int32_t>();
404	275	}
405	3.86k	if (fuzzed_data_provider.ConsumeBool()) { Branch (405:9): [True: 386, False: 3.48k]
406	386	block.hashPrevBlock = ConsumeUInt256(fuzzed_data_provider);
407	386	}
408
409	3.86k	if (fuzzed_data_provider.ConsumeBool()) { Branch (409:9): [True: 311, False: 3.55k]
410	311	block.nTime = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
411	311	}
412	3.86k	if (fuzzed_data_provider.ConsumeBool()) { Branch (412:9): [True: 433, False: 3.43k]
413	433	block.nBits = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
414	433	}
415
416		// Read the coinbase transaction from the input.
417	3.86k	block.vtx.push_back(ConsumeTransaction(fuzzed_data_provider, additional_txins, true, target_height));
418
419		// Read up to num_tx transactions from the input.
420	3.86k	int num_tx = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 5);
421	10.0k	for (int i = 0; i < num_tx; i++) { Branch (421:21): [True: 6.15k, False: 3.86k]
422	6.15k	block.vtx.push_back(ConsumeTransaction(fuzzed_data_provider, additional_txins));
423	6.15k	}
424
425		// Commit witness.
426	3.86k	if (num_tx > 0) { Branch (426:9): [True: 3.28k, False: 587]
427	3.28k	g_setup->m_node.chainman->GenerateCoinbaseCommitment(block, nullptr);
428	3.28k	}
429
430		// Set hashMerkleRoot to expected value.
431	3.86k	block.hashMerkleRoot = BlockMerkleRoot(block);
432		// Let the fuzzer mutate hashMerkleRoot.
433	3.86k	if (fuzzed_data_provider.ConsumeBool()) { Branch (433:9): [True: 841, False: 3.02k]
434	841	block.hashMerkleRoot = ConsumeUInt256(fuzzed_data_provider);
435	841	}
436
437		// Read the nonce from the input and avoid reusing a setup block hash.
438	3.86k	block.nNonce = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
439	3.86k	while (g_existing_block_hashes.contains(block.GetHash())) { Branch (439:12): [True: 0, False: 3.86k]
440	0	++block.nNonce;
441	0	}
442
443	3.86k	return block;
444	3.86k	}
445
446
447		FUZZ_TARGET(connect_block, .init = initialize_connect_block)
448	3.86k	{
449	3.86k	SeedRandomStateForTest(SeedRand::ZEROS);
450	3.86k	FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
451	3.86k	FakeNodeClock clock{g_blocks.back()->Time() + 2s};
452
453	3.86k	LOCK(::cs_main);
454	3.86k	Chainstate& active_chainstate = g_setup->m_node.chainman->ActiveChainstate();
455	3.86k	CBlockIndex* active_tip = active_chainstate.m_chain.Tip();
456	3.86k	Assert(active_tip->GetBlockHash() == g_blocks.back()->GetHash());
457	3.86k	CCoinsViewCache active_coins(&active_chainstate.CoinsTip());
458
459		// Read a new block from the data provider.
460	3.86k	std::vector<CTxIn> additional_txins;
461	3.86k	CBlock block = ConsumeBlock(fuzzed_data_provider, *g_blocks.back(), active_tip->nHeight + 1, additional_txins);
462
463		// Compute new CBlockIndex object.
464	3.86k	uint256 current_hash = block.GetHash();
465	3.86k	CBlockIndex new_index(block);
466	3.86k	new_index.pprev = active_tip;
467	3.86k	new_index.nHeight = active_tip->nHeight + 1;
468	3.86k	new_index.phashBlock = &current_hash;
469
470		// Try to connect the block.
471	3.86k	BlockValidationState state;
472	3.86k	bool connected = active_chainstate.ConnectBlock(block,
473	3.86k	state,
474	3.86k	&new_index,
475	3.86k	active_coins,
476	3.86k	/fJustCheck=/true);
477	3.86k	Assert(connected == state.IsValid());
478	3.86k	}
479
480		} // namespace