bitcoin/src/test/fuzz/util.h

// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_TEST_FUZZ_UTIL_H
#define BITCOIN_TEST_FUZZ_UTIL_H

#include <amount.h>
#include <arith_uint256.h>
#include <attributes.h>
#include <chainparamsbase.h>
#include <coins.h>
#include <consensus/consensus.h>
#include <merkleblock.h>
#include <net.h>
#include <netaddress.h>
#include <netbase.h>
#include <primitives/transaction.h>
#include <script/script.h>
#include <script/standard.h>
#include <serialize.h>
#include <streams.h>
#include <test/fuzz/FuzzedDataProvider.h>
#include <test/fuzz/fuzz.h>
#include <test/util/net.h>
#include <test/util/setup_common.h>
#include <txmempool.h>
#include <uint256.h>
#include <util/time.h>
#include <version.h>

#include <algorithm>
#include <cstdint>
#include <cstdio>
#include <optional>
#include <string>
#include <vector>

template <typename... Callables>
void CallOneOf(FuzzedDataProvider& fuzzed_data_provider, Callables... callables)
{
    constexpr size_t call_size{sizeof...(callables)};
    static_assert(call_size >= 1);
    const size_t call_index{fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, call_size - 1)};

    size_t i{0};
    return ((i++ == call_index ? callables() : void()), ...);
}

[[nodiscard]] inline std::vector<uint8_t> ConsumeRandomLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const size_t max_length = 4096) noexcept
{
    const std::string s = fuzzed_data_provider.ConsumeRandomLengthString(max_length);
    return {s.begin(), s.end()};
}

[[nodiscard]] inline std::vector<bool> ConsumeRandomLengthBitVector(FuzzedDataProvider& fuzzed_data_provider, const size_t max_length = 4096) noexcept
{
    return BytesToBits(ConsumeRandomLengthByteVector(fuzzed_data_provider, max_length));
}

[[nodiscard]] inline CDataStream ConsumeDataStream(FuzzedDataProvider& fuzzed_data_provider, const size_t max_length = 4096) noexcept
{
    return {ConsumeRandomLengthByteVector(fuzzed_data_provider, max_length), SER_NETWORK, INIT_PROTO_VERSION};
}

[[nodiscard]] inline std::vector<std::string> ConsumeRandomLengthStringVector(FuzzedDataProvider& fuzzed_data_provider, const size_t max_vector_size = 16, const size_t max_string_length = 16) noexcept
{
    const size_t n_elements = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, max_vector_size);
    std::vector<std::string> r;
    for (size_t i = 0; i < n_elements; ++i) {
        r.push_back(fuzzed_data_provider.ConsumeRandomLengthString(max_string_length));
    }
    return r;
}

template <typename T>
[[nodiscard]] inline std::vector<T> ConsumeRandomLengthIntegralVector(FuzzedDataProvider& fuzzed_data_provider, const size_t max_vector_size = 16) noexcept
{
    const size_t n_elements = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, max_vector_size);
    std::vector<T> r;
    for (size_t i = 0; i < n_elements; ++i) {
        r.push_back(fuzzed_data_provider.ConsumeIntegral<T>());
    }
    return r;
}

template <typename T>
[[nodiscard]] inline std::optional<T> ConsumeDeserializable(FuzzedDataProvider& fuzzed_data_provider, const size_t max_length = 4096) noexcept
{
    const std::vector<uint8_t> buffer = ConsumeRandomLengthByteVector(fuzzed_data_provider, max_length);
    CDataStream ds{buffer, SER_NETWORK, INIT_PROTO_VERSION};
    T obj;
    try {
        ds >> obj;
    } catch (const std::ios_base::failure&) {
        return std::nullopt;
    }
    return obj;
}

template <typename WeakEnumType, size_t size>
[[nodiscard]] WeakEnumType ConsumeWeakEnum(FuzzedDataProvider& fuzzed_data_provider, const WeakEnumType (&all_types)[size]) noexcept
{
    return fuzzed_data_provider.ConsumeBool() ?
               fuzzed_data_provider.PickValueInArray<WeakEnumType>(all_types) :
               WeakEnumType(fuzzed_data_provider.ConsumeIntegral<typename std::underlying_type<WeakEnumType>::type>());
}

[[nodiscard]] inline opcodetype ConsumeOpcodeType(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return static_cast<opcodetype>(fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(0, MAX_OPCODE));
}

[[nodiscard]] inline CAmount ConsumeMoney(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(0, MAX_MONEY);
}

[[nodiscard]] inline int64_t ConsumeTime(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    // Avoid t=0 (1970-01-01T00:00:00Z) since SetMockTime(0) is a no-op.
    static const int64_t time_min = ParseISO8601DateTime("1970-01-01T00:00:01Z");
    static const int64_t time_max = ParseISO8601DateTime("9999-12-31T23:59:59Z");
    return fuzzed_data_provider.ConsumeIntegralInRange<int64_t>(time_min, time_max);
}

[[nodiscard]] inline CScript ConsumeScript(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    const std::vector<uint8_t> b = ConsumeRandomLengthByteVector(fuzzed_data_provider);
    return {b.begin(), b.end()};
}

[[nodiscard]] inline CScriptNum ConsumeScriptNum(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return CScriptNum{fuzzed_data_provider.ConsumeIntegral<int64_t>()};
}

[[nodiscard]] inline uint160 ConsumeUInt160(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    const std::vector<uint8_t> v160 = fuzzed_data_provider.ConsumeBytes<uint8_t>(160 / 8);
    if (v160.size() != 160 / 8) {
        return {};
    }
    return uint160{v160};
}

[[nodiscard]] inline uint256 ConsumeUInt256(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    const std::vector<uint8_t> v256 = fuzzed_data_provider.ConsumeBytes<uint8_t>(256 / 8);
    if (v256.size() != 256 / 8) {
        return {};
    }
    return uint256{v256};
}

[[nodiscard]] inline arith_uint256 ConsumeArithUInt256(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return UintToArith256(ConsumeUInt256(fuzzed_data_provider));
}

[[nodiscard]] inline CTxMemPoolEntry ConsumeTxMemPoolEntry(FuzzedDataProvider& fuzzed_data_provider, const CTransaction& tx) noexcept
{
    // Avoid:
    // policy/feerate.cpp:28:34: runtime error: signed integer overflow: 34873208148477500 * 1000 cannot be represented in type 'long'
    //
    // Reproduce using CFeeRate(348732081484775, 10).GetFeePerK()
    const CAmount fee = std::min<CAmount>(ConsumeMoney(fuzzed_data_provider), std::numeric_limits<CAmount>::max() / static_cast<CAmount>(100000));
    assert(MoneyRange(fee));
    const int64_t time = fuzzed_data_provider.ConsumeIntegral<int64_t>();
    const unsigned int entry_height = fuzzed_data_provider.ConsumeIntegral<unsigned int>();
    const bool spends_coinbase = fuzzed_data_provider.ConsumeBool();
    const unsigned int sig_op_cost = fuzzed_data_provider.ConsumeIntegralInRange<unsigned int>(0, MAX_BLOCK_SIGOPS_COST);
    return CTxMemPoolEntry{MakeTransactionRef(tx), fee, time, entry_height, spends_coinbase, sig_op_cost, {}};
}

[[nodiscard]] inline CTxDestination ConsumeTxDestination(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    CTxDestination tx_destination;
    CallOneOf(
        fuzzed_data_provider,
        [&] {
            tx_destination = CNoDestination{};
        },
        [&] {
            tx_destination = PKHash{ConsumeUInt160(fuzzed_data_provider)};
        },
        [&] {
            tx_destination = ScriptHash{ConsumeUInt160(fuzzed_data_provider)};
        },
        [&] {
            tx_destination = WitnessV0ScriptHash{ConsumeUInt256(fuzzed_data_provider)};
        },
        [&] {
            tx_destination = WitnessV0KeyHash{ConsumeUInt160(fuzzed_data_provider)};
        },
        [&] {
            WitnessUnknown witness_unknown{};
            witness_unknown.version = fuzzed_data_provider.ConsumeIntegral<int>();
            const std::vector<uint8_t> witness_unknown_program_1 = fuzzed_data_provider.ConsumeBytes<uint8_t>(40);
            witness_unknown.length = witness_unknown_program_1.size();
            std::copy(witness_unknown_program_1.begin(), witness_unknown_program_1.end(), witness_unknown.program);
            tx_destination = witness_unknown;
        });
    return tx_destination;
}

template <typename T>
[[nodiscard]] bool MultiplicationOverflow(const T i, const T j) noexcept
{
    static_assert(std::is_integral<T>::value, "Integral required.");
    if (std::numeric_limits<T>::is_signed) {
        if (i > 0) {
            if (j > 0) {
                return i > (std::numeric_limits<T>::max() / j);
            } else {
                return j < (std::numeric_limits<T>::min() / i);
            }
        } else {
            if (j > 0) {
                return i < (std::numeric_limits<T>::min() / j);
            } else {
                return i != 0 && (j < (std::numeric_limits<T>::max() / i));
            }
        }
    } else {
        return j != 0 && i > std::numeric_limits<T>::max() / j;
    }
}

template <class T>
[[nodiscard]] bool AdditionOverflow(const T i, const T j) noexcept
{
    static_assert(std::is_integral<T>::value, "Integral required.");
    if (std::numeric_limits<T>::is_signed) {
        return (i > 0 && j > std::numeric_limits<T>::max() - i) ||
               (i < 0 && j < std::numeric_limits<T>::min() - i);
    }
    return std::numeric_limits<T>::max() - i < j;
}

[[nodiscard]] inline bool ContainsSpentInput(const CTransaction& tx, const CCoinsViewCache& inputs) noexcept
{
    for (const CTxIn& tx_in : tx.vin) {
        const Coin& coin = inputs.AccessCoin(tx_in.prevout);
        if (coin.IsSpent()) {
            return true;
        }
    }
    return false;
}

/**
 * Returns a byte vector of specified size regardless of the number of remaining bytes available
 * from the fuzzer. Pads with zero value bytes if needed to achieve the specified size.
 */
[[nodiscard]] inline std::vector<uint8_t> ConsumeFixedLengthByteVector(FuzzedDataProvider& fuzzed_data_provider, const size_t length) noexcept
{
    std::vector<uint8_t> result(length);
    const std::vector<uint8_t> random_bytes = fuzzed_data_provider.ConsumeBytes<uint8_t>(length);
    if (!random_bytes.empty()) {
        std::memcpy(result.data(), random_bytes.data(), random_bytes.size());
    }
    return result;
}

inline CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    const Network network = fuzzed_data_provider.PickValueInArray({Network::NET_IPV4, Network::NET_IPV6, Network::NET_INTERNAL, Network::NET_ONION});
    CNetAddr net_addr;
    if (network == Network::NET_IPV4) {
        const in_addr v4_addr = {
            .s_addr = fuzzed_data_provider.ConsumeIntegral<uint32_t>()};
        net_addr = CNetAddr{v4_addr};
    } else if (network == Network::NET_IPV6) {
        if (fuzzed_data_provider.remaining_bytes() >= 16) {
            in6_addr v6_addr = {};
            memcpy(v6_addr.s6_addr, fuzzed_data_provider.ConsumeBytes<uint8_t>(16).data(), 16);
            net_addr = CNetAddr{v6_addr, fuzzed_data_provider.ConsumeIntegral<uint32_t>()};
        }
    } else if (network == Network::NET_INTERNAL) {
        net_addr.SetInternal(fuzzed_data_provider.ConsumeBytesAsString(32));
    } else if (network == Network::NET_ONION) {
        net_addr.SetSpecial(fuzzed_data_provider.ConsumeBytesAsString(32));
    }
    return net_addr;
}

inline CSubNet ConsumeSubNet(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return {ConsumeNetAddr(fuzzed_data_provider), fuzzed_data_provider.ConsumeIntegral<uint8_t>()};
}

inline CService ConsumeService(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return {ConsumeNetAddr(fuzzed_data_provider), fuzzed_data_provider.ConsumeIntegral<uint16_t>()};
}

inline CAddress ConsumeAddress(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return {ConsumeService(fuzzed_data_provider), ConsumeWeakEnum(fuzzed_data_provider, ALL_SERVICE_FLAGS), fuzzed_data_provider.ConsumeIntegral<uint32_t>()};
}

template <bool ReturnUniquePtr = false>
auto ConsumeNode(FuzzedDataProvider& fuzzed_data_provider, const std::optional<NodeId>& node_id_in = std::nullopt) noexcept
{
    const NodeId node_id = node_id_in.value_or(fuzzed_data_provider.ConsumeIntegral<NodeId>());
    const ServiceFlags local_services = ConsumeWeakEnum(fuzzed_data_provider, ALL_SERVICE_FLAGS);
    const SOCKET socket = INVALID_SOCKET;
    const CAddress address = ConsumeAddress(fuzzed_data_provider);
    const uint64_t keyed_net_group = fuzzed_data_provider.ConsumeIntegral<uint64_t>();
    const uint64_t local_host_nonce = fuzzed_data_provider.ConsumeIntegral<uint64_t>();
    const CAddress addr_bind = ConsumeAddress(fuzzed_data_provider);
    const std::string addr_name = fuzzed_data_provider.ConsumeRandomLengthString(64);
    const ConnectionType conn_type = fuzzed_data_provider.PickValueInArray(ALL_CONNECTION_TYPES);
    const bool inbound_onion{conn_type == ConnectionType::INBOUND ? fuzzed_data_provider.ConsumeBool() : false};
    if constexpr (ReturnUniquePtr) {
        return std::make_unique<CNode>(node_id, local_services, socket, address, keyed_net_group, local_host_nonce, addr_bind, addr_name, conn_type, inbound_onion);
    } else {
        return CNode{node_id, local_services, socket, address, keyed_net_group, local_host_nonce, addr_bind, addr_name, conn_type, inbound_onion};
    }
}
inline std::unique_ptr<CNode> ConsumeNodeAsUniquePtr(FuzzedDataProvider& fdp, const std::optional<NodeId>& node_id_in = nullopt) { return ConsumeNode<true>(fdp, node_id_in); }

inline void FillNode(FuzzedDataProvider& fuzzed_data_provider, CNode& node, const std::optional<int32_t>& version_in = std::nullopt) noexcept
{
    const ServiceFlags remote_services = ConsumeWeakEnum(fuzzed_data_provider, ALL_SERVICE_FLAGS);
    const NetPermissionFlags permission_flags = ConsumeWeakEnum(fuzzed_data_provider, ALL_NET_PERMISSION_FLAGS);
    const int32_t version = version_in.value_or(fuzzed_data_provider.ConsumeIntegral<int32_t>());
    const bool filter_txs = fuzzed_data_provider.ConsumeBool();

    node.nServices = remote_services;
    node.m_permissionFlags = permission_flags;
    node.nVersion = version;
    node.SetCommonVersion(version);
    if (node.m_tx_relay != nullptr) {
        LOCK(node.m_tx_relay->cs_filter);
        node.m_tx_relay->fRelayTxes = filter_txs;
    }
}

inline void InitializeFuzzingContext(const std::string& chain_name = CBaseChainParams::REGTEST)
{
    static const BasicTestingSetup basic_testing_setup{chain_name, {"-nodebuglogfile"}};
}

class FuzzedFileProvider
{
    FuzzedDataProvider& m_fuzzed_data_provider;
    int64_t m_offset = 0;

public:
    FuzzedFileProvider(FuzzedDataProvider& fuzzed_data_provider) : m_fuzzed_data_provider{fuzzed_data_provider}
    {
    }

    FILE* open()
    {
        if (m_fuzzed_data_provider.ConsumeBool()) {
            return nullptr;
        }
        std::string mode;
        CallOneOf(
            m_fuzzed_data_provider,
            [&] {
                mode = "r";
            },
            [&] {
                mode = "r+";
            },
            [&] {
                mode = "w";
            },
            [&] {
                mode = "w+";
            },
            [&] {
                mode = "a";
            },
            [&] {
                mode = "a+";
            });
#ifdef _GNU_SOURCE
        const cookie_io_functions_t io_hooks = {
            FuzzedFileProvider::read,
            FuzzedFileProvider::write,
            FuzzedFileProvider::seek,
            FuzzedFileProvider::close,
        };
        return fopencookie(this, mode.c_str(), io_hooks);
#else
        (void)mode;
        return nullptr;
#endif
    }

    static ssize_t read(void* cookie, char* buf, size_t size)
    {
        FuzzedFileProvider* fuzzed_file = (FuzzedFileProvider*)cookie;
        if (buf == nullptr || size == 0 || fuzzed_file->m_fuzzed_data_provider.ConsumeBool()) {
            return fuzzed_file->m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
        }
        const std::vector<uint8_t> random_bytes = fuzzed_file->m_fuzzed_data_provider.ConsumeBytes<uint8_t>(size);
        if (random_bytes.empty()) {
            return 0;
        }
        std::memcpy(buf, random_bytes.data(), random_bytes.size());
        if (AdditionOverflow(fuzzed_file->m_offset, (int64_t)random_bytes.size())) {
            return fuzzed_file->m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
        }
        fuzzed_file->m_offset += random_bytes.size();
        return random_bytes.size();
    }

    static ssize_t write(void* cookie, const char* buf, size_t size)
    {
        FuzzedFileProvider* fuzzed_file = (FuzzedFileProvider*)cookie;
        const ssize_t n = fuzzed_file->m_fuzzed_data_provider.ConsumeIntegralInRange<ssize_t>(0, size);
        if (AdditionOverflow(fuzzed_file->m_offset, (int64_t)n)) {
            return fuzzed_file->m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
        }
        fuzzed_file->m_offset += n;
        return n;
    }

    static int seek(void* cookie, int64_t* offset, int whence)
    {
        assert(whence == SEEK_SET || whence == SEEK_CUR); // SEEK_END not implemented yet.
        FuzzedFileProvider* fuzzed_file = (FuzzedFileProvider*)cookie;
        int64_t new_offset = 0;
        if (whence == SEEK_SET) {
            new_offset = *offset;
        } else if (whence == SEEK_CUR) {
            if (AdditionOverflow(fuzzed_file->m_offset, *offset)) {
                return -1;
            }
            new_offset = fuzzed_file->m_offset + *offset;
        }
        if (new_offset < 0) {
            return -1;
        }
        fuzzed_file->m_offset = new_offset;
        *offset = new_offset;
        return fuzzed_file->m_fuzzed_data_provider.ConsumeIntegralInRange<int>(-1, 0);
    }

    static int close(void* cookie)
    {
        FuzzedFileProvider* fuzzed_file = (FuzzedFileProvider*)cookie;
        return fuzzed_file->m_fuzzed_data_provider.ConsumeIntegralInRange<int>(-1, 0);
    }
};

[[nodiscard]] inline FuzzedFileProvider ConsumeFile(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return {fuzzed_data_provider};
}

class FuzzedAutoFileProvider
{
    FuzzedDataProvider& m_fuzzed_data_provider;
    FuzzedFileProvider m_fuzzed_file_provider;

public:
    FuzzedAutoFileProvider(FuzzedDataProvider& fuzzed_data_provider) : m_fuzzed_data_provider{fuzzed_data_provider}, m_fuzzed_file_provider{fuzzed_data_provider}
    {
    }

    CAutoFile open()
    {
        return {m_fuzzed_file_provider.open(), m_fuzzed_data_provider.ConsumeIntegral<int>(), m_fuzzed_data_provider.ConsumeIntegral<int>()};
    }
};

[[nodiscard]] inline FuzzedAutoFileProvider ConsumeAutoFile(FuzzedDataProvider& fuzzed_data_provider) noexcept
{
    return {fuzzed_data_provider};
}

#define WRITE_TO_STREAM_CASE(type, consume) \
    [&] {                                   \
        type o = consume;                   \
        stream << o;                        \
    }
template <typename Stream>
void WriteToStream(FuzzedDataProvider& fuzzed_data_provider, Stream& stream) noexcept
{
    while (fuzzed_data_provider.ConsumeBool()) {
        try {
            CallOneOf(
                fuzzed_data_provider,
                WRITE_TO_STREAM_CASE(bool, fuzzed_data_provider.ConsumeBool()),
                WRITE_TO_STREAM_CASE(char, fuzzed_data_provider.ConsumeIntegral<char>()),
                WRITE_TO_STREAM_CASE(int8_t, fuzzed_data_provider.ConsumeIntegral<int8_t>()),
                WRITE_TO_STREAM_CASE(uint8_t, fuzzed_data_provider.ConsumeIntegral<uint8_t>()),
                WRITE_TO_STREAM_CASE(int16_t, fuzzed_data_provider.ConsumeIntegral<int16_t>()),
                WRITE_TO_STREAM_CASE(uint16_t, fuzzed_data_provider.ConsumeIntegral<uint16_t>()),
                WRITE_TO_STREAM_CASE(int32_t, fuzzed_data_provider.ConsumeIntegral<int32_t>()),
                WRITE_TO_STREAM_CASE(uint32_t, fuzzed_data_provider.ConsumeIntegral<uint32_t>()),
                WRITE_TO_STREAM_CASE(int64_t, fuzzed_data_provider.ConsumeIntegral<int64_t>()),
                WRITE_TO_STREAM_CASE(uint64_t, fuzzed_data_provider.ConsumeIntegral<uint64_t>()),
                WRITE_TO_STREAM_CASE(float, fuzzed_data_provider.ConsumeFloatingPoint<float>()),
                WRITE_TO_STREAM_CASE(double, fuzzed_data_provider.ConsumeFloatingPoint<double>()),
                WRITE_TO_STREAM_CASE(std::string, fuzzed_data_provider.ConsumeRandomLengthString(32)),
                WRITE_TO_STREAM_CASE(std::vector<char>, ConsumeRandomLengthIntegralVector<char>(fuzzed_data_provider)));
        } catch (const std::ios_base::failure&) {
            break;
        }
    }
}

#define READ_FROM_STREAM_CASE(type) \
    [&] {                           \
        type o;                     \
        stream >> o;                \
    }
template <typename Stream>
void ReadFromStream(FuzzedDataProvider& fuzzed_data_provider, Stream& stream) noexcept
{
    while (fuzzed_data_provider.ConsumeBool()) {
        try {
            CallOneOf(
                fuzzed_data_provider,
                READ_FROM_STREAM_CASE(bool),
                READ_FROM_STREAM_CASE(char),
                READ_FROM_STREAM_CASE(int8_t),
                READ_FROM_STREAM_CASE(uint8_t),
                READ_FROM_STREAM_CASE(int16_t),
                READ_FROM_STREAM_CASE(uint16_t),
                READ_FROM_STREAM_CASE(int32_t),
                READ_FROM_STREAM_CASE(uint32_t),
                READ_FROM_STREAM_CASE(int64_t),
                READ_FROM_STREAM_CASE(uint64_t),
                READ_FROM_STREAM_CASE(float),
                READ_FROM_STREAM_CASE(double),
                READ_FROM_STREAM_CASE(std::string),
                READ_FROM_STREAM_CASE(std::vector<char>));
        } catch (const std::ios_base::failure&) {
            break;
        }
    }
}

#endif // BITCOIN_TEST_FUZZ_UTIL_H