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bitcoin/src/test/fuzz/coinscache_sim.cpp

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// Copyright (c) 2023 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 <coins.h>
#include <crypto/sha256.h>
#include <primitives/transaction.h>
#include <test/fuzz/fuzz.h>
#include <test/fuzz/FuzzedDataProvider.h>
#include <test/fuzz/util.h>
#include <assert.h>
#include <optional>
#include <memory>
#include <stdint.h>
#include <vector>
namespace {
/** Number of distinct COutPoint values used in this test. */
constexpr uint32_t NUM_OUTPOINTS = 256;
/** Number of distinct Coin values used in this test (ignoring nHeight). */
constexpr uint32_t NUM_COINS = 256;
/** Maximum number CCoinsViewCache objects used in this test. */
constexpr uint32_t MAX_CACHES = 4;
/** Data type large enough to hold NUM_COINS-1. */
using coinidx_type = uint8_t;
struct PrecomputedData
{
//! Randomly generated COutPoint values.
COutPoint outpoints[NUM_OUTPOINTS];
//! Randomly generated Coin values.
Coin coins[NUM_COINS];
PrecomputedData()
{
static const uint8_t PREFIX_O[1] = {'o'}; /** Hash prefix for outpoint hashes. */
static const uint8_t PREFIX_S[1] = {'s'}; /** Hash prefix for coins scriptPubKeys. */
static const uint8_t PREFIX_M[1] = {'m'}; /** Hash prefix for coins nValue/fCoinBase. */
for (uint32_t i = 0; i < NUM_OUTPOINTS; ++i) {
uint32_t idx = (i * 1200U) >> 12; /* Map 3 or 4 entries to same txid. */
const uint8_t ser[4] = {uint8_t(idx), uint8_t(idx >> 8), uint8_t(idx >> 16), uint8_t(idx >> 24)};
uint256 txid;
CSHA256().Write(PREFIX_O, 1).Write(ser, sizeof(ser)).Finalize(txid.begin());
outpoints[i].hash = Txid::FromUint256(txid);
outpoints[i].n = i;
}
for (uint32_t i = 0; i < NUM_COINS; ++i) {
const uint8_t ser[4] = {uint8_t(i), uint8_t(i >> 8), uint8_t(i >> 16), uint8_t(i >> 24)};
uint256 hash;
CSHA256().Write(PREFIX_S, 1).Write(ser, sizeof(ser)).Finalize(hash.begin());
/* Convert hash to scriptPubkeys (of different lengths, so SanityCheck's cached memory
* usage check has a chance to detect mismatches). */
switch (i % 5U) {
case 0: /* P2PKH */
coins[i].out.scriptPubKey.resize(25);
coins[i].out.scriptPubKey[0] = OP_DUP;
coins[i].out.scriptPubKey[1] = OP_HASH160;
coins[i].out.scriptPubKey[2] = 20;
std::copy(hash.begin(), hash.begin() + 20, coins[i].out.scriptPubKey.begin() + 3);
coins[i].out.scriptPubKey[23] = OP_EQUALVERIFY;
coins[i].out.scriptPubKey[24] = OP_CHECKSIG;
break;
case 1: /* P2SH */
coins[i].out.scriptPubKey.resize(23);
coins[i].out.scriptPubKey[0] = OP_HASH160;
coins[i].out.scriptPubKey[1] = 20;
std::copy(hash.begin(), hash.begin() + 20, coins[i].out.scriptPubKey.begin() + 2);
coins[i].out.scriptPubKey[12] = OP_EQUAL;
break;
case 2: /* P2WPKH */
coins[i].out.scriptPubKey.resize(22);
coins[i].out.scriptPubKey[0] = OP_0;
coins[i].out.scriptPubKey[1] = 20;
std::copy(hash.begin(), hash.begin() + 20, coins[i].out.scriptPubKey.begin() + 2);
break;
case 3: /* P2WSH */
coins[i].out.scriptPubKey.resize(34);
coins[i].out.scriptPubKey[0] = OP_0;
coins[i].out.scriptPubKey[1] = 32;
std::copy(hash.begin(), hash.begin() + 32, coins[i].out.scriptPubKey.begin() + 2);
break;
case 4: /* P2TR */
coins[i].out.scriptPubKey.resize(34);
coins[i].out.scriptPubKey[0] = OP_1;
coins[i].out.scriptPubKey[1] = 32;
std::copy(hash.begin(), hash.begin() + 32, coins[i].out.scriptPubKey.begin() + 2);
break;
}
/* Hash again to construct nValue and fCoinBase. */
CSHA256().Write(PREFIX_M, 1).Write(ser, sizeof(ser)).Finalize(hash.begin());
coins[i].out.nValue = CAmount(hash.GetUint64(0) % MAX_MONEY);
coins[i].fCoinBase = (hash.GetUint64(1) & 7) == 0;
coins[i].nHeight = 0; /* Real nHeight used in simulation is set dynamically. */
}
}
};
enum class EntryType : uint8_t
{
/* This entry in the cache does not exist (so we'd have to look in the parent cache). */
NONE,
/* This entry in the cache corresponds to an unspent coin. */
UNSPENT,
/* This entry in the cache corresponds to a spent coin. */
SPENT,
};
struct CacheEntry
{
/* Type of entry. */
EntryType entrytype;
/* Index in the coins array this entry corresponds to (only if entrytype == UNSPENT). */
coinidx_type coinidx;
/* nHeight value for this entry (so the coins[coinidx].nHeight value is ignored; only if entrytype == UNSPENT). */
uint32_t height;
};
struct CacheLevel
{
CacheEntry entry[NUM_OUTPOINTS];
void Wipe() {
for (uint32_t i = 0; i < NUM_OUTPOINTS; ++i) {
entry[i].entrytype = EntryType::NONE;
}
}
};
/** Class for the base of the hierarchy (roughly simulating a memory-backed CCoinsViewDB).
*
* The initial state consists of the empty UTXO set, though coins whose output index
* is 3 (mod 5) always have GetCoin() succeed (but returning an IsSpent() coin unless a UTXO
* exists). Coins whose output index is 4 (mod 5) have GetCoin() always succeed after being spent.
* This exercises code paths with spent, non-DIRTY cache entries.
*/
class CoinsViewBottom final : public CCoinsView
{
std::map<COutPoint, Coin> m_data;
public:
bool GetCoin(const COutPoint& outpoint, Coin& coin) const final
{
auto it = m_data.find(outpoint);
if (it == m_data.end()) {
if ((outpoint.n % 5) == 3) {
coin.Clear();
return true;
}
return false;
} else {
coin = it->second;
return true;
}
}
bool HaveCoin(const COutPoint& outpoint) const final
{
return m_data.count(outpoint);
}
uint256 GetBestBlock() const final { return {}; }
std::vector<uint256> GetHeadBlocks() const final { return {}; }
std::unique_ptr<CCoinsViewCursor> Cursor() const final { return {}; }
size_t EstimateSize() const final { return m_data.size(); }
bool BatchWrite(CoinsCachePair *pairs, const uint256&, bool will_erase) final
{
for (auto it{pairs}; it != nullptr; it = it->second.Next(will_erase)) {
if (it->second.GetFlags() & CCoinsCacheEntry::DIRTY) {
if (it->second.coin.IsSpent() && (it->first.n % 5) != 4) {
m_data.erase(it->first);
} else if (will_erase) {
m_data[it->first] = std::move(it->second.coin);
} else {
m_data[it->first] = it->second.coin;
}
} else {
/* For non-dirty entries being written, compare them with what we have. */
auto it2 = m_data.find(it->first);
if (it->second.coin.IsSpent()) {
assert(it2 == m_data.end() || it2->second.IsSpent());
} else {
assert(it2 != m_data.end());
assert(it->second.coin.out == it2->second.out);
assert(it->second.coin.fCoinBase == it2->second.fCoinBase);
assert(it->second.coin.nHeight == it2->second.nHeight);
}
}
}
return true;
}
};
} // namespace
FUZZ_TARGET(coinscache_sim)
{
/** Precomputed COutPoint and CCoins values. */
static const PrecomputedData data;
/** Dummy coinsview instance (base of the hierarchy). */
CoinsViewBottom bottom;
/** Real CCoinsViewCache objects. */
std::vector<std::unique_ptr<CCoinsViewCache>> caches;
/** Simulated cache data (sim_caches[0] matches bottom, sim_caches[i+1] matches caches[i]). */
CacheLevel sim_caches[MAX_CACHES + 1];
/** Current height in the simulation. */
uint32_t current_height = 1U;
// Initialize bottom simulated cache.
sim_caches[0].Wipe();
/** Helper lookup function in the simulated cache stack. */
auto lookup = [&](uint32_t outpointidx, int sim_idx = -1) -> std::optional<std::pair<coinidx_type, uint32_t>> {
uint32_t cache_idx = sim_idx == -1 ? caches.size() : sim_idx;
while (true) {
const auto& entry = sim_caches[cache_idx].entry[outpointidx];
if (entry.entrytype == EntryType::UNSPENT) {
return {{entry.coinidx, entry.height}};
} else if (entry.entrytype == EntryType::SPENT) {
return std::nullopt;
};
if (cache_idx == 0) break;
--cache_idx;
}
return std::nullopt;
};
/** Flush changes in top cache to the one below. */
auto flush = [&]() {
assert(caches.size() >= 1);
auto& cache = sim_caches[caches.size()];
auto& prev_cache = sim_caches[caches.size() - 1];
for (uint32_t outpointidx = 0; outpointidx < NUM_OUTPOINTS; ++outpointidx) {
if (cache.entry[outpointidx].entrytype != EntryType::NONE) {
prev_cache.entry[outpointidx] = cache.entry[outpointidx];
cache.entry[outpointidx].entrytype = EntryType::NONE;
}
}
};
// Main simulation loop: read commands from the fuzzer input, and apply them
// to both the real cache stack and the simulation.
FuzzedDataProvider provider(buffer.data(), buffer.size());
LIMITED_WHILE(provider.remaining_bytes(), 10000) {
// Every operation (except "Change height") moves current height forward,
// so it functions as a kind of epoch, making ~all UTXOs unique.
++current_height;
// Make sure there is always at least one CCoinsViewCache.
if (caches.empty()) {
caches.emplace_back(new CCoinsViewCache(&bottom, /*deterministic=*/true));
sim_caches[caches.size()].Wipe();
}
// Execute command.
CallOneOf(
provider,
[&]() { // GetCoin
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Look up in simulation data.
auto sim = lookup(outpointidx);
// Look up in real caches.
Coin realcoin;
auto real = caches.back()->GetCoin(data.outpoints[outpointidx], realcoin);
// Compare results.
if (!sim.has_value()) {
assert(!real || realcoin.IsSpent());
} else {
assert(real && !realcoin.IsSpent());
const auto& simcoin = data.coins[sim->first];
assert(realcoin.out == simcoin.out);
assert(realcoin.fCoinBase == simcoin.fCoinBase);
assert(realcoin.nHeight == sim->second);
}
},
[&]() { // HaveCoin
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Look up in simulation data.
auto sim = lookup(outpointidx);
// Look up in real caches.
auto real = caches.back()->HaveCoin(data.outpoints[outpointidx]);
// Compare results.
assert(sim.has_value() == real);
},
[&]() { // HaveCoinInCache
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Invoke on real cache (there is no equivalent in simulation, so nothing to compare result with).
(void)caches.back()->HaveCoinInCache(data.outpoints[outpointidx]);
},
[&]() { // AccessCoin
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Look up in simulation data.
auto sim = lookup(outpointidx);
// Look up in real caches.
const auto& realcoin = caches.back()->AccessCoin(data.outpoints[outpointidx]);
// Compare results.
if (!sim.has_value()) {
assert(realcoin.IsSpent());
} else {
assert(!realcoin.IsSpent());
const auto& simcoin = data.coins[sim->first];
assert(simcoin.out == realcoin.out);
assert(simcoin.fCoinBase == realcoin.fCoinBase);
assert(realcoin.nHeight == sim->second);
}
},
[&]() { // AddCoin (only possible_overwrite if necessary)
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
uint32_t coinidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_COINS - 1);
// Look up in simulation data (to know whether we must set possible_overwrite or not).
auto sim = lookup(outpointidx);
// Invoke on real caches.
Coin coin = data.coins[coinidx];
coin.nHeight = current_height;
caches.back()->AddCoin(data.outpoints[outpointidx], std::move(coin), sim.has_value());
// Apply to simulation data.
auto& entry = sim_caches[caches.size()].entry[outpointidx];
entry.entrytype = EntryType::UNSPENT;
entry.coinidx = coinidx;
entry.height = current_height;
},
[&]() { // AddCoin (always possible_overwrite)
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
uint32_t coinidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_COINS - 1);
// Invoke on real caches.
Coin coin = data.coins[coinidx];
coin.nHeight = current_height;
caches.back()->AddCoin(data.outpoints[outpointidx], std::move(coin), true);
// Apply to simulation data.
auto& entry = sim_caches[caches.size()].entry[outpointidx];
entry.entrytype = EntryType::UNSPENT;
entry.coinidx = coinidx;
entry.height = current_height;
},
[&]() { // SpendCoin (moveto = nullptr)
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Invoke on real caches.
caches.back()->SpendCoin(data.outpoints[outpointidx], nullptr);
// Apply to simulation data.
sim_caches[caches.size()].entry[outpointidx].entrytype = EntryType::SPENT;
},
[&]() { // SpendCoin (with moveto)
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Look up in simulation data (to compare the returned *moveto with).
auto sim = lookup(outpointidx);
// Invoke on real caches.
Coin realcoin;
caches.back()->SpendCoin(data.outpoints[outpointidx], &realcoin);
// Apply to simulation data.
sim_caches[caches.size()].entry[outpointidx].entrytype = EntryType::SPENT;
// Compare *moveto with the value expected based on simulation data.
if (!sim.has_value()) {
assert(realcoin.IsSpent());
} else {
assert(!realcoin.IsSpent());
const auto& simcoin = data.coins[sim->first];
assert(simcoin.out == realcoin.out);
assert(simcoin.fCoinBase == realcoin.fCoinBase);
assert(realcoin.nHeight == sim->second);
}
},
[&]() { // Uncache
uint32_t outpointidx = provider.ConsumeIntegralInRange<uint32_t>(0, NUM_OUTPOINTS - 1);
// Apply to real caches (there is no equivalent in our simulation).
caches.back()->Uncache(data.outpoints[outpointidx]);
},
[&]() { // Add a cache level (if not already at the max).
if (caches.size() != MAX_CACHES) {
// Apply to real caches.
caches.emplace_back(new CCoinsViewCache(&*caches.back(), /*deterministic=*/true));
// Apply to simulation data.
sim_caches[caches.size()].Wipe();
}
},
[&]() { // Remove a cache level.
// Apply to real caches (this reduces caches.size(), implicitly doing the same on the simulation data).
caches.back()->SanityCheck();
caches.pop_back();
},
[&]() { // Flush.
// Apply to simulation data.
flush();
// Apply to real caches.
caches.back()->Flush();
},
[&]() { // Sync.
// Apply to simulation data (note that in our simulation, syncing and flushing is the same thing).
flush();
// Apply to real caches.
caches.back()->Sync();
},
[&]() { // Flush + ReallocateCache.
// Apply to simulation data.
flush();
// Apply to real caches.
caches.back()->Flush();
caches.back()->ReallocateCache();
},
[&]() { // GetCacheSize
(void)caches.back()->GetCacheSize();
},
[&]() { // DynamicMemoryUsage
(void)caches.back()->DynamicMemoryUsage();
},
[&]() { // Change height
current_height = provider.ConsumeIntegralInRange<uint32_t>(1, current_height - 1);
}
);
}
// Sanity check all the remaining caches
for (const auto& cache : caches) {
cache->SanityCheck();
}
// Full comparison between caches and simulation data, from bottom to top,
// as AccessCoin on a higher cache may affect caches below it.
for (unsigned sim_idx = 1; sim_idx <= caches.size(); ++sim_idx) {
auto& cache = *caches[sim_idx - 1];
size_t cache_size = 0;
for (uint32_t outpointidx = 0; outpointidx < NUM_OUTPOINTS; ++outpointidx) {
cache_size += cache.HaveCoinInCache(data.outpoints[outpointidx]);
const auto& real = cache.AccessCoin(data.outpoints[outpointidx]);
auto sim = lookup(outpointidx, sim_idx);
if (!sim.has_value()) {
assert(real.IsSpent());
} else {
assert(!real.IsSpent());
assert(real.out == data.coins[sim->first].out);
assert(real.fCoinBase == data.coins[sim->first].fCoinBase);
assert(real.nHeight == sim->second);
}
}
// HaveCoinInCache ignores spent coins, so GetCacheSize() may exceed it. */
assert(cache.GetCacheSize() >= cache_size);
}
// Compare the bottom coinsview (not a CCoinsViewCache) with sim_cache[0].
for (uint32_t outpointidx = 0; outpointidx < NUM_OUTPOINTS; ++outpointidx) {
Coin realcoin;
bool real = bottom.GetCoin(data.outpoints[outpointidx], realcoin);
auto sim = lookup(outpointidx, 0);
if (!sim.has_value()) {
assert(!real || realcoin.IsSpent());
} else {
assert(real && !realcoin.IsSpent());
assert(realcoin.out == data.coins[sim->first].out);
assert(realcoin.fCoinBase == data.coins[sim->first].fCoinBase);
assert(realcoin.nHeight == sim->second);
}
}
}
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