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tests: refactor versionbits fuzz test
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Test `VersionBitsConditionChecker` behaviour directly, rather than
reimplementing it, thus slightly improving fuzz test coverage of the
real code.
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@ajtowns
ajtowns committed Sep 2, 2024
1 parent 7df5185 commit 0bdc31c
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Showing 2 changed files with 68 additions and 83 deletions.
144 changes: 62 additions & 82 deletions src/test/fuzz/versionbits.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,43 +21,22 @@
#include <vector>

namespace {
class TestConditionChecker : public AbstractThresholdConditionChecker
class TestConditionChecker : public VersionBitsConditionChecker
{
private:
mutable ThresholdConditionCache m_cache;

public:
const int64_t m_begin;
const int64_t m_end;
const int m_period;
const int m_threshold;
const int m_min_activation_height;
const int m_bit;

TestConditionChecker(int64_t begin, int64_t end, int period, int threshold, int min_activation_height, int bit)
: m_begin{begin}, m_end{end}, m_period{period}, m_threshold{threshold}, m_min_activation_height{min_activation_height}, m_bit{bit}
TestConditionChecker(const Consensus::BIP9Deployment& dep) : VersionBitsConditionChecker{dep}
{
assert(m_period > 0);
assert(0 <= m_threshold && m_threshold <= m_period);
assert(0 <= m_bit && m_bit < 32 && m_bit < VERSIONBITS_NUM_BITS);
assert(0 <= m_min_activation_height);
assert(dep.period > 0);
assert(dep.threshold <= dep.period);
assert(0 <= dep.bit && dep.bit < 32 && dep.bit < VERSIONBITS_NUM_BITS);
assert(0 <= dep.min_activation_height);
}

bool Condition(const CBlockIndex* pindex) const override { return Condition(pindex->nVersion); }
int64_t BeginTime() const override { return m_begin; }
int64_t EndTime() const override { return m_end; }
int Period() const override { return m_period; }
int Threshold() const override { return m_threshold; }
int MinActivationHeight() const override { return m_min_activation_height; }

ThresholdState GetStateFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateFor(pindexPrev, m_cache); }
int GetStateSinceHeightFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateSinceHeightFor(pindexPrev, m_cache); }

bool Condition(int32_t version) const
{
uint32_t mask = (uint32_t{1}) << m_bit;
return (((version & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) && (version & mask) != 0);
}
};

/** Track blocks mined for test */
Expand Down Expand Up @@ -122,9 +101,6 @@ FUZZ_TARGET(versionbits, .init = initialize)
const size_t max_periods = 16;
const size_t max_blocks = 2 * period * max_periods;

const uint32_t threshold = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(1, period);
assert(0 < threshold && threshold <= period); // must be able to both pass and fail threshold!

// too many blocks at 10min each might cause uint32_t time to overflow if
// block_start_time is at the end of the range above
assert(std::numeric_limits<uint32_t>::max() - MAX_START_TIME > interval * max_blocks);
Expand All @@ -134,53 +110,57 @@ FUZZ_TARGET(versionbits, .init = initialize)
// what values for version will we use to signal / not signal?
const int32_t ver_signal = fuzzed_data_provider.ConsumeIntegral<int32_t>();
const int32_t ver_nosignal = fuzzed_data_provider.ConsumeIntegral<int32_t>();
if (ver_nosignal < 0) return; // negative values are uninteresting

// select deployment parameters: bit, start time, timeout
const int bit = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, VERSIONBITS_NUM_BITS - 1);

bool always_active_test = false;
bool never_active_test = false;
int64_t start_time;
int64_t timeout;
if (fuzzed_data_provider.ConsumeBool()) {
// pick the timestamp to switch based on a block
// note states will change *after* these blocks because mediantime lags
int start_block = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * (max_periods - 3));
int end_block = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * (max_periods - 3));

start_time = block_start_time + start_block * interval;
timeout = block_start_time + end_block * interval;

// allow for times to not exactly match a block
if (fuzzed_data_provider.ConsumeBool()) start_time += interval / 2;
if (fuzzed_data_provider.ConsumeBool()) timeout += interval / 2;
} else {
if (fuzzed_data_provider.ConsumeBool()) {
start_time = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
always_active_test = true;
// Now that we have chosen time and versions, setup to mine blocks
Blocks blocks(block_start_time, interval, ver_signal, ver_nosignal);

const bool always_active_test = fuzzed_data_provider.ConsumeBool();
const bool never_active_test = !always_active_test && fuzzed_data_provider.ConsumeBool();

const Consensus::BIP9Deployment dep{[&]() {
Consensus::BIP9Deployment dep;
dep.period = period;

dep.threshold = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(1, period);
assert(0 < dep.threshold && dep.threshold <= dep.period); // must be able to both pass and fail threshold!

// select deployment parameters: bit, start time, timeout
dep.bit = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, VERSIONBITS_NUM_BITS - 1);

if (always_active_test) {
dep.nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
dep.nTimeout = fuzzed_data_provider.ConsumeBool() ? Consensus::BIP9Deployment::NO_TIMEOUT : fuzzed_data_provider.ConsumeIntegral<int64_t>();
} else if (never_active_test) {
dep.nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
dep.nTimeout = fuzzed_data_provider.ConsumeBool() ? Consensus::BIP9Deployment::NO_TIMEOUT : fuzzed_data_provider.ConsumeIntegral<int64_t>();
} else {
start_time = Consensus::BIP9Deployment::NEVER_ACTIVE;
never_active_test = true;
}
timeout = fuzzed_data_provider.ConsumeBool() ? Consensus::BIP9Deployment::NO_TIMEOUT : fuzzed_data_provider.ConsumeIntegral<int64_t>();
}
int min_activation = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * max_periods);
// pick the timestamp to switch based on a block
// note states will change *after* these blocks because mediantime lags
int start_block = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * (max_periods - 3));
int end_block = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * (max_periods - 3));

TestConditionChecker checker(start_time, timeout, period, threshold, min_activation, bit);
dep.nStartTime = block_start_time + start_block * interval;
dep.nTimeout = block_start_time + end_block * interval;

// allow for times to not exactly match a block
if (fuzzed_data_provider.ConsumeBool()) dep.nStartTime += interval / 2;
if (fuzzed_data_provider.ConsumeBool()) dep.nTimeout += interval / 2;
}
dep.min_activation_height = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * max_periods);
return dep;
}()};
TestConditionChecker checker(dep);

// Early exit if the versions don't signal sensibly for the deployment
if (!checker.Condition(ver_signal)) return;
if (checker.Condition(ver_nosignal)) return;
if (ver_nosignal < 0) return;

// TOP_BITS should ensure version will be positive and meet min
// version requirement
assert(ver_signal > 0);
assert(ver_signal >= VERSIONBITS_LAST_OLD_BLOCK_VERSION);

// Now that we have chosen time and versions, setup to mine blocks
Blocks blocks(block_start_time, interval, ver_signal, ver_nosignal);

/* Strategy:
* * we will mine a final period worth of blocks, with
* randomised signalling according to a mask
Expand Down Expand Up @@ -222,9 +202,9 @@ FUZZ_TARGET(versionbits, .init = initialize)
// get statistics from end of previous period, then reset
BIP9Stats last_stats;
last_stats.period = period;
last_stats.threshold = threshold;
last_stats.threshold = dep.threshold;
last_stats.count = last_stats.elapsed = 0;
last_stats.possible = (period >= threshold);
last_stats.possible = (period >= dep.threshold);
std::vector<bool> last_signals{};

int prev_next_height = (prev == nullptr ? 0 : prev->nHeight + 1);
Expand All @@ -238,7 +218,7 @@ FUZZ_TARGET(versionbits, .init = initialize)
CBlockIndex* current_block = blocks.mine_block(signal);

// verify that signalling attempt was interpreted correctly
assert(checker.Condition(current_block) == signal);
assert(checker.Condition(current_block->nVersion) == signal);

// state and since don't change within the period
const ThresholdState state = checker.GetStateFor(current_block);
Expand All @@ -255,10 +235,10 @@ FUZZ_TARGET(versionbits, .init = initialize)
&& stats.possible == stats_no_signals.possible);

assert(stats.period == period);
assert(stats.threshold == threshold);
assert(stats.threshold == dep.threshold);
assert(stats.elapsed == b);
assert(stats.count == last_stats.count + (signal ? 1 : 0));
assert(stats.possible == (stats.count + period >= stats.elapsed + threshold));
assert(stats.possible == (stats.count + period >= stats.elapsed + dep.threshold));
last_stats = stats;

assert(signals.size() == last_signals.size() + 1);
Expand All @@ -269,21 +249,21 @@ FUZZ_TARGET(versionbits, .init = initialize)

if (exp_state == ThresholdState::STARTED) {
// double check that stats.possible is sane
if (blocks_sig >= threshold - 1) assert(last_stats.possible);
if (blocks_sig >= dep.threshold - 1) assert(last_stats.possible);
}

// mine the final block
bool signal = (signalling_mask >> (period % 32)) & 1;
if (signal) ++blocks_sig;
CBlockIndex* current_block = blocks.mine_block(signal);
assert(checker.Condition(current_block) == signal);
assert(checker.Condition(current_block->nVersion) == signal);

const BIP9Stats stats = checker.GetStateStatisticsFor(current_block);
assert(stats.period == period);
assert(stats.threshold == threshold);
assert(stats.threshold == dep.threshold);
assert(stats.elapsed == period);
assert(stats.count == blocks_sig);
assert(stats.possible == (stats.count + period >= stats.elapsed + threshold));
assert(stats.possible == (stats.count + period >= stats.elapsed + dep.threshold));

// More interesting is whether the state changed.
const ThresholdState state = checker.GetStateFor(current_block);
Expand All @@ -303,33 +283,33 @@ FUZZ_TARGET(versionbits, .init = initialize)
case ThresholdState::DEFINED:
assert(since == 0);
assert(exp_state == ThresholdState::DEFINED);
assert(current_block->GetMedianTimePast() < checker.m_begin);
assert(current_block->GetMedianTimePast() < dep.nStartTime);
break;
case ThresholdState::STARTED:
assert(current_block->GetMedianTimePast() >= checker.m_begin);
assert(current_block->GetMedianTimePast() >= dep.nStartTime);
if (exp_state == ThresholdState::STARTED) {
assert(blocks_sig < threshold);
assert(current_block->GetMedianTimePast() < checker.m_end);
assert(blocks_sig < dep.threshold);
assert(current_block->GetMedianTimePast() < dep.nTimeout);
} else {
assert(exp_state == ThresholdState::DEFINED);
}
break;
case ThresholdState::LOCKED_IN:
if (exp_state == ThresholdState::LOCKED_IN) {
assert(current_block->nHeight + 1 < min_activation);
assert(current_block->nHeight + 1 < dep.min_activation_height);
} else {
assert(exp_state == ThresholdState::STARTED);
assert(blocks_sig >= threshold);
assert(blocks_sig >= dep.threshold);
}
break;
case ThresholdState::ACTIVE:
assert(always_active_test || min_activation <= current_block->nHeight + 1);
assert(always_active_test || dep.min_activation_height <= current_block->nHeight + 1);
assert(exp_state == ThresholdState::ACTIVE || exp_state == ThresholdState::LOCKED_IN);
break;
case ThresholdState::FAILED:
assert(never_active_test || current_block->GetMedianTimePast() >= checker.m_end);
assert(never_active_test || current_block->GetMedianTimePast() >= dep.nTimeout);
if (exp_state == ThresholdState::STARTED) {
assert(blocks_sig < threshold);
assert(blocks_sig < dep.threshold);
} else {
assert(exp_state == ThresholdState::FAILED);
}
Expand Down
7 changes: 6 additions & 1 deletion src/versionbits_impl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -70,14 +70,19 @@ class VersionBitsConditionChecker : public AbstractThresholdConditionChecker {

bool Condition(const CBlockIndex* pindex) const override
{
return (((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) && (pindex->nVersion & Mask()) != 0);
return Condition(pindex->nVersion);
}

public:
explicit VersionBitsConditionChecker(const Consensus::BIP9Deployment& dep) : dep{dep} {}
explicit VersionBitsConditionChecker(const Consensus::Params& params, Consensus::DeploymentPos id) : VersionBitsConditionChecker{params.vDeployments[id]} {}

uint32_t Mask() const { return (uint32_t{1}) << dep.bit; }

bool Condition(int32_t nVersion) const
{
return (((nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) && (nVersion & Mask()) != 0);
}
};

#endif // BITCOIN_VERSIONBITS_IMPL_H

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