From 1639c3b76c3f2b74606f62ecd3ca725154e27f1b Mon Sep 17 00:00:00 2001 From: Anthony Towns Date: Tue, 16 Mar 2021 18:35:45 +1000 Subject: tests: Add fuzzing harness for versionbits --- src/test/fuzz/versionbits.cpp | 345 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 345 insertions(+) create mode 100644 src/test/fuzz/versionbits.cpp (limited to 'src/test/fuzz') diff --git a/src/test/fuzz/versionbits.cpp b/src/test/fuzz/versionbits.cpp new file mode 100644 index 0000000000..a898e2782d --- /dev/null +++ b/src/test/fuzz/versionbits.cpp @@ -0,0 +1,345 @@ +// Copyright (c) 2020-2021 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 +#include +#include +#include +#include + +#include +#include +#include + +#include +#include +#include +#include + +namespace { +class TestConditionChecker : public AbstractThresholdConditionChecker +{ +private: + mutable ThresholdConditionCache m_cache; + const Consensus::Params dummy_params{}; + +public: + const int64_t m_begin = 0; + const int64_t m_end = 0; + const int m_period = 0; + const int m_threshold = 0; + const int m_bit = 0; + + TestConditionChecker(int64_t begin, int64_t end, int period, int threshold, int bit) + : m_begin{begin}, m_end{end}, m_period{period}, m_threshold{threshold}, m_bit{bit} + { + assert(m_period > 0); + assert(0 <= m_threshold && m_threshold <= m_period); + assert(0 <= m_bit && m_bit <= 32 && m_bit < VERSIONBITS_NUM_BITS); + } + + bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const override { return Condition(pindex->nVersion); } + int64_t BeginTime(const Consensus::Params& params) const override { return m_begin; } + int64_t EndTime(const Consensus::Params& params) const override { return m_end; } + int Period(const Consensus::Params& params) const override { return m_period; } + int Threshold(const Consensus::Params& params) const override { return m_threshold; } + + ThresholdState GetStateFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateFor(pindexPrev, dummy_params, m_cache); } + int GetStateSinceHeightFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateSinceHeightFor(pindexPrev, dummy_params, m_cache); } + BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateStatisticsFor(pindexPrev, dummy_params); } + + bool Condition(int64_t version) const + { + return ((version >> m_bit) & 1) != 0 && (version & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS; + } + + bool Condition(const CBlockIndex* pindex) const { return Condition(pindex->nVersion); } +}; + +/** Track blocks mined for test */ +class Blocks +{ +private: + std::vector> m_blocks; + const uint32_t m_start_time; + const uint32_t m_interval; + const int32_t m_signal; + const int32_t m_no_signal; + +public: + Blocks(uint32_t start_time, uint32_t interval, int32_t signal, int32_t no_signal) + : m_start_time{start_time}, m_interval{interval}, m_signal{signal}, m_no_signal{no_signal} {} + + size_t size() const { return m_blocks.size(); } + + CBlockIndex* tip() const + { + return m_blocks.empty() ? nullptr : m_blocks.back().get(); + } + + CBlockIndex* mine_block(bool signal) + { + CBlockHeader header; + header.nVersion = signal ? m_signal : m_no_signal; + header.nTime = m_start_time + m_blocks.size() * m_interval; + header.nBits = 0x1d00ffff; + + auto current_block = std::make_unique(header); + current_block->pprev = tip(); + current_block->nHeight = m_blocks.size(); + current_block->BuildSkip(); + + return m_blocks.emplace_back(std::move(current_block)).get(); + } +}; + +void initialize() +{ + SelectParams(CBaseChainParams::MAIN); +} +} // namespace + +constexpr uint32_t MAX_TIME = 4102444800; // 2100-01-01 + +FUZZ_TARGET_INIT(versionbits, initialize) +{ + const CChainParams& params = Params(); + + const int64_t interval = params.GetConsensus().nPowTargetSpacing; + assert(interval > 1); // need to be able to halve it + assert(interval < std::numeric_limits::max()); + + FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size()); + + // making period/max_periods larger slows these tests down significantly + const int period = 32; + const size_t max_periods = 16; + const size_t max_blocks = 2 * period * max_periods; + + const int threshold = fuzzed_data_provider.ConsumeIntegralInRange(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::max() - MAX_TIME > interval * max_blocks); + + const int64_t block_start_time = fuzzed_data_provider.ConsumeIntegralInRange(params.GenesisBlock().nTime, MAX_TIME); + + // what values for version will we use to signal / not signal? + const int32_t ver_signal = fuzzed_data_provider.ConsumeIntegral(); + const int32_t ver_nosignal = fuzzed_data_provider.ConsumeIntegral(); + + // select deployment parameters: bit, start time, timeout + const int bit = fuzzed_data_provider.ConsumeIntegralInRange(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(0, period * (max_periods - 3)); + int end_block = fuzzed_data_provider.ConsumeIntegralInRange(start_block, period * (max_periods - 3)); + + start_time = block_start_time + start_block * interval; + timeout = block_start_time + end_block * interval; + + assert(start_time <= timeout); + + // 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; + + // this may make timeout too early; if so, don't run the test + if (start_time > timeout) return; + } else { + if (fuzzed_data_provider.ConsumeBool()) { + start_time = Consensus::BIP9Deployment::ALWAYS_ACTIVE; + timeout = Consensus::BIP9Deployment::NO_TIMEOUT; + always_active_test = true; + } else { + start_time = 1199145601; // January 1, 2008 + timeout = 1230767999; // December 31, 2008 + never_active_test = true; + } + } + + TestConditionChecker checker(start_time, timeout, period, threshold, bit); + + // 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 + assert(ver_signal > 0); + + // 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 + * * but before we mine those blocks, we will mine some + * randomised number of prior periods; with either all + * or no blocks in the period signalling + * + * We establish the mask first, then consume "bools" until + * we run out of fuzz data to work out how many prior periods + * there are and which ones will signal. + */ + + // establish the mask + const uint32_t signalling_mask = fuzzed_data_provider.ConsumeIntegral(); + + // mine prior periods + while (fuzzed_data_provider.remaining_bytes() > 0) { + // all blocks in these periods either do or don't signal + bool signal = fuzzed_data_provider.ConsumeBool(); + for (int b = 0; b < period; ++b) { + blocks.mine_block(signal); + } + + // don't risk exceeding max_blocks or times may wrap around + if (blocks.size() + period*2 > max_blocks) break; + } + // NOTE: fuzzed_data_provider may be fully consumed at this point and should not be used further + + // now we mine the final period and check that everything looks sane + + // count the number of signalling blocks + int blocks_sig = 0; + + // get the info for the first block of the period + CBlockIndex* prev = blocks.tip(); + const int exp_since = checker.GetStateSinceHeightFor(prev); + const ThresholdState exp_state = checker.GetStateFor(prev); + BIP9Stats last_stats = checker.GetStateStatisticsFor(prev); + + int prev_next_height = (prev == nullptr ? 0 : prev->nHeight + 1); + assert(exp_since <= prev_next_height); + + // mine (period-1) blocks and check state + for (int b = 1; b < period; ++b) { + const bool signal = (signalling_mask >> (b % 32)) & 1; + if (signal) ++blocks_sig; + + CBlockIndex* current_block = blocks.mine_block(signal); + + // verify that signalling attempt was interpreted correctly + assert(checker.Condition(current_block) == signal); + + // state and since don't change within the period + const ThresholdState state = checker.GetStateFor(current_block); + const int since = checker.GetStateSinceHeightFor(current_block); + assert(state == exp_state); + assert(since == exp_since); + + // GetStateStatistics may crash when state is not STARTED + if (state != ThresholdState::STARTED) continue; + + // check that after mining this block stats change as expected + const BIP9Stats stats = checker.GetStateStatisticsFor(current_block); + assert(stats.period == period); + assert(stats.threshold == threshold); + assert(stats.elapsed == b); + assert(stats.count == last_stats.count + (signal ? 1 : 0)); + assert(stats.possible == (stats.count + period >= stats.elapsed + threshold)); + last_stats = stats; + } + + if (exp_state == ThresholdState::STARTED) { + // double check that stats.possible is sane + if (blocks_sig >= 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); + + // GetStateStatistics is safe on a period boundary + // and has progressed to a new period + const BIP9Stats stats = checker.GetStateStatisticsFor(current_block); + assert(stats.period == period); + assert(stats.threshold == threshold); + assert(stats.elapsed == 0); + assert(stats.count == 0); + assert(stats.possible == true); + + // More interesting is whether the state changed. + const ThresholdState state = checker.GetStateFor(current_block); + const int since = checker.GetStateSinceHeightFor(current_block); + + // since is straightforward: + assert(since % period == 0); + assert(0 <= since && since <= current_block->nHeight + 1); + if (state == exp_state) { + assert(since == exp_since); + } else { + assert(since == current_block->nHeight + 1); + } + + // state is where everything interesting is + switch (state) { + case ThresholdState::DEFINED: + assert(since == 0); + assert(exp_state == ThresholdState::DEFINED); + assert(current_block->GetMedianTimePast() < checker.m_begin); + assert(current_block->GetMedianTimePast() < checker.m_end); + break; + case ThresholdState::STARTED: + assert(current_block->GetMedianTimePast() >= checker.m_begin); + assert(current_block->GetMedianTimePast() < checker.m_end); + if (exp_state == ThresholdState::STARTED) { + assert(blocks_sig < threshold); + } else { + assert(exp_state == ThresholdState::DEFINED); + } + break; + case ThresholdState::LOCKED_IN: + assert(exp_state == ThresholdState::STARTED); + assert(current_block->GetMedianTimePast() < checker.m_end); + assert(blocks_sig >= threshold); + break; + case ThresholdState::ACTIVE: + assert(exp_state == ThresholdState::ACTIVE || exp_state == ThresholdState::LOCKED_IN); + break; + case ThresholdState::FAILED: + assert(current_block->GetMedianTimePast() >= checker.m_end); + assert(exp_state != ThresholdState::LOCKED_IN && exp_state != ThresholdState::ACTIVE); + break; + default: + assert(false); + } + + if (blocks.size() >= max_periods * period) { + // we chose the timeout (and block times) so that by the time we have this many blocks it's all over + assert(state == ThresholdState::ACTIVE || state == ThresholdState::FAILED); + } + + // "always active" has additional restrictions + if (always_active_test) { + assert(state == ThresholdState::ACTIVE); + assert(exp_state == ThresholdState::ACTIVE); + assert(since == 0); + } else { + // except for always active, the initial state is always DEFINED + assert(since > 0 || state == ThresholdState::DEFINED); + assert(exp_since > 0 || exp_state == ThresholdState::DEFINED); + } + + // "never active" does too + if (never_active_test) { + assert(state == ThresholdState::FAILED); + assert(since == period); + if (exp_since == 0) { + assert(exp_state == ThresholdState::DEFINED); + } else { + assert(exp_state == ThresholdState::FAILED); + } + } +} -- cgit v1.2.3