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1 : : // Copyright (c) 2020-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 <chain.h>
6 : : #include <chainparams.h>
7 : : #include <common/args.h>
8 : : #include <consensus/params.h>
9 : : #include <primitives/block.h>
10 : : #include <util/chaintype.h>
11 : : #include <versionbits.h>
12 : : #include <versionbits_impl.h>
13 : :
14 : : #include <test/fuzz/FuzzedDataProvider.h>
15 : : #include <test/fuzz/fuzz.h>
16 : : #include <test/fuzz/util.h>
17 : : #include <test/util/versionbits.h>
18 : :
19 : : #include <cstdint>
20 : : #include <limits>
21 : : #include <memory>
22 : : #include <vector>
23 : :
24 : : namespace {
25 : 254 : class TestConditionChecker : public VersionBitsConditionChecker
26 : : {
27 : : private:
28 : : mutable ThresholdConditionCache m_cache;
29 : :
30 : : public:
31 [ - + ]: 254 : TestConditionChecker(const Consensus::BIP9Deployment& dep) : VersionBitsConditionChecker{dep}
32 : : {
33 [ - + ]: 254 : assert(dep.period > 0);
34 [ - + ]: 254 : assert(dep.threshold <= dep.period);
35 [ - + ]: 254 : assert(0 <= dep.bit && dep.bit < 32 && dep.bit < VERSIONBITS_MAX_NUM_BITS);
36 [ - + ]: 254 : assert(0 <= dep.min_activation_height);
37 : 254 : }
38 : :
39 : 7557 : ThresholdState GetStateFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateFor(pindexPrev, m_cache); }
40 : 7557 : int GetStateSinceHeightFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateSinceHeightFor(pindexPrev, m_cache); }
41 : : };
42 : :
43 : : /** Track blocks mined for test */
44 : 0 : class Blocks
45 : : {
46 : : private:
47 : : std::vector<std::unique_ptr<CBlockIndex>> m_blocks;
48 : : const uint32_t m_start_time;
49 : : const uint32_t m_interval;
50 : : const int32_t m_signal;
51 : : const int32_t m_no_signal;
52 : :
53 : : public:
54 : 254 : Blocks(uint32_t start_time, uint32_t interval, int32_t signal, int32_t no_signal)
55 : 254 : : m_start_time{start_time}, m_interval{interval}, m_signal{signal}, m_no_signal{no_signal} {}
56 : :
57 : 6058 : size_t size() const { return m_blocks.size(); }
58 : :
59 : 97157 : CBlockIndex* tip() const
60 : : {
61 [ + + ]: 97157 : return m_blocks.empty() ? nullptr : m_blocks.back().get();
62 : : }
63 : :
64 : 96928 : CBlockIndex* mine_block(bool signal)
65 : : {
66 : 96928 : CBlockHeader header;
67 [ + + ]: 96928 : header.nVersion = signal ? m_signal : m_no_signal;
68 [ - + ]: 96928 : header.nTime = m_start_time + m_blocks.size() * m_interval;
69 : 96928 : header.nBits = 0x1d00ffff;
70 : :
71 : 96928 : auto current_block = std::make_unique<CBlockIndex>(header);
72 [ - + ]: 96928 : current_block->pprev = tip();
73 [ - + + - ]: 96928 : current_block->nHeight = m_blocks.size();
74 [ + - ]: 96928 : current_block->BuildSkip();
75 : :
76 [ + - ]: 96928 : return m_blocks.emplace_back(std::move(current_block)).get();
77 : 96928 : }
78 : : };
79 : :
80 : : std::unique_ptr<const CChainParams> g_params;
81 : :
82 : 1 : void initialize()
83 : : {
84 : : // this is actually comparatively slow, so only do it once
85 [ + - ]: 2 : g_params = CreateChainParams(ArgsManager{}, ChainType::MAIN);
86 [ - + ]: 1 : assert(g_params != nullptr);
87 : 1 : }
88 : :
89 : : constexpr uint32_t MAX_START_TIME = 4102444800; // 2100-01-01
90 : :
91 [ + - ]: 743 : FUZZ_TARGET(versionbits, .init = initialize)
92 : : {
93 [ - + ]: 277 : const CChainParams& params = *g_params;
94 : 277 : const int64_t interval = params.GetConsensus().nPowTargetSpacing;
95 [ - + ]: 277 : assert(interval > 1); // need to be able to halve it
96 [ - + ]: 277 : assert(interval < std::numeric_limits<int32_t>::max());
97 : :
98 [ - + ]: 277 : FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
99 : :
100 : : // making period/max_periods larger slows these tests down significantly
101 : 277 : const uint32_t period = 32;
102 : 277 : const size_t max_periods = 16;
103 : 277 : const size_t max_blocks = 2 * period * max_periods;
104 : :
105 : : // too many blocks at 10min each might cause uint32_t time to overflow if
106 : : // block_start_time is at the end of the range above
107 [ - + ]: 277 : assert(std::numeric_limits<uint32_t>::max() - MAX_START_TIME > interval * max_blocks);
108 : :
109 : 277 : const int64_t block_start_time = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(params.GenesisBlock().nTime, MAX_START_TIME);
110 : :
111 : : // what values for version will we use to signal / not signal?
112 : 277 : const int32_t ver_signal = fuzzed_data_provider.ConsumeIntegral<int32_t>();
113 : 277 : const int32_t ver_nosignal = fuzzed_data_provider.ConsumeIntegral<int32_t>();
114 [ + + ]: 277 : if (ver_nosignal < 0) return; // negative values are uninteresting
115 : :
116 : : // Now that we have chosen time and versions, setup to mine blocks
117 : 254 : Blocks blocks(block_start_time, interval, ver_signal, ver_nosignal);
118 : :
119 : 254 : const bool always_active_test = fuzzed_data_provider.ConsumeBool();
120 [ + + + + ]: 464 : const bool never_active_test = !always_active_test && fuzzed_data_provider.ConsumeBool();
121 : :
122 : 508 : const Consensus::BIP9Deployment dep{[&]() {
123 : 254 : Consensus::BIP9Deployment dep;
124 : 254 : dep.period = period;
125 : :
126 : 254 : dep.threshold = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(1, period);
127 [ + - - + ]: 254 : assert(0 < dep.threshold && dep.threshold <= dep.period); // must be able to both pass and fail threshold!
128 : :
129 : : // select deployment parameters: bit, start time, timeout
130 : 254 : dep.bit = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, VERSIONBITS_MAX_NUM_BITS - 1);
131 : :
132 [ + + ]: 254 : if (always_active_test) {
133 : 44 : dep.nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
134 [ + + ]: 44 : dep.nTimeout = fuzzed_data_provider.ConsumeBool() ? Consensus::BIP9Deployment::NO_TIMEOUT : fuzzed_data_provider.ConsumeIntegral<int64_t>();
135 [ + + ]: 210 : } else if (never_active_test) {
136 : 11 : dep.nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
137 [ + + ]: 11 : dep.nTimeout = fuzzed_data_provider.ConsumeBool() ? Consensus::BIP9Deployment::NO_TIMEOUT : fuzzed_data_provider.ConsumeIntegral<int64_t>();
138 : : } else {
139 : : // pick the timestamp to switch based on a block
140 : : // note states will change *after* these blocks because mediantime lags
141 : 199 : int start_block = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * (max_periods - 3));
142 : 199 : int end_block = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * (max_periods - 3));
143 : :
144 : 199 : dep.nStartTime = block_start_time + start_block * interval;
145 : 199 : dep.nTimeout = block_start_time + end_block * interval;
146 : :
147 : : // allow for times to not exactly match a block
148 [ + + ]: 199 : if (fuzzed_data_provider.ConsumeBool()) dep.nStartTime += interval / 2;
149 [ + + ]: 199 : if (fuzzed_data_provider.ConsumeBool()) dep.nTimeout += interval / 2;
150 : : }
151 : 254 : dep.min_activation_height = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * max_periods);
152 : 254 : return dep;
153 : 254 : }()};
154 : 254 : TestConditionChecker checker(dep);
155 : :
156 : : // Early exit if the versions don't signal sensibly for the deployment
157 [ + + ]: 254 : if (!checker.Condition(ver_signal)) return;
158 [ + + ]: 258 : if (checker.Condition(ver_nosignal)) return;
159 : :
160 : : // TOP_BITS should ensure version will be positive and meet min
161 : : // version requirement
162 [ - + ]: 229 : assert(ver_signal > 0);
163 [ - + ]: 229 : assert(ver_signal >= VERSIONBITS_LAST_OLD_BLOCK_VERSION);
164 : :
165 : : /* Strategy:
166 : : * * we will mine a final period worth of blocks, with
167 : : * randomised signalling according to a mask
168 : : * * but before we mine those blocks, we will mine some
169 : : * randomised number of prior periods; with either all
170 : : * or no blocks in the period signalling
171 : : *
172 : : * We establish the mask first, then consume "bools" until
173 : : * we run out of fuzz data to work out how many prior periods
174 : : * there are and which ones will signal.
175 : : */
176 : :
177 : : // establish the mask
178 : 229 : const uint32_t signalling_mask = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
179 : :
180 : : // mine prior periods
181 [ + + ]: 3224 : while (fuzzed_data_provider.remaining_bytes() > 0) { // early exit; no need for LIMITED_WHILE
182 : : // all blocks in these periods either do or don't signal
183 : 2800 : bool signal = fuzzed_data_provider.ConsumeBool();
184 [ + + ]: 92400 : for (uint32_t b = 0; b < period; ++b) {
185 [ + - ]: 89600 : blocks.mine_block(signal);
186 : : }
187 : :
188 : : // don't risk exceeding max_blocks or times may wrap around
189 [ - + + + ]: 2800 : if (blocks.size() + 2 * period > max_blocks) break;
190 : : }
191 : : // NOTE: fuzzed_data_provider may be fully consumed at this point and should not be used further
192 : :
193 : : // now we mine the final period and check that everything looks sane
194 : :
195 : : // count the number of signalling blocks
196 : 229 : uint32_t blocks_sig = 0;
197 : :
198 : : // get the info for the first block of the period
199 : 229 : CBlockIndex* prev = blocks.tip();
200 [ + - ]: 229 : const int exp_since = checker.GetStateSinceHeightFor(prev);
201 [ + - ]: 229 : const ThresholdState exp_state = checker.GetStateFor(prev);
202 : :
203 : : // get statistics from end of previous period, then reset
204 : 229 : BIP9Stats last_stats;
205 : 229 : last_stats.period = period;
206 : 229 : last_stats.threshold = dep.threshold;
207 : 229 : last_stats.count = last_stats.elapsed = 0;
208 : 229 : last_stats.possible = (period >= dep.threshold);
209 : 229 : std::vector<bool> last_signals{};
210 : :
211 [ + + ]: 229 : int prev_next_height = (prev == nullptr ? 0 : prev->nHeight + 1);
212 [ - + ]: 229 : assert(exp_since <= prev_next_height);
213 : :
214 : : // mine (period-1) blocks and check state
215 [ + + ]: 7328 : for (uint32_t b = 1; b < period; ++b) {
216 : 7099 : const bool signal = (signalling_mask >> (b % 32)) & 1;
217 [ + + ]: 7099 : if (signal) ++blocks_sig;
218 : :
219 [ + - ]: 7099 : CBlockIndex* current_block = blocks.mine_block(signal);
220 : :
221 : : // verify that signalling attempt was interpreted correctly
222 [ + + - + ]: 10462 : assert(checker.Condition(current_block->nVersion) == signal);
223 : :
224 : : // state and since don't change within the period
225 [ + - ]: 7099 : const ThresholdState state = checker.GetStateFor(current_block);
226 [ + - ]: 7099 : const int since = checker.GetStateSinceHeightFor(current_block);
227 [ - + ]: 7099 : assert(state == exp_state);
228 [ - + ]: 7099 : assert(since == exp_since);
229 : :
230 : : // check that after mining this block stats change as expected
231 : 7099 : std::vector<bool> signals;
232 [ + - ]: 7099 : const BIP9Stats stats = checker.GetStateStatisticsFor(current_block, &signals);
233 [ + - ]: 7099 : const BIP9Stats stats_no_signals = checker.GetStateStatisticsFor(current_block);
234 [ + - + - : 7099 : assert(stats.period == stats_no_signals.period && stats.threshold == stats_no_signals.threshold
+ - + - -
+ ]
235 : : && stats.elapsed == stats_no_signals.elapsed && stats.count == stats_no_signals.count
236 : : && stats.possible == stats_no_signals.possible);
237 : :
238 [ - + ]: 7099 : assert(stats.period == period);
239 [ - + ]: 7099 : assert(stats.threshold == dep.threshold);
240 [ - + ]: 7099 : assert(stats.elapsed == b);
241 [ + + - + ]: 11383 : assert(stats.count == last_stats.count + (signal ? 1 : 0));
242 [ - + ]: 7099 : assert(stats.possible == (stats.count + period >= stats.elapsed + dep.threshold));
243 : 7099 : last_stats = stats;
244 : :
245 [ - + ]: 7099 : assert(signals.size() == last_signals.size() + 1);
246 [ - + ]: 7099 : assert(signals.back() == signal);
247 [ + - ]: 7099 : last_signals.push_back(signal);
248 [ - + ]: 7099 : assert(signals == last_signals);
249 : 7099 : }
250 : :
251 [ + + ]: 229 : if (exp_state == ThresholdState::STARTED) {
252 : : // double check that stats.possible is sane
253 [ + + - + ]: 43 : if (blocks_sig >= dep.threshold - 1) assert(last_stats.possible);
254 : : }
255 : :
256 : : // mine the final block
257 : 229 : bool signal = (signalling_mask >> (period % 32)) & 1;
258 [ + + ]: 229 : if (signal) ++blocks_sig;
259 [ + - ]: 229 : CBlockIndex* current_block = blocks.mine_block(signal);
260 [ + + - + ]: 350 : assert(checker.Condition(current_block->nVersion) == signal);
261 : :
262 [ + - ]: 229 : const BIP9Stats stats = checker.GetStateStatisticsFor(current_block);
263 [ - + ]: 229 : assert(stats.period == period);
264 [ - + ]: 229 : assert(stats.threshold == dep.threshold);
265 [ - + ]: 229 : assert(stats.elapsed == period);
266 [ - + ]: 229 : assert(stats.count == blocks_sig);
267 [ - + ]: 229 : assert(stats.possible == (stats.count + period >= stats.elapsed + dep.threshold));
268 : :
269 : : // More interesting is whether the state changed.
270 [ + - ]: 229 : const ThresholdState state = checker.GetStateFor(current_block);
271 [ + - ]: 229 : const int since = checker.GetStateSinceHeightFor(current_block);
272 : :
273 : : // since is straightforward:
274 [ - + ]: 229 : assert(since % period == 0);
275 [ + - - + ]: 229 : assert(0 <= since && since <= current_block->nHeight + 1);
276 [ + + ]: 229 : if (state == exp_state) {
277 [ - + ]: 176 : assert(since == exp_since);
278 : : } else {
279 [ - + ]: 53 : assert(since == current_block->nHeight + 1);
280 : : }
281 : :
282 : : // state is where everything interesting is
283 : 458 : [&]() {
284 [ + + + + : 229 : switch (state) {
+ - ]
285 : 19 : case ThresholdState::DEFINED:
286 [ - + ]: 19 : assert(since == 0);
287 [ - + ]: 19 : assert(exp_state == ThresholdState::DEFINED);
288 [ - + ]: 19 : assert(current_block->GetMedianTimePast() < dep.nStartTime);
289 : : return;
290 : 30 : case ThresholdState::STARTED:
291 [ - + ]: 30 : assert(current_block->GetMedianTimePast() >= dep.nStartTime);
292 [ + + ]: 30 : if (exp_state == ThresholdState::STARTED) {
293 [ - + ]: 14 : assert(blocks_sig < dep.threshold);
294 [ - + ]: 14 : assert(current_block->GetMedianTimePast() < dep.nTimeout);
295 : : } else {
296 [ - + ]: 16 : assert(exp_state == ThresholdState::DEFINED);
297 : : }
298 : : return;
299 : 25 : case ThresholdState::LOCKED_IN:
300 [ + + ]: 25 : if (exp_state == ThresholdState::LOCKED_IN) {
301 [ - + ]: 5 : assert(current_block->nHeight + 1 < dep.min_activation_height);
302 : : } else {
303 [ - + ]: 20 : assert(exp_state == ThresholdState::STARTED);
304 [ - + ]: 20 : assert(blocks_sig >= dep.threshold);
305 : : }
306 : : return;
307 : 99 : case ThresholdState::ACTIVE:
308 [ + + - + ]: 99 : assert(always_active_test || dep.min_activation_height <= current_block->nHeight + 1);
309 [ - + ]: 99 : assert(exp_state == ThresholdState::ACTIVE || exp_state == ThresholdState::LOCKED_IN);
310 : : return;
311 : 56 : case ThresholdState::FAILED:
312 [ + + - + ]: 56 : assert(never_active_test || current_block->GetMedianTimePast() >= dep.nTimeout);
313 [ + + ]: 56 : if (exp_state == ThresholdState::STARTED) {
314 [ - + ]: 9 : assert(blocks_sig < dep.threshold);
315 : : } else {
316 [ - + ]: 47 : assert(exp_state == ThresholdState::FAILED);
317 : : }
318 : : return;
319 : : } // no default case, so the compiler can warn about missing cases
320 : 0 : assert(false);
321 : 229 : }();
322 : :
323 [ - + + + ]: 229 : if (blocks.size() >= period * max_periods) {
324 : : // we chose the timeout (and block times) so that by the time we have this many blocks it's all over
325 [ - + ]: 88 : assert(state == ThresholdState::ACTIVE || state == ThresholdState::FAILED);
326 : : }
327 : :
328 [ + + ]: 229 : if (always_active_test) {
329 : : // "always active" has additional restrictions
330 [ - + ]: 26 : assert(state == ThresholdState::ACTIVE);
331 [ - + ]: 26 : assert(exp_state == ThresholdState::ACTIVE);
332 [ - + ]: 26 : assert(since == 0);
333 [ + + ]: 203 : } else if (never_active_test) {
334 : : // "never active" does too
335 [ - + ]: 7 : assert(state == ThresholdState::FAILED);
336 [ - + ]: 7 : assert(exp_state == ThresholdState::FAILED);
337 [ - + ]: 7 : assert(since == 0);
338 : : } else {
339 : : // for signalled deployments, the initial state is always DEFINED
340 [ + + - + ]: 196 : assert(since > 0 || state == ThresholdState::DEFINED);
341 [ + + - + ]: 196 : assert(exp_since > 0 || exp_state == ThresholdState::DEFINED);
342 : : }
343 : 254 : }
344 : : } // namespace
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