Merge bitcoin/bitcoin#28450: Add package evaluation fuzzer

262ab8e Add package evaluation fuzzer (Greg Sanders)

Pull request description:

  This fuzzer target caught the issue in bitcoin/bitcoin#28251 within 5 minutes on master branch, and an additional issue which I've applied a preliminary patch to cover.

  Fuzzer target does the following:

  1) Picks mempool confgs, including max package size, count, mempool size, etc
  2) Generates 1 to 26 transactions with arbitrary coins/fees, the first N-1 spending only confirmed outpoints
  3) Nth transaction, if >1, sweeps all unconfirmed outpoints in mempool
  4) If N==1, it may submit it through single-tx submission path, to allow for more interesting topologies
  5) Otherwise submits through package submission interface
  6) Repeat 1-5  a few hundred times per mempool instance

  In other words, it ends up building chains of txns in the mempool using parents-and-children packages, which is currently the topology supported on master.

  The test itself is a direct rip of tx_pool.cpp, with a number of assertions removed because they were failing for unknown reasons, likely due to the notification changes of single tx submission to package, which is used to track addition/removal of transactions in the test. I'll continue working on re-adding these assertions for further invariant testing.

ACKs for top commit:
  murchandamus:
    ACK 262ab8e
  glozow:
    reACK 262ab8e
  dergoegge:
    tACK 262ab8e

Tree-SHA512: 190784777d0f2361b051b3271db8f79b7927e3cab88596d2c30e556da721510bd17f6cc96f6bb03403bbf0589ad3f799fa54e63c1b2bd92a2084485b5e3e96a5

src/Makefile.test.include

@@ -300,6 +300,7 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/netbase_dns_lookup.cpp \
  test/fuzz/node_eviction.cpp \
  test/fuzz/p2p_transport_serialization.cpp \
+ test/fuzz/package_eval.cpp \
  test/fuzz/parse_hd_keypath.cpp \
  test/fuzz/parse_numbers.cpp \
  test/fuzz/parse_script.cpp \

src/test/fuzz/package_eval.cpp

@@ -0,0 +1,294 @@
+// 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 <consensus/validation.h>
+#include <node/context.h>
+#include <node/mempool_args.h>
+#include <node/miner.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <test/fuzz/util/mempool.h>
+#include <test/util/mining.h>
+#include <test/util/script.h>
+#include <test/util/setup_common.h>
+#include <test/util/txmempool.h>
+#include <util/rbf.h>
+#include <validation.h>
+#include <validationinterface.h>
+
+using node::NodeContext;
+
+namespace {
+
+const TestingSetup* g_setup;
+std::vector<COutPoint> g_outpoints_coinbase_init_mature;
+
+struct MockedTxPool : public CTxMemPool {
+    void RollingFeeUpdate() EXCLUSIVE_LOCKS_REQUIRED(!cs)
+    {
+        LOCK(cs);
+        lastRollingFeeUpdate = GetTime();
+        blockSinceLastRollingFeeBump = true;
+    }
+};
+
+void initialize_tx_pool()
+{
+    static const auto testing_setup = MakeNoLogFileContext<const TestingSetup>();
+    g_setup = testing_setup.get();
+
+    for (int i = 0; i < 2 * COINBASE_MATURITY; ++i) {
+        COutPoint prevout{MineBlock(g_setup->m_node, P2WSH_OP_TRUE)};
+        if (i < COINBASE_MATURITY) {
+            // Remember the txids to avoid expensive disk access later on
+            g_outpoints_coinbase_init_mature.push_back(prevout);
+        }
+    }
+    SyncWithValidationInterfaceQueue();
+}
+
+struct OutpointsUpdater final : public CValidationInterface {
+    std::set<COutPoint>& m_mempool_outpoints;
+
+    explicit OutpointsUpdater(std::set<COutPoint>& r)
+        : m_mempool_outpoints{r} {}
+
+    void TransactionAddedToMempool(const CTransactionRef& tx, uint64_t /* mempool_sequence */) override
+    {
+        // for coins spent we always want to be able to rbf so they're not removed
+
+        // outputs from this tx can now be spent
+        for (uint32_t index{0}; index < tx->vout.size(); ++index) {
+            m_mempool_outpoints.insert(COutPoint{tx->GetHash(), index});
+        }
+    }
+
+    void TransactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason, uint64_t /* mempool_sequence */) override
+    {
+        // outpoints spent by this tx are now available
+        for (const auto& input : tx->vin) {
+            // Could already exist if this was a replacement
+            m_mempool_outpoints.insert(input.prevout);
+        }
+        // outpoints created by this tx no longer exist
+        for (uint32_t index{0}; index < tx->vout.size(); ++index) {
+            m_mempool_outpoints.erase(COutPoint{tx->GetHash(), index});
+        }
+    }
+};
+
+struct TransactionsDelta final : public CValidationInterface {
+    std::set<CTransactionRef>& m_added;
+
+    explicit TransactionsDelta(std::set<CTransactionRef>& a)
+        : m_added{a} {}
+
+    void TransactionAddedToMempool(const CTransactionRef& tx, uint64_t /* mempool_sequence */) override
+    {
+        // Transactions may be entered and booted any number of times
+        m_added.insert(tx);
+    }
+
+    void TransactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason, uint64_t /* mempool_sequence */) override
+    {
+        // Transactions may be entered and booted any number of times
+         m_added.erase(tx);
+    }
+};
+
+void MockTime(FuzzedDataProvider& fuzzed_data_provider, const Chainstate& chainstate)
+{
+    const auto time = ConsumeTime(fuzzed_data_provider,
+                                  chainstate.m_chain.Tip()->GetMedianTimePast() + 1,
+                                  std::numeric_limits<decltype(chainstate.m_chain.Tip()->nTime)>::max());
+    SetMockTime(time);
+}
+
+CTxMemPool MakeMempool(FuzzedDataProvider& fuzzed_data_provider, const NodeContext& node)
+{
+    // Take the default options for tests...
+    CTxMemPool::Options mempool_opts{MemPoolOptionsForTest(node)};
+
+
+    // ...override specific options for this specific fuzz suite
+    mempool_opts.limits.ancestor_count = fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 50);
+    mempool_opts.limits.ancestor_size_vbytes = fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 202) * 1'000;
+    mempool_opts.limits.descendant_count = fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 50);
+    mempool_opts.limits.descendant_size_vbytes = fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 202) * 1'000;
+    mempool_opts.max_size_bytes = fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 200) * 1'000'000;
+    mempool_opts.expiry = std::chrono::hours{fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 999)};
+    nBytesPerSigOp = fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(1, 999);
+
+    mempool_opts.estimator = nullptr;
+    mempool_opts.check_ratio = 1;
+    mempool_opts.require_standard = fuzzed_data_provider.ConsumeBool();
+
+    // ...and construct a CTxMemPool from it
+    return CTxMemPool{mempool_opts};
+}
+
+FUZZ_TARGET(tx_package_eval, .init = initialize_tx_pool)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    const auto& node = g_setup->m_node;
+    auto& chainstate{static_cast<DummyChainState&>(node.chainman->ActiveChainstate())};
+
+    MockTime(fuzzed_data_provider, chainstate);
+
+    // All RBF-spendable outpoints outside of the unsubmitted package
+    std::set<COutPoint> mempool_outpoints;
+    std::map<COutPoint, CAmount> outpoints_value;
+    for (const auto& outpoint : g_outpoints_coinbase_init_mature) {
+        Assert(mempool_outpoints.insert(outpoint).second);
+        outpoints_value[outpoint] = 50 * COIN;
+    }
+
+    auto outpoints_updater = std::make_shared<OutpointsUpdater>(mempool_outpoints);
+    RegisterSharedValidationInterface(outpoints_updater);
+
+    CTxMemPool tx_pool_{MakeMempool(fuzzed_data_provider, node)};
+    MockedTxPool& tx_pool = *static_cast<MockedTxPool*>(&tx_pool_);
+
+    chainstate.SetMempool(&tx_pool);
+
+    LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 300)
+    {
+        Assert(!mempool_outpoints.empty());
+
+        std::vector<CTransactionRef> txs;
+
+        // Make packages of 1-to-26 transactions
+        const auto num_txs = (size_t) fuzzed_data_provider.ConsumeIntegralInRange<int>(1, 26);
+        std::set<COutPoint> package_outpoints;
+        while (txs.size() < num_txs) {
+
+            // Last transaction in a package needs to be a child of parents to get further in validation
+            // so the last transaction to be generated(in a >1 package) must spend all package-made outputs
+            // Note that this test currently only spends package outputs in last transaction.
+            bool last_tx = num_txs > 1 && txs.size() == num_txs - 1;
+
+            // Create transaction to add to the mempool
+            const CTransactionRef tx = [&] {
+                CMutableTransaction tx_mut;
+                tx_mut.nVersion = CTransaction::CURRENT_VERSION;
+                tx_mut.nLockTime = fuzzed_data_provider.ConsumeBool() ? 0 : fuzzed_data_provider.ConsumeIntegral<uint32_t>();
+                // Last tx will sweep all outpoints in package
+                const auto num_in = last_tx ? package_outpoints.size()  : fuzzed_data_provider.ConsumeIntegralInRange<int>(1, mempool_outpoints.size());
+                const auto num_out = fuzzed_data_provider.ConsumeIntegralInRange<int>(1, mempool_outpoints.size() * 2);
+
+                auto& outpoints = last_tx ? package_outpoints : mempool_outpoints;
+
+                Assert(!outpoints.empty());
+
+                CAmount amount_in{0};
+                for (size_t i = 0; i < num_in; ++i) {
+                    // Pop random outpoint
+                    auto pop = outpoints.begin();
+                    std::advance(pop, fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, outpoints.size() - 1));
+                    const auto outpoint = *pop;
+                    outpoints.erase(pop);
+                    // no need to update or erase from outpoints_value
+                    amount_in += outpoints_value.at(outpoint);
+
+                    // Create input
+                    const auto sequence = ConsumeSequence(fuzzed_data_provider);
+                    const auto script_sig = CScript{};
+                    const auto script_wit_stack = std::vector<std::vector<uint8_t>>{WITNESS_STACK_ELEM_OP_TRUE};
+                    CTxIn in;
+                    in.prevout = outpoint;
+                    in.nSequence = sequence;
+                    in.scriptSig = script_sig;
+                    in.scriptWitness.stack = script_wit_stack;
+
+                    tx_mut.vin.push_back(in);
+                }
+                const auto amount_fee = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(0, amount_in);
+                const auto amount_out = (amount_in - amount_fee) / num_out;
+                for (int i = 0; i < num_out; ++i) {
+                    tx_mut.vout.emplace_back(amount_out, P2WSH_OP_TRUE);
+                }
+                // TODO vary transaction sizes to catch size-related issues
+                auto tx = MakeTransactionRef(tx_mut);
+                // Restore previously removed outpoints, except in-package outpoints
+                if (!last_tx) {
+                    for (const auto& in : tx->vin) {
+                        Assert(outpoints.insert(in.prevout).second);
+                    }
+                    // Cache the in-package outpoints being made
+                    for (size_t i = 0; i < tx->vout.size(); ++i) {
+                        package_outpoints.emplace(tx->GetHash(), i);
+                    }
+                }
+                // We need newly-created values for the duration of this run
+                for (size_t i = 0; i < tx->vout.size(); ++i) {
+                    outpoints_value[COutPoint(tx->GetHash(), i)] = tx->vout[i].nValue;
+                }
+                return tx;
+            }();
+            txs.push_back(tx);
+        }
+
+        if (fuzzed_data_provider.ConsumeBool()) {
+            MockTime(fuzzed_data_provider, chainstate);
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            tx_pool.RollingFeeUpdate();
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            const auto& txid = fuzzed_data_provider.ConsumeBool() ?
+                                   txs.back()->GetHash() :
+                                   PickValue(fuzzed_data_provider, mempool_outpoints).hash;
+            const auto delta = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-50 * COIN, +50 * COIN);
+            tx_pool.PrioritiseTransaction(txid, delta);
+        }
+
+        // Remember all added transactions
+        std::set<CTransactionRef> added;
+        auto txr = std::make_shared<TransactionsDelta>(added);
+        RegisterSharedValidationInterface(txr);
+        const bool bypass_limits = fuzzed_data_provider.ConsumeBool();
+
+        // When there are multiple transactions in the package, we call ProcessNewPackage(txs, test_accept=false)
+        // and AcceptToMemoryPool(txs.back(), test_accept=true). When there is only 1 transaction, we might flip it
+        // (the package is a test accept and ATMP is a submission).
+        auto single_submit = txs.size() == 1 && fuzzed_data_provider.ConsumeBool();
+
+        const auto result_package = WITH_LOCK(::cs_main,
+                                    return ProcessNewPackage(chainstate, tx_pool, txs, /*test_accept=*/single_submit));
+        // If something went wrong due to a package-specific policy, it might not return a
+        // validation result for the transaction.
+        if (result_package.m_state.GetResult() != PackageValidationResult::PCKG_POLICY) {
+            auto it = result_package.m_tx_results.find(txs.back()->GetWitnessHash());
+            Assert(it != result_package.m_tx_results.end());
+            Assert(it->second.m_result_type == MempoolAcceptResult::ResultType::VALID ||
+                   it->second.m_result_type == MempoolAcceptResult::ResultType::INVALID ||
+                   it->second.m_result_type == MempoolAcceptResult::ResultType::MEMPOOL_ENTRY);
+        }
+
+        const auto res = WITH_LOCK(::cs_main, return AcceptToMemoryPool(chainstate, txs.back(), GetTime(), bypass_limits, /*test_accept=*/!single_submit));
+        const bool accepted = res.m_result_type == MempoolAcceptResult::ResultType::VALID;
+
+        SyncWithValidationInterfaceQueue();
+        UnregisterSharedValidationInterface(txr);
+
+        // There is only 1 transaction in the package. We did a test-package-accept and a ATMP
+        if (single_submit) {
+            Assert(accepted != added.empty());
+            Assert(accepted == res.m_state.IsValid());
+            if (accepted) {
+                Assert(added.size() == 1);
+                Assert(txs.back() == *added.begin());
+            }
+        } else {
+            // This is empty if it fails early checks, or "full" if transactions are looked at deeper
+            Assert(result_package.m_tx_results.size() == txs.size() || result_package.m_tx_results.empty());
+        }
+    }
+
+    UnregisterSharedValidationInterface(outpoints_updater);
+
+    WITH_LOCK(::cs_main, tx_pool.check(chainstate.CoinsTip(), chainstate.m_chain.Height() + 1));
+}
+} // namespace