Merge bitcoin/bitcoin#21953: fuzz: Add utxo_snapshot target

fa91994b1b9b6da3bb2a2f722d9251d7d0f2167e fuzz: Add utxo_snapshot target (MarcoFalke)

Pull request description:

ACKs for top commit:
  jamesob:
    ACK https://github.com/bitcoin/bitcoin/pull/21953/commits/fa91994b1b9b6da3bb2a2f722d9251d7d0f2167e

Tree-SHA512: a00f077102a4e4e321bd1464c3fa11e7a5b9e04324b9be87aa28cfdc77630db7fc772d3a3768dc6ec36bbdd2d67b7e0719f0cf3fd87b4a1087365b934e137b5c

1 files changed, 87 insertions, 0 deletions

diff --git a/src/test/fuzz/utxo_snapshot.cpp b/src/test/fuzz/utxo_snapshot.cpp
new file mode 100644
index 0000000000..0b42282b34
--- /dev/null
+++ b/src/test/fuzz/utxo_snapshot.cpp
@@ -0,0 +1,87 @@
+// Copyright (c) 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 <chainparams.h>
+#include <consensus/validation.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <test/util/mining.h>
+#include <test/util/setup_common.h>
+#include <validation.h>
+#include <validationinterface.h>
+
+namespace {
+
+const std::vector<std::shared_ptr<CBlock>>* g_chain;
+
+void initialize_chain()
+{
+    const auto params{CreateChainParams(ArgsManager{}, CBaseChainParams::REGTEST)};
+    static const auto chain{CreateBlockChain(2 * COINBASE_MATURITY, *params)};
+    g_chain = &chain;
+}
+
+FUZZ_TARGET_INIT(utxo_snapshot, initialize_chain)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    std::unique_ptr<const TestingSetup> setup{MakeNoLogFileContext<const TestingSetup>()};
+    const auto& node = setup->m_node;
+    auto& chainman{*node.chainman};
+
+    const auto snapshot_path = GetDataDir() / "fuzzed_snapshot.dat";
+
+    Assert(!chainman.SnapshotBlockhash());
+
+    {
+        CAutoFile outfile{fsbridge::fopen(snapshot_path, "wb"), SER_DISK, CLIENT_VERSION};
+        const auto file_data{ConsumeRandomLengthByteVector(fuzzed_data_provider)};
+        outfile << Span<const uint8_t>{file_data};
+    }
+
+    const auto ActivateFuzzedSnapshot{[&] {
+        CAutoFile infile{fsbridge::fopen(snapshot_path, "rb"), SER_DISK, CLIENT_VERSION};
+        SnapshotMetadata metadata;
+        try {
+            infile >> metadata;
+        } catch (const std::ios_base::failure&) {
+            return false;
+        }
+        return chainman.ActivateSnapshot(infile, metadata, /* in_memory */ true);
+    }};
+
+    if (fuzzed_data_provider.ConsumeBool()) {
+        for (const auto& block : *g_chain) {
+            BlockValidationState dummy;
+            bool processed{chainman.ProcessNewBlockHeaders({*block}, dummy, ::Params())};
+            Assert(processed);
+            const auto* index{WITH_LOCK(::cs_main, return chainman.m_blockman.LookupBlockIndex(block->GetHash()))};
+            Assert(index);
+        }
+    }
+
+    if (ActivateFuzzedSnapshot()) {
+        LOCK(::cs_main);
+        Assert(!chainman.ActiveChainstate().m_from_snapshot_blockhash->IsNull());
+        Assert(*chainman.ActiveChainstate().m_from_snapshot_blockhash ==
+               *chainman.SnapshotBlockhash());
+        const auto& coinscache{chainman.ActiveChainstate().CoinsTip()};
+        int64_t chain_tx{};
+        for (const auto& block : *g_chain) {
+            Assert(coinscache.HaveCoin(COutPoint{block->vtx.at(0)->GetHash(), 0}));
+            const auto* index{chainman.m_blockman.LookupBlockIndex(block->GetHash())};
+            const auto num_tx{Assert(index)->nTx};
+            Assert(num_tx == 1);
+            chain_tx += num_tx;
+        }
+        Assert(g_chain->size() == coinscache.GetCacheSize());
+        Assert(chain_tx == chainman.ActiveTip()->nChainTx);
+    } else {
+        Assert(!chainman.SnapshotBlockhash());
+        Assert(!chainman.ActiveChainstate().m_from_snapshot_blockhash);
+    }
+    // Snapshot should refuse to load a second time regardless of validity
+    Assert(!ActivateFuzzedSnapshot());
+}
+} // namespace