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

6 files changed, 132 insertions, 6 deletions

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index d55f5e1850..dc79ea3125 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -303,6 +303,7 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/tx_out.cpp \
  test/fuzz/tx_pool.cpp \
  test/fuzz/txrequest.cpp \
+ test/fuzz/utxo_snapshot.cpp \
  test/fuzz/validation_load_mempool.cpp \
  test/fuzz/versionbits.cpp
 endif # ENABLE_FUZZ_BINARY
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index fc5a9d84cc..1b71c4db43 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -454,8 +454,8 @@ public:
                 {AssumeutxoHash{uint256S("0x1ebbf5850204c0bdb15bf030f47c7fe91d45c44c712697e4509ba67adb01c618")}, 110},
             },
             {
-                210,
-                {AssumeutxoHash{uint256S("0x9c5ed99ef98544b34f8920b6d1802f72ac28ae6e2bd2bd4c316ff10c230df3f2")}, 210},
+                200,
+                {AssumeutxoHash{uint256S("0x51c8d11d8b5c1de51543c579736e786aa2736206d1e11e627568029ce092cf62")}, 200},
             },
         };
 
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
diff --git a/src/test/util/mining.cpp b/src/test/util/mining.cpp
index 3fc3329da2..1204873828 100644
--- a/src/test/util/mining.cpp
+++ b/src/test/util/mining.cpp
@@ -11,8 +11,10 @@
 #include <node/context.h>
 #include <pow.h>
 #include <script/standard.h>
+#include <test/util/script.h>
 #include <util/check.h>
 #include <validation.h>
+#include <versionbits.h>
 
 CTxIn generatetoaddress(const NodeContext& node, const std::string& address)
 {
@@ -23,6 +25,37 @@ CTxIn generatetoaddress(const NodeContext& node, const std::string& address)
     return MineBlock(node, coinbase_script);
 }
 
+std::vector<std::shared_ptr<CBlock>> CreateBlockChain(size_t total_height, const CChainParams& params)
+{
+    std::vector<std::shared_ptr<CBlock>> ret{total_height};
+    auto time{params.GenesisBlock().nTime};
+    for (size_t height{0}; height < total_height; ++height) {
+        CBlock& block{*(ret.at(height) = std::make_shared<CBlock>())};
+
+        CMutableTransaction coinbase_tx;
+        coinbase_tx.vin.resize(1);
+        coinbase_tx.vin[0].prevout.SetNull();
+        coinbase_tx.vout.resize(1);
+        coinbase_tx.vout[0].scriptPubKey = P2WSH_OP_TRUE;
+        coinbase_tx.vout[0].nValue = GetBlockSubsidy(height + 1, params.GetConsensus());
+        coinbase_tx.vin[0].scriptSig = CScript() << (height + 1) << OP_0;
+        block.vtx = {MakeTransactionRef(std::move(coinbase_tx))};
+
+        block.nVersion = VERSIONBITS_LAST_OLD_BLOCK_VERSION;
+        block.hashPrevBlock = (height >= 1 ? *ret.at(height - 1) : params.GenesisBlock()).GetHash();
+        block.hashMerkleRoot = BlockMerkleRoot(block);
+        block.nTime = ++time;
+        block.nBits = params.GenesisBlock().nBits;
+        block.nNonce = 0;
+
+        while (!CheckProofOfWork(block.GetHash(), block.nBits, params.GetConsensus())) {
+            ++block.nNonce;
+            assert(block.nNonce);
+        }
+    }
+    return ret;
+}
+
 CTxIn MineBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey)
 {
     auto block = PrepareBlock(node, coinbase_scriptPubKey);
diff --git a/src/test/util/mining.h b/src/test/util/mining.h
index 5f250fffe8..1fc1864b91 100644
--- a/src/test/util/mining.h
+++ b/src/test/util/mining.h
@@ -7,12 +7,17 @@
 
 #include <memory>
 #include <string>
+#include <vector>
 
 class CBlock;
+class CChainParams;
 class CScript;
 class CTxIn;
 struct NodeContext;
 
+/** Create a blockchain, starting from genesis */
+std::vector<std::shared_ptr<CBlock>> CreateBlockChain(size_t total_height, const CChainParams& params);
+
 /** Returns the generated coin */
 CTxIn MineBlock(const NodeContext&, const CScript& coinbase_scriptPubKey);
 
diff --git a/src/test/validation_tests.cpp b/src/test/validation_tests.cpp
index 1e5baec01a..a0c2e76f00 100644
--- a/src/test/validation_tests.cpp
+++ b/src/test/validation_tests.cpp
@@ -136,11 +136,11 @@ BOOST_AUTO_TEST_CASE(test_assumeutxo)
 
     const auto out110 = *ExpectedAssumeutxo(110, *params);
     BOOST_CHECK_EQUAL(out110.hash_serialized.ToString(), "1ebbf5850204c0bdb15bf030f47c7fe91d45c44c712697e4509ba67adb01c618");
-    BOOST_CHECK_EQUAL(out110.nChainTx, (unsigned int)110);
+    BOOST_CHECK_EQUAL(out110.nChainTx, 110U);
 
-    const auto out210 = *ExpectedAssumeutxo(210, *params);
-    BOOST_CHECK_EQUAL(out210.hash_serialized.ToString(), "9c5ed99ef98544b34f8920b6d1802f72ac28ae6e2bd2bd4c316ff10c230df3f2");
-    BOOST_CHECK_EQUAL(out210.nChainTx, (unsigned int)210);
+    const auto out210 = *ExpectedAssumeutxo(200, *params);
+    BOOST_CHECK_EQUAL(out210.hash_serialized.ToString(), "51c8d11d8b5c1de51543c579736e786aa2736206d1e11e627568029ce092cf62");
+    BOOST_CHECK_EQUAL(out210.nChainTx, 200U);
 }
 
 BOOST_AUTO_TEST_SUITE_END()