Merge bitcoin/bitcoin#21584: Fix assumeutxo crash due to invalid base_blockhash

fa340b87944764ea4e8e04038fe7471fd452bc23 refactor: Avoid magic value of all-zeros in assumeutxo base_blockhash (MarcoFalke)
fae33f98e6a8d5934edbdce2eb8688112eac41a8 Fix assumeutxo crash due to invalid base_blockhash (MarcoFalke)
fa5668bfb34e2778936af30e9fb6bd3c6bcf41fd refactor: Use type-safe assumeutxo hash (MarcoFalke)
00000077098a23e0ac9781f5f799c90fd2fd97de refactor: Remove unused code (MarcoFalke)
faa921f78788be0f236c6b10ed3f92dcf148d1cb move-only: Add util/hash_type (MarcoFalke)

Pull request description:

  Starting with commit d6af06d68aa, a block hash of all-zeros is invalid and will lead to a crash of the node. Can be tested by cherry-picking the test changes without the other changes.

  Stack trace (copied from https://github.com/bitcoin/bitcoin/pull/21584#discussion_r612673879):

  ```
  #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
  #1  0x00007ffff583c8b1 in __GI_abort () at abort.c:79
  #2  0x00007ffff582c42a in __assert_fail_base (fmt=0x7ffff59b3a38 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
      assertion=assertion@entry=0x555556c8b450 "!hashBlock.IsNull()", file=file@entry=0x555556c8b464 "txdb.cpp", line=line@entry=89,
      function=function@entry=0x555556c8b46d "virtual bool CCoinsViewDB::BatchWrite(CCoinsMap &, const uint256 &)") at assert.c:92
  #3  0x00007ffff582c4a2 in __GI___assert_fail (assertion=0x555556c8b450 "!hashBlock.IsNull()", file=0x555556c8b464 "txdb.cpp", line=89,
      function=0x555556c8b46d "virtual bool CCoinsViewDB::BatchWrite(CCoinsMap &, const uint256 &)") at assert.c:101
  #4  0x000055555636738b in CCoinsViewDB::BatchWrite (this=0x5555577975c0, mapCoins=std::unordered_map with 110 elements = {...}, hashBlock=...) at txdb.cpp:89
  #5  0x00005555564a2e80 in CCoinsViewBacked::BatchWrite (this=0x5555577975f8, mapCoins=std::unordered_map with 110 elements = {...}, hashBlock=...) at coins.cpp:30
  #6  0x00005555564a43de in CCoinsViewCache::Flush (this=0x55555778eaf0) at coins.cpp:223
  #7  0x00005555563fc11d in ChainstateManager::PopulateAndValidateSnapshot (this=0x55555740b038 <g_chainman>, snapshot_chainstate=..., coins_file=..., metadata=...)
      at validation.cpp:5422
  #8  0x00005555563fab3d in ChainstateManager::ActivateSnapshot (this=0x55555740b038 <g_chainman>, coins_file=..., metadata=..., in_memory=true) at validation.cpp:5299
  #9  0x0000555555e8c893 in validation_chainstatemanager_tests::CreateAndActivateUTXOSnapshot<validation_chainstatemanager_tests::chainstatemanager_activate_snapshot::test_method()::$_12>(NodeContext&, boost::filesystem::path, validation_chainstatemanager_tests::chainstatemanager_activate_snapshot::test_method()::$_12) (node=...,
      root=..., malleation=...) at test/validation_chainstatemanager_tests.cpp:199
  #10 0x0000555555e8877a in validation_chainstatemanager_tests::chainstatemanager_activate_snapshot::test_method (this=0x7fffffffc8d0)
      at test/validation_chainstatemanager_tests.cpp:262

ACKs for top commit:
  laanwj:
    Code review re-ACK fa340b87944764ea4e8e04038fe7471fd452bc23
  jamesob:
    ACK fa340b87944764ea4e8e04038fe7471fd452bc23 ([`jamesob/ackr/21584.1.MarcoFalke.fix_assumeutxo_crash_due`](https://github.com/jamesob/bitcoin/tree/ackr/21584.1.MarcoFalke.fix_assumeutxo_crash_due))

Tree-SHA512: c2c4e66c1abfd400ef18a04f22fec1f302f1ff4d27a18050f492f688319deb4ccdd165ff792eee0a1f816e7b69fb64080662b79517ab669e3d26b9eb77802851

2 files changed, 12 insertions, 9 deletions

diff --git a/src/test/validation_chainstatemanager_tests.cpp b/src/test/validation_chainstatemanager_tests.cpp
index 82e70b5cdc..0b912acb08 100644
--- a/src/test/validation_chainstatemanager_tests.cpp
+++ b/src/test/validation_chainstatemanager_tests.cpp
@@ -226,10 +226,8 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup)
 
     // Snapshot should refuse to load at this height.
     BOOST_REQUIRE(!CreateAndActivateUTXOSnapshot(m_node, m_path_root));
-    BOOST_CHECK(chainman.ActiveChainstate().m_from_snapshot_blockhash.IsNull());
-    BOOST_CHECK_EQUAL(
-        chainman.ActiveChainstate().m_from_snapshot_blockhash,
-        chainman.SnapshotBlockhash().value_or(uint256()));
+    BOOST_CHECK(!chainman.ActiveChainstate().m_from_snapshot_blockhash);
+    BOOST_CHECK(!chainman.SnapshotBlockhash());
 
     // Mine 10 more blocks, putting at us height 110 where a valid assumeutxo value can
     // be found.
@@ -263,15 +261,20 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup)
     BOOST_REQUIRE(!CreateAndActivateUTXOSnapshot(
         m_node, m_path_root, [](CAutoFile& auto_infile, SnapshotMetadata& metadata) {
             // Wrong hash
+            metadata.m_base_blockhash = uint256::ZERO;
+    }));
+    BOOST_REQUIRE(!CreateAndActivateUTXOSnapshot(
+        m_node, m_path_root, [](CAutoFile& auto_infile, SnapshotMetadata& metadata) {
+            // Wrong hash
             metadata.m_base_blockhash = uint256::ONE;
     }));
 
     BOOST_REQUIRE(CreateAndActivateUTXOSnapshot(m_node, m_path_root));
 
     // Ensure our active chain is the snapshot chainstate.
-    BOOST_CHECK(!chainman.ActiveChainstate().m_from_snapshot_blockhash.IsNull());
+    BOOST_CHECK(!chainman.ActiveChainstate().m_from_snapshot_blockhash->IsNull());
     BOOST_CHECK_EQUAL(
-        chainman.ActiveChainstate().m_from_snapshot_blockhash,
+        *chainman.ActiveChainstate().m_from_snapshot_blockhash,
         *chainman.SnapshotBlockhash());
 
     const AssumeutxoData& au_data = *ExpectedAssumeutxo(snapshot_height, ::Params());
@@ -347,7 +350,7 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup)
 
     // Snapshot blockhash should be unchanged.
     BOOST_CHECK_EQUAL(
-        chainman.ActiveChainstate().m_from_snapshot_blockhash,
+        *chainman.ActiveChainstate().m_from_snapshot_blockhash,
         loaded_snapshot_blockhash);
 }
 
diff --git a/src/test/validation_tests.cpp b/src/test/validation_tests.cpp
index d0317aca0a..1e5baec01a 100644
--- a/src/test/validation_tests.cpp
+++ b/src/test/validation_tests.cpp
@@ -135,11 +135,11 @@ BOOST_AUTO_TEST_CASE(test_assumeutxo)
     }
 
     const auto out110 = *ExpectedAssumeutxo(110, *params);
-    BOOST_CHECK_EQUAL(out110.hash_serialized, uint256S("1ebbf5850204c0bdb15bf030f47c7fe91d45c44c712697e4509ba67adb01c618"));
+    BOOST_CHECK_EQUAL(out110.hash_serialized.ToString(), "1ebbf5850204c0bdb15bf030f47c7fe91d45c44c712697e4509ba67adb01c618");
     BOOST_CHECK_EQUAL(out110.nChainTx, (unsigned int)110);
 
     const auto out210 = *ExpectedAssumeutxo(210, *params);
-    BOOST_CHECK_EQUAL(out210.hash_serialized, uint256S("9c5ed99ef98544b34f8920b6d1802f72ac28ae6e2bd2bd4c316ff10c230df3f2"));
+    BOOST_CHECK_EQUAL(out210.hash_serialized.ToString(), "9c5ed99ef98544b34f8920b6d1802f72ac28ae6e2bd2bd4c316ff10c230df3f2");
     BOOST_CHECK_EQUAL(out210.nChainTx, (unsigned int)210);
 }