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

1 files changed, 72 insertions, 0 deletions

diff --git a/src/util/hash_type.h b/src/util/hash_type.h
new file mode 100644
index 0000000000..13b831cf19
--- /dev/null
+++ b/src/util/hash_type.h
@@ -0,0 +1,72 @@
+// Copyright (c) 2020-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_HASH_TYPE_H
+#define BITCOIN_UTIL_HASH_TYPE_H
+
+template <typename HashType>
+class BaseHash
+{
+protected:
+    HashType m_hash;
+
+public:
+    BaseHash() : m_hash() {}
+    explicit BaseHash(const HashType& in) : m_hash(in) {}
+
+    unsigned char* begin()
+    {
+        return m_hash.begin();
+    }
+
+    const unsigned char* begin() const
+    {
+        return m_hash.begin();
+    }
+
+    unsigned char* end()
+    {
+        return m_hash.end();
+    }
+
+    const unsigned char* end() const
+    {
+        return m_hash.end();
+    }
+
+    operator std::vector<unsigned char>() const
+    {
+        return std::vector<unsigned char>{m_hash.begin(), m_hash.end()};
+    }
+
+    std::string ToString() const
+    {
+        return m_hash.ToString();
+    }
+
+    bool operator==(const BaseHash<HashType>& other) const noexcept
+    {
+        return m_hash == other.m_hash;
+    }
+
+    bool operator!=(const BaseHash<HashType>& other) const noexcept
+    {
+        return !(m_hash == other.m_hash);
+    }
+
+    bool operator<(const BaseHash<HashType>& other) const noexcept
+    {
+        return m_hash < other.m_hash;
+    }
+
+    size_t size() const
+    {
+        return m_hash.size();
+    }
+
+    unsigned char* data() { return m_hash.data(); }
+    const unsigned char* data() const { return m_hash.data(); }
+};
+
+#endif // BITCOIN_UTIL_HASH_TYPE_H