Merge bitcoin/bitcoin#32646: p2p: Add witness mutation check inside FillBlock

28299ce776 p2p: remove vestigial READ_STATUS_CHECKBLOCK_FAILED (Greg Sanders)
bac9ee4830 p2p: Add witness mutation check inside FillBlock (Greg Sanders)

Pull request description:

  Since #29412, we have not allowed mutated blocks to continue being processed immediately the block is received, but this is only done for the legacy BLOCK message.

  Extend these checks as belt-and-suspenders to not allow similar mutation strategies to affect relay by honest peers by applying the check inside `PartiallyDownloadedBlock::FillBlock`, immediately before returning `READ_STATUS_OK`.

ACKs for top commit:
  Crypt-iQ:
    ACK 28299ce776
  achow101:
    ACK 28299ce776
  stratospher:
    ACK 28299ce7.
  dergoegge:
    Code review ACK 28299ce776

Tree-SHA512: 883d7c12ca096234b425e6fe12e46b0611607600916e6ac8d1c8112224aa76924b7b074754910163ac2ec15379075d618a9ece3642649ac7629cddb0d4e432ea

src/test/fuzz/partially_downloaded_block.cpp

@@ -36,14 +36,10 @@ void initialize_pdb()
     g_setup = testing_setup.get();
 }
 
-PartiallyDownloadedBlock::CheckBlockFn FuzzedCheckBlock(std::optional<BlockValidationResult> result)
+PartiallyDownloadedBlock::IsBlockMutatedFn FuzzedIsBlockMutated(bool result)
 {
-    return [result](const CBlock&, BlockValidationState& state, const Consensus::Params&, bool, bool) {
-        if (result) {
-            return state.Invalid(*result);
-        }
-
-        return true;
+    return [result](const CBlock& block, bool) {
+        return result;
     };
 }
 
@@ -115,35 +111,22 @@ FUZZ_TARGET(partially_downloaded_block, .init = initialize_pdb)
         skipped_missing |= (!pdb.IsTxAvailable(i) && skip);
     }
 
-    // Mock CheckBlock
-    bool fail_check_block{fuzzed_data_provider.ConsumeBool()};
-    auto validation_result =
-        fuzzed_data_provider.PickValueInArray(
-            {BlockValidationResult::BLOCK_RESULT_UNSET,
-             BlockValidationResult::BLOCK_CONSENSUS,
-             BlockValidationResult::BLOCK_CACHED_INVALID,
-             BlockValidationResult::BLOCK_INVALID_HEADER,
-             BlockValidationResult::BLOCK_MUTATED,
-             BlockValidationResult::BLOCK_MISSING_PREV,
-             BlockValidationResult::BLOCK_INVALID_PREV,
-             BlockValidationResult::BLOCK_TIME_FUTURE,
-             BlockValidationResult::BLOCK_HEADER_LOW_WORK});
-    pdb.m_check_block_mock = FuzzedCheckBlock(
-        fail_check_block ?
-            std::optional<BlockValidationResult>{validation_result} :
-            std::nullopt);
+    bool segwit_active{fuzzed_data_provider.ConsumeBool()};
+
+    // Mock IsBlockMutated
+    bool fail_block_mutated{fuzzed_data_provider.ConsumeBool()};
+    pdb.m_check_block_mutated_mock = FuzzedIsBlockMutated(fail_block_mutated);
 
     CBlock reconstructed_block;
-    auto fill_status{pdb.FillBlock(reconstructed_block, missing)};
+    auto fill_status{pdb.FillBlock(reconstructed_block, missing, segwit_active)};
     switch (fill_status) {
     case READ_STATUS_OK:
         assert(!skipped_missing);
-        assert(!fail_check_block);
+        assert(!fail_block_mutated);
         assert(block->GetHash() == reconstructed_block.GetHash());
         break;
-    case READ_STATUS_CHECKBLOCK_FAILED: [[fallthrough]];
     case READ_STATUS_FAILED:
-        assert(fail_check_block);
+        assert(fail_block_mutated);
         break;
     case READ_STATUS_INVALID:
         break;