[validation] Introduce IsBlockMutated

Github-Pull: bitcoin#29412
Rebased-From: 66abce1

src/validation.cpp

@@ -3806,6 +3806,26 @@ bool HasValidProofOfWork(const std::vector<CBlockHeader>& headers, const Consens
             [&](const auto& header) { return CheckProofOfWork(header.GetHash(), header.nBits, consensusParams);});
 }
 
+bool IsBlockMutated(const CBlock& block, bool check_witness_root)
+{
+    BlockValidationState state;
+    if (!CheckMerkleRoot(block, state)) {
+        LogPrint(BCLog::VALIDATION, "Block mutated: %s\n", state.ToString());
+        return true;
+    }
+
+    if (block.vtx.empty() || !block.vtx[0]->IsCoinBase()) {
+        return false;
+    }
+
+    if (!CheckWitnessMalleation(block, check_witness_root, state)) {
+        LogPrint(BCLog::VALIDATION, "Block mutated: %s\n", state.ToString());
+        return true;
+    }
+
+    return false;
+}
+
 arith_uint256 CalculateHeadersWork(const std::vector<CBlockHeader>& headers)
 {
     arith_uint256 total_work{0};

src/validation.h

@@ -360,6 +360,9 @@ bool TestBlockValidity(BlockValidationState& state,
 /** Check with the proof of work on each blockheader matches the value in nBits */
 bool HasValidProofOfWork(const std::vector<CBlockHeader>& headers, const Consensus::Params& consensusParams);
 
+/** Check if a block has been mutated (with respect to its merkle root and witness commitments). */
+bool IsBlockMutated(const CBlock& block, bool check_witness_root);
+
 /** Return the sum of the work on a given set of headers */
 arith_uint256 CalculateHeadersWork(const std::vector<CBlockHeader>& headers);