From e9e4cad8e8affa82f047acf999d4195168024287 Mon Sep 17 00:00:00 2001
From: Capri <caprimc@yahoo.com>
Date: Tue, 15 Sep 2026 22:06:59 +0000
Subject: [PATCH] Validate RandomX proof of work when reading blocks

---
 src/node/blockstorage.cpp | 29 ++++++++++++++++++++++++++---
 src/validation.cpp        |  9 +--------
 src/validation.h          |  8 ++++++++
 3 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
index ae867a9..de6646f 100644
--- a/src/node/blockstorage.cpp
+++ b/src/node/blockstorage.cpp
@@ -379,9 +379,16 @@ bool ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, const Consensus::P
         return error("%s: Deserialize or I/O error - %s at %s", __func__, e.what(), pos.ToString());
     }
 
-    // Check the header
-    if (!CheckProofOfWork(block.GetHash(), block.nBits, consensusParams)) {
-        return error("ReadBlockFromDisk: Errors in block header at %s", pos.ToString());
+    // Check context-free proof of work. RandomX requires the previous block
+    // index to resolve its deterministic seed and is therefore checked by
+    // the CBlockIndex overload below.
+    if (block.GetHash() == consensusParams.hashGenesisBlock ||
+        block.GetAlgo() == ALGO_SHA256D) {
+        if (!CheckProofOfWork(block.GetHash(), block.nBits, consensusParams)) {
+            return error("ReadBlockFromDisk: Errors in block header at %s", pos.ToString());
+        }
+    } else if (block.GetAlgo() != ALGO_RANDOMX) {
+        return error("ReadBlockFromDisk: Unknown proof-of-work algorithm at %s", pos.ToString());
     }
 
     // Signet only: check block solution
@@ -403,6 +410,22 @@ bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus
         return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() doesn't match index for %s at %s",
                      pindex->ToString(), block_pos.ToString());
     }
+
+    if (block.GetHash() != consensusParams.hashGenesisBlock &&
+        block.GetAlgo() == ALGO_RANDOMX) {
+        if (pindex->pprev == nullptr) {
+            return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): RandomX block has no previous block index for %s at %s",
+                         pindex->ToString(), block_pos.ToString());
+        }
+
+        BlockValidationState state;
+        if (!CheckContextualRandomXProofOfWork(
+                block, state, consensusParams, pindex->pprev, true)) {
+            return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): RandomX proof of work failed for %s at %s: %s",
+                         pindex->ToString(), block_pos.ToString(), state.ToString());
+        }
+    }
+
     return true;
 }
 
diff --git a/src/validation.cpp b/src/validation.cpp
index c763ffb..e02fce2 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1747,13 +1747,6 @@ static int64_t nTimeCallbacks = 0;
 static int64_t nTimeTotal = 0;
 static int64_t nBlocksTotal = 0;
 
-static bool CheckContextualRandomXProofOfWork(
-    const CBlockHeader& block,
-    BlockValidationState& state,
-    const Consensus::Params& consensusParams,
-    const CBlockIndex* pindexPrev,
-    bool fCheckPOW);
-
 /** Apply the effects of this block (with given index) on the UTXO set represented by coins.
  *  Validity checks that depend on the UTXO set are also done; ConnectBlock()
  *  can fail if those validity checks fail (among other reasons). */
@@ -3157,7 +3150,7 @@ static bool CheckRandomXProofOfWork(
     return true;
 }
 
-static bool CheckContextualRandomXProofOfWork(
+bool CheckContextualRandomXProofOfWork(
     const CBlockHeader& block,
     BlockValidationState& state,
     const Consensus::Params& consensusParams,
diff --git a/src/validation.h b/src/validation.h
index 646dc06..1d785fe 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -346,6 +346,14 @@ void InitScriptExecutionCache();
 /** Context-independent validity checks */
 bool CheckBlock(const CBlock& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true, bool fCheckMerkleRoot = true);
 
+/** Context-dependent RandomX proof-of-work validation. */
+bool CheckContextualRandomXProofOfWork(
+    const CBlockHeader& block,
+    BlockValidationState& state,
+    const Consensus::Params& consensusParams,
+    const CBlockIndex* pindexPrev,
+    bool fCheckPOW = true);
+
 /** Check a block is completely valid from start to finish (only works on top of our current best block) */
 bool TestBlockValidity(BlockValidationState& state,
                        const CChainParams& chainparams,