2 files changed, 39 insertions, 5 deletions
diff --git a/src/hash.h b/src/hash.h
index eacb8f04fe..b8de19c0fd 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -160,6 +160,41 @@ public:
     }
 };
 
+/** Reads data from an underlying stream, while hashing the read data. */
+template<typename Source>
+class CHashVerifier : public CHashWriter
+{
+private:
+    Source* source;
+
+public:
+    CHashVerifier(Source* source_) : CHashWriter(source_->GetType(), source_->GetVersion()), source(source_) {}
+
+    void read(char* pch, size_t nSize)
+    {
+        source->read(pch, nSize);
+        this->write(pch, nSize);
+    }
+
+    void ignore(size_t nSize)
+    {
+        char data[1024];
+        while (nSize > 0) {
+            size_t now = std::min<size_t>(nSize, 1024);
+            read(data, now);
+            nSize -= now;
+        }
+    }
+
+    template<typename T>
+    CHashVerifier<Source>& operator>>(T& obj)
+    {
+        // Unserialize from this stream
+        ::Unserialize(*this, obj);
+        return (*this);
+    }
+};
+
 /** Compute the 256-bit hash of an object's serialization. */
 template<typename T>
 uint256 SerializeHash(const T& obj, int nType=SER_GETHASH, int nVersion=PROTOCOL_VERSION)
diff --git a/src/validation.cpp b/src/validation.cpp
index ed94be5c26..fc7e129c05 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1210,8 +1210,10 @@ bool UndoReadFromDisk(CBlockUndo& blockundo, const CDiskBlockPos& pos, const uin
 
     // Read block
     uint256 hashChecksum;
+    CHashVerifier<CAutoFile> verifier(&filein); // We need a CHashVerifier as reserializing may lose data
     try {
-        filein >> blockundo;
+        verifier << hashBlock;
+        verifier >> blockundo;
         filein >> hashChecksum;
     }
     catch (const std::exception& e) {
@@ -1219,10 +1221,7 @@ bool UndoReadFromDisk(CBlockUndo& blockundo, const CDiskBlockPos& pos, const uin
     }
 
     // Verify checksum
-    CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
-    hasher << hashBlock;
-    hasher << blockundo;
-    if (hashChecksum != hasher.GetHash())
+    if (hashChecksum != verifier.GetHash())
         return error("%s: Checksum mismatch", __func__);
 
     return true;