From fe1dc62cef88280d2490a619beded052f313c6fc Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Sun, 30 Oct 2016 18:02:16 -0400
Subject: [PATCH] Hash P2P messages as they are received instead of at
 process-time

---
 src/main.cpp | 2 +-
 src/net.cpp  | 9 +++++++++
 src/net.h    | 5 +++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/main.cpp b/src/main.cpp
index 5e17ec625..56c24d93b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -6350,7 +6350,7 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman)
 
         // Checksum
         CDataStream& vRecv = msg.vRecv;
-        uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
+        const uint256& hash = msg.GetMessageHash();
         if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0)
         {
             LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR expected %s was %s\n", __func__,
diff --git a/src/net.cpp b/src/net.cpp
index 48ba9588d..a2414acf4 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -758,12 +758,21 @@ int CNetMessage::readData(const char *pch, unsigned int nBytes)
         vRecv.resize(std::min(hdr.nMessageSize, nDataPos + nCopy + 256 * 1024));
     }
 
+    hasher.Write((const unsigned char*)pch, nCopy);
     memcpy(&vRecv[nDataPos], pch, nCopy);
     nDataPos += nCopy;
 
     return nCopy;
 }
 
+const uint256& CNetMessage::GetMessageHash() const
+{
+    assert(complete());
+    if (data_hash.IsNull())
+        hasher.Finalize(data_hash.begin());
+    return data_hash;
+}
+
 
 
 
diff --git a/src/net.h b/src/net.h
index 58b492e59..955bad488 100644
--- a/src/net.h
+++ b/src/net.h
@@ -512,6 +512,9 @@ public:
 
 
 class CNetMessage {
+private:
+    mutable CHash256 hasher;
+    mutable uint256 data_hash;
 public:
     bool in_data;                   // parsing header (false) or data (true)
 
@@ -539,6 +542,8 @@ public:
         return (hdr.nMessageSize == nDataPos);
     }
 
+    const uint256& GetMessageHash() const;
+
     void SetVersion(int nVersionIn)
     {
         hdrbuf.SetVersion(nVersionIn);