Merge #8822: net: Consistent checksum handling

305087b net: Hardcode protocol sizes and use fixed-size types (Wladimir J. van der Laan)
41e58fa net: Consistent checksum handling (Wladimir J. van der Laan)

src/main.cpp

@@ -6253,11 +6253,12 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman)
         // Checksum
         CDataStream& vRecv = msg.vRecv;
         uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
-        unsigned int nChecksum = ReadLE32((unsigned char*)&hash);
-        if (nChecksum != hdr.nChecksum)
+        if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0)
         {
-            LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR nChecksum=%08x hdr.nChecksum=%08x\n", __func__,
-               SanitizeString(strCommand), nMessageSize, nChecksum, hdr.nChecksum);
+            LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR expected %s was %s\n", __func__,
+               SanitizeString(strCommand), nMessageSize,
+               HexStr(hash.begin(), hash.begin()+CMessageHeader::CHECKSUM_SIZE),
+               HexStr(hdr.pchChecksum, hdr.pchChecksum+CMessageHeader::CHECKSUM_SIZE));
             continue;
         }
 

src/net.cpp

@@ -2661,10 +2661,8 @@ void CNode::EndMessage(const char* pszCommand) UNLOCK_FUNCTION(cs_vSend)
 
     // Set the checksum
     uint256 hash = Hash(ssSend.begin() + CMessageHeader::HEADER_SIZE, ssSend.end());
-    unsigned int nChecksum = 0;
-    memcpy(&nChecksum, &hash, sizeof(nChecksum));
-    assert(ssSend.size () >= CMessageHeader::CHECKSUM_OFFSET + sizeof(nChecksum));
-    memcpy((char*)&ssSend[CMessageHeader::CHECKSUM_OFFSET], &nChecksum, sizeof(nChecksum));
+    assert(ssSend.size () >= CMessageHeader::CHECKSUM_OFFSET + CMessageHeader::CHECKSUM_SIZE);
+    memcpy((char*)&ssSend[CMessageHeader::CHECKSUM_OFFSET], hash.begin(), CMessageHeader::CHECKSUM_SIZE);
 
     LogPrint("net", "(%d bytes) peer=%d\n", nSize, id);
 

src/protocol.cpp

@@ -79,7 +79,7 @@ CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn)
     memcpy(pchMessageStart, pchMessageStartIn, MESSAGE_START_SIZE);
     memset(pchCommand, 0, sizeof(pchCommand));
     nMessageSize = -1;
-    nChecksum = 0;
+    memset(pchChecksum, 0, CHECKSUM_SIZE);
 }
 
 CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn, const char* pszCommand, unsigned int nMessageSizeIn)
@@ -88,7 +88,7 @@ CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn, const
     memset(pchCommand, 0, sizeof(pchCommand));
     strncpy(pchCommand, pszCommand, COMMAND_SIZE);
     nMessageSize = nMessageSizeIn;
-    nChecksum = 0;
+    memset(pchChecksum, 0, CHECKSUM_SIZE);
 }
 
 std::string CMessageHeader::GetCommand() const

src/protocol.h

@@ -45,15 +45,15 @@ public:
         READWRITE(FLATDATA(pchMessageStart));
         READWRITE(FLATDATA(pchCommand));
         READWRITE(nMessageSize);
-        READWRITE(nChecksum);
+        READWRITE(FLATDATA(pchChecksum));
     }
 
     // TODO: make private (improves encapsulation)
 public:
     enum {
         COMMAND_SIZE = 12,
-        MESSAGE_SIZE_SIZE = sizeof(int),
-        CHECKSUM_SIZE = sizeof(int),
+        MESSAGE_SIZE_SIZE = 4,
+        CHECKSUM_SIZE = 4,
 
         MESSAGE_SIZE_OFFSET = MESSAGE_START_SIZE + COMMAND_SIZE,
         CHECKSUM_OFFSET = MESSAGE_SIZE_OFFSET + MESSAGE_SIZE_SIZE,
@@ -61,8 +61,8 @@ public:
     };
     char pchMessageStart[MESSAGE_START_SIZE];
     char pchCommand[COMMAND_SIZE];
-    unsigned int nMessageSize;
-    unsigned int nChecksum;
+    uint32_t nMessageSize;
+    uint8_t pchChecksum[CHECKSUM_SIZE];
 };
 
 /**