From 41e58faf043864a64a6db08a8df527fa5fd1ec5b Mon Sep 17 00:00:00 2001 From: "Wladimir J. van der Laan" Date: Tue, 27 Sep 2016 14:05:24 +0200 Subject: [PATCH] net: Consistent checksum handling In principle, the checksums of P2P packets are simply 4-byte blobs which are the first four bytes of SHA256(SHA256(payload)). Currently they are handled as little-endian 32-bit integers half of the time, as blobs the other half, sometimes copying the one to the other, resulting in somewhat confused code. This PR changes the handling to be consistent both at packet creation and receiving, making it (I think) easier to understand. --- src/main.cpp | 9 +++++---- src/net.cpp | 6 ++---- src/protocol.cpp | 4 ++-- src/protocol.h | 4 ++-- 4 files changed, 11 insertions(+), 12 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index c33b41ac4..ab6721971 100644 --- a/src/main.cpp +++ b/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; } diff --git a/src/net.cpp b/src/net.cpp index cce06f2d6..770e2d295 100644 --- a/src/net.cpp +++ b/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); diff --git a/src/protocol.cpp b/src/protocol.cpp index 247c6c212..54ad62b1a 100644 --- a/src/protocol.cpp +++ b/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 diff --git a/src/protocol.h b/src/protocol.h index 9b474ec79..177d74530 100644 --- a/src/protocol.h +++ b/src/protocol.h @@ -45,7 +45,7 @@ public: READWRITE(FLATDATA(pchMessageStart)); READWRITE(FLATDATA(pchCommand)); READWRITE(nMessageSize); - READWRITE(nChecksum); + READWRITE(FLATDATA(pchChecksum)); } // TODO: make private (improves encapsulation) @@ -62,7 +62,7 @@ public: char pchMessageStart[MESSAGE_START_SIZE]; char pchCommand[COMMAND_SIZE]; unsigned int nMessageSize; - unsigned int nChecksum; + uint8_t pchChecksum[CHECKSUM_SIZE]; }; /**