From e5bef4962b285acb5303fe0079269ff678c66335 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. (cherry picked from commit bitcoin/bitcoin@41e58faf043864a64a6db08a8df527fa5fd1ec5b) --- 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 e9052aaeb..a7b3c0eae 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -7215,11 +7215,12 @@ bool ProcessMessages(const CChainParams& chainparams, CNode* pfrom) // 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 bdc650e85..7f594b2c8 100644 --- a/src/net.cpp +++ b/src/net.cpp @@ -2356,10 +2356,8 @@ void CNode::EndMessage() 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 193555d7b..9bb636b8d 100644 --- a/src/protocol.cpp +++ b/src/protocol.cpp @@ -17,7 +17,7 @@ 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) @@ -26,7 +26,7 @@ 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 bb43edf64..dfc22b81a 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]; }; /** nServices flags */