C++ - Detours WinSock Hooking

Question

What I am trying to do is use the Detours library to hook into an applications WinSock2 send() and recv() functions (a packet logger).

While it does work for the send() function, it does not, however, work for the recv() function.

Here is my relevant code:

#include <cstdio>
#include <ctime>
#include <fstream>
#include <iomanip>
#include <string>
#include <windows.h>
#include <detours.h>

#pragma comment( lib, "Ws2_32.lib" )
#pragma comment( lib, "detours.lib" )
#pragma comment( lib, "detoured.lib" )
#pragma comment( lib, "Mswsock.lib" )

std::ofstream Logger;

std::string NowToString() {
    time_t rawtime;
    tm *timeinfo = new tm();
    char buffer[32];

    time( &rawtime );
    localtime_s( timeinfo, &rawtime );

    strftime( buffer, 32, "%m/%d/%Y %I:%M:%S %p", timeinfo );

    delete timeinfo;

    return std::string( buffer );
}

std::string TimeToString() {
    time_t rawtime;
    tm *timeinfo = new tm();
    char buffer[32];

    time( &rawtime );
    localtime_s( timeinfo, &rawtime );

    strftime( buffer, 32, "%I:%M:%S %p", timeinfo );

    delete timeinfo;

    return std::string( buffer );
}

void LogPacket( const char *buf, int len ) {
    Logger << "        0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F\n";
    Logger << "       -- -- -- -- -- -- -- --  -- -- -- -- -- -- -- --\n";
    Logger << "0000   ";

    for ( int i = 0; i < len; ++i ) {
     if ( i != 0 && i % 16 == 0 ) {
      Logger << "  ";

      int line = ( i / 16 ) - 1;

      for ( int j = 0; j < 16; ++j ) {
       char c = buf[line * 16 + j];

       if ( c >= 32 && c <= 126 ) {
        Logger << c;
       } else {
        Logger << '.';
       }
      }

      Logger << "\n" << std::hex << std::setw( 4 ) << std::setfill( '0' ) << i << std::dec << std::setw( 0 ) << "   ";
     } else if ( i % 16 == 8 ) {
      Logger << ' ';
     }

     Logger << std::hex << std::setw( 2 ) << std::setfill( '0' ) << ( int( buf[i] ) & 0xFF ) << ' ';
     Logger << std::dec << std::setw( 0 );

     if ( i == len - 1 ) {
      int remaining = 16 - ( len % 16 );
      int fill = ( remaining * 3 ) + 2;

      if ( remaining >= 8 ) {
       ++fill;
      }

      for ( int j = 0; j < fill; ++j ) {
       Logger << ' ';
      }

      int line = ( i - ( ( len % 16 ) - 1 ) ) / 16 ;

      for ( int k = 0; k < ( len % 16 ); ++k ) {
       char c = buf[line * 16 + k];

       if ( c >= 32 && c <= 126 ) {
        Logger << c;
       } else {
        Logger << '.';
       }
      }
     }
    }

    Logger << "\n\n";
}

int ( WINAPI *Real_Send )( SOCKET s, const char *buf, int len, int flags ) = send;
int ( WINAPI *Real_Recv )( SOCKET s, char *buf, int len, int flags ) = recv;
int ( WINAPI *Real_RecvFrom )( SOCKET s, char *buf, int len, int flags, sockaddr *from, int *fromlen ) = recvfrom;
int ( WINAPI *Real_WSARecvEx )( SOCKET s, char *buf, int len, int *flags ) = WSARecvEx;

int WINAPI Mine_Send( SOCKET s, const char* buf, int len, int flags );
int WINAPI Mine_Recv( SOCKET s, char *buf, int len, int flags );
int WINAPI Mine_RecvFrom( SOCKET s, char *buf, int len, int flags, sockaddr *from, int *fromlen );
int WINAPI Mine_WSARecvEx( SOCKET s, char *buf, int len, int *flags );

int WINAPI Mine_Send( SOCKET s, const char *buf, int len, int flags ) {
    Logger << TimeToString() << ": Client -> Server (Length: " << len << " bytes)\n\n";
    LogPacket( buf, len );
    Logger << std::endl;

    return Real_Send( s, buf, len, flags );
}

int WINAPI Mine_Recv( SOCKET s, char *buf, int len, int flags ) {
    Logger << TimeToString() << ": Server -> Client (Length: " << len << " bytes)\n\n";
    LogPacket( buf, len );
    Logger << std::endl;

    return Real_Recv( s, buf, len, flags );
}

int WINAPI Mine_RecvFrom( SOCKET s, char *buf, int len, int flags, sockaddr *from, int *fromlen ) {
    Logger << TimeToString() << ": Server -> Client (Length: " << len << " bytes)*\n\n";
    LogPacket( buf, len );
    Logger << std::endl;

    return Real_RecvFrom( s, buf, len, flags, from, fromlen );
}

int WINAPI Mine_WSARecvEx( SOCKET s, char *buf, int len, int *flags ) {
    Logger << TimeToString() << ": Server -> Client (Length: " << len << " bytes)**\n\n";
    LogPacket( buf, len );
    Logger << std::endl;

    return Real_WSARecvEx( s, buf, len, flags );
}

BOOL WINAPI DllMain( HINSTANCE, DWORD dwReason, LPVOID ) {
    switch ( dwReason ) {
     case DLL_PROCESS_ATTACH: 
      Logger.open( "C:\\Packets.txt", std::ios::out | std::ios::app | std::ios::ate );

      if ( Logger.tellp() > 0 ) {
       Logger << "\n\n\n";
      }

      Logger << "##\n## Logging Started (" << NowToString() << ")\n##\n\n\n";

      DetourTransactionBegin();
      DetourUpdateThread( GetCurrentThread() );
      DetourAttach( &(PVOID &)Real_Send, Mine_Send );
      DetourAttach( &(PVOID &)Real_Recv, Mine_Recv );
      DetourAttach( &(PVOID &)Real_RecvFrom, Mine_RecvFrom );
      DetourAttach( &(PVOID &)Real_WSARecvEx, Mine_WSARecvEx );
      DetourTransactionCommit();

      break;

     case DLL_PROCESS_DETACH:
      Logger << "##\n## Logging Stopped (" << NowToString() << ")\n##";
      Logger.close();

      DetourTransactionBegin();
      DetourUpdateThread( GetCurrentThread() );
      DetourDetach( &(PVOID &)Real_Send, Mine_Send );
      DetourDetach( &(PVOID &)Real_Recv, Mine_Recv );
      DetourDetach( &(PVOID &)Real_RecvFrom, Mine_RecvFrom );
      DetourDetach( &(PVOID &)Real_WSARecvEx, Mine_WSARecvEx );
      DetourTransactionCommit();

      break;
    }

    return TRUE;
}

Any ideas?

EDIT: So I've hooked recvfrom(), and WSARecvEx() as well, and it still doesn't log the outgoing packets! I've updated my code with my exact code.

Answer 1

To use hooking effectively you need to make sure you really hook all of the relevant endpoints or atleast a common denominator that is ensured to be called eventually from all of them.
In the case of recv() I think its possible that the application actually calls WSARecv() instead.
You can use depends.exe to find out exactly what functions does the application/library import from Ws2_32.dll to know which ones you need to hook.

Answer 2

Well, a few months later I figured it out: I was hooking WinSock 2 functions when I should have been hooking WinSock 1.1's send()/recv()!