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C++ hooking winsock

incognymviaStackOverflow
March 03, 2013
0 score
2 answers

I am trying to hook winsock send and recv in order to read all traffic of a process. I am injectin the following code as a dll inside the target process

#include "dll.h"
#include <windows.h>
#include <winsock2.h>
#include <iostream>
#include <fstream>

#pragma comment(lib, "ws2_32.lib")

using namespace std;

DllClass::DllClass()
{

}


DllClass::~DllClass ()
{

}

BYTE hook[6];
BYTE hook2[6];
BYTE jmp[6] = { 0xe9,0x00, 0x00, 0x00, 0x00 ,0xc3 };  
ofstream myfile;
ofstream myfile2;

DWORD HookFunction(LPCSTR lpModule, LPCSTR lpFuncName, LPVOID lpFunction, unsigned char *lpBackup)
{  
      DWORD dwAddr = (DWORD)GetProcAddress(GetModuleHandle(lpModule), lpFuncName);
      ReadProcessMemory(GetCurrentProcess(), (LPVOID)dwAddr, lpBackup, 6, 0);
      DWORD dwCalc = ((DWORD)lpFunction - dwAddr - 5);
      memcpy(&jmp[1], &dwCalc, 4);
      WriteProcessMemory(GetCurrentProcess(), (LPVOID)dwAddr, jmp, 6, 0);
      return dwAddr;
}    

BOOL UnHookFunction(LPCSTR lpModule, LPCSTR lpFuncName, unsigned char *lpBackup)
{
DWORD dwAddr = (DWORD)GetProcAddress(GetModuleHandle(lpModule), lpFuncName);
if (WriteProcessMemory(GetCurrentProcess(), (LPVOID)dwAddr, lpBackup, 6, 0))
        return TRUE;
return FALSE;  
}

int nSend(SOCKET s, const char *buf, int len,int flags){
UnHookFunction("ws2_32.dll", "send", hook);


int result = send(s,buf,len,flags);


  myfile.open ("C:\\tmp\\log.txt",ios::app | ios::binary);
  myfile << buf;
  myfile.close();




HookFunction("ws2_32.dll", "send", (LPVOID*) nSend, hook);
return result;
} 

int nRecv(SOCKET s, char* buf, int len, int flags)
{
    UnHookFunction("ws2_32.dll", "recv", hook2);
    DWORD tmp;

    len = recv(s, buf, len, flags);

    if (len > 0)
    {

        myfile2.open ("C:\\tmp\\log.txt",ios::app | ios::binary);
        myfile2 << buf;
        myfile2.close();
    }
   HookFunction("ws2_32.dll", "recv", (LPVOID*) nRecv, hook2);
    return len;
}
void fun(){ // <-- this is called after the DLL has been injected
HookFunction("ws2_32.dll", "send", (LPVOID*) nSend, hook);
HookFunction("ws2_32.dll", "recv", (LPVOID*) nRecv, hook2);
}

BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
{
switch (ul_reason_for_call)
{
case DLL_PROCESS_ATTACH:

case DLL_THREAD_ATTACH:
case DLL_THREAD_DETACH:
case DLL_PROCESS_DETACH:
break;
}
return TRUE;
}

This works in some cases and in some it doesnt. If i inject it into filezilla ftp it works like a charm and writes everything that is send or recieved to a file.

But on nearly all other programms (internet explorer, firefox usw.) it just writes some bytes to the file and then the process crashes...

Has anyone an idea what is going wrong?

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