Simple Remote Thread DLL Injection Not Working

Posted on 2008-10-28
Last Modified: 2012-06-21
Download VS2008 project at -- or use the code directly from: -- if using the site from the link, make sure to download his 1KB zip file with two functions not posted in his thread.

Any help would be MUCH appreciated.  I've spent most of today beating my head against a wall, getting nowhere.  I have many years of programming experience, but this is my first attempt at a Windows app, and it's driving me nuts!

Only two changes, both seem necessary to the code on the thread (changes are made in the project downloadable at :
(1) He accidentally (I think) typed taskmgr where he meant notepad.  Changed 'hProcess = GetProcessHandle("taskmgr.exe")' where he meant '...notepad.exe'
(2) FindWindow() at least in VS08 has two paramters, LPCSTR lpClassName and LPCSTR lpWindowName.  So, I tried both 'FindWindow("Untitled - Notepad", NULL)' and 'FindWindow(NULL, "Untitled - Notepad")'.  I'm virtually certain "Untitled - Notepad" is for lpWindowName, but I tried both just in case.

Oh, I also threw in a MessageBox that states the Dll injection was successful, so there isn't just one upon an error.

The program message box'es success, but the injected dll never seems to execute.  Even with a MessageBox as the first instruction in DllMain, nothing seems to happen.

I'm running on Vista, if it matters.  Changing the attached project to release form (and moving both solutions over to multi-byte character sets) and copying the .exe and .dll to an XP machine is even worse.  The .exe eats up a ton of memory and brings my system to its knees.
Question by:darlingm2
  • 2
LVL 19

Accepted Solution

drichards earned 500 total points
ID: 22828577
You probably don't have permission to open the notepad process with PROCESS_ALL_ACCESS.  I added a few lines of code to acquire the correct access and it seems to work.  The new GetProcessHandle function is shown below.

Also, I had to add a full path to Dll.dll so it would load correctly, and your logic to print success/fail of the injection is backwards, I think.  Should be "if (!DllInject..."
HANDLE GetProcessHandle(LPSTR szExeName)
	HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPALL, 0);
    HANDLE phandle = NULL;
	if(Process32First(hSnapshot, &Pc)){
			if(!strcmp(Pc.szExeFile, szExeName)) {
                HANDLE token;
                if (OpenProcessToken(GetCurrentProcess(), TOKEN_ALL_ACCESS, &token))
                    LUID luid;
                    if (LookupPrivilegeValue(NULL, SE_DEBUG_NAME, &luid))
                        TOKEN_PRIVILEGES tp;
                        tp.PrivilegeCount = 1;
                        tp.Privileges[0].Luid = luid;
                        tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
                        if (AdjustTokenPrivileges(token, FALSE, &tp, sizeof(TOKEN_PRIVILEGES), NULL, NULL))
            				phandle = OpenProcess(PROCESS_ALL_ACCESS, TRUE, Pc.th32ProcessID);
                if (phandle == NULL)
                    DWORD err = GetLastError();
                    err = 0;
		}while(Process32Next(hSnapshot, &Pc));
	return phandle;

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Author Comment

ID: 22831950
Thank you very much for your time on this.  Your version of GetProcessHandle() works, and puts the addition into Notepad.  You're also right also about the original writer's logic on the message box being incorrect.  All this time it was not giving an error when it should have been for me.
LVL 19

Expert Comment

ID: 34256118
After coming across the same article darlingm2 mentioned, I found the above code from drichards very useful, so thanks drichards for that!

I also spent some time figuring out why my code would not work in Unicode mode: for future searchers I post the simple changes I made here.  Basically it is about modifying DllInject() to writ ethe correct number of bytes out within WriteProcessMemory...
LVL 19

Expert Comment

ID: 34256120
BOOL DllInject(HANDLE hProcess, LPCTSTR lpszDllPath)
      HMODULE hmKernel = GetModuleHandle(_T("Kernel32"));//heres the DLL
      if(hmKernel == NULL || hProcess == NULL) return FALSE;
      int nBytes = ( _tcslen(lpszDllPath) + 1 ) * sizeof ( TCHAR );
      LPVOID lpvMem = VirtualAllocEx(hProcess, NULL, nBytes, MEM_COMMIT, PAGE_READWRITE);
      BOOL bRet = WriteProcessMemory(hProcess, lpvMem, lpszDllPath, nBytes, NULL);
      DWORD dwWaitResult, dwExitResult = 0;
#ifdef _UNICODE
      HANDLE hThread = CreateRemoteThread(hProcess, NULL, 0, (LPTHREAD_START_ROUTINE)GetProcAddress(hmKernel, "LoadLibraryW"), lpvMem, 0, NULL);
      HANDLE hThread = CreateRemoteThread(hProcess, NULL, 0, (LPTHREAD_START_ROUTINE)GetProcAddress(hmKernel, "LoadLibraryA"), lpvMem, 0, NULL);
      if(hThread != NULL){
            dwWaitResult = WaitForSingleObject(hThread, 10000); // 10 seconds
            bRet = GetExitCodeThread(hThread, &dwExitResult);
            bRet = CloseHandle(hThread);
      VirtualFreeEx(hProcess, lpvMem, 0, MEM_RELEASE);
      return ((dwWaitResult != WAIT_TIMEOUT) && (dwExitResult > 0));

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