Why won't my program inject my .dll properly? - c++

Question

Been stuck for a few hours making a (simple) dll injector that takes a .dll file and a process as arguments and then injects said .dll into the process, and I'm about to start tearing my hair out.
It doesn't function properly, and for no obvious reason either. The dll simply won't load into the process, but without any error messages being displayed. I did the exact same thing but with ANSI functions instead of Unicode and it worked like a charm, which after some testing is leading me to believe it's PROBABLY a problem with the file path not being loaded properly but I have no idea why.
I've attached my entire source code below and added some comments to hopefully clarify somewhat. And like I said, if I'm right, then the important part should start somewhere around:
//Get the full path of our dll and store it in a variable
Help a bro out.
#include <iostream>
#include <Windows.h>
#include <TlHelp32.h>
using namespace std;
int main()
{
HANDLE hSnapshot, hProc = NULL;
PROCESSENTRY32 PE32;
PE32.dwSize = sizeof(PROCESSENTRY32);
WCHAR injProcName[100] = {NULL}, injDllName[100] = {NULL};
//Let user input options
cout << "Dll injector started!" << endl << "Please enter the name of the dll you would like to inject: ";
wcin >> injDllName;
cout << "Enter the name of the target process: ";
wcin >> injProcName;
//Create snapshot
hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, NULL);
Process32First(hSnapshot, &PE32);
//Load the first process into PE32 and loop to see if target process is running
do {
if(wcscmp(PE32.szExeFile, injProcName) == 0) {
wcout << PE32.szExeFile << " found!" << endl;
wcout << "Attempting to open " << injProcName << ".." << endl;
hProc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, PE32.th32ProcessID);
if(!hProc)
{
cout << "Failed to open process!" << endl;
return 1;
}
break;
}
}
while(Process32Next(hSnapshot, &PE32));
if(!hProc) {
cout << "Unable to locate process!" << endl;
return 1;
}
cout << "Process successfully opened!" << endl;
//Get the full path of our dll and store it in a variable
WCHAR DllPath[MAX_PATH] = {NULL};
GetFullPathName(injDllName, MAX_PATH, DllPath, NULL);
wcout << DllPath << endl;
//Allocate memory in target process
cout << "Allocating memory.." << endl;
LPVOID DllMemAddr = VirtualAllocEx(hProc,
NULL,
wcslen(DllPath),
MEM_COMMIT|MEM_RESERVE,
PAGE_READWRITE);
//Write our path into target process memory
wcout << "Writing dll to target process.." << endl;
WriteProcessMemory(hProc,
DllMemAddr,
DllPath,
wcslen(DllPath),
NULL);
//Get the memory address of LoadLibraryW
LPVOID LoadAddr = GetProcAddress(GetModuleHandle(L"kernel32.dll"), "LoadLibraryW");
//Finally, start a new thread with the address of LoadLibraryW and our dll path as argument
cout << "Executing dll in remote process.." << endl;
CreateRemoteThread(hProc,
NULL,
NULL,
(LPTHREAD_START_ROUTINE)LoadAddr,
DllMemAddr,
NULL,
NULL);
cout << "Dll sucessfully injected!" << endl;
cin.get();
return 0;
}

Answer 1

wcslen returns length in wchar_t units. But VirtualAllocEx and WriteProcessMemory receive a length in byte units. So you only write half the string, because wchar_t is two bytes wide. And you did not write the null terminator.
You need to pass (wcslen(DllPath)+1)*sizeof(wchar_t).
Incidentally, your ANSI code was probably broken too because, presumably, it also missed the null terminator. But you probably got away with it by chance.
A little error checking would not go amis, while we are in the business of looking at your code. And initialising DllPath is a little pointless when you follow it with the call to GetFullPathName.