C++ - Unresolved External in DLL Injector [duplicate] - c++

Question

This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 6 years ago.
I can't really see the reason I am getting this error, I have had a look arround and apparently it's something to do with defining a function that does nothing? I can't really tell what the issue is here unfortunately so any help would be appreciated.
Here is my source code:
main.cpp
#include <Windows.h>
#include <tlhelp32.h>
#include <shlwapi.h>
#include <conio.h>
#include <stdio.h>
#include <iostream>
using namespace std;
#define WIN32_LEAN_AND_MEAN
#define CREATE_THREAD_ACCESS (PROCESS_CREATE_THREAD | PROCESS_QUERY_INFORMATION | PROCESS_VM_OPERATION | PROCESS_VM_WRITE | PROCESS_VM_READ)
BOOL Inject(DWORD pID, const char * DLL_NAME);
DWORD GetTargetThreadIDFromProcName(const char * ProcName);
using namespace std;
char buf[MAX_PATH];
LPVOID RemoteString, LoadLib;
HANDLE Proc;
DWORD pID;
__int32 main()
{
pID = GetTargetThreadIDFromProcName("Program.exe");
buf[MAX_PATH] = {0};
GetFullPathName("DLL.dll", MAX_PATH, buf, NULL);
if(!Inject(pID, buf)) cout << ("Failed to inject!\n\n\n");
system("pause");
return 0;
}
BOOL Inject(DWORD pID, const char * DLL_NAME)
{
char buf[50] = {0};
if(!pID) return false;
Proc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pID);
if(!Proc) return false;
LoadLib = (LPVOID)GetProcAddress(GetModuleHandle("kernel32.dll"), "LoadLibraryA");
RemoteString = (LPVOID)VirtualAllocEx(Proc, NULL, strlen(DLL_NAME), MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
WriteProcessMemory(Proc, (LPVOID)RemoteString, DLL_NAME, strlen(DLL_NAME), NULL);
CreateRemoteThread(Proc, NULL, NULL, (LPTHREAD_START_ROUTINE)LoadLib, (LPVOID)RemoteString, NULL, NULL);
CloseHandle(Proc);
return true;
}
DWORD GetTargetThreadIDFromProcName(const char * ProcName)
{
PROCESSENTRY32 pe;
HANDLE thSnapShot;
BOOL retval, ProcFound = false;
thSnapShot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
if(thSnapShot == INVALID_HANDLE_VALUE) return false;
pe.dwSize = sizeof(PROCESSENTRY32);
retval = Process32First(thSnapShot, &pe);
while(retval)
{
if(StrStrI(pe.szExeFile, ProcName)) return pe.th32ProcessID;
retval = Process32Next(thSnapShot, &pe);
}
return 0;
}
The error I am getting is the following:
main.obj
unresolved external symbol __imp__StrStrIA#8 referenced in function "unsigned long __cdecl GetTargetThreadIDFromProcName(char const *)" (?GetTargetThreadIDFromProcName##YAKPBD#Z)
Injector.exe
1 unresolved externals
Any solutions or just some help on understanding why this occurs would be great!

Answer 1

As mentioned in the comments, it looks like you are not linking with shlwapi.lib. You need to do this in order to call StrStrI.