#include <cstdio>
#include <windows.h>
#include <tlhelp32.h>

int main( int, char *[] )
{
    PROCESSENTRY32 entry;
    entry.dwSize = sizeof(PROCESSENTRY32);

    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

    if (Process32First(snapshot, &entry) == TRUE)
    {
        while (Process32Next(snapshot, &entry) == TRUE)
        {
            if (stricmp(entry.szExeFile, "target.exe") == 0)
            {  
                HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, entry.th32ProcessID);

                // Do stuff..

                CloseHandle(hProcess);
            }
        }
    }

    CloseHandle(snapshot);

    return 0;
}

Also, if you'd like to use PROCESS_ALL_ACCESS in OpenProcess, you could try this:

#include <cstdio>
#include <windows.h>
#include <tlhelp32.h>

void EnableDebugPriv()
{
    HANDLE hToken;
    LUID luid;
    TOKEN_PRIVILEGES tkp;

    OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken);

    LookupPrivilegeValue(NULL, SE_DEBUG_NAME, &luid);

    tkp.PrivilegeCount = 1;
    tkp.Privileges[0].Luid = luid;
    tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

    AdjustTokenPrivileges(hToken, false, &tkp, sizeof(tkp), NULL, NULL);

    CloseHandle(hToken); 
}

int main( int, char *[] )
{
    EnableDebugPriv();

    PROCESSENTRY32 entry;
    entry.dwSize = sizeof(PROCESSENTRY32);

    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, NULL);

    if (Process32First(snapshot, &entry) == TRUE)
    {
        while (Process32Next(snapshot, &entry) == TRUE)
        {
            if (stricmp(entry.szExeFile, "target.exe") == 0)
            {  
                HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, entry.th32ProcessID);

                // Do stuff..

                CloseHandle(hProcess);
            }
        }
    }

    CloseHandle(snapshot);

    return 0;
}

Use CreateToolhelp32Snapshot, Process32First, and Process32Next to enumerate all of the processes.

Inside the PROCESSENTRY32 you can find a szExeFile member. You can get the process handle by calling OpenProcess with the process ID th32ProcessID within the same struct.

Once you find a process matching your exe name, you can break out of your loop and obtain the handle.

Note: If you need to enumerate EVERY process no matter what the session is, you should acquire the SE_DEBUG privilege.

At the top of your main call this:

acquirePrivilegeByName(SE_DEBUG_NAME);// SeDebugPrivilege

And here is the definition of acquirePrivilegeByName:

BOOL acquirePrivilegeByName(
                            const TCHAR     *szPrivilegeName)
{
    HANDLE          htoken;
    TOKEN_PRIVILEGES    tkp;
    DWORD           dwerr;

    if (szPrivilegeName == NULL)
    {
        SetLastError(ERROR_INVALID_PARAMETER);
        return FALSE;
    }

    if (!LookupPrivilegeValue(NULL, szPrivilegeName, &(tkp.Privileges[0].Luid)))
        return FALSE;

    tkp.PrivilegeCount = 1;
    tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

    if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &htoken))
        return FALSE;

    if (!AdjustTokenPrivileges(htoken, FALSE, &tkp, 0, NULL, NULL) ||
        GetLastError() != ERROR_SUCCESS)    // may equal ERROR_NOT_ALL_ASSIGNED
    {
        dwerr = GetLastError();
        CloseHandle(htoken);
        SetLastError(dwerr);
        return FALSE;
    }

    CloseHandle(htoken);
    SetLastError(ERROR_SUCCESS);

    return TRUE;
} //acquirePrivilegeByName()

In addition to what I said above, there is an example on how to use the above Win32 API here.

OpenProcess(PROCESS_ALL_ACCESS, TRUE, procId);

You'll need to verify that you're using a valid process ID, and that you're permitted the access rights you request from the process.

Even if you do move the handle from one process to the other. You still have the issue of the handle values possibly being meaningful only within the process that originally opened them.

If you don't use OpenProcess(), you'll end up using DuplicateHandle().

See the here:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms724251(v=vs.85).aspx