Compare username of running program to username logged into Windows - c++

Question

I've tried to implement a program which controls if the name of the user logged into the computer and the user who ran a program is the same, but I think I've done something wrong. The name of the usernamed logged works, but not the one to get the user who ran the program.
#include <Windows.h>
#include <iostream>
#include <stdlib.h>
#include <Lmcons.h>
#include <tchar.h>
#include <stdio.h>
#define INFO_BUFFER_SIZE 32767
using namespace std;
void Test() {
WCHAR UsernameSSR[INFO_BUFFER_SIZE];
TCHAR UsernameWindows[INFO_BUFFER_SIZE];
DWORD bufCharCountWindows = INFO_BUFFER_SIZE;
DWORD bufCharCountSSR = INFO_BUFFER_SIZE;
GetUserName(UsernameWindows, &bufCharCountWindows);
GetUserNameW(UsernameSSR, &bufCharCountSSR);
cout << UsernameWindows << " and " << UsernameSSR;
return;
}

Answer 1

GetUserName() is just a preprocessor macro that maps to either GetUserNameA() (ANSI) or GetUserNameW() (Unicode), depending on your project setup. Either way, GetUserName(A|W) returns the username currently associated with the calling thread, which in your example is also the username that is used to run the program. No mixing of GetUserNameA() and GetUserNameW() together will get you the results you want, because they are going to return the same username just in different character encodings.
To get the username that is logged into Windows itself, you need a different function, such as WTSQuerySessionInformation() (A or W variant), eg:
#include <iostream>
#include <Windows.h>
#include <wtsapi32.h>
#include <Lmcons.h>
void Test()
{
WCHAR UsernameSSR[UNLEN+1];
DWORD bufCharCountSSR = UNLEN+1;
if (GetUserNameW(UsernameSSR, &bufCharCountSSR))
std::wcout << L"UsernameSSR: " << UsernameSSR << std::endl;
else
std::wcout << L"Error getting UserNameSSR" << std::endl;
// alternatively, use GetUserNameExW() instead...
LPWSTR UsernameWindows;
DWORD bufByteCountWindows;
if (WTSQuerySessionInformationW(WTS_CURRENT_SERVER_HANDLE, WTS_CURRENT_SESSION, WTSUserName, &UsernameWindows, &bufByteCountWindows))
{
LPWSTR Domain;
DWORD bufByteCountDomain;
std::wcout << L"UsernameWindows: ";
if (WTSQuerySessionInformationW(WTS_CURRENT_SERVER_HANDLE, WTS_CURRENT_SESSION, WTSDomainName, &Domain, &bufByteCountDomain))
{
if (*Domain)
std::wcout << Domain << L"\\";
WTSFreeMemory(Domain);
}
std::wcout << UsernameWindows << std::endl;
WTSFreeMemory(UsernameWindows);
}
else
std::wcout << L"Error getting UserNameWindows" << std::endl;
// alternatively, query WTSQuerySessionInformation() for WTSSessionInfo, which
// returns both Domain and UserName in a single call, amongst other pieces of info...
}
That being said, comparing username strings is not the best way to determine whether your program is being run by the same user that is logged into Windows.
For instance, another way would be to obtain the Security Identifier (SID) of the user who is running the program and then compare it to the SID of the user that is logged into Windows using EqualSid().
Getting the SID of the calling process is easy: you can use GetCurrentProcessId(), OpenProcessToken(TOKEN_QUERY), and GetTokenInformation(TokenUser).
However, getting the SID of the logged in Windows session is a bit trickier. You can either:
get the Session ID of the logged in user, such as with ProcessIdToSessionId() or QueryTokenInformation(TokenSessionId) for the parent process that spawned your program (to find the parent process ID, use CreateToolhelp32Snapshot(), Process32First(), and Process32Next()), and then pass that Session ID to WTSQueryUserToken(), and then query the SID from that token. The gotcha is that WTSQueryUserToken() can only be called from a service that is running under the LocalSystem account, so you will have to write such a service and delegate to it via an IPC mechanism of you choosing.
retrieve the domain\username of the user session as described further above, and then use WMI to query the Win32_UserAccount table for that specific user and read its Sid property, then parse the SID into its binary form using ConvertStringSidToSid().

Answer 2

You missed , after first parameter (name):
GetUserNameA((LPSTR)name(LPDWORD) & size)
Also, why did you use GetUserName and not GetUserNameW? In some cases GetUserName will be same as GetUserNameA, so if you try to get the difference write GetUserNameW directly.