Launch a No Elevated Process from an Elevated Process in an easy way (Win32 API)

dinkumoil

You have to provide the fully qualified path to Calc.exe/Notepad++.exe.

donho

You have to provide the fully qualified path to Calc.exe/Notepad++.exe.

Yes I did. The following code doesn’t work neither:

case IDM_FILE_NEW:
{
	//fileNew();
	::ShellExecuteA(NULL, "open", "explorer.exe", "C:\\sources\\notepad-plus-plus\\PowerEditor\\bin\\notepad++.exe -multiInst", "C:\\sources\\notepad-plus-plus\\PowerEditor\\bin\\", SW_SHOW);
}
break;

donho

Hmm…
The following code works :
ShellExecute(nullptr, L"open", L"explorer.exe", L"c:\\windows\\system32\\calc.exe", nullptr, SW_SHOW);

SinghRajenM

@donho

@donho said:

@dinkumoil said:

You have to provide the fully qualified path to Calc.exe/Notepad++.exe.

Yes I did. The following code doesn’t work neither:
case IDM_FILE_NEW:
{
	//fileNew();
	::ShellExecuteA(NULL, "open", "explorer.exe", "C:\\sources\\notepad-plus-plus\\PowerEditor\\bin\\notepad++.exe -multiInst", "C:\\sources\\notepad-plus-plus\\PowerEditor\\bin\\", SW_SHOW);
}
break;

As you know ShellExecute parameters,
Command/operation => “open”
Command Location/File => “explorer.exe”
Command Parameters => “C:\sources\notepad-plus-plus\PowerEditor\bin\notepad++.exe -multiInst”

So here problem is command parameter which includes another command parameter. Try without “-multiInst”. It should work.

dinkumoil

@donho

In case it is important for you to be able to call Notepad++ with command line arguments - I’ve implemented the algorithm from my 2nd MSDN link provided above in C and wrapped it in a small demo program.

It can start another program with the user rights of the desktop shell process if itself is elevated.
It can start another program with the same user rights that itself runs under if it is not elevated.
It can start another program with parameters.

Of course, it is not an oneliner and you have to change the implementation of error handling. The GetFullPath routine is not necessary.

I compiled it with MinGW. It has to be linked against Advapi32.lib and Kernel32.lib.

#define _WIN32_WINNT 0x0501
#define WIN32_LEAN_AND_MEAN
#define STRICT 1

#define _UNICODE
#define UNICODE

#include <sdkddkver.h>


/*******************************************************************************
Includes
*******************************************************************************/

#include <windows.h>

#include <stdlib.h>
#include <stdio.h>



/*******************************************************************************
Prototypes
*******************************************************************************/

BOOL   RunAsDesktopUser (LPCWSTR szApp, LPWSTR szCmdLine, LPCWSTR szCurrDir, STARTUPINFO *si, PROCESS_INFORMATION *pi);
BOOL   RunLoweredProcess(LPCWSTR szApp, LPWSTR szCmdLine, LPCWSTR szCurrDir, STARTUPINFO *si, PROCESS_INFORMATION *pi);
BOOL   RunProcess       (LPCWSTR szApp, LPWSTR szCmdLine, LPCWSTR szCurrDir, STARTUPINFO *si, PROCESS_INFORMATION *pi);
BOOL   SetPrivilege     (HANDLE hProcessToken, LPCWSTR lpszPrivilege, BOOL bEnablePrivilege);
BOOL   IsElevatedToken  (HANDLE hProcessToken);
LPWSTR GetFullPath      (LPCWSTR szFilePath);




/*******************************************************************************
Main program
*******************************************************************************/

int wmain(int argc, WCHAR *argv[])
{
  LPWSTR              fullPath    = NULL;
  LPWSTR              commandLine = NULL;
  STARTUPINFO         si          = {0};
  PROCESS_INFORMATION pi          = {0};

  si.cb          = sizeof(si);
  si.dwFlags     = STARTF_USESHOWWINDOW;
  si.wShowWindow = SW_SHOWNORMAL;

  if ((fullPath = GetFullPath(L"%ProgramFiles(x86)%\\Notepad++\\notepad++.exe")) == NULL)
  {
    wprintf(L"File not found\n");
    goto cleanup;
  }

  commandLine = calloc(wcslen(fullPath) + 14, sizeof(*fullPath));
  wsprintf(commandLine, L"\"%s\" %s", fullPath, L"-multiInst");

  if (RunAsDesktopUser(fullPath, commandLine, NULL, &si, &pi))
  {
    WaitForSingleObject(pi.hProcess, INFINITE);

    if (pi.hThread != NULL)
      CloseHandle(pi.hThread);

    if (pi.hProcess != NULL)
      CloseHandle(pi.hProcess);
  }

cleanup:
  free(fullPath);
  free(commandLine);

  return 0;
}


BOOL RunAsDesktopUser(LPCWSTR szApp, LPWSTR szCmdLine, LPCWSTR szCurrDir,
                      STARTUPINFO *si, PROCESS_INFORMATION *pi)
{
  BOOL   bRetVal       = FALSE;
  HANDLE hProcessToken = NULL;

  // Retrieve process token of own process
  if (!OpenProcessToken(GetCurrentProcess(),
                        TOKEN_QUERY
                         | TOKEN_ADJUST_PRIVILEGES,
                        &hProcessToken))
  {
    wprintf(L"OpenProcessToken failed, error code: %u\n", GetLastError());
    goto cleanup;
  }

  // Check if own process is elevated
  if (!IsElevatedToken(hProcessToken))
  {
    // Run process with user rights of own process
    if (!(bRetVal = RunProcess(szApp, szCmdLine, szCurrDir, si, pi)))
      goto cleanup;
  }
  else
  {
    // Add privilege SE_INCREASE_QUOTA_NAME to own process token
    if (!(bRetVal = SetPrivilege(hProcessToken, SE_INCREASE_QUOTA_NAME, TRUE)))
      goto cleanup;

    // Run process with user rights of desktop shell process
    if (!(bRetVal = RunLoweredProcess(szApp, szCmdLine, szCurrDir, si, pi)))
      goto cleanup;
  }

  bRetVal = TRUE;

cleanup:
  CloseHandle(hProcessToken);

  return bRetVal;
}


BOOL RunProcess(LPCWSTR szApp, LPWSTR szCmdLine, LPCWSTR szCurrDir,
                STARTUPINFO *si, PROCESS_INFORMATION *pi)
{
  // Start process with user rights of own process
  if (!CreateProcess(szApp,
                     szCmdLine,
                     (LPSECURITY_ATTRIBUTES) NULL,
                     (LPSECURITY_ATTRIBUTES) NULL,
                     FALSE,
                     0,
                     (LPVOID) NULL,
                     szCurrDir,
                     si,
                     pi))
  {
    wprintf(L"CreateProcess failed, error code: %u\n", GetLastError());
    return FALSE;
  }

  return TRUE;
}


BOOL RunLoweredProcess(LPCWSTR szApp, LPWSTR szCmdLine, LPCWSTR szCurrDir,
                       STARTUPINFO *si, PROCESS_INFORMATION *pi)
{
  BOOL   bRetVal            = FALSE;
  HWND   hShellWnd          = NULL;
  DWORD  dwShellProcessID   = 0;
  HANDLE hShellProcess      = NULL;
  HANDLE hShellProcessToken = NULL;
  HANDLE hPrimaryToken      = NULL;

  // Retrieve handle of desktop shell window
  if ((hShellWnd = GetShellWindow()) == NULL)
  {
    wprintf(L"GetShellWindow failed\n");
    goto cleanup;
  }

  // Retrieve process id of desktop shell window
  GetWindowThreadProcessId(hShellWnd,
                           &dwShellProcessID);

  if (dwShellProcessID == 0)
  {
    wprintf(L"GetWindowThreadProcessId failed\n");
    goto cleanup;
  }

  // Retrieve process handle of desktop shell process
  hShellProcess = OpenProcess(PROCESS_QUERY_INFORMATION,
                              FALSE,
                              dwShellProcessID);

  if (hShellProcess == NULL)
  {
    wprintf(L"OpenProcess failed, error code: %u\n", GetLastError());
    goto cleanup;
  }

  // Retrieve process token of desktop shell process
  if (!OpenProcessToken(hShellProcess,
                        TOKEN_DUPLICATE,
                        &hShellProcessToken))
  {
    wprintf(L"OpenProcessToken failed, error code: %u\n", GetLastError());
    goto cleanup;
  }

  // Duplicate process token of desktop shell process to a primary token
  if (!DuplicateTokenEx(hShellProcessToken,
                        TOKEN_QUERY
                         | TOKEN_DUPLICATE
                         | TOKEN_ASSIGN_PRIMARY
                         | TOKEN_ADJUST_DEFAULT
                         | TOKEN_ADJUST_SESSIONID,
                        NULL,
                        SecurityImpersonation,
                        TokenPrimary,
                        &hPrimaryToken))
  {
    wprintf(L"DuplicateTokenEx failed, error code: %u\n", GetLastError());
    goto cleanup;
  }

  // Start process with user rights of desktop shell process
  if (!CreateProcessWithTokenW(hPrimaryToken,
                               0,
                               szApp,
                               szCmdLine,
                               0,
                               (LPVOID) NULL,
                               szCurrDir,
                               si,
                               pi))
  {
    wprintf(L"CreateProcessWithToken failed, error code: %u\n", GetLastError());
    goto cleanup;
  }

  bRetVal = TRUE;

cleanup:
  CloseHandle(hShellProcessToken);
  CloseHandle(hPrimaryToken);
  CloseHandle(hShellProcess);

  return bRetVal;
}


BOOL IsElevatedToken(HANDLE hProcessToken)
{
  DWORD elevationType  = 0;
  DWORD dwReturnLength = 0;

  if (!GetTokenInformation(hProcessToken,
                           TokenElevationType,
                           &elevationType,
                           sizeof(elevationType),
                           &dwReturnLength))
  {
    wprintf(L"GetTokenInformation failed, error code: %u", GetLastError());
    return FALSE;
  }
  else
  {
    switch (elevationType)
    {
      case TokenElevationTypeDefault:
        return FALSE;

      case TokenElevationTypeLimited:
        return FALSE;

      case TokenElevationTypeFull:
        return TRUE;

      default:
        return FALSE;
    }
  }
}


BOOL SetPrivilege(HANDLE hProcessToken, LPCWSTR lpszPrivilege, BOOL bEnablePrivilege)
{
  TOKEN_PRIVILEGES tp   = {0};
  LUID             luid = {0};

  if (!LookupPrivilegeValue((LPCWSTR) NULL,
                            lpszPrivilege,
                            &luid))
  {
    wprintf(L"LookupPrivilegeValue, failed, error code: %u\n", GetLastError() );
    return FALSE;
  }

  tp.PrivilegeCount           = 1;
  tp.Privileges[0].Luid       = luid;
  tp.Privileges[0].Attributes = (bEnablePrivilege ? SE_PRIVILEGE_ENABLED : 0);

  if (!AdjustTokenPrivileges(hProcessToken,
                             FALSE,
                             &tp,
                             0,
                             (PTOKEN_PRIVILEGES) NULL,
                             (PDWORD) NULL))
  {
    wprintf(L"AdjustTokenPrivileges failed, error code: %u\n", GetLastError() );
    return FALSE;
  }

  if (GetLastError() != ERROR_SUCCESS)
  {
    wprintf(L"AdjustTokenPrivileges failed to set the specified privilege.\n");
    return FALSE;
  }

  return TRUE;
}


LPWSTR GetFullPath(LPCWSTR szFilePath)
{
  LPWSTR szPath    = (LPWSTR) szFilePath;
  BOOL   bFreePath = FALSE;
  LPWSTR szBuf     = NULL;
  DWORD  dwBufLen  = 0;
  DWORD  nCCh      = 0;

  // Expand environment variables
  do
  {
    szBuf = (LPWSTR) realloc(szBuf, dwBufLen * sizeof(*szBuf));
    nCCh  = ExpandEnvironmentStrings(szPath,
                                     szBuf,
                                     dwBufLen);

    if (nCCh == 0)        break;
    if (nCCh == dwBufLen) break;

    dwBufLen = nCCh;
  } while (TRUE);

  if (nCCh > 0)
  {
    szPath    = szBuf;
    bFreePath = TRUE;
  }

  // Search file name in PATH and current directory
  szBuf    = NULL;
  dwBufLen = 0;

  do
  {
    szBuf = (LPWSTR) realloc(szBuf, dwBufLen * sizeof(*szBuf));
    nCCh  = SearchPath((LPCWSTR) NULL,
                       szPath,
                       (LPCWSTR) NULL,
                       dwBufLen,
                       szBuf,
                       NULL);

    if (nCCh == 0)       break;
    if (nCCh < dwBufLen) break;

    dwBufLen = nCCh;
  } while (TRUE);

  if (bFreePath)
    free(szPath);

  if (nCCh > 0)
    return szBuf;
  else
    return NULL;
}

donho

@dinkumoil
Wow, it’s miles and miles of codes for just preventing from elevation ! I’ll try firstly One Line solution of @SinghRajenM .
Thank you.

dinkumoil

@donho said:

I’ll try firstly One Line solution of @SinghRajenM .

Of course.

Wow, it’s miles and miles of codes

It’s not that bad, the absolutely core functionality is about to 90 lines of code which you can shorten even more.

for just preventing from elevation !

It’s not a “just”. For this functionality there is no ready-to-use Windows API. That the ShellExecute one-liner does the job is an undocumented feature and relies on the current implementation of Explorer.exe. And with this method it is not possible to start the unelevated process with parameters.

donho

The solution of @SinghRajenM is tested and works fine! Merged into the master of wingup:
https://github.com/notepad-plus-plus/wingup/commit/af34920693261307d34bb530622e6d70cbe875d2

Thank you @SinghRajenM for your hint and your solution (again, besides of NSIS).

dinkumoil

@donho

I have tested the ShellExec one-liner solution more thoroughly and noticed the following:

If a user wants to install a plugin, an UAC dialog pops up and requests for confirmation. After the plugin is installed Notepad++ restarts. So far so good.

If the user now wants to install another plugin, the plugin gets installed without an UAC dialog poping up, it is just done and Notepad++ restarts after that.

It seems like though Notepad++ obviously runs with user rights, it actually does not.

dinkumoil

@donho

Sorry, I was wrong. I have tested with the wrong debug binary which hadn’t contained your last ShellExecute patch. Sorry for the inconvenience.