c++ - How to launch non-elevated administrator process from elevated administrator context on Windows 10?

Question

Is there an easy way to create a normal administrator process (not elevated) from an elevated administrator process? I am using Windows 10 pro. The situation is that I are trying to make some kind of deploy tools. The tool will be running with elevated administrator context in order to write files into "Program Files" ( and access other privileged resources). But one of the step is to invoke an external program. That program seems to have strange issues when created with elevated administrator privilege. We have to launch it in a non-elevated administrator context. I tried the approach in an MSDN blog, https://blogs.msdn.microsoft.com/winsdk/2010/05/31/dealing-with-administrator-and-standard-users-context it does not work at all.

Answer 1

Raymond Chen addressed this exact question on his "Old New Thing" blog on MSDN:

How can I launch an unelevated process from my elevated process and vice versa?

Going the other way is trickier. For one thing, it's really hard to munge your token to remove the elevation nature properly. And for another thing, even if you could do it, it's not the right thing to do, because the unelevated user may be different from the elevated user.

...

The solution here is to go back to Explorer and ask Explorer to launch the program for you. Since Explorer is running as the original unelevated user, the program (in this case, the Web browser) will run as Bob. This is also important in the case that the handler for the file you want to open runs as an in-process extension rather than as a separate process, for in that case, the attempt to unelevate would be pointless since no new process was created in the first place. (And if the handler for the file tries to communicate with an existing unelevated copy of itself, things may fail because of UIPI.)

Raymond uses IShellFolderViewDual and IShellDispatch2 to accomplish that ¹:

#define STRICT
#include <windows.h>
#include <shldisp.h>
#include <shlobj.h>
#include <exdisp.h>
#include <atlbase.h>
#include <stdlib.h>

// FindDesktopFolderView incorporated by reference

void GetDesktopAutomationObject(REFIID riid, void **ppv)
{
 CComPtr<IShellView> spsv;
 FindDesktopFolderView(IID_PPV_ARGS(&spsv));
 CComPtr<IDispatch> spdispView;
 spsv->GetItemObject(SVGIO_BACKGROUND, IID_PPV_ARGS(&spdispView));
 spdispView->QueryInterface(riid, ppv);
}

void ShellExecuteFromExplorer(
    PCWSTR pszFile,
    PCWSTR pszParameters = nullptr,
    PCWSTR pszDirectory  = nullptr,
    PCWSTR pszOperation  = nullptr,
    int nShowCmd         = SW_SHOWNORMAL)
{
 CComPtr<IShellFolderViewDual> spFolderView;
 GetDesktopAutomationObject(IID_PPV_ARGS(&spFolderView));
 CComPtr<IDispatch> spdispShell;
 spFolderView->get_Application(&spdispShell);

 CComQIPtr<IShellDispatch2>(spdispShell)
    ->ShellExecute(CComBSTR(pszFile),
                   CComVariant(pszParameters ? pszParameters : L""),
                   CComVariant(pszDirectory ? pszDirectory : L""),
                   CComVariant(pszOperation ? pszOperation : L""),
                   CComVariant(nShowCmd));
}

int __cdecl wmain(int argc, wchar_t **argv)
{
 if (argc < 2) return 0;

 CCoInitialize init;
 ShellExecuteFromExplorer(
    argv[1],
    argc >= 3 ? argv[2] : L"",
    argc >= 4 ? argv[3] : L"",
    argc >= 5 ? argv[4] : L"",
    argc >= 6 ? _wtoi(argv[5]) : SW_SHOWNORMAL);

 return 0;
}

Open an elevated command prompt, and then run this program in various ways.

scratch http://www.msn.com/
Open an unelevated Web page in the user's default Web browser.

scratch cmd.exe "" C:Users "" 3
Open an unelevated command prompt at C:Users, maximized.

scratch C:PathToImage.bmp "" "" edit
Edit a bitmap in an unelevated image editor

¹: the implementation of FindDesktopFolderView() is in another article on Raymond's blog:

Manipulating the positions of desktop icons:

void FindDesktopFolderView(REFIID riid, void **ppv)
{
 CComPtr<IShellWindows> spShellWindows;
 spShellWindows.CoCreateInstance(CLSID_ShellWindows);

 CComVariant vtLoc(CSIDL_DESKTOP);
 CComVariant vtEmpty;
 long lhwnd;
 CComPtr<IDispatch> spdisp;
 spShellWindows->FindWindowSW(
     &vtLoc, &vtEmpty,
     SWC_DESKTOP, &lhwnd, SWFO_NEEDDISPATCH, &spdisp);

 CComPtr<IShellBrowser> spBrowser;
 CComQIPtr<IServiceProvider>(spdisp)->
     QueryService(SID_STopLevelBrowser,
                  IID_PPV_ARGS(&spBrowser));

 CComPtr<IShellView> spView;
 spBrowser->QueryActiveShellView(&spView);

 spView->QueryInterface(riid, ppv);
}