Why does Group Policy block to create ISensorManger instance?

Question

I have a Surface Pro 3, running Window 10 Pro, version 1803. One of the things that I do with this tablet is play around with the new API and programming features that Microsoft provides.

Recently, I was test some small toy programs using the sensor API to get a feel for them. I have a small program that enumerates all the sensors on the device, worked find on an older surface tablet, running 8.1. However when I brought the source code over to the Surface Pro, recompiled it and when to run it I got the error:

"Unable to CoCreateInstance() on SensorManger error: This program is blocked by group policy. For more information contact your system administrator"

I get this error regardless if I run as myself or as an administrator. Due to this being test code, I never bother to do anything robust error handling so this error does not cause the program to abort, so the program continues and shows a GUI with no sensor discovered obviously.

This device is a personal stand-alone device, not attached to a domain controller. Under developers, I have selected "sideload apps".

My question is, how do I troubleshoot / fix the above error?

A second, related, question with this being a stand-alone computer do I really need Group Policy, and if not is there some way to disable it

Thanks

Answer 1

How do I troubleshoot / fix the above error?

Short answer: Run these two command as administrator (using reg add command):

REG ADD "HKLM\SOFTWARE\Policies\Microsoft\Windows\LocationAndSensors" /V "DisableSensors" /T REG_DWORD /D "0" /F 
REG ADD "HKCU\SOFTWARE\Policies\Microsoft\Windows\LocationAndSensors" /V "DisableSensors" /T REG_DWORD /D "0" /F 

Explanation: I used some C language with SensorManger interface. You can skip this part. A demo program:

#include <Windows.h>
#include <sensorsapi.h>

void func(void)
{
    HRESULT hRes = 0;
    ISensorManager *pSensorManager = NULL;

    hRes = CoInitialize(NULL);
    hRes = CoCreateInstance(&CLSID_SensorManager,
                            NULL,
                            CLSCTX_INPROC_SERVER,
                            &IID_ISensorManager,
                            &pSensorManager);

    hRes = pSensorManager->lpVtbl->Release(pSensorManager);
    CoUninitialize();
}

How did I find? This requires some reverse engineering idea. The CLSID_SensorManager GUID leads me to C:\Windows\System32\SensorsApi.dll file. I opened it in a disassembler. There is a function SensorsGroupPolicy::IsSensorsFeatureDisabled in that DLL file which checks both the two REG_DWORD values.

• HKLM\SOFTWARE\Policies\Microsoft\Windows\LocationAndSensors\DisableSensors is checked first which is applied for all user.
• Then HKCU\SOFTWARE\Policies\Microsoft\Windows\LocationAndSensors\DisableSensors is checked which is applied for current logged in user.
• The setting can be disabled in Local Group Policy editor → Computer Configuration → Administrative Templates → Windows Components → Location and Sensors → Turn off sensors → Disabled. But the registry method is instantaneous.