Using WMI to Extract Management Information

Environment: VC6, WMI SDK

This week I gained a little experience of WMI using, so I would share it with you. The attached application is WMI client which can connect to WMI management servers and performs some activities:

  • enumerating all instances of most populated CIMV2 classes,
  • displaying their properties (only BSTR types),
  • executing methods (for Win32_Process and Win32_OperatingSystem classes only), and
  • connecting to any computer and performing WMI login for different users and passwords.

In order to execute class object methods press the right button on selected instance and choose from pop up menu the method you want to execute.

REMEMBER the Win32_OperatingSystem methods are booting the PC, so save all your works before trying it.

Take a look at the function implementation in AcWMI.h and its cpp file. These functions manipulate the WMI interfaces and supply the following functionality. I will be glad if youll find some problems or bugs in this implementation and report to me. If you have any suggestion or question please refer to me.

Connecting to WMI namespace services (using password and username is not required for local machine).


///////////////////////////////////////////////////////////////////////
//1)	Connecting to WMI namespace services (using password and username 
//	is not required for local machine). This function returns IWbemLocator, 
//	IWbemServices interface pointers and the user error description.
///////////////////////////////////////////////////////////////////////

HRESULT	ConnectServerWMI ( OUT IWbemLocator**  ppiWmiLoc   ,
                           OUT IWbemServices** ppiWmiServ   ,
                           const CString       csNamespace   ,
                           const CString       csUsername   ,
                           const CString       csPassword   ,
                           CString&    csErrRef   )
{
   if (NULL == ppiWmiServ || NULL == ppiWmiLoc)   {
      csErrRef = _T("Invalid argument");
      return E_INVALIDARG;
   }

   HRESULT      hres;
   hres = CoCreateInstance ( CLSID_WbemLocator, 0, 
                             CLSCTX_INPROC_SERVER, IID_IWbemLocator,
                             (LPVOID *) ppiWmiLoc   );
 
    if (FAILED(hres))   {
      csErrRef = _T("Failed to create IWbemLocator object.");
      return hres;
    }

   CComBSTR bstrNamespace(csNamespace);

   if (csPassword.IsEmpty() || csUsername.IsEmpty())   
   {
      hres = (*ppiWmiLoc)->ConnectServer(bstrNamespace, NULL, NULL,
                              0, NULL, 0, 0, ppiWmiServ   );
   }
   else   
   {
      // connect server using password and username
      CComBSTR bstrUsername(csUsername), bstrPassword(csPassword);

      hres = (*ppiWmiLoc)->ConnectServer(bstrNamespace, bstrUsername, 
                              bstrPassword, 0, NULL, 0, 0, 
                              ppiWmiServ   );
   }

    if (FAILED(hres))   
   {
      (*ppiWmiLoc)->Release();

      csErrRef = _T("Failed to connect server.");
      return hres;
    }


   hres = CoSetProxyBlanket( *ppiWmiServ   , 
                          RPC_C_AUTHN_WINNT   , 
                          RPC_C_AUTHZ_NONE   , 
                          NULL, 
                          RPC_C_AUTHN_LEVEL_CALL      ,
                          RPC_C_IMP_LEVEL_IMPERSONATE   , 
                          NULL,
                          EOAC_NONE);

   if(FAILED(hres))   
   {
      (*ppiWmiLoc)->Release();
      (*ppiWmiServ)->Release();

      csErrRef = _T("Can not set proxy blank.");
      return hres;
   }

   return hres;
}
 
///////////////////////////////////////////////////////////////////////
//2)   Enumerating of all similar service instances in OS is doing by 
// EnumInstancesWMI function. This function returns IEnumWbemClassObject 
//  interface.
///////////////////////////////////////////////////////////////////////
HRESULT   EnumInstancesWMI ( IN    IWbemServices*           piWmiServ   ,
                             OUT   IEnumWbemClassObject**   ppiWmiEnum   ,
                             const CString& csInstName, CString& csErrRef   )
{   
   if (NULL == piWmiServ || NULL == ppiWmiEnum)
   {
      csErrRef = _T("Invalid argument");
      return E_INVALIDARG;
   }

   HRESULT      hres;
   CComBSTR      bstrObjectName(csInstName);

   hres = piWmiServ->CreateInstanceEnum(   bstrObjectName   ,
                                 WBEM_FLAG_RETURN_IMMEDIATELY | WBEM_FLAG_FORWARD_ONLY ,
                                 NULL   ,
                                 ppiWmiEnum);
    if (FAILED(hres))    
    {
      csErrRef.Format("Could not enumerate %s instances.", csInstName);
      return hres;
    }
   return hres;
}


///////////////////////////////////////////////////////////////////////
//3)   Error description is provided by IWbemStatusCodeText interface 
// which implemented in my GetLastErrorWMI function. This function 
// returns error description by HRESULT argument.
///////////////////////////////////////////////////////////////////////

HRESULT   GetLastErrorWMI (CString&   csErrRef, HRESULT hresErr)
{
    IWbemStatusCodeText * pStatus = NULL;

    HRESULT hres = CoCreateInstance(CLSID_WbemStatusCodeText, 0, CLSCTX_INPROC_SERVER,
                                    IID_IWbemStatusCodeText, (LPVOID *) &pStatus);
    
    if(S_OK == hres)
    {
       CComBSTR bstrError;
       hres = pStatus->GetErrorCodeText(hresErr, 0, 0, &bstrError);

       if(S_OK != hres)
         bstrError = SysAllocString(L"Get last error failed");

       USES_CONVERSION;
       csErrRef = OLE2T(bstrError);
      
       pStatus->Release();
    }

    return hres;
}

///////////////////////////////////////////////////////////////////////
//4)   Enumerating of all property names of instance is doing by 
// EnumInstPropNameWMI function. This function is returning string array 
// of all properties.
///////////////////////////////////////////////////////////////////////

HRESULT   EnumInstPropNameWMI ( IN IWbemClassObject* piappObj, 
                               OUT LPSAFEARRAY* ppsarProp   )
{   
   if (NULL == ppsarProp || NULL == piappObj)
      return E_INVALIDARG;

   // GetNames methods will create SAFEARRAY, 
   // but on entry this parameter must point to NULL
   if (NULL != *ppsarProp)   
   {
      SafeArrayDestroy(*ppsarProp);
      delete *ppsarProp;
      *ppsarProp = NULL;

      if (NULL == ppsarProp)
         return E_INVALIDARG;
   }

   HRESULT hres;
   hres = piappObj->GetNames(   NULL,
                        WBEM_FLAG_ALWAYS | WBEM_FLAG_NONSYSTEM_ONLY,
                        NULL,
                        ppsarProp);
   return hres;
}

   

///////////////////////////////////////////////////////////////////////
//5)   Another enumerating function enumerates all property names of 
// instance in SAFEARRAY type. The SAFEARRAY pointer should be NULL 
// at receiving time.
///////////////////////////////////////////////////////////////////////

HRESULT   EnumInstPropNameWMI ( IN IWbemClassObject* piappObj, 
                               OUT CStringArray& psarPropRef   )
{
   HRESULT      hres;
   SAFEARRAY*   pSafeArrProp = NULL;
   
   psarPropRef.RemoveAll();

   hres = EnumInstPropNameWMI(piappObj, &pSafeArrProp );
   
   if (WBEM_S_NO_ERROR != hres)
      return hres;

   long   lLower, lUpper;
   SafeArrayGetLBound(pSafeArrProp , 1, &lLower);
   SafeArrayGetUBound(pSafeArrProp , 1, &lUpper);
   
   for (long i = lLower; i <= lUpper; ++i) 
   {
      CComBSTR   bstrPropName;

      if (S_OK !=  (hres = SafeArrayGetElement(pSafeArrProp, &i, &bstrPropName)) )
      {
         if (NULL != pSafeArrProp)
            SafeArrayDestroy(pSafeArrProp);
         return hres;
      }

      USES_CONVERSION;
      psarPropRef.SetAtGrow(psarPropRef.GetSize(), OLE2T(bstrPropName));
   }
   
   if (NULL != pSafeArrProp)
      SafeArrayDestroy(pSafeArrProp);

   return hres;
}


///////////////////////////////////////////////////////////////////////
//6)   Executing instance method I do through ExecMethodWMI.
// The user has to take care to the property name array,
// in - argument VARIANT array and size of in -  arguments he 
// want to receive into object method. 
// See the void CWMI_TestDlg::ExecMethod (UINT nID) implementation; 
// there I fill these arguments for Win32_Process and 
// Win32_OperatingSystem classes.
///////////////////////////////////////////////////////////////////////

HRESULT  ExecMethodWMI ( IN IWbemServices* piWmiServ,
                   const CString& csMethodName,
                   const CString& csClassName,
                   const CString& csClassPath,
                   const CString& csObjectPath,
                   const CStringArray* csarrPropNames /*=NULL*/,
                   VARIANT *arrVarInArg/*=NULL*/, const int size_t/*=0*/)
{
   // sanity checks
   if (NULL == piWmiServ)
      return E_INVALIDARG;

   if (( NULL != csarrPropNames  && NULL == arrVarInArg) ||
      ( NULL == csarrPropNames  && NULL != arrVarInArg)   )
         return E_INVALIDARG;

   if (NULL != csarrPropNames)
   {
      if(size_t != csarrPropNames->GetSize())
         return E_INVALIDARG;
   }

   IWbemClassObject*   pClassObj   = NULL;
   IWbemClassObject*   pOutParam   = NULL;
   IWbemClassObject*   pInParam    = NULL;
    
   IWbemClassObject*   pInClass    = NULL;
   IWbemClassObject*   pOutClass   = NULL;

   CComBSTR   bstrMethodName   ( csMethodName);
   CComBSTR   bstrClassName    ( csClassName );
   CComBSTR   bstrClassPath    ( csClassPath );
   CComBSTR   bstrObjectPath   ( csObjectPath);
 
   HRESULT   hres;
   hres = piWmiServ->GetObject(bstrClassName, 0, NULL, &pClassObj, NULL);

    if (WBEM_S_NO_ERROR == hres)
   {
      // get the input-argument class object and create an instance.
      // pInClass == NULL indicates that no input parameters needed.
      hres = pClassObj->GetMethod(bstrMethodName, 0, &pInClass, NULL);

      if (WBEM_S_NO_ERROR == hres)
      {
         if( NULL != pInClass)
         {
            // create instance copy
            if(WBEM_S_NO_ERROR == (hres=pInClass->SpawnInstance(0, &pInParam)) )
            {
               // set each property
               for (long i = 0; i < size_t; ++i)
               {   
                  CComBSTR bstrPropName(csarrPropNames->GetAt(i));
                  hres = pInParam->Put(bstrPropName, 0, &arrVarInArg[i], 0);

                  // DUF!!! Put failed, check the properties and their types
                  if (WBEM_S_NO_ERROR != hres)
                     break;
               }
            }
         }         
         // finally call the method
         if (WBEM_S_NO_ERROR == hres)
            hres = piWmiServ->ExecMethod(bstrObjectPath, bstrMethodName, 0, NULL, pInParam, &pOutParam, NULL);
      }
   }

   // free all resources 
   if (NULL != pOutParam)
   {
      // but first we get the output parameters here
      CComBSTR   bstrClassObj;
      hres = pOutParam->GetObjectText(0, &(bstrClassObj.m_str));

      USES_CONVERSION;
      
      CWnd* pWndMain = AfxGetMainWnd();
      MessageBox( pWndMain ? pWndMain->m_hWnd : NULL, OLE2T(bstrClassObj), "Result parameters", MB_OK);

      pOutParam->Release();
   }

   if (NULL != pClassObj)      pClassObj->Release();
   if (NULL != pInParam)       pInParam->Release();
   if (NULL != pInClass)       pInClass->Release();
   if (NULL != pOutClass)      pOutClass->Release();

    return hres;
}


///////////////////////////////////////////////////////////////////////
//7)   And finally the GetClassMethodsWMI returns through CStringArray 
// argument the array of all class object methods.
///////////////////////////////////////////////////////////////////////

HRESULT  GetClassMethodsWMI ( IN IWbemClassObject* piappObj, 
                             OUT CStringArray&   csarrMethods)
{

   if (NULL == piappObj)
      return E_INVALIDARG;

   csarrMethods.RemoveAll();
      
   USES_CONVERSION;

   HRESULT   hres;
   hres = piappObj->BeginMethodEnumeration(0);

   while(WBEM_S_NO_ERROR == hres)
   {
      CComBSTR   bstrMethodName;   
      hres = piappObj->NextMethod(0, &bstrMethodName, NULL, NULL);

      if (WBEM_S_NO_ERROR == hres)
         csarrMethods.SetAtGrow(csarrMethods.GetSize(), OLE2T(bstrMethodName));
   }
   
   return piappObj->EndMethodEnumeration();
}

Thats all (meantime).

Good luck!!!

Downloads

Download demo project - 64.0 Kb
Download source - 4 Kb


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