Using WMI to enumerate local user accounts

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Introduction

Sometimes, you want to get information about user accounts in your computer. This article will help you get that information using WMI.

Supported Platforms

How to use it?

Step 1: Initialize COM:

 CoInitialize(NULL);

Step 2: Set COM security levels:

 //Security needs to be initialized in XP first

 // and this was the major problem

 //why it was not working in XP.

 if(CoInitializeSecurity( NULL,
   -1,
   NULL,
   NULL,
   RPC_C_AUTHN_LEVEL_PKT,
   RPC_C_IMP_LEVEL_IMPERSONATE,
   NULL,
   EOAC_NONE,
   0
  ) != S_OK)
  return;

Step 3: Obtain the initial locator to WMI:

 IWbemLocator * pIWbemLocator = NULL;
 IWbemServices * pWbemServices = NULL;
 IEnumWbemClassObject * pEnumObject  = NULL;

 BSTR bstrNamespace = (L"root\\cimv2");


 if(CoCreateInstance (
    CLSID_WbemAdministrativeLocator,
    NULL ,
    CLSCTX_INPROC_SERVER | CLSCTX_LOCAL_SERVER , 
    IID_IUnknown ,
    ( void ** ) & pIWbemLocator
            ) != S_OK)
    return;

Step 4: Connect to WMI through the IWbemLocator::ConnectServer method:

 if(pIWbemLocator->ConnectServer(
     bstrNamespace,  // Namespace

     NULL,          // Userid

     NULL,           // PW

     NULL,           // Locale

     0,              // flags

     NULL,           // Authority

     NULL,           // Context

     &pWbemServices
                ) != S_OK)
    return;

Step 5: Use the IWbemServices pointer to make requests of WMI:

 HRESULT hRes;
 BSTR strQuery = (L"Select * from Win32_UserAccount") + 
                 (L" Where LocalAccount = True");
 BSTR strQL = (L"WQL");
 hRes = pWbemServices->ExecQuery(strQL, strQuery, 
        WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &pEnumObject);
 
 if(hRes != S_OK)
 {
  MessageBox("Could not execute Query");
  return;
 }

Step 6: Get data from the query in step 5.

 ULONG uCount = 1, uReturned;
 IWbemClassObject * pClassObject = NULL;


 hRes = pEnumObject->Reset();

 if(hRes != S_OK)
 {
  MessageBox("Could not Enumerate");
  return;
 }

 int nItemIndex = 0;
 while (1)
 {
  hRes = pEnumObject->Next(WBEM_INFINITE, uCount, 
         &pClassObject, &uReturned);
  if(hRes != S_OK)
  {
   break;
  }

  for (int i = enmAccountType; i < enmTotal; i ++)
  {
   VARIANT v;
   BSTR strClassProp = SysAllocString(arrStrFields[i]);
   hRes = pClassObject->Get(strClassProp, 0, &v, 0, 0);

   SysFreeString(strClassProp);
   _bstr_t bstrPath = &v;  //Just to convert BSTR to ANSI

   char* strPath=(char*)bstrPath;

   if (SUCCEEDED(hRes))
   {
    if (i == enmAccountType)
    {
     m_lstUsers.InsertItem(nItemIndex, strPath);
    }
    else
    {
     m_lstUsers.SetItemText(nItemIndex, i, strPath);
    }
   }

   VariantClear( &v );
  }
  nItemIndex ++;
 }

Step 7: Free memory.

 pIWbemLocator->Release();
 pWbemServices->Release();
 pEnumObject->Release();
 pClassObject->Release();
 CoUninitialize();

Note

For more information about the Win32_UserAccount class used in this script, click here.