Modifying the defaultSecurityDescriptor for an Object Class

The following code example retrieves the default security descriptor for an object class, adds an ACE to the DACL, and then sets the modified security descriptor on the object class.

Be aware that schema modification is disabled, by default, on all Windows 2000 domain controllers. To enable schema modification at a particular DC, set a REG_DWORD value named "Schema Update Allowed" under the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NTDS\Parameters

Add this value if it does not already exist. Set this value to 1 to enable schema modification. If this value is zero, schema modification is disabled. The Schema Manager MMC snap-in provides a check box that selects or clears this registry key.


//  Add msvcrt.dll to your project
//  Add activeds.lib to your project
//  Add adsiid.lib to your project

#include "stdafx.h"
#include <wchar.h>
#include <objbase.h>
#include <activeds.h>
#include <ACLAPI.h>
#include <winnt.h>
#include <Sddl.h>
#include "atlbase.h"
#include "stdio.h"
#include "iads.h"
 
#define _WIN32_WINNT 0x0500
 
HRESULT ModifyDefaultSecurityDescriptor( IADs *pObject );

//  Entry point for the application.
int main(int argc, char *argv[])
{
LPOLESTR szPath = new OLECHAR[MAX_PATH];
LPOLESTR pszBuffer  = new WCHAR[MAX_PATH];
HRESULT hr = S_OK;
IADs *pObject = NULL;
VARIANT var;
 
wprintf(L"This program modifies the default security descriptor of an object class\n");
wprintf(L"Specify the object class:");
#ifdef _MBCS
_getws_s(pszBuffer);
if (!pszBuffer)
    return TRUE;
wcscpy_s(szPath,L"LDAP://cn=");
wcscat_s(szPath,pszBuffer);
wcscat_s(szPath,L",");
#endif _MBCS
 
//  Initialize COM.
CoInitialize(NULL);
 
//  Get rootDSE and the schema container DN. Bind to the
//  current user's domain using current user's security context.
 
hr = ADsOpenObject(L"LDAP://rootDSE",
            NULL,
            NULL,
            ADS_SECURE_AUTHENTICATION, // Use Secure Authentication.
            IID_IADs,
            (void**)&pObject);
 
if (SUCCEEDED(hr)) {
    hr = pObject->Get(CComBSTR("schemaNamingContext"), &var);
    if (SUCCEEDED(hr)) {
        #ifdef _MBCS
        wcscat_s(szPath,var.bstrVal);
        #endif _MBCS
        VariantClear(&var);
        if (pObject) {
            pObject->Release();
            pObject = NULL;
    }
    hr = ADsOpenObject(szPath,
               NULL,
               NULL,
               ADS_SECURE_AUTHENTICATION, //  Use Secure Authentication.
               IID_IADs,
               (void**)&pObject);
    if (SUCCEEDED(hr)) {
        wprintf(L"Modify the default SD for the %s class\n", pszBuffer);
        hr = ModifyDefaultSecurityDescriptor( pObject );
    }
  }
}
 
if (FAILED(hr))
    wprintf(L"Failed with the following HRESULT: 0x%x\n", hr);
 
if (pObject)
    pObject->Release();
 
//  Uninitialize COM.
 
CoUninitialize();
return TRUE;
}    
 
 
HRESULT ModifyDefaultSecurityDescriptor(
                          IADs *pObject
                          )
{
HRESULT hr = E_FAIL;
VARIANT var;
PSECURITY_DESCRIPTOR pSDCNV = NULL;
SECURITY_DESCRIPTOR SD = {0};
DWORD dwSDSize = sizeof(SECURITY_DESCRIPTOR);
PSID pOwnerSID = NULL;
DWORD dwOwnerSIDSize = 0;
PSID pGroupSID = NULL;
DWORD dwGroupSIDSize = 0;
PACL pDACL = NULL;
DWORD dwDACLSize = 0;
PACL pSACL = NULL;
DWORD dwSACLSize = 0;
BOOL bDaclPresent = FALSE;
BOOL bDaclDefaulted = FALSE;
PACL pOldDACL, pNewDACL;
ULONG ulLen;
EXPLICIT_ACCESS ea;
DWORD dwRes;
 
//  Get the default security descriptor. Type should be VT_BSTR.
 
hr = pObject->Get(CComBSTR("defaultSecurityDescriptor"), &var);
if (FAILED(hr) || var.vt!=VT_BSTR ) {
    wprintf(L"Error getting default SD: 0x%x\n", hr );
    goto Cleanup;
}
 
wprintf(L"Old Default SD: %s\n", var.bstrVal);
 
//  Convert the security descriptor string to a security descriptor.
 
if ( ! ConvertStringSecurityDescriptorToSecurityDescriptor (
           var.bstrVal, SDDL_REVISION_1, &pSDCNV, NULL )) {
    wprintf(L"Error converting string security descriptor: %d\n", 
           GetLastError() );
    goto Cleanup;
}
 
//  Convert self-relative security descriptor to absolute.
//  First, get the required buffer sizes.
 
if (! MakeAbsoluteSD(pSDCNV, &SD, &dwSDSize, 
           pDACL, &dwDACLSize, 
           pSACL, &dwSACLSize, 
           pOwnerSID, &dwOwnerSIDSize, 
           pGroupSID, &dwGroupSIDSize) ) {
 
  //  Allocate the buffers.
 
  pDACL = (PACL) GlobalAlloc(GPTR, dwDACLSize);
  pSACL = (PACL) GlobalAlloc(GPTR, dwSACLSize);
  pOwnerSID = (PACL) GlobalAlloc(GPTR, dwOwnerSIDSize);
  pGroupSID = (PACL) GlobalAlloc(GPTR, dwGroupSIDSize);
  if (! (pDACL && pSACL && pOwnerSID && pGroupSID) ) {
    wprintf(L"GlobalAlloc failed: %d\n", GetLastError() );
    goto Cleanup;
  }
 
  //  Perform the conversion.
 
  if (! MakeAbsoluteSD(pSDCNV, &SD, &dwSDSize, pDACL, &dwDACLSize, 
           pSACL, &dwSACLSize, pOwnerSID, &dwOwnerSIDSize, 
           pGroupSID, &dwGroupSIDSize) ) {
    wprintf(L"MakeAbsoluteSD: %d\n", GetLastError() );
    goto Cleanup;
  }
}
 
//  Get the DACL from the security descriptor.
 
if (! GetSecurityDescriptorDacl(&SD, &bDaclPresent, 
                  &pOldDACL, &bDaclDefaulted) ) {
    wprintf(L"GetSecurityDescriptorDacl failed: %d\n", GetLastError() );
    goto Cleanup;
} 
 
//  Initialize an EXPLICIT_ACCESS structure for the new ACE.
//  The ACE grants Everyone the right to read properties.
 
ZeroMemory(&ea, sizeof(EXPLICIT_ACCESS));
ea.grfAccessPermissions = ADS_RIGHT_DS_READ_PROP;
ea.grfAccessMode = GRANT_ACCESS;
ea.grfInheritance= 0;
ea.Trustee.TrusteeForm = TRUSTEE_IS_NAME;
ea.Trustee.ptstrName = TEXT("Everyone");
 
//  Create a new ACL that merges the new ACE into the existing DACL.
 
dwRes = SetEntriesInAcl(1, &ea, pOldDACL, &pNewDACL);
if (ERROR_SUCCESS != dwRes)  {
    wprintf(L"SetEntriesInAcl Error %u\n", dwRes );
    goto Cleanup;
}
 
//  Put the modified DACL into the security descriptor.
 
if (! SetSecurityDescriptorDacl(&SD, TRUE, pNewDACL, FALSE) ) {
    wprintf(L"SetSecurityDescriptorOwner failed: %d\n", 
            GetLastError() );
    goto Cleanup;
} 
 
//  Convert the security descriptor back to string format.
 
VariantClear(&var);
if ( ! ConvertSecurityDescriptorToStringSecurityDescriptor (
        &SD, SDDL_REVISION_1, 
        GROUP_SECURITY_INFORMATION | OWNER_SECURITY_INFORMATION |
        DACL_SECURITY_INFORMATION | SACL_SECURITY_INFORMATION, 
        &var.bstrVal, &ulLen )) {
    wprintf(L"Error converting security descriptor to string: %d\n", 
        GetLastError() );
    goto Cleanup;
}
 
wprintf(L"New default SD: %s\n", var.bstrVal);
V_VT(&var) = VT_BSTR;
 
//  Use Put and SetInfo to set the modified security descriptor.
 
hr = pObject->Put(CComBSTR("defaultSecurityDescriptor"), var);
if (FAILED(hr)) {
    wprintf(L"Error putting default SD: 0x%x\n", hr );
    goto Cleanup;
}
 
hr = pObject->SetInfo();
if (FAILED(hr)) {
    wprintf(L"Error setting default SD: 0x%x\n", hr );
    goto Cleanup;
}
 
Cleanup:
 
VariantClear(&var);
if (pSDCNV) 
    LocalFree(pSDCNV);
if (pDACL) 
    GlobalFree(pDACL);
if (pSACL) 
    GlobalFree(pSACL);
if (pOwnerSID) 
    GlobalFree(pOwnerSID);
if (pGroupSID) 
    GlobalFree(pGroupSID);
if (pNewDACL) 
    LocalFree(pNewDACL);
 
return hr;
}


 

 

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