#ifndef _NTRTL_H
NTSYSAPI
NTSTATUS
NTAPI
RtlGetOwnerSecurityDescriptor(
    _In_ PSECURITY_DESCRIPTOR SecurityDescriptor,
    _Outptr_result_maybenull_ PSID *Owner,
    _Out_ PBOOLEAN OwnerDefaulted
    );
View code on GitHubThis function is documented in Windows Driver Kit.