Effective file permissions tool's api in windows

Question

Starting from Windows Server 2003, Windows included a new tool which calculates the effective permissions for a user (basically it resolves all groups access and takes care

Answer 1

I found a function called GetEffectiveRightsFromAcl in advapi32.dll. This seems to be exactly what I was looking for. Actually, the effective permissions tool uses the AuthzAccessCheck function. I used it, and did not find performance degradation by as much as I thought. (However, I am told that Authz does not include the "integrity" concept available in windows 7 and above, and may report wrong results.)

Answer 2

Some quick code:

using System;
using System.IO;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.AccessControl;


namespace ConsoleApplication1
{
    class Program
    {
        [DllImport("advapi32.dll", SetLastError = true)]
        static extern uint GetEffectiveRightsFromAcl(IntPtr pDacl, ref TRUSTEE pTrustee, ref ACCESS_MASK pAccessRights);

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto, Pack = 4)]
        struct TRUSTEE
        {
            IntPtr pMultipleTrustee; // must be null
            public int MultipleTrusteeOperation;
            public TRUSTEE_FORM TrusteeForm;
            public TRUSTEE_TYPE TrusteeType;
            [MarshalAs(UnmanagedType.LPStr)]
            public string ptstrName;
        }

        enum TRUSTEE_FORM
        {
            TRUSTEE_IS_SID,
            TRUSTEE_IS_NAME,
            TRUSTEE_BAD_FORM,
            TRUSTEE_IS_OBJECTS_AND_SID,
            TRUSTEE_IS_OBJECTS_AND_NAME
        }

        enum TRUSTEE_TYPE {
          TRUSTEE_IS_UNKNOWN,
          TRUSTEE_IS_USER,
          TRUSTEE_IS_GROUP,
          TRUSTEE_IS_DOMAIN,
          TRUSTEE_IS_ALIAS,
          TRUSTEE_IS_WELL_KNOWN_GROUP,
          TRUSTEE_IS_DELETED,
          TRUSTEE_IS_INVALID,
          TRUSTEE_IS_COMPUTER 
        } 

        [DllImport("advapi32.dll", CharSet = CharSet.Auto)]
        static extern uint GetNamedSecurityInfo(
            string pObjectName,
            SE_OBJECT_TYPE ObjectType,
            SECURITY_INFORMATION SecurityInfo,
            out IntPtr pSidOwner,
            out IntPtr pSidGroup,
            out IntPtr pDacl,
            out IntPtr pSacl,
            out IntPtr pSecurityDescriptor);

        enum ACCESS_MASK : uint
        {
            DELETE = 0x00010000,
            READ_CONTROL = 0x00020000,
            WRITE_DAC = 0x00040000,
            WRITE_OWNER = 0x00080000,
            SYNCHRONIZE = 0x00100000,

            STANDARD_RIGHTS_REQUIRED = 0x000f0000,

            STANDARD_RIGHTS_READ = 0x00020000,
            STANDARD_RIGHTS_WRITE = 0x00020000,
            STANDARD_RIGHTS_EXECUTE = 0x00020000,

            STANDARD_RIGHTS_ALL = 0x001f0000,

            SPECIFIC_RIGHTS_ALL = 0x0000ffff,

            ACCESS_SYSTEM_SECURITY = 0x01000000,

            MAXIMUM_ALLOWED = 0x02000000,

            GENERIC_READ = 0x80000000,
            GENERIC_WRITE = 0x40000000,
            GENERIC_EXECUTE = 0x20000000,
            GENERIC_ALL = 0x10000000,

            DESKTOP_READOBJECTS = 0x00000001,
            DESKTOP_CREATEWINDOW = 0x00000002,
            DESKTOP_CREATEMENU = 0x00000004,
            DESKTOP_HOOKCONTROL = 0x00000008,
            DESKTOP_JOURNALRECORD = 0x00000010,
            DESKTOP_JOURNALPLAYBACK = 0x00000020,
            DESKTOP_ENUMERATE = 0x00000040,
            DESKTOP_WRITEOBJECTS = 0x00000080,
            DESKTOP_SWITCHDESKTOP = 0x00000100,

            WINSTA_ENUMDESKTOPS = 0x00000001,
            WINSTA_READATTRIBUTES = 0x00000002,
            WINSTA_ACCESSCLIPBOARD = 0x00000004,
            WINSTA_CREATEDESKTOP = 0x00000008,
            WINSTA_WRITEATTRIBUTES = 0x00000010,
            WINSTA_ACCESSGLOBALATOMS = 0x00000020,
            WINSTA_EXITWINDOWS = 0x00000040,
            WINSTA_ENUMERATE = 0x00000100,
            WINSTA_READSCREEN = 0x00000200,

            WINSTA_ALL_ACCESS = 0x0000037f
        }

        [Flags]
        enum SECURITY_INFORMATION : uint
        {
            OWNER_SECURITY_INFORMATION = 0x00000001,
            GROUP_SECURITY_INFORMATION = 0x00000002,
            DACL_SECURITY_INFORMATION = 0x00000004,
            SACL_SECURITY_INFORMATION = 0x00000008,
            UNPROTECTED_SACL_SECURITY_INFORMATION = 0x10000000,
            UNPROTECTED_DACL_SECURITY_INFORMATION = 0x20000000,
            PROTECTED_SACL_SECURITY_INFORMATION = 0x40000000,
            PROTECTED_DACL_SECURITY_INFORMATION = 0x80000000
        }

        enum SE_OBJECT_TYPE
        {
            SE_UNKNOWN_OBJECT_TYPE = 0,
            SE_FILE_OBJECT,
            SE_SERVICE,
            SE_PRINTER,
            SE_REGISTRY_KEY,
            SE_LMSHARE,
            SE_KERNEL_OBJECT,
            SE_WINDOW_OBJECT,
            SE_DS_OBJECT,
            SE_DS_OBJECT_ALL,
            SE_PROVIDER_DEFINED_OBJECT,
            SE_WMIGUID_OBJECT,
            SE_REGISTRY_WOW64_32KEY
        }


        static void Main(string[] args)
        {            

        String user = "DOMAIN\\USER";
        String Path = "C:\\";

            IntPtr pSidOwner, pSidGroup, pDacl, pSacl, pSecurityDescriptor;
            ACCESS_MASK mask = new ACCESS_MASK();
            uint ret = GetNamedSecurityInfo(Path, 
                SE_OBJECT_TYPE.SE_FILE_OBJECT, 
                SECURITY_INFORMATION.DACL_SECURITY_INFORMATION,
                out pSidOwner, out pSidGroup, out pDacl, out pSacl, out pSecurityDescriptor);

            TRUSTEE t = new TRUSTEE();
            t.TrusteeForm = TRUSTEE_FORM.TRUSTEE_IS_NAME;
            t.TrusteeType= TRUSTEE_TYPE.TRUSTEE_IS_USER;
            t.ptstrName = user;
            ret = GetEffectiveRightsFromAcl(pDacl, ref t , ref mask);

            if ((mask & ACCESS_MASK.READ_CONTROL) == ACCESS_MASK.READ_CONTROL)
            {
                System.Diagnostics.Debug.WriteLine("Read");
            }
            else
            {
                System.Diagnostics.Debug.WriteLine("No Read");
            }

        }
    }
}

Answer 3

You can determine the effective permission of an user over a file/folder by using the Authz API provided by Windows. Follow the below link. https://msdn.microsoft.com/en-us/library/windows/desktop/ff394768(v=vs.85).aspx and also this. https://msdn.microsoft.com/en-us/library/windows/desktop/aa446637(v=vs.85).aspx. I have tried this out in all versions of Windows starting from Windows server 2003 and got fairly good performance.