NT Security Classes for .NET

Introduction

This class library allows access to the Win32 security calls in a .NET friendly way. It encapsulates the concepts of a user, a securable object (like a file, named pipe, directory, etc.), and permissions. This library was written in Managed C++ to simplify the amount of work needed to link to existing Win32 libraries. However, since it exposes all of its functionality via .NET, it can be used from any .NET compliant language, including C# and Visual Basic. The project was written and compiled with Visual Studio 2002.

NOTE: There is a library written by some Microsoft guys on GotDotNet that does much of the same thing and more. It can be found at http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=e6098575-dda0-48b8-9abf-e0705af065d9.

This article outlines the primary objects in the library and their use in manipulating security objects.

Documentation

WindowsUser class

This class represents a single Windows identity (SID). It can be created by specifying either a username ("DOMAIN\user" format) or the string representation of a SID ("S-1-5-xxxx-xxx..."). You can also get the identity of the current user using the static property CurrentUser.

There are a number of predefined identities that exist as static members of a child class called WellKnownIdentities. Once you have an identity, you can get the following properties:

AccountName: string name of the account
Domain: string name of the account's domain
FullName: string in the form of "Domain\AccountName"
SidString: string representation of the SID

SecuredObject class

This class represents an object which can have a security descriptor. It can be created by specifying the name of the resource along with its type or by passing a handle (as an IntPtr) to the resource.

Once you have the object, you can update the permissions, audit information, owner and group.

PermissionsList

This class encapsulates actions on the ACL. It allows granting, revoking, changing, and denying access levels to different users. Derived from AccessList, which is a collection class for AccessEntry.

AuditingList

This class encapsulates actions on the auditing list of an object. It allows getting and setting audit success and failure rights. Derived from AccessList, which is a collection class for AccessEntry.

AccessEntry

This class encapsulates the Access Control Entry or ACE. You can set the user (trustee) and the associated rights and inheritance.

Example

This code shows the library in action. It assumes you have aliased the Microsoft.Win32.Security namespace (using in C#, Imports in VB).

// Get the current user and print their information
WindowsUser user = WindowsUser.CurrentUser;
Console.WriteLine("{0} ({1})", user.FullName, user.SidString);

// Get the current user from their token
WindowsUser duser = new WindowsUser(
  System.Security.Principal.WindowsIdentity.GetCurrent().Token);
Console.WriteLine(duser.FullName);

// Compare users
if (user == duser)
   Console.WriteLine("Same");
else
   Console.WriteLine("Different");

// Get a well-known user
user = WindowsUser.WellKnownIdentities.World;
Console.WriteLine(user.FullName);

// Get a user by name from a specific server (usually a domain controller)
WindowsUser kuser = new WindowsUser("user2", @"\\MYPDC");
Console.WriteLine(kuser.FullName);

// Get a user by name
user = new WindowsUser("DOMAIN\\user3");
Console.WriteLine(user.FullName);

// Get a user by SID
user = new WindowsUser("S-1-5-21-21782756-1035017279-1439700725-1111");
Console.WriteLine(user.FullName);

// Get security for C:\ directory
SecuredObject sec = new SecuredObject("C:\\", SecuredObjectType.FileObject);
DumpObject(sec);

// Set some various permissions on the directory
sec.Permissions.SetAccess(kuser, AccessRights.FileRead,
   AceInheritanceFlags.ContainerInherit|AceInheritanceFlags.ObjectInherit);
sec.Permissions.GrantAccess(kuser, AccessRights.FileExecute,
   AceInheritanceFlags.ContainerInherit|AceInheritanceFlags.ObjectInherit);
sec.Permissions.DenyAccess(kuser, AccessRights.FileWriteUnsync,
   AceInheritanceFlags.ContainerInherit|AceInheritanceFlags.ObjectInherit);
WindowsUser owner = sec.Owner;
sec.Owner = duser;
sec.Auditing.SetAuditFailure(duser, AccessRights.FileReadUnsync,
   AceInheritanceFlags.ContainerInherit|AceInheritanceFlags.ObjectInherit);
DumpObject(sec);

// Revoke some access
sec.Permissions.RevokeAccess(kuser);
sec.Owner = owner;
DumpObject(sec) ;

// Reset the security on the directory
sec.Permissions.Clear();
sec.Permissions.InheritFromParent = true;
DumpObject(sec);

// Write the DACL using the Microsoft style
Console.WriteLine(sec.ToString());

The following function shows how to enumerate the permissions on a security object.

static void DumpObject(SecuredObject sec)
{
   Console.WriteLine("Security description:");
   Console.WriteLine("=====================");
   Console.WriteLine("Owner: {0}\nGroup: {1}", 
     sec.Owner.FullName, sec.Group.FullName);
   Console.WriteLine("Permissions:");
   foreach (AccessEntry ace in sec.Permissions)
      Console.WriteLine(String.Format("  {0} : {1} : {2}", 
         ace.Trustee.FullName,
         ace.Inheritance, ace.Rights));
   Console.WriteLine("Auditing:");
   foreach (AccessEntry ace in sec.Auditing)
      Console.WriteLine(String.Format("  {0} : {1} : {2}", 
         ace.Trustee.FullName,
         ace.Inheritance, ace.Rights));
}