Problem - Kevin Tafuro

See Also
Recipes 1.3, 1.4, 2.8
2.2 Understanding the Windows Access Control
Model
Problem
You want to understand how access control works on Windows systems.
Solution
Versions of Windows before Windows NT have no access control whatsoever. Windows
95, Windows 98, and Windows ME are all intended to be single-user desktop
operating systems and thus have no need for access control. Windows NT, Windows
2000, Windows XP, and Windows Server 2003 all use a system of access control
lists (ACLs).
Most users do not understand the Windows access control model and generally
regard it as being overly complex. However, it is actually rather straightforward and
easy to understand. Unfortunately, from a programmer’s perspective, the API for
dealing with ACLs is not so easy to deal with.
In the “Discussion” section, we describe the Windows access control model from a
high level. We do not provide examples of using the API here, but other recipes
throughout the book do provide such examples.
Discussion
All Windows resources, including files, the registry, synchronization primitives (e.g.,
mutexes and events), and IPC mechanisms (e.g., pipes and mailslots), are accessed
through objects, which may be secured using ACLs. Every ACL contains a discretionary
access control list (DACL) and a system access control list (SACL). DACLs determine
access rights to an object, and SACLs determine auditing (e.g., logging) policy.
In this recipe, we are concerned only with access rights, so we will discuss only
DACLs.
A DACLcontains zero or more access control entries (ACEs). A DACLwith no ACEs,
said to be a NULL DACL, is essentially the equivalent of granting full access to
everyone, which is never a good idea. A NULL DACL means anyone can do anything
to the object. Not only does full access imply the ability to read from or write
to the object, it also implies the ability to take ownership of the object or modify its
DACL. In the hands of an attacker, the ability to take ownership of the object and
Understanding the Windows Access Control Model | 41
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.