Secure Programming Cookbook for C and C++

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 Section 2.2.3, 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 DACL contains zero or more access ...