windows user account control (uac) security technologies · •uac is an new user account control...

Windows User Account Control (UAC)

www.winitor.com – Nov.2009

Security Technologies

• Many more or less visible security related features

• Encrypting File System (EFS)

• BitLocker

• Services Hardening

• Address Space Layout Randomization (ASLR)

• Integrity Level

• File System Virtualization

• Registry Virtualization

• User Interface Privilege Isolation (UIPI)

• IE Protected Mode

• Protected Processes

• User Account Control

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Introduction

• UAC remains a misunderstood feature

• UAC is not an user access control system

• UAC is an new user account control framework

• UAC has several goals

• force (administrators) users to work with less rights

• control legacy applications

• enable actions without administrative credentials

• protect the system from malware and from administrators




Motivation

• Reduce the exposure surface of the operating system

• Mitigate the impact of malware

• Make computers (and networks) less vulnerable




Token Types

• Applications run in one of the following security contexts• Standard user

• Administrator user




Visible Identification

• In the past users could not easily tell what actions required administrative credentials

• Vista removes this uncertainty by showing a shield to identify actions that require administrative privileges




User Interaction

• When working using an administrative account, a user must (by default) conscent an action requesting elevated rights.




User Interaction

• When working using a standard account, a user must provide adequate credentials in oder to perform an action requesting administrative privileges.




Consent Prompt Types

• Built-in Windows program




• Digital signed third-party applications






• Unsigned third-party applications




Configuration

• Switching User Account Control on or off




Configuration

• Disabling User Account Control is tagged as unsecured




Configuration

• Security Policy enables a very granular and flexible configuration of the UAC behaviors

• Localy/Globaly




Configuration

• The built-in Administrator account can be configured to run in one of the following modes:

• Admin Approval Mode

• XP Compatible Mode (default)




Framework

• UAC is built on different new technologies

• Windows file system virtualization

• Windows Registry virtualization

• Windows Integrity level

• …




Framework - Service

• User Account Control mechanism is built on the Application Information service




• The process name consent.exe is responsible to show the UAC dialogs

Framework - Consent




Framework - Desktop

• Elevation prompts are displayed on a secure desktop by default.




Framework – Application Marking

• UAC ready applications contain an XML manifest which documents the desired security Run Level credential




Framework – Resources Virtualization

• UAC Virtualization redirects the following locations

• \Program Files

• \Windows

• \Windows\System32

• \HKLM\Software

• Applications accesses are virtualized when accessing secure locations. These locations are then serialized in the corresponding user profile.

• \Users\AppData\Local\Virtual Store

• \HKCU\Software\Classes\VirtualStore

• Virtualization is intended as a bride technology to enable applications that are not UAC compatible to work properly

• Virtualization is not supported on 64bit systems




Workflow

• The workfow of UAC depends several factors

• The account a user is logged as

• The Security Policy




Running Programs Elevated

• One-time basis

• Always





• Application running in elevated mode





• Application running in normal mode




History

• Some components have kept their names

LUA UAP UAC




Links

• Windows Vista TechNet, www.microsoft.com/technet/windowsvista

• User Account Control Overview, www.microsoft.com/technet/windowsvista/security/uacppr.mspx

• User Account Control, www.microsoft.com/technet/windowsvista/security/uac.mspx


http://www.microsoft.com/technet/windowsvista

http://www.microsoft.com/technet/windowsvista/security/uacppr.mspx

http://www.microsoft.com/technet/windowsvista/security/uac.mspx

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