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1 Event slides will be posted at:

2 User Account Control in Windows Vista Daniel Moth Developer & Platform Group Microsoft Ltd

3 AGENDA Why, What, How Manifests Process Elevation Virtualisation Compatibility Issues

4 UAC Goals The Vista goal: enable users to run with standard user rights Prevents deliberate (and accidental) modification of system settings Reduces malware impact by preventing modification of security settings and hardware Prevents compromise of sensitive information on shared computers

5 UAC Challenges The Windows usage model has been one of administrative rights Applications use them without knowing it Those that need it don’t distinguish administrative from standard user actions Users want administrative rights to easily perform operations that require them Software installations Changing the time zone Changing firewall settings Etc.

6 Administrative Rights Problem: there are still operations that require administrative rights: Installing applications Modifying system-global settings Parental controls Solution: make it convenient to access administrative rights from standard user accounts Identify operations that require administrative rights Allow for “run as” functionality Called Over The Shoulder (OTS) elevation

7 DEMO What UAC looks like to the end user

8 OTS Dialogs

9 User Account Control Internals Windows Vista Logon with UAC Enabled Administrator Token “Filtered” token 1.Token inspected for “elevated” privileges Explorer.exe created. 2. Elevated privileges removed. An administrator enters credentials in WinLogon UI Local Security Authority (LSA) verifies credentials Windows XP

10 UAC Internals² Defining Elevated Privileges User will have a filtered token if they belong to any admin-type group e.g.: Administrators Controllers Backup Operators User will have a filtered token if they have any of these privileges: Create Token, Debug, TCB, Take Ownership, Backup, Restore, Impersonate, Load Driver, Relabel

11 UAC Internals³ Administrator’s Standard User Identity Administrator’s standard user token is subset of their full administrator token Administrator groups are marked as “deny only” groups Applies to Domain Administrators, Builtin\Administrators and others Can only be used to deny access, never to grant E.g. if file only allows administrator access, user is denied access E.g. if allows a user’s group access, but denies administrators, user is denied access All privileges except the following are stripped: Change Notify, Shutdown, Undock, Reserve Processor, Time Zone When authenticating to remote resources: If system is non-domain joined, user authenticates as standard user If domain-joined and an administrator of the remote resource, user authenticates as administrator

12 StandardUser-Friendly Windows In Vista, many previously-admin operations are accessible by standard users: View system clock and calendar Change time zone Configure Wired Equivalent Privacy (WEP) to connect to secure wireless networks Change power management settings Add printers and other devices that have the required drivers installed on computer or have been allowed by an IT administrator in Group Policy Install ActiveX Controls from sites approved by an administrator Create and configure a Virtual Private Network connection Install critical Windows Updates

13 StandardUser-Friendly Your Application Test your application when running as Standard User!! Saving Per-User State as Standard User %userprofile% HKCU Saving Per-Machine State as Standard User %allusersprofile% Embed Manifest with run level = “asInvoker”

14 Privileges in Manifests Manifest files were introduced in Windows XP to support side-by-side DLLs Used for XP’s Common Control v6 dialog.NET uses it for managed code “assemblies” Embedded in resources of binary file New key in Vista, requestedElevationLevel asInvoker: Run with the user’s rights highestAvailable: if standard user then don’t ask, but if user is an administrator, then ask requireAdministrator: always ask

15 Embedding Manifest in VS Create Manifest in source directory Add following lines to.rc file for project #define MANIFEST_RESOURCE_ID 1 MANIFEST_RESOURCE_ID RT_MANIFEST "AdminApp.exe.manifest" Add additional manifest in project properties

16 DEMO Manifests

17 Process Creation in Vista with UAC Enabled CreateProcess* checks the following sources for privilege information about the process 1. Embedded Application Manifest 2. Side-by-Side External Manifest 3. App Compatibility Database 4. Installer Detection If process requires elevated privileges and parent process token does not possess these privileges ERROR_REQUIRES_ELEVATION is returned.

18 Explorer.exe UAC Prompt Internals ShellExecute AppInfo Service 2. RPC Consent.exe Admin.exe CreateProcess( Admin.exe) Standard User Local SystemAdministrator 3. Re-parented CreateProcessAsUser ( Admin.exe) CreateProcess 1. ERROR_ELEVATION_REQUIRED

19 DEMO Launching Elevated -Shield -Extract admin pieces as other manifested processes -Re-launch ourselves elevated

20 COM Elevation Accomplished using elevation moniker Object class must contain elevation attributes Example: File Operation elevation HKCR\CLSID\{3ad b85bdb8e09} \Elevation REG_DWORD Enabled=1 HKCR\CLSID\{3ad b85bdb8e09} REG_EXPAND_SZ LocalizedString=

21 DEMO Shell “access denied” to file

22 MSI Elevation Administrator only installation into the Public profile ALLUSERS=”1” or ALLUSERS=”2” Word Count Summary property Bit 3 = 0 Per-user installation that can be installed by a Standard User ALLUSERS=”” or don’t define the property Word Count Summary property Bit 3 = 1

23 Common AppCompat Issue File and Registry Permissions Many applications would run fine as standard user …but they needlessly store data in HKLM\Software or %ProgramFiles% They use these locations for per-user data, not global data These locations are system-global and so only writeable by administrators It’s always worked because Windows users have always been administrators

24 DEMO Virtualisation Modifications of most system-global locations go to per-user areas Reads generally go to the per-user location and fall back to the global location

25 File Virtualisation Redirected file system locations: %ProgramFiles% (\Program Files) %SystemRoot% (\Windows) %SystemRoot%\System32 (\Windows\System32) %AllUsersProfile% (\ProgramData – what was \Documents and Settings\All Users) Exceptions: Files that have executable extensions (.exe,.bat,.vbs,.scr, etc) Exceptions can be added in HKLM\System\CurrentControlSet\Services\Luafv\Parameters \ExcludedExtensionsAdd Per-user virtual root: %UserProfile%\AppData\Local\VirtualStore

26 Registry Virtualization Redirected locations: HKLM\Software Exceptions: HKLM\Software\Microsoft\Windows HMLM\Software\Microsoft\Windows NT Other subkeys under Microsoft Per-user virtual root: HKEY_CURRENT_USER\Software\Classes\VirtualStore

27 Virtualized Processes Processes are virtualized unless They are running with administrative rights They are 64-bit They have a requestedExecutionLevel in their executable manifest Most Windows Vista executables Can be turned off globally via local security policy setting (secpol.msc)

28 DEMO UAC: Local Security Policies

29 Installation AppCompat Issues Don’t Perform Administrator Operations on First Run Configure all machine-wide state during install Updating Application Binaries Usually Requires Administrator Privileges Application binaries in %ProgramFile% cannot be overwritten by a Standard User. MSI updating technology (MSPs) does elevated update based on the signature of the patch Use Bootstrapper to Launch Application As Part of Install

30 Summary Understand UAC Filtered Token, Elevation, Process creation, Prompts, Shields, Manifests, Virtualisation Act Now Test your applications as a Standard User Use the Standard User Analyzer to help Embed a manifest in your EXEs Fix your installation programs (use MSI)

31 UAC Resources User Account Control Resources for IT Professionals (TechNet Landing Page) Windows Vista Application Development Requirements for UAC Compatibility 38acd478f46d/WindowsVistaUACDevReqs.dochttp://download.microsoft.com/download/5/6/a/56a0ed11-e073-42f9-932b- 38acd478f46d/WindowsVistaUACDevReqs.doc UAC Team blog COM Elevation Moniker us/com/html/1595ebb8-65af-4609-b3e7-a21209e64391.asphttp://msdn.microsoft.com/library/default.asp?url=/library/en- us/com/html/1595ebb8-65af-4609-b3e7-a21209e64391.asp Windows Vista UX Guidelines for UAC us/UxGuide/UXGuide/Environment/UAC/UAC.asp MSI Patching Technology Service Security

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35 ©2006 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS SUMMARY.


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