• Chapter 1. Installing and Configuring Windows Server 2003
  • software development Company Server 2003
  • Chapter 1. Installing and Configuring Windows Server 2003
  • New Features in Windows Server 2003
  • Best Practices
  • Moving Forward
  • Version Comparisons
  • Hardware Recommendations
  • Installation Checklist
  • Functional Overview of Windows Server 2003 Setup
  • Installing Windows Server 2003
  • Post Setup Configurations
  • Functional Description of the Windows Server 2003 Boot Process
  • Correcting Common Setup Problems
  • Chapter 2. Performing Upgrades and Automated Installations
  • New Features in Windows Server 2003
  • NT4 Upgrade Functional Overview
  • Upgrading an NT4 or Windows 2000 Server
  • Automating Windows Server 2003 Deployments
  • Moving Forward
  • Chapter 3. Adding Hardware
  • New Features in Windows Server 2003
  • Functional Description of Windows Server 2003 Architecture
  • Overview of Windows Server 2003 Plug and Play
  • Installing and Configuring Devices
  • Troubleshooting New Devices
  • Moving Forward
  • Chapter 4. Managing NetBIOS Name Resolution
  • New Features in Windows Server 2003
  • Moving Forward
  • Overview of Windows Server 2003 Networking
  • Name Resolution and Network Services
  • Network Diagnostic Utilities
  • Resolving NetBIOS Names Using Broadcasts
  • Resolving NetBIOS Names Using Lmhosts
  • Resolving NetBIOS Names Using WINS
  • Managing WINS
  • Disabling NetBIOS-over-TCP/IP Name Resolution
  • Chapter 5. Managing DNS
  • New Features in Windows Server 2003
  • Configuring a Caching-Only Server
  • Configuring a DNS Server to Use a Forwarder
  • Managing Dynamic DNS
  • Configuring Advanced DNS Server Parameters
  • Examining Zones with Nslookup
  • Command-Line Management of DNS
  • Configuring DHCP to Support DNS
  • Moving Forward
  • Overview of DNS Domain Structure
  • Functional Description of DNS Query Handling
  • Designing DNS Domains
  • Active Directory Integration
  • Configuring DNS Clients
  • Installing and Configuring DNS Servers
  • Configuring Secondary DNS Servers
  • Integrating DNS Zones into Active Directory
  • Chapter 6. Understanding Active Directory Services
  • New Features in Windows Server 2003
  • Active Directory Support Files
  • Active Directory Utilities
  • Bulk Imports and Exports
  • Moving Forward
  • Limitations of Classic NT Security
  • Directory Service Components
  • Brief History of Directory Services
  • X.500 Overview
  • LDAP Information Model
  • LDAP Namespace Structure
  • Active Directory Namespace Structure
  • Active Directory Schema
  • Chapter 7. Managing Active Directory Replication
  • New Features in Windows Server 2003
  • Replication Overview
  • Detailed Replication Transaction Descriptions
  • Designing Site Architectures
  • Configuring Inter-site Replication
  • Controlling Replication Parameters
  • Special Replication Operations
  • Troubleshooting Replication Problems
  • Moving Forward
  • Chapter 8. Designing Windows Server 2003 Domains
  • New Features in Windows Server 2003
  • Design Objectives
  • DNS and Active Directory Namespaces
  • Domain Design Strategies
  • Strategies for OU Design
  • Flexible Single Master Operations
  • Domain Controller Placement
  • Moving Forward
  • Chapter 9. Deploying Windows Server 2003 Domains
  • New Features in Windows Server 2003
  • Preparing for an NT Domain Upgrade
  • In-Place Upgrade of an NT4 Domain
  • In-Place Upgrade of a Windows 2000 Forest
  • Migrating from NT and Windows 2000 Domains to Windows Server 2003
  • Additional Domain Operations
  • Moving Forward
  • Chapter 10. Active Directory Maintenance
  • New Features in Windows Server 2003
  • Loss of a DNS Server
  • Loss of a Domain Controller
  • Loss of Key Replication Components
  • Backing Up the Directory
  • Performing Directory Maintenance
  • Moving Forward
  • Chapter 11. Understanding Network Access Security and Kerberos
  • New Features in Windows Server 2003
  • Windows Server 2003 Security Architecture
  • Security Components
  • Password Security
  • Authentication
  • Analysis of Kerberos Transactions
  • MITv5 Kerberos Interoperability
  • Security Auditing
  • Moving Forward
  • Chapter 12. Managing Group Policies
  • New Features in Windows Server 2003
  • Group Policy Operational Overview
  • Managing Individual Group Policy Types
  • Moving Forward
  • Chapter 13. Managing Active Directory Security
  • New Features in Windows Server 2003
  • Overview of Active Directory Security
  • Using Groups to Manage Active Directory Objects
  • Service Accounts
  • Using the Secondary Logon Service and RunAs
  • Using WMI for Active Directory Event Notification
  • Moving Forward
  • Chapter 14. Configuring Data Storage
  • New Features in Windows Server 2003
  • Functional Description of Windows Server 2003 Data Storage
  • Performing Disk Operations on IA32 Systems
  • Recovering Failed Fault Tolerant Disks
  • Working with GPT Disks
  • Moving Forward
  • Chapter 15. Managing File Systems
  • New Features in Windows Server 2003
  • Overview of Windows Server 2003 File Systems
  • NTFS Attributes
  • Link Tracking Service
  • Reparse Points
  • File System Recovery and Fault Tolerance
  • Quotas
  • File System Operations
  • Moving Forward
  • Chapter 16. Managing Shared Resources
  • New Features in Windows Server 2003
  • Functional Description of Windows Resource Sharing
  • Configuring File Sharing
  • Connecting to Shared Folders
  • Resource Sharing Using the Distributed File System (Dfs)
  • Printer Sharing
  • Configuring Windows Server 2003 Clients to Print
  • Managing Print Services
  • Moving Forward
  • Chapter 17. Managing File Encryption
  • New Features in Windows Server 2003
  • File Encryption Functional Description
  • Certificate Management
  • Encrypted File Recovery
  • Encrypting Server-Based Files
  • EFS File Transactions and WebDAV
  • Special EFS Guidelines
  • EFS Procedures
  • Moving Forward
  • Chapter 18. Managing a Public Key Infrastructure
  • New Features in Windows Server 2003
  • Moving Forward
  • PKI Goals
  • Cryptographic Elements in Windows Server 2003
  • Public/Private Key Services
  • Certificates
  • Certification Authorities
  • Certificate Enrollment
  • Key Archival and Recovery
  • Command-Line PKI Tools
  • Chapter 19. Managing the User Operating Environment
  • New Features in Windows Server 2003
  • Side-by-Side Assemblies
  • User State Migration
  • Managing Folder Redirection
  • Creating and Managing Home Directories
  • Managing Offline Files
  • Managing Servers via Remote Desktop
  • Moving Forward
  • Chapter 20. Managing Remote Access and Internet Routing
  • New Features in Windows Server 2003
  • Configuring a Network Bridge
  • Configuring Virtual Private Network Connections
  • Configuring Internet Authentication Services (IAS)
  • Moving Forward
  • Functional Description of WAN Device Support
  • PPP Authentication
  • NT4 RAS Servers and Active Directory Domains
  • Deploying Smart Cards for Remote Access
  • Installing and Configuring Modems
  • Configuring a Remote Access Server
  • Configuring a Demand-Dial Router
  • Configuring an Internet Gateway Using NAT
  • Chapter 21. Recovering from System Failures
  • New Features in Windows Server 2003
  • Functional Description Ntbackup
  • Backup and Restore Operations
  • Recovering from Blue Screen Stops
  • Using Emergency Management Services (EMS)
  • Using Safe Mode
  • Restoring Functionality with the Last Known Good Configuration
  • Recovery Console
  • Moving Forward
  • Who Should Read This Book
  • Who This Book Is Not For
  • Conventions
  • Acknowledgments
  • About the Author
  • About the Technical Reviewers
  • Index
  • Index A
  • Index B
  • Index C
  • Index D
  • Index E
  • Index F
  • Index G
  • Index H
  • Index I
  • Index J
  • Index K
  • Index L
  • Index M
  • Index N
  • Index O
  • Index P
  • Index Q
  • Index R
  • Index S
  • Index SYMBOL
  • Index T
  • Index U
  • Index V
  • Index W
  • Index X
  • Index Z
  • Preface
  • Previous Section Next Section

    NT4 RAS Servers and Active Directory Domains

    There's one more item of business left to cover before starting to deploy Windows Server 2003 remote access servers, and that's how to deal with any classic NT4 RAS servers that might be still be in production. Unless you make special accommodations for these RAS servers, they will not be able to authenticate dial-up users in an Active Directory domain. The reason for this harkens back to the origins of Windows networking in LanMan Server.

    As we've seen, MS-CHAPv2 requires that the remote access server obtain the user's NT password hash to complete the authentication transaction. The NT4 RAS server makes its call to the domain controller to get the user's credentials, but the domain controller says, "Not so fast, buddy. Let me see some Kerberos credentials, first, before I let you touch Active Directory."

    Well, NT4 doesn't know diddly about Active Directory and it keeps submitting its tried-and-true connection request until it finally gives up and returns an Access Denied message to the user.

    Null Sessions

    It's a little mystifying at first to figure out why this happens because a user at an NT4 server is able to access Active Directory without a hitch. The problem lies with the security context of the RAS service, which runs under the aegis of the Local System account. The Local System account on a Windows computer has no SID and therefore it cannot make a normal connection to a domain controller.

    In an NT4 domain, this lack of security context is not a problem because the RAS service can make a null session connection to the domain controller. A null session is a special type of connection in which a connecting entity that presents no credentials whatsoever is given limited access permissions on a server. The NT4 RAS server uses a null session connection to perform an impersonation of the user to the extent necessary to look up the user's credentials and dial-up permissions in the SAM and LSA databases.

    Windows Server 2003 and Windows 2000 domain controllers do not permit null session connections to touch Active Directory. This avoids certain notorious exploits that have plagued (and continue to plague) classic NT. A Kerberos-enabled remote access server is able to access Active Directory by using the Kerberos credentials obtained by the underlying computer account. The RAS service on an NT4 server is not that fortunate because the underlying computer has no means of obtaining Kerberos credentials.

    So we have a stalemate of sorts. The workaround involves a group with the long but appropriate name of Pre-Windows 2000 Compatible Access. This group has Read access to the following User attributes in Active Directory:

    • Remote Access Information

    • General Information

    • Logon Information

    • Group Membership

    • Account Restrictions

    The group also has the following permissions for Group objects:

    • Read All Properties

    • List Contents

    • Read Permissions

    What is the net result? These permissions give members of the Pre-Windows 2000 Compatible Access group the ability to obtain a user's logon credentials, account restrictions, and group membership, all the information needed to validate an MS-CHAPv2 authentication.

    Anonymous Access

    Now comes the ugly part. Because NT4 RAS servers have no Kerberos identity, you cannot simply put their computer objects in the Pre-Windows 2000 Compatible Access group and expect dial-in authentication to work. You must open the door to null session connections across the board by making the Anonymous Logon group a member of the Pre-Windows 2000 Compatible Access group.

    This is a change from Windows 2000, where it was necessary to add the Everyone group rather than the Anonymous Logon group to the Pre-Windows 2000 Compatible Access group. This is due to a change in the way Windows Server 2003 handles null session connections. In legacy Windows, including Windows 2000, the null session connection was assigned membership in the Everyone group by default. This was accomplished by putting the well-known SID representing Everyone into the access token that was auto-generated for null session connections.

    In Windows Server 2003, null sessions are not put in the Everyone group. This stymies many of the null session port scanners that circulate around the Internet for use in hacking Windows networks. The Anonymous Logon group is a new well-known RID in Windows Server 2003 that is tied to the domain, as contrasted with the Everyone group SID, which is the same for any domain.

    During Dcpromo, the utility that promotes a server running Windows Server 2003 to a domain controller, there is an option that asks whether or not to maintain Windows 2000 compatibility. This option controls whether the Anonymous Logon group is added to the Pre-Windows 2000 Compatible Access group. (The Everyone group is also added for backward compatibility with Windows 2000.)

    Additionally, because the NT4 RAS server must query for specific attributes in user and group objects rather than the entire object itself, as is done in classic NT, the NT4 RAS server must be running Service Pack 4 or later. This service pack contains changes to RLOGON and other functions that permit NT to read specific attributes.

    Anonymous Access and Active Directory Security

    Leaving a null session connection capable of reading Active Directory, even for the limited number of attributes controlled by the Pre-Windows 2000 Compatible Access group, represents a vulnerability that you should avoid. For this reason, you should upgrade your NT4 RAS servers to Windows Server 2003 or Windows 2000 prior to migrating your domain to Active Directory.

    If you should choose to retain Windows 2000 compatibility for sake of your NT4 RAS servers then later upgrade those servers to Windows Server 2003, you can eliminate the null session vulnerability by removing the Anonymous Logon and Everyone groups from the Pre-Windows 2000 Compatible Access group.

    IMPORTANT: You must restart every domain controller after you've made this change to stop Anonymous Logon from reading Active Directory.

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