Certificate-Based Authentication Changes and Always On VPN

Microsoft introduced important changes affecting certificate-based authentication on Windows domain controllers as part of the May 10, 2022 update KB5014754 that may affect Always On VPN deployments. The update addresses privilege escalation vulnerabilities when a domain controller is processing a certificate-based authentication request. The recommendation from Microsoft is that the update be applied to all Windows domain controllers and Active Directory Certificate Services (AD CS) servers as soon as possible.

Updated 5/20/2022: An out-of-band update to address authentication issues reported with this update is now available. Updates are available for Windows Server 2022, Windows Server 20H2, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2 SP1, and Windows Server 2008 SP2.

Certificate Services

After applying the update to certification authority (CA) servers, a non-critical extension with Object Identifier (OID) 1.3.6.1.4.1.311.25.2 is added to all issued certificates with the user or device security identifier (SID) included. Domain controllers with the update installed will use this information to validate the certificate used for authentication and ensure that it matches the information in Active Directory.

Domain Controllers

The update operates in Compatibility Mode, by default, when applied to domain controllers. Windows monitors authentication requests and records audit events for certificates presented for authentication under the following conditions.

No strong mapping (event ID 39) – The certificate has not been mapped explicitly to a domain account, and the certificate did not include the new SID extension.

Certificate predates account (event ID 40) – A certificate was issued before the user existed in Active Directory, and no explicit mapping could be found.

User’s SID does not match certificate (event ID 41) – A certificate contains the new SID extension, but it does not match the SID of the corresponding user account.

Certificate Mapping

Administrators can map certificates explicitly to accounts in Active Directory, but this results in a significant administrative burden in most environments. A better option is to reissue user and device authentication certificates after applying the KB5014754 update to all issuing CA servers.

Reenroll Certificates

Administrators should reissue user and device authentication certificates after applying the KB5014754 update. Open the Certificate Templates management console (certtmpl.msc), identify the user or device authentication certificate template, then right-click on the template and choose Reenroll All Certificate Holders.

Enforcement Mode

After applying update KB5014754, administrators should monitor domain controller event logs for event IDs 39, 40, and 41. Once all certificates have been updated, and none of these events have been recorded for 30 days, administrators can switch to Full Enforcement Mode by enabling it in the registry on all domain controllers.

Key: HKLM\SYSTEM\CurrentControlSet\Services\KDC
Value: StrongCertificateBindingEnforcement
Type: DWORD
Data: 2

Note: Microsoft will automatically switch to Full Enforcement Mode beginning May 9, 2023.

Known Issues

There have been some reports of authentication issues after installing the KB5014754 update. Early indications are that device authentication certificates missing a Subject Alternative Name (SAN) entry are to blame. Administrators are encouraged to update their device certificates to include the SAN entry. Optionally, but not recommended, administrators can place the update in disabled mode by editing the registry.

Note: An out-of-band update for these authentication issues is now available. See the reference links at the top of this article for more information.

Additional Information

KB5014754 – Certificate-based authentication changes on Windows domain controllers

Microsoft Windows Always On VPN Users Prompted for Certificate

Microsoft Windows Always On VPN Clients Prompted for Authentication when Accessing Internal Resources

Always On VPN at MMSMOA 2022

I am excited to announce that I will be presenting at this year’s Midwest Management Summit at the Mall of America (MMSMOA) in Bloomington, Minnesota. The conference takes place the week of May 2. This is my first time presenting at this event, and I’m looking forward to sharing my experience deploying enterprise mobility and security infrastructure solutions with systems management professionals from around the world.

Sessions

I will be delivering three talks at the conference addressing various secure remote access and certificate services topics.

Managing Always On VPN with Intune

This session will provide administrators with everything they need to know about provisioning and managing Always On VPN client configuration settings using Intune. I’ll be providing tips, tricks, and best practices for Always On VPN profile configuration and demonstrating many of the limitations associated with using Intune. I will provide workarounds whenever possible.

Managing Always On VPN with Intune: The Good, The Bad, and the Ugly

Always On VPN Gateway Options in Azure

Deploying Always On VPN in Azure is increasingly common. However, administrators are unaware of the limitations of supporting Always On VPN connections with native Azure VPN gateway solutions. In this session, I’ll describe in detail what’s required to support Always On VPN and, importantly, what the limitations are.

Always On VPN Gateway Options in Azure

Deploying On-premises PKI Certificates with Intune

As organizations continue to migrate applications, services, and infrastructure to the cloud, the requirement for endpoints to be joined to an on-premises domain is fading. Moving to full Intune management and native Azure Active Directory join for endpoints is increasingly common. However, deploying enterprise PKI certificates o these endpoints is often required. This session will provide detailed guidance for choosing the best solution to deliver on-premises certificates to Azure AD joined devices using Intune.

Deploying on-premises PKI Certificates with Intune

Let’s Connect

I’m looking forward to meeting so many folks who have helped me get up to speed with Microsoft Endpoint Manager/Intune over the years. If you’re attending the conference, or if you are in the area, be sure to reach out. Let’s grab a beer and chat!

Additional Information

Midwest Management Summit at Mall of America (MMSMOA) 2022

Managing Always On VPN with Intune: The Good, The Bad, and the Ugly

Always On VPN Gateway Options in Azure

Deploying on-premises PKI Certificates with Intune

Always On VPN with Active Directory Group Policy

Windows Always On VPN is a workload explicitly designed to be implemented and managed using Microsoft Endpoint Manager/Intune. While this is the best way to deploy and manage Always On VPN client configuration settings, it is not the only way. Administrators can also use System Center Configuration Manager (SCCM) by deploying a PowerShell script and XML configuration file to configure Always On VPN. Of course, it’s always possible to run the PowerShell script on individual machines.

Group Policy

Until now, there have been few options for deploying and managing Windows Always On VPN using Active Directory and group policy. This presents a challenge for administrators who still rely on group policy to manage their endpoints. It is possible to deploy the PowerShell script and XML configuration file using a group policy startup script. However, there are many limitations to this approach. Administrators must learn to properly configure the XML file and manage any configuration updates post-implementation.

Always On VPN DPC

The folks at PowerON Platforms have developed the Always On VPN Dynamic Profile Configurator (DPC) to address these shortcomings. Always On VPN DPC allows administrators to deploy and manage Always On VPN client configuration settings using Active Directory and group policy. Their software comes with Active Directory group policy templates that include all the necessary settings and client software that manages the configuration on the endpoint.

Advanced Features

Always On VPN DPC includes advanced features not included in Microsoft Endpoint Manager/Intune or XML. Here’s a sample of helpful custom settings that can be configured using Always On VPN DPC.

  • VpnStrategy
  • Interface metrics
  • Route metrics
  • Dynamically updated Office 365 exclusion route list
  • IKE mobility settings
  • IPv6 routes
  • And more…

Videos

I’ve created a brief introduction video for PowerOn Platforms Always On VPN DPC on YouTube. Soon I’ll be releasing additional videos that cover the installation and configuration of Always On VPN DPC and some of its advanced features, so be sure to subscribe to my YouTube channel.

Learn More

Are you interested in learning more about PowerON Platforms Always On VPN DPC? Fill out the form below, and I’ll contact you with more information. In addition, you can visit aovpndpc.com to register for an evaluation license.

Special Thanks

I want to extend a special thank you to Leo D’Arcy and the entire team at PowerON Platforms for allowing me to preview this software before its wide release. Also, I’m honored that you have graciously accepted my input and feedback for this solution. I’m consistently amazed at how rapidly you’ve corrected issues and implemented new features at my behest. You are all amazing. Thanks again! 😁

Additional Information

AovpnDPC.com

Introducing PowerON Platforms Always On VPN DPC on YouTube.com

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