Strong Certificate Mapping for Intune PKCS and SCEP Certificates

Always On VPN LockDown Mode

With the October 2024 Intune update, Microsoft introduced support for strong certificate mapping for certificates issued by Intune via the Intune Certificate Connector. Enabling strong certificate mapping support in Intune is an important change for those organizations using Microsoft Intune to issue and manage certificates for their users and devices, as it resolves a critical implementation blocker.

Note: This post was updated to clarify that adding the {{OnPremisesSecurityIdentifier}} for PKCS certificates is not required. This variable is only used for SCEP certificates.

Background

In May 2022, Microsoft released security update KB5014754, which added functionality to domain controllers and enterprise issuing certification authority (CA) servers, allowing the Kerberos Key Distribution Center (KDC) to enforce strong certificate mapping. Specifically, with KB5014754 installed, issuing CAs now add the requesting principal’s Security Identifier (SID) to the certificate in a new certificate extension. Domain controllers can be configured to reject authentication requests using certificates that do not include this information.

Today, DCs with KB5014754 installed will still allow authentication without strong certificate mapping. However, Microsoft has stated they will begin enforcing strong certificate mapping in February 2025, with an option to disable it via the registry. Starting in September 2025, full enforcement will be mandatory.

Reference: https://support.microsoft.com/en-us/topic/kb5014754-certificate-based-authentication-changes-on-windows-domain-controllers-ad2c23b0-15d8-4340-a468-4d4f3b188f16

Limitation

The initial changes in KB5014754 applied only to online certificate templates, meaning those that build the subject name from Active Directory. However, deploying certificates with Intune using either PKCS or SCEP requires using an offline certificate template that allows the requestor to supply the subject name in the request. When using offline templates, a certificate is issued but does not embed the SID in the certificate. Using offline templates presents unique challenges to organizations moving to modern management with Intune and Entra ID.

Intune Changes

The October 2024 Intune update addresses this limitation by providing a method to include SID information in certificates using either SCEP or PKCS.

SCEP

To include the SID information in SCEP certificates, create or edit an existing SCEP device configuration policy and define a URI Subject Alternative Name (SAN) attribute with the value {{OnPremisesSecurityIdentifier}} as shown here.

PKCS

To include SID information in PKCS certificates, administrators must ensure the Intune Certificate Connector is updated to at least version 6.2406.0.1001. In addition, a registry setting must be enabled on the Intune Certificate Connector server.

On the server where the Intune Certificate Connector is installed, open the registry editor, navigate to HKLM\Software\Microsoft\MicrosoftIntune\PFXCertificateConnector, and change the value of EnableSidSecurityExtension to 1.

Optionally, administrators can update this setting at the command line by running the following PowerShell command.

Set-ItemProperty -Path ‘HKLM:\SOFTWARE\Microsoft\MicrosoftIntune\PFXCertificateConnector’ -Name EnableSidSecurityExtension -Value 1 -Force

Once complete, restart the Intune Certificate Connector server for the changes to take effect.

Certificates

SID information is added to certificates differently depending on which Intune device configuration policy type is used.

PCKS

PKCS certificates have the SID embedded in the certificate extension 1.3.6.1.4.1.311.25.2, as shown here.

SCEP

SCEP certificates have the SID embedded in the Subject Alternative Name (SAN) field in the format “tag:microsoft.com,2022-09-14:sid:<SID>” as shown here.

Migration

When making these changes to embed the SID in Intune-issued certificates in an existing Intune PKCS or SCEP configuration policy, the change will only affect certificates issued after the change is made. To update all certificate holders, you must create and deploy a new device configuration policy to targeted users or devices. Deleting the old profile (or ensuring it no longer applies) will remove the old certificate from the endpoint. If you’ve configured your Intune Certificate Connector to support revocation, the old certificate will also be revoked.

Entra Conditional Access

Entra Conditional Access certificates have included SID information since July 2023. More details here.

Intune Cloud PKI

The changes above will also work with certificates issued by Cloud PKI for Intune.

Other Cloud PKI Providers

Many other Cloud PKI providers, such as SCEPman and KEYTOS, already include the embedded SID in their certificates. Other cloud PKI providers may also include embedded SID. Consult your provider to confirm.

Additional Information

Microsoft Intune October 2024 Strong Certificate Mapping Update

Microsoft Intune Certificate Connector Strong Certificate Mapping Update for PKCS

Entra ID Conditional Access Certificates with SID Information Now Available

Implementing Strong Certificate Mapping in Microsoft Intune PKCS and SCEP Certificates

Certificate-Based Authentication Changes and Always On VPN

Always On VPN Disconnects in Windows 11

Always On VPN administrators migrating their endpoints to Windows 11 may encounter a scenario where Always On VPN randomly disconnects when the VPN profile is deployed using Microsoft Intune. The same configuration deployed to Windows 10 devices works reliably, however. In addition, Always On VPN profiles deployed using PowerShell (natively or with SCCM) or Dynamic Profile Configurator (DPC) do not experience this problem.

Troubleshooting

Administrators troubleshooting this issue will find the root cause is associated with the Always On VPN profiles being removed and replaced each time the device syncs with Intune. This occurs even if there are no changes to the configuration. Removing and replacing the Always On VPN profiles on each device sync is unnecessary, of course, but is also highly disruptive to connected users.

Intune and XML

The Intune team identified the issue, and a fix was made available in the August update. However, many of you have reported the issue persists with some Windows 11 clients after installing the latest updates. Further investigation indicates that although the issue has been resolved when using Intune and the native VPN device configuration profile template, the problem still occurs when using the Custom device configuration template.

Workaround

Microsoft is aware of the issues with deploying Always On VPN client configuration settings using XML in Intune, but there’s no indication when or if they will fix it. Until then, administrators have two options to address this problem.

Native VPN Template

When deploying Always On VPN client configuration settings to Windows 11 endpoints, use the native VPN device configuration template, as shown here.

Using the native VPN template does have some limitations, however. The following settings are not exposed using the native VPN template and can only be configured using XML.

XML

If you must use XML, I’ve had some success by ensuring the order and syntax of XML settings is exactly as Intune expects. Follow the steps below to confirm the XML settings order in your XML configuration file.

  1. Deploy your XML file with Intune.
  2. Run Get-VpnClientProfileXML.ps1 to extract the deployed XML settings.
  3. Compare the order of settings to your existing XML.
  4. Compare the syntax of all settings. For example, the <Servers> section should list the server FQDN twice, separated by a semi-colon.
  5. Make changes to ensure all settings in your XML are in the same order as the extracted XML.
  6. Publish a new XML configuration file using Intune and test.

I’ll caution you that this workaround doesn’t always work reliably. Some customers report that this solved their problems entirely, while others have indicated it does not. My testing shows the same results. Let us know in the comments below if this works for you!

Reference XML

I have published an Always On VPN XML configuration file on GitHub for reference. It includes all common settings using the order and syntax required to ensure reliable operation. As a reminder, the sample file includes many settings that aren’t required. It is published as guidance for reference only.

Additional Information

Always On VPN Windows 11 Issues with Intune

Always On VPN PowerShell Script Issues in Windows 11

Always On VPN at MMSMOA 2023

I’m excited to share that I’ve been invited to present at the popular Midwest Management Summit at Mall of America (MMSMOA) this year! The event takes place Monday, May 2, through Thursday, May 4, 2023.

Sessions

I will be delivering two talks at the event this year. One on Microsoft Always On VPN and Intune, the other on deploying certificate using Intune.

Always On VPN and Intune: Notes from the FieldTuesday, May 2 at 10:00 AM CDT

This session will cover all aspects of deploying and managing Always On VPN client configuration settings using Microsoft Intune.

Intune Certificate ManagementWednesday, May 3 at 10:00 AM CDT

This session will provide detailed configuration guidance and best practice recommendations for issuing on-premises enterprise PKI certificate using Microsoft Intune.

Attending MMS?

Will you be attending MMSMOA? Let’s connect! Drop in on my sessions, of course, but let’s plan to hang out! I will have copies of my book to give away too, so don’t miss out. Send me a note here or on Twitter, or just find me at the conference. Looking forward to seeing all of you soon!