Always On VPN Device Tunnel Issues with April 2024 Security Update

Always On VPN administrators may find that their device tunnel connections no longer connect automatically after applying the April 2024 security updates. The device tunnel connection is optional and only required under specific conditions, so end users may not be immediately impacted. However, administrators should be aware of this issue.

Note: The issues outlined in this post have been resolved with the May 14, 2024, security updates.

Error Messages

When manually establishing an Always On VPN device tunnel connection using rapshone.exe or rasdial.exe, you may receive one of the following error messages.

Rasphone.exe

Error 0x80070057: The parameter is incorrect.

Rasdial.exe

Connecting to <Name of Device Tunnel>…The parameter is incorrect.

Affected Devices

The issue affects all supported versions of Windows with an Always On VPN device tunnel connection configured to require a specific Enhanced Key Usage (EKU) OID. Administrators can run the following PowerShell command to identify this configuration.

Get-VpnConnection -AllUserConnection -Name <Name of Device Tunnel> | Select-Object MachineCertificateEkuFilter

If the output of this PowerShell command returns data, it is affected by this issue.

Workaround

To restore Always On VPN device tunnel functionality on devices with the April 2024 security updates installed, open an elevated PowerShell command window and run the following command.

Set-VpnConnection -AllUserConnection -Name ‘Always On VPN Device Tunnel’ -MachineCertificateEKUFilter $Null

After running this command, the output should now be blank.

Caveat

The problem with implementing the workaround described here is that you likely enabled this configuration to address an issue where the wrong certificate was selected for use with the device tunnel. In this case, the workaround may result in unexpected behavior and may not restore full functionality.

Known Issue Rollback

Currently, Microsoft is aware of the issue and is actively working to resolve it. If you are experiencing this issue, open a support case with Microsoft, and they will provide you with more information and possibly a private Known Issue Rollback (KIR). I will update this post as soon as Microsoft publishes a permanent fix.

Additional Information

Always On VPN Device Tunnel Operation and Best Practices

Always On VPN Device Tunnel Only Deployment Considerations

Considerations for Always On VPN with Azure VPN Gateway and Virtual WAN

Microsoft Intune Cloud PKI

Recently, Microsoft introduced the general availability of its new PKI-as-a-service solution called Microsoft Intune Cloud PKI. Cloud PKI allows administrators to issue and manage user and device authentication certificates for Intune-managed endpoints without deploying Active Directory Certificate Services (AD CS) on-premises. Cloud PKI frees administrators from the burdens of deploying and managing AD CS, including the complicated Network Device Enrollment Service (NDES) server configuration required for Simple Certificate Enrollment Protocol (SCEP) certificate deployment with Intune.

Advantages

Microsoft Intune Cloud PKI offers many significant advantages over traditional on-premises AD CS deployments.

No Infrastructure

The most obvious advantage of using Cloud PKI is that you do not have to deploy and manage your own Certification Authority (CA). Although implementing AD CS isn’t that difficult, managing and operating a CA infrastructure securely can be quite challenging. In addition, a high-security AD CS deployment utilizes hardware secure modules (HSMs) to protect CA private keys, which are quite expensive and sometimes difficult to support.

Cloud-Hosted SCEP

Removing the requirement to configure and deploy your own NDES server to support SCEP certificates is certainly a welcome advantage. NDES is notoriously difficult to configure, secure, and troubleshoot when it doesn’t work correctly. Cloud PKI includes cloud hosted SCEP services that are highly available and redundant within the Microsoft Azure infrastructure.

Automatic Revocation

Cloud PKI automates the deployment of certificates to Intune-managed users and devices and automatically revokes certificates when they fall out of scope. Administrators can also manually revoke certificates using the Intune management console.

Reporting

Administrators can easily view the status of Cloud PKI-issued certificates in Intune. The UI shows the active, expired, and revoked certificates for the issuing CA.

Clicking View all certificates shows a detailed list of all certificates.

BYOCA

Another compelling feature of Cloud PKI is Bring Your Own CA (BYOCA). This feature enables administrators to deploy a cloud-hosted CA that is chained to their existing on-premises AD CS root CA. This is helpful for scenarios where AD CS is already in place and used to issue and manage certificates to existing domain-joined clients and servers. BYOCA effectively allows you to extend your existing CA infrastructure to the cloud and use Cloud PKI to issue and manage certificates for your Intune-managed endpoints while maintaining the full functionality and feature set of on-premises AD CS for non-Intune-managed devices.

Limitations

Although there are many advantages to Cloud PKI, there are some limiting factors to consider.

RSA Only

Today, Cloud PKI is limited to RSA keys only. Administrators can create CAs using RSA 2048, 3072, or 4096-bit keys. Elliptic Curve (EC) keys are not currently supported in Cloud PKI.

Intune Devices Only

Cloud PKI is limited to issuing certificates to Intune-managed devices only. Endpoints must be Entra-joined, or hybrid Entra-joined to enroll for certificates using Cloud PKI.

Inflexible Configuration

The Cloud PKI root and issuing CAs cannot be reconfigured after deployment. Since Cloud PKI root and issuing CAs don’t support the Any Purpose EKU (2.5.29.37.0), all EKUs must be defined when the CA is created. If, in the future, an administrator requires an EKU that was not present when the CA was deployed, an entirely new hierarchy (root and issuing CA) must be deployed.

No Strong Mapping

As of this writing, Cloud PKI does not yet support strong certificate mapping for KB5014754. Microsoft fixed this limitation with Entra Conditional Access certificates and is working to include support for SCEP and PKCS. Hopefully, this shortcoming will be addressed soon in Cloud PKI.

Cost

There’s been much discussion about the cost associated with Cloud PKI. Cloud PKI can be licensed as part of the Intune Suite, which is $10.00 per user per month. Cloud PKI licenses will also be available as a standalone add-on for $2.00 per user per month. For large organizations, this might be cost-prohibitive.

Summary

Overall, Microsoft Intune Cloud PKI is a welcome addition to the Microsoft suite of cloud services. Certificates are excellent phishing-resistant credentials that can be used to improve security for organizations of all sizes. However, managing a CA can be tedious and time-consuming. Leveraging the cloud for PKI and certificate management will be helpful in many scenarios. However, Cloud PKI has some potential drawbacks, and many may not fit everyone.

More Information

Want to learn more about Microsoft Intune Cloud PKI and how it can benefit your organization? Take the first step towards streamlined certificate management and enhanced security for your organization. Fill out the form below, and I’ll provide more information about using Intune Cloud PKI to safeguard your digital assets confidently.

Mastering Certificates with Intune Training Course

I’m excited to announce I’ll present a three-day LIVE online training event covering all things Microsoft Intune and certificates. This training event takes place on the ViaMonstra online academy May 14-16, 2024.

Course Material

This training course comprehensively examines all aspects of delivering certificates using Microsoft Intune, including common deployment scenarios, PKCS and SCEP configuration, Intune certificate connector configuration, high availability strategies, implementation and security best practices, and troubleshooting.

Cloud PKI

Cloud PKI, a new cloud-based PKI-as-a-Service solution from Microsoft, will also be covered in depth. I’ll provide an overview of the service and discuss the advantages and limitations of Cloud PKI. We’ll also cover different configuration and deployment scenarios, including Bring Your Own CA (BYOCA). In addition, I’ll share security best practices for Microsoft Cloud PKI deployments.

Register Now

Space is limited, so don’t miss out on this excellent opportunity to learn about these critically essential technologies. Reserve your spot in this training class today!

Additional Information

Mastering Certificates and Microsoft Intune

Microsoft Cloud PKI

ViaMonstra Online Academy