Always On VPN Updates for Windows 10 2004

Always On VPN Updates for Windows 10 2004Microsoft recently made available an update for Windows 10 2004 that includes many important fixes for outstanding issues with Windows 10 Always On VPN. KB4571744 (build 19041.488) addresses many challenges faced by Always On VPN administrators today, including the following.

TPM

This update addresses an issue that prevents hash signing from working correctly using the Microsoft Platform Crypto Provider for Trusted Platform Module (TPM). This issue can occur when administrators configure Always On VPN to use Protected Extensible Authentication Protocol (PEAP) with client certificate authentication using a FortiGate security device.

Sleep/Hibernate

This update also addresses issues with Windows 10 Always On VPN failing to automatically reconnect when resuming from sleep or hibernate. I’ve written about issues with Always On VPN and sleep/hibernate in the past. This is an issue that has plagued Always On VPN since its introduction, so let’s hope this finally provides some meaningful relief from this persistent problem.

Certificate Authentication

When both the Always On VPN device tunnel and user tunnel are provisioned to a Windows 10 clients, user tunnel connections may be authenticated using the machine certificate and not EAP/PEAP. This can result in connections that are not validated as intended, and allowing a user to bypass configured NPS policies, MFA requirements, or conditional access rules. This update includes a fix for this issue, restoring proper authentication for the user tunnel when the device tunnel is also provisioned.

Device and User Tunnel Coexistence

A bug that first appeared when Windows 10 2004 was introduced prevented a device tunnel and user tunnel Always On VPN connection from being established to the same VPN server if the user tunnel used Internet Key Exchange Version 2 (IKEv2). This update restores full functionality under those conditions.

Update KB4571744

To resolve these issues with Windows 10 Always On VPN as well as others, download and install update KB4571744 today. If you are experiencing any of these issues with releases of Windows 10 prior to 2004, look for updates for those build to come later this year.

Additional Information

September 3, 2020 – KB4571744 (OS Build 19041.488) Preview

Windows 10 Always On VPN Connection Issues after Sleep or Hibernate

Windows 10 Always On VPN Bug in Windows 10 2004

Always On VPN Device Tunnel Only Deployment Considerations

Always On VPN Device Tunnel Only Deployment ConsiderationsRecently I wrote about Windows 10 Always On VPN device tunnel operation and best practices, explaining its common uses cases and requirements, as well as sharing some detailed information about authentication, deployment recommendations, and best practices. I’m commonly asked if deploying Always On VPN using the device tunnel exclusively, as opposed to using it to supplement the user tunnel, is supported or recommended. I’ll address those topics in detail here.

Device Tunnel Only?

To start, yes, it is possible to deploy Windows 10 Always On VPN using only the device tunnel. In this scenario the administrator will configure full access to the network instead of limited access to domain infrastructure services and management servers.

Is It Recommended?

Generally, no. Remember, the device tunnel was designed with a specific purpose in mind, that being to provide pre-logon network connectivity to support scenarios such as logging on without cached credentials. Typically, the device tunnel is best used for its intended purpose, which is providing supplemental functionality to the user tunnel.

Deployment Considerations

The choice to implement Always On VPN using only the device tunnel is an interesting one. There are some potential advantages to this deployment model, but it is not without some serious limitations. Below I’ve listed some of the advantages and disadvantages to deploying the device tunnel alone for Windows 10 Always On VPN.

Advantages

Using the device tunnel alone does have some compelling advantages over the standard two tunnel (device tunnel/user tunnel) deployment model. Consider the following.

  • Single VPN Connection – Deploying the device tunnel alone means a single VPN connection to configure, deploy, and manage on the client. This also results in less concurrent connections and, importantly, less IP addresses to allocate and provision.
  • Reduced Infrastructure – The device tunnel is authenticated using only the device certificate. This certificate check is performed directly on the Windows Server Routing and Remote Access Service (RRAS) VPN server, eliminating the requirement to deploy Network Policy Server (NPS) servers for authentication.
  • User Transparency – The device tunnel does not appear in the modern Windows UI. The user will not see this connection if they click on the network icon in the notification area. In addition, they will not see the device tunnel connection in the settings app under Network & Internet > VPN. This prevents casual users from playing with the connection settings, and potentially deleting the connection entirely. It’s not that they can’t delete the device tunnel however, it’s just not as obvious.
  • Simplified Deployment – Deploying the device tunnel is less complicated than deploying the user tunnel. The device tunnel is provisioned once to the device and available to all users. This eliminates the complexity of having to deploy the user tunnel in each individual user’s profile.

Disadvantages

While there are some advantages to using the device tunnel by itself, this configuration is not without some serious limitations. Consider the following.

  • IKEv2 Only – The device tunnel uses the IKEv2 VPN protocol exclusively. It does not support SSTP. While IKEv2 is an excellent protocol in terms of security, it is commonly blocked by firewalls. This will prevent some users from accessing the network remotely depending on their location.
  • Limited OS Support – The device tunnel is only supported on Windows 10 Enterprise edition clients, and those clients must be joined to a domain. Arguably the device tunnel wouldn’t be necessary if the client isn’t domain joined, but some organizations have widely deployed Windows 10 Professional, which would then preclude them from being able to use the device tunnel.
  • Machine Certificate Authentication Only – The device tunnel is authenticated using only the certificate issued to the device. This means anyone who logs on to the device will have full access to the internal network. This may or may not be desirable, depending on individual requirements.
  • No Mutual Authentication – When the device tunnel is authenticated, the server performs authentication of the client, but the client does not authenticate the server. The lack of mutual authentication increases the risk of a man-in-the-middle attack.
  • CRL Checks Not Enforced – By default, RRAS does not perform certificate revocation checking for device tunnel connections. This means simply revoking a certificate won’t prevent the device from connecting. You’ll have to import the client’s device certificate into the Untrusted Certificates certificate store on each VPN server. Fortunately, there is a fix available to address this limitation, but it involves some additional configuration. See Always On VPN Device Tunnel and Certificate Revocation for more details.
  • No Support for Azure Conditional Access – Azure Conditional Access requires EAP authentication. However, the device tunnel does not use EAP but instead uses a simple device certificate check to authenticate the device.
  • No Support for Multifactor Authentication – As the device tunnel is authenticated by the RRAS VPN server directly and authentication requests are not sent to the NPS server, it is not possible to integrate MFA with the device tunnel.
  • Limited Connection Visibility – Since the device tunnel is designed for the device and not the user it does not appear in the list of active network connections in the Windows UI. There is no user-friendly connection status indicator, although the connection can be viewed using the classic network control panel applet (ncpa.cpl).

Summary

The choice to deploy Windows 10 Always On VPN using the device tunnel alone, or in conjunction with the user tunnel, is a design choice that administrators must make based on their individual requirements. Using the device tunnel alone is supported and works but has some serious drawbacks and limitations. The best experience will be found using the device tunnel as it was intended, as an optional component to provide pre-logon connectivity for an existing Always On VPN user tunnel.

Additional Information

Windows 10 Always On VPN Device Tunnel with Azure VPN Gateway

Windows 10 Always On VPN Device Tunnel and Certificate Revocation

Windows 10 Always On VPN Device Tunnel Configuration with Microsoft Intune

Windows 10 Always On VPN Device Tunnel Does Not Connect Automatically

Windows 10 Always On VPN Device Tunnel Missing in Windows 10 UI

Deleting a Windows 10 Always On VPN Device Tunnel

Windows 10 Always On VPN Device Tunnel Configuration using PowerShell

Windows 10 Always On VPN IKEv2 Features and Limitations

Always On VPN Error Code 858

Always On VPN Error Code 858When configuring Windows 10 Always On VPN using Extensible Authentication Protocol (EAP), the administrator may encounter a scenario in which the client connection fails. The event log will include an event ID 20227 from the RasClient source that includes the following error message.

“The user [domain\username] dialed a connection named [connection name] which has failed. The error code returned on failure is 858.”

Always On VPN Error Code 858

RasClient Error 858

RasClient error code 858 translates to ERROR_EAP_SERVER_CERT_EXPIRED. Intuitively, this indicates that the Server Authentication certificate installed on the Network Policy Server (NPS) has expired. To resolve this issue, renew the certificate on the NPS server.

Additional Information

Windows 10 Always On VPN Network Policy Server (NPS) Load Balancing

Windows 10 Always On VPN and Windows Server 2019 NPS Bug

Windows 10 Always On VPN Error Code 864

Microsoft Intune NDES Connector Error 0x80004003

Microsoft Intune NDES Connector Error 0x80004003To support certificate deployment for non-domain Windows 10 Always On VPN clients, a Windows Server with the Network Device Enrollment Service (NDES) role can be provisioned on-premises. In addition, the Microsoft Intune Connector must be installed and configured on the NDES server to allow Intune-managed clients to request and receive certificates from the on-premises Certification Authority (CA) server.

Connection Status Error

After installing the Microsoft Intune Connector, the administrator may encounter the following error message.

“An error occurred while connecting to the Intune Service. Error code is 0x80004003. The NDES Connector will retry the connection as soon as possible.”

 Microsoft Intune NDES Connector Error 0x80004003

IE Enhanced Security Configuration

This error can occur if Internet Explorer Enhanced Security Configuration (ESC) is enabled. To resolve this issue, disable ESC for administrators and users by opening the Server Manager on the NDES server and performing the following steps.

1. In the navigation pane click Local Server.
2. Click the On link next to IE Enhanced Security Configuration.
3. Click Off in the Administrators section.
4. Click Off in the Users section
5. Click Ok.

Microsoft Intune NDES Connector Error 0x80004003

Once complete, restart the NDES Connector service using the following PowerShell command.

Restart-Service NDESConnectorSvc -PassThru

Additional Configuration

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Microsoft Intune NDES Connector Setup Wizard Ended PrematurelyA Windows Server with the Network Device Enrollment Service (NDES) role can be provisioned on-premises to support certificate deployment for non-domain Windows 10 Always On VPN clients. In addition, the Microsoft Intune Connector must be installed and configured on the NDES server to allow Intune-managed clients to request and receive certificates from the on-premises Certification Authority (CA) server.

Setup Wizard Ended Prematurely

When installing the Microsoft Intune Connector, the administrator may encounter a scenario where the setup wizard fails with the following error message.

“Microsoft Intune Connector Setup Wizard ended prematurely because of an error. Your system has not been modified. To install this program at a later time, run Setup Wizard again. Click the Finish button to exit the Setup Wizard.”

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Cryptographic Service Provider

This error can occur if the NDES server certificate template is configured to use the Key Storage Provider cryptography service provider (CSP). When configuring the certificate template for the NDES server, the Legacy Cryptography Service Provider must be used, as shown here.

Microsoft Intune NDES Connector Setup Wizard Ended Prematurely

Additional Information

Deploying Windows 10 Always On VPN with Intune using Custom ProfileXML

Windows 10 Always On VPN Device Tunnel Configuration using Microsoft Intune

Deploying Windows 10 Always On VPN with Microsoft Intune

 

Always On VPN Device Tunnel and Certificate Revocation

Always On VPN Device Tunnel and Certificate RevocationRecently I wrote about denying access to Windows 10 Always On VPN users or computers. In that post I provided specific guidance for denying access to computers configured with the device tunnel. To summarize, the process involved exporting the device certificate from the issuing Certification Authority (CA) server and placing it in the Untrusted Certificates certificate store on each VPN server. In theory, simply revoking the device certificate should be all that’s required to prevent device tunnel connections.

Revocation Check Failure

As it turns out, a bug in Windows Server Routing and Remote Access prevents this from working as expected. Windows Server 2012 R2, 2016, and 2019 all fail to check the Certificate Revocation List (CRL) for IKEv2 VPN connections using machine certificate authentication (for example an Always On VPN device tunnel).

Updates for Windows Server

Microsoft has released fixes to support device tunnel certificate revocation for the following operating systems.

Windows Server 2019 – KB4505658 (build 17763.652)

Windows Server 2016 – KB4503294 (build 14393.3053)

Windows Server 2012/R2 – Will not be updated.

Enable Revocation Check

Additional configuration is required to enable support for CRL checking. Microsoft published guidance for configuring CRL revocation checks for IKEv2 VPN connections using machine certificate authentication here. Specifically, administrators must enable the RootCertificateNameToAccept parameter and set a registry key to enable this functionality.

Open an elevated PowerShell window and run the following commands to enable CRL checking for IKEv2 VPN connections using machine certificate authentication.

$Thumbprint = ‘Root CA Certificate Thumbprint’
$RootCACert = (Get-ChildItem -Path cert:\LocalMachine\root | Where-Object {$_.Thumbprint -eq $Thumbprint})
Set-VpnAuthProtocol -RootCertificateNameToAccept $RootCACert -PassThru

New-ItemProperty -Path ‘HKLM:\SYSTEM\CurrentControlSet\Services\RemoteAccess\Parameters\Ikev2\’ -Name CertAuthFlags -PropertyTYpe DWORD -Value ‘4’ -Force

Restart-Service RemoteAccess -PassThru

Always On VPN Device Tunnel and Certificate Revocation

A PowerShell script to update the RootCertificateNameToAccept parameter on multiple VPN servers can be found here.

Revoking Certificates

To prevent a Windows 10 Always On VPN device tunnel connection, the administrator must first revoke the certificate on the issuing CA. Next, open an elevated command window an enter the following commands. Repeat these steps on each VPN server in the enterprise.

certutil -urlcache * delete
certutil -setreg chain\ChainCacheResyncFiletime @now

Additional Information

Denying Access to Windows 10 Always On VPN Users or Computers

Blocking VPN Clients that use Revoked Certificates

PowerShell Script to Configure RootCertificateNameToAccept on GitHub

 

 

Always On VPN Users Prompted for Certificate

Always On VPN Users Prompted for CertificateWhen deploying Windows 10 Always On VPN using Protected Extensible Authentication Protocol (PEAP) authentication with client certificates, administrators may find the VPN connection does not establish automatically. In this specific scenario the client is prompted to select a certificate to use to authenticate to the VPN server.

Always On VPN Users Prompted for Certificate

Multiple Certificates

This can occur when certificates from multiple Certification Authorities (CAs) are issued to the user that include the Client Authentication Enhanced Key Usage (EKU). When this happens, the user is forced to select the correct certificate to use for VPN authentication.

Clearly this is less than ideal, as it not only breaks the seamless and transparent nature of Always On VPN, the user may select the wrong certificate resulting in authentication failure. Ideally the client should be configured to select the correct certificate without user interaction.

Certificate Selection

Follow the steps below to configure automatic certificate selection for VPN authentication.

  1. On a VPN client, right-click the Always On VPN connection and choose Properties.
  2. Select the Security tab.
  3. In the Authentication section click Properties below Use Extensible Authentication Protocol (EAP).
  4. In the Select Authentication Method section click Configure.
  5. In the When connecting section click Advanced.
  6. Check the box next to Certificate Issuer.
  7. Select the root CA used to issue client authentication certificates for VPN authentication.
  8. Click Ok four times to save the configuration.

Always On VPN Users Prompted for Certificate

Once complete, export the EAP configuration to XML from the VPN client and paste the new settings in Intune or in your custom ProfileXML.

Certificate Purpose

By default, a client certificate requires only the Client Authentication EKU to establish a VPN connection. In some cases, this may not be desirable. For example, consider a deployment where Client Authentication certificates are issued to all users for Wi-Fi authentication. Depending on the Network Policy Server (NPS) configuration, these certificates may also be used to authenticate to the VPN.

VPN Specific Certificate

Follow the steps below to create a user authentication certificate template to be used exclusively for VPN authentication.

Certificate Template

  1. On the CA server, open the Certificate Templates management console (certtmpl.msc).
  2. Right-click the certificate template configured for VPN authentication and choose Properties.
  3. Select the Extension tab.
  4. Highlight Application Policies and click Edit.
  5. Click Add.
  6. Click New.
  7. Enter a descriptive name for the new application policy.
  8. Copy the Object identifier for later use and click Ok four times to save the configuration.

    Always On VPN Users Prompted for Certificate

  9. If certificate autoenrollment is configured and the certificate is already provisioned to users, right-click the certificate template and choose Reenroll All Certificate holders.

Client Configuration

  1. On the VPN client, follow the steps outlined previously to configure certificate selection.
  2. In addition to choosing a certificate issuer, select Extended Key Usage (EKU).
  3. Uncheck All Purpose.
  4. Select Client Authentication and the following EKUs.
  5. Click Add.
  6. Click Add once more.
  7. Enter the name of the custom EKU policy created previously.
  8. Enter the custom EKU object identifier copied previously from the custom policy.

    Always On VPN Users Prompted for Certificate

  9. Click Ok twice.
  10. Uncheck AnyPurpose and the following EKUs.
  11. Click Ok four times to save the configuration.

Always On VPN Users Prompted for Certificate

Once complete, export the EAP configuration to XML from the VPN client and paste the new settings in Intune or in your custom ProfileXML.

Additional Information

Windows 10 Always On VPN Clients Prompted for Authentication when Accessing Internal Resources

Get-EapConfiguration PowerShell Script on GitHub

Windows 10 Always On VPN Hands-On Training

Always On VPN Clients Prompted for Authentication when Accessing Internal Resources

Always On VPN Clients Prompted for Authentication when Accessing Internal ResourcesWhen deploying Windows 10 Always On VPN using Protected Extensible Authentication Protocol (PEAP) with client authentication certificates, the administrator may encounter a scenario in which the user can establish a VPN connection without issue, but when accessing internal resources they are prompted for credentials and receive the following error message.

“The system cannot contact a domain controller to service the authentication request. Please try again later.”

Always On VPN Clients Prompted for Authentication when Accessing Internal Resources

Resolution

This can occur if one or more domain controllers in the enterprise have expired or missing domain controller authentication certificates. To ensure seamless single sign-on to internal resources, ensure that all domain controllers have a certificate issued by the internal certification authority (CA) that includes the Server Authentication (1.3.6.1.5.5.7.3.1), Client Authentication (1.3.6.1.5.5.7.3.2), KDC Authentication (1.3.6.1.5.2.3.5), and Smart Card Logon (1.3.6.1.4.1.311.20.2.2) Enhanced Key Usage (EKU). Administrators can duplicate the Kerberos Authentication template for this purpose.

Always On VPN Clients Prompted for Authentication when Accessing Internal Resources

Additional Information

Windows 10 Always On VPN Certificate Requirements for IKEv2

Windows 10 Always On VPN Hands-On Training

 

Renew DirectAccess Self-Signed Certificates

Renew DirectAccess Self-Signed CertificatesImportant! Updated April 29, 2020 to resolve an issue where the DirectAccess RADIUS encryption certificate was not published to the DirectAccess Server Settings GPO in Active Directory.

When DirectAccess is deployed using the Getting Started Wizard (GSW), sometimes referred to as the “simplified deployment” method, self-signed certificates are created during the installation and used for the IP-HTTPS IPv6 transition technology, the Network Location Server (NLS), and for RADIUS secret encryption. Administrators may also selectively choose to use self-signed certificates for IP-HTTPS, or when collocating the NLS on the DirectAccess server. The RADIUS encryption certificate is always self-signed.

Renew DirectAccess Self-Signed Certificates

Certificate Expiration

These self-signed certificates expire 5 years after they are created, which means many DirectAccess administrators who have used this deployment option will need to renew these certificates at some point in the future. Unfortunately, there’s no published guidance from Microsoft on how to accomplish this. However, the process is simple enough using PowerShell and the New-SelfSignedCertificate cmdlet.

PowerShell Script on GitHub

The PowerShell script to renew DirectAccess self-signed certificates has been published on GitHub. You can download Renew-DaSelfSignedCertificates.ps1 here.

Important Considerations

When the IP-HTTPS certificate is renewed using this script, DirectAccess clients outside will be immediately disconnected and will be unable to reconnect until they update group policy. This will require connecting to the internal network locally or remotely using another VPN solution. The NLS and RADIUS encryption certificates can be updated without impacting remote users.

In addition, internal clients that are not online when this change is made will be unable to access internal resources by name until they update group policy. If this happens, delete the Name Resolution Policy Table (NRPT) on the client using the following PowerShell command and reboot to restore connectivity.

Get-Item -Path “HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\DNSClient\DnsPolicyConfig” | Remove-Item -Confirm:$false

Additional Information

PowerShell Recommended Reading for DirectAccess Administrators

Top 5 DirectAccess Troubleshooting PowerShell Commands

 

 

Always On VPN and Azure MFA ESTS Token Error

Always On VPN and Azure MFA ESTS Token ErrorConfiguring Multifactor Authentication (MFA) is an excellent way to ensure the highest level of assurance for Always On VPN users. Azure MFA is widely deployed and commonly integrated with Windows Server Network Policy Server (NPS) using the NPS Extension for Azure MFA. Azure MFA has a unique advantage over many other MFA providers in that it supports MFA when using Protected Extensible Authentication Protocol (PEAP). This makes Azure MFA the solution of choice for integrating with Windows 10 Always On VPN deployments using client certificate authentication, a recommended security configuration best practice.

NPS Configuration

Installing and configuring the NPS extension for Azure MFA is straightforward. Configuration guidance from Microsoft can be found here.

Connection Issues

After installing the NPS extension for Azure MFA, administrators may find that Always On VPN connections fail and the user is never challenged for authentication. The connection eventually times out and returns the following error message.

“A connection to the remote computer could not be established, so the port used for this connection was closed.”

Always On VPN and Azure MFA ESTS Token Error

In addition, the Application event log on the Windows 10 client contains an Event ID 20221 from the RasClient source that includes the following error message.

“The user [username] dialed a connection named [connection] which has failed. The error code returned on failure is 0.”

Always On VPN and Azure MFA ESTS Token Error

NPS Event Log

Reviewing the event logs on the NPS server reveals more information. The Security event log contains an Event ID 6274 from the Microsoft Windows security auditing source that includes the following error message.

“Network Policy Server discarded the request for a user. Contact the Network Policy Administrator for more information.”

Always On VPN and Azure MFA ESTS Token Error

ESTS Token Error

Digging deeper in the operational event log on the NPS server, the AuthZAdminCh log (Applications and Services Logs > Microsoft > AzureMfa > AuthZ) contains an Event ID 3 from the AuthZ source indicating an ESTS_TOKEN_ERROR message.

Always On VPN and Azure MFA ESTS Token Error

Troubleshooting ESTS Token Error

Follow the steps below to troubleshoot the ESTS_TOKEN_ERROR.

Prerequisites

Ensure that all prerequisites are met. Validate the user is being synced to Azure Active Directory and that it is properly licensed for Azure MFA.

Certificates

As part of the NPS extension configuration, a certificate is created on the NPS server that is uploaded to Azure Active Directory. To validate the certificate was created and uploaded correctly, follow the troubleshooting guidance found here.

Enterprise Applications

The Azure Multi-Factor Auth Client and the Azure Multi-Factor Auth Connector enterprise applications must be enabled to support the NPS extension for Azure MFA. To confirm they are enabled, open an elevated PowerShell command window on the server where the Azure AD Connector is installed and run the following PowerShell commands.

Import-Module MSOnline
Connect-MsolService

Get-MsolServicePrincipal -AppPrincipalId “981f26a1-7f43-403b-a875-f8b09b8cd720” | Select-Object DisplayName, AccountEnabled

Get-MsolServicePrincipal -AppPrincipalId “1f5530b3-261a-47a9-b357-ded261e17918” | Select-Object DisplayName, AccountEnabled

Always On VPN and Azure MFA ESTS Token Error

If either or both enterprise applications are not enabled, enable them using the following PowerShell commands.

Set-MsolServicePrincipal -AppPrincipalId “981f26a1-7f43-403b-a875-f8b09b8cd720” -AccountEnabled $True

Set-MsolServicePrincipal -AppPrincipalId “1f5530b3-261a-47a9-b357-ded261e17918” -AccountEnabled $True

Once complete, restart the IAS service on the NPS server using the following PowerShell command.

Restart-Service IAS -PassThru

Additional Information

Windows 10 Always On VPN Network Policy Server (NPS) Load Balancing Strategies

Deploy Windows 10 Always On VPN with Microsoft Intune

Windows 10 Always On VPN Hands-On Training Classes Now Available

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