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 IKEv2 Policy Mismatch Error

Always On VPN IKEv2 Policy Mismatch ErrorThe Internet Key Exchange version 2 (IKEv2) VPN protocol is the protocol of choice for Windows 10 Always On VPN deployments where the highest levels of security and assurance are required. However, as I’ve written about in the past, often the default IKEv2 security settings are less than desirable. Before using IKEv2 VPN in a production environment the administrator will need to update these security settings accordingly.

Connection Failure

When configuring Windows Server Routing and Remote Access Service (RRAS) or a third-party VPN appliance to support IKEv2 using custom security policies, the administrator may encounter a scenario in which a connection cannot be established due to a policy mismatch error. When the connection attempt fails, an error will be recorded in the Windows Application event log from the RasClient source with Event ID 20227. The error message states the following:

“The user [username] dialed a connection named [connection name] which has failed. The error code returned on failure is 13868.”

Always On VPN IKEv2 Policy Mismatch Error

Error Code 13868

Error code 13868 translates to ERROR_IPSEC_IKE_POLICY_MATCH. Essentially this error indicates that the IKEv2 security policy on the client did not match the configuration on the server.

Server Configuration

To view the current IKEv2 IPsec policy configuration, open an elevated PowerShell command window and run the following command.

Get-VpnServerIPsecConfiguration

Always On VPN IKEv2 Policy Mismatch Error

Client Configuration

To ensure interoperability, the VPN client must be configured to use the same IKEv2 security policy as defined on the sever. To view a VPN client’s currently configured IKEv2 security policy, open an elevated PowerShell command window and run the following command.

Get-VpnConnection -Name [connection name] | Select-Object -ExpandProperty IPsecCustomPolicy

Always On VPN IKEv2 Policy Mismatch Error

Note: If this PowerShell command returns no output, the VPN connection is not using a custom IKEv2 IPsec security policy.

Updating Settings

Guidance for configuring IKEv2 security policies on Windows Server RRAS and Windows 10 can be found here.

Summary

IKEv2 policy mismatch errors can be resolved easily by ensuring both the VPN server and client are configured to use the same IPsec security policies. Use the PowerShell commands in the above referenced above to validate settings and make changes when necessary.

Additional Information

Windows 10 Always On VPN IKEv2 Security Configuration

Windows 10 Always On VPN IKEv2 Features and Limitations

Show-VpnConnectionIPsecConfiguration PowerShell script on Github

Set-IKEv2SecurityBaseline PowerShell script on Github

Always On VPN with Azure Gateway

Always On VPN with Azure GatewayRecently I wrote about VPN server deployment options for Windows 10 Always On VPN in Azure. In that post I indicated the native Azure VPN gateway could be used to support Always On VPN connections using Internet Key Exchange version 2 (IKEv2) and Secure Socket Tunneling Protocol (SSTP). In this post I’ll outline the requirements and configuration steps for implementing this solution.

Requirements

To support Always On VPN, point-to-site VPN connections must be enabled on the Azure VPN gateway. Not all Azure VPN gateways are alike, and point-to-site connections are not supported in all scenarios. For Always On VPN, the Azure VPN gateway must meet the following requirements.

VPN SKU

The Azure VPN gateway SKU must be VpnGw1, VpnGw2, VpnGw3, VpnGw1AZ, VpnGw2AZ, or VpnGw3AZ. The Basic SKU is not supported.

VPN Type

The VPN type must be route-based. Policy-based VPN gateways are not supported for point-to-site VPN connections.

Limitations

Using the Azure VPN gateway for Always On VPN may not be ideal in all scenarios. The following limitations should be considered thoroughly before choosing the Azure VPN gateway for Always On VPN.

Device Tunnel

RADIUS/EAP authentication for user tunnel connections is not supported if the Azure VPN gateway is configured to support device tunnel with machine certificate authentication.

Maximum Connections

A maximum of 250, 500, and 1000 concurrent IKEv2 connections are supported when using the VpnGw1/AZ, VpnGw2/AZ, and VpnGw3/AZ SKUs, respectively (x2 for active/active gateway deployments). In addition, a maximum of 128 concurrent SSTP connections are supported for all VPN gateway SKUs (x2 for active/active gateway deployments).

Always On VPN with Azure Gateway

Reference: https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-about-vpngateways#gwsku

RADIUS Requirements

To support Always On VPN connections, the Azure VPN gateway must be configured to authenticate to a RADIUS server. The RADIUS server must be reachable from the VPN gateway subnet. The RADIUS server can be hosted in Azure or on-premises. Before proceeding, ensure that any network routes, firewall rules, and site-to-site VPN tunnel configuration is in place to allow this communication.

RADIUS Configuration

Guidance for configuring Windows Server NPS for Always On VPN can be found here. The only difference when configuring NPS for use with Azure VPN gateway is the RADIUS client configuration.

Open the NPS management console (nps.msc) and follow the steps below to configure Windows Server NPS to support Always On VPN client connections from the Azure VPN gateway.

1. Expand RADIUS Clients and Servers.
2. Right-click RADIUS Clients and choose New.
3. Enter a descriptive name in the Friendly name field.
4. Enter the Azure VPN gateway subnet using CIDR notation in the Address (IP or DNS) field. The gateway subnet can be found by viewing the properties of the Azure VPN gateway in the Azure portal.
5. Enter the shared secret to be used for RADIUS communication in the Shared secret field.

Always On VPN with Azure Gateway

Azure VPN Gateway Configuration

To begin, provision a Virtual Network Gateway in Azure that meets the requirements outlined above. Guidance for implementing an Azure VPN gateway can be found here. Once complete, follow the steps below to enable support for Always On VPN client connections.

Enable Point-to-Site

Perform the following steps to enable point-to-site VPN connectivity.

1. In the navigation pane of the Azure VPN gateway settings click Point-to-site configuration.
2. Click Configure Now and specify an IPv4 address pool to be assigned to VPN clients. This IP address pool must be unique in the organization and must not overlap with any IP address ranges defined in the Azure virtual network.
3. From the Tunnel type drop-down list select IKEv2 and SSTP (SSL).
4. In the RADIUS authentication field enter the IPv4 address of the RADIUS server. At the time of this writing only a single IPv4 address is supported. If RADIUS redundancy is required, consider creating a load balanced NPS cluster.
5. In the Server secret field enter the RADIUS shared secret.
6. Click Save to save the configuration.

Always On VPN with Azure Gateway

VPN Client Configuration

Perform the following steps to configure a Windows 10 VPN client to connect to the Azure VPN gateway.

Download VPN Configuration

1. Click Point-to-site configuration.
2. Click Download VPN client.
3. Select EAPMSCHAv2 (yes, that’s correct even if EAP-TLS will be used!)
4. Click Download.
5. Open the downloaded zip file and extract the VpnSettings.XML file from the Generic folder.
6. Copy the FQDN in the VpnServer element in VpnSettings.XML. This is the FQDN that will be used in the template VPN connection and later in ProfileXML.

Always On VPN with Azure Gateway

Create a Test VPN Connection

On a Windows 10 device create a test VPN profile using the VPN server address copied previously. Configure EAP settings to match those configured on the NPS server and test connectivity.

Create an Always On VPN Connection

Once the VPN has been validated using the test profile created previously, the VPN server and EAP configuration from the test profile can be used to create the Always On VPN profile for publishing using Intune, SCCM, or PowerShell.

IKEv2 Security Configuration

The default IKEv2 security parameters used by the Azure VPN gateway are better than Windows Server, but the administrator will notice that a weak DH key (1024 bit) is used in phase 1 negotiation.

Always On VPN with Azure Gateway

Use the following PowerShell commands to update the default IKEv2 security parameters to recommended baseline defaults, including 2048-bit keys (DH group 14) and AES-128 for improved performance.

Connect-AzAccount
Select-AzSubscription -SubscriptionName [Azure Subscription Name]

$Gateway = [Gateway Name]
$ResourceGroup = [Resource Group Name]

$IPsecPolicy = New-AzVpnClientIpsecParameter -IpsecEncryption AES128 -IpsecIntegrity SHA256 -SALifeTime 28800 -SADataSize 102400000 -IkeEncryption AES128 -IkeIntegrity SHA256 -DhGroup DHGroup14 -PfsGroup PFS14

Set-AzVpnClientIpsecParameter -VirtualNetworkGatewayName $Gateway -ResourceGroupName $ResourceGroup -VpnClientIPsecParameter $IPsecPolicy

Note: Be sure to update the cryptography settings on the test VPN connection and in ProfileXML for Always On VPN connections to match the new VPN gateway settings. Failing to do so will result in an IPsec policy mismatch error.

Additional Information

Microsoft Azure VPN Gateway Overview

About Microsoft Azure Point-to-Site VPN

Windows 10 Always On VPN IKEv2 Security Configuration

 

 

 

Always On VPN Options for Azure Deployments

Always On VPN Options for Azure DeploymentsOrganizations everywhere are rapidly adopting Microsoft Azure public cloud infrastructure to extend or replace their existing datacenter. As traditional on-premises workloads are migrated to the cloud, customers are looking for options to host VPN services there as well.

Windows Server

Windows Server with the Routing and Remote Access Service (RRAS) installed is a popular choice for on-premises Always On VPN deployments. Intuitively it would make sense to deploy Windows Server and RRAS in Azure as well. However, at the time of this writing, RRAS is not a supported workload on Windows Server in Azure.

Always On VPN Options for Azure Deployments

Reference: https://support.microsoft.com/en-us/help/2721672/microsoft-server-software-support-for-microsoft-azure-virtual-machines/

Although explicitly unsupported, it is possible to deploy Windows Server and RRAS in Azure for Always On VPN. In my experience it works well and can be an option for organizations willing to forgo formal support by Microsoft.

Azure Gateway

Options for supporting Always On VPN connections using native Azure VPN infrastructure depend on the type of VPN gateway chosen.

VPN Gateway

The Azure VPN Gateway can be configured to support client-based (point-to-site) VPN. With some additional configuration it can be used to support Windows 10 Always On VPN deployments. Azure VPN gateway supports both IKEv2 and SSTP VPN protocols for client connections. The Azure VPN gateway has some limitations though. Consider the following:

  • A route-based VPN gateway is required
  • A maximum of 1000 concurrent IKEv2 connections are supported when using the VpnGw3 or VpnGw3AZ SKUs (2000 supported in active/active mode)
  • A maximum of 128 concurrent SSTP connections are supported on all gateway SKUs (256 supported in active/active mode)

Virtual WAN

Azure Virtual WAN is the future of remote connectivity for Azure. It includes support for client-based VPN (currently in public preview at the time of this writing), but only supports IKEv2 and OpenVPN VPN protocols for client connections. SSTP is not supported at all. Further, OpenVPN is not supported for Windows 10 Always On VPN, leaving IKEv2 as the only option, which poses some potential operational challenges. Virtual WAN offer much better scalability though, supporting up to 10,000 concurrent client-based VPN connections.

Virtual Appliance

The most supportable option for hosting VPN services in Azure for Windows 10 Always On VPN is to deploy a third-party Network Virtual Appliance (NVA). They are available from a variety of vendors including Cisco, Check Point, Palo Alto Networks, Fortinet, and many others. To support Windows 10 Always On VPN, the NVA vendor must either support IKEv2 for client-based VPN connections or have a Universal Windows Platform (UWP) VPN plug-in client available from the Microsoft store. Click here to learn more about Always On VPN and third-party VPN devices.

Note: Be careful when choosing an NVA as some vendors support IKEv2 only for site-to-site VPN, but not client-based VPN!

Hybrid Deployments

For organizations with hybrid cloud deployments (infrastructure hosted on-premises and in Azure), there are several options for choosing the best location to deploy VPN services. In general, it is recommended that client VPN connections be established nearest the resources accessed by remote clients. However, having VPN servers hosted both on-premises and in Azure is fully supported. In this scenario Azure Traffic Manager can be configured to intelligently route VPN connections for remote clients.

NetMotion Mobility

The NetMotion Mobility purpose-built enterprise VPN is a popular replacement for Microsoft DirectAccess. It is also an excellent alternative for enterprise organizations considering a migration to Always On VPN. It is a software-based solution that can be deployed on Windows Server and is fully supported running in Microsoft Azure. It offers many advanced features and capabilities not included in other remote access solutions.

Summary

Administrators have many options for deploying VPN servers in Azure to support Windows 10 Always On VPN. Windows Server and RRAS is the simplest and most cost-effective option, but it is not formally supported by Microsoft. Azure VPN gateway is an interesting alternative but lacks enough capacity for larger deployments. Azure Virtual WAN is another option but has limited protocol support. Deploying an NVA is a good choice, and NetMotion Mobility is an excellent alternative to both DirectAccess and Always On VPN that is software-based and fully supported in Azure.

Additional Information

Windows 10 Always On VPN with Azure Gateway

Windows 10 Always On VPN and Third-Party VPN Devices

Windows 10 Always On VPN and Windows Server Routing and Remote Access Service (RRAS)

Windows 10 Always On VPN IKEv2 Features and Limitations

Windows 10 Always On VPN Multisite with Azure Traffic Manager

Comparing DirectAccess and NetMotion Mobility

Deploying NetMotion Mobility in Microsoft Azure

 

 

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 SSTP Load Balancing with F5 BIG-IP

Always On VPN SSTP Load Balancing with F5 BIG-IP The Windows Server Routing and Remote Access Service (RRAS) includes support for the Secure Sockets Tunneling Protocol (SSTP), which is a Microsoft proprietary VPN protocol that uses SSL/TLS for security and privacy of VPN connections. The advantage of using SSTP for Always On VPN is that it is firewall friendly and ensures consistent remote connectivity even behind highly restrictive firewalls.

Load Balancing SSTP

In a recent post, I described some of the use cases and benefits of SSTP load balancing as well as the offloading of TLS for SSTP VPN connections. Using a load balancer for SSTP VPN connections increases scalability, and offloading TLS for SSTP reduces resource utilization and improves performance for VPN connections. There are positive security benefits too.

Configuration

Enabling load balancing for SSTP on the F5 BIG-IP platform is fundamentally similar to load balancing HTTPS web servers. However, there are a few subtle but important differences.

Default Monitor

The default HTTP and HTTPS monitors on the F5 will not accurately reflect the health of the SSTP service running on the RRAS server. In addition, using a simple TCP port monitor could yield unexpected results. To ensure accurate service status monitoring, a new custom monitor must be created to validate the health of the SSTP service.

Custom SSTP Monitor

Open the F5 BIG-IP management console and follow the steps below to create and assign a new custom monitor for SSTP.

Create Monitor

1. In the navigation tree highlight Local Traffic.
2. Click Monitors.
3. Click Create.

Always On VPN SSTP Load Balancing with F5 BIG-IP

4. Enter a descriptive name in the Name field and from the Type drop-down list choose HTTP if TLS offload is enabled, or HTTPS if it is not.
5. In the Send String field enter HEAD /sra_{BA195980-CD49-458b-9E23-C84EE0ADCD75}/ HTTP/1.1\r\nHost:r\nConnection: Close\r\n\r\n.
6. In the Receive String field enter HTTP/1.1 401.
7. Click Finished.

Always On VPN SSTP Load Balancing with F5 BIG-IP

Assign Monitor

1. Below Local Traffic click Pools.
2. Click on the SSTP VPN server pool.
3. In the Health Monitors section select the SSTP VPN health monitor from the Available list and make it Active.
4. Click Update.

Always On VPN SSTP Load Balancing with F5 BIG-IP

CLI Configuration

If you prefer to configure the SSTP VPN monitor using the F5’s Command Line Interface (CLI), you can download the monitor configuration from my GitHub here.

TLS Offload

It is generally recommended that TLS offload not be enabled for SSTP VPN. However, if TLS offload is desired, it is configured in much the same way as a common HTTPS web server. Specific guidance for enabling TLS offload on the F5 BIG-IP can be found here. Details for configuring RRAS and SSTP to support TLS offload can be found here.

Certificates

When enabling TLS offload for SSTP VPN connections it is recommended that the public SSL certificate be installed on the RRAS server, even though TLS processing will be handled on the F5 and HTTP will be used between the F5 and the RRAS server. If installing the public SSL certificate on the RRAS server is not an option, additional configuration will be required. Specifically, TLS offload for SSTP must be configured using the Enable-SSTPOffload PowerShell script, which can be found here.

Once the script has been downloaded, open an elevated PowerShell command window and enter the following command.

Enable-SSTPOffload -CertificateHash [SHA256 Certificate Hash of Public SSL Certificate] -Restart

Example:

Enable-SSTPOffload -CertificateHash “C3AB8FF13720E8AD9047DD39466B3C8974E592C2FA383D4A3960714CAEF0C4F2” -Restart

Re-Encryption

When offloading TLS for SSTP VPN connections, all traffic between the F5 and the RRAS server will be sent in the clear using HTTP. In some instances, TLS offload is required only for traffic inspection, not performance gain. In this scenario the F5 will be configured to terminate and then re-encrypt connections to the RRAS server. When terminating TLS on the F5 and re-encrypting connections to the RRAS server is required, the same certificate must be used on both the F5 and the RRAS server. Using different certificates on the RRAS server and the load balancer is not supported.

Additional Information

Windows 10 Always On VPN SSTP Load Balancing and SSL Offload

Windows 10 Always On VPN SSL Certificate Requirements for SSTP

Windows 10 Always On VPN ECDSA SSL Certificate Request for SSTP

Windows 10 Always On VPN SSTP Connects then Disconnects

Windows 10 Always On VPN Load Balancing Deployment Guide for Kemp Load Balancers

 

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

 

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

Denying Access to Always On VPN Users or Computers

Denying Access to Always On VPN Users or ComputersOnce Windows 10 Always On VPN has been deployed in production, it may be necessary at some point for administrators to deny access to individual users or computers. Commonly this occurs when an employee is terminated or leaves the company, or if a device is lost, stolen, or otherwise compromised. Typically, this means that user accounts and computer accounts in Active Directory are disabled, and any issued certificates are revoked. However, additional steps may be required to disconnect current VPN sessions or prevent future remote connections.

Certificate Revocation

When certificates are used for authentication, for example when a device tunnel is deployed, or a user tunnel is configured to use Extensible Authentication Protocol (EAP) with user certificate authentication, immediately revoking issued user and device certificates and publishing a new Certificate Revocation List (CRL) is recommended. However, this will not instantly prevent VPN access because revocation information is cached on the VPN and NPS servers, as well as any online responders. The process of flushing certificate revocation caches is challenging and time consuming as well.

Blocking Users

To immediately prevent users from accessing the VPN, a security group must be created in Active Directory that contains users that will be denied access. In addition, a Network Policy must be created on the Network Policy Server (NPS) that denies access to users belong to this security group.

NPS Configuration

Once the security group has been created, open the NPS management console (nps.msc) and perform the following steps.

  1. Expand Policies.
  2. Right-click Network Policies and choose New.
  3. Enter a descriptive name for the policy in the Policy name field.
  4. Select Remote Access Server (VPN-Dial up) from the Type of network access server drop-down list.
  5. Click Next.
  6. Click Add.
    1. Select User Groups.
    2. Click Add.
    3. Click Add Groups.
    4. Select the security group create for denied users.
    5. Click Ok twice.
  7. Click Next.
  8. Select Access denied.
  9. Click Next four times and click Finish.

Denying Access to Always On VPN Users or Computers

Denying Access to Always On VPN Users or Computers

Once complete, move the deny access policy so that it is before the policy that allows VPN access.

Denying Access to Always On VPN Users or Computers

Device Tunnel Considerations

Since device tunnel connections don’t use the NPS for authentication, blocking devices from establishing Always On VPN connections requires a different technique. Once again, revoking the computer certificate and publishing a new CRL is recommended, but isn’t immediately effective. To address this challenge, it is recommended that the computer certificate issued to the client be retrieved from the issuing CA and placed in the local computer’s Untrusted Certificates store on each VPN server, as shown here.

Note: The certificate must be imported on each VPN server in the organization.

Terminating Connections

Once the guidance above is put in to place, any user or device that is denied access will be unable to connect to the VPN. However, if a user or device is currently connected when these changes are implemented, additional steps must be taken to proactively terminate their existing session. When using Windows Server Routing and Remote Access Service (RRAS) as the VPN server, uUser sessions can be proactively terminated using RRAS management console or PowerShell.

GUI

To terminate an established Always On VPN connection, open the RRAS management console (rrasmgmt.msc), highlight Remote Access Clients, then right-click the client connection and choose Disconnect. Repeat the process for any additional connections established by the user or device.

Denying Access to Always On VPN Users or Computers

PowerShell

Alternatively, Always On VPN connections can also be terminated programmatically using PowerShell. To identify currently connected users on a VPN server, open an elevated PowerShell command window and run the following command.

Get-RemoteAccessConnectionStatistics | Format-Table -AutoSize

Next, to disconnect a user tunnel, identify the User Principal Name (UPN) of the user to disconnect and include it in the following PowerShell command.

Disconnect-VpnUser -UserName “user@corp.example.net”

To disconnect a device tunnel, identify the Fully-Qualified Domain Name (FQDN) of the device to disconnect and include it in the following PowerShell command.

Disconnect-VpnUser -UserName “client1.corp.example.net”

Additional Information

Windows 10 Always On VPN Hands-On Training

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