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Always On VPN CSP Updates

Always On VPN DNS Registration Update Available

Administrators can deploy Always On VPN client configuration settings in several ways. The simplest method is to use the native Microsoft Intune UI and the VPN device configuration profile template. Optionally, administrators can create an XML file that can be deployed with Intune using the Custom template. In addition, the XML file can be deployed using PowerShell, either interactively or with System Center Configuration Manager (SCCM). Administrators can also deploy the XML file using PowerShell via Active Directory group policy startup script or another software provisioning platform.

Custom XML

While using the native Intune VPN device configuration template to deploy and manage Always On VPN client configuration settings is easy and convenient, it lacks support for many crucial configuration settings. Deploying Always On VPN client settings using the Custom template is helpful to overcome these limitations as it enables additional configuration settings not exposed in the Intune VPN template.

VPNv2CSP

The VPNv2 Configuration Service Provider (CSP) is the interface used by Intune to deploy Always On VPN client configuration settings to the endpoint. The WMI-to-CSP bridge enables settings deployment using PowerShell. In either scenario, administrators must create an XML file that includes the settings used for the Always On VPN profile. A reference for all supported settings in the VPNv2 CSP can be found here.

New Settings

Microsoft recently introduced some new settings in the VPNv2 CSP. Beginning with Windows 11 22H2, administrators can disable the disconnect button and prevent access to the advanced settings menu for device and user tunnels in the Windows UI by adding the following entries in the XML configuration file.

<DisableDisconnectButton>true</DisableDisconnectButton>

<DisableAdvancedOptionsEditButton>true
</DisableAdvancedOptionsEditButton>

Additional Updates

Microsoft also added options to define encryption settings, disable IKEv2 fragmentation support, update IPv4 and IPv6 interface metrics, adjust IKEv2 network outage time, and disable the use of RAS credentials in XML for device and user tunnels. These new options eliminate the need to use Intune Proactive Remediation to adjust these VPN client configuration settings post-deployment.

Unfortunately, these settings are not supported in any current release of Windows 10 or 11 today. However, they are available in the latest Windows Insider build (development channel) if you want to test them. I’ve provided example settings below. These settings will be supported in a public release of Windows in the future.

<DataEncryption>Max</DataEncryption>
<DisableIKEv2Fragmentation>true</DisableIKEv2Fragmentation>
<IPv4InterfaceMetric>3</IPv4InterfaceMetric>
<IPv6InterfaceMetric>3</IPv6InterfaceMetric>
<NetworkOutageTime>0</NetworkOutageTime>
<UseRasCredentials>false</UseRasCredentials>

Note: At the time of this writing, the VPNv2 CSP indicates these settings apply to Windows 11 21H2 and later. That is incorrect. Microsoft is aware of the issue and will hopefully correct it soon.

Intune Support

At some point, Microsoft may add these features to the Intune VPN device configuration template. However, XML with the Custom template is the only way to enable these new settings today.

Additional Information

Always On VPN VPNv2 CSP Reference

Deploying Always On VPN with Intune using Custom ProfileXML

Always On VPN and Intune Proactive Remediation

Microsoft Intune Learning Resources for Always On VPN Administrators

Example Always On VPN User Tunnel ProfileXML

Example Always On VPN Device Tunnel ProfileXML

8 Comments
by Richard M. Hicks on March 6, 2023  •  Permalink
Posted in administration, Always On VPN, AOVPN, Deployment, Device Management, device tunnel, Endpoint Manager, Enterprise, enterprise mobility, Group Policy, IKEv2, Infrastructure, InTune, MDM, MEM, MEMCM, Microsoft, Microsoft Endpoint Manager, Microsoft Intune, Mobile Device Management, Mobility, OMA-DM, Operational Support, PowerShell, ProfileXML, Remote Access, SCCM, Security, System Center Configuration Manager, systems management, Update, VPN, Windows 11
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Posted by Richard M. Hicks on March 6, 2023

https://directaccess.richardhicks.com/2023/03/06/always-on-vpn-csp-updates/

Always On VPN NPS and PEAP Vulnerabilities

The February 2023 security updates for Windows Server address multiple vulnerabilities that affect Microsoft Always On VPN administrators. This latest update addresses multiple critical and important vulnerabilities in the Network Policy Server (NPS), commonly used to perform RADIUS authentication for Always On VPN servers. Specifically, there are several Remote Code Execution (RCE) and Denial of Service (DoS) vulnerabilities with Protected Extensible Authentication Protocol (PEAP). PEAP with user authentication certificates is the authentication protocol of choice for Always On VPN user tunnel authentication.

Vulnerabilities

The following is a list of vulnerabilities in PEAP addressed in the February 2023 security update.

  • CVE-2023-21689 – Microsoft PEAP Remote Code Execution Vulnerability (critical)
  • CVE-2023-21690 – Microsoft PEAP Remote Code Execution Vulnerability (critical)
  • CVE-2023-21691 – Microsoft PEAP Information Disclosure vulnerability (important)
  • CVE-2023-21692 – Microsoft PEAP Remote Code Execution Vulnerability (critical)
  • CVE-2023-21695 – Microsoft PEAP Remote Code Execution Vulnerability (important)
  • CVE-2023-21701 – Microsoft PEAP Denial of Service Vulnerability (important)

Mitigation

Unauthenticated attackers can exploit the RCE vulnerabilities in PEAP on Microsoft Windows NPS servers. However, NPS servers should not be exposed directly to the Internet and would require an attacker to have access to the internal network already. However, administrators are advised to apply this update to their NPS servers as soon as possible. In addition, organizations that deploy the NPS role on enterprise domain controllers should update immediately.

Additional Information

February 2023 Update for Windows Server 2022 (KB5022842)

February 2023 Update for Windows Server 2019 (KB022840)

February 2023 Update for Windows Server 2016 (KB5022838)

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by Richard M. Hicks on February 16, 2023  •  Permalink
Posted in Active Directory, administration, Always On VPN, AOVPN, authentication, certificates, Cryptography, Device Management, EAP, Encryption, Enterprise, enterprise mobility, extensible authentication protocol, Hotfix, Infrastructure, Microsoft, Mobility, network policy server, NPS, Operational Support, PEAP, Protected EAP, Remote Access, Security, Update, user tunnel, VPN, Vulnerability, Windows Server 2016, Windows Server 2019, Windows Server 2022
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Posted by Richard M. Hicks on February 16, 2023

https://directaccess.richardhicks.com/2023/02/16/always-on-vpn-nps-and-peap-vulnerabilities/

Always On VPN Authentication Failed Reason Code 16

Strong authentication is essential for remote access to on-premises resources over the public Internet. Using the Protected Extensible Authentication Protocol (PEAP) in combination with user certificates issued by the organization’s internal certification authority (CA) provides high assurance for remote user authentication. It includes the added benefit of making the Always On VPN connection completely seamless for the user, as their certificate is presented to the authentication server transparently during VPN connection establishment. Using PEAP with user certificates is the recommended authentication method for Always On VPN deployments.

Reason Code 16

When configuring Always On VPN to use PEAP with client authentication certificates, administrators may encounter a scenario in which a user has a valid certificate. Yet, their authentication request is rejected by the Network Policy Server (NPS) server when attempting to connect remotely. Looking at the Security event log on the NPS server, administrators will find a corresponding event ID 6273 in the Network Policy Server task category from the Microsoft Windows security auditing event source. In the Authentication Details section, you’ll find that the reason code for the failed request is Reason Code 16, with the following reason specified.

“Authentication failed due to a user credentials mismatch. Either the user name provided does not map to an existing user account or the password was incorrect”.

Password Incorrect?

The reason code indicates the user may have entered an incorrect password. However, the user does not enter their password when using PEAP with client authentication certificates, so there’s no chance the password was entered incorrectly.

TPM

I have increasingly encountered this scenario with many customers deploying Always On VPN over the last year or so. This error is often caused by a known issue with older TPM models. Specifically, those with a TPM specification sub-version of 1.16 and earlier. You can view these TPM details by opening the Windows Settings app and entering ‘security processor’ in the search field.

Workaround

These older TPM models seem to have an issue with RSA-PSS signature algorithms, as described here. If possible, administrators should upgrade devices with older TPM versions to ensure the highest level of security and assurance for their remote users. However, in cases where that is not feasible, administrators can remove RSA-PSS signature algorithms from the registry, which forces the use of a different signature algorithm and seems to restore functionality.

To do this, open the registry editor (regedit.exe) and navigate to the following registry key.

HKLM\CurrentControlSet\Control\Cryptography\
Configuration\Local\SSL\00010003\

Double-click the Functions entry and remove the following algorithms from the Value data section.

  • RSAE-PSS/SHA256
  • RSAE-PSS/SHA384
  • RSAE-PSS/SHA512

Once complete, reboot the device and test authentication once again.

Intune Proactive Remediation

Administrators using Intune Proactive Remediation will find detection and remediation scripts to make these changes published on GitHub.

Detect-RsaePss.ps1

Remediate-RsaePss.ps1

Additional Information

Windows TPM 2.0 Client Authentication in TLS 1.2 with RSA PSS

Always On VPN NPS Auditing and Logging

Always On VPN NPS RADIUS Configuration Missing

Always On VPN NPS Load Balancing

11 Comments
by Richard M. Hicks on February 13, 2023  •  Permalink
Posted in Active Directory, administration, Always On VPN, AOVPN, authentication, certificates, Cryptography, EAP, Encryption, Enterprise, enterprise mobility, Microsoft, Mobility, network policy server, NPS, Operational Support, PEAP, PKI, public key infrastructure, Remote Access, Security, TPM, troubleshooting, Trusted Platform Module, VPN, Windows 10, Windows 11
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Posted by Richard M. Hicks on February 13, 2023

https://directaccess.richardhicks.com/2023/02/13/always-on-vpn-authentication-failed-reason-code-16/

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