All posts tagged workaround

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.

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

When Always On VPN Isn’t

Microsoft Always On VPN is a beautiful thing. VPN profiles are assigned to the user (and, optionally, their device). When users power up their device and log on, they are automatically connected to the corporate network and can access all the applications and data they need on-premises. Until recently, though, end users could disconnect the VPN. Why they would do this is beyond comprehension, but sadly, it happens all too often. When it does, it presents a problem for Always On VPN administrators because they must now rely on the user to re-enable this feature. And until they do, they often suffer productivity loss, and their devices may fall out of compliance.

Connect Automatically

When an Always On VPN profile is provisioned to a user (or a device), the VPN profile has the option to ‘Connect automatically’ enabled by default. Unfortunately, this setting is cleared if a user terminates the VPN.

This setting will remain cleared until the user rechecks the box to enable it. Until then, the VPN will no longer connect automatically.

Workarounds

Instead of relying on the grace of the end user to restore Always On functionality, administrators have a few options to correct this problem programmatically.

Intune Remediation

Administrators can use Intune Remediations to deploy a set of detection and remediation scripts I’ve published to update this setting. Now, administrators can enforce ‘Always On’ VPN connections with the assurance that if the user turns off this feature, it will be quickly re-enabled.

Detect-AutoTriggerDisabledProfile.ps1

Remediate-AutoTriggerDisabledProfile.ps1

SCCM

You can find a standalone version of this script here if you use System Center Configuration Manager (SCCM) or another systems management solution to manage your endpoints.

Clear-AutoTriggerDisabledProfile.ps1

AovpnTools

In addition, you will find the Clear-AutoTriggerDisabledProfile function is included in my AOVPNTools PowerShell module, which can be installed from the PowerShell gallery.

Install-Module -Name AOVPNTools -Force

Disable Disconnect Button

To avoid this pain in the future, Always On VPN administrators can prevent users from disconnecting the VPN using the UI by leveraging the DisableDisconnectButton option in ProfileXML. This setting is supported for both user and device tunnels on Windows 11 and later devices.

Additional Information

AOVPNTools PowerShell Module

AOVPNTools PowerShell Module on GitHub

Always On VPN and Intune Remediations

6 Comments

by Richard M. Hicks on January 15, 2024 • Permalink

Posted by Richard M. Hicks on January 15, 2024

https://directaccess.richardhicks.com/2024/01/15/when-always-on-vpn-isnt/

Always On VPN November 2023 Security Updates

Microsoft has released its security updates for November 2023. For Always On VPN administrators, it’s a light month, with just a single CVE affecting Always On VPN infrastructure.

PEAP

CVE-2023-36028 addresses a remote code execution (RCE) vulnerability in the Microsoft Protected Extensible Authentication Protocol (PEAP). An attacker could exploit this vulnerability by sending a specially crafted PEAP packet to a Windows Network Policy Server (NPS). This attack does not require authentication or user interaction.

Affected Systems

This PEAP vulnerability affects only NPS servers configured to support PEAP authentication explicitly. PEAP authentication is a best practice configuration for Always On VPN deployments and is widely deployed. NPS servers deployed to support other services, such as Wi-Fi or router and switch access that are configured to allow PEAP authentication, are also affected.

Exposure

NPS servers are not (or should not be!) exposed directly to the public Internet. This limits the attack surface to adversaries already on the internal network.

Mitigation

Microsoft suggests disabling PEAP authentication support on NPS servers until the update is applied. However, this would break the majority of Always On VPN deployments today. Since disabling PEAP isn’t a viable option, administrators can reduce their attack surface by updating the NPS firewall rules to restrict access only to authorized VPN servers or other network devices until their systems are fully updated.

Additional Information

November 2023 Security Updates

CVE-2023-36028 PEAP Remote Code Execution Vulnerability

4 Comments

by Richard M. Hicks on November 14, 2023 • Permalink

Posted by Richard M. Hicks on November 14, 2023

https://directaccess.richardhicks.com/2023/11/14/always-on-vpn-november-2023-security-updates/

Richard M. Hicks Consulting, Inc.

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All posts tagged workaround

Always On VPN Device Tunnel Issues with April 2024 Security Update