What do I do if the error message "An authentication error has occurred. The function requested is not supported" appears when I connect to a simple application server?

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important

This topic contains important information on necessary precautions. We recommend that you read this topic carefully before proceeding.

This topic describes the error message "An authentication error has occurred. The function requested is not supported" that appears when you connect to a simple application server. This topic also describes the causes of and solutions to the error.

Problem description

When you use Remote Desktop on your on-premises device to a Windows simple application server, the error message "An authentication error has occurred. The function requested is not supported" appears.

Causes

In May 2018, Microsoft released an update for the Credential Security Support Provider protocol (CredSSP) and changed the authentication method. By default, if the update is not installed on your on-premises device or your simple application server, the on-premises device and the simple application server may not be able to communicate.

The connection error occurs in the following scenarios:

Scenario 1: No CredSSP update is installed on the on-premises device. A CredSSP update is installed on the simple application server, with Encryption Oracle Remediation set to Force Updated Clients.
For more information about how to fix the connection error, see the Solution 1: Allow the simple application server to use Remote Desktop Connection section of this topic.
Scenario 2: A CredSSP update is installed on the on-premises device, with Encryption Oracle Remediation set to Force Updated Clients. No CredSSP update is installed on the simple application server.
For more information about how to fix the connection error, see the Solution 2: Install a CredSSP update or Solution 3: Modify the Windows registry section of this topic.
Scenario 3: A CredSSP update is installed on the on-premises device, with Encryption Oracle Remediation set to Mitigated. No CredSSP update is installed on the simple application server.
For more information about how to fix the connection error, see the Solution 2: Install a CredSSP update or Solution 3: Modify the Windows registry section of this topic.

Note

The preceding description "no CredSSP update is installed" means no CredSSP update version released since May 2018 is installed.
The preceding description "a CredSSP update is installed" means a CredSSP update version released since May 2018 is installed.
For more information about Encryption Oracle Remediation policies, see CredSSP updates for CVE-2018-0886.

Solutions

You can fix this issue by allowing the simple application server to use Remote Desktop Connection, installing a CredSSP update, or modifying the Windows registry.

Solution 1: Allow the simple application server to use Remote Desktop Connection

The operations slightly vary based on Windows versions. The following sections describe the operations on simple application servers of Windows Server 2008 R2, Windows 2012 R2, and Windows 2016 Datacenter.

Windows Server 2008 R2

Windows Server 2012 R2

Windows Server 2016 Datacenter

Connect to the simple application server by using the Virtual Network Console (VNC).
For more information, see the "Use VNC to connect to the server in the Simple Application Server console" section of the Connect to a Windows server topic.
Click Start on your on-premises device, right-click Computer, and then select Properties.
In the Control Panel Home section, click Remote settings.
In the System Properties dialog box, on the Remote tab, select Allow connections from computers running any version of Remote Desktop (Less secure), and then click OK.

Connect to the simple application server by using the VNC.
For more information, see the "Use VNC to connect to the server in the Simple Application Server console" section of the Connect to a Windows server topic.
Click the icon, right-click This PC, and then select Properties.
In the Control Panel Home section, click Remote settings.
On the Remote tab, clear Allow connections only from computers running Remote Desktop with Network Level Authentication (more secure), and then click OK.

Connect to the simple application server by using the VNC.
For more information, see the "Use VNC to connect to the server in the Simple Application Server console" section of the Connect to a Windows server topic.
Click the icon, and then click Windows System.
Right-click This PC and choose More > Properties.
In the Control Panel Home section, click Remote settings.
On the Remote tab, clear Allow connections only from computers running Remote Desktop with Network Level Authentication (more secure), and then click OK.

Solution 2: Install a CredSSP update

In the following example, an on-premises device that runs Windows Server 2016 operating system is used. The operations for other Windows systems are similar with these operations.

Connect to the simple application server by using the VNC.
For more information, see the "Use VNC to connect to the server in the Simple Application Server console" section of the Connect to a Windows server topic.
Click the icon, and then click Settings.
On the Windows Settings page, click Update and Security.
On the Update Status page, click Check for Updates and wait for the update to be downloaded and installed.
Note
To manually install the security update package for CredSSP, visit the Microsoft official website and download the security update package.
On the simple application server, choose > > Restart to restart the simple application server and update the configurations of the server.

Solution 3: Modify the Windows registry

In the following example, an on-premises device that runs Windows Server 2016 operating system is used. The operations for other Windows systems are similar with these operations. After a CredSSP update is installed on your on-premises device or your simple application server, use one of the following methods to modify the Windows registry.

Warning

If the registry is improperly modified, serious issues may occur on the Windows operating system. You need to modify the registry at your own risk. Before you modify the registry, we recommend that you create a snapshot to back up your data to avoid possible data loss. For more information, see the "Create a snapshot" section of the Manage snapshots topic.

(Recommended) Use a script to modify the registry

Manually modify the registry

Connect to the simple application server by using the VNC.
For more information, see the "Use VNC to connect to the server in the Simple Application Server console" section of the Connect to a Windows server topic.
Open the Command Prompt window.
1. Right-click the icon, and then select Run.
2. In the Run dialog box, enter cmd.
3. Click OK.
  Open the Command Prompt window.
Run the following command to enter the PowerShell mode:
```
powershell
```

Run the following command to run the Windows PowerShell script as an administrator:

New-Item -Path HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System -Name CredSSP -Force
New-Item -Path HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP -Name Parameters -Force
Get-Item -Path HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters | New-ItemProperty -Name AllowEncryptionOracle -Value 2 -PropertyType DWORD -Force

On the simple application server, choose > > Restart to restart the simple application server and update the configurations of the server.
Note
If you have used this method to modify the registry and then installed security updates on the on-premises device and the simple application sever, we recommend that you set Values of AllowEncryptionOracle to 0 or 1 to enhance security. For more information about Values of AllowEncryptionOracle, see CredSSP updates for CVE-2018-0886.

Connect to the simple application server by using the VNC.
For more information, see the "Use VNC to connect to the server in the Simple Application Server console" section of the Connect to a Windows server topic.
Open Registry Editor.
1. Right-click the icon, and then select Run.
2. In the Run dialog box, enter regedit.
3. Click OK.
  Go to Registry Editor.
On the Registry Editor page, in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters path, set Values of AllowEncryptionOracle to 2.
Note
For more information about Values of AllowEncryptionOracle, see CredSSP updates for CVE-2018-0886.
If the CredSSP key or Parameters key does not exist, create a new corresponding registry key, and then create a new AllowEncryptionOracle registry key of the REG_DWORD type under the corresponding registry key. For example, if none of the CredSSP and Parameters keys exists, perform the following operations:
1. Create a new CredSSP key in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System path.
  1. Right-click the blank area of the registry keys and select New (N) > Key (K).
  2. Enter the CredSSP and press the Enter key.
2. Create a new Parameters key in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP path.
3. Create a new AllowEncryptionOracle key in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters path.
4. Modify the Values of the AllowEncryptionOracle registry key.
  1. Right-click AllowEncryptionOracle, and then click Modify.
  2. In the dialog box, set Value Data to 2 and click OK.
On the simple application server, choose > > Restart to restart the simple application server and update the configurations of the server.