Windows RDP: ‘An authentication error has occurred’

KB ID 0001433

Problem

When attempting to RDP to a remote machine;

RDP Error The Function Requested is not supported

 

An authentication error has occurred.
The function requested is not supported

Remote computer: {name}
This could be due to CredSSP encryption oracle remediation.

Or you may just see;

 

The Function Request Is Not supported

An authentication error has occurred.
The function requested is not supported

Remote computer: {name}

Solution

This is happening after you have a applied a windows security update it was this security update. It also tells you how to change your GPOs accordingly.

Enable Oracle Remediation Missing

If your business is in Chaos – set it to ‘Vulnerable‘ to get things working, get EVERYTHING patched, then change it to ‘Mitigated‘ or ‘Force Updated‘. (WARNING: any change requires a reboot!).

CredSSP Matrix

 ‘Encryption Oracle Remediation’ Policy Is Missing?

Copy these two files from a freshly updated machine;

  • C:\Windows\PolicyDefinitions\CredSsp.admx (Dtd Did Feb 2018)
  • C:\Windows\PolicyDefinitions\en-US\CredSsp.adml (Dtd Feb 2018 – Your local folder may be different i.e. en-GB)

On a DC, navigate to;

  • C:\Windows\SYSVOL\sysvol\<your domain>\Policies\PolicyDefinitions

Rename the current CredSsp.admx to CredSsp.admx.old

Copy the new CredSsp.admx to this folder.

On the same DC navigate to;

  • C:\Windows\SYSVOL\sysvol\<your domain>\Policies\PolicyDefinitions\en-US (or your local language)

Rename the current CredSsp.adml to CredSsp.adml.old

Copy the new CredSsp.adml file to this folder.

Try your group policy again.

If Using a Central Policy Definition Store

You will need to copy the files to the central PolicyDefinitions folder in your Sysvol directory, see the following link;

Setup up a Central ‘PolicyDefinitions’ Store (for ADMX files)

 

Footnote

Don’t Simply Uninstall Windows updates KB41037272. and or KB4103718 – just because something works does not mean that’s what you should do!

Related Articles, References, Credits, or External Links

Windows – Remote Desktop Error ‘An authentication error has occurred. The Local Security Authority cannot be contacted’

Author: PeteLong

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