Enabling SMB guest access via registry breaks the Workstation service beyond repair

Question

In effort to enable insecure guest access for SMB via powershell script on Windows Server 2022, I've followed steps recommended in this article : https://learn.microsoft.com/en-US/troubleshoot/windows-server/networking/guest-access-in-smb2-is-disabled-by-default

There are two ways of setting insecure guest access for SMB :

• via Group Policy (manual setup, this seems to work fine)
• via Windows Registry entries (problematic one!)

As I'm doing automated setup, I've used powershell to execute registry entry config as explained in aforementioned web page :

To set the value without using Group Policy, set the following DWORD registry value to 1 (insecure guest auth enabled) or 0 (insecure guest auth disabled):

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

*AllowInsecureGuestAuth
*
However, after executing this config and after OS restarts, Workstation service is not able to start any more. Exception being thrown is : Windows could not start the Workstation service on Local Computer. Error 2: The System cannot find the file specified.

There is no way, at least I was not able to find one, to undo this. How can one fix this and make this setting automated? Re-installing Windows OS and applying the setting manually is only way to fix this.

Answer 1

I've used powershell to execute registry entry config as explained in aforementioned web page :

Can you share the command that you ran?

Did you specify a REG_DWORD type?

(From Win10 VM.)

C:\>reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters
    EnablePlainTextPassword    REG_DWORD    0x0
    EnableSecuritySignature    REG_DWORD    0x1
    RequireSecuritySignature    REG_DWORD    0x0
    ServiceDll    REG_EXPAND_SZ    %SystemRoot%\System32\wkssvc.dll
    ServiceDllUnloadOnStop    REG_DWORD    0x1
    AllowInsecureGuestAuth    REG_DWORD    0x1

I ran this.

reg.exe add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters /v AllowInsecureGuestAuth /t REG_DWORD /d 1 

Answer 2

I've used this two commands :

    New-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" -force -ErrorAction SilentlyContinue
    Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" -Name AllowInsecureGuestAuth -Value "1" -Type DWORD -force

First one checks the Parameters Item/Path, second one adds a DWORD AllowInsecureGuestAuth key with value set to 1.

Btw. when I execute :
**reg query HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters
**
I'm getting only this :

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters
    AllowInsecureGuestAuth    REG_DWORD    0x1

... I don't see any other parameters.

Furthermore, if you do a config using Local Group Policy Editor :

*1. Open the Local Group Policy Editor (gpedit.msc) on your Windows device.
2. In the console tree, select Computer Configuration > Administrative Templates > Network > Lanman Workstation.
3. For the setting, right-click Enable insecure guest logons and select Edit.
4.Select Enabled > OK.

For monitoring and inventory purposes, this group policy sets the following DWORD registry value to 1 (insecure guest auth enabled) or 0 (insecure guest auth disabled):*
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\LanmanWorkstation\
AllowInsecureGuestAuth

... but, there are no visible entries added to that specific registry path when you do this. Nevertheless, it works.

Answer 3

Hi,

Modifying the registry can cause serious problems if not done correctly. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs.

How to back up and restore the registry in Windows - Microsoft Support

PC resetting and startup repair are worth having a try.

Reference: “Recovery options in Windows” for step-by-step formation:

Recovery options in Windows - Microsoft Support