[Samba] 4.13.2 guest access denied with "Bad SMB2 signature"

[Jeremy Allison]

On Thu, Dec 03, 2020 at 10:39:37AM -0700, Steve Leung via samba wrote:
>
>Hi all,
>
>Guest access to file shares in Samba 4.13.2 seems to be broken.  The 
>logs report a "Bad SMB2 signature" error, and the client sees an 
>"access denied" error.  This looks like a regression IMO, but I'd like 
>to check that I'm not doing something wrong.
>
>Clients tested:
>- AndSMB app on Android
>- Windows 10 laptop
>
>I've trimmed my smb.conf down to the essentials for a standalone 
>server, based on:

Correct me if I'm wrong, but doesn't guest access prohibit
signing and encryption ?

https://docs.microsoft.com/en-us/troubleshoot/windows-server/networking/guest-access-in-smb2-is-disabled-by-default

Note:

"Guest logons do not support standard security features such as signing and encryption.
Therefore, guest logons are vulnerable to man-in-the-middle attacks that can expose
sensitive data on the network. Windows disables insecure (nonsecure) guest logons
by default. Microsoft recommends that you do not enable insecure guest logons."