samba - Jan 2025 - Different behavior when client uses "sec=none" and when provides bad user (mapped to guest)

On Sat, 18 Jan 2025 11:04:21 +0100
Carlos Alberto Balseiro Mayi via samba <samba at lists.samba.org> wrote:
> mount -t cifs //192.168.1.4/descargas/MiSTer /media/fat/cifs -o 
> username=badusertest
When you run the above command (by the way, mount.cifs has nothing to
do with Samba), the mount command sends the user 'badusertest' and as
that user does not exist, Samba maps it the 'guest' user and allows
access to the 'descargas' share because you have 'map to guest = Bad
User' in global and 'guest ok = Yes' in the share.
 
> 
> mount -t cifs //192.168.1.4/descargas/MiSTer /media/fat/cifs -o
> sec=none
> 
When you send 'sec=none', no username is sent, now I do not know what
is doing it (it could be the mount program, Samba or something Truenas
has added), but something is using the username 'nobody' and that name
does exist and so it isn't getting mapped to the guest user (even
though it is the 'guest' user) and is denied access.

I do not know how long this has been going on (I personally have never
used 'sec=none') and, if it is a bug, I have no idea what needs fixing,
Samba, cifs-utils or Truenas.

Rowland

Thanks a lot for your analysis. I just wanted to add that I think we are 
not using at all? The client is an embedded Linux/FPGA machine and it 
doesn't have mount.cifs . I think it is using 
https://wiki.samba.org/index.php/LinuxCIFSKernel . It comes default with 
kernel 5.15 but I tried with a 6.10 and same problem happens.

Best Regards,

Carlos A. Balseiro

El 2025-01-18 11:32, Rowland Penny via samba escribi?:
> On Sat, 18 Jan 2025 11:04:21 +0100
> Carlos Alberto Balseiro Mayi via samba <samba at lists.samba.org>
wrote:
> 
>> mount -t cifs //192.168.1.4/descargas/MiSTer /media/fat/cifs -o
>> username=badusertest
> 
> When you run the above command (by the way, mount.cifs has nothing to
> do with Samba), the mount command sends the user 'badusertest' and
as
> that user does not exist, Samba maps it the 'guest' user and allows
> access to the 'descargas' share because you have 'map to guest
= Bad
> User' in global and 'guest ok = Yes' in the share.
> 
>> mount -t cifs //192.168.1.4/descargas/MiSTer /media/fat/cifs -o
>> sec=none
> 
> When you send 'sec=none', no username is sent, now I do not know
what
> is doing it (it could be the mount program, Samba or something Truenas
> has added), but something is using the username 'nobody' and that
name
> does exist and so it isn't getting mapped to the guest user (even
> though it is the 'guest' user) and is denied access.
> 
> I do not know how long this has been going on (I personally have never
> used 'sec=none') and, if it is a bug, I have no idea what needs
fixing,
> Samba, cifs-utils or Truenas.
> 
> Rowland