samba - Oct 2017 - Do Unix extensions still work with SMB3?

Hi all,

Quick question - does Samba server still support Unix extensions when
connecting over SMB3?

My Linux client recently got upgraded to a CIFS module version that uses
SMB3 by default, and since then I lost the ability to create symlinks
on my CIFS shares.  Running "mount" shows the share mounted with the
"nounix" option.  If I follow the advice in dmesg and add the mount
option "vers=1.0" to return to SMB1, then Unix extensions are enabled
and symlinks work fine.

The server is a Seagate NAS appliance running Samba 4.6.2, with "unix
extensions = yes" in the [global] section of smb.conf.

Do I need to change the way Unix extensions are activated for SMB3?

Many thanks,
Adam.

On Sat, 14 Oct 2017 19:08:48 +1000
Adam Nielsen via samba <samba at lists.samba.org> wrote:
> Hi all,
> 
> Quick question - does Samba server still support Unix extensions when
> connecting over SMB3?
Quick answer - No
> 
> My Linux client recently got upgraded to a CIFS module version that
> uses SMB3 by default, and since then I lost the ability to create
> symlinks on my CIFS shares.  Running "mount" shows the share
mounted
> with the "nounix" option.  If I follow the advice in dmesg and
add
> the mount option "vers=1.0" to return to SMB1, then Unix
extensions
> are enabled and symlinks work fine.
> 
> The server is a Seagate NAS appliance running Samba 4.6.2, with "unix
> extensions = yes" in the [global] section of smb.conf.
> 
> Do I need to change the way Unix extensions are activated for SMB3?
> 
You cannot - Yet, it is being worked on.

Rowland

On Sat, Oct 14, 2017 at 07:08:48PM +1000, Adam Nielsen via samba
wrote:
> Hi all,
> 
> Quick question - does Samba server still support Unix extensions when
> connecting over SMB3?
> 
> My Linux client recently got upgraded to a CIFS module version that uses
> SMB3 by default, and since then I lost the ability to create symlinks
> on my CIFS shares.  Running "mount" shows the share mounted with
the
> "nounix" option.  If I follow the advice in dmesg and add the
mount
> option "vers=1.0" to return to SMB1, then Unix extensions are
enabled
> and symlinks work fine.
FYI, when we do finalize the UNIX extensions, at least for
the Samba implementation, we're not going to allow clients
to create "real" symlinks on the server - only SMB-followable
symlinks. Allowing clients to create real server symlinks as
in SMB1 UNIX extensions has been a long-term security disaster.

Cheers,

	Jeremy.

> > Quick question - does Samba server still support Unix extensions when
> > connecting over SMB3?
> 
> FYI, when we do finalize the UNIX extensions, at least for
> the Samba implementation, we're not going to allow clients
> to create "real" symlinks on the server - only SMB-followable
> symlinks. Allowing clients to create real server symlinks as
> in SMB1 UNIX extensions has been a long-term security disaster.
Thanks for the info.  Will there be a utility to convert existing
server-side symlinks into SMB-style symlinks, so that upgrading the
server won't break existing symlinks?  Or at least a server-side command
to create SMB symlinks so you can script the change with `find -type l`?

Thanks also Rowland for the quick answer.

Cheers,
Adam.