[PLUG] Mount cifs share from fstab.

Tomas tomas.kuchta.lists at gmail.com
Tue Dec 5 05:57:18 UTC 2017


Yes, thank you ... that is how it is suppose to work with
AD/keberos/SMB/CIFS.

Unfortunately, the original poster does not appear to have AD or any
kind of SSO. So, I believe that he is concerned that plain text
password in a file is not the most secure option.

Despite the password from the file not being transmitted in plain text,
there are still issues with this --> The SMB share would be mounted by
the mounting user, regardless who is logged in on the linux box and
using the share. So the ownership and access rights would naturally
follow the mountee.

This is not too much of an issue with windows, especially if SMB and
local passwords are identical. However typical Linux setup does not use
SMB for local authentication. Additionally, in SMB nothing really can
be mounted without some sort of user authentication first. So SMB sort
of prevents securely mounting shares at boot being ready for user to
login.

There has been plenty of similar posts related to SMB/CIFS mounts and
resulting access issues. I think, that people do not realize that a
local user on one machine is not equal to a local user on another
machine. SSO/AD provides the trust between the hosts and common
authentication method between the machines and servers.

The easiest way to reconcile this would be probably to synchronize the
users and their UID's across the machines and the file server and
switch to plain NFS on Linux. Of course this is only as secure as the
network because plain NFS trusts the machines about the users.

I hope it helps explaining little the
ownership/permission/authentication issues.

Tomas

On Tue, 2017-12-05 at 01:32 +0000, Smith, Cathy wrote:
> I work in a multi-user environment where authentication is performed
> by Kerberos.  So all user accounts in the Active Directory domain,
> use their AD password to login to the Linux servers.   The Linux
> server is configured as a samba server.   We run Red Hat here.   I
> just have a basic samba server configuration running on the Linux
> server.  I don't have to have the account's password specified as
> long as the account is in the AD domain.  We only use the .sambpass
> file for non-AD accounts.  Those account must have a local password
> entry on the Linux server.
> 
> Cathy
> -- 
> Cathy L. Smith
> IT Engineer
> 
> Pacific Northwest National Laboratory
> Operated by Battelle for the 
> U.S. Department of Energy
> 
> Phone: 509.375.2687
> Fax:       509.375.4399
> Email: cathy.smith at pnnl.gov
> 
> 
> 
> -----Original Message-----
> From: plug-bounces at pdxlinux.org [mailto:plug-bounces at pdxlinux.org] On
> Behalf Of Tomas Kuchta
> Sent: Monday, December 04, 2017 4:35 PM
> To: Portland Linux/Unix Group <plug at pdxlinux.org>
> Subject: Re: [PLUG] Mount cifs share from fstab.
> 
> When you put SMB password into root RO file, it is not secure
> locally, but it is not transmitted over the network in the plain text
> as far as I know.
> 
> In my experience, SMB/CIFS is quie painful to use in multi user,
> multi machine world without domain compatible single sign of.
> 
> To be fair, same goes for NFS with Kerberos, if you cannot live
> without server side authentication.
> 
> Off topic:
> In my opinion - single sign on should be basic stuff done by any
> ..nix household chiefdom setup for both Linux and Windows. Once
> working, it makes huge difference in usability and security. And it
> currently keeps M$ away from local network resource scans.
> 
> -T
> 
> On Dec 4, 2017 3:47 PM, "David" <dafr+plug at dafr.us> wrote:
> 
> > 
> > On 12/04/2017 03:36 PM, michael wrote:
> > 
> > > 
> > > On 2017-12-04 17:00, David wrote:
> > > 
> > > > 
> > > > On 12/04/2017 02:33 PM, michael wrote:
> > > > 
> > > > > 
> > > > > I have it working.  I don't want the password for the owner
> > > > > of the 
> > > > > share in plain text in a file though.  Creating
> > > > > /home/pi/.smbpasswd 
> > > > > with the contents:
> > > > > username=Test
> > > > > password=password
> > > > > domain=somedomain
> > > > > and chmod 600 isn't good enough.
> > > > > 
> > > > > The password should be salted in this file even if it is
> > > > > password!
> > > > > 
> > > > > Is there a simple way to use an smbpasswd file properly
> > > > > salted 
> > > > > without implementing a full samba server?
> > > > > 
> > > > 
> > > > The proper tool that I know of is "smbpasswd" as an
> > > > executable, 
> > > > which is part of the samba-common-bin package on my system
> > > > (Debian).
> > > > 
> > > > It may have dependencies which includes a full smb server
> > > > (which I 
> > > > run), so this may not be helpful information.
> > > > 
> > > > dafr
> > > > 
> > > 
> > 
> > > 
> > > I am most concerned about the password having to be in plaintext
> > > when 
> > > transmitted over the network.  Even if there is a way without a
> > > full 
> > > samba server deployment to have the password sent in encrypted
> > > form 
> > > over the network, that would be great.  The server is probably
> > > the 
> > > latest incarnation of Windows server.  I don't like the idea of 
> > > having to have a Linux user for every Windows user either.
> > > 
> > 
> > 
> > 
> > Sure, I get that, and agree with the concerns. I was looking at
> > the 
> > smbpasswd man page initially and this is why I think you want to
> > use 
> > this
> > utility:
> > 
> >       "On a UNIX machine the encrypted SMB
> >        passwords are usually stored in the smbpasswd(5) file."
> > 
> > Now, the problem with the utility is that unless you do something 
> > fancy, you may have to be on the localhost where the share is
> > exported 
> > to set / reset the password as a user. This may not be feasible in 
> > your situation unless there is a web interface that you can front 
> > smbpasswd with to allow users to change passwords.
> > 
> > When mounting a share in a Windows VM on my Linux host, I have to
> > auth 
> > with a pop-up window of user / pass to access the shared
> > directory. 
> > I'm not sure if (and don't believe that) you have to have a Linux 
> > account for the Windows user. They are different password files,
> > but 
> > my experience is also limited to a full samba server, so your
> > needs 
> > may be more an issue than mine.
> > 
> > dafr
> > _______________________________________________
> > PLUG mailing list
> > PLUG at pdxlinux.org
> > http://lists.pdxlinux.org/mailman/listinfo/plug
> > 
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