[Samba] Domain Administrator and shares problems

Tue Oct 9 08:23:49 UTC 2018

On Mon, 8 Oct 2018 22:52:05 +0200
Peter Milesson via samba <samba at lists.samba.org> wrote:

> 
> 
> On 08.10.2018 21:02, Rowland Penny via samba wrote:
> > On Mon, 8 Oct 2018 18:53:45 +0200
> > Peter Milesson via samba <samba at lists.samba.org> wrote:
> >
> >> Hi folks,
> >> Problem
> >> =======
> >> Setting up and managing the shares on the Samba member server
> >> differs significantly from the Samba Wiki documentation. It seems
> >> that the domain Administrator account, and the Domain Admins group
> >> haven't got any elevated privileges whatsoever. On the contrary,
> >> it seems the privileges are even lower than for the Anyone group.
> >> This resulted in a very quirky and non standard way of share setup
> >> and management.
> >>
> >> The different steps I have gone through are described below.
> >>
> >> I follow the step-by-step description in the Wiki
> >> (https://wiki.samba.org/index.php/Setting_up_a_Share_Using_Windows_ACLs)
> >>
> >> - The folder for the share is created
> >> - The Linux ownership and permissions of the folder are set
> >> (root:"Domain Admins" and 0770)
> >> - The share is defined in smb.conf on the member server
> >> - Restarting the daemons (nmbd winbindd smbd)
> > Try running this on the Unix domain member:
> > net rpc rights list privileges SeDiskOperatorPrivilege -S $(hostname
> > -f) -k -P
> >
> > It should give you something like this:
> >
> > SeDiskOperatorPrivilege:
> >    BUILTIN\Administrators
> >
> > If you then run this on a DC:
> >
> > samba-tool group listmembers Administrators
> >
> > You should get this:
> >
> > Domain Admins
> > Enterprise Admins
> > Administrator
> >
> > This shows that both 'Domain Admins' & 'Administrator' both have the
> > required privileges.
> >
> >> - Logging in as domain Administrator on a Windows PC
> >> - Opening up Computer Management in Windows
> >> - Connecting to the samba member server
> >> - Clicking on Shared folders, a long error message about DCOM is
> >> displayed, but the shares on the member server is displayed anyway.
> > You can ignore the message, as you have found out, it is
> > meaningless.
> >
> >> - Selecting the share, right click and selecting Properties, and
> >> Share Permissions tab
> >> - Setting Domain Users having Read & Change permissions, and Domain
> >> Admins Full Control, removing Everyone from the list
> > Don't remove anything, in fact, ignore the share permissions tab.
> >
> >> - Switching to the Security tab, which is blank, which effectively
> > Now here is a problem, it shouldn't be blank, is a firewall running
> > on the Unix domain member holding the 'Profiles' share ?
> >
> >> means that anything that deals with security is not available to
> >> the accounts Domain Users and Domain Admins. Which in turn implies
> >> that none of those groups can do anything with the share (i.e.
> >> lacking administrative permissions).
> > It should work, check that smbd, nmbd & winbind are running and not
> > being blocked by anything.
> >
> >> - It could stop here. But...
> >>
> >> - Going back to the Share Permissions tab and adding Everyone with
> >> full share permissions
> >> - Once again going to the Security tab, which now displays all the
> >> default permissions. One of the users in the list is for example
> >> Unix root
> >> - Now it is possible to add different security objects and set
> >> permissions. But adding the domain Administrator to the security
> >> objects list is almost a guarantee to get into trouble, no matter
> >> what permissions the Administrator is given.
> >>
> >> I succeeded to setup working shares on the Samba member server this
> >> way, but it feels wrong, and it's definitely not the standard way
> >> to do things.
> >>
> >> Besides, on the Samba member server also, the domain Administrator
> >> account behaves like a normal user account, not like the root
> > I think you may be operating under a misapprehension, Windows users
> > are just Windows users and Unix users are just Unix users. You can
> > map Windows users to Unix users or make them Unix users by giving
> > them a uidNumber attribute or using the winbind 'rid' backend, but
> > making a Windows user a Unix user, just gives it the same rights as
> > any other Unix user.
> > When you map 'Administrator' to the Unix user 'root', Administrator
> > becomes root, with all the rights that root has, this means
> > Administrator can do anything on Unix.
> > The Windows user Administrator shouldn't really log into a Unix
> > machine, just as the Unix user root shouldn't be able to log into a
> > Windows machine.
> >
> >> account, like this on the folder grulf:
> >>
> >> (using root)  drwxrwx---   2 root domain admins 4096 Oct  8 18:19
> >> grulf
> >>
> >> (using adminstrator) drwxrwx---   2 administrator domain admins
> >> 4096 Oct  8 18:19 grulf
> > Yes, it does show it isn't working for you, but not for the reason
> > you think ;-)
> >
> > [root at cen1804 ~]# ls -la /data/samba
> > total 4
> > drwxr-xr-x  4 root root        41 Oct  8 18:37 .
> > drwxr-xr-x  3 root root        19 Oct  8 18:37 ..
> > drwxr-xr-x  2 root root         6 Oct  8 18:37 common_docs
> > drwxrwxr-x+ 2 root unix admins  6 Oct  8 18:37 profiles
> >
> > If you look carefully at the line that ends in 'profiles', you will
> > see a '+' sign, this means that ACL's are set on the share.
> >
> > [root at cen1804 ~]# getfacl /data/samba/profiles/
> > getfacl: Removing leading '/' from absolute path names
> > # file: data/samba/profiles/
> > # owner: root
> > # group: unix\040admins
> > user::rwx
> > user:root:rwx
> > user:12122:rwx
> > group::r-x
> > group:root:r-x
> > group:unix\040admins:rwx
> > mask::rwx
> > other::r-x
> > default:user::rwx
> > default:user:root:rwx
> > default:user:12122:rwx
> > default:group::r-x
> > default:group:root:r-x
> > default:group:unix\040admins:rwx
> > default:mask::rwx
> > default:other::r-x
> >
> > and if I return to my Win7 VM running ADUC and add myself to the
> > security tab:
> >
> > [root at cen1804 ~]# getfacl /data/samba/profiles/
> > getfacl: Removing leading '/' from absolute path names
> > # file: data/samba/profiles/
> > # owner: root
> > # group: unix\040admins
> > user::rwx
> > user:root:rwx
> > user:rowland:r-x
> > user:12122:rwx
> > group::rwx
> > group:root:r-x
> > group:rowland:r-x
> > group:unix\040admins:rwx
> > mask::rwx
> > other::r-x
> > default:user::rwx
> > default:user:root:rwx
> > default:user:rowland:r-x
> > default:user:12122:rwx
> > default:group::r-x
> > default:group:rowland:r-x
> > default:group:unix\040admins:rwx
> > default:mask::rwx
> > default:other::r-x
> >
> > So, you can see that it does work.
> >
> > What filesystem are you using ?
> >
> >> smb.conf AD DC
> >> =============
> >> [global]
> >>           netbios name = KONADC
> >>           realm = SAMDOM.LOCAL
> >>           server role = active directory domain controller
> >>           workgroup = SAMDOM
> >>           idmap_ldb:use rfc2307 = yes
> >>           username map = /etc/samba/user.map
> > You do not use a 'user.map' on a DC, it uses idmap.ldb instead
> >
> > Rowland
> >
> >
> Hi Rowland,
> 
> Plenty of information here...
> 
> Essentially...
> 
> - Running net rpc rights list ... etc, and  samba-tool group
> listmember Administrator returns exactly what you have got.
> - The share permissons tab has got one single entry the first time
> it's opened, and that's Everyone, with Full control (see below, about
> ACLs)
> - If I leave Everyone in the share permissions tab with Full control, 
> the Security tab displays the default security objects, and is
> editable and sort of working. Starting to mix in Administrator here,
> and things go wrong...
> 
> On purpose, getting things straight before stepping up security, I
> have turned off firewalld and selinux on both the AD DC, and the
> member server. I have made extra sure that no sssd (neither client,
> nor daemon), or other irrelevant daemons are installed. Everything is
> just plain as plain as possible. I have really stepped down security
> as much as possible here, just to get things working. I'm always
> using ext4 file systems. The other file systems on offer are too
> experimental to my taste ;-)
> 
> I am not trying to get any account defined through AD to login into a 
> Linux machine. The member server I have set up is intended to work
> with Windows ACLs only on all shares. No shell logins with AD users.
> No Posix ACLs. The only shell accounts allowed will be local root,
> and a local user account with sudo permissions. Likewise, no
> connections from the member server to Windows machines. I regard the
> Samba member server as any Windows file server in this respect. The
> only purpose is to supply shares for different purposes. Nothing else.
> 
> IMHO, if I manage the shares through AD, except for the small work of 
> defining a share in smb.conf, I want the rest of the work to be more
> or less agnostic when it comes to management. In this respect, I
> really don't care if the server supplying shares is running Linux,
> Windows, or BananaOS. The domain administrator has got very extensive
> privileges in a Windows environment. Mapping this to root on a Samba
> member server is just logical on a domain member server running Samba
> in this context. That I prefer Linux over Windows is also irrelevant
> here. Those points could be debated till the next Big Bang...

I only have Windows in VMs and only start them when needed, so the
debate would probably be very short, Linux is undoubtedly better than
Windows ;-)

> 
> When you show the ACLs above, it's ringing a bell. When running mkdir 
> under CentOS 7.5, the folder is created with plain Linux permissions, 
> without using any extended attributes, or ACLs at all. When having
> been manipulated via Windows Computer Management, ACLs are also
> applied. Maybe this is the problem, that CentOS does not apply ACLs
> by default when creating a folder?

I sort of thought the computer name (cen1804) would have shown that
Centos does apply ACLs ;-)

I installed Centos 7 in a VM, accepted the defaults and then installed
Samba. One thing I found out, xfs seems to be the default filesystem,
but ext4 works in roughly the same way.

> 
> Anyway, it sort of works, I managed to make the migration from a NT4
> PDC (from 2011) to AD without loss of user profiles. In the current
> state, the behavior is ugly, but it works, differently from setting
> up a share on a Windows server, however. But still, it seems that the
> Samba member server still does not honor the privileges of the domain
> Administrator, and regards it like "ordinary" user "Donald with very
> tiny permissions", belonging to the group "Domain Users".

I think your problem is that you expect Administrator to have the same
rights as root on a Unix machine, it doesn't, it is just another use.
If you use the winbind 'rid' backend, then getent will show the
Administrator user, but the 'ad' backend doesn't (unless you give
Administrator a uidNumber and this is definitely not recommended).
This means that the best thing you can do is, ignore Administrator on
Unix and map it in the user.map to root.

> 
> Next step, I'm going to try it out on a freshly setup domain, an AD
> DC, a member server, and a Windows domain PC, without any historical 
> ballast. There may have been lots of garbage left, that's giving 
> trouble. I don't know, until it's tested.

That might be a good idea, as I said, I used a new install and it
worked for me.

Rowland