[Samba] Winbind and GPO access restrictions?

Patrick Goetz pgoetz at math.utexas.edu
Fri Oct 1 19:56:15 UTC 2021

On 10/1/21 13:52, Robert Marcano via samba wrote:
> On 10/1/21 2:21 PM, Patrick Goetz via samba wrote:
>> On 10/1/21 12:52, Robert Marcano via samba wrote:
>>> On 10/1/21 12:02 PM, Patrick Goetz via samba wrote:
>>>> While most of my campus Samba projects are still going to need to 
>>>> play nice with at least sssd id mapping, I do have one project 
>>>> which, based on discussions on this list, I was planning to 
>>>> configure strictly with winbind, since the AD DC is going to be 
>>>> Samba and it's the rare luxury where I get to control everything.
>>>> However, a couple of days ago I had an anxiety-inducing thought. 
>>>> This is a mixed windows/linux environment, and one of the features 
>>>> the end users would like and which I've already promised them is 
>>>> that the linux machines would have different access restrictions 
>>>> from the Windows desktops. The way I've been doing this with sssd is 
>>>> creating a GPO applied to the host (or set of hosts) which restricts 
>>>> access to a particular security group.
>>>> Reading through this page: 
>>>> https://wiki.samba.org/index.php/Group_Policy
>>>> it's not clear this would also be possible with winbind.  Would such 
>>>> a thing fall under the category of "smb.conf Policies"?  It doesn't 
>>>> seem like it, since smb.conf access restrictions are most aimed at 
>>>> share control.
>>> With winbind alone you will not be able to do that, you will need to 
>>> use classic Linux mechanism to control login (pam files editing for 
>>> example) and maybe automate the deployment on all machines by other 
>>> means (Ansible, Puppet, etc)
>>> Samba doesn't apply any GPO rules to Linux hosts. It is a sssd 
>>> feature to apply login restriction policies if enabled (and only a 
>>> few of them that make sense to Linux hosts)
>> Oh wow. So I guess winbind can not do everything sssd does, and I'm 
>> guessing that using idmap_sss doesn't help with this issue, either.
>> Looks like I'm back to using RFC 2307 mapping and doing what Rowland 
>> said not to do: just matching the UIDs/GIDs on the linux systems. But 
>> that's headache equivalent to using Ansible to copy around modified 
>> PAM configuration files and solves the other problem I have of at 
>> least one linux machine that needs file access being behind someone 
>> else's AD domain.
> In the case of PAM files, these files are very security sensitive and I 
> think people should embrace Red Hat auth select. Create customized 
> configuration, probably based on /usr/share/authselect/default/winbind/
> Install that authselect profile as an RPM and the only thing you need to 
> execute on you clients is to switch to your custom profile. At work I 
> will never trust a young sysadmin to modify these files directly, it is 
> too easy to make a security hole, only by a senior admin defining 
> templates.

And when using common-auth files, even easier to lock everyone out of 
the system so that you have to boot from USB or over IPMI to repair.

I didn't know about authselect and will need to look this up.

>> Now I'm mystified at how people are using newer versions of Samba in a 
>> mixed Windows/Linux environment. If your linux workstations (i.e. not 
>> fileservers) are bound to the domain, you most certainly want them to 
>> be using domain authentication restrictions and not some ad hoc thing 
>> you have to cobble together and deploy with CMS every time the 
>> directory changes. I guess this is the problem that RHEL idM solves by 
>> foresting with a Samba DC; no idea; I have no experience with this 
>> whatsoever.
>> Out of curiosity, is anyone out there using full blown sssd with a 
>> Samba version > 4.8?  Is that even a thing?
>>>> Thanks.

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