[Samba] Samba 3.0.0 -- ACLs are unusable due to UID/SID mapping weirdness :(

John H Terpstra jht at samba.org
Tue Oct 21 02:43:36 GMT 2003

On Mon, 20 Oct 2003, Anton Solovyev wrote:

Having read your posting, I believe I need your help to fix our
documentation. Are you willing to help me to do that?

> Hi,
> I am sure somebody asks this question about once a week. Since I have
> not found an answer I assume the worst -- it just does not work.

Please do not assume that because something does not work the way you have
tried it that this means that Samba is broken. That is a bit like failing
a driving test and then claiming that the test vehicle must have been

Have you read the Samba-HOWTO-Collection.pdf? Did you understand it all?
Did you red the chapter on Group Mapping? Did it help you any? What do we
need to add to the documentation to help someone else to understand the
issues and to help them to find a solution.

I need your feedback to help improve our documentation. Perhaps it is all
wrong. It could be you know!

> So, here goes my problem. I am testing Samba 3.0.0. I have got UNIX and
> Windows domain users matching each other one-to-one.

Here we go! What do you mean by: "users matching each other one-to-one"?
Please explain this fully. I do not want to jump to conclusions, but my
reading is that you have added users to the Samba server while it is a
domain member server. Is my interpretation correct?

> The server is running with "security = domain". Everything works fine
> and all Windows users connecting to Samba get mapped into their
> respective UNIX user ids. Everything is nice, simple and consistent.

So you have a Windows NT4 Domain, or Active Directory? I can't really tell
from your description. It does matter - it would certainly help me to help
you. I have to tell people time and again that my crystal ball is worn out
and my guessing is lousy! :)

How did you "join the domain"? What precise steps did you take? Help me to
reproduce your problem!

What information can you glean from the samba log files to confirm that
"everything is nice, simple and consistent"?

> Now I want to enable ACLs and fortunately the host OS supports them
> fine. Here the trouble starts. It looks like ACLs refuse to work in the
> absense of winbindd.

Precisely, which user identities (or group identities) do you want to
include in the ACLs? Accounts that are in /etc/passwd on the Samba server,
or Domain Accounts?

If you have a johndoe account in the Samba /etc/passwd, and a johndoe
account on the Domain as well, then you need to realise that they are two
totally different users. One is machine local and tied to the SID of your
Samba server, the other is Domain Global, and is tied to the Domain SID.
Do you recognize that?

If you want to be able to use Domain accounts then you must have winbindd

> So I start winbindd and... get random mapping of NT domain accounts into
> UNIX ids in the range of "idmap uid/gid".
> So, for example, if I create a file from the windows side it gets
> ownership of:
> solovam/uid=1001
> on the UNIX side. Windows says the owner is:
> \SAMBA-SERVER\solovam
> Which is already strange, I expect \DOMAIN\solovam like on all NT boxes.

No. As I mentioned, a Samba server /etc/passwd account called 'solocam' is
an entirely different user account from user 'solovam' on a Domain

> If I try to add and ACL entry for myself to this file, I get a POSIX acl
> entry for:
> ???/uid=40000

Thanks to NSS (entry in /etc/nsswitch.conf) this is a domain account.

> which is what winbindd assigned for my SID. At this point Windows says
> this was an ACL entry for user:
> \DOMAIN\solovam

Right. As expected.

> So, this is basically the problem. When I connect to Samba server I
> connect as \DOMAIN\solovam and use domain password. The files I create
> belong to my UNIX account "solovam". At the same time if I check
> ownership, I see that I act as \SAMBA-SERVER\solovam! If I try to change
> ACLs, I am back to being \DOMAIN\solovam, but my SID is now mapped by
> winbindd to something randomly selected.

Nope. I already explained that.

> Well, there are a lot of funny implications at this point (like change
> UNIX permissions to 000 and try to add "full control" ACL for the domain
> user, which resets UNIX permissions again!), but the bottom line is that
> Samba in this area is completely broken and horribly inconsistent.

Alternatively, could it possibly be that your understanding of how this
ought to work is "completely uninformed", or "completely unrealistic", or
maybe "just a little bit off".

> I hope I am missing something really obvious, but after a day of looking
> at documentation I doubt it is so.

What documentation did you look at? What documentation (specific pages
etc.) did you look at that allowed you to come to the conclusions you have
arrived at.

Maybe, just maybe, your conclusions are perfectly valid and "the
documentation is completely wrong". Which ever it is, will you help me to
fix it?


- John T.
John H Terpstra
Email: jht at samba.org

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