[Samba] idmap & migration to rfc2307

Michael Adam obnox at samba.org
Sun Nov 8 20:01:57 UTC 2015

On 2015-11-08 at 20:34 +0100, buhorojo wrote:
> On 07/11/15 19:57, Michael Adam wrote:
> >On 2015-11-07 at 17:47 +0000, Jonathan Hunter wrote:
> >>On 7 November 2015 at 17:01, Michael Adam <obnox at samba.org> wrote:
> >>>Also, for all I know, the DC always has local unix user and group
> >>>IDs, and does NOT use the rfc2307 attributes for this. (Unless
> >>>this has changed recently, but I can't imagine how.) So there is
> >>>nothing wrong with samba not using the rfc ids on the DC -- this is
> >>>how it works by design.
> >>Thanks Michael. I will see if I can use winbind locally instead of
> >>sssd later this evening, now that I have fully switched to rfc2307
> >>rather than algorithmic mappings.
> >>
> >>One question on this, though - how is file ownership managed on the DC
> >>from the samba side? I know DCs aren't "supposed" to be used as file
> >>servers in the samba view of things (which is another story
> >>altogether), but I can't understand why sometimes the ID mapping comes
> >>from the rfc2307 attributes and then later on not.
> >I don't understand that yet.
> >As explained in my previous mail, what can happen is that
> >a user first (before given a rfc unixID) gets its uid from the
> >idmap.ldb, but as soon as there is a unixid in the rfc
> >attributes in his ldap object, that should always be used.
> >
> >This is a per-user thing.
> >
> >It is not surpsising that an externally configured sssd
> >(configured to use rfc in a ad, and hence behaving more like
> >a domain member) possibly gives different results, and also
> >consistently uses the rfc attrs, since that one does not
> >have the fallback to idmap.ldb that samba has.
> sssd's uses its own implementation of winbind

I repeat: sssd does not implement winbind.
It implements some parts of the winbind protocol.
It is not a drop-in replacement for winbind(d).
And the ad-dc forcefully uses winbindd anyways,
so sssd is not at all an option.

> and _always_ retrieves the same id from AD. Repeat, _always_.
> Currently it and nslcd are the only way to obtain full rfc2307
> and consistent ids on DCs. Neither winbind nor
> winbindd can do so.

Sure. winbindd can do it. use the idmap_ad module :-)
The only problem exists in the ad/dc setup due to
the fallback (that I proposed to remove).

> >The mapping should indeed be consistent for a user on the DC,
> >so it should not intermittently switch between idmap.ldb and
> >the rfc attributes. That would be a bug that we need to
> >understand.
> >
> >One step as written in a previous mail would be to change
> >the dc code to _never_ fall back to idmap.ldb when configured
> >with "idmap_ldb:use rfc2307 = yes".
> It has to fall back as uid is undefined for builtin objects.

As someone else has already said: builtin are different.
These are machine-local anyways.
We were talking about the main user DB, subordinate
to the domain SID. And for _that_, it should not fall back.
Fallback is a bug here as elaborated ealier...

Cheers - Michael
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