[Samba] Recommended configuration for AD forest with child domains

Gémes Géza geza at kzsdabas.hu
Sat Sep 17 00:12:50 MDT 2011

2011-09-16 21:21 keltezéssel, Jim Stalewski írta:
> Greetings,
> I have had Samba/Winbind/Kerberos single-sign-on authentication working
> for a few years now, for a single domain, and it works great.  It pulls
> the RFC2307 populated attributes just like you'd expect, and people get
> the IDs mapped according to their attributes in AD.
> This works for version 3.2.7 and 3.4.3.  I had to give the domain's
> Domain Users group a gid in the range of the idmap config range in order
> for it to work in 3.4.3 because for some unexplained reason, you have to
> be a member of domain users in order for winbind to even look at your
> rfc2307 attributes, but that's another complaint/bug/"feature."
> I have tried it with 3.5x and 3.6.0, and can't get it to work no matter
> how I tweak smb.conf.  
> I am in a multi-domain AD forest, in a child domain.  I need to be able
> to give the same single sign-on access to people that live in the parent
> domain as well as the peer domain, and since AD has the whole transitive
> trust thing, there should be no trust issues.
> I can list all of the users in each domain and all of the groups in each
> domain, by issuing wbinfo -u or wbinfo -g, so Winbind, through whatever
> mechanism it uses, can see all of them.  
> However, to look at the RFC2307 attributes to determine whether or not
> they should be enumerated with getent group or getent passwd, it appears
> the idmap_ad process uses LDAP lookup on the authentication server to
> find whether the rfc2307 attributes have been populated.  I don't know
> if this is the problem or not, but some observations:
> LDAP access to AD, when done on the LDAP port 389, will automatically
> set the search base to the domain.  This precludes any lookup of people
> not in that domain.
> The lookup that is done is done against whatever AD server answers the
> knock on the door, whether it has a replica of the Global Catalog or
> not, so if by luck of the draw your domain's Infrastructure master is
> used as the authentication server, there's no GC to look against, even
> if Winbind didn't default to port 389 and looked at port 3268 (the GC
> port) to do its idmap lookup.  
> So, given those observations, exactly how would someone configure
> Samba/Winbind to do SSO authentication using AD RFC2307 in a
> multi-domain parent/child domain AD forest such that you could have
> people authenticating from the Samba server's domain as well as the
> other trusted domains in the forest?
> I have made sure that the GC included attributes have the necessary
> RFC2307 attributes included.  They're not by default so you have to make
> sure they do get populated into the GC (at least according to the
> idmap_adex man page)
> Speaking of which, I tried using idmap_adex with 3.5x and 3.6.0, but
> although the users/groups enumerate just fine with wbinfo, I am not
> getting any idmapping through NSS.  I have seen comments that
> idmap_adex' features were being rolled into idmap_ad (no need to have
> more than one idmap for a given infrastructure) but no word as to when
> that will happen for Samba 3, if at all, or what us poor
> multi-domain-forest suckers like me are supposed to do in the meantime.
> Thanks,
> Jim.
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You could try to switch to idmap_adex which was created explicitly to
answer the multidomain forest problem. Please read
http://www.samba.org/samba/docs/man/manpages-3/idmap_adex.8.html before
trying to deploy as it needs schema modifications for AD: "Note that you
must add the uidNumber, gidNumber, and uid attributes to the partial
attribute set of the forest global catalog servers. This can be done
using the Active Directory Schema Management MMC plugin (schmmgmt.dll).".

Good Luck!


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