[Samba] Recommended configuration for AD forest with child domains

Jim Stalewski JStalewski at VisaLighting.com
Fri Sep 16 13:21:31 MDT 2011


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.



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