Re: Samba authentication to Kerberos via OpenLDAP, third and last try

[Buchan Milne <bgmilne@staff.telkomsa.net>]

On Thursday 03 April 2008 22:39:26 Wes Modes wrote:
> So far answers I've received about this have been inconsistent at best
> and downright inaccurate at worst.  I'm going to try one more time and
> see if, at the very least, someone can give me a lead.  I ask you to
> consider what I'm asking remotely possible, and then seek a solution.
> (Particularly before one blasts off an ill-thought out message that says
> simple, "Can't be done," simple because you've never done it or haven't
> heard of it being done.)  So consider this a challenge or a riddle.
>
>    1. I have an OpenLDAP directory server that I am using for user and
>       group information.  I would like to use it also to authenticate
>       against.  This way, whatever I hook up to it (Samba, webstuff, PHP
>       apps, CMS) can both authenticate and authorize from one source.
>    2. There is a separate Kerberos server that has users' campus-wide
>       passwords.  I have access to it, but do not control it.
>    3. I have a separate linux file server running Samba.  PCs and Macs
>       will connect to it.

Let's ignore the solution you proposed, and look at what you *can* do.

1)You can have the OpenLDAP directory server authenticate simple binds against 
the KDC

2)You can (if your OpenLDAP directory server has appropriate service 
principals and their tickets or keytabs) authenticate LDAP access to your 
OpenLDAP directory server via Kerberos

3)You can have all your user and group information (including the samba 
password hashes, samba group mappings etc.) in the OpenLDAP directory server.

Thus far, there isn't really a means for you to authenticate access from 
Windows clients accessing your samba server with the same credentials that 
they use for (1) or (2).

However, the "Active Directory Password Cache" overlay sitting in ITS may 
help. Instead of (1), you may rather choose to use the adpwc overlay, simple 
binds against the directory would first try and authenticate with the 
password hash stored in the userPassword attribute in-directory. If that 
fails, the overlay intercepts that, and tries a Kerberos authentication with 
the principal stored in the krbPrincipalName attribute. If this succeeds, the 
overlay hashes the password and stores the has in the userPassword attribute, 
and hashes it with a samba-compatible hash and stores the has in the 
sambaNTPassword attribute.

Now, authentications with the same password will not contact the KDC, and 
samba should be able to authenticate the user with the hash in the OpenLDAP 
directory.

The inconvenience here is that if the password has changed on the KDC, Samba 
won't get the new password until the directory server has seen a simple bind 
with the new password. The inconvenience could be reduced by putting in a 
simple web script allowing users to sync their passwords.

The password expiry aspects also need some looking at ...


Regards,
Buchan