[Freeipa-devel] [RFC] Migrating existing environments to Trust

[Dmitri Pal]

On 05/27/2014 03:52 PM, Simo Sorce wrote:
> On Tue, 2014-05-27 at 16:01 +0200, Sumit Bose wrote:
>> On Tue, Apr 15, 2014 at 11:13:38AM +0200, Sumit Bose wrote:
>>> Hi,
>>>
>>> I have started to write a design page for 'Migrating existing
>>> environments to Trust'
>>> http://www.freeipa.org/page/V3/Migrating_existing_environments_to_Trust
>>> It shall cover https://fedorahosted.org/freeipa/ticket/3318 and
>>> https://fedorahosted.org/freeipa/ticket/3979 .
>>>
>> while working on a new version of the page with more details on design
>> and implementation I came across the following problem. On the IPA
>> server there should be a way for SSSD to deliver unmodified data (no
>> view applied) or views other than the one for the IPA server to
>> processes which delivers user and group data to other clients. This are
>> mainly the extdom and the compat plugin of dirsrv.
>>
>> The two currently use standard glibc calls like getpwnam_r() to get the
>> needed data from SSSD. While they can read the view objects form the
>> LDAP tree there is no way to read the original data for users from
>> trusted domains because it is only in the cache of SSSD.
>>
>> I'm looking for a way to allow SSSD to deliver the data without changing
>> the protocol used by the NSS responder.
>>
>> One way I can think of is to use a new socket like
>> /var/lib/sss/pipes/nss_noview and create a small library for the extdom
>> and compat plugin to use the new socket. With this the plugin have to
>> apply the views on their own if needed.
>>
>> Another way would be a new command for the NSS responder with two
>> arguments, the view name (or empty for unmodified data) and a blob which
>> contains the data for the corresponding request like e.g. getpwnam_r() or
>> getgrgid_r(). Here the plugins have to use some new calls but all view
>> processing can happen in sssd and the plugins can deliver the data
>> directly.
>>
>> A drawback in both cases is that the memcache cannot be used.
>>
>> If someone has suggestions for SSSD or other ways how to deliver user
>> and group data to client with other views than the IPA server I'm all
>> ears.
> Ok this one is hard to deal with in a way that will satisfy every
> possible user.
>
> I think what we need to aim is simplicity and predictability at the
> expense of flexibility.
>
> What I mean is that freeipa servers should be allowed to only stick to
> one view, the default view for external users.

I do not understand what you mean by "one" view?
Server should be able to have "all" views.
"View" is an equivalent of the "zones".

SSSD has to get raw data from the external domain and give it to IPA.
IPA would have to merge the data coming from SSSD in server mode with 
some set of data associated with a subset of clients.
I am not sure how it will be done (compat, cos or some other mechanism) 
but this is the requirement.

So for clarity let me restate the use cases:

a) I had my users in a NIS or LDAP with POSIX attributes there. I used 
to sync users from AD. I migrate from that to IPA but want to use trust 
for my users because AD is authoritative source and I do not want/can 
put POSIX into AD.
b) I have several NIS domains that I need to consolidate. For whatever 
reasons I can't migrate to the unified POSIX namespace. I want an 
equivalent of the Centrify Zones when different clients get different 
uid/gid assignments for the same users.
c) I used sync so my POSIX attributes are in IPA but now I want to 
switch to trust.
d) I had a third party solution that had posix zoning and I want to 
replace it with the similar solution based on IPA.

Views (plural) are a way to merge data and present it to a subset of 
clients. In this context it is not really clear what you mean by "one" 
view.





>
> And then the extdom plugin will be allowed to overlay a different view
> for specific clients.
> But the default view is the baseline, no special behavior.
> If you need to 're'-override some attributes in specific views, so be
> it.
>
> Simo.
>


-- 
Thank you,
Dmitri Pal

Sr. Engineering Manager IdM portfolio
Red Hat, Inc.