[Freeipa-users] External Collaboration Domains

[Dmitri Pal]

On 03/30/2014 03:14 PM, Nordgren, Bryce L -FS wrote:
>> I think it does not really differ from what I described, conceptually.
>> It is, however, requiring much more work than what I described.
>>
>> FreeIPA has flat LDAP DIT. Adding support for separate OUs is in itself a non-
>> trivial task.
> Ah. Well since that's the case, separate OUs are gone. (You may have to hit "reload" in your browser to get the new figure.) It does require that the RDN of all external entities encode both the name and the realm of the external Kerberos principal in order to avoid collisions. Is the current "external user" provisioning method able to handle the same name coming from two domains or does it assume that collisions will never happen?
>
>> PKINIT use in Kerberos is a big issue. Right now certificates produced by
>> FreeIPA do not include special extension that Kerberos KDC requires to have
>> PKINIT working. We have a ticket to solve this but it depends on few items
>> missing in FreeIPA, Dogtag, and nss. Solving it is required for full OTP use, so
>> we might gain this feature sooner or later.
> The proposal actually doesn't involve producing kx509 certificates, only consuming them. :) I think these are two issues which can be handled in parallel rather than having one block the other. ;)
>
>> What's reasonable and can be relatively easily pulled in from your proposal is
>> a mechanism to get users automatically provisioned in FreeIPA based on
>> their cross realm identities. For example, for cross realm trust with AD we
>> have means to selectively block certain SIDs from being imported from the
>> AD. The rest is recognized and accepted but no local external groups created
>> for them. We simply can automate creating the groups on login attempt if
>> SIDs involved aren't blocked. This automation should solve majority of
>> administrative load.
>  From my cursory examination of the code, I proposed auditing the KDC's AS and TGS conversations to trigger this automatic provisioning. Is this an approach worth keeping?
>
> I understand that IPA's bread and butter is to attach itself to a pre existing AD domain to simplify the administration of Linux machines within the same administrative boundaries.  This is a subset of Use Case 1. I just want to make sure that there's a plan in place for situations where the domain of origin is not AD, and no SID is exported  (the rest of Use Case 1, and Use Cases 2&  3.) This is just a generalization of the procedure to allow "AD" users access to services such that users from non-AD realms can also be included.
>
> Use Case 1 could be named "Intra-organizational cross-realm operation", Use Case 2 could be named "Inter-organizational cross realm operation", and Use Case 3 could be named "Multi-technology cross-realm operation". 2&3 involve independent administrative entities with a fair amount of autonomy. Traditional enterprise approaches are not valid for 2&3. :)
>
> Thanks for the review!
> Bryce
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Wow!
First of all thanks for a nice pictures and sharing your ideas.
A lot of work and though put into it.

Let me just point couple things:
1) It looks like the whole idea is about creating entries for external 
users on the server when external user authenticates via KDC. But don't 
we already lookup cache these users in a local SSSD cache and expose via 
the compat tree for legacy clients?
AFAIU the purpose is to be able to create local groups for the external 
users. May be we can do something and use compat tree DNs for external 
users?
In general it is better to distill the problem we are trying to solve: 
did I get it right?

2) I think PKINIT and related part of the proposal is not something that 
we would do.
Instead of PKI based Ipsilon would use GSS proxy that implements 
s4u2proxy + s4u2self to acquire a ticket on user behalf.
This functionality already exists, so there is no new code need.

3) The case when you send TGT back to the client from Ipsilon that 
authenticated user and acquired TGT on his behalf is an interesting one. 
The intent for client to later use SSH is understandable though hard to 
achieve. Currently there is no mechanism for Ipsilon or Ipsilon like 
gateways to return the TGT for a user and pass it to client browser. 
There is also no way a browser can save this TGT in the cache.

Bottom line:
Let us focus on the problem we are trying to solve here. Keep in mind 
that we have not started designing IPA to IPA trusts and Kerberos to IPA 
trusts. It might very well be that we would need to create some external 
entries for those trusts so IMO looking into these trust scenarios would 
reveal where our AD integration approach lacks external info and needs 
to be extended. If we want to solve the high level problem of trusts in 
general we need to build those specific flows and see what data is not 
in ldap and we can get it there. A simple mental exercise  suggests that 
we would need something for grouping of the identities coming from a 
vanilla trusted Kerberos domain. May be this is something we should 
drill down as a next step?




-- 
Thank you,
Dmitri Pal

Sr. Engineering Manager for IdM portfolio
Red Hat Inc.


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