On to, 09 helmi 2017, Piper, Nick wrote:
Hi Alexander,

Alexander Bokovoy wrote:
On to, 09 helmi 2017, Piper, Nick wrote:

We're currently using FreeIPA 4.2.0, and we have two unrelated
instances of IdM server. We'd like the user list which IPA maintains
in one, to be a superset of the other; so we're looking for one way
replication (of cn=users,cn=accounts,dc=realm, not necessarily of host
entries etc.)

We use a different 'dc' in each instance, and could use a different cn
too if needed.

In short, there is no support for IPA-IPA trust or replication. There
are many reasons for that, including some complex technical issues on
how this could be reliably working.

If you are after actual POSIX systems where users need to logon to use
their services, you may try to configure SSSD with two different domains
(for IPA1 and IPA2). You can look at discussion we had in 2014:
https://www.redhat.com/archives/freeipa-users/2014-January/msg00075.html
You are not necessarily need to enroll the machine in two different
realms, any Kerberos principal would do instead of a host principal to
authenticate against IPA LDAP (see sssd-ldap man page for details on
ldap_sasl_authid).

Thanks, so the idea here would be for SSSD (and any other software
which uses krb or LDAP) to be configured to use both our IPA instances
simultaneously. I'll ponder on this and check into if each of our
applications has support for multiple LDAP servers.

We believe we need one way sync (including passwords) to be able to
authenticate users which are mastered in the 'remote' IPA, even when
the 'remote' IPA is offline. Another option we might explore is
'cross-forest trust', although I believe this would make
authentication unavailable if the 'master' IPA is unavailable. Both
are discussed at
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html-single/Windows_Integration_Guide/index.html#summary-indirect
, but again in the context of AD/IPA rather than IPA/IPA.

I'd welcome any pointers on trust or one-way replication between two
IPA instances!

You are stuck, there is no such support between different IPA
deployments.

It would help to actually explain your real use case. So far you
outlined above your approaches to solve a problem which is not really
stated upfront.

Thanks - I'll try to explain the wider picture:

We have a Hadoop deployment which uses an instance of FreeIPA both for
the Operating Systems (using SSSD) and applications which use LDAP
(for authentication, authorisation and for directory search.) This
FreeIPA (Project IPA) is intended to be authoritative for user
accounts which are specific to the project, such as administrators,
contractors, and so on. The project fits into a wider estate, which
uses FreeIPA (call this Enterprise IPA) to manage general user
accounts.

For auditing and consistency purposes, the general users managed in
Enterprise IPA should be able to run POSIX processes under their
username (in this case YARN containers), log into project tools (which
use LDAP to Project IPA - although this could be changed to
SAML/Shibboleth which might avoid Project IPA having to validate
credentials) and so on.


+----------------------------------------------------------+
|                                                          |
| +----------------------------------------------------+   |
| |                                                    |   |
| | +-------+ +---------+ +--------+  +----------+     |   |
| | | IPA   | |Linux OS | |Linux OS|  | App using|     |   |
| | |       | |         | |        |  | LDAP     |     |   |
| | +-------+ +---------+ +--------+  +----------+     |   |
| |                                                    |   |
| |                ^                                   |   |
| |Project         +--------------------------------------------
| +----------------------------------------------------+   |  user1 can own
|                                                          |  processes here
|                                                          |
|                                                          |
|                                                          |
|                                                          |
|   +--------+    +---------+  +---------+ +------------+  |
|   |        |    |         |  |         | |            |  |
|   | IPA    |    | Linux   |  | Linux   | | App using  |  |
|   |        |    | OS      |  | OS      | | LDAP       |  |
|   +--------+    +---------+  +---------+ +------------+  |
|                                                          |
|        ^                                                 |
|        |                                                 |
| Wider Enterprise Estate                                  |
+--------|-------------------------------------------------+
        |
        |
     user1 details mastered here


If 'Enterprise' IPA was instead Active Directory, I believe the above
could be achieved with a One way Trust?
Yes, that's what would be supported now by FreeIPA.

We have an additional aim to be able to set authorisation rules in the
Project IPA (e.g., putting the Enterprise IPA users into groups where
the groups are managed in Project IPA.)
Understood.

Unfortunately, we are still far away from making IPA-IPA trust a
reality. We need to implement several features until we get to the point
that practical IPA-IPA trust is possible.

--
/ Alexander Bokovoy

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