[Freeipa-users] Using external KDC

[Dmitri Pal]

On 03/05/2014 06:24 PM, Trey Dockendorf wrote:
> Correction from my email, the condition that sets if a 389DS user is
> proxied to pam_krb5 is the "pamFilter", sorry.
>
> On Wed, Mar 5, 2014 at 5:22 PM, Trey Dockendorf<treydock at gmail.com>  wrote:
>> On Mon, Mar 3, 2014 at 7:29 PM, Dmitri Pal<dpal at redhat.com>  wrote:
>>> On 03/03/2014 07:47 PM, Simo Sorce wrote:
>>>> On Mon, 2014-03-03 at 18:42 -0600, Trey Dockendorf wrote:
>>>>> Is it possible with FreeIPA to use an external KDC or pass some or all
>>>>> authentication to an external KDC?  The KDC at our University may give
>>>>> me a one way trust if I describe my implementation plan for FreeIPA.
>>>>> Currently I use 389DS with PAM pass through using untrusted pam_krb5.
>>>>> I'd like to fully utilize FreeIPA without managing passwords since all
>>>>> my users already have University accounts.  I just want to manage
>>>>> authorization for my systems, not authentication.
>>>> You could set up a kerberos trust manually but at the moment we do not
>>>> support it in the code or the utilities.
>>>>
>>>> SSSD in particular will have no place to find identity information if
>>>> all you have is a kerberos trust, you'd need also an external identity
>>>> store to point to, but there is no builtin code in SSSD to link the 2
>>>> domain at this point.
>>>>
>>>> We are planning on working on IPA-to-IPA trust, and possibly
>>>> IPA-to-*other* so any requirements you can throw at us will be made part
>>>> of the consideration and planning to add this kind of functionality in
>>>> the future.
>>>>
>>>> NM B HTH,
>>>> Simo.
>>>>
>>> Can you describe your workflows because I have some idea in mind?
>> Right now the workflow I have with 389ds using PAM Pass Through Auth
>> is the following:
>>
>> For users with the proper attribute defined in 'pamIDAttr'
>>
>> client --->  389DS --->  389DS server's pam_krb5 --->  Campus KDC
>>
>> For users lacking the attribute for 'pamIDAttr'
>>
>> client --->  389DS
>>
>> The Kerberos setup currently on the 389DS server is untrusted (no krb5.keytab).
>>
>> The ideal workflow with FreeIPA would be
>>
>> client ---->  IPA --->  Campus KDC
>>
>>> Would you be OK if your accounts would be in IPA but the authentication
>>> would be proxied out?
>> This is fine with me.  Does the idea you describe allow for some
>> authentication (ie system accounts or internal accounts) to be handled
>> by FreeIPA?  That's the benefit to us when using PAM Pass Through
>> Auth, is that we can conditionally proxy out the authentication.
>>
>>> The idea is that you can use OTP RADIUS capability to proxy passwords to
>>> your main KDC.
>>>
>>> client ---OTP--->  IPA --->  OTP Proxy --->  RADIUS --->  Your KDC
>>>
>>> Disclaimer: that would defeat the purpose of Kerberos and the password will
>>> be sent over the wire but it seems that you are already in this setup.
>>>
>>> Would you be interested to give it a try?
>> Absolutely.  Right now I need to contact our campus IT group and let
>> them know what I require to make our setup work.  I have been told a
>> one way trust is the most I can get.  Will that facilitate what you
>> described?

You do not need trust for that setup. Any user account (i am not sure 
about special system accounts that are not created in cn=users) would be 
able to go to external RADIUS server.

>>
>>> Would require latest SSSD and kerberos library on the client though but
>>> would work with LDAP binds too.
>> Latest SSSD and Kerberos that's available in EL6, or latest upstream?

Upstream.

Please take a look at the design page: 
http://www.freeipa.org/page/V3/OTP - that will give you an idea about 
the internals.

Latest upstream UI should be able to allow to configure external RADIUS 
servers and then change per user policy to proxy via RADIUS. Then you 
can try binding with LDAP to IPA using password from your main KDC.
Then you can use SSSD on the same system to try to authenticate using 
Kerberos. You will create a new user, set him to use RADIUS server for 
authentication and then try to su to this user or ssh into the box as 
that user. It should work and klist should report a TGT for this user on 
the box.

>>
>>>
>>> --
>>> Thank you,
>>> Dmitri Pal
>>>
>>> Sr. Engineering Manager for IdM portfolio
>>> Red Hat Inc.
>>>
>>>
>>> -------------------------------
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>>>
>>>
>>>
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-- 
Thank you,
Dmitri Pal

Sr. Engineering Manager for IdM portfolio
Red Hat Inc.


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