[Freeipa-users] IPA PKI Questions

[thierry bordaz]

On 04/26/2017 11:58 PM, Rob Crittenden wrote:
> Kendal Montgomery wrote:
>> Hi all,
>>
>>   
>>
>> I’ve been struggling the last few days with rebuilding part of my
>> FreeIPA infrastructure, which has lead me to some questions about how
>> some of the IPA infrastructure works.  To give a bit of background, I
>> have two IPA servers (my initially installed IPA server, and a replica)
>> both of which have DNS, NTP, and CA roles.  I’m running CentOS 7.3,
>> FreeIPA 4.4 currently (upgraded from original CentOS 7 installations
>> which I believe was FreeIPA 4.1? initiall).  I have several remote sites
>> that each have two IPA server replicas that have replication topology
>> segments for domain and ca suffixes back to the two on-prem IPA
>> servers.  This has been working quite well for over a year now, through
>> the upgrades, etc.  Occasionally I get an issue with getting some
>> conflicting records in LDAP, which I’ve cleared up by following some of
>> the documentation out there.  It seems when this happens however, I end
>> up getting into a situation where replication stops working, and I end
>> up needing to “refresh” the installations. I have done this once so far,
>> and am in the process again currently, by deleting each remote IPA
>> server (ipa server-del), then re-installing each server to get a clean
>> copy of the databases for everything.  Last time I had no issues doing
>> this.  This time around, I’m running into some issues with the CA
>> setup.  I seem to be able to run ipa-replica-install just fine without
>> the --setup-ca option.  I may be running into some issues identified in
>> an earlier post this week, so I’ll ask about this issue separately if I
>> continue to have problems.  In working through these issues, I realized
>> I don’t really know enough about how the interaction between the IPA
>> clients and IPA server is working, with regard to the PKI
>> infrastructure.  I have some questions on what server roles I need at
>> each site and how the PKI infrastructure works within the IPA
>> environment, and how the clients communicate to it:
>>
> You don't need to uninstall a master in order to fix replication issues.
> You can re-initialize it from a working master. I'm pretty sure that if
> you re-init one you need to re-init them all though, to be safe. I cc'd
> a couple of 389-ds devs to clarify.
Hi Kendal,

Regarding re-initialization it is a safety practice to re-init all of 
them when you need to re-init one.
It is sometime not necessary to re-init all servers but checking if it 
is necessary or not take usually more time that a full reinit. A concern 
of full reinit is if you have large database (so reinit take longer) or 
difficulty to find a calm period to do this this task.

Reading your description I understand that you had to cleanup some 
conflicting entries (ldapsearch -D 'cn=directory manager' -W -b 
"<suffix>" "(objectclass=nsds5ReplConflict)" dn). The management of 
those entries will greatly improve but it is a complex task, with many 
corner cases. The better is to avoid creation of those entries. A 
recommendation to avoid those entries is, avoid parallel upgrade of IPA 
servers and do not disconnect IPA servers when doing those upgrade.

regards
>
>> 1)       How do the IPA clients discover servers with the CA role and
>> use them?
> They don't, they talk to one of the IPA masters and lets that figure it out.
>
> An IPA master does this by looking at cn=<host>,
> cn=masters,cn=ipa,cn=etc,$SUFFIX
>
>> 2)       Is all this interaction done through APIs on the IPA server –
>> in other words, are these requests fielded by the IPA server and proxied
>> somehow to known servers with the CA role?
> Right.
>
>> 3)       Do the clients need “direct” access to a server with the CA
>> role to request and obtain certificates and renewals? (i.e. do I need
>> each IPA server to have the CA role)?
> Nope.
>
>> 4)       Is it sufficient to just have one server with CA role at each
>> site?  Or even just one at the main on-prem site?
> One per site may be sufficient, you want to ensure that you have > 1 CAs
> and since you have separate sites, having one at each would give you
> lots of leeway in case of catastrophe.
>
> rob