[Freeipa-users] IPA PKI Questions

[Rob Crittenden]

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.

> 
> 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