[Freeipa-users] Services and Keytabs for load-balanced hostnames

[Mark Heslin]

Folks,

I'm looking for the best approach to take for configuring IdM clients to 
access web services (HTTP)
with keytabs when a front-end load-balanced hostname is in place.

I have a distributed OpenShift Enterprise configuration with three 
broker hosts (broker1, broker2, broker3)
with all three configured as IdM clients.

IdM is configured with one server (idm-srv1.example.com), one replica 
(idm-srv2.example.com); an HTTP service
has been created for each broker host:

   # ipa service-add HTTP/broker1.example.com
   # ipa service-add HTTP/broker2.example.com
   # ipa service-add HTTP/broker3.example.com

A DNS round-robin hostname called '*broker**.example.com*' has also been 
configured to distribute broker requests
across the three brokers:

   # ipa dnsrecord-add example.com broker --a-ip-address=10.0.0.11
   # ipa dnsrecord-add example.com broker --a-ip-address=10.0.0.12
   # ipa dnsrecord-add example.com broker --a-ip-address=10.0.0.13

Effectively, this creates a DNS A record that acts as a pseudo DNS 
load-balancer.

To access the HTTP services, we have been creating keytabs for for the 
first broker host:

    # ipa-getkeytab -s idm-srv1.example.com -p 
HTTP/*broker1*.example.com at EXAMPLE.COM
                                 -k 
/var/www/openshift/broker/httpd/conf.d/http.keytab

and copying the keytab over to the other two OpenShift broker hosts.

This all works fine but in the event that *broker1* should go down, the 
other broker hosts will lose access
to the web service. Ideally, we would like to have web services use the 
more generic, "load balanced"
hostname (*broker.example.com*) and in turn have the keytabs use this 
name as well.

I tried creating an HTTP service using the "load balanced" hostname 
(*broker.example.com*) but that appears to fail
due to *broker.example.com* not being a valid host within IdM:

    # ipa service-add HTTP/broker.example.com
    ipa: ERROR: The host 'broker.example.com' does not exist to add a 
service to.

In the F18 FreeIPA guide it discusses creating a combined keytab file 
(Section 6.5.4) using ktutil:

http://docs.fedoraproject.org/en-US/Fedora/18/html/FreeIPA_Guide/managing-services.html#Using_the_Same_Service_Principal_for_Multiple_Services

but would that still work as intended should a broker host go down?

The next section (6.5.5) mentions creating a keytab to create a service 
principal that can be used across multiple hosts:

   # ipa-getkeytab -s kdc.example.com -p HTTP/server.example.com -k 
/etc/httpd/conf/krb5.keytab -e des-cbc-crc

Which seems more in-line with my thinking and exactly what we've been 
doing but again, if I try to do that
using the "load balanced" hostname (*broker.example.com*) it fails sicne 
it's not a valid host within IdM.

What is the best method to doing this?

Thank you,

-m


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