Chapter 4. Planning your CA services

Identity Management (IdM) in Red Hat Enterprise Linux provides different types of certificate authority (CA) configurations. The following sections describe different scenarios and provide advice to help you determine which configuration is best for your use case.

4.1. CA Services available in an IdM server

You can install an Identity Management (IdM) server with an integrated IdM certificate authority (CA) or without a CA.

Table 4.1. Comparing IdM with integrated CA and without a CA

 Integrated CAWithout a CA

Overview:

IdM uses its own public key infrastructure (PKI) service with a CA signing certificate to create and sign the certificates in the IdM domain.

  • If the root CA is the integrated CA, IdM uses a self-signed CA certificate.
  • If the root CA is an external CA, the integrated IdM CA is subordinate to the external CA. The CA certificate used by IdM is signed by the external CA, but all certificates for the IdM domain are issued by the integrated Certificate System instance.
  • Integrated CA is also able to issue certificates for users, hosts, or services.

The external CA can be a corporate CA or a third-party CA.

IdM does not set up its own CA, but uses signed host certificates from an external CA.

Installing a server without a CA requires you to request the following certificates from a third-party authority:

  • An LDAP server certificate
  • An Apache server certificate
  • A PKINIT certificate
  • Full CA certificate chain of the CA that issued the LDAP and Apache server certificates

Limitations:

If the integrated CA is subordinate to an external CA, the certificates issued within the IdM domain are potentially subject to restrictions set by the external CA for various certificate attributes, such as:

  • The validity period.
  • Constraints on what subject names can appear on certificates issued by the IDM CA or its subordinates..
  • Constraints on whether the IDM CA can itself, issue subordinate CA certificates, or how "deep" the chain of subordinate certificates can go.

Managing certificates outside of IdM causes a lot of additional activities, such as :

  • Creating, uploading, and renewing certificates is a manual process.
  • The certmonger service does not track the IPA certificates (LDAP server, Apache server, and PKINIT certificates) and does not notify you when the certificates are about to expire. The administrators must manually set up notifications for externally issued certificates, or set tracking requests for those certificates if they want certmonger to track them.

Works best for:

Environments that allow you to create and use your own certificate infrastructure.

Very rare cases when restrictions within the infrastructure do not allow you to install certificate services integrated with the server.

Note

Switching from the self-signed CA to an externally-signed CA, or the other way around, as well as changing which external CA issues the IdM CA certificate, is possible even after the installation. It is also possible to configure an integrated CA even after an installation without a CA.

4.2. CA subject DN

The Certificate Authority (CA) subject distinguished name (DN) is the name of the CA. It must be globally unique in the Identity Management (IdM) CA infrastructure and cannot be changed after the installation. In case you need the IdM CA to be externally signed, you might need to consult the administrator of the external CA about the form your IdM CA Subject DN should take.

4.3. Guidelines for distribution of CA services

Following steps provide guidelines for the distribution of your certificate authority (CA) services.

  • Install the CA services on more than one server in the topology

Replicas configured without a CA forward all certificate operations requests to the CA servers in your topology.

Warning

If you lose all servers with a CA, you will lose all the CA configuration without any chance of recovery. In such case you need to set up new CA and issue and install new certificates.

  • Maintain a sufficient number of CA servers to handle the CA requests in your deployment

For recommendation see the following table:

Table 4.2. Guidelines for setting up appropriate number of CA servers

Description of the deploymentSuggested number of CA servers

A deployment with a very large number of certificates issued

Three or four CA servers

A deployment with bandwidth or availability problems between multiple regions

One CA server per region, with a minimum of three servers total for the deployment

All other deployments

Two CA servers