Using a Dogtag instance as external CA for FreeIPA installation

A FreeIPA user recently had issues installing FreeIPA with an external CA. He was using Dogtag certificate system as external CA and FreeIPA installation was failing, complaining about the certificate provided by Dogtag.

So I decided to try the same deployment and share my findings in this post.

A little background…

FreeIPA server can be configured to act as a Certificate Authority inside FreeIPA IDM domain. It will then be able to create the certificates used by the LDAP server, the Apache server used for the Web GUI or the users and hosts.

This CA can be set-up in different ways:

• The CA is a root CA, meaning that its certificate is self-signed
• or the CA is subordinate to an external, 3rd-party CA, meaning that its certificate is signed by the 3rd party CA.

There are a wide range of products that can be used as 3rd-party CAs, among which Dogtag certificate system. In this blog post, I will explain how Dogtag can provide the certificate for IPA CA.

Instructions

The following instructions apply to Fedora 24. They will:

1. run the 1st step of ipa-server-install to generate a CSR
2. submit the CSR to Dogtag and have Dogtag issue a certificate for FreeIPA server
3. run the 2nd step of ipa-server-install with the certificate obtained in step 2.

For instructions to setup the Dogtag server, you can refer to this post: Dogtag installation.

 

FreeIPA server installation – step 1

In order to install FreeIPA with an externally-signed CA, we must use the –external-ca option of ipa-server-install. The installation is then a multi-step install, where:

• ipa-server-install produces a CSR
• we need to submit this CSR to the external CA, that will in return provide a certificate and certificate chain
• we need to run ipa-server-install a 2nd time, with different options and providing the certificates obtained in the previous step.

So let’s run the first step of ipa-server-install:

root@ipaserver$ ipa-server-install --setup-dns \
 --auto-forwarders \
 --auto-reverse \
 -n ipadomain.com \
 -r IPADOMAIN.COM \
 -p Secret123 -a Secret123 \
 --external-ca \
 -U
[...]
Configuring certificate server (pki-tomcatd). Estimated time: 3 minutes 30 seconds
 [1/8]: creating certificate server user
 [2/8]: configuring certificate server instance
The next step is to get /root/ipa.csr signed by your CA and re-run /sbin/ipa-server-install as:
/sbin/ipa-server-install --external-cert-file=/path/to/signed_certificate --external-cert-file=/path/to/external_ca_certificate

 

Generation of the certificate using Dogtag

We then need to copy this CSR on the Dogtag instance and submit the CSR, approve it and export the certificate.

The submission is an important step as it allows to specify a profile. Basically, if we pick caCACert profile, we signal our intent to use the produced certificate as a Certificate Authority in our FreeIPA deployment, and the resulting certificate will contain the required extensions:

root@dogtag$ pki ca-cert-request-submit --profile caCACert --request-type pkcs10 --csr-file ipa.csr
-----------------------------
Submitted certificate request
-----------------------------
 Request ID: 7
 Type: enrollment
 Request Status: pending
 Operation Result: success

Note the Request ID as we will need it in order to approve the submission:

root@dogtag$ pki -c Secret123 -d /root/.dogtag/nssdb/ -n "PKI Administrator for example.com" cert-request-review 7 --action approve
------------------------------
Approved certificate request 7
------------------------------
 Request ID: 7
 Type: enrollment
 Request Status: complete
 Operation Result: success
 Certificate ID: 0x7

Note the Certificate ID as we will need it to export the certificate into a file ipa.cert:

root@dogtag$ pki -c Secret123 -d /root/.dogtag/nssdb/ -n "PKI Administrator for example.com" cert-show 7 --encoded --output ipa.cert

We will also need the dogtagca certificate chain:

root@dogtag$ pki ca-cert-show 1 --encoded --output dogtagca.cert

At this point, we have a new certificate and chain (ipa.cert and dogtagca.cert), that we need to copy on FreeIPA server. We can resume FreeIPA installation.

FreeIPA server installation – step 2

In order to resume FreeIPA installation, we will follow the instructions provided in step 1:

root@ipaserver$ /sbin/ipa-server-install --external-cert-file=ipa.cert --external-cert-file=dogtagca.cert

 

The installation will resume and use the ipa.cert for IPA Certificate Authority. That’s it!

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