[Freeipa-devel] FreeIPA and wildcard certificates

[Alexander Bokovoy]

On ke, 08 helmi 2017, Martin Kosek wrote:
>Hi Fraser and the list,
>
>I recently was in a conversation about integrating OpenShift with FreeIPA. One
>of the gaps was around generating a wildcard certificate by FreeIPA that will
>be used in the default OpenShift router for applications that do not deploy own
>certificates [1].
>
>Is there any way that FreeIPA can generate it? I was thinking that uploading
>some custom certificate profile in FreeIPA may let us get such certificate...
>Or is the the only way we can add it by adding a new RFE in FreeIPA, tracked in
>[2]?
Yes, we need a new RFE. There are checks in IPA that prevent wildcard
certificates to be issued:

 - we ensure subject 'cn' of the certificate matches a Kerberos principal
   specified in the request

 - we validate that host object exists in IPA when the Kerberos
   principal is host/...

We could lift off these two limitations for 'cn=*,$suffix' but there is
still a need to apply proper ACLs when issuing the cert -- e.g. some
object has to be used for performing access rights check. The wildcard
certificate does not need to be stored anywhere in the tree, but a
check still needs to be done.

For example, for Kerberos PKINIT certificate which is issued to KDC we
don't store public certificate in LDAP either but we do two checks:
 - a special KDC certificate profile is used to issue the cert
 - a special hostname check is done so that only IPA masters are able to
   request this certificate

For the wildcard certificate I think we could have following:
 - use a separate profile for the wildcard, associated with a sub-CA
 - hardcode CN default in the profile to always be 'CN=*, O=$SUB_CA_SUBJECT' so that
   actual certificate ignores requested CN.
 - a special check to be done so that only wildcard-based subject
   alternative names can be added to a wildcard certificate request
 - all Kerberos principal / hostname checks are skipped.
 - actual ACL check is done by CA ACL.

-- 
/ Alexander Bokovoy