[Freeipa-devel] certmonger everywhere

[Fraser Tweedale]

On Tue, Dec 15, 2015 at 04:23:33PM +0100, Martin Kosek wrote:
> On 12/15/2015 08:54 AM, Jan Cholasta wrote:
> > Hi,
> > 
> > recently I and David discussed the direction of installers with regard to
> > requesting certificates. Currently there are four (!) different ways of
> > requesting certificates in the installer [1][2][3][4]. We would like to reduce
> > it to one.
> > 
> > Since all the certificates are tracked by certmonger and certmonger already
> > knows how to request certificates from Dogtag (and other CAs), we believe that
> > all certificates should be requested using certmonger.
> > 
> > Taking our meditation further, we thought "Why not use certmonger for the
> > cert-request command as well?" What is the benefit, do you ask?
> > 
> >  a) single code path for requesting certificates (seriously, the current state
> > is ridiculous)
> > 
> >  b) use any CA supported by certmonger as the IPA CA (i.e. Let's Encrypt [5],
> > once certmonger gains support for it)
> > 
> >  c) automate external CA install, using any CA supported by certmonger [6]
> > 
> >  d) support multiple different CAs at once (generalization of the Sub-CA feature)
> > 
> >  e) uniform configuration on clients (configure once, use forever, even for
> > CA-less)
> > 
> > The idea is to store configuration for the different CAs in LDAP and have
> > cert-request redirect requests to a proper CA helper according to that
> > configuration. This would require a new certmonger D-Bus method to call a CA
> > helper without associated certificate storage, but that should be rather easy
> > to add. In return, it would be possible to do all of the above.
> > 
> > Note that this should not conflict with tighter integration with Dogtag
> > (profiles, ACLs, etc.).
> > 
> > Comments are welcome.
> > 
> > Honza
> > 
> > [1]
> > <https://git.fedorahosted.org/cgit/freeipa.git/tree/ipapython/certmonger.py#n305>
> > [2]
> > <https://git.fedorahosted.org/cgit/freeipa.git/tree/ipaserver/install/certs.py#n329>
> > 
> > [3]
> > <https://git.fedorahosted.org/cgit/freeipa.git/tree/ipaserver/install/certs.py#n355>
> > 
> > [4]
> > <https://git.fedorahosted.org/cgit/freeipa.git/tree/ipaserver/install/cainstance.py#n878>
> > 
> > [5] <https://fedorahosted.org/freeipa/ticket/5431>
> > [6] <https://fedorahosted.org/freeipa/ticket/5317>
> 
> Interesting idea! I would be definitely interested to hear what Fraser, Rob or
> Simo thinks here.
> 
For the installer cases, +1 from me.

For the general cert-request case, currently Certmonger calls `ipa
cert-request' using host credentials (Kerberos), and IPA framework
does some validation (e.g. ensure CN and altNames correspond to
subject principal), before requesting cert from Dogtag using RA
Agent credentials (TLS client cert).

There are a few things that have to happen before Certmonger can
request certs directly from Dogtag, in IPA scenario:

1. support SNPEGO authentication in Dogtag (work has started)

2. perform all validation that IPA framework currently performs in
   Dogtag, or make the validation no longer required by pulling cert
   data straight from LDAP according to the profile.

3. Requestor credentials must be delegated to Certmonger so that the
   correct principal is used to talk to Dogtag.  Presumably this would
   be S4U2Proxy constrained delegation with host/<hostname> as
   impersonator and Dogtag service principal as target.

At that point `ipa cert-request' can become a client-side command
that merely configures Certmonger to request the cert.

Cheers,
Fraser