[Freeipa-devel] [DESIGN] Sub-CAs; authenticating to Custodia

[Simo Sorce]

On Wed, 2016-04-20 at 11:32 +1000, Fraser Tweedale wrote:
> On Tue, Apr 19, 2016 at 07:48:27AM +0200, Jan Cholasta wrote:
> > On 14.4.2016 08:56, Jan Cholasta wrote:
> > >On 7.4.2016 16:17, Petr Spacek wrote:
> > >>On 7.4.2016 15:20, Fraser Tweedale wrote:
> > >>>On Thu, Apr 07, 2016 at 12:29:00PM +0200, Jan Cholasta wrote:
> > >>>>On 7.4.2016 12:13, Christian Heimes wrote:
> > >>>>>On 2016-04-07 11:09, Petr Spacek wrote:
> > >>>>>>On 7.4.2016 08:43, Fraser Tweedale wrote:
> > >>>>>>>Hi team,
> > >>>>>>>
> > >>>>>>>I updated the Sub-CAs design page with more detail for the key
> > >>>>>>>replication[1].  This part of the design is nearly complete (a large
> > >>>>>>>patchset is in review over at pki-devel@) but there are various
> > >>>>>>>options about how to authenticate to Custodia.
> > >>>>>>>
> > >>>>>>>[1] http://www.freeipa.org/page/V4/Sub-CAs#Key_replication
> > >>>>>>>
> > >>>>>>>In brief, the options are:
> > >>>>>>>
> > >>>>>>>1) authenticate as host principal; install binary setuid
> > >>>>>>>    root:pkiuser to read host keytab and custodia keys.
> > >>>>>>
> > >>>>>>Huh, I really do not like this. Host keytab on IPA master is one
> > >>>>>>of the most
> > >>>>>>sensitive keys we have.
> > >>>>>>
> > >>>>>>Maybe gssproxy can be used somehow, but I think it would be better
> > >>>>>>to use
> > >>>>>>separate key.
> > >>>>>>
> > >>>>>>
> > >>>>>>>2) authenticate as host principal; copy host keytab and custodia
> > >>>>>>>    keys to location readable by pkiuser.
> > >>>>>>
> > >>>>>>No, really, do not copy host keytab anywhere.
> > >>>>>>
> > >>>>>>
> > >>>>>>>3) create new principal for pkiuser to use, along with custodia keys
> > >>>>>>>    and keytab in location readable by pkiuser.
> > >>>>>>>
> > >>>>>>>I prefer option (1) for reasons outlined in the design page.  The
> > >>>>>>>design page goes into quite a bit more detail so please review the
> > >>>>>>>section linked above and get back to me with your thoughts.
> > >>>>>>
> > >>>>>>The only downside of (3) using new keys is:
> > >>>>>>... This approach requires the creation of new principals, and
> > >>>>>>Kerberos
> > >>>>>>keytabs and Custodia keys for those principals, as part of the
> > >>>>>>installation/upgrade process.
> > >>>>>>
> > >>>>>>Compared with additional SUID binary this seems as safer and
> > >>>>>>easier way to go.
> > >>>>>>FreeIPA installers already create quite a lot of principals and
> > >>>>>>keytabs so
> > >>>>>>this is well understood task.
> > >>>>>>
> > >>>>>>I would do (3).
> > >>>>>
> > >>>>>+1 for (3)
> > >>>>>
> > >>>>>A SUID binary feels like a dangerous hack.
> > >>>>
> > >>>>+1
> > >>>>
> > >>>OK, (3) it is.  Thanks all for your input.
> > >>>
> > >>>Now for next question: what should service principal name be?  I
> > >>>think `dogtag/example.com at EXAMPLE.COM' but am open to other
> > >>>suggestions, e.g. `pki/...'.
> > >>
> > >>Do you plan to attempt to standardize this name in future? I do not
> > >>expect that.
> > >>
> > >>Considering private nature of it, it should be as specific as possible to
> > >>avoid any potential conflicts with future standards.
> > >>"dogtag-key-replication"
> > >>sounds like a good candidate.
> > >
> > >IMO it shouldn't be *that* specific, considering we want to switch
> > >Dogtag from SSL to GSSAPI authentication to DS, which will probably use
> > >the same principal name. I think "ipa-pki/..." or "dogtag/..." should be
> > >fine.
> > 
> > (Forgot to CC Fraser.)
> > 
> What is HTTP client support like for principal names with service
> part /= "HTTP"?

As a target ?
None, in which case are you going to use the dogtag keytab for the
acceptor though ?

>   For communication from IPA framework to Dogtag,
> we will need a way to force the client to use an alternative service
> name.

Our pbox design says differently.
We'll just interpose gssproxy and we'll be able to safely share the HTTP
key for all services.

> As for the actual service name, I will use "dogtag/..."

Good to use as a client.

Simo.

> Cheers,
> Fraser
> 
> > >
> > >>
> > >>Before you set the name in stone make sure it does not conflict with
> > >>anything
> > >>listed on
> > >>http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml
> > >>
> > >>
> > >>These names have potential to be used by someone else.
> > >
> > 
> > -- 
> > Jan Cholasta
> 


-- 
Simo Sorce * Red Hat, Inc * New York