On 17.6.2016 09:34, Fraser Tweedale wrote:
On Mon, May 09, 2016 at 09:35:06AM +0200, Jan Cholasta wrote:
Hi,

On 6.5.2016 08:01, Fraser Tweedale wrote:
Hullo all,

FreeIPA Lightweight CAs implementation is progressing well.  The
remaining big unknown in the design is how to do renewal.  I have
put my ideas into the design page[1] and would appreciate any and
all feedback!

[1] http://www.freeipa.org/page/V4/Sub-CAs#Renewal

Some brief commentary on the options:

I intend to implement approach (1) as a baseline.  Apart from
implementing machinery in Dogtag to actually perform the renewal -
which is required for all the approaches - it's not much work and
gets us over the "lightweight CAs can be renewed easily" line, even
if it is a manual process.

For automatic renewal, I am leaning towards approach (2).  Dogtag
owns the lightweight CAs so I think it makes sense to give Dogtag
the ability to renew them automatically (if configured to do so),
without relying on external tools i.e. Certmonger.  But as you will
see from the outlines, each approach has its upside and downside.

I would prefer (3), as I would very much like to avoid duplicating
certmonger's functionality in Dogtag.

Some comments on the disadvantages:

  * "Proliferation of Certmonger tracking requests; one for each
FreeIPA-managed lightweight CA."

    I don't think this is an actual issue, as it's purely cosmetic.

  * "Either lightweight CA creation is restricted to the renewal master, or
the renewal master must observe the creation of new lightweight CAs and
start tracking their certificate."

    IMO this doesn't have to be done automatically in the initial
implementation. You could extend ipa-certupdate to set up certmonger for
lightweight CAs and have admins run it manually on masters after adding a
new lightweight CA. They will have to run it anyway to get the new
lightweight CA certificate installed in the system, so it should be fine to
do it this way.

I have updated the renew_ca_cert post-save script to perform the
database update necessary for CA replicas to pick up the new cert.
What remains is the command to tell certmonger to track the CA.

You mentioned ipa-certupdate but perhaps ipa-cacert-manage is a
better fit, e.g.:

    ipa-cacert-manage track <CA-ID>

It would look up the necessary info (basically just the CA-ID) and
set up the certmonger tracking.

No. ipa-cacert-manage updates global configuration in LDAP, whereas ipa-certupdate applies the global configuration on the local system. Updating certmonger configuration is the latter, hence it should be done in ipa-certupdate.

Also, I don't think we should expose (un)tracking certificates by CA ID to users, as all our CA certificates should always be tracked.


It could be an error to run the command on other than the renewal
master.

Note that the main CA certificate is tracked on all CA servers, not just the renewal master, otherwise it wouldn't get updated on the other CA servers after renewal. I would think the same needs to be done for lightweight CA certificates, unless there is a different mechanism for distributing the certificates to other CA masters, in which case I would prefer if the mechanism was also used for the main CA certificate.


An untrack command could also be provided.

Thoughts?

  * "Development of new Certmonger renewal helpers solely for lightweight CA
renewal."

    It would be easier to extend the existing helpers. I don't think there
is anything preventing them from being used for lighweight CAs, except not
conveying the CA name, which should be easy to implement.


I would also avoid starting with (1), I don't believe it adds any real
value. IMHO the first thing that should be done is implement lightweight CA
support in certmonger (add new 'request' / 'start-tracking' option for CA
name, store it in tracking requests, pass it to CA helpers in a new
environment variable).


Honza

--
Jan Cholasta


--
Jan Cholasta

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