Subject: [pkix] Certificate Transparency and user agent warnings

From: Jeffrey Walton <[email-masked]>
Date: Tue, 21 Apr 2015 19:59:03 -0400

According to the CT FAQ at
http://www.certificate-transparency.org/faq, there are three ways to
avoid warnings in some user agents:

  * X509v3 Certificate Extension
  * TLS Extension
  * OCSP Stapling

If a private PKI includes a subordinate in the chain that is name
constrained, then can that be used in lieu of the three methods above?

RFC 6962 does not discuss it (https://tools.ietf.org/html/rfc6962).
But I feel like if the problem is issuing server certificates for
domains *not* authorized to do so, then name constraints seems like a
natural solution.

Thanks in advance.

---

From: Rob Stradling <[email-masked]>
Date: Wed, 22 Apr 2015 10:03:56 +0100

(Cross-posting to TRANS)

Jeffrey, does "private PKI" mean...

1. A publicly-trusted root, a publicly-logged intermediate, and 
non-logged end-entity certs.
or
2. A non-publicly-trusted root, a non-logged intermediate, and 
non-logged end-entity certs.

If 1, then please take a look at the mechanism in 6962-bis [1] for 
logging a name-constrained intermediate CA certificate in place of the 
end-entity certs issued under it.

If 2, then I suspect that this is out of scope for CT, since it seems 
likely that most CT logs accepted by browsers will only issue SCTs for 
(intermediate or end-entity) certs that chain to publicly-trusted roots.

[1] 
https://datatracker.ietf.org/doc/draft-ietf-trans-rfc6962-bis/?include_text=1

-- 
Rob Stradling
Senior Research & Development Scientist
COMODO - Creating Trust Online

---

From: Jeffrey Walton <[email-masked]>
Date: Wed, 22 Apr 2015 05:20:52 -0400

Hi Rob,

Thanks.

> If 2, then I suspect that this is out of scope for CT, since it seems likely
> that most CT logs accepted by browsers will only issue SCTs for

Yes, this is the case.

Is there a call-out or spec somewhere that states SCT is required of
public CAs; but not CAs for internal or private PKIs?

I'm concerned with an in-house, private PKI and the warnings that have
been showing up in Chrome.

Jeff

On Wed, Apr 22, 2015 at 5:03 AM, Rob Stradling <[email-masked]> wrote:
> 1. A publicly-trusted root, a publicly-logged intermediate, and non-logged
> end-entity certs.
> or
> 2. A non-publicly-trusted root, a non-logged intermediate, and non-logged
> end-entity certs.
>
> If 1, then please take a look at the mechanism in 6962-bis [1] for logging a
> name-constrained intermediate CA certificate in place of the end-entity
> certs issued under it.
>
> If 2, then I suspect that this is out of scope for CT, since it seems likely
> that most CT logs accepted by browsers will only issue SCTs for