[cabfpub] Fwd: OCSP exception contingent on must-staple (was Re: SHA1 certs issued this year chaining to included roots)
rbarnes at mozilla.com
Wed Jan 20 15:26:12 UTC 2016
Redirecting to CABF, where I meant to send it in the first place...
---------- Forwarded message ----------
From: Richard Barnes <rbarnes at mozilla.com>
Date: Wed, Jan 20, 2016 at 9:35 AM
Subject: OCSP exception contingent on must-staple (was Re: SHA1 certs
issued this year chaining to included roots)
To: Rob Stradling <rob.stradling at comodo.com>
Cc: Charles Reiss <woggling at gmail.com>, "
mozilla-dev-security-policy at lists.mozilla.org" <
mozilla-dev-security-policy at lists.mozilla.org>
Changing the subject line as this is branching a bit...
On Wed, Jan 20, 2016 at 8:24 AM, Rob Stradling <rob.stradling at comodo.com>
> On 19/01/16 21:13, Charles Reiss wrote:
>> On 01/19/16 11:49, Jakob Bohm wrote:
>> If there is no OCSP, it obviously cannot be stapled.
>> The CA/Browser forum BRs contemplate OCSP stapling without an OCSP
>> being listed in the certificate in section 22.214.171.124.c ("The HTTP URL of
>> Issuing CA’s OCSP responder MAY be omitted, provided that the Subscriber
>> “staples” the OCSP response for the Certificate in its TLS handshakes
>> [RFC4366].") I assume the idea is that the OCSP responder URL would be
>> configured in the server and that this would make the certificate
>> slightly smaller.
> IIRC, the original motivation for this text was to make it possible to
> suppress OCSP requests directly from TLS clients (that don't support OCSP
> Stapling). In particular, there was a concern that some OCSP responders
> might not be able to cope with the OCSP traffic generated by certs used by
> sites with extremely high numbers of users.
> At the time, Firefox didn't support OCSP Stapling, and it was much less
> common for CAs to use CDNs for their OCSP responders. (Indeed, some CAs
> didn't even support OCSP back then).
This sentence has always bothered me, though, because in order to make
sense, you would have to have the CA verify that the OCSP response is
stapled, and there's not any requirement to do that. ISTM that omitting
the OCSP URL only really makes sense if there's a TLS Feature extension
requiring stapling (i.e., must-staple).
The HTTP URL of the Issuing CA’s OCSP responder MAY be omitted, provided
that the Certificate contains a TLS Feature extension including the value
status_request(5). This extension requires that the Subscriber “staples”
the OCSP response for the Certificate in its TLS handshakes [RFC4366]."
If this is non-controversial, maybe this is something to add to Bowen's
ballot that's being discussed on another thread?
> Rob Stradling
> Senior Research & Development Scientist
> COMODO - Creating Trust Online
> dev-security-policy mailing list
> dev-security-policy at lists.mozilla.org
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