Re: [TLS] comments on draft-ietf-tls-tls13-19

[Nikos Mavrogiannopoulos <[e-mail]>]

On Sun, 2017-04-23 at 12:01 -0400, Ryan Sleevi wrote:

> > 
> > As for what the TLS library I have written does if OCSP staple
> > lacks
> > NextUpdate, it outright causes handshake failure and fatal alert.
> 
> So far, the preference on our end has been for a TLS library that
> doesn't have to have deeply-ingrained knowledge of the PKI, including
> OCSP, and instead treat these as separate layers. This PR
> necessitates that awareness by force of spec, 

That's intentional. Not every application is firefox or chrome and thus
application writers cannot be expected to set sane defaults for OCSP
validity time _when the nextUpdate field is missing_. The reason they
cannot be expected to do that, is that it is not by way obvious what to
do. Ilari's implentation closes the connection, mine sets a limit of 15
days, and I guess each and every other one behaves differently. It is
the role of the standards to clarify uncertainties for implementers or
forbid such options (I'd equally be happy if we have a text that
forbids an empty nextUpdate field in OCSP responses to be used in the
context of TLS 1.3 ocsp stapling).

>  Given that stapling "issues" exist even without stapling, it does
> seem an unnecessary reach to include within the spec.

There is a usability and interoperability issue there. Given that there
is no common interpretation of what the missing nextUpdate field means
in terms of validity, there some equally valid interpretations:
 1. the response is invalid for use in TLS 1.3
 2. the response is valid for a limited amount of time 1, 7, 8, 9, 15
days
 3. the response is valid for an unlimited amount of time (which raises
 the question of why staple at all in that case?)

Without a clarification in the spec, we are going to see
implementations that fail when encountered with such response,
implementations that work fine, and implementations that claim the
response is too old. That would most likely result to ocsp stapling
becoming the thing to disable for things to work.

regards,
Nikos