Subject: Re: Basic Constrains and Key Usage processing

From: [email-masked] (Peter Gutmann)
Date: Tue, 25 Jun 2002 20:29:22 +1200 (NZST)

Stephen Kent <[email-masked]> writes:

>We had all these discussions a long time ago. The PKIX documents do not make
>concessions for legacy designs; they set standards for what should be done
>going forward.

The original message, however, requested guidelines on what would work with
real-world implementations, not what standards require to move forward.  The
problem with many PKIX documents is that they describe an ideal situation which
doesn't exist in reality.  As a result, it's possible to create implementations
which are PKIX-compliant, or which work in the real world, but not both.  A
recent example of this (which happens to relate to the use of the keyUsage
extension) results in fully PKIX-compliant implementations rejecting a
significant number of real-world certs because they're not PKIX compliant.
Since these problems aren't even noticed by the majority of cert-handling
implementations, the logical corollary is that said majority of implementations
are similarly not PKIX-compliant.  I don't know how many hacked-up versions of
my code exist out there where users have had to disable various checks to get
it to process certs, because the other option, telling a CA that the certs
they're issuing aren't standards-compliant, is largely an exercise in futility
(this is used to advantage by a number of European CAs, since in order to
handle their certs you need to buy the CA's proprietary software).

This difference between standards and real life was the motivation for the
creation of the X.509 style guide, and why in RFC drafts I always include
sections telling readers that although the standard may say X, in practice
everyone seems to do Y instead, and that implementors should be prepared for
this.  I guess I need to update the style guide a bit, it's been laying dormat
for awhile.

Peter.

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From: "David P. Kemp" <[email-masked]>
Date: Tue, 25 Jun 2002 10:40:23 -0400

Peter,

In your experience, do implementors of IPSEC or TLS receive much slack
if they are not "strict in what they generate"?   Should not CAs that
mention the PKIX brand be held to a similar standard?

Dave

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From: Stephen Kent <[email-masked]>
Date: Tue, 25 Jun 2002 11:11:04 -0400

Peter,

We are producing standards that we want vendors to follow. This is 
not an academic exercise. We have good reasons for why we have 
adopted conventions that differ from what vendors have done, and 
these reasons have been documented. So, the goal is to get vendors to 
do the right thing, not to accommodate vendor choices that may have 
been made because of lack of foresight, lack of a transition strategy 
re backwards compatibility, proprietary advantage, ....

Steve