Subject: Re: Matching CertIDs between OCSP requests and responses

From: [email-masked] (Peter Gutmann)
Date: Fri, 16 Mar 2001 05:31:04 (NZDT)

[email-masked] writes:

>Section 4.3 of OCSP v1 states that responders SHALL support SHA1 - it doesn't
>say that they MUST use it.  Suppose I send a request, in which my CertID has
>used SHA1.  Suppose the responder then replies, but uses MD5 to form the
>CertID term corresponding to the same certificate.  Then the matching of the
>CertID term between request and response becomes less trivial than a simple
>binary comparison.

Anecdotal evidence (that chap again) suggests that everyone uses SHA1
exclusively.  Have you tried submitting a request hashed with MD5 to see how
many servers you can break?

>As mentioned earlier, the complexity of matching certificate identifiers
>between request and response increases in v2, where there are so many other
>ways to identify a certificate.

Yes, but they're all unique (there's only one way to encode an
issuerAndSerialNumber, certificate, etc), a binary compare should do for this.

I'll do a bit of experimenting next week, but I'd be very surprised if a binary
compare failed for any responder.

Peter.

---

From: Dr S N Henson <[email-masked]>
Date: Thu, 15 Mar 2001 23:44:28 +0000

> compare failed for any responder.

One responder I tested didn't get this right but that was due to a
responder bug.

Wrt multiple certificates in request I've come across two different
kinds of anomalous behaviour.

One just rejects it with malformedRequest. Another includes status
information about the first certificate and nothing for the remainder.

Steve.
-- 
Dr Stephen N. Henson.   http://www.drh-consultancy.demon.co.uk/
Personal Email: [email-masked] 
Senior crypto engineer, Celo Communications: http://www.celocom.com/
Core developer of the   OpenSSL project: http://www.openssl.org/
Business Email: [email-masked] PGP key: via homepage.