Subject: [Spasm] RFC 6960 CertID hash algorithm mismatches

From: Carl Wallace <[email-masked]>
Date: Mon, 21 Nov 2016 16:26:50 -0500

RFC 6960 (and RFC 2560 before it) includes a hash algorithm field in the
CertID structure, as shown below.

CertID ::= SEQUENCE {
  hashAlgorithm           AlgorithmIdentifier,
  issuerNameHash          OCTET STRING, -- Hash of issuer's DN
  issuerKeyHash           OCTET STRING, -- Hash of issuer's public key
  serialNumber            CertificateSerialNumber }

However, neither includes any text that compels the responder to use the
same hash algorithm in the response as the requestor used in the request.
This seems like an oversight. If this is not required, OCSP clients would
potentially need to calculate multiple sets of hash values in order to
find the status in response.

RFC5019 requires clients to use SHA1, but it also requires nothing in
terms of requiring responses match the CertID value and places no similar
SHA1 requirement on the responder. Simply requiring responders to also use
SHA1 seems like the easiest fix.

Is this something LAMPS could address with an errata?