OCSP hash algorithm agility

[Alan DeKok]

On Jan 11, 2017, at 4:30 AM, Stefan Winter <stefan.winter at restena.lu> wrote:
> But: FreeRADIUS

  ... OpenSSL...

> sends the name and key hashes hashed with SHA1; my
> resonse does the hashes with SHA256.
> 
> The result in debug mode is:
> 
> Wed Jan 11 03:56:13 2017 : Debug: (54) eap_tls: Starting OCSP Request
> Wed Jan 11 03:56:13 2017 : Debug: (54) eap_tls: ocsp: Using responder
> URL "http://ocsp-test.hosted.eduroam.org:80/ticker/"
> Wed Jan 11 03:56:13 2017 : ERROR: (54) eap_tls: ocsp: No Status found
> Wed Jan 11 03:56:13 2017 : ERROR: (54) eap_tls: ocsp: Certificate has
> been expired/revoked
> 
> The Status sits right there in the response: "Cert Status: good" but for
> some reason FR

  ... OpenSSL...

> won't accept it.
> 
> I believe it would be easy to fix this; calculate the name and key
> hashes for both algos and check if the response matches any one of those.
> 
> I thought I could slap you with RFC6960's section 4.3: "Clients that
> request OCSP services SHALL be capable of processing responses signed
> using RSA with SHA-256 (identified by the sha256WithRSAEncryption OID
> specified in [RFC4055]). "
> 
> but that one only pertains to the signature hash algorithm of the full
> response (which is sha256, and which does not seem to be the issue here).
> 
> So, is all that correct?

  Mostly.

  We don't implement OCSP.  OpenSSL does.  We just call the OpenSSL API.  If it returns "no", there's not a lot we can do.

  Perhaps try upgrading OpenSSL.

  Alan DeKok.