OpenSSL::OCSP::Response's to_der always returns an empty string
The OCSP response object always seems to produce an empty string when to_der is called. The correct response should be a properly encoded DER response similar to the behavior of the other OpenSSL objects that implement to_der.
The problem appears to be on the call to i2d_OCSP_RESPONSE on line 382 (taken from SVN) in ossl_ocsp.c. Instead of passing NULL as the second argument, it should be &p. I have made the change locally and confirmed the output contains what appears to be the correctly formatted DER string. I have also attached the recommended patch. This bug is also present in the latest 1.9 build.