[openssl-users] OCSP_BASICRESP_verify() in 1.1.0

[Dave Coombs]

>> If I pass in a STACK_OF(X509) *certs with only the signer's cert in it, and NULL for X509_STORE *st since it won't be used, then I think I should get the desired result, yes, at the cost of ocsp_find_signer(single-entry certs) and the internal creation/destruction of an unused X509_STORE_CTX.  I'd have a small performance hit but it probably wouldn't be too bad.
> 
> Probably the construction of that ctx is in the wrong place. It should
> be later in the function. I can't imagine the ocsp_find_signer() hit is
> too great.

Having tried this, I now see that my copying the structs from ocsp_lcl.h into the external code masked the fact that the external code is getting the signer's cert beforehand by directly accessing OCSP_BASICRESP->certs (and ->tbsResponseData) anyway, effectively doing what ocsp_find_signer() does.  So it is clear that I will need to be rework this, potentially centred around OCSP_basic_verify(), while remaining ignorant of the signer cert.

It would be nice, though, if the API provided a way to get the signer's certificate.  There is OCSP_resp_get0_signature(), but that only returns the bit string.  Comparable functions in other modules (eg: X509_get0_signature(), X509_REQ_get0_signature(), X509_CRL_get0_signature(), CMS_SignerInfo_get0_algs()) provide a way to get any combination of bit string, algorithm, and signer cert.

Cheers,
  -Dave