Inclusion of OSSL_LIB_CTX* in hybrid generation procedures

[RodriM11]

Hi! I wanted to propose a minor (but I think interesting) feature for the key generation, encapsulation and signature procedures, to ensure that the OSSL_LIB_CTX* context in which the provider is loaded is used within these three procedures. This would help ensure, for example, that whatever DRBG construction loaded into it is also used in these three probabilistic procedures (for the classical parts).

I am aware that an equivalent solution would be to ensure that the default NULL OSSL_LIB_CTX* context is established with the same DRBG as the libctx in which the provider is loaded, but this can be somewhat undesirable depending upon use, situation, etc... Meanwhile, I believe that this solution is fairly simple:

• For Key Generation, the OSSL_LIB_CTX *libctx context received as parameter to the procedure ''oqsx_key_new'' would need to be propagated to the procedures oqsx_hybsig_init and oqshybkem_init_ecp/oqshybkem_init_ecx, for this context to then be used in the associated EVP_PKEY_CTX_new (to be modified to EVP_PKEY_CTX_new_from_pkey).
• For Encapsulation, oqs_evp_kem_encaps_keyslot should be modified, to employ the OSSL_LIB_CTX* context inside pkemctx in the procedure EVP_PKEY_CTX_new_from_pkey (instead of EVP_PKEY_CTX_new).
• For Sign, the procedure oqs_sig_sign should be expanded in a similar way to include the same libctx where appropiate.

Thanks in advance.

[baentsch]

Thanks for the proposal @RodriM11 ! This sounds like a sensible enhancement. Would you like to take a swing at contributing this via PR?

[RodriM11]

Yes, sure. I will write it and PR it in the following days. Thanks in advance!