EVP_PKEY_get_int_param is not getting degree from EC key

[Tomas Mraz]

On Tue, 2022-01-04 at 19:25 +0000, Blumenthal, Uri - 0553 - MITLL
wrote:
> >  > But, considering that the man pages describe C API, wouldn't it
> > be
> >  > nice to mention (even though it may be obvious that a number of
> > order
> >  > 2^384 might not fit into 32 or even 64 bits) that the actual
> > type is
> >  > BIGNUM?
> > 
> >  No, the type is not a BIGNUM. Please read "man OSSL_PARAM" it
> > contains
> >  the information on what types OSSL_PARAM support.
> 
> I did that before playing with and modifying the OP's code.
> Obviously, either I'm too dense to understand it, or it's too dense.
> 
> >  > Also, what should arguments to that C call
> > EVP_PKEY_get_int_param()
> >  > look like to succeed? Do I need to pass a pointer to BN there???
> > 
> >  Please read "man EVP_PKEY_get_int_param".
> 
> See above. Some verbiage, very little clues - especially for somebody
> who doesn't already know how it works.
> 
>    int EVP_PKEY_get_int_param(const EVP_PKEY *pkey, const char
> *key_name,
>                               int *out);
>    EVP_PKEY_get_int_param() retrieves a key pkey integer value *out
> associated with a name of key_name.
> 
> Overall, VERY confusing.
> 
> How does one know (without going through
> EVP_PKEY_gettable_params(EVP_PKEY *pkey) and
> EVP_PKEY_get_params(const EVP_PKEY *pkey, OSSL_PARAM params[])) what
> method to use to retrieve what parameter?

So you're basically asking to put something like - "The parameter most
probably won't fit into unsigned int." - to every such parameter
documented for PKEYs?

-- 
Tomáš Mráz, OpenSSL