How do I check that the key is legacy

[beldmit]

For non-legacy keys it's safe to make _todata/_fromdata conversions. For engine-backed keys, it still can be done, but the resulting key will not be operable. How do I distinguish that the key is a legacy one (at least for RSA/EC)?

[mattcaswell]

EVP_PKEY_get0_provider() will return a reference to a provider associated with the key or NULL if there is none (implying it is blank or legacy).

[beldmit]

OK. And what about the legacy structs - RSA/EC?

[mattcaswell]

Not sure I understand the question. What about them?

[beldmit]

I have a legacy application that creates RSA/EC structs. I want to check if a particular struct is suitable to creating a EVP_PKEY via legacy accessors and EVP_PKEY_fromdata or not