EVP_PKEY_fromdata_init returns unsupported.

[William Roberts]

On Mon, Feb 28, 2022 at 2:59 AM Matt Caswell <matt at openssl.org> wrote:
>
>
>
> On 25/02/2022 22:07, William Roberts wrote:
> > Hello,
> >
> > In openssl 3.0.1 the following code hits the ctx->keymgt is null check
> > and thus returns -2
> > in pmeth_gn.c:
> > static int fromdata_init(EVP_PKEY_CTX *ctx, int operation)
> > {
> >      if (ctx == NULL || ctx->keytype == NULL)
> >          goto not_supported;
> >
> >      evp_pkey_ctx_free_old_ops(ctx);
> >      if (ctx->keymgmt == NULL)
> >          goto not_supported;
> >
> > The callpath comes in from EVP_PKEY_fromdata_init:
> >
> > libctx = OSSL_LIB_CTX_new()
> > genctx = EVP_PKEY_CTX_new_from_name(libctx, "RSA", NULL);
>
>
> My guess is EVP_PKEY_CTX_new_from_name() is finding a default engine
> implementation for RSA. You might like to step through
> EVP_PKEY_CTX_new_from_name in the debugger (actually int_ctx_new in
> crypto/evp/pmeth_lib.c) and see if the "e" variable ever gets associated
> with an engine.
>

Yes variable e does indeed get associated with the "pkcs11 engine"

> If an engine is being found then the EVP_PKEY_CTX will use that engine
> implementation for all subsequent RSA operations. EVP_PKEY_fromdata will
> only work with provider based implementations (we should make that
> explicit in the documentation) - hence it will fail.
>

Is there any way I can build an RSA or EC public key and encrypt with that and
not go to a provider?

> Matt
>
>
>
> > int rc = EVP_PKEY_fromdata_init(genctx);
> >
> > I have no idea why it returns unsupported... any ideas?
> > I also tried replacing EVP_PKEY_CTX_new_from_name  with
> > EVP_PKEY_CTX_new_id, same error.
> >
> > Thanks,
> > Bill
> >