[Pcsclite-muscle] Directly using RSA key of a smartcard

[David Woodhouse]

On Thu, 2023-06-22 at 11:10 +0100, David Woodhouse wrote:
> 
>  $ echo Test | openssl dgst -sha256 -sign 'pkcs11:manufacturer=piv_II;id=%04' -engine pkcs11 -keyform engine  > signature.bin
>  $ echo Test openssl dgst -sha256 -verify pubkey.pem -signature signature.bin
> Verified OK

Someone on StackExchange pointed out that this is *signature* not
encryption, and isn't quite what you asked for.

He's correct; I was being a bit lazy because those command lines
happened to be in my bash history anyway from what I was playing with
this week. And encryption *ought* to be similar.... except...

Some keys+tokens won't do the raw "decrypt" RSA operation for you,
because it exposes them to oracle attacks and leaking the key.

Even though mathematically, the low-level RSA signature *is* a
decryption operation, some keys will only do that decryption if they
*also* do the "padding" operation for themselves. And that might be the
case for *all* of the key slots in the Yubikey PIV; I don't see that
*any* of them have the CKA_DECRYPT flag which indicates that they'll do
a raw decrypt for you?

Most of my point about "this stuff should just work through PKCs#11"
remains true, but you *might* need something other than a Yubikey?
Folks on this list might know better about what the PIV will do with
its different key slots? And I'm using OpenSC not the Yubico ykcs11
module; maybe that behaves differently? 

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