PoC: Add vendor command for signing an arbitrary SHA256 hash

[rgerganov]

This patch adds new CTAP2 vendor command with command value 0x50. The
command arguments are credentialId and user specified SHA256 hash. It
returns a DER encoded signature of the given hash, using the key
which corresponds to the specified credentialId.

Example request:
{1: <sha256_hash>, 2: {"id": <credential_id>, "type": "public-key"}}

Example response:
{1: <der_signature>}

Issue: #395

[My1]

btw I tried this along with solokeys/solo1-cli#67 and it works, pretty neat idea.

[rgerganov]

Rebased the patch and added support for pinAuth

[My1]

question is on what base we would run pin, basically force if available, or let the user decide some way on creating the credential or whatever

[rgerganov]

question is on what base we would run pin, basically force if available, or let the user decide some way on creating the credential or whatever

I am trying to mimic the semantics of GetAssertion. If there is a PIN set, then platform needs to send pinAuth. Otherwise, only a button press is needed for signing.

[My1]

but get assertion has uv kinda optional as far as I read it in the document, depending on how the options.uv is set and it defaults to false

[My1]

okay considering this:
#395 (comment)
it makes totally sense to force pin if set

[rgerganov]

I have rebased the patch on top of master