How about this? https://github.com/dany74q/ctap-keyring-device

This library provides an implementation of a virtual CTAP2 (client-to-authenticator-protocol) device, which uses the keyring library as its backend.

One may use this implementation as a reference for CTAP2-compatible devices, or to use ones host machine as an authenticator, rather than using an external one.

A common use-case would be to use this library as an authenticator for a webauthn flow, storing keys and retrieving assertions on a machine's configured keyring.