Consume the new, safer Rust PKCS#11 interface into Parsec when it is available

[paulhowardarm]

Summary

Refactor the Parsec PKCS#11 provider so that it consumes the newer, safer types and interfaces in the Rust PKCS#11 library.

Background

The Rust PKCS#11 provider allows Parsec to work with hardware security modules and similar systems that adopt the Oasis PKCS#11 Standard.

The PKCS11 provider makes use of a suite of Rust PKCS11 bindings from the rust-pkcs11 project.

Parsec project contributors have noted some safety improvements that could be made to these interfaces. For details see: mheese/rust-pkcs11#38

There is a fork of the PKCS#11 library created by @joechrisellis that implements the recommended changes to the Rust library: https://github.com/joechrisellis/rust-pkcs11/tree/new-abstraction

This branch reworks the library into a lower-level pkcs11-sys module, and higher-level pkcs11 module, the latter containing a new set of abstractions aimed at consumption into application code.

Once these new interfaces are made available, either by PR into the original project, or by creating a new separate project, it will be possible to refactor the PKCS#11 provider in Parsec to consume these interfaces.

This issue has been raised to track for the future.

[hug-dev]

The work on adding the safe abstraction layer is now located on the new-abstraction branch here.