Add support for Elliptic Curve keys

[yonran]

Hi. I wanted to add EC support to certbot because I was using lego and wanted to switch my account to certbot. But lego created an account signed using EC instead of RSA so my account was stuck. I would like guidance on what tests I should write and how to run pylint/pydoc.

[bmw]

Hey @yonran. Sorry this has sat around so long.

I would largely base the tests on the tests for the RSA versions of the classes you're adding. You can find these in jwk_test.py and util_test.py.

As for how to run tests, you can install josepy and it's dependencies in a virtual environment by running commands like the following from the root of the repo:

virtualenv venv
source venv/bin/activate
pip install -e .[dev,tests]

After that, you can run tests with tox by running:

tox -e py27

You can replace 27 whichever Python version you want to test against as long as that version of Python is installed on your system.

[jannispinter]

I would love to see this and #45 implemented, as ES256 is a MUST requirement for ACME.

Quoting RFC 8555 Section 6.2 here:

An ACME server MUST implement the "ES256" signature algorithm
[RFC7518] and SHOULD implement the "EdDSA" signature algorithm using
the "Ed25519" variant (indicated by "crv") [RFC8037].

[bmw]

Indeed it is a MUST for an ACME server.

While the small Certbot team would also love to see this implemented, we probably won't be able to get to it for a little while. If you'd like to see it sooner, we'd accept well written PRs for these features.

[bmw]

Now that #51 has landed, can this be closed?

cc @adferrand

[adferrand]

Indeed! This PR was in fact the base on which the actually merged PR has been constructed.

[JamesTheAwesomeDude]

Just to confirm: this only added the SECP- keys, and not X25519?

[adferrand]

Exactly. A work is in progress to add the other elliptic curve keys: #98