x5c support?

[JonasKs]

Hi,

I can construct public keys from x5c like this:

import base64

from cryptography.hazmat.backends.openssl.backend import backend
from cryptography.x509 import load_der_x509_certificate

from jose import jwk

x5c_key = "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"
cert_obj = load_der_x509_certificate(base64.b64decode(x5c_key), backend)

x5c_constructed = jwk.construct(cert_obj.public_key(), 'RS256')

But, I cannot use construct without first manually creating the public key. This means, for endpoints that only provide x5c, and not n and e, I have to do this manually.

This works "out of the box":

from jose import jwk

key = {
    "kty": "RSA",
    "use": "sig",
    "kid": "nOo3ZDrODXEK1jKWhXslHR_KXEg",
    "x5t": "nOo3ZDrODXEK1jKWhXslHR_KXEg",
    "n": "oaLLT9hkcSj2tGfZsjbu7Xz1Krs0qEicXPmEsJKOBQHauZ_kRM1HdEkgOJbUznUspE6xOuOSXjlzErqBxXAu4SCvcvVOCYG2v9G3-uIrLF5dstD0sYHBo1VomtKxzF90Vslrkn6rNQgUGIWgvuQTxm1uRklYFPEcTIRw0LnYknzJ06GC9ljKR617wABVrZNkBuDgQKj37qcyxoaxIGdxEcmVFZXJyrxDgdXh9owRmZn6LIJlGjZ9m59emfuwnBnsIQG7DirJwe9SXrLXnexRQWqyzCdkYaOqkpKrsjuxUj2-MHX31FqsdpJJsOAvYXGOYBKJRjhGrGdONVrZdUdTBQ",
    "e": "AQAB",
}
modulus_exponent_constructed = jwk.construct(key, "RS256")

Comparing them is the same:

x5c_constructed.to_dict() == modulus_exponent_constructed.to_dict()

Would you consider adding support for loading of x5c keys?