Convert pem to jwk

pem_to_jwk.py

import base64
import math
from typing import Dict, cast

import cryptography.hazmat.backends.openssl.rsa as rsa
from cryptography.hazmat.primitives.serialization import load_der_private_key, load_der_public_key
from jose import jwt

# stolen from https://github.com/mpdavis/python-jose/blob/fccbcf4/tests/test_jws.py#L143
rsa_private_key = """-----BEGIN RSA PRIVATE KEY-----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=
-----END RSA PRIVATE KEY-----"""

rsa_public_key = """-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----"""


def encode_b64url(data: bytes) -> str:
    """
    Base64url Encoding as per https://www.rfc-editor.org/rfc/rfc7515#page-6.

    See also https://github.com/ietf-wg-acme/acme/issues/64#issuecomment-168852757

    Args:
        data (bytes): data

    Returns:
        str: ascii
    """

    # strip base64 padding (ie: = chars)
    return base64.urlsafe_b64encode(data).rstrip(b"=").decode("ascii")


# stolen from https://github.com/certbot/josepy/blob/1cde3c2/src/josepy/jwk.py#L181
def encode_b64url_int(data: int) -> str:
    """Encode int as Base64url

    Args:
        data (int): int

    Returns:
        str: ascii
    """

    length = max(data.bit_length(), 8)  # decoding 0
    length = math.ceil(length / 8)
    return encode_b64url(data.to_bytes(byteorder="big", length=length))


def as_der(pem: str) -> bytes:
    # convert to DER bytes format by stripping off the PEM BEGIN/END markers and decoding
    return base64.b64decode(pem[pem.find("\n") + 1 : pem.rfind("\n")])


def jwk_from_public_key() -> Dict[str, str]:
    key = cast(rsa._RSAPublicKey, load_der_public_key(as_der(rsa_public_key)))
    public_numbers = key.public_numbers()

    return {
        "alg": "RS256",
        "kty": "RSA",
        "n": encode_b64url_int(public_numbers.n),
        "e": encode_b64url_int(public_numbers.e),
        "use": "sig",
        "kid": "skeleton",
    }


def jwk_from_private_key() -> Dict[str, str]:
    key = cast(rsa._RSAPrivateKey, load_der_private_key(as_der(rsa_private_key), password=None))
    public_numbers = key.public_key().public_numbers()

    return {
        "alg": "RS256",
        "kty": "RSA",
        "n": encode_b64url_int(public_numbers.n),
        "e": encode_b64url_int(public_numbers.e),
        "use": "sig",
        "kid": "skeleton",
    }


def test_encode() -> None:
    a = jwt.encode(
        claims={},
        key=rsa_private_key,
        algorithm="RS256",
    )
    jwt.decode(a, jwk_from_private_key())