I have a ECDSA private key, which needs to be converted to PKCS8 DER. For now I use a Python script, but I want to use bash with openssl or node.js for further AWS KMS import.

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import ec
from dotenv import load_dotenv

import os

private_key_hex  = "******"

def load_private_key_from_hex(private_key_hex):
    # Convert the hex string to bytes
    private_key_bytes = bytes.fromhex(private_key_hex)

    # Generate the private key object from the bytes
    private_key = ec.derive_private_key(
        int.from_bytes(private_key_bytes, byteorder='big'), 
        ec.SECP256K1(), 
        default_backend()
    )
    return private_key

def convert_key_to_der_format(private_key):
    der_private_key = private_key.private_bytes(
        encoding=serialization.Encoding.DER,
        format=serialization.PrivateFormat.PKCS8,
        encryption_algorithm=serialization.NoEncryption()
    )
    return der_private_key


private_key = load_private_key_from_hex(private_key_hex)
der_private_key = convert_key_to_der_format(private_key)

with open("...", "wb") as der_file:
    der_file.write(der_private_key)