cf_signed

import datetime

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
from botocore.signers import CloudFrontSigner

KEY_ID = '*****************'
FILE_URL = 'http://**********.cloudfront.net/s3.png'
expire_date = datetime.datetime(2020, 3, 6, 11, 0, 0)

def rsa_signer(message):
    with open('pk.pem', 'rb') as key_file:
        private_key = serialization.load_pem_private_key(
            key_file.read(),
            password=None,
            backend=default_backend()
        )
    return private_key.sign(message, padding.PKCS1v15(), hashes.SHA1())

def main():
    cloudfront_signer = CloudFrontSigner(KEY_ID, rsa_signer)
    signed_url = cloudfront_signer.generate_presigned_url(
        FILE_URL, date_less_than=expire_date)
    print(signed_url)


if __name__ == "__main__":
    main()