#!/usr/bin/env python3

import hmac
import hashlib
import base64
import argparse

# These values are required to calculate the signature. Do not change them.
DATE = "11111111"
SERVICE = "ses"
MESSAGE = "SendRawEmail"
TERMINAL = "aws4_request"
VERSION = 0x04


def sign(key, msg):
    return hmac.new(key, msg.encode('utf-8'), hashlib.sha256).digest()

def calculate_key(secret_access_key, region):
    signature = sign(("AWS4" + secret_access_key).encode('utf-8'), DATE)
    signature = sign(signature, region)
    signature = sign(signature, SERVICE)
    signature = sign(signature, TERMINAL)
    signature = sign(signature, MESSAGE)
    signature_and_version = bytes([VERSION]) + signature
    smtp_password = base64.b64encode(signature_and_version)
    return smtp_password.decode('utf-8')

def main():
    parser = argparse.ArgumentParser(
        description='Convert a Secret Access Key for an IAM user to an SMTP password.')
    parser.add_argument(
        'secret', help='The Secret Access Key to convert.')
    parser.add_argument(
        'region',
        help='The AWS Region where the SMTP password will be used.')
    args = parser.parse_args()
    print(calculate_key(args.secret, args.region))

if __name__ == '__main__':
    main()