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AWS KMS + Python Cryptography using Fernet
#!/usr/bin/env python
"""
kmsencrypt.py
AWS kms + python Cryptography library file encrypt and decrypt
This will perform a file encryption and decryption using AWS KMS for generating a data key
rather than using the Fernet generate_key function.
Assumes that AWS access key, secret or token have been setup outside using credentials file or envvars
!! WARNING - I am not a security expert so use at your own risk !!
"""
import sys
import base64
import boto3
from cryptography.fernet import Fernet
KEY_ID='alias/my_key' # <- place you kms keyid or alias here
def main():
# get a data key from kms
kms_client = boto3.client('kms')
data_key_dict = kms_client.generate_data_key(
KeyId=KEY_ID, KeySpec='AES_256')
# get the components from kms response
encrypted_key = base64.b64encode(data_key_dict['CiphertextBlob'])
master_key_id = data_key_dict['KeyId']
plain_key = base64.b64encode(data_key_dict['Plaintext'])
# encrypt file with data key using cryptography.fernet library
with open("./data.txt", mode='rb') as data_fh:
cipher = Fernet(plain_key)
encrypted_data_content = cipher.encrypt(data_fh.read())
# remove sensitive variables
del plain_key, cipher, data_key_dict
# write content to file
with open("./data.txt.enc", mode='wb') as encdata_fh:
encdata_fh.write(encrypted_data_content)
print("Encryped file...")
print("enckey={}\nmasterkey={}".format(encrypted_key, master_key_id))
#---------------------------------------------------------------
# OK, lets decrypt the file. You only have the encrypted key to work with
#---------------------------------------------------------------
# decrypt the data key using aws kms
data_key_dict = kms_client.decrypt(CiphertextBlob=base64.b64decode(encrypted_key))
plain_key = base64.b64encode(data_key_dict['Plaintext'])
# decrypt the file using plan key and fernet
cipher = Fernet(plain_key)
with open("./data.txt.enc", mode='rb') as encdata_fh:
data = cipher.decrypt(encdata_fh.read())
# remove the key variables
del plain_key, cipher, data_key_dict
print("\nDecrypted file...")
print("The content is as follows:\n{}".format(data.decode()))
if __name__ == '__main__':
sys.exit(int(main() or 0))
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