# Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.

#

# Licensed under the Apache License, Version 2.0 (the "License"). You

# may not use this file except in compliance with the License. A copy of

# the License is located at

#

# http://aws.amazon.com/apache2.0/

#

# or in the "license" file accompanying this file. This file is

# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF

# ANY KIND, either express or implied. See the License for the specific

# language governing permissions and limitations under the License.

"""Example showing how to disable commitment.

Note: This configuration should only be used as part of a migration from version 1.x to 2.x, or for advanced users

with specialized requirements. We recommend that AWS Encryption SDK users enable commitment whenever possible.

"""

import aws_encryption_sdk

from aws_encryption_sdk import CommitmentPolicy

def encrypt_decrypt(key_arn, source_plaintext, botocore_session=None):

"""Encrypts and then decrypts a string under one KMS customer master key (CMK).

:param str key_arn: Amazon Resource Name (ARN) of the KMS CMK

:param bytes source_plaintext: Data to encrypt

:param botocore_session: existing botocore session instance

:type botocore_session: botocore.session.Session

"""

kwargs = dict(key_ids=[key_arn])

if botocore_session is not None:

kwargs["botocore_session"] = botocore_session

# Set up an encryption client with an explicit commitment policy disallowing encryption with algorithms that

# provide commitment

client = aws_encryption_sdk.EncryptionSDKClient(commitment_policy=CommitmentPolicy.FORBID_ENCRYPT_ALLOW_DECRYPT)

# Create master key provider using the ARN of the key and the session (botocore_session)

kms_key_provider = aws_encryption_sdk.StrictAwsKmsMasterKeyProvider(**kwargs)

# Encrypt the plaintext using the AWS Encryption SDK. It returns the encrypted message and the header. Note: in

# order for decrypt to succeed, the key_ids value must be the key ARN of the CMK.

ciphertext, encrypted_message_header = client.encrypt(source=source_plaintext, key_provider=kms_key_provider)

# Decrypt the encrypted message using the AWS Encryption SDK. It returns the decrypted message and the header

plaintext, decrypted_message_header = client.decrypt(source=ciphertext, key_provider=kms_key_provider)

# Verify that the original message and the decrypted message are the same

assert source_plaintext == plaintext

# Verify that the encryption context of the encrypted message and decrypted message match

assert all(

pair in encrypted_message_header.encryption_context.items()

for pair in decrypted_message_header.encryption_context.items()

)