aws_kms_encrypted_resource.py

# Copyright 2018 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 use of AWS KMS CMP with EncryptedResource."""
import boto3
from boto3.dynamodb.types import Binary

from dynamodb_encryption_sdk.encrypted.resource import EncryptedResource
from dynamodb_encryption_sdk.identifiers import CryptoAction
from dynamodb_encryption_sdk.material_providers.aws_kms import AwsKmsCryptographicMaterialsProvider
from dynamodb_encryption_sdk.structures import AttributeActions


def encrypt_batch_items(table_name, aws_cmk_id):
    """Demonstrate use of EncryptedResource to transparently encrypt multiple items in a batch request."""
    index_keys = [
        {"partition_attribute": "is this", "sort_attribute": 55},
        {"partition_attribute": "is this", "sort_attribute": 56},
        {"partition_attribute": "is this", "sort_attribute": 57},
        {"partition_attribute": "another", "sort_attribute": 55},
    ]
    plaintext_additional_attributes = {
        "example": "data",
        "some numbers": 99,
        "and some binary": Binary(b"\x00\x01\x02"),
        "leave me": "alone",  # We want to ignore this attribute
    }
    plaintext_items = []
    for key in index_keys:
        _attributes = key.copy()
        _attributes.update(plaintext_additional_attributes)
        plaintext_items.append(_attributes)

    # Collect all of the attributes that will be encrypted (used later).
    encrypted_attributes = set(plaintext_additional_attributes.keys())
    encrypted_attributes.remove("leave me")
    # Collect all of the attributes that will not be encrypted (used later).
    unencrypted_attributes = set(index_keys[0].keys())
    unencrypted_attributes.add("leave me")

    # Create a normal service resource.
    resource = boto3.resource("dynamodb")
    # Create a crypto materials provider using the specified AWS KMS key.
    aws_kms_cmp = AwsKmsCryptographicMaterialsProvider(key_id=aws_cmk_id)
    # Create attribute actions that tells the encrypted resource to encrypt all attributes except one.
    actions = AttributeActions(
        default_action=CryptoAction.ENCRYPT_AND_SIGN, attribute_actions={"leave me": CryptoAction.DO_NOTHING}
    )
    # Use these objects to create an encrypted service resource.
    encrypted_resource = EncryptedResource(resource=resource, materials_provider=aws_kms_cmp, attribute_actions=actions)

    # Put the items to the table, using the encrypted service resource to transparently encrypt them.
    encrypted_resource.batch_write_item(
        RequestItems={table_name: [{"PutRequest": {"Item": item}} for item in plaintext_items]}
    )

    # Get the encrypted item using the standard service resource.
    encrypted_items = resource.batch_get_item(  # generated code confuse pylint: disable=no-member
        RequestItems={table_name: {"Keys": index_keys}}
    )["Responses"][table_name]

    # Get the item using the encrypted service resource, transparently decyrpting it.
    decrypted_items = encrypted_resource.batch_get_item(RequestItems={table_name: {"Keys": index_keys}})["Responses"][
        table_name
    ]

    def _select_index_from_item(item):
        """Find the index keys that match this item."""
        for index in index_keys:
            if all(item[key] == value for key, value in index.items()):
                return index

        raise Exception("Index key not found in item.")

    def _select_item_from_index(index, all_items):
        """Find the item that matches these index keys."""
        for item in all_items:
            if all(item[key] == value for key, value in index.items()):
                return item

        raise Exception("Index key not found in item.")

    for encrypted_item in encrypted_items:
        key = _select_index_from_item(encrypted_item)
        plaintext_item = _select_item_from_index(key, plaintext_items)
        decrypted_item = _select_item_from_index(key, decrypted_items)

        # Verify that all of the attributes are different in the encrypted item
        for name in encrypted_attributes:
            assert encrypted_item[name] != plaintext_item[name]
            assert decrypted_item[name] == plaintext_item[name]

        # Verify that all of the attributes that should not be encrypted were not.
        for name in unencrypted_attributes:
            assert decrypted_item[name] == encrypted_item[name] == plaintext_item[name]

    # Clean up the item
    encrypted_resource.batch_write_item(
        RequestItems={table_name: [{"DeleteRequest": {"Key": key}} for key in index_keys]}
    )