aws_kms_rsa_keyring_example.py

# Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0
"""
This example sets up the AWS KMS RSA Keyring

This example creates a KMS RSA Keyring and then encrypts a custom input
EXAMPLE_DATA with an encryption context. This example also includes some sanity checks for
demonstration:
1. Ciphertext and plaintext data are not the same
2. Encryption context is correct in the decrypted message header
3. Decrypted plaintext value matches EXAMPLE_DATA
These sanity checks are for demonstration in the example only. You do not need these in your code.

# For more information on how to use KMS keyrings, see
# https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/use-kms-keyring.html
"""

import boto3
from aws_cryptographic_materialproviders.mpl import AwsCryptographicMaterialProviders
from aws_cryptographic_materialproviders.mpl.config import MaterialProvidersConfig
from aws_cryptographic_materialproviders.mpl.models import CreateAwsKmsRsaKeyringInput
from aws_cryptographic_materialproviders.mpl.references import IKeyring
from typing import Dict  # noqa pylint: disable=wrong-import-order

import aws_encryption_sdk
from aws_encryption_sdk import CommitmentPolicy
from aws_encryption_sdk.identifiers import AlgorithmSuite

EXAMPLE_DATA: bytes = b"Hello World"


def encrypt_and_decrypt_with_keyring(
    kms_rsa_key_id: str,
    public_key: str
):
    """Demonstrate an encrypt/decrypt cycle using an AWS KMS RSA keyring.

    Usage: encrypt_and_decrypt_with_keyring(kms_rsa_key_id, public_key)
    :param kms_rsa_key_id: KMS RSA Key identifier for the KMS RSA key you want to use
    :type kms_rsa_key_id: string
    :param public_key: public key you want to use
    :type public_key: string

    For more information on KMS Key identifiers, see
    https://docs.aws.amazon.com/kms/latest/developerguide/concepts.html#key-id
    """
    # 1. Instantiate the encryption SDK client.
    # This builds the client with the REQUIRE_ENCRYPT_REQUIRE_DECRYPT commitment policy,
    # which enforces that this client only encrypts using committing algorithm suites and enforces
    # that this client will only decrypt encrypted messages that were created with a committing
    # algorithm suite.
    # This is the default commitment policy if you were to build the client as
    # `client = aws_encryption_sdk.EncryptionSDKClient()`.
    client = aws_encryption_sdk.EncryptionSDKClient(
        commitment_policy=CommitmentPolicy.REQUIRE_ENCRYPT_ALLOW_DECRYPT
    )

    # 2. Create a boto3 client for KMS.
    kms_client = boto3.client('kms', region_name="us-west-2")

    # 3. Create encryption context.
    # Remember that your encryption context is NOT SECRET.
    # For more information, see
    # https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/concepts.html#encryption-context
    encryption_context: Dict[str, str] = {
        "encryption": "context",
        "is not": "secret",
        "but adds": "useful metadata",
        "that can help you": "be confident that",
        "the data you are handling": "is what you think it is",
    }

    # 4. Create a KMS RSA keyring
    mat_prov: AwsCryptographicMaterialProviders = AwsCryptographicMaterialProviders(
        config=MaterialProvidersConfig()
    )

    # Create the AWS KMS RSA keyring input
    # For more information on the allowed encryption algorithms, please see
    # https://docs.aws.amazon.com/kms/latest/developerguide/asymmetric-key-specs.html#key-spec-rsa
    keyring_input: CreateAwsKmsRsaKeyringInput = CreateAwsKmsRsaKeyringInput(
        public_key=public_key,
        kms_key_id=kms_rsa_key_id,
        encryption_algorithm="RSAES_OAEP_SHA_256",
        kms_client=kms_client
    )

    kms_rsa_keyring: IKeyring = mat_prov.create_aws_kms_rsa_keyring(
        input=keyring_input
    )

    # 5. Encrypt the data with the encryptionContext
    ciphertext, _ = client.encrypt(
        source=EXAMPLE_DATA,
        keyring=kms_rsa_keyring,
        encryption_context=encryption_context,
        algorithm=AlgorithmSuite.AES_256_GCM_HKDF_SHA512_COMMIT_KEY
    )

    # 6. Demonstrate that the ciphertext and plaintext are different.
    # (This is an example for demonstration; you do not need to do this in your own code.)
    assert ciphertext != EXAMPLE_DATA, \
        "Ciphertext and plaintext data are the same. Invalid encryption"

    # 7. Decrypt your encrypted data using the same keyring you used on encrypt.
    plaintext_bytes, dec_header = client.decrypt(
        source=ciphertext,
        keyring=kms_rsa_keyring
    )

    # 8. Demonstrate that the encryption context is correct in the decrypted message header
    # (This is an example for demonstration; you do not need to do this in your own code.)
    for k, v in encryption_context.items():
        assert v == dec_header.encryption_context[k], \
            "Encryption context does not match expected values"

    # 9. Demonstrate that the decrypted plaintext is identical to the original plaintext.
    # (This is an example for demonstration; you do not need to do this in your own code.)
    assert plaintext_bytes == EXAMPLE_DATA, \
        "Decrypted plaintext should be identical to the original plaintext. Invalid decryption"