chore: added keyring examples (kms_rsa, multi, discovery)

examples/src/keyrings/aws_kms_discovery_keyring_example.py

@@ -0,0 +1,233 @@
+# Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""
+This example sets up the AWS KMS Discovery Keyring
+
+AWS KMS discovery keyring is an AWS KMS keyring that doesn't specify any wrapping keys.
+
+The AWS Encryption SDK provides a standard AWS KMS discovery keyring and a discovery keyring
+for AWS KMS multi-Region keys. For information about using multi-Region keys with the
+AWS Encryption SDK, see
+https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/configure.html#config-mrks
+
+Because it doesn't specify any wrapping keys, a discovery keyring can't encrypt data.
+If you use a discovery keyring to encrypt data, alone or in a multi-keyring, the encrypt
+operation fails.
+
+When decrypting, a discovery keyring allows the AWS Encryption SDK to ask AWS KMS to decrypt
+any encrypted data key by using the AWS KMS key that encrypted it, regardless of who owns or
+has access to that AWS KMS key. The call succeeds only when the caller has kms:Decrypt
+permission on the AWS KMS key.
+
+This example creates a KMS Keyring and then encrypts a custom input EXAMPLE_DATA
+with an encryption context. This encrypted ciphertext is then decrypted using the Discovery keyring.
+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
+4. Decryption is only possible if the Discovery Keyring contains the correct AWS Account ID's to
+    which the KMS key used for encryption belongs
+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 Discovery keyrings, see
+https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/use-kms-keyring.html#kms-keyring-discovery
+"""
+import sys
+
+import boto3
+from aws_cryptographic_materialproviders.mpl import AwsCryptographicMaterialProviders
+from aws_cryptographic_materialproviders.mpl.config import MaterialProvidersConfig
+from aws_cryptographic_materialproviders.mpl.models import (
+    CreateAwsKmsDiscoveryKeyringInput,
+    CreateAwsKmsKeyringInput,
+    DiscoveryFilter,
+)
+from aws_cryptographic_materialproviders.mpl.references import IKeyring
+from typing import Dict
+
+import aws_encryption_sdk
+from aws_encryption_sdk import CommitmentPolicy
+from aws_encryption_sdk.exceptions import AWSEncryptionSDKClientError
+
+# TODO-MPL: Remove this as part of removing PYTHONPATH hacks.
+MODULE_ROOT_DIR = '/'.join(__file__.split("/")[:-1])
+
+sys.path.append(MODULE_ROOT_DIR)
+
+EXAMPLE_DATA: bytes = b"Hello World"
+
+
+def get_account_id_from_kms_key_id(kms_key_id: str) -> str:
+    """
+    Get the AWS Account ID from the KMS Key ID.
+
+    Usage: get_account_id_from_kms_key_id(kms_key_id)
+    :param kms_key_id: KMS Key identifier for the KMS key you want to use
+    :type kms_key_id: string
+    :return: AWS Account ID
+    :rtype: string
+    """
+    return kms_key_id.split(":")[4]
+
+
+def get_aws_region_from_kms_key_id(kms_key_id: str) -> str:
+    """
+    Get the AWS Region from the KMS Key ID.
+
+    Usage: get_aws_region_from_kms_key_id(kms_key_id)
+    :param kms_key_id: KMS Key identifier for the KMS key you want to use
+    :type kms_key_id: string
+    :return: AWS Region
+    :rtype: string
+    """
+    return kms_key_id.split(":")[3]
+
+
+def encrypt_and_decrypt_with_keyring(
+    kms_key_id: str
+):
+    """Demonstrate an encrypt/decrypt cycle using an AWS KMS Discovery Keyring.
+
+    Usage: encrypt_and_decrypt_with_keyring(kms_key_id)
+    :param kms_key_id: KMS Key identifier for the KMS key you want to use for creating
+    the kms_keyring used for encryption
+    :type kms_key_id: 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_REQUIRE_DECRYPT
+    )
+
+    # 2. Create a boto3 client for KMS.
+
+    # Get the AWS Region from the KMS Key ID.
+    region_name = get_aws_region_from_kms_key_id(kms_key_id)
+
+    kms_client = boto3.client('kms', region_name=region_name)
+
+    # 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 the keyring that determines how your data keys are protected.
+    # Although this example highlights Discovery keyrings, Discovery keyrings cannot
+    # be used to encrypt, so for encryption we create a KMS keyring without discovery mode.
+    mat_prov: AwsCryptographicMaterialProviders = AwsCryptographicMaterialProviders(
+        config=MaterialProvidersConfig()
+    )
+
+    kms_keyring_input: CreateAwsKmsKeyringInput = CreateAwsKmsKeyringInput(
+        kms_key_id=kms_key_id,
+        kms_client=kms_client
+    )
+
+    encrypt_kms_keyring: IKeyring = mat_prov.create_aws_kms_keyring(
+        input=kms_keyring_input
+    )
+
+    # 5. Encrypt the data with the encryptionContext
+    ciphertext, _ = client.encrypt(
+        source=EXAMPLE_DATA,
+        keyring=encrypt_kms_keyring,
+        encryption_context=encryption_context
+    )
+
+    # 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. Now create a Discovery keyring to use for decryption. We'll add a discovery filter
+    # so that we limit the set of ciphertexts we are willing to decrypt to only ones
+    # created by KMS keys in our account and partition.
+
+    # Get the AWS Account ID from the KMS Key ID to use in the discovery filter
+    aws_account_id: str = get_account_id_from_kms_key_id(kms_key_id=kms_key_id)
+
+    discovery_keyring_input: CreateAwsKmsDiscoveryKeyringInput = CreateAwsKmsDiscoveryKeyringInput(
+        kms_client=kms_client,
+        discovery_filter=DiscoveryFilter(
+            account_ids=[aws_account_id],
+            partition="aws"
+        )
+    )
+
+    discovery_keyring: IKeyring = mat_prov.create_aws_kms_discovery_keyring(
+        input=discovery_keyring_input
+    )
+
+    # 8. Decrypt your encrypted data using the discovery keyring.
+    # On Decrypt, the header of the encrypted message (ciphertext) will be parsed.
+    # The header contains the Encrypted Data Keys (EDKs), which, if the EDK
+    # was encrypted by a KMS Keyring, includes the KMS Key ARN.
+    # The Discovery Keyring filters these EDKs for
+    # EDKs encrypted by Single Region OR Multi Region KMS Keys.
+    # If a Discovery Filter is present, these KMS Keys must belong
+    # to an AWS Account ID in the discovery filter's AccountIds and
+    # must be from the discovery filter's partition.
+    # Finally, KMS is called to decrypt each filtered EDK until an EDK is
+    # successfully decrypted. The resulting data key is used to decrypt the
+    # ciphertext's message.
+    # If all calls to KMS fail, the decryption fails.
+    plaintext_bytes, dec_header = client.decrypt(
+        source=ciphertext,
+        keyring=discovery_keyring
+    )
+
+    # 9. 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"
+
+    # 10. 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
+
+    # 11. Demonstrate that if a discovery keyring (Bob's) doesn't have the correct AWS Account ID's,
+    # the decrypt will fail with an error message
+    # Note that this assumes Account ID used here ('888888888888') is different than the one used
+    # during encryption
+    discovery_keyring_input_bob: CreateAwsKmsDiscoveryKeyringInput = \
+        CreateAwsKmsDiscoveryKeyringInput(
+            kms_client=kms_client,
+            discovery_filter=DiscoveryFilter(
+                account_ids=["888888888888"],
+                partition="aws"
+            )
+        )
+
+    discovery_keyring_bob: IKeyring = mat_prov.create_aws_kms_discovery_keyring(
+        input=discovery_keyring_input_bob
+    )
+
+    # Decrypt the ciphertext using Bob's discovery keyring which doesn't contain the required
+    # Account ID's for the KMS keyring used for encryption.
+    # This should throw an AWSEncryptionSDKClientError exception
+    try:
+        plaintext_bytes, _ = client.decrypt(
+            source=ciphertext,
+            keyring=discovery_keyring_bob
+        )
+
+        raise AssertionError("Decrypt using discovery keyring with wrong AWS Account ID should"
+                             + "raise AWSEncryptionSDKClientError")
+    except AWSEncryptionSDKClientError:
+        pass