KMS : Adding support for multi-region keys and implementing replicate_key API. (#5288)

moto/kms/models.py

@@ -1,6 +1,7 @@
 import json
 import os
 from collections import defaultdict
+from copy import copy
 from datetime import datetime, timedelta
 from cryptography.exceptions import InvalidSignature
 from cryptography.hazmat.primitives import hashes
@@ -55,8 +56,10 @@ class Grant(BaseModel):
 
 
 class Key(CloudFormationModel):
-    def __init__(self, policy, key_usage, key_spec, description, region):
-        self.id = generate_key_id()
+    def __init__(
+        self, policy, key_usage, key_spec, description, region, multi_region=False
+    ):
+        self.id = generate_key_id(multi_region)
         self.creation_date = unix_time()
         self.policy = policy or self.generate_default_policy()
         self.key_usage = key_usage
@@ -64,6 +67,7 @@ class Key(CloudFormationModel):
         self.description = description or ""
         self.enabled = True
         self.region = region
+        self.multi_region = multi_region
         self.account_id = get_account_id()
         self.key_rotation_status = False
         self.deletion_date = None
@@ -184,6 +188,7 @@ class Key(CloudFormationModel):
                 "KeyManager": self.key_manager,
                 "KeyUsage": self.key_usage,
                 "KeyState": self.key_state,
+                "MultiRegion": self.multi_region,
                 "Origin": self.origin,
                 "SigningAlgorithms": self.signing_algorithms,
             }
@@ -264,13 +269,31 @@ class KmsBackend(BaseBackend):
             self.add_alias(key.id, alias_name)
             return key.id
 
-    def create_key(self, policy, key_usage, key_spec, description, tags, region):
-        key = Key(policy, key_usage, key_spec, description, region)
+    def create_key(
+        self, policy, key_usage, key_spec, description, tags, region, multi_region=False
+    ):
+        key = Key(policy, key_usage, key_spec, description, region, multi_region)
         self.keys[key.id] = key
         if tags is not None and len(tags) > 0:
             self.tag_resource(key.id, tags)
         return key
 
+    # https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html#mrk-sync-properties
+    # In AWS replicas of a key only share some properties with the original key. Some of those properties get updated
+    # in all replicas automatically if those properties change in the original key. Also, such properties can not be
+    # changed for replicas directly.
+    #
+    # In our implementation with just create a copy of all the properties once without any protection from change,
+    # as the exact implementation is currently infeasible.
+    def replicate_key(self, key_id, replica_region):
+        # Using copy() instead of deepcopy(), as the latter results in exception:
+        #    TypeError: cannot pickle '_cffi_backend.FFI' object
+        # Since we only update top level properties, copy() should suffice.
+        replica_key = copy(self.keys[key_id])
+        replica_key.region = replica_region
+        to_region_backend = kms_backends[replica_region]
+        to_region_backend.keys[replica_key.id] = replica_key
+
     def update_key_description(self, key_id, description):
         key = self.keys[self.get_key_id(key_id)]
         key.description = description

moto/kms/responses.py

@@ -51,8 +51,11 @@ class KmsResponse(BaseResponse):
         - key ARN
         """
         is_arn = key_id.startswith("arn:") and ":key/" in key_id
+        # https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html
+        # "Notice that multi-Region keys have a distinctive key ID that begins with mrk-. You can use the mrk- prefix to
+        # identify MRKs programmatically."
         is_raw_key_id = re.match(
-            r"^[A-F0-9]{8}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{12}$",
+            r"^(mrk-)?[A-F0-9]{8}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{12}$",
             key_id,
             re.IGNORECASE,
         )
@@ -114,12 +117,19 @@ class KmsResponse(BaseResponse):
         )
         description = self.parameters.get("Description")
         tags = self.parameters.get("Tags")
+        multi_region = self.parameters.get("MultiRegion")
 
         key = self.kms_backend.create_key(
-            policy, key_usage, key_spec, description, tags, self.region
+            policy, key_usage, key_spec, description, tags, self.region, multi_region
         )
         return json.dumps(key.to_dict())
 
+    def replicate_key(self):
+        key_id = self.parameters.get("KeyId")
+        self._validate_key_id(key_id)
+        replica_region = self.parameters.get("ReplicaRegion")
+        self.kms_backend.replicate_key(key_id, replica_region)
+
     def update_key_description(self):
         """https://docs.aws.amazon.com/kms/latest/APIReference/API_UpdateKeyDescription.html"""
         key_id = self.parameters.get("KeyId")

moto/kms/utils.py

@@ -45,8 +45,15 @@ RESERVED_ALIASES = [
 ]
 
 
-def generate_key_id():
-    return str(uuid.uuid4())
+def generate_key_id(multi_region=False):
+    key = str(uuid.uuid4())
+    # https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html
+    # "Notice that multi-Region keys have a distinctive key ID that begins with mrk-. You can use the mrk- prefix to
+    # identify MRKs programmatically."
+    if multi_region:
+        key = "mrk-" + key
+
+    return key
 
 
 def generate_data_key(number_of_bytes):

tests/test_kms/test_kms_boto3.py

@@ -120,6 +120,60 @@ def test_create_key():
     key["KeyMetadata"]["SigningAlgorithms"].should.equal(["ECDSA_SHA_512"])
 
 
+@mock_kms
+def test_create_multi_region_key():
+    conn = boto3.client("kms", region_name="us-east-1")
+    key = conn.create_key(
+        Policy="my policy",
+        Description="my key",
+        KeyUsage="ENCRYPT_DECRYPT",
+        MultiRegion=True,
+        Tags=[{"TagKey": "project", "TagValue": "moto"}],
+    )
+
+    key["KeyMetadata"]["KeyId"].should.match("^mrk-")
+    key["KeyMetadata"]["MultiRegion"].should.equal(True)
+
+
+@mock_kms
+def test_non_multi_region_keys_should_not_have_multi_region_properties():
+    conn = boto3.client("kms", region_name="us-east-1")
+    key = conn.create_key(
+        Policy="my policy",
+        Description="my key",
+        KeyUsage="ENCRYPT_DECRYPT",
+        MultiRegion=False,
+        Tags=[{"TagKey": "project", "TagValue": "moto"}],
+    )
+
+    key["KeyMetadata"]["KeyId"].should_not.match("^mrk-")
+    key["KeyMetadata"]["MultiRegion"].should.equal(False)
+
+
+@mock_kms
+def test_replicate_key():
+    region_to_replicate_from = "us-east-1"
+    region_to_replicate_to = "us-west-1"
+    from_region_client = boto3.client("kms", region_name=region_to_replicate_from)
+    to_region_client = boto3.client("kms", region_name=region_to_replicate_to)
+
+    response = from_region_client.create_key(
+        Policy="my policy",
+        Description="my key",
+        KeyUsage="ENCRYPT_DECRYPT",
+        MultiRegion=True,
+        Tags=[{"TagKey": "project", "TagValue": "moto"}],
+    )
+    key_id = response["KeyMetadata"]["KeyId"]
+
+    with pytest.raises(to_region_client.exceptions.NotFoundException):
+        to_region_client.describe_key(KeyId=key_id)
+
+    from_region_client.replicate_key(KeyId=key_id, ReplicaRegion=region_to_replicate_to)
+    to_region_client.describe_key(KeyId=key_id)
+    from_region_client.describe_key(KeyId=key_id)
+
+
 @mock_kms
 def test_create_key_deprecated_master_custom_key_spec():
     conn = boto3.client("kms", region_name="us-east-1")