SSM parameters in cloudformation (AWS::SSM::Parameter::) are not recognized and resolved (#3929)

* Add ssm parsing support for cloudformation stacks

* Start adding unit tests for ssm parameter parsing

* Add tests for code update

* Add tests to parse ssm parameters code

* Fix black lint errors

* Fix bug.

* Need to specify region_name

* region needs to be same

* Use ssm_backends[region] instead of ssm_backend

* StringList -> string

* Linting

* check if servermode tests are on

* Typo

Co-authored-by: Bert Blommers <bblommers@users.noreply.github.com>

moto/cloudformation/parsing.py

@@ -41,6 +41,7 @@ from moto.sagemaker import models as sagemaker_models  # noqa
 from moto.sns import models as sns_models  # noqa
 from moto.sqs import models as sqs_models  # noqa
 from moto.stepfunctions import models as stepfunctions_models  # noqa
+from moto.ssm import models as ssm_models, ssm_backends  # noqa
 
 # End ugly list of imports
 
@@ -516,6 +517,23 @@ class ResourceMap(collections_abc.Mapping):
                 parameter_slot = parameter_slots[key]
 
                 value_type = parameter_slot.get("Type", "String")
+
+                def _parse_ssm_parameter(value, value_type):
+                    # The Value in SSM parameters is the SSM parameter path
+                    # we need to use ssm_backend to retreive the
+                    # actual value from parameter store
+                    parameter = ssm_backends[self._region_name].get_parameter(
+                        value, False
+                    )
+                    actual_value = parameter.value
+
+                    if value_type.find("List") > 0:
+                        return actual_value.split(",")
+
+                    return actual_value
+
+                if value_type.startswith("AWS::SSM::Parameter::"):
+                    value = _parse_ssm_parameter(value, value_type)
                 if value_type == "CommaDelimitedList" or value_type.startswith("List"):
                     value = value.split(",")
 

tests/test_cloudformation/test_stack_parsing.py

@@ -1,4 +1,5 @@
 from __future__ import unicode_literals
+import boto3
 import json
 import yaml
 
@@ -12,6 +13,7 @@ from moto.cloudformation.parsing import (
     parse_condition,
     Export,
 )
+from moto import mock_ssm, settings
 from moto.sqs.models import Queue
 from moto.s3.models import FakeBucket
 from moto.cloudformation.utils import yaml_tag_constructor
@@ -73,6 +75,13 @@ parameters = {
     }
 }
 
+ssm_parameter = {
+    "Parameters": {
+        "SingleParamCfn": {"Type": "AWS::SSM::Parameter::Value<String>"},
+        "ListParamCfn": {"Type": "AWS::SSM::Parameter::Value<List<String>>"},
+    }
+}
+
 split_select_template = {
     "AWSTemplateFormatVersion": "2010-09-09",
     "Resources": {
@@ -143,6 +152,9 @@ get_availability_zones_template = dict(
 )
 
 parameters_template = dict(list(dummy_template.items()) + list(parameters.items()))
+ssm_parameter_template = dict(
+    list(dummy_template.items()) + list(ssm_parameter.items())
+)
 
 dummy_template_json = json.dumps(dummy_template)
 name_type_template_json = json.dumps(name_type_template)
@@ -151,6 +163,7 @@ bad_output_template_json = json.dumps(bad_outputs_template)
 get_attribute_outputs_template_json = json.dumps(get_attribute_outputs_template)
 get_availability_zones_template_json = json.dumps(get_availability_zones_template)
 parameters_template_json = json.dumps(parameters_template)
+ssm_parameter_template_json = json.dumps(ssm_parameter_template)
 split_select_template_json = json.dumps(split_select_template)
 sub_template_json = json.dumps(sub_template)
 export_value_template_json = json.dumps(export_value_template)
@@ -498,3 +511,29 @@ def test_short_form_func_in_yaml_teamplate():
     ]
     for k, v in key_and_expects:
         template_dict.should.have.key(k).which.should.be.equal(v)
+
+
+@mock_ssm
+def test_ssm_parameter_parsing():
+    client = boto3.client("ssm", region_name="us-west-1")
+    client.put_parameter(Name="/path/to/single/param", Value="string", Type="String")
+    client.put_parameter(
+        Name="/path/to/list/param", Value="comma,separated,string", Type="StringList"
+    )
+
+    if not settings.TEST_SERVER_MODE:
+        stack = FakeStack(
+            stack_id="test_id",
+            name="test_stack",
+            template=ssm_parameter_template_json,
+            parameters={
+                "SingleParamCfn": "/path/to/single/param",
+                "ListParamCfn": "/path/to/list/param",
+            },
+            region_name="us-west-1",
+        )
+
+        stack.resource_map.resolved_parameters["SingleParamCfn"].should.equal("string")
+        stack.resource_map.resolved_parameters["ListParamCfn"].should.equal(
+            ["comma", "separated", "string"]
+        )