Add support for creating an IAM role

This adds `stacker_blueprints.iam_roles.IAMRole`, which creates an IAM
Role, accepting a list of principals allowed to assume the role, and
attached policies. It's expected that this would be used with an
existing user and policy.

Author: aengelas

stacker_blueprints/iam_roles.py

@@ -8,7 +8,8 @@
     iam,
 )
 
-from awacs.aws import Policy
+from awacs.aws import Policy, Statement, Principal
+from awacs import sts
 from awacs.helpers.trust import (
     get_default_assumerole_policy,
     get_lambda_assumerole_policy
@@ -227,3 +228,73 @@ def create_template(self):
             self.create_lambda_role(role)
 
         self.create_policy()
+
+
+class IAMRole(Blueprint):
+    """
+    Blueprint to create an IAM role.
+
+    - class_path: stacker_blueprints.iam_roles.IAMRole
+      name: my-role
+        variables:
+          Name: myRole
+          Path: /
+          AttachedPolicies:
+            - arn:aws:iam::aws:policy/CloudWatchLogsFullAccess
+          AssumeRole:
+            - arn:aws:iam::123456789012:user/JohnDoe
+    """
+    VARIABLES = {
+        "Name": {
+            "type": str,
+            "description": "The name of the role",
+            "default": "Role",
+        },
+        "Path": {
+            "type": str,
+            "description": "Provide the path",
+            "default": "/",
+        },
+        "AttachedPolicies": {
+            "type": list,
+            "description": "List of ARNs of policies to attach",
+            "default": [],
+        },
+        "AssumeRole": {
+            "type": list,
+            "description": "List of ARNs of entities allowed to assume this role",
+            "default": [],
+        },
+    }
+
+    def create_template(self):
+        variables = self.get_variables()
+
+        ar_policy = Policy(
+            Statement=[
+                Statement(
+                    Effect='Allow',
+                    Principal=Principal("AWS", p),
+                    Action=[
+                        sts.AssumeRole,
+                    ],
+                ) for p in variables['AssumeRole']
+            ]
+        )
+
+        role = self.template.add_resource(
+            iam.Role(
+                variables['Name'],
+                Path=variables['Path'],
+                ManagedPolicyArns=variables['AttachedPolicies'],
+                AssumeRolePolicyDocument=ar_policy,
+            )
+        )
+
+        self.template.add_output(
+            Output("RoleName", Value=Ref(role))
+        )
+
+        self.template.add_output(
+            Output("RoleArn", Value=GetAtt(role.title, "Arn"))
+        )

tests/fixtures/blueprints/test_iam_roles_iam_role.json

@@ -0,0 +1,41 @@
+{
+    "Outputs": {
+        "RoleArn": {
+            "Value": {
+                "Fn::GetAtt": [
+                    "Role", 
+                    "Arn"
+                ]
+            }
+        }, 
+        "RoleName": {
+            "Value": {
+                "Ref": "Role"
+            }
+        }
+    }, 
+    "Resources": {
+        "Role": {
+            "Properties": {
+                "AssumeRolePolicyDocument": {
+                    "Statement": [
+                        {
+                            "Action": [
+                                "sts:AssumeRole"
+                            ], 
+                            "Effect": "Allow", 
+                            "Principal": {
+                                "AWS": "arn:aws:iam::123456789012:user/JohnDoe"
+                            }
+                        }
+                    ]
+                }, 
+                "ManagedPolicyArns": [
+                    "arn:aws:iam::aws:policy/CloudWatchLogsFullAccess"
+                ], 
+                "Path": "/"
+            }, 
+            "Type": "AWS::IAM::Role"
+        }
+    }
+}

tests/fixtures/blueprints/test_iam_roles_iam_role_name.json

@@ -0,0 +1,41 @@
+{
+    "Outputs": {
+        "RoleArn": {
+            "Value": {
+                "Fn::GetAtt": [
+                    "myRole", 
+                    "Arn"
+                ]
+            }
+        }, 
+        "RoleName": {
+            "Value": {
+                "Ref": "myRole"
+            }
+        }
+    }, 
+    "Resources": {
+        "myRole": {
+            "Properties": {
+                "AssumeRolePolicyDocument": {
+                    "Statement": [
+                        {
+                            "Action": [
+                                "sts:AssumeRole"
+                            ], 
+                            "Effect": "Allow", 
+                            "Principal": {
+                                "AWS": "arn:aws:iam::123456789012:user/JohnDoe"
+                            }
+                        }
+                    ]
+                }, 
+                "ManagedPolicyArns": [
+                    "arn:aws:iam::aws:policy/CloudWatchLogsFullAccess"
+                ], 
+                "Path": "/"
+            }, 
+            "Type": "AWS::IAM::Role"
+        }
+    }
+}

tests/test_iam_roles.py

@@ -88,3 +88,37 @@ def test_role_name(self):
         blueprint.resolve_variables(self.generate_variables())
         blueprint.create_template()
         self.assertRenderedBlueprint(blueprint)
+
+
+class TestIamRoleBlueprint(TestIamRolesCommon):
+
+    def test_role(self):
+        self.common_variables = {
+            'Path': '/',
+            'AttachedPolicies': [
+                'arn:aws:iam::aws:policy/CloudWatchLogsFullAccess',
+            ],
+            'AssumeRole': [
+                'arn:aws:iam::123456789012:user/JohnDoe',
+            ],
+        }
+        blueprint = self.create_blueprint('test_iam_roles_iam_role', class_name=iam_roles.IAMRole)
+        blueprint.resolve_variables(self.generate_variables())
+        blueprint.create_template()
+        self.assertRenderedBlueprint(blueprint)
+
+    def test_role_name(self):
+        self.common_variables = {
+            'Name': 'myRole',
+            'Path': '/',
+            'AttachedPolicies': [
+                'arn:aws:iam::aws:policy/CloudWatchLogsFullAccess',
+            ],
+            'AssumeRole': [
+                'arn:aws:iam::123456789012:user/JohnDoe',
+            ],
+        }
+        blueprint = self.create_blueprint('test_iam_roles_iam_role_name', class_name=iam_roles.IAMRole)
+        blueprint.resolve_variables(self.generate_variables())
+        blueprint.create_template()
+        self.assertRenderedBlueprint(blueprint)