[breaking] [feature] aws-iam-instance-profile reuse existing role and remove SSM support (#183)

* Allows passing an existing role to aws-iam-instance-profile, and the module will attach whatever permissions are needed. This allows using roles that are created and managed by other modules (e.g. EKS worker role), but provides ability to attach a standard set of permissions to that role. It will still always create the instance profile, even if the profile will be unused.
* Removes unused permissions from the aws-iam-instance-profile module for using SSM.

Author: mbarrien

aws-iam-instance-profile/README.md

@@ -39,7 +39,8 @@ resource "aws_instance" "instance" {
 
 | Name | Description | Type | Default | Required |
 |------|-------------|------|---------|:-----:|
-| enable\_ssm | Attach the appropriate policies to allow the instance to integrate with AWS Systems Manager. | `string` | `"true"` | no |
+| create\_role | Creates a role for use with the instance profile. | `bool` | `true` | no |
+| existing\_role\_name | Use existing role with the given name instead of creating a new role. Attaches all standard policies to given role. Only used if create\_role is false. | `string` | n/a | yes |
 | iam\_path | The IAM path to the role. | `string` | `"/"` | no |
 | name\_prefix | Creates a unique name for both the role and instance profile beginning with the specified prefix. Max 32 characters long. | `string` | n/a | yes |
 | role\_description | The description of the IAM role. | `string` | `""` | no |

aws-iam-instance-profile/main.tf

@@ -1,3 +1,7 @@
+locals {
+  role_name = coalescelist(aws_iam_role.role[*].name, [var.existing_role_name])[0]
+}
+
 data "aws_iam_policy_document" "assume-role" {
   statement {
     sid     = "AssumeRole"
@@ -11,6 +15,7 @@ data "aws_iam_policy_document" "assume-role" {
 }
 
 resource "aws_iam_role" "role" {
+  count              = var.create_role ? 1 : 0
   name_prefix        = var.name_prefix
   description        = var.role_description
   path               = var.iam_path
@@ -21,120 +26,17 @@ resource "aws_iam_role" "role" {
   }
 }
 
-resource "aws_iam_role_policy" "ssm" {
-  count  = var.enable_ssm ? 1 : 0
-  role   = aws_iam_role.role.name
-  policy = data.aws_iam_policy_document.ssm_policy.json
-}
-
 resource "aws_iam_role_policy_attachment" "cloudwatch-agent" {
-  role       = aws_iam_role.role.name
+  role       = local.role_name
   policy_arn = "arn:aws:iam::aws:policy/CloudWatchAgentServerPolicy"
 }
 
 resource "aws_iam_instance_profile" "profile" {
   name_prefix = var.name_prefix
   path        = var.iam_path
-  role        = aws_iam_role.role.name
+  role        = local.role_name
 
   lifecycle {
     ignore_changes = [name, name_prefix, path]
   }
 }
-
-data "aws_iam_policy_document" "ssm_policy" {
-  statement {
-    actions = [
-      "ssm:DescribeAssociation",
-      "ssm:GetDeployablePatchSnapshotForInstance",
-      "ssm:GetDocument",
-      "ssm:DescribeDocument",
-      "ssm:GetManifest",
-      "ssm:GetParameters",
-      "ssm:ListAssociations",
-      "ssm:ListInstanceAssociations",
-      "ssm:PutInventory",
-      "ssm:PutComplianceItems",
-      "ssm:PutConfigurePackageResult",
-      "ssm:UpdateAssociationStatus",
-      "ssm:UpdateInstanceAssociationStatus",
-      "ssm:UpdateInstanceInformation",
-    ]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = [
-      "ssmmessages:CreateControlChannel",
-      "ssmmessages:CreateDataChannel",
-      "ssmmessages:OpenControlChannel",
-      "ssmmessages:OpenDataChannel",
-    ]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = [
-      "ec2messages:AcknowledgeMessage",
-      "ec2messages:DeleteMessage",
-      "ec2messages:FailMessage",
-      "ec2messages:GetEndpoint",
-      "ec2messages:GetMessages",
-      "ec2messages:SendReply",
-    ]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = ["cloudwatch:PutMetricData"]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = ["ec2:DescribeInstanceStatus"]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = [
-      "ds:CreateComputer",
-      "ds:DescribeDirectories",
-    ]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = [
-      "logs:CreateLogGroup",
-      "logs:CreateLogStream",
-      "logs:DescribeLogGroups",
-      "logs:DescribeLogStreams",
-      "logs:PutLogEvents",
-    ]
-
-    resources = ["*"]
-  }
-
-  statement {
-    actions = [
-      "s3:GetObject",
-      "s3:ListBucket",
-    ]
-
-    //https://docs.aws.amazon.com/systems-manager/latest/userguide/ssm-agent-minimum-s3-permissions.html
-    resources = [
-      "arn:aws:s3:::aws-ssm-*/*",
-      "arn:aws:s3:::aws-windows-downloads-*/*",
-      "arn:aws:s3:::amazon-ssm-*/*",
-      "arn:aws:s3:::amazon-ssm-packages-*/*",
-      "arn:aws:s3:::*-birdwatcher-prod/*",
-      "arn:aws:s3:::patch-baseline-snapshot-*/*",
-    ]
-  }
-}

aws-iam-instance-profile/module_test.go

@@ -22,19 +22,3 @@ func TestAWSIAMInstanceProfile(t *testing.T) {
 
 	testutil.Run(t, terraformOptions)
 }
-
-func TestAWSIAMInstanceProfileDisableSSM(t *testing.T) {
-	terraformOptions := testutil.Options(
-		testutil.IAMRegion,
-		map[string]interface{}{
-			"name_prefix":      random.UniqueId(),
-			"iam_path":         "/foo/",
-			"role_description": random.UniqueId(),
-			"enable_ssm":       "false",
-		},
-	)
-
-	defer terraform.Destroy(t, terraformOptions)
-
-	testutil.Run(t, terraformOptions)
-}

aws-iam-instance-profile/outputs.tf

@@ -1,10 +1,10 @@
 output "role_arn" {
-  value       = aws_iam_role.role.arn
+  value       = coalescelist(aws_iam_role.role[*].arn, [""])[0]
   description = "The Amazon Resource Name (ARN) specifying the role."
 }
 
 output "role_name" {
-  value       = aws_iam_role.role.name
+  value       = local.role_name
   description = "The name of the role."
 }
 

aws-iam-instance-profile/variables.tf

@@ -3,6 +3,18 @@ variable "name_prefix" {
   description = "Creates a unique name for both the role and instance profile beginning with the specified prefix. Max 32 characters long."
 }
 
+variable "existing_role_name" {
+  type        = string
+  description = "Use existing role with the given name instead of creating a new role. Attaches all standard policies to given role. Only used if create_role is false."
+  default     = null
+}
+
+variable "create_role" {
+  type        = bool
+  description = "Creates a role for use with the instance profile."
+  default     = true
+}
+
 variable "iam_path" {
   type        = string
   default     = "/"
@@ -14,9 +26,3 @@ variable "role_description" {
   description = "The description of the IAM role."
   default     = ""
 }
-
-variable "enable_ssm" {
-  type        = string
-  description = "Attach the appropriate policies to allow the instance to integrate with AWS Systems Manager."
-  default     = "true"
-}