feat(runner): Ability to disable default runner security group creation (#1718)

* Implement optional disable for the managed security group creation.

* Create security group disablement variable.

* Fix launch template creation issue.

* Fix formatting error.

Author: Király Ádám

Diff for: README.md

@@ -402,6 +402,7 @@ In case the setup does not work as intended follow the trace of events:
 | <a name="input_delay_webhook_event"></a> [delay\_webhook\_event](#input\_delay\_webhook\_event) | The number of seconds the event accepted by the webhook is invisible on the queue before the scale up lambda will receive the event. | `number` | `30` | no |
 | <a name="input_enable_cloudwatch_agent"></a> [enable\_cloudwatch\_agent](#input\_enable\_cloudwatch\_agent) | Enabling the cloudwatch agent on the ec2 runner instances, the runner contains default config. Configuration can be overridden via `cloudwatch_config`. | `bool` | `true` | no |
 | <a name="input_enable_ephemeral_runners"></a> [enable\_ephemeral\_runners](#input\_enable\_ephemeral\_runners) | Enable ephemeral runners, runners will only be used once. | `bool` | `false` | no |
+| <a name="input_enable_managed_runner_security_group"></a> [enable\_managed\_runner\_security\_group](#inputenable\_managed\_runner\_security\_group) | Enabling the default managed security group creation. Unmanaged security groups can be specified via `runner_additional_security_group_ids`. | `bool` | `true` | no |
 | <a name="input_enable_organization_runners"></a> [enable\_organization\_runners](#input\_enable\_organization\_runners) | Register runners to organization, instead of repo level | `bool` | `false` | no |
 | <a name="input_enable_ssm_on_runners"></a> [enable\_ssm\_on\_runners](#input\_enable\_ssm\_on\_runners) | Enable to allow access the runner instances for debugging purposes via SSM. Note that this adds additional permissions to the runner instances. | `bool` | `false` | no |
 | <a name="input_enabled_userdata"></a> [enabled\_userdata](#input\_enabled\_userdata) | Should the userdata script be enabled for the runner. Set this to false if you are using your own prebuilt AMI | `bool` | `true` | no |

Diff for: main.tf

@@ -107,6 +107,7 @@ module "runners" {
   github_app_parameters                = local.github_app_parameters
   enable_organization_runners          = var.enable_organization_runners
   enable_ephemeral_runners             = var.enable_ephemeral_runners
+  enable_managed_runner_security_group = var.enable_managed_runner_security_group
   scale_down_schedule_expression       = var.scale_down_schedule_expression
   minimum_running_time_in_minutes      = var.minimum_running_time_in_minutes
   runner_boot_time_in_minutes          = var.runner_boot_time_in_minutes

Diff for: modules/runners/README.md

@@ -122,6 +122,7 @@ yarn run dist
 | <a name="input_egress_rules"></a> [egress\_rules](#input\_egress\_rules) | List of egress rules for the GitHub runner instances. | <pre>list(object({<br>    cidr_blocks      = list(string)<br>    ipv6_cidr_blocks = list(string)<br>    prefix_list_ids  = list(string)<br>    from_port        = number<br>    protocol         = string<br>    security_groups  = list(string)<br>    self             = bool<br>    to_port          = number<br>    description      = string<br>  }))</pre> | <pre>[<br>  {<br>    "cidr_blocks": [<br>      "0.0.0.0/0"<br>    ],<br>    "description": null,<br>    "from_port": 0,<br>    "ipv6_cidr_blocks": [<br>      "::/0"<br>    ],<br>    "prefix_list_ids": null,<br>    "protocol": "-1",<br>    "security_groups": null,<br>    "self": null,<br>    "to_port": 0<br>  }<br>]</pre> | no |
 | <a name="input_enable_cloudwatch_agent"></a> [enable\_cloudwatch\_agent](#input\_enable\_cloudwatch\_agent) | Enabling the cloudwatch agent on the ec2 runner instances, the runner contains default config. Configuration can be overridden via `cloudwatch_config`. | `bool` | `true` | no |
 | <a name="input_enable_ephemeral_runners"></a> [enable\_ephemeral\_runners](#input\_enable\_ephemeral\_runners) | Enable ephemeral runners, runners will only be used once. | `bool` | `false` | no |
+| <a name="input_enable_managed_runner_security_group"></a> [enable\_managed\_runner\_security\_group](#inputenable\_managed\_runner\_security\_group) | Enabling the default managed security group creation. Unmanaged security groups can be specified via `runner_additional_security_group_ids`. | `bool` | `true` | no |
 | <a name="input_enable_organization_runners"></a> [enable\_organization\_runners](#input\_enable\_organization\_runners) | n/a | `bool` | n/a | yes |
 | <a name="input_enable_ssm_on_runners"></a> [enable\_ssm\_on\_runners](#input\_enable\_ssm\_on\_runners) | Enable to allow access to the runner instances for debugging purposes via SSM. Note that this adds additional permissions to the runner instances. | `bool` | n/a | yes |
 | <a name="input_enabled_userdata"></a> [enabled\_userdata](#input\_enabled\_userdata) | Should the userdata script be enabled for the runner. Set this to false if you are using your own prebuilt AMI | `bool` | `true` | no |

Diff for: modules/runners/main.tf

@@ -88,7 +88,7 @@ resource "aws_launch_template" "runner" {
   key_name                             = var.key_name
 
   vpc_security_group_ids = compact(concat(
-    [aws_security_group.runner_sg.id],
+    var.enable_managed_runner_security_group ? [aws_security_group.runner_sg[0].id] : [],
     var.runner_additional_security_group_ids,
   ))
 
@@ -136,6 +136,7 @@ resource "aws_launch_template" "runner" {
 }
 
 resource "aws_security_group" "runner_sg" {
+  count       = var.enable_managed_runner_security_group ? 1 : 0
   name_prefix = "${var.environment}-github-actions-runner-sg"
   description = "Github Actions Runner security group"
 

Diff for: modules/runners/variables.tf

@@ -318,6 +318,12 @@ variable "enable_cloudwatch_agent" {
   default     = true
 }
 
+variable "enable_managed_runner_security_group" {
+  description = "Enabling the default managed security group creation. Unmanaged security groups can be specified via `runner_additional_security_group_ids`."
+  type        = bool
+  default     = true
+}
+
 variable "cloudwatch_config" {
   description = "(optional) Replaces the module default cloudwatch log config. See https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch-Agent-Configuration-File-Details.html for details."
   type        = string

Diff for: variables.tf

@@ -501,6 +501,12 @@ variable "enable_ephemeral_runners" {
   default     = false
 }
 
+variable "enable_managed_runner_security_group" {
+  description = "Enabling the default managed security group creation. Unmanaged security groups can be specified via `runner_additional_security_group_ids`."
+  type        = bool
+  default     = true
+}
+
 variable "runner_os" {
   description = "The EC2 Operating System type to use for action runner instances (linux,windows)."
   type        = string