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feat: Added org_id and source_accounts to allow SNS topic to receive AWS Config events from sub-accounts
Add optional org_id and source_accounts variables to the stack module's SNS topic policy to support AWS Organizations and Control Tower integrations.
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‎modules/stack/README.md‎

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@@ -160,6 +160,7 @@ You can additionally configure other submodules in this manner:
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| [aws_sns_topic.this](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/sns_topic) | resource |
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| [aws_sns_topic_policy.this](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/sns_topic_policy) | resource |
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| [aws_sns_topic_subscription.this](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/sns_topic_subscription) | resource |
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| [aws_caller_identity.current](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/caller_identity) | data source |
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| [aws_iam_policy_document.sns_topic_policy](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/iam_policy_document) | data source |
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## Inputs
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| <a name="input_logwriter"></a> [logwriter](#input\_logwriter) | Variables for AWS CloudWatch Logs collection. | <pre>object({<br> log_group_name_patterns = optional(list(string))<br> log_group_name_prefixes = optional(list(string))<br> exclude_log_group_name_prefixes = optional(list(string))<br> buffering_interval = optional(number)<br> buffering_size = optional(number)<br> filter_name = optional(string)<br> filter_pattern = optional(string)<br> num_workers = optional(number)<br> discovery_rate = optional(string, "24 hours")<br> lambda_memory_size = optional(number)<br> lambda_timeout = optional(number)<br> lambda_env_vars = optional(map(string))<br> lambda_runtime = optional(string)<br> code_uri = optional(string)<br> sam_release_version = optional(string)<br> })</pre> | `null` | no |
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| <a name="input_metricstream"></a> [metricstream](#input\_metricstream) | Variables for AWS CloudWatch Metrics Stream collection. | <pre>object({<br> include_filters = optional(list(object({ namespace = string, metric_names = optional(list(string)) })))<br> exclude_filters = optional(list(object({ namespace = string, metric_names = optional(list(string)) })))<br> buffering_interval = optional(number)<br> buffering_size = optional(number)<br> sam_release_version = optional(string)<br> })</pre> | `null` | no |
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| <a name="input_name"></a> [name](#input\_name) | Name of role. Since this name must be unique within the<br>account, it will be reused for most of the resources created by this<br>module. | `string` | n/a | yes |
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| <a name="input_org_id"></a> [org\_id](#input\_org\_id) | Optional AWS Organizations ID. If set, adds an AllowAWSConfigFromOrg statement on the SNS topic that allows publishes by aws:PrincipalOrgID. Useful for AWS Control Tower integrations. | `string` | `null` | no |
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| <a name="input_s3_bucket_lifecycle_expiration"></a> [s3\_bucket\_lifecycle\_expiration](#input\_s3\_bucket\_lifecycle\_expiration) | Expiration in days for S3 objects in collection bucket | `number` | `4` | no |
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| <a name="input_sam_release_version"></a> [sam\_release\_version](#input\_sam\_release\_version) | Release version for SAM apps as defined on github.com/observeinc/aws-sam-apps. | `string` | `null` | no |
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| <a name="input_source_accounts"></a> [source\_accounts](#input\_source\_accounts) | List of AWS account IDs allowed to publish to the SNS topic via AWS Config. Useful for sub-accounts in AWS Organizations and Control Tower integrations.<br>The current account ID is automatically included when this list is non-empty. | `list(string)` | <pre>[<br> "891377094505"<br>]</pre> | no |
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| <a name="input_verbosity"></a> [verbosity](#input\_verbosity) | Logging verbosity for Lambda. Highest log verbosity is 9. | `number` | `null` | no |
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## Outputs

‎modules/stack/sns.tf‎

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data "aws_caller_identity" "current" {}
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locals {
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# When source_accounts is set, automatically include the current (audit) account
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# to ensure the local AWS Config can also publish to the SNS topic
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effective_source_accounts = length(var.source_accounts) > 0 ? distinct(concat(
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var.source_accounts,
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[data.aws_caller_identity.current.account_id]
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)) : []
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}
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resource "aws_sns_topic" "this" {
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name_prefix = "${var.name}-"
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}
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aws_sns_topic.this.arn,
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]
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}
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# Optional: if org_id is set, add an AllowAWSConfigFromOrg statement that
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# allows config.amazonaws.com to publish, restricted by aws:PrincipalOrgID.
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dynamic "statement" {
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for_each = var.org_id == null ? [] : [1]
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content {
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sid = "AllowAWSConfigFromOrg"
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effect = "Allow"
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principals {
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type = "Service"
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identifiers = ["config.amazonaws.com"]
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}
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actions = [
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"SNS:Publish",
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]
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resources = [
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aws_sns_topic.this.arn
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]
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condition {
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test = "StringEquals"
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variable = "aws:PrincipalOrgID"
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values = [var.org_id]
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}
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}
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}
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# Optional: if source_accounts is non-empty, add an AllowAWSConfigFromSourceAccounts
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# statement that restricts publishes by AWS:SourceAccount.
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# This automatically includes the current (audit) account ID.
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dynamic "statement" {
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for_each = length(local.effective_source_accounts) == 0 ? [] : [1]
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content {
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sid = "AllowAWSConfigFromSourceAccounts"
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effect = "Allow"
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principals {
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type = "Service"
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identifiers = ["config.amazonaws.com"]
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}
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actions = [
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"SNS:Publish",
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]
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resources = [
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aws_sns_topic.this.arn,
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]
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condition {
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test = "StringEquals"
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variable = "AWS:SourceAccount"
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values = local.effective_source_accounts
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}
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}
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}
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}
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resource "aws_sns_topic_subscription" "this" {

‎modules/stack/variables.tf‎

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type = string
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default = null
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}
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# Optional AWS Organizations ID. If set, we'll add an AllowAWSConfigFromOrg
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# statement on the SNS topic that restricts publishes by aws:PrincipalOrgID.
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variable "org_id" {
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description = "Optional AWS Organizations ID. If set, adds an AllowAWSConfigFromOrg statement on the SNS topic that allows publishes by aws:PrincipalOrgID. Useful for AWS Control Tower integrations."
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type = string
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default = null
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}
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# Optional list of AWS SourceAccount IDs. If non-empty, we'll add a
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# statement that restricts publishes using the AWS:SourceAccount condition.
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# The current (audit) account ID is automatically included in the list.
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variable "source_accounts" {
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type = list(string)
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default = ["891377094505"]
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description = <<-EOF
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List of AWS account IDs allowed to publish to the SNS topic via AWS Config. Useful for sub-accounts in AWS Organizations and Control Tower integrations.
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The current account ID is automatically included when this list is non-empty.
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EOF
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}

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