From 9ec52426eed3fc95f74062d59640a85db7d36ff4 Mon Sep 17 00:00:00 2001
From: Vincent Marguerie <24724195+vincentmrg@users.noreply.github.com>
Date: Wed, 10 Apr 2024 17:58:23 +0200
Subject: [PATCH] Add configuration for external-dns IAM (#59)

* Add configuration for external-dns IAM

* Update variables.tf

---------

Co-authored-by: Antonin <9219052+antonincms@users.noreply.github.com>
---
 iam_external_dns.tf | 83 +++++++++++++++++++++++++++++++++++++++++++++
 variables.tf        | 26 ++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 iam_external_dns.tf

diff --git a/iam_external_dns.tf b/iam_external_dns.tf
new file mode 100644
index 0000000..c72e81c
--- /dev/null
+++ b/iam_external_dns.tf
@@ -0,0 +1,83 @@
+/**
+ * Copyright 2020 Quortex
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+
+locals {
+  handle_iam_external_dns = var.handle_iam_resources && var.handle_iam_external_dns
+}
+
+resource "aws_iam_role" "external_dns" {
+  count       = local.handle_iam_external_dns ? 1 : 0
+  name        = var.external_dns_role_name
+  description = "IAM Role required for external-dns."
+
+  assume_role_policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        Effect = "Allow"
+        Principal = {
+          Federated = "arn:aws:iam::${data.aws_caller_identity.current.account_id}:oidc-provider/${local.cluster_oidc_issuer}"
+        }
+        Action = "sts:AssumeRoleWithWebIdentity"
+        Condition = {
+          StringEquals = {
+            "${local.cluster_oidc_issuer}:aud" : "sts.amazonaws.com"
+            "${local.cluster_oidc_issuer}:sub" : "system:serviceaccount:${var.external_dns_sa.namespace}:${var.external_dns_sa.name}"
+          }
+        }
+      }
+    ]
+  })
+
+  tags = var.tags
+}
+
+resource "aws_iam_policy" "external_dns" {
+  count       = local.handle_iam_external_dns ? 1 : 0
+  description = "The policy required for external-dns."
+
+  policy = jsonencode({
+    Version = "2012-10-17"
+    Statement = [
+      {
+        "Effect" : "Allow",
+        "Action" : [
+          "route53:ChangeResourceRecordSets"
+        ],
+        "Resource" : [
+          "arn:aws:route53:::hostedzone/*"
+        ]
+      },
+      {
+        "Effect" : "Allow",
+        "Action" : [
+          "route53:ListHostedZones",
+          "route53:ListResourceRecordSets",
+          "route53:ListTagsForResource"
+        ],
+        "Resource" : [
+          "*"
+        ]
+      }
+    ]
+  })
+}
+
+resource "aws_iam_role_policy_attachment" "external_dns" {
+  count      = local.handle_iam_external_dns ? 1 : 0
+  policy_arn = aws_iam_policy.external_dns[0].arn
+  role       = aws_iam_role.external_dns[0].name
+}
diff --git a/variables.tf b/variables.tf
index ec5a003..b29c185 100644
--- a/variables.tf
+++ b/variables.tf
@@ -108,6 +108,26 @@ variable "aws_load_balancer_controller_sa" {
   }
 }
 
+variable "external_dns_role_name" {
+  type        = string
+  description = "A name to be used as the AWS resource name for the external-dns role."
+  default     = "quortex-external-dns"
+}
+
+variable "external_dns_sa" {
+  description = "Service Account name for external-dns"
+
+  type = object({
+    namespace = string
+    name      = string
+  })
+
+  default = {
+    namespace = "kube-system"
+    name      = "external-dns"
+  }
+}
+
 variable "kubernetes_version" {
   type        = string
   description = "Kubernetes master version."
@@ -217,6 +237,12 @@ variable "handle_iam_aws_load_balancer_controller" {
   default     = false
 }
 
+variable "handle_iam_external_dns" {
+  type        = bool
+  description = "Whether to handle IAM resources lifecycle for external-dns addon"
+  default     = false
+}
+
 variable "master_role_arn" {
   type        = string
   description = "The ARN of a role with the necessary permissions for EKS master. (to be used with handle_iam_resources = false)"