Task: Create an IAM role for EKS Fargate profiles with the necessary policies for pod execution. Attach the AmazonEKSFargatePodExecutionRolePolicy to the IAM role. Define an AWS EKS Fargate profile for the 'kube-system' namespace, associating it with the EKS cluster and specifying the pod execution role ARN. Ensure that the specified subnets have the required resource tag for cluster association. Use a null_resource to patch the Kubernetes deployment 'coredns' in the 'kube-system' namespace, using the EKS cluster's endpoint, certificate authority, and authentication token for communication.

Specification:
Resource "aws_iam_role" "eks-fargate-profile"
has one "name"
has one "assume_role_policy"
Resource "aws_iam_role_policy_attachment" "eks-fargate-profile"
has one "policy_arn"
has one "role"
Resource "aws_eks_fargate_profile" "kube-system"
has one "cluster_name"
has one "fargate_profile_name"
has one "pod_execution_role_arn"
has one "subnet_ids"
has one "namespace" in "selector"
Data "aws_eks_cluster_auth" "eks"
has one "name"
Resource "null_resource" "k8s_patcher"
has multiple "triggers" (endpoint, ca_crt, token)
uses a "local-exec" provisioner to execute a command that patches the Kubernetes deployment
has a "lifecycle" policy to ignore changes in "triggers"

Terraform configuration (main.tf):
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = ">= 5.75"
    }
  }

  required_version = ">= 1.9.0"
}

provider "aws" {
  region = "us-east-1"
}

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
}

data "aws_availability_zones" "available" {
  state = "available"
}

resource "aws_subnet" "test_eks_1" {
  vpc_id     = aws_vpc.main.id
  cidr_block = "10.0.1.0/24"

  availability_zone = data.aws_availability_zones.available.names[0]

  tags = {
    "kubernetes.io/cluster/test" = "shared"
  }
}

resource "aws_subnet" "test_eks_2" {
  vpc_id     = aws_vpc.main.id
  cidr_block = "10.0.2.0/24"

  availability_zone = data.aws_availability_zones.available.names[1]

  tags = {
    "kubernetes.io/cluster/test" = "shared"
  }
}

resource "aws_iam_role" "eks-cluster" {
  name = "eks-cluster-1"

  assume_role_policy = <<POLICY
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "eks.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}
POLICY
}

resource "aws_iam_role_policy_attachment" "eks_cluster_policy" {
  policy_arn = "arn:aws:iam::aws:policy/AmazonEKSClusterPolicy"
  role       = aws_iam_role.eks-cluster.name
}

resource "aws_iam_role_policy_attachment" "eks_service_policy" {
  policy_arn = "arn:aws:iam::aws:policy/AmazonEKSServicePolicy"
  role       = aws_iam_role.eks-cluster.name
}


resource "aws_eks_cluster" "cluster" {
  name     = "test"
  role_arn = aws_iam_role.eks-cluster.arn

  vpc_config {
    subnet_ids = [
      aws_subnet.test_eks_1.id,
      aws_subnet.test_eks_2.id
    ]
  }

  depends_on = [
    aws_iam_role_policy_attachment.eks_cluster_policy,
    aws_iam_role_policy_attachment.eks_service_policy,
  ]
}

resource "aws_iam_role" "eks-fargate-profile" {
  name = "eks-fargate-profile"

  assume_role_policy = jsonencode({
    Statement = [{
      Action = "sts:AssumeRole"
      Effect = "Allow"
      Principal = {
        Service = "eks-fargate-pods.amazonaws.com"
      }
    }]
    Version = "2012-10-17"
  })
}

resource "aws_iam_role_policy_attachment" "eks-fargate-profile" {
  policy_arn = "arn:aws:iam::aws:policy/AmazonEKSFargatePodExecutionRolePolicy"
  role       = aws_iam_role.eks-fargate-profile.name
}

resource "aws_eks_fargate_profile" "kube-system" {
  cluster_name           = aws_eks_cluster.cluster.name
  fargate_profile_name   = "kube-system"
  pod_execution_role_arn = aws_iam_role.eks-fargate-profile.arn

  subnet_ids = [
    aws_subnet.test_eks_1.id,
    aws_subnet.test_eks_2.id
  ]

  selector {
    namespace = "kube-system"
  }

  depends_on = [ aws_iam_role_policy_attachment.eks-fargate-profile ]
}

data "aws_eks_cluster_auth" "eks" {
  name = aws_eks_cluster.cluster.id
}

resource "null_resource" "k8s_patcher" {
  depends_on = [aws_eks_fargate_profile.kube-system]

  triggers = {
    endpoint = aws_eks_cluster.cluster.endpoint
    ca_crt   = base64decode(aws_eks_cluster.cluster.certificate_authority[0].data)
    token    = data.aws_eks_cluster_auth.eks.token
  }

  provisioner "local-exec" {
    command = <<EOH
      cat >/tmp/ca.crt <<EOF
      ${base64decode(aws_eks_cluster.cluster.certificate_authority[0].data)}
      EOF
      kubectl \
        --server="${aws_eks_cluster.cluster.endpoint}" \
        --certificate_authority=/tmp/ca.crt \
        --token="${data.aws_eks_cluster_auth.eks.token}" \
        patch deployment coredns \
        -n kube-system --type json \
        -p='[{"op": "remove", "path": "/spec/template/metadata/annotations/eks.amazonaws.com~1compute-type"}]'
      EOH
  }

  lifecycle {
    ignore_changes = [triggers]
  }
}

Validation policy (checks.rego):
package terraform.validation

default has_aws_iam_role_fargate = false
default has_aws_iam_role_policy_attachment_fargate = false
default has_aws_eks_fargate_profile = false
default has_aws_eks_cluster_auth = false
default has_null_resource_k8s_patcher = false

has_aws_iam_role_fargate {
    role := input.planned_values.root_module.resources[_]
    role.type == "aws_iam_role"
    role.name == "eks-fargate-profile"
    role.values.name == "eks-fargate-profile"
    role.values.assume_role_policy != null
}

has_aws_iam_role_policy_attachment_fargate {
    attachment := input.planned_values.root_module.resources[_]
    attachment.type == "aws_iam_role_policy_attachment"
    attachment.name == "eks-fargate-profile"
    attachment.values.policy_arn == "arn:aws:iam::aws:policy/AmazonEKSFargatePodExecutionRolePolicy"
    attachment.values.role == input.planned_values.root_module.resources[_].values.name  # Ensure role is correctly referenced
}

has_aws_eks_fargate_profile {
    fargate_profile := input.configuration.root_module.resources[_]
    fargate_profile.type == "aws_eks_fargate_profile"
    fargate_profile.name == "kube-system"
    fargate_profile.expressions.cluster_name != null
    fargate_profile.expressions.fargate_profile_name.constant_value == "kube-system"
    fargate_profile.expressions.pod_execution_role_arn != null
    count(fargate_profile.expressions.subnet_ids.references) == 4  # Ensure there are two subnet IDs
    fargate_profile.expressions.selector[_].namespace.constant_value == "kube-system"
}

has_aws_eks_cluster_auth {
    cluster_auth := input.configuration.root_module.resources[_]
    cluster_auth.type == "aws_eks_cluster_auth"
    cluster_auth.name != null  # Check for proper referencing
}

has_null_resource_k8s_patcher {
    k8s_patcher := input.configuration.root_module.resources[_]
    k8s_patcher.type == "null_resource"
    k8s_patcher.name == "k8s_patcher"
    k8s_patcher.depends_on != null
    count(k8s_patcher.expressions.triggers.references) == 8  # Check for three triggers
    k8s_patcher.provisioners[0].type == "local-exec"
    k8s_patcher.provisioners[0].expressions.command != null
}

valid_configuration {
    has_aws_iam_role_fargate
    has_aws_iam_role_policy_attachment_fargate
    has_aws_eks_fargate_profile
    has_aws_eks_cluster_auth
    has_null_resource_k8s_patcher
}