main.tf

provider "aws" {
  region = local.region
}

locals {
  name            = "ex-${replace(basename(path.cwd), "_", "-")}"
  cluster_version = "1.21"
  region          = "eu-west-1"

  tags = {
    Example    = local.name
    GithubRepo = "terraform-aws-eks"
    GithubOrg  = "terraform-aws-modules"
  }
}

data "aws_caller_identity" "current" {}

################################################################################
# EKS Module
################################################################################

module "eks" {
  source = "../.."

  cluster_name                    = local.name
  cluster_version                 = local.cluster_version
  cluster_endpoint_private_access = true
  cluster_endpoint_public_access  = true

  cluster_addons = {
    coredns = {
      resolve_conflicts = "OVERWRITE"
    }
    kube-proxy = {}
    vpc-cni = {
      resolve_conflicts = "OVERWRITE"
    }
  }

  cluster_encryption_config = [{
    provider_key_arn = aws_kms_key.eks.arn
    resources        = ["secrets"]
  }]

  vpc_id     = module.vpc.vpc_id
  subnet_ids = module.vpc.private_subnets

  enable_irsa = true

  # Extend cluster security group rules
  cluster_security_group_additional_rules = {
    egress_nodes_ephemeral_ports_tcp = {
      description                = "To node 1025-65535"
      protocol                   = "tcp"
      from_port                  = 1025
      to_port                    = 65535
      type                       = "egress"
      source_node_security_group = true
    }
  }

  # Extend node-to-node security group rules
  node_security_group_additional_rules = {
    ingress_self_all = {
      description = "Node to node all ports/protocols"
      protocol    = "-1"
      from_port   = 0
      to_port     = 0
      type        = "ingress"
      self        = true
    }
    egress_all = {
      description      = "Node all egress"
      protocol         = "-1"
      from_port        = 0
      to_port          = 0
      type             = "egress"
      cidr_blocks      = ["0.0.0.0/0"]
      ipv6_cidr_blocks = ["::/0"]
    }
  }

  self_managed_node_group_defaults = {
    disk_size = 50
  }

  self_managed_node_groups = {
    # Default node group - as provisioned by the module defaults
    default_node_group = {}

    # Bottlerocket node group
    bottlerocket = {
      name = "bottlerocket-self-mng"

      platform      = "bottlerocket"
      ami_id        = data.aws_ami.eks_default_bottlerocket.id
      instance_type = "m5.large"
      desired_size  = 2
      key_name      = aws_key_pair.this.key_name

      iam_role_additional_policies = ["arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore"]

      bootstrap_extra_args = <<-EOT
      # The admin host container provides SSH access and runs with "superpowers".
      # It is disabled by default, but can be disabled explicitly.
      [settings.host-containers.admin]
      enabled = false

      # The control host container provides out-of-band access via SSM.
      # It is enabled by default, and can be disabled if you do not expect to use SSM.
      # This could leave you with no way to access the API and change settings on an existing node!
      [settings.host-containers.control]
      enabled = true

      [settings.kubernetes.node-labels]
      ingress = "allowed"
      EOT
    }

    mixed = {
      name = "mixed"

      min_size     = 1
      max_size     = 5
      desired_size = 2

      bootstrap_extra_args = "--kubelet-extra-args '--node-labels=node.kubernetes.io/lifecycle=spot'"

      use_mixed_instances_policy = true
      mixed_instances_policy = {
        instances_distribution = {
          on_demand_base_capacity                  = 0
          on_demand_percentage_above_base_capacity = 20
          spot_allocation_strategy                 = "capacity-optimized"
        }

        override = [
          {
            instance_type     = "m5.large"
            weighted_capacity = "1"
          },
          {
            instance_type     = "m6i.large"
            weighted_capacity = "2"
          },
        ]
      }
    }

    # Complete
    complete = {
      name            = "complete-self-mng"
      use_name_prefix = false

      subnet_ids = module.vpc.public_subnets

      min_size     = 1
      max_size     = 7
      desired_size = 1

      ami_id               = data.aws_ami.eks_default.id
      bootstrap_extra_args = "--kubelet-extra-args '--max-pods=110'"

      pre_bootstrap_user_data = <<-EOT
      export CONTAINER_RUNTIME="containerd"
      export USE_MAX_PODS=false
      EOT

      post_bootstrap_user_data = <<-EOT
      echo "you are free little kubelet!"
      EOT

      disk_size     = 256
      instance_type = "m6i.large"

      launch_template_name            = "self-managed-ex"
      launch_template_use_name_prefix = true
      launch_template_description     = "Self managed node group example launch template"

      ebs_optimized          = true
      vpc_security_group_ids = [aws_security_group.additional.id]
      enable_monitoring      = true

      block_device_mappings = {
        xvda = {
          device_name = "/dev/xvda"
          ebs = {
            volume_size           = 75
            volume_type           = "gp3"
            iops                  = 3000
            throughput            = 150
            encrypted             = true
            kms_key_id            = aws_kms_key.ebs.arn
            delete_on_termination = true
          }
        }
      }

      metadata_options = {
        http_endpoint               = "enabled"
        http_tokens                 = "required"
        http_put_response_hop_limit = 2
        instance_metadata_tags      = "disabled"
      }

      create_iam_role          = true
      iam_role_name            = "self-managed-node-group-complete-example"
      iam_role_use_name_prefix = false
      iam_role_description     = "Self managed node group complete example role"
      iam_role_tags = {
        Purpose = "Protector of the kubelet"
      }
      iam_role_additional_policies = [
        "arn:aws:iam::aws:policy/AmazonEC2ContainerRegistryReadOnly"
      ]

      create_security_group          = true
      security_group_name            = "self-managed-node-group-complete-example"
      security_group_use_name_prefix = false
      security_group_description     = "Self managed node group complete example security group"
      security_group_rules = {
        phoneOut = {
          description = "Hello CloudFlare"
          protocol    = "udp"
          from_port   = 53
          to_port     = 53
          type        = "egress"
          cidr_blocks = ["1.1.1.1/32"]
        }
        phoneHome = {
          description                   = "Hello cluster"
          protocol                      = "udp"
          from_port                     = 53
          to_port                       = 53
          type                          = "egress"
          source_cluster_security_group = true # bit of reflection lookup
        }
      }
      security_group_tags = {
        Purpose = "Protector of the kubelet"
      }

      timeouts = {
        create = "80m"
        update = "80m"
        delete = "80m"
      }

      tags = {
        ExtraTag = "Self managed node group complete example"
      }
    }
  }

  tags = local.tags
}

################################################################################
# aws-auth configmap
# Only EKS managed node groups automatically add roles to aws-auth configmap
# so we need to ensure fargate profiles and self-managed node roles are added
################################################################################

data "aws_eks_cluster_auth" "this" {
  name = module.eks.cluster_id
}

locals {
  kubeconfig = yamlencode({
    apiVersion      = "v1"
    kind            = "Config"
    current-context = "terraform"
    clusters = [{
      name = module.eks.cluster_id
      cluster = {
        certificate-authority-data = module.eks.cluster_certificate_authority_data
        server                     = module.eks.cluster_endpoint
      }
    }]
    contexts = [{
      name = "terraform"
      context = {
        cluster = module.eks.cluster_id
        user    = "terraform"
      }
    }]
    users = [{
      name = "terraform"
      user = {
        token = data.aws_eks_cluster_auth.this.token
      }
    }]
  })
}

resource "null_resource" "apply" {
  triggers = {
    kubeconfig = base64encode(local.kubeconfig)
    cmd_patch  = <<-EOT
      kubectl create configmap aws-auth -n kube-system --kubeconfig <(echo $KUBECONFIG | base64 --decode)
      kubectl patch configmap/aws-auth --patch "${module.eks.aws_auth_configmap_yaml}" -n kube-system --kubeconfig <(echo $KUBECONFIG | base64 --decode)
    EOT
  }

  provisioner "local-exec" {
    interpreter = ["/bin/bash", "-c"]
    environment = {
      KUBECONFIG = self.triggers.kubeconfig
    }
    command = self.triggers.cmd_patch
  }
}

################################################################################
# Supporting Resources
################################################################################

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 3.0"

  name = local.name
  cidr = "10.0.0.0/16"

  azs             = ["${local.region}a", "${local.region}b", "${local.region}c"]
  private_subnets = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
  public_subnets  = ["10.0.4.0/24", "10.0.5.0/24", "10.0.6.0/24"]

  enable_nat_gateway   = true
  single_nat_gateway   = true
  enable_dns_hostnames = true

  enable_flow_log                      = true
  create_flow_log_cloudwatch_iam_role  = true
  create_flow_log_cloudwatch_log_group = true

  public_subnet_tags = {
    "kubernetes.io/cluster/${local.name}" = "shared"
    "kubernetes.io/role/elb"              = 1
  }

  private_subnet_tags = {
    "kubernetes.io/cluster/${local.name}" = "shared"
    "kubernetes.io/role/internal-elb"     = 1
  }

  tags = local.tags
}

resource "aws_security_group" "additional" {
  name_prefix = "${local.name}-additional"
  vpc_id      = module.vpc.vpc_id

  ingress {
    from_port = 22
    to_port   = 22
    protocol  = "tcp"
    cidr_blocks = [
      "10.0.0.0/8",
      "172.16.0.0/12",
      "192.168.0.0/16",
    ]
  }

  tags = local.tags
}

resource "aws_kms_key" "eks" {
  description             = "EKS Secret Encryption Key"
  deletion_window_in_days = 7
  enable_key_rotation     = true

  tags = local.tags
}

data "aws_ami" "eks_default" {
  most_recent = true
  owners      = ["amazon"]

  filter {
    name   = "name"
    values = ["amazon-eks-node-${local.cluster_version}-v*"]
  }
}

data "aws_ami" "eks_default_bottlerocket" {
  most_recent = true
  owners      = ["amazon"]

  filter {
    name   = "name"
    values = ["bottlerocket-aws-k8s-${local.cluster_version}-x86_64-*"]
  }
}

resource "tls_private_key" "this" {
  algorithm = "RSA"
}

resource "aws_key_pair" "this" {
  key_name   = local.name
  public_key = tls_private_key.this.public_key_openssh
}

resource "aws_kms_key" "ebs" {
  description             = "Customer managed key to encrypt self managed node group volumes"
  deletion_window_in_days = 7
  policy                  = data.aws_iam_policy_document.ebs.json
}

# This policy is required for the KMS key used for EKS root volumes, so the cluster is allowed to enc/dec/attach encrypted EBS volumes
data "aws_iam_policy_document" "ebs" {
  # Copy of default KMS policy that lets you manage it
  statement {
    sid       = "Enable IAM User Permissions"
    actions   = ["kms:*"]
    resources = ["*"]

    principals {
      type        = "AWS"
      identifiers = ["arn:aws:iam::${data.aws_caller_identity.current.account_id}:root"]
    }
  }

  # Required for EKS
  statement {
    sid = "Allow service-linked role use of the CMK"
    actions = [
      "kms:Encrypt",
      "kms:Decrypt",
      "kms:ReEncrypt*",
      "kms:GenerateDataKey*",
      "kms:DescribeKey"
    ]
    resources = ["*"]

    principals {
      type = "AWS"
      identifiers = [
        "arn:aws:iam::${data.aws_caller_identity.current.account_id}:role/aws-service-role/autoscaling.amazonaws.com/AWSServiceRoleForAutoScaling", # required for the ASG to manage encrypted volumes for nodes
        module.eks.cluster_iam_role_arn,                                                                                                            # required for the cluster / persistentvolume-controller to create encrypted PVCs
      ]
    }
  }

  statement {
    sid       = "Allow attachment of persistent resources"
    actions   = ["kms:CreateGrant"]
    resources = ["*"]

    principals {
      type = "AWS"
      identifiers = [
        "arn:aws:iam::${data.aws_caller_identity.current.account_id}:role/aws-service-role/autoscaling.amazonaws.com/AWSServiceRoleForAutoScaling", # required for the ASG to manage encrypted volumes for nodes
        module.eks.cluster_iam_role_arn,                                                                                                            # required for the cluster / persistentvolume-controller to create encrypted PVCs
      ]
    }

    condition {
      test     = "Bool"
      variable = "kms:GrantIsForAWSResource"
      values   = ["true"]
    }
  }
}