main.tf

data "aws_partition" "current" {}

################################################################################
# Cluster
################################################################################

resource "aws_eks_cluster" "this" {
  count = var.create ? 1 : 0

  name                      = var.cluster_name
  role_arn                  = try(aws_iam_role.this[0].arn, var.iam_role_arn)
  version                   = var.cluster_version
  enabled_cluster_log_types = var.cluster_enabled_log_types

  vpc_config {
    security_group_ids      = distinct(concat(var.cluster_additional_security_group_ids, [local.cluster_security_group_id]))
    subnet_ids              = var.subnet_ids
    endpoint_private_access = var.cluster_endpoint_private_access
    endpoint_public_access  = var.cluster_endpoint_public_access
    public_access_cidrs     = var.cluster_endpoint_public_access_cidrs
  }

  kubernetes_network_config {
    service_ipv4_cidr = var.cluster_service_ipv4_cidr
  }

  dynamic "encryption_config" {
    for_each = toset(var.cluster_encryption_config)

    content {
      provider {
        key_arn = encryption_config.value["provider_key_arn"]
      }
      resources = encryption_config.value["resources"]
    }
  }

  tags = merge(
    var.tags,
    var.cluster_tags,
  )

  timeouts {
    create = lookup(var.cluster_timeouts, "create", null)
    delete = lookup(var.cluster_timeouts, "update", null)
    update = lookup(var.cluster_timeouts, "delete", null)
  }

  depends_on = [
    aws_iam_role_policy_attachment.this,
    aws_security_group_rule.cluster,
    aws_security_group_rule.node,
    aws_cloudwatch_log_group.this
  ]
}

resource "aws_cloudwatch_log_group" "this" {
  count = var.create && var.create_cloudwatch_log_group ? 1 : 0

  name              = "/aws/eks/${var.cluster_name}/cluster"
  retention_in_days = var.cloudwatch_log_group_retention_in_days
  kms_key_id        = var.cloudwatch_log_group_kms_key_id

  tags = var.tags
}

################################################################################
# Cluster Security Group
# Defaults follow https://docs.aws.amazon.com/eks/latest/userguide/sec-group-reqs.html
################################################################################

locals {
  cluster_sg_name   = coalesce(var.cluster_security_group_name, "${var.cluster_name}-cluster")
  create_cluster_sg = var.create && var.create_cluster_security_group

  cluster_security_group_id = local.create_cluster_sg ? aws_security_group.cluster[0].id : var.cluster_security_group_id

  cluster_security_group_rules = {
    ingress_nodes_443 = {
      description                = "Node groups to cluster API"
      protocol                   = "tcp"
      from_port                  = 443
      to_port                    = 443
      type                       = "ingress"
      source_node_security_group = true
    }
    egress_nodes_443 = {
      description                = "Cluster API to node groups"
      protocol                   = "tcp"
      from_port                  = 443
      to_port                    = 443
      type                       = "egress"
      source_node_security_group = true
    }
    egress_nodes_kubelet = {
      description                = "Cluster API to node kubelets"
      protocol                   = "tcp"
      from_port                  = 10250
      to_port                    = 10250
      type                       = "egress"
      source_node_security_group = true
    }
  }
}

resource "aws_security_group" "cluster" {
  count = local.create_cluster_sg ? 1 : 0

  name        = var.cluster_security_group_use_name_prefix ? null : local.cluster_sg_name
  name_prefix = var.cluster_security_group_use_name_prefix ? "${local.cluster_sg_name}${var.prefix_separator}" : null
  description = var.cluster_security_group_description
  vpc_id      = var.vpc_id

  tags = merge(
    var.tags,
    { "Name" = local.cluster_sg_name },
    var.cluster_security_group_tags
  )
}

resource "aws_security_group_rule" "cluster" {
  for_each = { for k, v in merge(local.cluster_security_group_rules, var.cluster_security_group_additional_rules) : k => v if local.create_cluster_sg }

  # Required
  security_group_id = aws_security_group.cluster[0].id
  protocol          = each.value.protocol
  from_port         = each.value.from_port
  to_port           = each.value.to_port
  type              = each.value.type

  # Optional
  description      = try(each.value.description, null)
  cidr_blocks      = try(each.value.cidr_blocks, null)
  ipv6_cidr_blocks = try(each.value.ipv6_cidr_blocks, null)
  prefix_list_ids  = try(each.value.prefix_list_ids, [])
  self             = try(each.value.self, null)
  source_security_group_id = try(
    each.value.source_security_group_id,
    try(each.value.source_node_security_group, false) ? local.node_security_group_id : null
  )
}

################################################################################
# IRSA
# Note - this is different from EKS identity provider
################################################################################

data "tls_certificate" "this" {
  count = var.create && var.enable_irsa ? 1 : 0

  url = aws_eks_cluster.this[0].identity[0].oidc[0].issuer
}

resource "aws_iam_openid_connect_provider" "oidc_provider" {
  count = var.create && var.enable_irsa ? 1 : 0

  client_id_list  = distinct(compact(concat(["sts.${data.aws_partition.current.dns_suffix}"], var.openid_connect_audiences)))
  thumbprint_list = [data.tls_certificate.this[0].certificates[0].sha1_fingerprint]
  url             = aws_eks_cluster.this[0].identity[0].oidc[0].issuer

  tags = merge(
    { Name = "${var.cluster_name}-eks-irsa" },
    var.tags
  )
}

################################################################################
# IAM Role
################################################################################

locals {
  iam_role_name     = coalesce(var.iam_role_name, "${var.cluster_name}-cluster")
  policy_arn_prefix = "arn:${data.aws_partition.current.partition}:iam::aws:policy"
}

data "aws_iam_policy_document" "assume_role_policy" {
  count = var.create && var.create_iam_role ? 1 : 0

  statement {
    sid     = "EKSClusterAssumeRole"
    actions = ["sts:AssumeRole"]

    principals {
      type        = "Service"
      identifiers = ["eks.amazonaws.com"]
    }
  }
}

resource "aws_iam_role" "this" {
  count = var.create && var.create_iam_role ? 1 : 0

  name        = var.iam_role_use_name_prefix ? null : local.iam_role_name
  name_prefix = var.iam_role_use_name_prefix ? "${local.iam_role_name}${var.prefix_separator}" : null
  path        = var.iam_role_path
  description = var.iam_role_description

  assume_role_policy    = data.aws_iam_policy_document.assume_role_policy[0].json
  permissions_boundary  = var.iam_role_permissions_boundary
  force_detach_policies = true

  tags = merge(var.tags, var.iam_role_tags)
}

# Policies attached ref https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/eks_node_group
resource "aws_iam_role_policy_attachment" "this" {
  for_each = var.create && var.create_iam_role ? toset(compact(distinct(concat([
    "${local.policy_arn_prefix}/AmazonEKSClusterPolicy",
    "${local.policy_arn_prefix}/AmazonEKSVPCResourceController",
  ], var.iam_role_additional_policies)))) : toset([])

  policy_arn = each.value
  role       = aws_iam_role.this[0].name
}

################################################################################
# EKS Addons
################################################################################

resource "aws_eks_addon" "this" {
  for_each = { for k, v in var.cluster_addons : k => v if var.create }

  cluster_name = aws_eks_cluster.this[0].name
  addon_name   = try(each.value.name, each.key)

  addon_version            = lookup(each.value, "addon_version", null)
  resolve_conflicts        = lookup(each.value, "resolve_conflicts", null)
  service_account_role_arn = lookup(each.value, "service_account_role_arn", null)

  lifecycle {
    ignore_changes = [
      modified_at
    ]
  }

  tags = var.tags
}

################################################################################
# EKS Identity Provider
# Note - this is different from IRSA
################################################################################

resource "aws_eks_identity_provider_config" "this" {
  for_each = { for k, v in var.cluster_identity_providers : k => v if var.create }

  cluster_name = aws_eks_cluster.this[0].name

  oidc {
    client_id                     = each.value.client_id
    groups_claim                  = lookup(each.value, "groups_claim", null)
    groups_prefix                 = lookup(each.value, "groups_prefix", null)
    identity_provider_config_name = try(each.value.identity_provider_config_name, each.key)
    issuer_url                    = each.value.issuer_url
    required_claims               = lookup(each.value, "required_claims", null)
    username_claim                = lookup(each.value, "username_claim", null)
    username_prefix               = lookup(each.value, "username_prefix", null)
  }

  tags = var.tags
}