Improve internal firewall rules on Google Cloud

* Whitelist internal traffic between controllers and workers
* Switch to tag-based firewall policies rather than source IP

CHANGES.md

@@ -14,6 +14,7 @@ Notable changes between versions.
 * Change etcd to run on-host, across controllers (etcd-member.service)
 * Change controller instances to automatically span zones in the region
 * Change worker managed instance group to automatically span zones in the region
+* Improve internal firewall rules and use tag-based firewall policies
 * Remove support for self-hosted etcd
 * Remove the `zone` required variable
 * Remove the `controller_preemptible` optional variable

google-cloud/container-linux/kubernetes/controllers/controllers.tf

@@ -48,6 +48,7 @@ resource "google_compute_instance" "controllers" {
   }
 
   can_ip_forward = true
+  tags = ["${var.cluster_name}-controller"]
 }
 
 # Controller Container Linux Config

google-cloud/container-linux/kubernetes/network.tf

@@ -4,18 +4,6 @@ resource "google_compute_network" "network" {
   auto_create_subnetworks = true
 }
 
-resource "google_compute_firewall" "allow-ingress" {
-  name    = "${var.cluster_name}-allow-ingress"
-  network = "${google_compute_network.network.name}"
-
-  allow {
-    protocol = "tcp"
-    ports    = [80, 443]
-  }
-
-  source_ranges = ["0.0.0.0/0"]
-}
-
 resource "google_compute_firewall" "allow-ssh" {
   name    = "${var.cluster_name}-allow-ssh"
   network = "${google_compute_network.network.name}"
@@ -26,31 +14,55 @@ resource "google_compute_firewall" "allow-ssh" {
   }
 
   source_ranges = ["0.0.0.0/0"]
+  target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
 }
 
-resource "google_compute_firewall" "allow-internal" {
-  name    = "${var.cluster_name}-allow-internal"
+resource "google_compute_firewall" "allow-apiserver" {
+  name    = "${var.cluster_name}-allow-apiserver"
   network = "${google_compute_network.network.name}"
 
   allow {
     protocol = "tcp"
-    ports    = ["1-65535"]
+    ports    = [443]
   }
 
+  source_ranges = ["0.0.0.0/0"]
+  target_tags = ["${var.cluster_name}-controller"]
+}
+
+
+resource "google_compute_firewall" "allow-ingress" {
+  name    = "${var.cluster_name}-allow-ingress"
+  network = "${google_compute_network.network.name}"
+
   allow {
-    protocol = "udp"
-    ports    = ["1-65535"]
+    protocol = "tcp"
+    ports    = [80, 443]
   }
 
-  source_ranges = ["10.0.0.0/8"]
+  source_ranges = ["0.0.0.0/0"]
+  target_tags = ["${var.cluster_name}-worker"]
+}
+
+resource "google_compute_firewall" "internal-etcd" {
+  name    = "${var.cluster_name}-internal-etcd"
+  network = "${google_compute_network.network.name}"
+
+  allow {
+    protocol = "tcp"
+    ports    = [2380]
+  }
+
+  source_tags = ["${var.cluster_name}-controller"]
+  target_tags = ["${var.cluster_name}-controller"]
 }
 
 # Calico BGP and IPIP
 # https://docs.projectcalico.org/v2.5/reference/public-cloud/gce
-resource "google_compute_firewall" "allow-calico" {
+resource "google_compute_firewall" "internal-calico" {
   count = "${var.networking == "calico" ? 1 : 0}"
 
-  name    = "${var.cluster_name}-allow-calico"
+  name    = "${var.cluster_name}-internal-calico"
   network = "${google_compute_network.network.name}"
 
   allow {
@@ -62,5 +74,63 @@ resource "google_compute_firewall" "allow-calico" {
     protocol = "ipip"
   }
 
-  source_ranges = ["10.0.0.0/8"]
+  source_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+  target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+}
+
+# flannel
+resource "google_compute_firewall" "internal-flannel" {
+  count = "${var.networking == "flannel" ? 1 : 0}"
+
+  name    = "${var.cluster_name}-internal-flannel"
+  network = "${google_compute_network.network.name}"
+
+  allow {
+    protocol = "udp"
+    ports    = [8472]
+  }
+
+  source_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+  target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+}
+
+# Allow prometheus (workload) to scrape node-exporter daemonset
+resource "google_compute_firewall" "internal-node-exporter" {
+  name    = "${var.cluster_name}-internal-node-exporter"
+  network = "${google_compute_network.network.name}"
+
+  allow {
+    protocol = "tcp"
+    ports    = [9100]
+  }
+
+  source_tags = ["${var.cluster_name}-worker"]
+  target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+}
+
+# kubelet API to allow kubectl exec and log
+resource "google_compute_firewall" "internal-kubelet" {
+  name    = "${var.cluster_name}-internal-kubelet"
+  network = "${google_compute_network.network.name}"
+
+  allow {
+    protocol = "tcp"
+    ports    = [10250]
+  }
+
+  source_tags = ["${var.cluster_name}-controller"]
+  target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+}
+
+resource "google_compute_firewall" "internal-kubelet-readonly" {
+  name    = "${var.cluster_name}-internal-kubelet-readonly"
+  network = "${google_compute_network.network.name}"
+
+  allow {
+    protocol = "tcp"
+    ports    = [10255]
+  }
+
+  source_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
+  target_tags = ["${var.cluster_name}-controller", "${var.cluster_name}-worker"]
 }

google-cloud/container-linux/kubernetes/workers/workers.tf

@@ -67,7 +67,7 @@ resource "google_compute_instance_template" "worker" {
 
   can_ip_forward = true
 
-  tags = ["worker"]
+  tags = ["worker", "${var.cluster_name}-worker"]
 
   lifecycle {
     # To update an Instance Template, Terraform should replace the existing resource