Remove dependency on kube-rbac-proxy by adopting controller-runtime's native authn/authz for metrics

cmd/ironcore-controller-manager/main.go

@@ -4,9 +4,11 @@
 package main
 
 import (
+	"crypto/tls"
 	"flag"
 	"fmt"
 	"os"
+	"path/filepath"
 	"time"
 
 	corev1alpha1 "github.com/ironcore-dev/ironcore/api/core/v1alpha1"
@@ -28,6 +30,8 @@ import (
 	quotaevaluatorironcore "github.com/ironcore-dev/ironcore/internal/quota/evaluator/ironcore"
 	"github.com/ironcore-dev/ironcore/utils/quota"
 	"k8s.io/utils/lru"
+	"sigs.k8s.io/controller-runtime/pkg/certwatcher"
+	"sigs.k8s.io/controller-runtime/pkg/metrics/filters"
 	metricsserver "sigs.k8s.io/controller-runtime/pkg/metrics/server"
 
 	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
@@ -100,13 +104,26 @@ func init() {
 
 func main() {
 	var metricsAddr string
+	var secureMetrics bool
+	var metricsCertPath, metricsCertName, metricsCertKey string
+	var enableHTTP2 bool
 	var enableLeaderElection bool
 	var probeAddr string
 	var prefixAllocationTimeout time.Duration
 	var volumeBindTimeout time.Duration
 	var virtualIPBindTimeout time.Duration
 	var networkInterfaceBindTimeout time.Duration
-	flag.StringVar(&metricsAddr, "metrics-bind-address", ":8080", "The address the metric endpoint binds to.")
+	var tlsOpts []func(*tls.Config)
+	flag.StringVar(&metricsAddr, "metrics-bind-address", "0", "The address the metrics endpoint binds to. "+
+		"Use :8443 for HTTPS or :8080 for HTTP, or leave as 0 to disable the metrics service.")
+	flag.BoolVar(&secureMetrics, "metrics-secure", true,
+		"If set, the metrics endpoint is served securely via HTTPS. Use --metrics-secure=false to use HTTP instead.")
+	flag.StringVar(&metricsCertPath, "metrics-cert-path", "",
+		"The directory that contains the metrics server certificate.")
+	flag.StringVar(&metricsCertName, "metrics-cert-name", "tls.crt", "The name of the metrics server certificate file.")
+	flag.StringVar(&metricsCertKey, "metrics-cert-key", "tls.key", "The name of the metrics server key file.")
+	flag.BoolVar(&enableHTTP2, "enable-http2", false,
+		"If set, HTTP/2 will be enabled for the metrics server")
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
 	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
 		"Enable leader election for controller manager. "+
@@ -166,10 +183,74 @@ func main() {
 	ctrl.SetLogger(logger)
 	ctx := ctrl.SetupSignalHandler()
 
+	// if the enable-http2 flag is false (the default), http/2 should be disabled
+	// due to its vulnerabilities. More specifically, disabling http/2 will
+	// prevent from being vulnerable to the HTTP/2 Stream Cancellation and
+	// Rapid Reset CVEs. For more information see:
+	// - https://github.com/advisories/GHSA-qppj-fm5r-hxr3
+	// - https://github.com/advisories/GHSA-4374-p667-p6c8
+	disableHTTP2 := func(c *tls.Config) {
+		setupLog.Info("disabling http/2")
+		c.NextProtos = []string{"http/1.1"}
+	}
+
+	if !enableHTTP2 {
+		tlsOpts = append(tlsOpts, disableHTTP2)
+	}
+
+	// Metrics endpoint is enabled in 'config/controller/default/kustomization.yaml'. The Metrics options configure the server.
+	// More info:
+	// - https://pkg.go.dev/sigs.k8s.io/[email protected]/pkg/metrics/server
+	// - https://book.kubebuilder.io/reference/metrics.html
+	metricsServerOptions := metricsserver.Options{
+		BindAddress:   metricsAddr,
+		SecureServing: secureMetrics,
+		TLSOpts:       tlsOpts,
+	}
+
+	if secureMetrics {
+		// FilterProvider is used to protect the metrics endpoint with authn/authz.
+		// These configurations ensure that only authorized users and service accounts
+		// can access the metrics endpoint. The RBAC are configured in 'config/controller/rbac/kustomization.yaml'. More info:
+		// https://pkg.go.dev/sigs.k8s.io/[email protected]/pkg/metrics/filters#WithAuthenticationAndAuthorization
+		metricsServerOptions.FilterProvider = filters.WithAuthenticationAndAuthorization
+	}
+
+	// If the certificate is not specified, controller-runtime will automatically
+	// generate self-signed certificates for the metrics server. While convenient for development and testing,
+	// this setup is not recommended for production.
+	//
+	// TODO(user): If you enable certManager, uncomment the following lines:
+	// - [METRICS-WITH-CERTS] at config/controller/default/kustomization.yaml to generate and use certificates
+	// managed by cert-manager for the metrics server.
+	// - [PROMETHEUS-WITH-CERTS] at config/controller/prometheus/kustomization.yaml for TLS certification.
+
+	// Create watchers for metrics certificates
+	var metricsCertWatcher *certwatcher.CertWatcher
+
+	if len(metricsCertPath) > 0 {
+		setupLog.Info("Initializing metrics certificate watcher using provided certificates",
+			"metrics-cert-path", metricsCertPath, "metrics-cert-name", metricsCertName, "metrics-cert-key", metricsCertKey)
+
+		var err error
+		metricsCertWatcher, err = certwatcher.New(
+			filepath.Join(metricsCertPath, metricsCertName),
+			filepath.Join(metricsCertPath, metricsCertKey),
+		)
+		if err != nil {
+			setupLog.Error(err, "to initialize metrics certificate watcher", "error", err)
+			os.Exit(1)
+		}
+
+		metricsServerOptions.TLSOpts = append(metricsServerOptions.TLSOpts, func(config *tls.Config) {
+			config.GetCertificate = metricsCertWatcher.GetCertificate
+		})
+	}
+
 	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
 		Logger:                 logger,
 		Scheme:                 scheme,
-		Metrics:                metricsserver.Options{BindAddress: metricsAddr},
+		Metrics:                metricsServerOptions,
 		HealthProbeBindAddress: probeAddr,
 		LeaderElection:         enableLeaderElection,
 		LeaderElectionID:       "d0ae00be.ironcore.dev",
@@ -179,6 +260,14 @@ func main() {
 		os.Exit(1)
 	}
 
+	if metricsCertWatcher != nil {
+		setupLog.Info("Adding metrics certificate watcher to manager")
+		if err := mgr.Add(metricsCertWatcher); err != nil {
+			setupLog.Error(err, "unable to add metrics certificate watcher to manager")
+			os.Exit(1)
+		}
+	}
+
 	// Register controllers
 
 	// compute controllers

config/apiserver/certmanager/certificate.yaml

@@ -14,10 +14,10 @@ kind: Certificate
 metadata:
   name: apiserver-cert  # this name should match the one appeared in kustomizeconfig.yaml
   namespace: system
-spec: # $(SERVICE_NAME) and $(SERVICE_NAMESPACE) will be substituted by kustomize
+spec: # SERVICE_NAME and SERVICE_NAMESPACE will be substituted by kustomize
   dnsNames:
-    - $(SERVICE_NAME).$(SERVICE_NAMESPACE).svc
-    - $(SERVICE_NAME).$(SERVICE_NAMESPACE).svc.cluster.local
+    - SERVICE_NAME.SERVICE_NAMESPACE.svc
+    - SERVICE_NAME.SERVICE_NAMESPACE.svc.cluster.local
   issuerRef:
     kind: Issuer
     name: apiserver-selfsigned-issuer

config/apiserver/default/kustomization.yaml

@@ -9,8 +9,10 @@ namespace: ironcore-system
 namePrefix: ironcore-
 
 # Labels to add to all resources and selectors.
-#commonLabels:
-#  someName: someValue
+#labels:
+#- includeSelectors: true
+#  pairs:
+#    someName: someValue
 
 resources:
   - ../rbac

config/apiserver/etcdless/kustomization.yaml

@@ -9,8 +9,10 @@ namespace: ironcore-system
 namePrefix: ironcore-
 
 # Labels to add to all resources and selectors.
-#commonLabels:
-#  someName: someValue
+#labels:
+#- includeSelectors: true
+#  pairs:
+#    someName: someValue
 
 resources:
   - ../rbac

config/bucketpoollet-broker/broker-rbac/kustomization.yaml

@@ -10,10 +10,13 @@ resources: # All RBAC will be applied under this service account in
   - cluster_role_binding.yaml
   - leader_election_role.yaml
   - leader_election_role_binding.yaml
-  # Comment the following 4 lines if you want to disable
-  # the auth proxy (https://github.com/brancz/kube-rbac-proxy)
-  # which protects your /metrics endpoint.
-  - auth_proxy_service.yaml
-  - auth_proxy_role.yaml
-  - auth_proxy_role_binding.yaml
-  - auth_proxy_client_clusterrole.yaml
+  # The following RBAC configurations are used to protect
+  # the metrics endpoint with authn/authz. These configurations
+  # ensure that only authorized users and service accounts
+  # can access the metrics endpoint. Comment the following
+  # permissions if you want to disable this protection.
+  # More info: https://book.kubebuilder.io/reference/metrics.html
+  - metrics_service.yaml
+  - metrics_auth_role.yaml
+  - metrics_auth_role_binding.yaml
+  - metrics_reader_role.yaml

config/bucketpoollet-broker/broker-rbac/auth_proxy_role.yaml → config/bucketpoollet-broker/broker-rbac/metrics_auth_role.yaml

@@ -1,7 +1,7 @@
 apiVersion: rbac.authorization.k8s.io/v1
 kind: ClusterRole
 metadata:
-  name: proxy-role
+  name: metrics-auth-role
 rules:
 - apiGroups:
   - authentication.k8s.io

config/machinepoollet-broker/broker-rbac/auth_proxy_role_binding.yaml → config/bucketpoollet-broker/broker-rbac/metrics_auth_role_binding.yaml

@@ -1,11 +1,11 @@
 apiVersion: rbac.authorization.k8s.io/v1
 kind: ClusterRoleBinding
 metadata:
-  name: proxy-rolebinding
+  name: metrics-auth-rolebinding
 roleRef:
   apiGroup: rbac.authorization.k8s.io
   kind: ClusterRole
-  name: proxy-role
+  name: metrics-auth-role
 subjects:
 - kind: ServiceAccount
   name: controller-manager

config/machinepoollet-broker/broker-rbac/auth_proxy_service.yaml → config/bucketpoollet-broker/broker-rbac/metrics_service.yaml

@@ -9,6 +9,7 @@ spec:
   ports:
   - name: https
     port: 8443
-    targetPort: https
+    protocol: TCP 
+    targetPort: 8443
   selector:
     control-plane: controller-manager

config/machinepoollet-broker/certmanager/certificate.yaml → config/bucketpoollet-broker/certmanager/certificate-metrics.yaml

@@ -12,13 +12,13 @@ spec:
 apiVersion: cert-manager.io/v1
 kind: Certificate
 metadata:
-  name: serving-cert  # this name should match the one appeared in kustomizeconfig.yaml
+  name: metrics-certs  # this name should match the one appeared in kustomizeconfig.yaml
   namespace: system
-spec: # $(SERVICE_NAME) and $(SERVICE_NAMESPACE) will be substituted by kustomize
+spec: # SERVICE_NAME and SERVICE_NAMESPACE will be substituted by kustomize
   dnsNames:
-    - $(SERVICE_NAME).$(SERVICE_NAMESPACE).svc
-    - $(SERVICE_NAME).$(SERVICE_NAMESPACE).svc.cluster.local
+    - SERVICE_NAME.SERVICE_NAMESPACE.svc
+    - SERVICE_NAME.SERVICE_NAMESPACE.svc.cluster.local
   issuerRef:
     kind: Issuer
     name: selfsigned-issuer
-  secretName: webhook-server-cert # this secret will not be prefixed, since it's not managed by kustomize
+  secretName: metrics-server-cert # this secret will not be prefixed, since it's not managed by kustomize

config/bucketpoollet-broker/certmanager/kustomization.yaml

@@ -1,5 +1,5 @@
 resources:
-- certificate.yaml
+- certificate-metrics.yaml
 
 configurations:
 - kustomizeconfig.yaml

config/bucketpoollet-broker/default/cert_metrics_manager_patch.yaml

@@ -0,0 +1,30 @@
+# This patch adds the args, volumes, and ports to allow the manager to use the metrics-server certs.
+
+# Add the volumeMount for the metrics-server certs
+- op: add
+  path: /spec/template/spec/containers/0/volumeMounts/-
+  value:
+    mountPath: /tmp/k8s-metrics-server/metrics-certs
+    name: metrics-certs
+    readOnly: true
+
+# Add the --metrics-cert-path argument for the metrics server
+- op: add
+  path: /spec/template/spec/containers/0/args/-
+  value: --metrics-cert-path=/tmp/k8s-metrics-server/metrics-certs
+
+# Add the metrics-server certs volume configuration
+- op: add
+  path: /spec/template/spec/volumes/-
+  value:
+    name: metrics-certs
+    secret:
+      secretName: metrics-server-cert
+      optional: false
+      items:
+        - key: ca.crt
+          path: ca.crt
+        - key: tls.crt
+          path: tls.crt
+        - key: tls.key
+          path: tls.key