feat(openshift): add mTLS for Prometheus metrics

Secure component metrics endpoints with mutual TLS on OpenShift.
Each reconciler syncs the Prometheus client CA bundle from
kube-system/extension-apiserver-authentication into the component
namespace as a metrics-client-ca ConfigMap.

OpenShift's serving-cert controller is triggered via annotation on
each metrics Service to provision a per-component TLS Secret.
Two new manifest transformers (InjectMetricsServingCert,
ApplyMetricsTLS) wire the Secret and ConfigMap as volumes and inject
METRICS_PROMETHEUS_TLS_* env vars so that the knative/pkg
prometheus.Server enables mTLS with require client auth.

ServiceMonitor resources are updated with scheme: https, scrapeClass
tls-client-certificate-auth, and tlsConfig.serverName. The existing
UpdateServiceMonitorTargetNamespace transformer is extended to also
patch the namespace segment inside serverName at runtime.

Relates-To: SRVKP-8172

Signed-off-by: Jawed khelil <jkhelil@redhat.com>
Assisted-by: Claude Sonnet 4.6 (via Cursor)
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: jkhelil

cmd/openshift/operator/kodata/openshift-monitoring/00-monitoring.yaml

@@ -58,8 +58,12 @@ metadata:
 spec:
   endpoints:
     - interval: 10s
-      port: http-metrics
+      port: https-metrics
       honorLabels: true
+      scheme: https
+      scrapeClass: tls-client-certificate-auth
+      tlsConfig:
+        serverName: tekton-pipelines-controller.openshift-pipelines.svc
   jobLabel: app
   namespaceSelector:
     matchNames:

cmd/openshift/operator/kodata/openshift-monitoring/01-trigger-monitoring.yaml

@@ -25,7 +25,11 @@ metadata:
 spec:
   endpoints:
     - interval: 10s
-      port: http-metrics
+      port: https-metrics
+      scheme: https
+      scrapeClass: tls-client-certificate-auth
+      tlsConfig:
+        serverName: tekton-triggers-controller.openshift-pipelines.svc
   jobLabel: app
   namespaceSelector:
     matchNames:

cmd/openshift/operator/kodata/openshift-monitoring/02-chains-monitoring.yaml

@@ -25,7 +25,11 @@ metadata:
 spec:
   endpoints:
     - interval: 10s
-      port: http-metrics
+      port: https-metrics
+      scheme: https
+      scrapeClass: tls-client-certificate-auth
+      tlsConfig:
+        serverName: tekton-chains-metrics.openshift-pipelines.svc
   jobLabel: app
   namespaceSelector:
     matchNames:

cmd/openshift/operator/kodata/openshift-monitoring/03-pipeline-webhook-monitoring.yaml

@@ -25,7 +25,11 @@ metadata:
 spec:
   endpoints:
     - interval: 10s
-      port: http-metrics
+      port: https-metrics
+      scheme: https
+      scrapeClass: tls-client-certificate-auth
+      tlsConfig:
+        serverName: tekton-pipelines-webhook.openshift-pipelines.svc
   jobLabel: app
   namespaceSelector:
     matchNames:

cmd/openshift/operator/kodata/openshift-monitoring/06-pruner-monitoring.yaml

@@ -25,7 +25,11 @@ metadata:
 spec:
   endpoints:
     - interval: 10s
-      port: http-metrics
+      port: https-metrics
+      scheme: https
+      scrapeClass: tls-client-certificate-auth
+      tlsConfig:
+        serverName: tekton-pruner-controller.openshift-pipelines.svc
   jobLabel: app
   namespaceSelector:
     matchNames:

pkg/reconciler/openshift/common/metricsca.go

@@ -0,0 +1,106 @@
+/*
+Copyright 2026 The Tekton Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package common
+
+import (
+	"context"
+	"fmt"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+	"knative.dev/pkg/logging"
+)
+
+const (
+	// MetricsClientCAConfigMap is the name of the ConfigMap synced into each
+	// component namespace so that the Prometheus metrics server can verify
+	// the client certificate presented by Prometheus during mTLS scraping.
+	MetricsClientCAConfigMap = "metrics-client-ca"
+
+	// MetricsClientCAKey is the data key within MetricsClientCAConfigMap that
+	// holds the PEM-encoded CA bundle.
+	MetricsClientCAKey = "client-ca-file"
+
+	// SourceConfigMapName is the authoritative ConfigMap in kube-system that
+	// contains the Prometheus client CA bundle on OpenShift.
+	SourceConfigMapName = "extension-apiserver-authentication"
+	SystemNamespace     = "kube-system"
+)
+
+// EnsureMetricsClientCA reads the Prometheus client CA from
+// kube-system/extension-apiserver-authentication and creates-or-updates
+// the metrics-client-ca ConfigMap in targetNamespace.
+//
+// The ConfigMap is mounted by Tekton component containers so that the
+// knative prometheus.Server can verify the Prometheus client certificate
+// during mTLS scraping (METRICS_PROMETHEUS_TLS_CLIENT_CA_FILE).
+func EnsureMetricsClientCA(ctx context.Context, kubeClient kubernetes.Interface, targetNamespace string) error {
+	logger := logging.FromContext(ctx)
+
+	src, err := kubeClient.CoreV1().ConfigMaps(SystemNamespace).Get(
+		ctx, SourceConfigMapName, metav1.GetOptions{})
+	if err != nil {
+		return fmt.Errorf("reading %s/%s: %w", SystemNamespace, SourceConfigMapName, err)
+	}
+
+	caBundle, ok := src.Data[MetricsClientCAKey]
+	if !ok {
+		return fmt.Errorf("%s/%s has no %q key", SystemNamespace, SourceConfigMapName, MetricsClientCAKey)
+	}
+
+	cmClient := kubeClient.CoreV1().ConfigMaps(targetNamespace)
+
+	existing, err := cmClient.Get(ctx, MetricsClientCAConfigMap, metav1.GetOptions{})
+	if err != nil && !errors.IsNotFound(err) {
+		return fmt.Errorf("getting %s/%s: %w", targetNamespace, MetricsClientCAConfigMap, err)
+	}
+
+	if errors.IsNotFound(err) {
+		logger.Infof("Creating %s/%s", targetNamespace, MetricsClientCAConfigMap)
+		desired := &corev1.ConfigMap{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      MetricsClientCAConfigMap,
+				Namespace: targetNamespace,
+				Labels: map[string]string{
+					"app.kubernetes.io/part-of": "tekton-pipelines",
+				},
+			},
+			Data: map[string]string{
+				MetricsClientCAKey: caBundle,
+			},
+		}
+		_, err = cmClient.Create(ctx, desired, metav1.CreateOptions{})
+		return err
+	}
+
+	// Already exists — update only if the CA bundle has changed.
+	if existing.Data[MetricsClientCAKey] == caBundle {
+		logger.Debugf("%s/%s is up to date", targetNamespace, MetricsClientCAConfigMap)
+		return nil
+	}
+
+	logger.Infof("Updating %s/%s (CA bundle changed)", targetNamespace, MetricsClientCAConfigMap)
+	updated := existing.DeepCopy()
+	if updated.Data == nil {
+		updated.Data = map[string]string{}
+	}
+	updated.Data[MetricsClientCAKey] = caBundle
+	_, err = cmClient.Update(ctx, updated, metav1.UpdateOptions{})
+	return err
+}