Add Patch to give optional option to enable ServiceMonitor to use cer…

…t-manager-managed serving-cert with TLS verification

Adds a patch to configure ServiceMonitor with  `insecureSkipVerify: false`  to ensure TLS verification using cert-manager certificates. Updates documentation and corrects misaligned comments.

docs/book/src/cronjob-tutorial/testdata/project/cmd/main.go

@@ -123,16 +123,16 @@ func main() {
 	metricsServerOptions := metricsserver.Options{
 		BindAddress:   metricsAddr,
 		SecureServing: secureMetrics,
-		// TODO(user): TLSOpts is used to allow configuring the TLS config used for the server. If certificates are
-		// not provided, self-signed certificates will be generated by default. This option is not recommended for
-		// production environments as self-signed certificates do not offer the same level of trust and security
-		// as certificates issued by a trusted Certificate Authority (CA). The primary risk is potentially allowing
-		// unauthorized access to sensitive metrics data. Consider replacing with CertDir, CertName, and KeyName
-		// to provide certificates, ensuring the server communicates using trusted and secure certificates.
-		TLSOpts: tlsOpts,
+		TLSOpts:       tlsOpts,
 	}
 
 	if secureMetrics {
+		// TODO(user): If cert-manager is enabled in config/default/kustomization.yaml,
+		// you can uncomment the following lines to use the certificate managed by cert-manager.
+		// metricsServerOptions.CertDir = "/var/run/secrets/kubernetes.io/certs"
+		// metricsServerOptions.CertName = "tls.crt"
+		// metricsServerOptions.KeyName = "tls.key"
+
 		// 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/rbac/kustomization.yaml'. More info:

docs/book/src/cronjob-tutorial/testdata/project/config/prometheus/kustomization.yaml

@@ -1,2 +1,11 @@
 resources:
 - monitor.yaml
+
+# [PROMETHEUS WITH CERTMANAGER] The following patch configures the ServiceMonitor in ../prometheus
+# to securely reference certificates created and managed by cert-manager.
+# Additionally, ensure that you uncomment the [WEBHOOK] patch under config/default/kustomization.yaml
+# to mount the "serving-cert" secret in the Manager Deployment.
+#patches:
+#  - path: monitor_tls_patch.yaml
+#    target:
+#      kind: ServiceMonitor

docs/book/src/cronjob-tutorial/testdata/project/config/prometheus/monitor.yaml

@@ -16,14 +16,10 @@ spec:
       bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
       tlsConfig:
         # TODO(user): The option insecureSkipVerify: true is not recommended for production since it disables
-        # certificate verification. This poses a significant security risk by making the system vulnerable to
-        # man-in-the-middle attacks, where an attacker could intercept and manipulate the communication between
-        # Prometheus and the monitored services. This could lead to unauthorized access to sensitive metrics data,
-        # compromising the integrity and confidentiality of the information.
-        # Please use the following options for secure configurations:
-        # caFile: /etc/metrics-certs/ca.crt
-        # certFile: /etc/metrics-certs/tls.crt
-        # keyFile: /etc/metrics-certs/tls.key
+        # certificate verification, exposing the system to potential man-in-the-middle attacks.
+        # For production environments, it is recommended to use cert-manager for automatic TLS certificate management.
+        # To apply this configuration, enable cert-manager and use the patch located at config/prometheus/servicemonitor_tls_patch.yaml,
+        # which securely references the certificate from the 'serving-cert' secret.
         insecureSkipVerify: true
   selector:
     matchLabels:

docs/book/src/cronjob-tutorial/testdata/project/config/prometheus/monitor_tls_patch.yaml

@@ -0,0 +1,22 @@
+# Patch for Prometheus ServiceMonitor to enable secure TLS configuration
+# using certificates managed by cert-manager
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: controller-manager-metrics-monitor
+  namespace: system
+spec:
+  endpoints:
+    - tlsConfig:
+        insecureSkipVerify: false
+        ca:
+          secret:
+            name: serving-cert
+            key: ca.crt
+        cert:
+          secret:
+            name: serving-cert
+            key: tls.crt
+        keySecret:
+          name: serving-cert
+          key: tls.key

docs/book/src/getting-started/testdata/project/cmd/main.go

@@ -103,16 +103,16 @@ func main() {
 	metricsServerOptions := metricsserver.Options{
 		BindAddress:   metricsAddr,
 		SecureServing: secureMetrics,
-		// TODO(user): TLSOpts is used to allow configuring the TLS config used for the server. If certificates are
-		// not provided, self-signed certificates will be generated by default. This option is not recommended for
-		// production environments as self-signed certificates do not offer the same level of trust and security
-		// as certificates issued by a trusted Certificate Authority (CA). The primary risk is potentially allowing
-		// unauthorized access to sensitive metrics data. Consider replacing with CertDir, CertName, and KeyName
-		// to provide certificates, ensuring the server communicates using trusted and secure certificates.
-		TLSOpts: tlsOpts,
+		TLSOpts:       tlsOpts,
 	}
 
 	if secureMetrics {
+		// TODO(user): If cert-manager is enabled in config/default/kustomization.yaml,
+		// you can uncomment the following lines to use the certificate managed by cert-manager.
+		// metricsServerOptions.CertDir = "/var/run/secrets/kubernetes.io/certs"
+		// metricsServerOptions.CertName = "tls.crt"
+		// metricsServerOptions.KeyName = "tls.key"
+
 		// 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/rbac/kustomization.yaml'. More info:

docs/book/src/getting-started/testdata/project/config/prometheus/kustomization.yaml

@@ -1,2 +1,11 @@
 resources:
 - monitor.yaml
+
+# [PROMETHEUS WITH CERTMANAGER] The following patch configures the ServiceMonitor in ../prometheus
+# to securely reference certificates created and managed by cert-manager.
+# Additionally, ensure that you uncomment the [WEBHOOK] patch under config/default/kustomization.yaml
+# to mount the "serving-cert" secret in the Manager Deployment.
+#patches:
+#  - path: monitor_tls_patch.yaml
+#    target:
+#      kind: ServiceMonitor

docs/book/src/getting-started/testdata/project/config/prometheus/monitor.yaml

@@ -16,14 +16,10 @@ spec:
       bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
       tlsConfig:
         # TODO(user): The option insecureSkipVerify: true is not recommended for production since it disables
-        # certificate verification. This poses a significant security risk by making the system vulnerable to
-        # man-in-the-middle attacks, where an attacker could intercept and manipulate the communication between
-        # Prometheus and the monitored services. This could lead to unauthorized access to sensitive metrics data,
-        # compromising the integrity and confidentiality of the information.
-        # Please use the following options for secure configurations:
-        # caFile: /etc/metrics-certs/ca.crt
-        # certFile: /etc/metrics-certs/tls.crt
-        # keyFile: /etc/metrics-certs/tls.key
+        # certificate verification, exposing the system to potential man-in-the-middle attacks.
+        # For production environments, it is recommended to use cert-manager for automatic TLS certificate management.
+        # To apply this configuration, enable cert-manager and use the patch located at config/prometheus/servicemonitor_tls_patch.yaml,
+        # which securely references the certificate from the 'serving-cert' secret.
         insecureSkipVerify: true
   selector:
     matchLabels:

docs/book/src/getting-started/testdata/project/config/prometheus/monitor_tls_patch.yaml

@@ -0,0 +1,22 @@
+# Patch for Prometheus ServiceMonitor to enable secure TLS configuration
+# using certificates managed by cert-manager
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: controller-manager-metrics-monitor
+  namespace: system
+spec:
+  endpoints:
+    - tlsConfig:
+        insecureSkipVerify: false
+        ca:
+          secret:
+            name: serving-cert
+            key: ca.crt
+        cert:
+          secret:
+            name: serving-cert
+            key: tls.crt
+        keySecret:
+          name: serving-cert
+          key: tls.key

docs/book/src/multiversion-tutorial/testdata/project/cmd/main.go

@@ -122,16 +122,16 @@ func main() {
 	metricsServerOptions := metricsserver.Options{
 		BindAddress:   metricsAddr,
 		SecureServing: secureMetrics,
-		// TODO(user): TLSOpts is used to allow configuring the TLS config used for the server. If certificates are
-		// not provided, self-signed certificates will be generated by default. This option is not recommended for
-		// production environments as self-signed certificates do not offer the same level of trust and security
-		// as certificates issued by a trusted Certificate Authority (CA). The primary risk is potentially allowing
-		// unauthorized access to sensitive metrics data. Consider replacing with CertDir, CertName, and KeyName
-		// to provide certificates, ensuring the server communicates using trusted and secure certificates.
-		TLSOpts: tlsOpts,
+		TLSOpts:       tlsOpts,
 	}
 
 	if secureMetrics {
+		// TODO(user): If cert-manager is enabled in config/default/kustomization.yaml,
+		// you can uncomment the following lines to use the certificate managed by cert-manager.
+		// metricsServerOptions.CertDir = "/var/run/secrets/kubernetes.io/certs"
+		// metricsServerOptions.CertName = "tls.crt"
+		// metricsServerOptions.KeyName = "tls.key"
+
 		// 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/rbac/kustomization.yaml'. More info:

docs/book/src/multiversion-tutorial/testdata/project/config/prometheus/kustomization.yaml

@@ -1,2 +1,11 @@
 resources:
 - monitor.yaml
+
+# [PROMETHEUS WITH CERTMANAGER] The following patch configures the ServiceMonitor in ../prometheus
+# to securely reference certificates created and managed by cert-manager.
+# Additionally, ensure that you uncomment the [WEBHOOK] patch under config/default/kustomization.yaml
+# to mount the "serving-cert" secret in the Manager Deployment.
+#patches:
+#  - path: monitor_tls_patch.yaml
+#    target:
+#      kind: ServiceMonitor

docs/book/src/multiversion-tutorial/testdata/project/config/prometheus/monitor.yaml

@@ -16,14 +16,10 @@ spec:
       bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
       tlsConfig:
         # TODO(user): The option insecureSkipVerify: true is not recommended for production since it disables
-        # certificate verification. This poses a significant security risk by making the system vulnerable to
-        # man-in-the-middle attacks, where an attacker could intercept and manipulate the communication between
-        # Prometheus and the monitored services. This could lead to unauthorized access to sensitive metrics data,
-        # compromising the integrity and confidentiality of the information.
-        # Please use the following options for secure configurations:
-        # caFile: /etc/metrics-certs/ca.crt
-        # certFile: /etc/metrics-certs/tls.crt
-        # keyFile: /etc/metrics-certs/tls.key
+        # certificate verification, exposing the system to potential man-in-the-middle attacks.
+        # For production environments, it is recommended to use cert-manager for automatic TLS certificate management.
+        # To apply this configuration, enable cert-manager and use the patch located at config/prometheus/servicemonitor_tls_patch.yaml,
+        # which securely references the certificate from the 'serving-cert' secret.
         insecureSkipVerify: true
   selector:
     matchLabels:

docs/book/src/multiversion-tutorial/testdata/project/config/prometheus/monitor_tls_patch.yaml

@@ -0,0 +1,22 @@
+# Patch for Prometheus ServiceMonitor to enable secure TLS configuration
+# using certificates managed by cert-manager
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: controller-manager-metrics-monitor
+  namespace: system
+spec:
+  endpoints:
+    - tlsConfig:
+        insecureSkipVerify: false
+        ca:
+          secret:
+            name: serving-cert
+            key: ca.crt
+        cert:
+          secret:
+            name: serving-cert
+            key: tls.crt
+        keySecret:
+          name: serving-cert
+          key: tls.key

docs/book/src/reference/metrics.md

@@ -136,40 +136,16 @@ spec:
 <aside class="warning">
 <h1>Changes Recommended for Production</h1>
 
-The default scaffold to configure the metrics server in `cmd/main.go` uses `TLSOpts` that rely on self-signed certificates
-(SelfCerts), which are generated automatically. However, self-signed certificates are **not** recommended for production
-environments as they do not offer the same level of trust and security as certificates issued by a trusted
-Certificate Authority (CA).
+The default scaffold in `cmd/main.go` uses a **controller-runtime feature**
+to generate a certificate for securing the metrics server. While convenient
+for development and testing, this setup is **not recommended for production**.
 
-While self-signed certificates are convenient for development and testing, they are unsuitable for production
-because they do not establish a chain of trust, making them vulnerable to security threats.
+Additionally, review the configuration file at `config/prometheus/monitor.yaml`
+to ensure secure integration with Prometheus. If `insecureSkipVerify: true` is
+enabled, certificate verification is turned off. **This is not recommended for production**
+as it exposes the system to man-in-the-middle attacks, potentially allowing
+unauthorized access to metrics data.
 
-Furthermore, check the configuration file located at `config/prometheus/monitor.yaml` to
-ensure secure integration with Prometheus. If the `insecureSkipVerify: true` option is enabled,
-it means that certificate verification is turned off. This is **not** recommended for production as
-it poses a significant security risk by making the system vulnerable to man-in-the-middle attacks,
-where an attacker could intercept and manipulate the communication between Prometheus and the monitored services.
-This could lead to unauthorized access to metrics data, compromising the integrity and confidentiality of the information.
-
-**In both cases, the primary risk is potentially allowing unauthorized access to sensitive metrics data.**
-
-### Recommended Actions for a Secure Production Setup
-
-1. **Replace Self-Signed Certificates:**
-   - Instead of using `TLSOpts`, configure the `CertDir`, `CertName`, and `KeyName` options to use your own certificates.
-   This ensures that your server communicates using trusted and secure certificates.
-
-2. **Configure Prometheus Monitoring Securely:**
-   - Check and update your Prometheus configuration file (`config/prometheus/monitor.yaml`) to ensure secure settings.
-   - Replace `insecureSkipVerify: true` with the following secure options:
-
-     ```yaml
-     caFile: The path to the CA certificate file, e.g., /etc/metrics-certs/ca.crt.
-     certFile: The path to the client certificate file, e.g., /etc/metrics-certs/tls.crt.
-     keyFile: The path to the client key file, e.g., /etc/metrics-certs/tls.key.
-     ```
-
-   These settings ensure encrypted and authenticated communication between Prometheus and the monitored services, providing a secure monitoring setup.
 </aside>
 
 <aside class="note">
@@ -187,6 +163,48 @@ An [issue](https://github.com/kubernetes-sigs/controller-runtime/issues/2781) ha
 enhance the controller-runtime and address these considerations.
 </aside>
 
+### By exposing the metrics endpoint using HTTPS and Cert-Manager
+
+Integrating `cert-manager` with your metrics service enables secure
+HTTPS access via TLS encryption. Follow the steps below to configure
+your project to expose the metrics endpoint using HTTPS with cert-manager.
+
+1. **Enable Cert-Manager in `config/default/kustomization.yaml`:**
+    - Uncomment the cert-manager resource to include it in your project:
+
+      ```yaml
+      - ../certmanager
+      ```
+
+2. **Enable the Patch for the `ServiceMonitor` to Use the Cert-Manager-Managed Secret `config/prometheus/kustomization.yaml`:**
+    - Add or uncomment the `ServiceMonitor` patch to securely reference the cert-manager-managed secret, replacing insecure configurations with secure certificate verification:
+
+      ```yaml
+      - path: monitor_tls_patch.yaml
+        target:
+          kind: ServiceMonitor
+      ```
+
+3. **Enable the Patch to Mount the Cert-Manager-Managed Secret in the Controller Deployment in `config/default/kustomization.yaml`:**
+    - Use the `manager_webhook_patch.yaml` (or create a custom metrics patch) to mount the `serving-cert` secret in the Manager Deployment.
+
+      ```yaml
+      - path: manager_webhook_patch.yaml
+      ```
+
+4. **Update `cmd/main.go` to Use the Certificate Managed by Cert-Manager:**
+    - Modify `cmd/main.go` to configure the metrics server to use the cert-manager-managed certificates.
+   Uncomment the lines for `CertDir`, `CertName`, and `KeyName`:
+
+      ```go
+      if secureMetrics {
+          // TODO(user): If cert-manager is enabled under config/default/kustomization.yaml, you can uncomment the following
+          // lines to use the certificate managed by cert-manager, mounted as a Kubernetes secret named 'serving-cert'.
+          // metricsServerOptions.CertDir = "/var/run/secrets/kubernetes.io/certs"
+          // metricsServerOptions.CertName = "tls.crt"
+          // metricsServerOptions.KeyName = "tls.key"
+      }
+      ```
 
 ### By using Network Policy (You can optionally enable)
 
@@ -202,16 +220,6 @@ Uncomment the following line in the `config/default/kustomization.yaml`:
 #- ../network-policy
 ```
 
-### By exposing the metrics endpoint using HTTPS and CertManager
-
-Integrating `cert-manager` with your metrics service can secure the endpoint via TLS encryption.
-
-To modify your project setup to expose metrics using HTTPS with
-the help of cert-manager, you'll need to change the configuration of both
-the `Service` under `config/default/metrics_service.yaml` and
-the `ServiceMonitor` under `config/prometheus/monitor.yaml` to use a secure HTTPS port
-and ensure the necessary certificate is applied.
-
 ## Exporting Metrics for Prometheus
 
 Follow the steps below to export the metrics using the Prometheus Operator:

pkg/plugins/common/kustomize/v2/scaffolds/init.go

@@ -84,6 +84,7 @@ func (s *initScaffolder) Scaffold() error {
 		&network_policy.NetworkPolicyAllowMetrics{},
 		&prometheus.Kustomization{},
 		&prometheus.Monitor{},
+		&prometheus.ServiceMonitorPatch{},
 	}
 
 	return scaffold.Execute(templates...)

pkg/plugins/common/kustomize/v2/scaffolds/internal/templates/config/prometheus/kustomization.go

@@ -42,4 +42,13 @@ func (f *Kustomization) SetTemplateDefaults() error {
 
 const kustomizationTemplate = `resources:
 - monitor.yaml
+
+# [PROMETHEUS WITH CERTMANAGER] The following patch configures the ServiceMonitor in ../prometheus
+# to securely reference certificates created and managed by cert-manager.
+# Additionally, ensure that you uncomment the [WEBHOOK] patch under config/default/kustomization.yaml
+# to mount the "serving-cert" secret in the Manager Deployment.
+#patches:
+#  - path: monitor_tls_patch.yaml
+#    target:
+#      kind: ServiceMonitor
 `

pkg/plugins/common/kustomize/v2/scaffolds/internal/templates/config/prometheus/monitor.go

@@ -41,6 +41,7 @@ func (f *Monitor) SetTemplateDefaults() error {
 	return nil
 }
 
+// nolint:lll
 const serviceMonitorTemplate = `# Prometheus Monitor Service (Metrics)
 apiVersion: monitoring.coreos.com/v1
 kind: ServiceMonitor
@@ -59,14 +60,10 @@ spec:
       bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
       tlsConfig:
         # TODO(user): The option insecureSkipVerify: true is not recommended for production since it disables
-        # certificate verification. This poses a significant security risk by making the system vulnerable to
-        # man-in-the-middle attacks, where an attacker could intercept and manipulate the communication between
-        # Prometheus and the monitored services. This could lead to unauthorized access to sensitive metrics data,
-        # compromising the integrity and confidentiality of the information.
-        # Please use the following options for secure configurations:
-        # caFile: /etc/metrics-certs/ca.crt
-        # certFile: /etc/metrics-certs/tls.crt
-        # keyFile: /etc/metrics-certs/tls.key
+        # certificate verification, exposing the system to potential man-in-the-middle attacks.
+        # For production environments, it is recommended to use cert-manager for automatic TLS certificate management.
+        # To apply this configuration, enable cert-manager and use the patch located at config/prometheus/servicemonitor_tls_patch.yaml,
+        # which securely references the certificate from the 'serving-cert' secret.
         insecureSkipVerify: true
   selector:
     matchLabels: