feat(service-monitor): support bearer token authentication on metrics endpoint (#719)

### Benefits

Can protect metrics endpoint with `Bearer` token authentication provided by gitea.
see PR #637 for previous discussion.

### Possible drawbacks

No possible drawbacks

### Applicable issues

- fixes #635

### Additional information

```
gitea:
  metrics:
    enabled: true
    token: "somepassword"
    serviceMonitor:
      enabled: true
```

Using above configuration is sufficient to secure /metrics endpoint with bearer token and corresponding ServiceMonitor.

### Checklist

- [x] Parameters are documented in the `values.yaml` and added to the `README.md` using [readme-generator-for-helm](https://github.com/bitnami-labs/readme-generator-for-helm)
- [ ] ~~Breaking changes are documented in the `README.md`~~ Not applicable
- [x] Templating unittests are added

Signed-off-by: Hitesh Nayak <hiteshnayak305@gmail.com>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/719
Reviewed-by: justusbunsi <justusbunsi@noreply.gitea.com>
Co-authored-by: Hitesh Nayak <hiteshnayak305@gmail.com>
Co-committed-by: Hitesh Nayak <hiteshnayak305@gmail.com>

README.md

@@ -30,6 +30,7 @@
   - [OAuth2 Settings](#oauth2-settings)
 - [Configure commit signing](#configure-commit-signing)
 - [Metrics and profiling](#metrics-and-profiling)
+  - [Secure Metrics Endpoint](#secure-metrics-endpoint)
 - [Pod annotations](#pod-annotations)
 - [Themes](#themes)
 - [Renovate](#renovate)
@@ -747,6 +748,21 @@ gitea:
       ENABLE_PPROF: true
 ```
 
+### Secure Metrics Endpoint
+
+Metrics endpoint `/metrics` can be secured by using `Bearer` token authentication.
+
+**Note:** Providing non-empty `TOKEN` value will also require authentication for `ServiceMonitor`.
+
+```yaml
+gitea:
+  metrics:
+    token: "secure-token"
+    enabled: true
+    serviceMonitor:
+      enabled: true
+```
+
 ## Pod annotations
 
 Annotations can be added to the Gitea pod.
@@ -1053,6 +1069,7 @@ To comply with the Gitea helm chart definition of the digest parameter, a "custo
 | `gitea.admin.email`                          | Email for the Gitea admin user                                                                                                 | `gitea@local.domain` |
 | `gitea.admin.passwordMode`                   | Mode for how to set/update the admin user password. Options are: initialOnlyNoReset, initialOnlyRequireReset, and keepUpdated  | `keepUpdated`        |
 | `gitea.metrics.enabled`                      | Enable Gitea metrics                                                                                                           | `false`              |
+| `gitea.metrics.token`                        | used for `bearer` token authentication on metrics endpoint. If not specified or empty metrics endpoint is public.              | `nil`                |
 | `gitea.metrics.serviceMonitor.enabled`       | Enable Gitea metrics service monitor. Requires, that `gitea.metrics.enabled` is also set to true, to enable metrics generally. | `false`              |
 | `gitea.metrics.serviceMonitor.interval`      | Interval at which metrics should be scraped. If not specified Prometheus' global scrape interval is used.                      | `""`                 |
 | `gitea.metrics.serviceMonitor.relabelings`   | RelabelConfigs to apply to samples before scraping.                                                                            | `[]`                 |

templates/_helpers.tpl

@@ -311,6 +311,9 @@ https
   {{- if not (hasKey .Values.gitea.config.metrics "ENABLED") -}}
     {{- $_ := set .Values.gitea.config.metrics "ENABLED" .Values.gitea.metrics.enabled -}}
   {{- end -}}
+  {{- if and (not (hasKey .Values.gitea.config.metrics "TOKEN")) (.Values.gitea.metrics.token) (.Values.gitea.metrics.enabled) -}}
+    {{- $_ := set .Values.gitea.config.metrics "TOKEN" .Values.gitea.metrics.token -}}
+  {{- end -}}
   {{- /* redis queue */ -}}
   {{- if or ((index .Values "redis-cluster").enabled) ((index .Values "redis").enabled) -}}
     {{- $_ := set .Values.gitea.config.queue "TYPE" "redis" -}}
@@ -465,3 +468,7 @@ https
   {{- end -}}
   {{- toYaml $probe -}}
 {{- end -}}
+
+{{- define "gitea.metrics-secret-name" -}}
+{{ default (printf "%s-metrics-secret" (include "gitea.fullname" .)) }}
+{{- end -}}

templates/gitea/metrics-secret.yaml

@@ -0,0 +1,12 @@
+{{- if and (.Values.gitea.metrics.enabled) (.Values.gitea.metrics.serviceMonitor.enabled) (.Values.gitea.metrics.token) -}}
+apiVersion: v1
+kind: Secret
+metadata:
+  name: {{ include "gitea.metrics-secret-name" . }}
+  namespace: {{ .Values.namespace | default .Release.Namespace }}
+  labels:
+    {{- include "gitea.labels" . | nindent 4 }}
+type: Opaque
+data:
+  token: {{ .Values.gitea.metrics.token  | b64enc }}
+{{- end }}

templates/gitea/servicemonitor.yaml

@@ -32,4 +32,12 @@ spec:
     tlsConfig:
       {{- . | toYaml | nindent 6 }}
     {{- end }}
+    {{- if .Values.gitea.metrics.token }}
+    authorization:
+      type: Bearer
+      credentials:
+        name: {{ include "gitea.metrics-secret-name" . }}
+        key: token
+        optional: false
+    {{- end }}
 {{- end -}}

unittests/config/metrics-section_metrics-token.yaml

@@ -0,0 +1,58 @@
+suite: config template | metrics section (metrics token)
+release:
+  name: gitea-unittests
+  namespace: testing
+tests:
+  - it: metrics token is set
+    template: templates/gitea/config.yaml
+    set:
+      gitea:
+        metrics:
+          enabled: true
+          token: "somepassword"
+    asserts:
+      - documentIndex: 0
+        equal:
+          path: stringData.metrics
+          value: |-
+            ENABLED=true
+            TOKEN=somepassword
+  - it: metrics token is empty
+    template: templates/gitea/config.yaml
+    set:
+      gitea:
+        metrics:
+          enabled: true
+          token: ""
+    asserts:
+      - documentIndex: 0
+        equal:
+          path: stringData.metrics
+          value: |-
+            ENABLED=true
+  - it: metrics token is nil
+    template: templates/gitea/config.yaml
+    set:
+      gitea:
+        metrics:
+          enabled: true
+          token:
+    asserts:
+      - documentIndex: 0
+        equal:
+          path: stringData.metrics
+          value: |-
+            ENABLED=true
+  - it: does not configures a token if metrics are disabled
+    template: templates/gitea/config.yaml
+    set:
+      gitea:
+        metrics:
+          enabled: false
+          token: "somepassword"
+    asserts:
+      - documentIndex: 0
+        equal:
+          path: stringData.metrics
+          value: |-
+            ENABLED=false

unittests/metric-secret/metrics-secret-servicemonitor-disabled.yaml

@@ -0,0 +1,23 @@
+suite: Metrics secret template (monitoring disabled)
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/metrics-secret.yaml
+tests:
+  - it: renders nothing if monitoring disabled and gitea.metrics.token empty
+    set:
+      gitea.metrics.enabled: false
+      gitea.metrics.serviceMonitor.enabled: false
+      gitea.metrics.token: ""
+    asserts:
+      - hasDocuments:
+          count: 0
+  - it: renders nothing if monitoring disabled and gitea.metrics.token not empty
+    set:
+      gitea.metrics.enabled: false
+      gitea.metrics.serviceMonitor.enabled: false
+      gitea.metrics.token: "test-token"
+    asserts:
+      - hasDocuments:
+          count: 0

unittests/metric-secret/metrics-secret-servicemonitor-enabled.yaml

@@ -0,0 +1,33 @@
+suite: Metrics secret template (monitoring enabled)
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/metrics-secret.yaml
+tests:
+  - it: renders nothing if monitoring enabled and gitea.metrics.token empty
+    set:
+      gitea.metrics.enabled: true
+      gitea.metrics.serviceMonitor.enabled: true
+      gitea.metrics.token: ""
+    asserts:
+      - hasDocuments:
+          count: 0
+  - it: renders Secret if monitoring enabled and gitea.metrics.token not empty
+    set:
+      gitea.metrics.enabled: true
+      gitea.metrics.serviceMonitor.enabled: true
+      gitea.metrics.token: "test-token"
+    asserts:
+      - hasDocuments:
+          count: 1
+      - documentIndex: 0
+        containsDocument:
+          kind: Secret
+          apiVersion: v1
+          name: gitea-unittests-metrics-secret
+      - isNotNullOrEmpty:
+          path: metadata.labels
+      - equal:
+          path: data.token
+          value: "dGVzdC10b2tlbg=="

unittests/servicemonitor/servicemonitor-disabled.yaml

@@ -0,0 +1,23 @@
+suite: ServiceMonitor template (monitoring disabled)
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/servicemonitor.yaml
+tests:
+  - it: renders nothing if gitea.metrics.serviceMonitor disabled and gitea.metrics.token empty
+    set:
+      gitea.metrics.enabled: false
+      gitea.metrics.token: ""
+      gitea.metrics.serviceMonitor.enabled: false
+    asserts:
+      - hasDocuments:
+          count: 0
+  - it: renders nothing if gitea.metrics.serviceMonitor disabled and gitea.metrics.token not empty
+    set:
+      gitea.metrics.enabled: false
+      gitea.metrics.token: "test-token"
+      gitea.metrics.serviceMonitor.enabled: false
+    asserts:
+      - hasDocuments:
+          count: 0

unittests/servicemonitor/servicemonitor-enabled.yaml

@@ -0,0 +1,70 @@
+suite: ServiceMonitor template (monitoring enabled)
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/servicemonitor.yaml
+tests:
+  - it: renders unsecure ServiceMonitor if gitea.metrics.token nil
+    set:
+      gitea.metrics.enabled: true
+      gitea.metrics.token:
+      gitea.metrics.serviceMonitor.enabled: true
+    asserts:
+      - hasDocuments:
+          count: 1
+      - documentIndex: 0
+        containsDocument:
+          kind: ServiceMonitor
+          apiVersion: monitoring.coreos.com/v1
+          name: gitea-unittests
+      - isNotNullOrEmpty:
+          path: metadata.labels
+      - equal:
+          path: spec.endpoints
+          value:
+            - port: http
+  - it: renders unsecure ServiceMonitor if gitea.metrics.token empty
+    set:
+      gitea.metrics.enabled: true
+      gitea.metrics.token: ""
+      gitea.metrics.serviceMonitor.enabled: true
+    asserts:
+      - hasDocuments:
+          count: 1
+      - documentIndex: 0
+        containsDocument:
+          kind: ServiceMonitor
+          apiVersion: monitoring.coreos.com/v1
+          name: gitea-unittests
+      - isNotNullOrEmpty:
+          path: metadata.labels
+      - equal:
+          path: spec.endpoints
+          value:
+            - port: http
+  - it: renders secure ServiceMonitor if gitea.metrics.token not empty
+    set:
+      gitea.metrics.enabled: true
+      gitea.metrics.token: "test-token"
+      gitea.metrics.serviceMonitor.enabled: true
+    asserts:
+      - hasDocuments:
+          count: 1
+      - documentIndex: 0
+        containsDocument:
+          kind: ServiceMonitor
+          apiVersion: monitoring.coreos.com/v1
+          name: gitea-unittests
+      - isNotNullOrEmpty:
+          path: metadata.labels
+      - equal:
+          path: spec.endpoints
+          value:
+            - port: http
+              authorization:
+                type: Bearer
+                credentials:
+                  name: gitea-unittests-metrics-secret
+                  key: token
+                  optional: false

values.yaml

@@ -461,6 +461,7 @@ gitea:
     passwordMode: keepUpdated
 
   ## @param gitea.metrics.enabled Enable Gitea metrics
+  ## @param gitea.metrics.token used for `bearer` token authentication on metrics endpoint. If not specified or empty metrics endpoint is public.
   ## @param gitea.metrics.serviceMonitor.enabled Enable Gitea metrics service monitor. Requires, that `gitea.metrics.enabled` is also set to true, to enable metrics generally.
   ## @param gitea.metrics.serviceMonitor.interval Interval at which metrics should be scraped. If not specified Prometheus' global scrape interval is used.
   ## @param gitea.metrics.serviceMonitor.relabelings RelabelConfigs to apply to samples before scraping.
@@ -469,6 +470,7 @@ gitea:
   ## @param gitea.metrics.serviceMonitor.tlsConfig TLS configuration to use when scraping the metric endpoint by Prometheus.
   metrics:
     enabled: false
+    token:
     serviceMonitor:
       enabled: false
       #  additionalLabels: