helm: add least privileges logic for secrets on ceph-csi-cephfs chart

this allows the encryption KMS config to be granted secret access with
a least privilges policy.

Signed-off-by: Antoine C <hi@acolombier.dev>

charts/ceph-csi-cephfs/README.md

@@ -83,6 +83,16 @@ storageClass:
     encryptionKMSID: kubernetes
 ```
 
+#### Least privilege secret access
+
+If you use the `metadata` and let RBAC created by the chart, permissions
+will be given to access **only** the secret referenced in the
+`encryptionKMSConfig`. This is something important to keep in mind, as a
+manual change to the config to point to another secret or add further KMS
+config will not be authorized. If you wish to give CephCSI a global secret
+access to the cluster, you may set `rbac.leastPrivileges` to `false`, and
+permissions will be granted globally via a *ClusterRole*.
+
 #### Known Issues Upgrading
 
 - When upgrading to version >=3.7.0, you might encounter an error that the
@@ -127,6 +137,7 @@ charts and their default values.
 | Parameter                                      | Description                                                                                                                                          | Default                                            |
 | ---------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------- |
 | `rbac.create`                                  | Specifies whether RBAC resources should be created                                                                                                   | `true`                                             |
+| `rbac.leastPrivileges`                         | Specifies whether RBAC resources should be created with a restricted scope when supported (only secrets supported currently)                         | `true`                                             |
 | `serviceAccounts.nodeplugin.create`            | Specifies whether a nodeplugin ServiceAccount should be created                                                                                      | `true`                                             |
 | `serviceAccounts.nodeplugin.name`              | The name of the nodeplugin ServiceAccount to use. If not set and create is true, a name is generated using the fullname                              | ""                                                 |
 | `serviceAccounts.provisioner.create`           | Specifies whether a provisioner ServiceAccount should be created                                                                                     | `true`                                             |

charts/ceph-csi-cephfs/templates/nodeplugin-clusterrole.yaml

@@ -3,7 +3,6 @@ kind: ClusterRole
 apiVersion: rbac.authorization.k8s.io/v1
 metadata:
   name: {{ include "ceph-csi-cephfs.nodeplugin.fullname" . }}
-  namespace: {{ .Release.Namespace }}
   labels:
     app: {{ include "ceph-csi-cephfs.name" . }}
     chart: {{ include "ceph-csi-cephfs.chart" . }}
@@ -19,7 +18,7 @@ rules:
   - apiGroups: [""]
     resources: ["configmaps"]
     verbs: ["get"]
-{{- if and .Values.encryptionKMSConfig .Values.encryptionKMSConfig.secretNamespace (not (eq .Values.encryptionKMSConfig.secretNamespace .Release.Namespace)) }}
+{{- if and .Values.encryptionKMSConfig .Values.encryptionKMSConfig.secretNamespace (not .Values.rbac.leastPrivileges) }}
   # allow to read the encryption key used with the metadata KMS
   - apiGroups: [""]
     resources: ["secrets"]

charts/ceph-csi-cephfs/templates/nodeplugin-role.yaml

@@ -1,9 +1,10 @@
-{{- if .Values.rbac.create -}}
-{{- if and .Values.encryptionKMSConfig .Values.encryptionKMSConfig.secretNamespace  .Values.encryptionKMSConfig.secretName (eq .Values.encryptionKMSConfig.secretNamespace .Release.Namespace) -}}
+{{- if and .Values.rbac.create .Values.rbac.leastPrivileges -}}
+{{- if and .Values.encryptionKMSConfig (eq .Values.encryptionKMSConfig.encryptionKMSType "metadata") .Values.encryptionKMSConfig.secretNamespace .Values.encryptionKMSConfig.secretName -}}
 kind: Role
 apiVersion: rbac.authorization.k8s.io/v1
 metadata:
   name: {{ include "ceph-csi-cephfs.nodeplugin.fullname" . }}
+  namespace: {{ .Values.encryptionKMSConfig.secretNamespace }}
   labels:
     app: {{ include "ceph-csi-cephfs.name" . }}
     chart: {{ include "ceph-csi-cephfs.chart" . }}

charts/ceph-csi-cephfs/templates/nodeplugin-rolebinding.yaml

@@ -1,10 +1,10 @@
-{{- if .Values.rbac.create -}}
-{{- if and (eq .Values.encryptionKMSConfig.encryptionKMSType "metadata") (eq .Values.encryptionKMSConfig.secretNamespace .Release.Namespace) -}}
+{{- if and .Values.rbac.create .Values.rbac.leastPrivileges -}}
+{{- if and .Values.encryptionKMSConfig (eq .Values.encryptionKMSConfig.encryptionKMSType "metadata") .Values.encryptionKMSConfig.secretNamespace -}}
 kind: RoleBinding
 apiVersion: rbac.authorization.k8s.io/v1
 metadata:
   name: {{ include "ceph-csi-cephfs.nodeplugin.fullname" . }}
-  namespace: {{ .Release.Namespace }}
+  namespace: {{ .Values.encryptionKMSConfig.secretNamespace }}
   labels:
     app: {{ include "ceph-csi-cephfs.name" . }}
     chart: {{ include "ceph-csi-cephfs.chart" . }}

charts/ceph-csi-cephfs/values.yaml

@@ -2,6 +2,9 @@
 rbac:
   # Specifies whether RBAC resources should be created
   create: true
+  # When possible try and reduce the scope of permission to only give
+  # access to resources defined in the config. See the README for more info
+  leastPrivileges: true
 
 serviceAccounts:
   nodeplugin: