Add policy Restrict Cluster Role CSR (#1077)

* Added policy for restricting clusterroles for CSR's, along with unit tests, chainsaw tests and artifacthub-pkg.yaml

Signed-off-by: nsagark <sagar@nirmata.com>

* updated the policy with annotations and validation failure action

Signed-off-by: nsagark <sagar@nirmata.com>

* updated the sha256sum on the artifacthub-pkg.yaml

Signed-off-by: nsagark <sagar@nirmata.com>

* Update other/restrict-clusterrole-csr/artifacthub-pkg.yaml

Signed-off-by: Chip Zoller <chipzoller@gmail.com>

* Update other/restrict-clusterrole-csr/artifacthub-pkg.yaml

Signed-off-by: Chip Zoller <chipzoller@gmail.com>

* Update other/restrict-clusterrole-csr/artifacthub-pkg.yaml

Signed-off-by: Chip Zoller <chipzoller@gmail.com>

---------

Signed-off-by: nsagark <sagar@nirmata.com>
Signed-off-by: Chip Zoller <chipzoller@gmail.com>
Co-authored-by: Chip Zoller <chipzoller@gmail.com>

other/restrict-clusterrole-csr/.chainsaw-test/chainsaw-step-01-assert-1.yaml

@@ -0,0 +1,6 @@
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: restrict-clusterrole-csr 
+status:
+  ready: true

other/restrict-clusterrole-csr/.chainsaw-test/chainsaw-test.yaml

@@ -0,0 +1,29 @@
+apiVersion: chainsaw.kyverno.io/v1alpha1
+kind: Test
+metadata:
+  name: restrict-clusterrole-csr 
+spec:
+  steps:
+  - name: step-01
+    try:
+    - apply:
+        file: ../restrict-clusterrole-csr.yaml
+    - patch:
+        resource:
+          apiVersion: kyverno.io/v1
+          kind: ClusterPolicy
+          metadata:
+            name: restrict-clusterrole-csr
+          spec:
+            validationFailureAction: Enforce
+    - assert:
+        file: chainsaw-step-01-assert-1.yaml
+  - name: step-02
+    try:
+    - apply:
+        file: non-violating-clusterrole.yaml
+    - apply:
+        expect:
+        - check:
+            ($error != null): true
+        file: violating-clusterrole.yaml

other/restrict-clusterrole-csr/.chainsaw-test/non-violating-clusterrole.yaml

@@ -0,0 +1,11 @@
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: non-violating-clusterrole
+rules:
+- apiGroups: [""]
+  resources: ["certificatesigningrequests/approval"]
+  verbs: ["get", "list"]
+- apiGroups: [""]
+  resources: ["signers"]
+  verbs: ["get", "list"]

other/restrict-clusterrole-csr/.chainsaw-test/violating-clusterrole.yaml

@@ -0,0 +1,11 @@
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: violating-clusterrole
+rules:
+- apiGroups: [""]
+  resources: ["certificatesigningrequests/approval"]
+  verbs: ["update", "approve"]
+- apiGroups: [""]
+  resources: ["signers"]
+  verbs: ["approve"]

other/restrict-clusterrole-csr/.kyverno-test/kyverno-test.yaml

@@ -0,0 +1,33 @@
+apiVersion: cli.kyverno.io/v1alpha1
+kind: Test
+metadata:
+  name: restrict-clusterrole-csr
+policies:
+- ../restrict-clusterrole-csr.yaml
+resources:
+- resource.yaml
+results:
+- kind: ClusterRole
+  policy: restrict-clusterrole-csr
+  resources:
+  - violating-clusterrole 
+  result: fail
+  rule: certificatesigningrequests-update-prevention
+- kind: ClusterRole
+  policy: restrict-clusterrole-csr
+  resources:
+  - violating-clusterrole
+  result: fail
+  rule: signers-approve-prevention
+- kind: ClusterRole
+  policy: restrict-clusterrole-csr
+  resources:
+  - non-violating-clusterrole
+  result: pass
+  rule: certificatesigningrequests-update-prevention
+- kind: ClusterRole
+  policy: restrict-clusterrole-csr
+  resources:
+  - non-violating-clusterrole
+  result: pass
+  rule: signers-approve-prevention

other/restrict-clusterrole-csr/.kyverno-test/resource.yaml

@@ -0,0 +1,24 @@
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: violating-clusterrole
+rules:
+- apiGroups: [""]
+  resources: ["certificatesigningrequests/approval"]
+  verbs: ["update", "approve"]
+- apiGroups: [""]
+  resources: ["signers"]
+  verbs: ["approve"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: non-violating-clusterrole
+rules:
+- apiGroups: [""]
+  resources: ["certificatesigningrequests/approval"]
+  verbs: ["get", "list"]
+- apiGroups: [""]
+  resources: ["signers"]
+  verbs: ["get", "list"]
+

other/restrict-clusterrole-csr/artifacthub-pkg.yaml

@@ -0,0 +1,21 @@
+name: restrict-clusterrole-csr 
+version: 1.0.0
+displayName: Restrict Clusterrole for Certificate Signing Requests (CSR's)
+createdAt: "2024-07-17T20:30:05.000Z"
+description: >-
+  ClusterRoles that grant permissions to approve CertificateSigningRequests should be minimized to reduce powerful identities in the cluster. Approving CertificateSigningRequests allows one to issue new credentials for any user or group. As such, ClusterRoles that grant permissions to approve CertificateSigningRequests are granting cluster admin privileges. Minimize such ClusterRoles to limit the number of powerful credentials that if compromised could take over the entire cluster. For more information, refer to https://docs.prismacloud.io/en/enterprise-edition/policy-reference/kubernetes-policies/kubernetes-policy-index/ensure-clusterroles-that-grant-permissions-to-approve-certificatesigningrequests-are-minimized. 
+install: |-
+  ```shell
+  kubectl apply -f https://raw.githubusercontent.com/kyverno/policies/main/other/restrict-clusterrole-csr/restrict-clusterrole-csr.yaml
+  ```
+keywords:
+- kyverno
+- Other
+readme: |
+  ClusterRoles that grant permissions to approve CertificateSigningRequests should be minimized to reduce powerful identities in the cluster. Approving CertificateSigningRequests allows one to issue new credentials for any user or group. As such, ClusterRoles that grant permissions to approve CertificateSigningRequests are granting cluster admin privileges. Minimize such ClusterRoles to limit the number of powerful credentials that if compromised could take over the entire cluster. For more information, refer to https://docs.prismacloud.io/en/enterprise-edition/policy-reference/kubernetes-policies/kubernetes-policy-index/ensure-clusterroles-that-grant-permissions-to-approve-certificatesigningrequests-are-minimized. 
+
+  Refer to the documentation for more details on Kyverno annotations: https://artifacthub.io/docs/topics/annotations/kyverno/
+annotations:
+  kyverno/category: "Other"
+  kyverno/subject: "ClusterRole"
+digest: c36b162b694005bbdf84f61f70c86b7ddbaf2dd9d428023c132570df7fd18854

other/restrict-clusterrole-csr/restrict-clusterrole-csr.yaml

@@ -0,0 +1,55 @@
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: restrict-clusterrole-csr
+  annotations:
+    policies.kyverno.io/title: Restrict Cluster Role CSR
+    policies.kyverno.io/category: Other
+    policies.kyverno.io/severity: medium
+    policies.kyverno.io/subject: ClusterRole
+    kyverno.io/kyverno-version: 1.11.5
+    kyverno.io/kubernetes-version: "1.27"
+    policies.kyverno.io/description: >-
+      ClusterRoles that grant permissions to approve CertificateSigningRequests should be minimized to reduce powerful identities in the cluster. Approving CertificateSigningRequests allows one to issue new credentials for any user or group. As such, ClusterRoles that grant permissions to approve CertificateSigningRequests are granting cluster admin privileges. Minimize such ClusterRoles to limit the number of powerful credentials that if compromised could take over the entire cluster. For more information, refer to https://docs.prismacloud.io/en/enterprise-edition/policy-reference/kubernetes-policies/kubernetes-policy-index/ensure-clusterroles-that-grant-permissions-to-approve-certificatesigningrequests-are-minimized.
+spec:
+  validationFailureAction: Audit
+  background: true
+  rules:
+  - name: certificatesigningrequests-update-prevention
+    match:
+      any:
+      - resources:
+          kinds:
+          - ClusterRole
+    validate:
+      message: "Use of verbs `update` and `patch` are forbidden for certificatesigningrequests/approval."
+      foreach:
+      - list: "request.object.rules[?resources.contains(@,'certificatesigningrequests/approval')]"
+        deny:
+          conditions:
+            any:
+            - key: ["update", "patch"]
+              operator: AnyIn
+              value: "{{ element.verbs[] }}"
+            - key: "{{ contains(element.verbs[], '*') }}"
+              operator: Equals
+              value: true
+  - name: signers-approve-prevention
+    match:
+      any:
+      - resources:
+          kinds:
+          - ClusterRole
+    validate:
+      message: "Use of verbs `approve` are forbidden for signers."
+      foreach:
+      - list: "request.object.rules[?resources.contains(@,'signers')]"
+        deny:
+          conditions:
+            any:
+            - key: ["approve"]
+              operator: AnyIn
+              value: "{{ element.verbs[] }}"
+            - key: "{{ contains(element.verbs[], '*') }}"
+              operator: Equals
+              value: true