Prevent Disabling Istio Sidecar Injection in CEL expressions

 1apiVersion: kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: prevent-disabling-injection-pods
 5  annotations:
 6    policies.kyverno.io/title: Prevent Disabling Istio Sidecar Injection in CEL expressions
 7    policies.kyverno.io/category: Istio in CEL 
 8    policies.kyverno.io/severity: medium
 9    kyverno.io/kyverno-version: 1.11.0
10    policies.kyverno.io/minversion: 1.11.0
11    kyverno.io/kubernetes-version: "1.26-1.27"
12    policies.kyverno.io/subject: Pod
13    policies.kyverno.io/description: >-
14      One way sidecar injection in an Istio service mesh may be accomplished is by defining
15      an annotation at the Pod level. Pods not receiving a sidecar cannot participate in the mesh
16      thereby reducing visibility. This policy ensures that Pods cannot set the annotation
17      `sidecar.istio.io/inject` to a value of `false`.
18spec:
19  validationFailureAction: Audit
20  background: true
21  rules:
22  - name: prohibit-inject-annotation
23    match:
24      any:
25      - resources:
26          kinds:
27          - Pod
28          operations:
29          - CREATE
30          - UPDATE
31    validate:
32      cel:
33        expressions:
34          - expression: >-
35              object.metadata.?annotations[?'sidecar.istio.io/inject'].orValue('') != 'false'
36            message: "Pods may not disable sidecar injection by setting the annotation sidecar.istio.io/inject to a value of false."