Runs an Image Not Pinned to a Digest

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: initcontainer-image-digest
  annotations:
    kubeapt.io/uuid: "b6f03623-4d26-40db-a300-f5d2c08cdd6e"
    security.kubeapt.io/displayName: "Runs an Image Not Pinned to a Digest"
    security.kubeapt.io/description: "An image reference without a digest resolves through a mutable tag, so registry content can be replaced between pulls and the init container silently starts running attacker-supplied code on the next restart or reschedule."
    security.kubeapt.io/resource: "InitContainers"
    security.kubeapt.io/severity: "Moderate"
    security.kubeapt.io/remediation: "Replace the mutable tag with an immutable digest reference of the form registry/image@sha256:<64-hex-digest>. Field: spec.initContainers[*].image."
    security.kubeapt.io/product: "Kubernetes"
spec:
  failurePolicy: Fail
  matchConstraints:
    resourceRules:
    - apiGroups:
      - ''
      apiVersions:
      - v1
      operations:
      - CREATE
      - UPDATE
      resources:
      - pods
  variables:
  - name: isWindows
    expression: |
      has(object.spec.os) && has(object.spec.os.name) && object.spec.os.name.lowerAscii() == "windows"
  validations:
  - expression: |
      variables.isWindows || !has(object.spec.initContainers) || object.spec.initContainers.all(ic,
        ic.image.matches(".*@sha256:[0-9A-Fa-f]{64}")
      )
    message: |
      spec.initContainers[*].image must be pinned by an immutable @sha256 digest.