policyDefinitions/Kubernetes/forbidden-sysctl-interfaces/template.yaml

apiVersion: templates.gatekeeper.sh/v1beta1
kind: ConstraintTemplate
metadata:
  name: k8sazureforbiddensysctls
spec:
  crd:
    spec:
      names:
        kind: K8sAzureForbiddenSysctls
      validation:
        # Schema for the `parameters` field
        openAPIV3Schema:
          properties:
            forbiddenSysctls:
              type: array
              items:
                type: string
  targets:
    - target: admission.k8s.gatekeeper.sh
      rego: |
        package k8sazureforbiddensysctls

        violation[{"msg": msg, "details": {}}] {
            sysctl := input.review.object.spec.securityContext.sysctls[_].name
            forbidden_sysctl(sysctl)
            msg := sprintf("The sysctl %v is not allowed, pod: %v. Forbidden sysctls: %v", [sysctl, input.review.object.metadata.name, input.parameters.forbiddenSysctls])
        }

        # * may be used to forbid all sysctls
        forbidden_sysctl(sysctl) {
            input.parameters.forbiddenSysctls[_] == "*"
        }

        forbidden_sysctl(sysctl) {
            input.parameters.forbiddenSysctls[_] == sysctl
        }

        forbidden_sysctl(sysctl) {
            startswith(sysctl, trim(input.parameters.forbiddenSysctls[_], "*"))
        }