kubeval should FAIL on underscore in resource names

[mjbright]

The following yaml should FAIL due to the underscore in 'pv_demo', but it PASSes:

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: pv_demo
  name: pv_demo
spec:
  containers:
  - image: mjbright/ckad-demo:alpine1
    name: pv_demo
  dnsPolicy: ClusterFirst
  restartPolicy: Always

Kubeval produces

$ kubeval pod.yaml
PASS - pod.yaml contains a valid Pod (pv_demo)

Trying to create the Pod produces

$ kubectl create -f pod.yaml

The Pod "pv_demo" is invalid:
* metadata.name: Invalid value: "pv_demo": a DNS-1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')
* spec.containers[0].name: Invalid value: "pv_demo": a DNS-1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')

[yannh]

Hi @mjbright , this issue, as well as others such as #256 or #253 , are related to the way kubeval does validation. Kubeval uses JSON Schemas derived from the Swagger documentation of the Kubernetes API - this file https://github.com/kubernetes/kubernetes/blob/master/api/openapi-spec/swagger.json .

While this file might tell you that this or that field is required, optional, or must be a string, an array or an integer, what that file does not contain is advanced validation logic that the Kubernetes server does.

This might help - https://prefetch.net/blog/2020/06/29/using-kubernetes-server-side-validation-to-validate-your-deployment-manifests/ but it doesn't seem extremely practical.

[carlossg]

dupe of #214