Using Azure Waf Policy For Path on a specific ingress when policy doesn't exist breaks entire app gateway

[Poltergeisen]

Describe the bug
We have an app gateway that is shared for an entire AKS cluster. When a team accidentally references a WAF policy that doesn't exist yet, it breaks the app gateway backend connections for the entire App Gateway, and not for the ingress in question.

To Reproduce
Steps to reproduce the behavior:
Create an AKS cluster
Create 2 applications to run on the cluster, one using no WAF policy and one using a WAF policy that doesn't exist yet

Both applications fail to resolve IP addresses from the backend pool.

Example ingress:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-api
  annotations:
    kubernetes.io/ingress.class: azure/application-gateway
    cert-manager.io/cluster-issuer: sectigo-issuer
    appgw.ingress.kubernetes.io/backend-protocol: http
    appgw.ingress.kubernetes.io/use-private-ip: "true"
    appgw.ingress.kubernetes.io/waf-policy-for-path: "subscriptions/xxx-xxx-xxx/resourceGroups/my-rg/providers/Microsoft.Network/applicationGatewayWebApplicationFirewallPolicies/my-policy-that-doesnt-exist"
spec:
  tls:
  - hosts:
    - my.host.tld
    secretName: sbx-tls
  rules:
  - host:my.host.tld
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: my-service
            port: 
              number: 80

Ingress Controller details

• Output of kubectl describe pod <ingress controller> . The pod name can be obtained by running helm list.
• I'm running this via AKS, i can send more additional info as needed. We don't have any custom configuration here
• Output of `kubectl logs .
  • I am not comfortable sharing those on github, but I can share privately through the support ticket if necessary.
• Any Azure support tickets associated with this issue.
  • 2405220040017720

[erkkov2lja]

The issue is there and will break the whole AKS ingresses created, after one of the ingress rules would have non-existing WAF rule reference.

[Poltergeisen]

The issue is there and will break the whole AKS ingresses created, after one of the ingress rules would have non-existing WAF rule reference.

Yes, this is what we experienced. We are working with a CSA on this, but there doesn't seem to be any good solutions. Waiting to hear back more and can update this issue if I do