Restrict External IPs

 1apiVersion: kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: restrict-external-ips
 5  annotations:
 6    policies.kyverno.io/title: Restrict External IPs
 7    policies.kyverno.io/category: Best Practices
 8    policies.kyverno.io/minversion: 1.6.0
 9    policies.kyverno.io/severity: medium
10    policies.kyverno.io/subject: Service
11    policies.kyverno.io/description: >-
12      Service externalIPs can be used for a MITM attack (CVE-2020-8554).
13      Restrict externalIPs or limit to a known set of addresses.
14      See: https://github.com/kyverno/kyverno/issues/1367. This policy validates
15      that the `externalIPs` field is not set on a Service.      
16spec:
17  validationFailureAction: audit
18  background: true
19  rules:
20  - name: check-ips
21    match:
22      any:
23      - resources:
24          kinds:
25          - Service
26    validate:
27      message: "externalIPs are not allowed."
28      pattern:
29        spec:
30          # restrict external IP addresses
31          # you can alternatively restrict to a known set of addresses using:
32          #     =(externalIPs): ["37.10.11.53", "153.10.20.1"]
33          X(externalIPs): "null"