ingress-nginx-helm/docs/examples/auth/external-auth/ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/auth-url: "https://httpbin.org/basic-auth/user/passwd"
  name: external-auth
spec:
  rules:
  - host: external-auth-01.sample.com
    http:
      paths:
      - backend:
          serviceName: http-svc
          servicePort: 80
        path: /