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:
  ingressClassName: nginx
  rules:
  - host: external-auth-01.sample.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: http-svc
            port:
              number: 80