Why Ingress NGINX removes my response headers

Use following annotations in your ingress to set response header

    nginx.ingress.kubernetes.io/configuration-snippet: |
      more_set_headers "X-Frame-Options: Deny";
      more_set_headers "X-Xss-Protection: 1; mode=block";
      more_set_headers "X-Content-Type-Options: nosniff";

The you are not able to find those headers as the traffic is flowing from a nginx ingress controller which acts as a proxy. To add some custom headers you can use the following given steps.

1. create a file and name it as custom-headers.yml and add the following data.

   apiVersion: v1
   data:
     X-Frame-Options: "Deny"
     X-Xss-Protection: "1; mode=block"
     X-Content-Type-Options: "nosniff"
     kind: ConfigMap
   metadata:
   name: custom-headers
   namespace: ingress-nginx
   

This file will create a ConfigMap in the ingress-nginx namespace. Apply this ConfigMap: kubectl apply -f custom-headers.yml

Now we need to make our nginx ingress controller to use this new ConfigMap. For that we need to add our config map with the global configs that were being used until now. For that create a file configmap.yml and add the following data. apiVersion: v1 data: proxy-set-headers: "ingress-nginx/custom-headers" kind: ConfigMap metadata: name: nginx-configuration namespace: ingress-nginx labels: app.kubernetes.io/name: ingress-nginx app.kubernetes.io/part-of: ingress-nginx

Apply this configuration by : kubectl apply -f configmap.yml

Check your configurations by using : kubectl exec <nginx-controller pod name> -n ingress-nginx cat /etc/nginx/nginx.conf

I have not tried this myself but I think you need to enable this setting.

https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/#allow-backend-server-header

data:
    allow-backend-server: "true"

You may try to enable this settings via annotations.