Implement custom CORS in Nginx Ingress Controller

[dhatri308]

We deploy our kubernetes application in AWS and Azure. We have an Nginx Ingress Controller in front of all our services. We need to implement some cross-origin calls allow/disallow logic. Which is the best place to implement this? For example we do want to allow all calls from *.foobar.com.
Thanks

[jjngx]

Hi @dhatri308 , do you use Ingress or VirtualServer?

[dhatri308]

We use Ingress.

Would below change work ?

annotations:
    nginx.org/location-snippets: |
      if ($http_origin ~* "^https?://([a-z0-9-]+\.)*foobar\.com$") {
          add_header "Access-Control-Allow-Origin" "$http_origin" always;
          add_header "Access-Control-Allow-Credentials" "true" always;
          add_header "Access-Control-Allow-Methods" "GET, POST, OPTIONS, PUT, DELETE" always;
          add_header "Access-Control-Allow-Headers" "DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range" always;
      }

    nginx.org/server-snippet: |
      if ($request_method = OPTIONS ) {
          add_header "Access-Control-Allow-Origin" "$http_origin" always;
          add_header "Access-Control-Allow-Credentials" "true" always;
          add_header "Access-Control-Allow-Methods" "GET, POST, OPTIONS, PUT, DELETE" always;
          add_header "Access-Control-Allow-Headers" "DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range" always;
          add_header "Access-Control-Max-Age" 1728000;
          add_header "Content-Type" "text/plain charset=UTF-8";
          add_header "Content-Length" 0;
          return 204;
      }

[dhatri308]

We have a main nginx and then bunch of Ingresses.
I tried adding both the if blocks in main nginx configmap location-snippets.
While some of the Ingress resources did get this config but some did not.
Then I noticed that the Ingresses that did not get this change from main nginx configmap had their own location-snippets and that had a higher precedence than the main nginx's configmap's location-snippets.
I was hoping that the location-snippets from both layers would get merged but looks like that is not the case. Is this behavior expected ?
Thanks