I have recently deployed my .NET Core 3.1 based API into an AKS cluster and used an NGINX ingress to access it. I added an A record to my domain DNS to point to the public IP address provided by the NGINX controller. I also set up TLS in the ingress manifest then set up a DevOps pipeline to use Helm to deploy my API to AKS. When I browse my domain, Swagger loads but when I try calling the API, Swagger displays an undocumented code where the details field contains TypeError: Failed to fetch. The API is simply supposed to return an OK.

I thought it was a CORS-related issue so I enabled CORS both on the API level and on the ingress level.

Here is my ingress manifest:

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
{{ $fullname := include "testchart.fullname" .}}
{{ $serviceport := .Values.service.port }}
{{ $ns := .Values.namespace }}
{{ with .Values.ingress }}
metadata:
  name: {{ $fullname }}-ing
  namespace: {{ $ns }}
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/enable-cors: "true"
    nginx.ingress.kubernetes.io/cors-allow-origin: "https://api.mydomain.io"
    nginx.ingress.kubernetes.io/cors-allow-credentials: "true"
    nginx.ingress.kubernetes.io/cors-allow-methods: PUT, GET, POST, OPTIONS, DELETE, PATCH    
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  tls:
  - hosts:
    - {{ .host }}
    secretName: {{ .tls.secretname }}
  rules:
  - host: {{ .host }}
    http:
      paths:
      - backend:
          serviceName: {{ $fullname }}-svc
          servicePort: {{ $serviceport }}
{{ end }}

When I try to hit the API in Postman, I get a warning saying Unable to verify the first certificate. The certificate I am using doesn't seem to have an issue as I can load the address in all browsers without getting an invalid or non-secure certificate warning.

Something I noticed is when I changed the type of the Kubernetes service from ClusterIP to LoadBalancer and browsed the public IP of the service, I managed to get an OK after calling the same API on Swagger.

Any idea what could be wrong?

Edit: I just removed the tls section from the ingress manifest and deployed the API. It worked. So it seems to have something to do with HTTPS.