Forbidden: user cannot get path "/" (not anonymous user)

Question

When accessing the k8s api endpoint (FQDN:6443), a successful retrieval will return a JSON object containing REST endpoint paths. I have a user who is granted cluster-admin privileges on the cluster who is able to successfully interact with that endpoint.

I've created a certificate for another user and granted them a subset of privileges in my cluster. The error I'm attempting to correct: They cannot access FQDN:6443, but instead get a 403 with a message that "User cannot get path /". I get the same behavior whether I specify as FQDN:6443/ or FQDN:6443 (no trailing slash). I've examined the privileges granted to cluster-admin role users, but have not recognized the gap.

Other behavior: They CAN access FQDN:6443/api, which I have not otherwise explicitly granted them, as well as the various endpoints I have explicitly granted. I believe they the api endpoint via the system:discovery role granted to the system:authenticated group. Also, if I attempt to interact with the cluster without a certificate, I correctly am identified as an anonymous user. If I interact with the cluster with a certificate whose user name does not match my rolebindings, I get the expected behaviors for all but the FQDN:6443 endpoint.

Answer 1

I had a similar similar issue. I was trying to curl the base url: https://api_server_ip:6443 with the correct certificates.

I got this error:

    {
      "kind": "Status",
      "apiVersion": "v1",
      "metadata": {

      },
      "status": "Failure",
      "message": "forbidden: User \"kubernetes\" cannot get path \"/\"",
      "reason": "Forbidden",
      "details": {

      },
      "code": 403
   }

It appears the system:discovery doesn't grant access to the base url: https://api_server_ip:6443/. The system:discovery roles only gives access to the following paths:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:discovery
rules:
- nonResourceURLs:
  - /api
  - /api/*
  - /apis
  - /apis/*
  - /healthz
  - /openapi
  - /openapi/*
  - /swagger-2.0.0.pb-v1
  - /swagger.json
  - /swaggerapi
  - /swaggerapi/*
  - /version
  - /version/
  verbs:
  - get

No access to / granted. So I created the following ClusterRole which I called discover_base_url. It grants access to the / path:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: discover_base_url
rules:
- nonResourceURLs:
  - /
  verbs:
  - get

Then I created a ClusterRoleBinding binding the forbidden user "kubernetes", (it could be any user) to the above cluster role. The following is the yaml for the ClusterRoleBinding (replace "kubernetes" with your user):

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: discover-base-url
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: discover_base_url
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: User
  name: kubernetes

After creating these two resources, the curl request works:

curl --cacert ca.pem --cert kubernetes.pem --key kubernetes-key.pem https://api_server_ip:6443
{
  "paths": [
    "/api",
    "/api/v1",
    "/apis",
    "/apis/",
    "/apis/admissionregistration.k8s.io",
    "/apis/admissionregistration.k8s.io/v1beta1",
    "/apis/apiextensions.k8s.io",
    "/apis/apiextensions.k8s.io/v1beta1",
    "/apis/apiregistration.k8s.io",
    "/apis/apiregistration.k8s.io/v1",
    "/apis/apiregistration.k8s.io/v1beta1",
    "/apis/apps",
    "/apis/apps/v1",
    "/apis/apps/v1beta1",
    "/apis/apps/v1beta2",
    "/apis/authentication.k8s.io",
    "/apis/authentication.k8s.io/v1",
    "/apis/authentication.k8s.io/v1beta1",
    "/apis/authorization.k8s.io",
    "/apis/authorization.k8s.io/v1",
    "/apis/authorization.k8s.io/v1beta1",
    "/apis/autoscaling",
    "/apis/autoscaling/v1",
    "/apis/autoscaling/v2beta1",
    "/apis/autoscaling/v2beta2",
    "/apis/batch",
    "/apis/batch/v1",
    "/apis/batch/v1beta1",
    "/apis/certificates.k8s.io",
    "/apis/certificates.k8s.io/v1beta1",
    "/apis/coordination.k8s.io",
    "/apis/coordination.k8s.io/v1beta1",
    "/apis/events.k8s.io",
    "/apis/events.k8s.io/v1beta1",
    "/apis/extensions",
    "/apis/extensions/v1beta1",
    "/apis/networking.k8s.io",
    "/apis/networking.k8s.io/v1",
    "/apis/policy",
    "/apis/policy/v1beta1",
    "/apis/rbac.authorization.k8s.io",
    "/apis/rbac.authorization.k8s.io/v1",
    "/apis/rbac.authorization.k8s.io/v1beta1",
    "/apis/scheduling.k8s.io",
    "/apis/scheduling.k8s.io/v1beta1",
    "/apis/storage.k8s.io",
    "/apis/storage.k8s.io/v1",
    "/apis/storage.k8s.io/v1beta1",
    "/healthz",
    "/healthz/autoregister-completion",
    "/healthz/etcd",
    "/healthz/log",
    "/healthz/ping",
    "/healthz/poststarthook/apiservice-openapi-controller",
    "/healthz/poststarthook/apiservice-registration-controller",
    "/healthz/poststarthook/apiservice-status-available-controller",
    "/healthz/poststarthook/bootstrap-controller",
    "/healthz/poststarthook/ca-registration",
    "/healthz/poststarthook/generic-apiserver-start-informers",
    "/healthz/poststarthook/kube-apiserver-autoregistration",
    "/healthz/poststarthook/rbac/bootstrap-roles",
    "/healthz/poststarthook/scheduling/bootstrap-system-priority-classes",
    "/healthz/poststarthook/start-apiextensions-controllers",
    "/healthz/poststarthook/start-apiextensions-informers",
    "/healthz/poststarthook/start-kube-aggregator-informers",
    "/healthz/poststarthook/start-kube-apiserver-admission-initializer",
    "/healthz/poststarthook/start-kube-apiserver-informers",
    "/logs",
    "/metrics",
    "/openapi/v2",
    "/swagger-2.0.0.json",
    "/swagger-2.0.0.pb-v1",
    "/swagger-2.0.0.pb-v1.gz",
    "/swagger-ui/",
    "/swagger.json",
    "/swaggerapi",
    "/version"
  ]
}