Access Kubernetes API without kubectl

Question

I am trying to access the Kubernetes API directly without running kubectl -proxy. But when I use the token of the serviceaccount default, I get a 403. Even after creating a ClusterRole and ClusterRoleBinding for this serviceaccount, the request is rejected with 403.

The configuration I applied looks like this:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: pod-reader
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get", "watch", "list"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: pod-reader
subjects:
- kind: ServiceAccount
  name: default
  namespace: default
roleRef:
  kind: ClusterRole
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io

(It is nearly the one from the docs on kubernetes io, just used the ServiceAccount as Subject and changed the resource to pods)

Then I applied the config and tried to access the pods via curl:

$ kubectl apply -f secrets.yaml 
clusterrole "pod-reader" created
clusterrolebinding "pod-reader" created
$ curl https://192.168.1.31:6443/v1/api/namespaces/default/pods --header "Authorization: Bearer $TOKEN" --insecure
{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {

  },
  "status": "Failure",
  "message": "forbidden: User \"system:serviceaccount:default:default\" cannot get path \"/v1/api/namespaces/default/pods\"",
  "reason": "Forbidden",
  "details": {

  },
  "code": 403
}

I guess the error message shows that the authentication part is ok, because it looks like the request was correctly identified as coming from the serviceaccount default:default. But what do I have to do to entitle this (or another service account) to access information about the pods or nodes?

I see this error when calling curl from outside a Pod, but also if I - for example - use the kubernetes java client to access the API from within a Pod using the secret mounted under /var/run/secrets.

I am a K8s newbie, so please forgive me if this is a stupid question.

Regarding the configuration: I have K8s 1.8 running on a cluster of Raspberry Pis with one Master and two Worker Nodes. I didn't pass much to kubeadm init, so I guess it should have the default configuration. FWIW kubectl describe shows this command for the apiserver:

  kube-apiserver
  --requestheader-group-headers=X-Remote-Group
  --service-account-key-file=/etc/kubernetes/pki/sa.pub
  --admission-control=Initializers,NamespaceLifecycle,LimitRanger,ServiceAccount,PersistentVolumeLabel,DefaultStorageClass,DefaultTolerationSeconds,NodeRestriction,ResourceQuota
  --secure-port=6443
  --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
  --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt
  --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key
  --advertise-address=192.168.1.31
  --service-cluster-ip-range=10.96.0.0/12
  --tls-cert-file=/etc/kubernetes/pki/apiserver.crt
  --tls-private-key-file=/etc/kubernetes/pki/apiserver.key
  --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt
  --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key
  --enable-bootstrap-token-auth=true
  --requestheader-username-headers=X-Remote-User
  --allow-privileged=true
  --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
  --requestheader-extra-headers-prefix=X-Remote-Extra-
  --requestheader-allowed-names=front-proxy-client
  --client-ca-file=/etc/kubernetes/pki/ca.crt
  --insecure-port=0
  --authorization-mode=Node,RBAC
  --etcd-servers=http://127.0.0.1:2379

Answer 1

I think you have a little issue in your curl path, it should be /api/v1/namespaces/... and not /v1/api/namespaces/.... See e.g. https://kubernetes.io/docs/api-reference/v1.8/#list-62