kubeadm doesn't support ABAC correctly

[msnelling]

Is this a BUG REPORT or FEATURE REQUEST?:
/kind bug

What happened:
I attempted to create a cluster using the kubeadm tool with ABAC authorisation enabled using the below configuration files.

~/config.yaml

apiVersion: kubeadm.k8s.io/v1alpha1
kind: MasterConfiguration
networking:
  podSubnet: 10.244.0.0/16
authorizationModes:
- Node
- RBAC
- ABAC
apiServerExtraArgs:
  basic-auth-file: /etc/kubernetes/basic_auth.csv
  authorization-policy-file: /etc/kubernetes/abac_policy.json

~/basic_auth.csv

admin,admin,1,"system:masters"

~/abac_policy.json

{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"user":"*", "nonResourcePath": "*", "readonly": true}}
{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"user":"admin", "namespace": "*", "resource": "*", "apiGroup": "*"}}
{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"group":"system:serviceaccounts", "namespace": "*", "resource": "*", "apiGroup": "*", "nonResourcePath": "*"}}

The kubeadm command hangs with the following output...

[init] Using Kubernetes version: v1.9.3
[init] Using Authorization modes: [Node RBAC ABAC]
[preflight] Running pre-flight checks.
        [WARNING FileExisting-crictl]: crictl not found in system path
[preflight] Starting the kubelet service
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [k8s-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [####### #######]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "scheduler.conf"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] Waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests".
[init] This might take a minute or longer if the control plane images have to be pulled.

It looks like the kube-apiserver container is constantly restarted.

The log output from the kube-apiserver container gives

I0306 12:39:33.179719       1 server.go:121] Version: v1.9.3
invalid authentication config: open /etc/kubernetes/basic_auth.csv: no such file or directory

What you expected to happen:
I expected the kube-apiserver to start.

How to reproduce it (as minimally and precisely as possible):

mkdir -p /etc/kubernetes
cp ~/basic_auth.csv /etc/kubernetes
cp ~/abac_policy.json /etc/kubernetes
kubeadm init --config ~/config.yaml

Anything else we need to know?:

Environment:

• Kubernetes version (use kubectl version): v1.9.3
• Cloud provider or hardware configuration: Bare metal
• OS (e.g. from /etc/os-release): 16.04.4 LTS (Xenial Xerus)
• Kernel (e.g. uname -a): Linux k8s-master 4.4.0-116-generic PreStart and PostStop event hooks #140-Ubuntu SMP Mon Feb 12 21:23:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
• Install tools:
• Others:

[msnelling]

It seems that maybe the /etc/kubernetes/basic_auth.csv and /etc/kubernetes/abac_policy.json files are not mounted inside the kube-apiserver container.
I tried using the following extra volumes stanza but I couldn't get it to work with files, it only seems to work with directories.

apiServerExtraVolumes:
- name: <value|string>
  hostPath: <value|string>
  mountPath: <value|string>

If I try mounting a directory containing the two files and specify the new locations in the config it still looks for them in the default location! See the generated /etc/kubernetes/manifests/kube-apiserver.yaml below, it has two entries for the --authorization-policy-file option, the second seemingly overrides the first.

apiVersion: v1
kind: Pod
metadata:
  annotations:
    scheduler.alpha.kubernetes.io/critical-pod: ""
  creationTimestamp: null
  labels:
    component: kube-apiserver
    tier: control-plane
  name: kube-apiserver
  namespace: kube-system
spec:
  containers:
  - command:
    - kube-apiserver
    - --authorization-policy-file=/etc/kubernetes/users/abac_policy.json
    - --basic-auth-file=/etc/kubernetes/users/basic_auth.csv
    - --service-account-key-file=/etc/kubernetes/pki/sa.pub
    - --tls-private-key-file=/etc/kubernetes/pki/apiserver.key
    - --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key
    - --admission-control=Initializers,NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,NodeRestriction,ResourceQuota
    - --enable-bootstrap-token-auth=true
    - --allow-privileged=true
    - --requestheader-group-headers=X-Remote-Group
    - --advertise-address=#######
    - --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
    - --insecure-port=0
    - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
    - --requestheader-extra-headers-prefix=X-Remote-Extra-
    - --tls-cert-file=/etc/kubernetes/pki/apiserver.crt
    - --secure-port=6443
    - --requestheader-username-headers=X-Remote-User
    - --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt
    - --requestheader-allowed-names=front-proxy-client
    - --service-cluster-ip-range=10.96.0.0/12
    - --client-ca-file=/etc/kubernetes/pki/ca.crt
    - --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt
    - --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key
    - --authorization-policy-file=/etc/kubernetes/abac_policy.json
    - --authorization-mode=Node,RBAC,ABAC
    - --etcd-servers=http://127.0.0.1:2379
    image: gcr.io/google_containers/kube-apiserver-amd64:v1.9.3
    livenessProbe:
      failureThreshold: 8
      httpGet:
        host: #######
        path: /healthz
        port: 6443
        scheme: HTTPS
      initialDelaySeconds: 15
      timeoutSeconds: 15
    name: kube-apiserver
    resources:
      requests:
        cpu: 250m
    volumeMounts:
    - mountPath: /etc/kubernetes/pki
      name: k8s-certs
      readOnly: true
    - mountPath: /etc/ssl/certs
      name: ca-certs
      readOnly: true
    - mountPath: /etc/kubernetes/users
      name: users
      readOnly: true
  hostNetwork: true
  volumes:
  - hostPath:
      path: /etc/kubernetes/pki
      type: DirectoryOrCreate
    name: k8s-certs
  - hostPath:
      path: /etc/ssl/certs
      type: DirectoryOrCreate
    name: ca-certs
  - hostPath:
      path: /etc/kubernetes/users
      type: DirectoryOrCreate
    name: users
status: {}

[timothysc]

@msnelling - We generally discourage ABAC enablement, but it does look like an over-ride issue.

Where possible please open issues against the https://github.com/kubernetes/kubeadm repo.