Service account lookup not set

api_server_service_account_lookup

Severity

low

Vendor

Kubernetes

Resource

kube-apiserver

Description

The Kubernetes API Server validates and configures data for the api objects which include pods, services, replication controllers, and others.

When --service-account-lookup is not enabled, the API Server does not verify that the service account token mentioned in the request is actually present in etcd. This allows using a service account token even after the corresponding service account is deleted.

Examples

apiVersion: v1
kind: Pod
metadata:
  name: bad (1)
spec:
  containers:
  - command:
    - kube-apiserver
    image: gcr.io/google_containers/kube-apiserver-amd64:v1.9.0
    name: bad-container
    livenessProbe:
      failureThreshold: 8
      httpGet:
        host: 127.0.0.1
        path: /health
        port: 6443
        scheme: HTTPS
      initialDelaySeconds: 15
      timeoutSeconds: 15
    resources:
      requests:
        cpu: 250m
    volumeMounts:
    - mountPath: /etc/kubernetes/
      name: k8s
      readOnly: true
    - mountPath: /etc/ssl/certs
      name: certs
    - mountPath: /etc/pki
      name: pki
  hostNetwork: true
  volumes:
  - hostPath:
      path: /etc/kubernetes
    name: k8s
  - hostPath:
      path: /etc/ssl/certs
    name: certs
  - hostPath:
      path: /etc/pki
    name: pki

1	Missing `-service-account-lookup` command argument means API Server does not validate that the service account token mentioned in the request is actually present in etcd.

Mitigation / Fix

apiVersion: v1
kind: Pod
metadata:
  name: good
spec:
  containers:
  - command:
    - kube-apiserver
    - --service-account-lookup=true (1)
    image: gcr.io/google_containers/kube-apiserver-amd64:v1.9.0
    name: good-container
    livenessProbe:
      failureThreshold: 8
      httpGet:
        host: 127.0.0.1
        path: /health
        port: 6443
        scheme: HTTPS
      initialDelaySeconds: 15
      timeoutSeconds: 15
    resources:
      requests:
        cpu: 250m
    volumeMounts:
    - mountPath: /etc/kubernetes/
      name: k8s
      readOnly: true
    - mountPath: /etc/ssl/certs
      name: certs
    - mountPath: /etc/pki
      name: pki
  hostNetwork: true
  volumes:
  - hostPath:
      path: /etc/kubernetes
    name: k8s
  - hostPath:
      path: /etc/ssl/certs
    name: certs
  - hostPath:
      path: /etc/pki
    name: pki

1	Provided `-service-account-lookup` command argument means API Server validates that the service account token mentioned in the request is actually present in etcd.