No Certificate Authority file set for etcd

api_server_etcd_ca_file

Severity

high

Vendor

Kubernetes

Resource

kube-apiserver

Description

etcd is a distributed key-value store, where Kubernetes stores configuration and state information. Anyone who can write to etcd can effectively control a Kubernetes cluster.

By using authenticity protection, the communication can be protected against man-in-the-middle attacks/session hijacking and the insertion of false information into sessions.

The communication session is protected by utilizing transport encryption protocols, such as TLS. TLS provides the Kubernetes API Server and etcd with a means to be able to authenticate sessions and encrypt traffic.

The parameter etcd-cafile which gives the location of a valid SSL Certificate Authority file must be set to enable encrypted communication for etcd.

Learn more about this topic at PKI certificates and requirements.

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 `--etcd-cafile` command argument means TLS encryption for client connections is not used.

Mitigation / Fix

apiVersion: v1
kind: Pod
metadata:
  name: good
spec:
  containers:
  - command:
    - kube-apiserver
    - --etcd-cafile (1)
    - --etcd-certfile=/path/to/cert
    - --etcd-keyfile=/path/to/key
    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 `--etcd-cafile` command argument means TLS encryption for client connections is used.