Kubernetes集群利用RBAC+ServiceAccount管理权限

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说明

这里简单记录一下如何通过k8s集群创建clusterrole配合serviceaccount实现权限控制，并且使用kubectl生成kubeconfig文件用于实现人员权限管理。

操作步骤

创建ClusterRole

这里参考了kube-apiserver初始化时生成的clusterrole.views权限设定

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apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: cluster-readonly
aggregationRule:
  clusterRoleSelectors:
  - matchLabels:
      rbac.example.com/aggregate-to-monitoring: "true"
rules:
- apiGroups:
  - ""
  resources:
  - configmaps
  - endpoints
  - nodes
  - nodes/metrics
  - nodes/proxy
  - nodes/status
  - persistentvolumeclaims
  - pods
  - replicationcontrollers
  - replicationcontrollers/scale
  - serviceaccounts
  - services
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - bindings
  - events
  - limitranges
  - namespaces/status
  - pods/log
  - pods/status
  - replicationcontrollers/status
  - resourcequotas
  - resourcequotas/status
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - namespaces
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - apps
  resources:
  - controllerrevisions
  - daemonsets
  - deployments
  - deployments/scale
  - replicasets
  - replicasets/scale
  - statefulsets
  - statefulsets/scale
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - autoscaling
  resources:
  - horizontalpodautoscalers
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - batch
  resources:
  - cronjobs
  - jobs
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - extensions
  resources:
  - daemonsets
  - deployments
  - deployments/scale
  - ingresses
  - networkpolicies
  - replicasets
  - replicasets/scale
  - replicationcontrollers/scale
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - policy
  resources:
  - poddisruptionbudgets
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - networking.k8s.io
  resources:
  - networkpolicies
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - metrics.k8s.io
  resources:
  - nodes
  - pods
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - monitoring.coreos.com
  resources:
  - alertmanagers
  - podmonitors
  - prometheuses
  - prometheusrules
  - servicemonitors
  verbs:
  - get
  - list
  - watch
- nonResourceURLs:
  - /metrics
  - /log
  - /logs
  - /healthz
  - /healthz/*
  verbs:
  - get

如果需要有Pod的exec权限可以创建一个ClusterRole

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apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: pod-exec
rules:
- apiGroups:
  - ""
  resources:
  - pods/exec
  verbs:
  - create

创建用户

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apiVersion: v1
kind: ServiceAccount
metadata:
  name: cluster-readonly
  namespace: default

创建ClusterRoleBinding

这里创建的ClusterRoleBinding是整个集群级别的

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apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: cluster-readonly
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-readonly
subjects:
- kind: ServiceAccount
  name: cluster-readonly
  namespace: default

创建RoleBinding

这里创建的RoleBinding可以具体到某一个namespace

这里创建一个default命名空间的RoleBinding

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apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: default-pod-exec
  namespace: default
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: pod-exec
subjects:
- kind: ServiceAccount
  name: cluster-readonly
  namespace: kube-system

获取ServiceAccount对应的Secret

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SECRET=$(kubectl -n default get serviceaccount cluster-readonly -o go-template='{{range .secrets}}{{.name}}{{end}}')

定义Kube-APIServer

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API_SERVER="https://192.168.1.100:6443"

获取集群CA证书

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kubectl -n default get secret ${SECRET} -o yaml | awk '/ca.crt:/{print $2}' | base64 -d > ca.crt

获取ServiceAccount对应的Token

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TOKEN=$(kubectl -n default get secret ${SECRET} -o go-template='{{.data.token}}')

定义kubeconfig文件名

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KUBECONFIG="cluster-readonly.kubeconfig"

创建kubeconfig

  • 设置kubeconfig集群信息
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kubectl config \
        set-cluster k8s-cluster \
        --server=${API_SERVER} \
        --embed-certs=true \
        --certificate-authority=./ca.crt \
        --kubeconfig=${KUBECONFIG}
  • 设置kubeconfig使用用户名+token认证
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kubectl config \
        set-credentials cluster-readonly \
        --token=`echo ${TOKEN} | base64 -d` \
        --kubeconfig=${KUBECONFIG}
  • 设置kubeconfig的context
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kubectl config \
        set-context default \
        --cluster=k8s-cluster \
        --user=cluster-readonly \
        --kubeconfig=${KUBECONFIG}
  • 将context设置为kubeconfig默认值
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kubectl config \
        use-context default \
        --kubeconfig=${KUBECONFIG}

验证权限

有权限的操作

获取Pod

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kubectl --kubeconfig=${KUBECONFIG} auth can-i get pod --all-namespaces

获取Pod日志

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kubectl --kubeconfig=${KUBECONFIG} auth can-i get pod --subresource=log --all-namespaces

获取ingress

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kubectl --kubeconfig=${KUBECONFIG} auth can-i get ingress --all-namespaces

返回结果

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yes

无权限的操作

创建容器

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kubectl --kubeconfig=${KUBECONFIG} auth can-i create pods --all-namespaces

删除容器

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kubectl --kubeconfig=${KUBECONFIG} auth can-i delete pods --all-namespaces

获取Secret

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kubectl --kubeconfig=${KUBECONFIG} auth can-i get secrets -n kube-system

返回结果

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no - no RBAC policy matched