K8S RBAC

API Server 内部通过用户认证后，然后进入授权流程。对合法用户进行授权并且随后在用户访问时进行鉴权，是权限管理的重要环节。

在 kubernetes 集群中，各种操作权限是赋予角色(Role 或者 ClusterRole）的。通过创建 RoleBinding 或者 ClusterBinding 把 用户(User),用户组（Group）或服务账号（Service Account）绑定在 Role 或 ClusterRole 上。这样用户，用户组或者服务账号就有了相对应的操作权限。

这里有个需要注意的地方

ClusterRoleBinding 只能绑定 ClusterRole,而 RoleBinding 可以绑定 Role 或者 ClusterRole。

根据上图：

1.User1 通过 RoleBinding 把 Role 绑定，可以在 Namespace A 获得 Role 中的权限；

2.User2 和 User3 通过 RoleBinding 把 ClusterRole 绑定，这两个用户即可以在 Namespace B 空间中获得 ClusterRole 权限；

3.如果 User1 通过 ClusterRoleBinding 把 ClusterRole 绑定，这个用户即可在所有的 Namespace 空间中获得 ClusterRole 权限；

创建 role

su - klvchen
cd sa/
kubectl create role pods-reader --verb=get,list,watch --resource=pods --dry-run -o yaml > role-demo.yaml
kubectl apply -f role-demo.yaml
kubectl get role
kubectl describe role pods-reader

创建 rolebinding

kubectl create rolebinding klvchen-read-pods --role=pods-reader --user=klvchen --dry-run -o yaml > rolebinding-demo.yaml
kubectl apply -f rolebinding-demo.yaml
kubectl describe rolebinding klvchen-read-pods

测试账号

kubectl config use-context klvchen@kubernetes
kubectl config view
kubectl get pods

为了方便测试，创建一个新的用户 ik8s

useradd ik8s
cp -rf .kube/ /home/ik8s/
chown  -R ik8s. /home/ik8s/
su - ik8s
kubectl config use-context klvchen@kubernetes
kubectl config view

创建 clusterrole

kubectl create clusterrole cluster-reader --verb=get,list,watch --resource=pods -o yaml --dry-run > clusterrole-demo.yaml
kubectl apply -f clusterrole-demo.yaml 
kubectl get rolebinding
# 删除 klvchen-read-pods ，解除 role 角色 pods-reader 和 user 用户 klvchen 的绑定关系
kubectl delete rolebinding klvchen-read-pods

创建 clusterrolebinding

kubectl create clusterrolebinding klvchen-read-all-pods --clusterrole=cluster-reader --user=klvchen --dry-run -o yaml > clusterrolebinding-demo.yaml
kubectl apply -f clusterrolebinding-demo.yaml
kubectl describe clusterrolebinding klvchen-read-all-pods

测试

#切换到 ik8s 账户
kubectl get pods -n kube-system
# 所有命名空间都可以正常显示 pods

使用 rolebinding 关联 clusterrole

kubectl delete clusterrolebinding klvchen-read-all-pods
kubectl create rolebinding klvchen-read-pods --clusterrole=cluster-reader --user=klvchen --dry-run -o yaml > rolebinding-clusterrole-demo.yaml
kubectl apply -f rolebinding-clusterrole-demo.yaml 
#测试
#切换到 ik8s 账户
kubectl get pods
# 只有默认的命名空间可以正常显示 pods

查看 k8s 集群中 admin 拥有的权限

kubectl get clusterrole admin -o yaml
kubectl get clusterrolebinding cluster-admin -o yaml
[root@master ~]# kubectl get clusterrolebinding cluster-admin -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  creationTimestamp: 2018-11-07T10:12:36Z
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: cluster-admin
  resourceVersion: "107"
  selfLink: /apis/rbac.authorization.k8s.io/v1/clusterrolebindings/cluster-admin
  uid: a6252a77-e275-11e8-8c94-cad98100ca95
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:masters                     # admin 所在的组是 system:masters
# kubernetes-admin 是属于 system:masters 组
[root@master ~]# kubectl config view
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://192.168.0.205:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: klvchen
  name: klvchen@kubernetes
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: klvchen
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED
- name: kubernetes-admin
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED

查看对应的证书，这里注意了，证书的有效期为1年

[root@master ~]# cd /etc/kubernetes/pki/
[root@master pki]# openssl x509 -in ./apiserver-kubelet-client.crt -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 3302614080992031284 (0x2dd53e0237bbb234)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN=kubernetes
        Validity
            Not Before: Nov  7 10:11:55 2018 GMT
            Not After : Nov  7 10:11:56 2019 GMT
        Subject: O=system:masters, CN=kube-apiserver-kubelet-client
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
...后面信息忽略