1、一些概念

Rule：规则，一组属于不同 API Group 的操作集合；

Role：角色，用于定义一组对 Kubernetes API 对象操作的一组规则，范围限定在 namespace；

ClusterRole：集群角色，该角色不受 namespace 的限制；

Subject：对象，也就是规则作用的对象；

RoleBinding：将角色和对象进行绑定，范围限定在 namespace；

ClusterRoleBinding：将集群角色和对象进行绑定，不受 namespace 限制

ServiceAccount： 服务账户

2、Useraccount和ServiceAccount介绍

kubernetes中账户分为：UserAccounts（用户账户） 和 ServiceAccounts（服务账户） 两种：
UserAccount是给kubernetes集群外部用户使用的，如kubectl访问k8s集群要用Useraccount用户， kubeadm安装的k8s，默认的useraccount用户是kubernetes-admin；
k8s客户端(一般用:kubectl) 请求API Server（APIServer需要对客户端的请求做认证，认证成功才会执行）
　　
使用kubeadm安装的K8s，会在用户家目录下创建一个认证配置文件 .kube/config 这里面保存了客户端访问API Server的密钥相关信息，这样当用kubectl访问k8s时，它就会自动读取该配置文件，向API Server发起认证，然后完成操作请求。

ServiceAccount是Pod使用的账号，Pod容器的进程需要访问API Server时用的就ServiceAccount账户；
ServiceAccount仅局限它所在的namespace，每个namespace创建时都会自动创建一个default service account；创建Pod时，如果没有指定Service Account，Pod则会使用default Service Account。

3、ServiceAccount使用案例

3.1 创建sa，并绑定到pod

1、创建sa

[root@master ~]# kubectl create sa sa-lihaihui
serviceaccount/sa-lihaihui created
[root@master ~]# kubectl get sa
NAME          SECRETS   AGE
default       1         21d
sa-lihaihui   1         13s
[root@master ~]#

2、创建pod

[root@master ~]# mkdir /RBAC
[root@master ~]# cd /RBAC/
[root@master RBAC]# ls
[root@master RBAC]# 

[root@master RBAC]# cat sa-pod.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: sa-lihaihui
  namespace: default
  labels:
    app: sa-lihaihui
spec:
  serviceAccountName: sa-lihaihui # pod use service accout
  containers:
  - name:  sa-nginx
    ports:
    - containerPort: 80
    image: nginx
    imagePullPolicy: IfNotPresent
[root@master RBAC]# 
[root@master RBAC]# kubectl apply -f sa-pod.yaml 
pod/sa-lihaihui created
[root@master RBAC]# kubectl get pod
NAME                               READY   STATUS    RESTARTS   AGE
sa-lihaihui                        1/1     Running   0          4s

因为pod 会去访问k8s集群的apiserver，所以需要进入到pod里

[root@master RBAC]# kubectl exec -it sa-lihaihui -- bash
root@sa-lihaihui:/# 
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount# ls
ca.crt  namespace  token
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount# 
执行下面的命令去访问我们的apiserver 

root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount#  curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat ./token)"  https://kubernetes/api/v1/namespaces/kube-system
{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {
    
  },
  "status": "Failure",
  "message": "namespaces \"kube-system\" is forbidden: User \"system:serviceaccount:default:sa-lihaihui\" cannot get resource \"namespaces\" in API group \"\" in the namespace \"kube-system\"",
  "reason": "Forbidden",
  "details": {
    "name": "kube-system",
    "kind": "namespaces"
  },
  "code": 403
}root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount# 

3、对sa做授权

cluster-admin 这是一个权力非常大的clusterrole 集群角色
将default命名空间里的ss-gaoshuo服务账号绑定到 集群角色 cluster-admin 上

root@master RBAC]# kubectl create clusterrolebinding sa-test-lihaihui  --clusterrole=cluster-admin  --serviceaccount=default:sa-lihaihui
clusterrolebinding.rbac.authorization.k8s.io/sa-test-lihaihui created
[root@master RBAC]# 

查看有哪些服务账号进行了集群角色绑定

[root@master RBAC]# kubectl get clusterrolebinding |grep lihaihui
sa-test-lihaihui                                       ClusterRole/cluster-admin                                                          2m35s
[root@master RBAC]#  

4、再次请求，使用绑定好的集群角色

[root@master RBAC]# kubectl exec -it sa-lihaihui -- bash
root@sa-lihaihui:/# cd /var/run/secrets/kubernetes.io/serviceaccount/
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount#  curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat ./token)"  https://kubernetes/api/v1/namespaces/kube-system
{
  "kind": "Namespace",
  "apiVersion": "v1",
  "metadata": {
    "name": "kube-system",
    "uid": "b1b4554f-2ab4-4b88-afac-1eb3a8427607",
    "resourceVersion": "10",
    "creationTimestamp": "2023-08-16T07:25:47Z",
    "managedFields": [
      {
        "manager": "kube-apiserver",
        "operation": "Update",
        "apiVersion": "v1",
        "time": "2023-08-16T07:25:47Z",
        "fieldsType": "FieldsV1",
        "fieldsV1": {"f:status":{"f:phase":{}}}
      }
    ]
  },
  "spec": {
    "finalizers": [
      "kubernetes"
    ]
  },
  "status": {
    "phase": "Active"
  }
}
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount#

可以看到"phase": “Active”，访问成功！

4、自己创建role和clusterrole

1、自己创建一个role

自己赋予role的访问权限

[root@master RBAC]# vim role.yaml
[root@master RBAC]# cat role.yaml 
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: default
  name: pod-reader
rules:
- apiGroups: [""] # "" 标明 core API 组
  resources: ["pods"]  
  verbs: ["get", "watch", "list"]
[root@master RBAC]# 
[root@master RBAC]# kubectl apply -f role.yaml 
role.rbac.authorization.k8s.io/pod-reader created
[root@master RBAC]# kubectl get role
NAME         CREATED AT
pod-reader   2023-09-07T03:47:00Z
[root@master RBAC]# 

2、sa绑定role

[root@master RBAC]# kubectl create rolebinding sa-test-lihaihui  --role=pod-reader --serviceaccount=default:sa-lihaihui
rolebinding.rbac.authorization.k8s.io/sa-test-lihaihui created

查看已经绑定的rolebinding

[root@master RBAC]# kubectl get rolebinding
NAME               ROLE              AGE
sa-test-lihaihui   Role/pod-reader   28s
[root@master RBAC]# 

3、创建一个clusterrole

[root@k8smaster sa]# cat clusterrole.yaml 
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  # "namespace" 被忽略，因为 ClusterRoles 不受名字空间限制
  name: secret-reader
rules:
- apiGroups: [""]
  # 在 HTTP 层面，用来访问 Secret 资源的名称为 "secrets"
  resources: ["secrets"]  #具体的资源对象
  verbs: ["get", "watch", "list"]  #动作
[root@k8smaster sa]# kubectl apply -f clusterrole.yaml 
clusterrole.rbac.authorization.k8s.io/secret-reader created
[root@k8smaster sa]# 
[root@k8smaster sa]# kubectl get clusterrole
secret-reader                                                          

4、将sa绑定到clusterrole

[root@master RBAC]# kubectl create clusterrolebinding sa-test-lihaihui-2  --clusterrole=secret-reader  --serviceaccount=default:sa-lihaihui
clusterrolebinding.rbac.authorization.k8s.io/sa-test-lihaihui-2 created

[root@k8smaster sa]# kubectl get clusterrolebinding
NAME                                                   ROLE                                                                               AGE
sa-test-lihaihui                                       ClusterRole/cluster-admin                                                          15m
sa-test-lihaihui-2                                     ClusterRole/secret-reader 

5、验证

进入sa-lihaihui启动的pod，去访问apiserver里的pod资源和secret资源

[root@master RBAC]# kubectl get pod
NAME                               READY   STATUS    RESTARTS   AGE
configmap-demo-pod                 1/1     Running   5          19h
configmap-nginx                    1/1     Running   1          19h
mysql                              1/1     Running   4          2d18h
nginx                              1/1     Running   3          2d
nginx-configmap-test               1/1     Running   1          19h
sa-lihaihui                        1/1     Running   0          30m

[root@master RBAC]# kubectl exec -it sa-lihaihui -- bash
root@sa-lihaihui:
root@sa-lihaihui:~# cd /var/run/secrets/kubernetes.io/serviceaccount/
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount# 
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount# curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat ./token)"  https://kubernetes/api/v1/pods  
root@sa-lihaihui:/var/run/secrets/kubernetes.io/serviceaccount# curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat .token)"  https://kubernetes/api/v1/secrets