技术教程 编程教程 kubernetes学习笔记之十:RBAC 正文

kubernetes学习笔记之十:RBAC

2023-03-14,,

第一章、RBAC介绍

在Kubernetes中，授权有ABAC（基于属性的访问控制）、RBAC（基于角色的访问控制）、Webhook、Node、AlwaysDeny（一直拒绝）和AlwaysAllow（一直允许）这6种模式。从1.6版本起，Kubernetes 默认启用RBAC访问控制策略。从1.8开始，RBAC已作为稳定的功能。通过设置–authorization-mode=RBAC，启用RABC。在RABC API中，通过如下的步骤进行授权：）定义角色：在定义角色时会指定此角色对于资源的访问控制的规则；）绑定角色：将主体与角色进行绑定，对用户进行访问授权。

1、 角色和集群角色

在RBAC API中，角色包含代表权限集合的规则。在这里，权限只有被授予，而没有被拒绝的设置。在Kubernetes中有两类角色，即普通角色和集群角色。可以通过Role定义在一个命名空间中的角色，或者可以使用ClusterRole定义集群范围的角色。一个角色只能被用来授予访问单一命令空间中的资源。

集群角色(ClusterRole)能够被授予如下资源的权限：

    集群范围的资源（类似于Node）

    非资源端点（类似于”/healthz”）

    集群中所有命名空间的资源（类似Pod）

2、角色绑定和集群角色绑定

角色绑定用于将角色与一个或一组用户进行绑定，从而实现将对用户进行授权的目的。主体分为用户、组和服务帐户。角色绑定也分为角色普通角色绑定和集群角色绑定。角色绑定只能引用同一个命名空间下的角色。

角色绑定也可以通过引用集群角色授予访问权限，当主体对资源的访问仅限与本命名空间，这就允许管理员定义整个集群的公共角色集合，然后在多个命名空间中进行复用。

集群角色可以被用来在集群层面和整个命名空间进行授权。

3、资源

在Kubernets中，主要的资源包括：Pods、Nodes、Services、Deployment、Replicasets、Statefulsets、Namespace、Persistents、Secrets和ConfigMaps等。另外，有些资源下面存在子资源，例如：Pod下就存在log子资源

4、主体

RBAC授权中的主体可以是组，用户或者服务帐户。用户通过字符串表示，比如“alice”、 “bob@example.com”等，具体的形式取决于管理员在认证模块中所配置的用户名。system:被保留作为用来Kubernetes系统使用，因此不能作为用户的前缀。组也有认证模块提供，格式与用户类似。

第二章、简单示例

1、使用RoleBanding将用户绑定到Role上

查看命令帮助及格式

[root@k8s-master01 ~]# kubectl create role -h  #查看创建role的命令帮助，以及一些简单的示例

[root@k8s-master01 RBAC]# kubectl create role pods-reader --verb=get,list,watch --resource=pods --dry-run -o yaml  #通过 -o参数导出yaml格式，可以大致看到Role是如何定义的

[root@k8s-master01 RBAC]# cat role-demo.yaml  #最后完成的yaml文件如下

apiVersion: rbac.authorization.k8s.io/v1

kind: Role

metadata:

  name: pods-reader

  namespace: default  #名称空间名称

rules:

- apiGroups:

  - ""

  resources:  #包含哪些资源

  - pods

  verbs:       #对以上资源允许进行哪些操作

  - get

  - list

  - watch

创建role

[root@k8s-master01 RBAC]# kubectl apply -f role-demo.yaml

role.rbac.authorization.k8s.io "pods-reader" created

[root@k8s-master01 RBAC]# kubectl get role   #查看role的信息

NAME          AGE

pods-reader   8s

[root@k8s-master01 RBAC]# kubectl describe role pods-reader  #查看pods-reader 的详细信息

Name:         pods-reader

Labels:       <none>

Annotations:  kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"rbac.authorization.k8s.io/v1","kind":"Role","metadata":{"annotations":{},"name":"pods-reader","namespace":"default"},"rules":[{"apiGroup...

PolicyRule:

  Resources  Non-Resource URLs  Resource Names  Verbs

  ---------     -----------------         --------------          -----

  pods          []                            []                         [get list watch]

#

Resources：资源类别，表示对该资源类别下的所有资源进行操作

Non-Resource URLs：非资源URL，对某些资源进行某种特殊操作的存在

Resource Names：对资源类别下某个或多个资源进行操作

Verbs：操作的类型　　

 创建一个RoleBinding，将用户qiangungun(该用户在上一章节serviceaccount中已经被创建)绑定到pods-reader 这个role上去

[root@k8s-master01 ~]# kubectl create rolebinding -h  #查看命令帮助

 kubectl create rolebinding  qiangungun-read-pods --role=pods-reader --user=qiangungun  --dry-run -o yaml  #创建名称为qiangungun-read-pods的rolebinding，绑定到名称为pods-reader的role上

[root@k8s-master01 RBAC]# cat rolebinding-demo.yaml

apiVersion: rbac.authorization.k8s.io/v1

kind: RoleBinding

metadata:

  name: qiangungun-read-pods

roleRef:   #role引用，表示引用哪个role

  apiGroup: rbac.authorization.k8s.io

  kind: Role

  name: pods-reader

subjects:  #动作的执行主题

- apiGroup: rbac.authorization.k8s.io

  kind: User

  name: qiangungun

[root@k8s-master01 RBAC]# kubectl describe rolebinding qiangungun-read-pods

Name:         qiangungun-read-pods

Labels:       <none>

Annotations:  kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"rbac.authorization.k8s.io/v1","kind":"RoleBinding","metadata":{"annotations":{},"name":"qiangungun-read-pods","namespace":"default"},"ro...

Role:

  Kind:  Role

  Name:  pods-reader

Subjects:

  Kind  Name        Namespace

  ----  ----        ---------

  User  qiangungun 　　

验证操作

[root@k8s-master01 RBAC]# kubectl config use-context qiangungun@kubernetes #前后当前上下文到qiangungun用户

Switched to context "qiangungun@kubernetes".

[root@k8s-master01 RBAC]# kubectl get pods    #获取当前名称空间的pod信息，可以看到能够正常显示

NAME                             READY     STATUS    RESTARTS   AGE

myapp-deploy-5cfd895984-262kz    /       Running             3d

myapp-deploy-5cfd895984-7whdn    /       Running             3d

myapp-deploy-5cfd895984-lg8sh    /       Running             3d

myapp-deploy-5cfd895984-m7h5j    /       Running             3d

myapp-deploy-5cfd895984-zd9cm    /       Running             3d

[root@k8s-master01 RBAC]# kubectl get pods -n kube-system    #查看其它空间pod的信息，可以看到提示没有权限，即验证RoleBanding的权限只对当前的名称空间生效

Error from server (Forbidden): pods is forbidden: User "qiangungun" cannot list pods in the namespace "kube-system"

2、使用ClusterRoleBanding将用户绑定到ClusterRole上

创建一个ClusterRole

[root@k8s-master01 RBAC]# kubectl config use-context kubernetes-admin@kubernetes #切换上下文

Switched to context "kubernetes-admin@kubernetes".

[root@k8s-master01 RBAC]# kubectl create clusterrole -h

[root@k8s-master01 RBAC]# kubectl create clusterrole cluster-reader --verb=get,list,watch --resource=pods -o yaml --dry-run

[root@k8s-master01 RBAC]# cat clusterrole-cluster.yaml

apiVersion: rbac.authorization.k8s.io/v1

kind: ClusterRole

metadata:

  name: cluster-reader #ClusterRole属于集群级别，所有不可以定义namespace

rules:

- apiGroups:

  - ""

  resources:

  - pods

  verbs:

  - get

  - list

  - watch

[root@k8s-master01 RBAC]# kubectl apply -f clusterrole-cluster.yaml

[root@k8s-master01 RBAC]# useradd admin

[root@k8s-master01 RBAC]# cp -rp ~/.kube/ /home/admin

[root@k8s-master01 RBAC]# chown -R admin:admin /home/admin

[root@k8s-master01 RBAC]# su - admin

[admin@k8s-master01 ~]$ kubectl config use-context qiangungun@kubernetes

[admin@k8s-master01 ~]$ kubectl config view　　

创建一个ClusterRoleBinding,将用户qiangungun绑定到cluster-reader这个ClusterRole上面去

[root@k8s-master01 RBAC]# kubectl delete rolebinding qiangungun-read-pods   #root用户

[admin@k8s-master01 ~]$ kubectl get pods   #admin用户下验证

Error from server (Forbidden): pods is forbidden: User "qiangungun" cannot list pods in the namespace "default"

[root@k8s-master01 RBAC]# kubectl create clusterrolebinding -h

[root@k8s-master01 RBAC]# kubectl create clusterrolebinding qiangungun-read-all-pods --clusterrole=cluster-reader --user=qiangungun --dry-run -o yaml #创建名称为qiangungun-read-all-pods的才clusterrolebinding，将名称为cluster-reader的clusterrole绑定到用户名称为qiangungun上

[root@k8s-master01 RBAC]# cat clusterrolebinding-demo.yaml

apiVersion: rbac.authorization.k8s.io/v1

kind: ClusterRoleBinding

metadata:

  creationTimestamp: null

  name: qiangungun-read-all-pods

roleRef:

  apiGroup: rbac.authorization.k8s.io

  kind: ClusterRole

  name: cluster-reader

subjects:

- apiGroup: rbac.authorization.k8s.io

  kind: User

  name: qiangungun

[root@k8s-master01 RBAC]# kubectl apply -f clusterrolebinding-demo.yaml

[root@k8s-master01 RBAC]# kubectl describe clusterrolebinding qiangungun-read-all-pods 　　

验证

#切换到admin用户终端下

[admin@k8s-master01 ~]$ kubectl get pods  #可以查看当前名称空间pod信息

NAME                             READY     STATUS    RESTARTS   AGE

myapp-deploy-5cfd895984-262kz    /       Running             3d

myapp-deploy-5cfd895984-7whdn    /       Running             3d

myapp-deploy-5cfd895984-lg8sh    /       Running             3d

myapp-deploy-5cfd895984-m7h5j    /       Running             3d

myapp-deploy-5cfd895984-zd9cm    /       Running             3d

[admin@k8s-master01 ~]$ kubectl get pods -n ingress-nginx  #可以查看其他空间的pod信息

NAME                                        READY     STATUS    RESTARTS   AGE

default-http-backend-66c4fbf5b4-m8d6j       /       Running             24d

nginx-ingress-controller-64bcff8657-6j4tq   /       Running             24d

[admin@k8s-master01 ~]$ kubectl delete pod myapp-deploy-5cfd895984-262kz  #无法删除pod

Error from server (Forbidden): pods "myapp-deploy-5cfd895984-262kz" is forbidden: User "qiangungun" cannot delete pods in the namespace "default"

3、使用RoleBinding绑定ClusterRole　

创建一个RoleBinding(ClusterRole使用以及存在的)，并将用户绑定到ClusterRole上

[root@k8s-master01 RBAC]# kubectl delete clusterrolebinding qiangungun-read-all-pods #为了避免冲突，先将之前的clusterrolebinding删除

clusterrolebinding.rbac.authorization.k8s.io "qiangungun-read-all-pods" deleted

[root@k8s-master01 RBAC]#kubectl create rolebinding qiangungun-read-pods --clusterrole=cluster-reader --user=qiangungun --dry-run -o yam

[root@k8s-master01 RBAC]# cat rolebinding-cluster-demo.yaml

apiVersion: rbac.authorization.k8s.io/v1

kind: RoleBinding

metadata:

  name: qiangungun-read-pods

roleRef:

  apiGroup: rbac.authorization.k8s.io

  kind: ClusterRole

  name: cluster-reader

subjects:

- apiGroup: rbac.authorization.k8s.io

  kind: User

  name: qiangungun

[root@k8s-master01 RBAC]# kubectl apply -f rolebinding-cluster-demo.yaml

rolebinding.rbac.authorization.k8s.io "qiangungun-read-pods" created

[root@k8s-master01 RBAC]# kubectl describe rolebinding qiangungun-read-pods 　　

验证：

#admin用户终端下

[admin@k8s-master01 ~]$ kubectl get pods  #可以获取当前名称空间的pod信息

NAME                             READY     STATUS    RESTARTS   AGE

myapp-deploy-5cfd895984-262kz    /       Running             3d

myapp-deploy-5cfd895984-7whdn    /       Running             3d

myapp-deploy-5cfd895984-lg8sh    /       Running             3d

myapp-deploy-5cfd895984-m7h5j    /       Running             3d

myapp-deploy-5cfd895984-zd9cm    /       Running             3d

[admin@k8s-master01 ~]$ kubectl get pods -n ingress-nginx   #不可用获取其他名称空间的信息

Error from server (Forbidden): pods is forbidden: User "qiangungun" cannot list pods in the namespace "ingres

4、使用RoleBinding绑定集群自带的ClusterRole　　

[root@k8s-master01 RBAC]# kubectl get clusterrole  #查看当前集群存在的clusterrole

[root@k8s-master01 RBAC]# kubectl create rolebinding default-ns-admin --clusterrole=admin --user=qiangungun  --dry-run -o yaml #将qiangungun用户绑定到名称为admin的clusterrole上，可以使用get查看admin的配置

[root@k8s-master01 RBAC]# cat rolebinding-cluster-admin-demo.yaml

piVersion: rbac.authorization.k8s.io/v1

kind: RoleBinding

metadata:

  name: default-ns-admin

  namespace: default

roleRef:

  apiGroup: rbac.authorization.k8s.io

  kind: ClusterRole

  name: admin

subjects:

- apiGroup: rbac.authorization.k8s.io

  kind: User

  name: qiangungun

[root@k8s-master01 RBAC]# kubectl apply -f rolebinding-cluster-admin-demo.yaml

[root@k8s-master01 RBAC]# kubectl describe rolebinding default-ns-admin 　　

验证

#admin用户终端下

[admin@k8s-master01 ~]$ kubectl get pods  #可以获取当前名称空间的pod信息

NAME                             READY     STATUS    RESTARTS   AGE

myapp-deploy-5cfd895984-262kz    /       Running             3d

myapp-deploy-5cfd895984-7whdn    /       Running             3d

myapp-deploy-5cfd895984-lg8sh    /       Running             3d

myapp-deploy-5cfd895984-m7h5j    /       Running             3d

myapp-deploy-5cfd895984-zd9cm    /       Running             3d

......

[admin@k8s-master01 ~]$ kubectl delete pod myapp-deploy-5cfd895984-262kz   #可以删除当前名称空间的pod

pod "myapp-deploy-5cfd895984-262kz" deleted

[admin@k8s-master01 ~]$ kubectl get deploy  #可以查看名称空间中的其他资源，如deployment

NAME              DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE

nginx-deploy                                                                     3d

[admin@k8s-master01 ~]$ kubectl delete deployment nginx-deploy  #可以删除当前名称空间的其他资源，如deployment

deployment.extensions "nginx-deploy" deleted

[admin@k8s-master01 ~]$ kubectl get pods -n kube-system  #对其名称空间没有任何权限

Error from server (Forbidden): pods is forbidden: User "qiangungun" cannot list pods in the namespace "kube-system"

第三章、Role、CluseterRole、RoleBinding、ClusterRoleBinding在系统的相关联系

[root@k8s-master01 RBAC]# kubectl get clusterrolebinding #查看集群中的clusterrolebingding

NAME                                                   AGE

cluster-admin                                          31d

......

[root@k8s-master01 RBAC]# kubectl get clusterrolebinding cluster-admin -o yaml  #获取名称为cluster-admin的clusterrolebingding配置信息

apiVersion: rbac.authorization.k8s.io/v1

kind: ClusterRoleBinding

metadata:

  annotations:

    rbac.authorization.kubernetes.io/autoupdate: "true"

  creationTimestamp: --30T02::22Z

  labels:

    kubernetes.io/bootstrapping: rbac-defaults

  name: cluster-admin

  resourceVersion: ""

  selfLink: /apis/rbac.authorization.k8s.io/v1/clusterrolebindings/cluster-admin

  uid: 07b1d436-dbec-11e8--5254001b07db

roleRef:

  apiGroup: rbac.authorization.k8s.io

  kind: ClusterRole

  name: cluster-admin

subjects:

- apiGroup: rbac.authorization.k8s.io

  kind: Group   #类型是一个组

  name: system:masters   #这个组中包含了kubernetes-admin这个用户，而这个用户是默认的当前使用用户

[root@k8s-master01 RBAC]# kubectl config view

apiVersion: v1

clusters:

- cluster:

    certificate-authority-data: REDACTED

    server: https://172.16.150.212:6443

  name: kubernetes

contexts:

- context:

    cluster: kubernetes

    user: kubernetes-admin  #默认使用的当前用户

  name: kubernetes-admin@kubernetes

- context:

    cluster: kubernetes

    user: qiangungun

  name: qiangungun@kubernetes

current-context: kubernetes-admin@kubernetes  #当前的使用sa

kind: Config

preferences: {}

users:

- name: kubernetes-admin

  user:

    client-certificate-data: REDACTED

    client-key-data: REDACTED

- name: qiangungun

  user:

    client-certificate-data: REDACTED

    client-key-data: REDACTED

[root@k8s-master01 RBAC]# cd /etc/kubernetes/pki/

[root@k8s-master01 pki]# openssl x509  -in ./apiserver-kubelet-client.crt -text -noout #查看证书签发的内容

Certificate:

    Data:

        Version:  (0x2)

        Serial Number:  (0x2c3ce992f3e5d4dd)

    Signature Algorithm: sha256WithRSAEncryption

        Issuer: CN=kubernetes

        Validity

            Not Before: Oct  ::  GMT

            Not After : Oct  ::  GMT

        Subject: O=system:masters, CN=kube-apiserver-kubelet-client  #kubernetes-admin用户之所以属于system:master这个组，是因为在它的的证书中定义的，O表示组,如果以后我们想一次授权多个用户，可以将这些用户添加至一个组内，然后给这个组授权即可

        Subject Public Key Info:

            Public Key Algorithm: rsaEncryption

                Public-Key: ( bit)

              .....

#如果RoleBinding或者ClusterRoleBinding的对象是serviceaccount，，那么任意一个pod(spec.serviceAcountName中定义)如果启动时以这个serviceaccount name作为它是以的serviceaccount，那么pod中的应用程序也同时拥有了这个serviceaccount的权限，也就是拥有该serviceaccount绑定的Role或者ClusterRole的权限。系统上一下特殊的pod可能需要做这样的设置，下面我就以集群创建时使用的flannel网络插件为示例讲解

查看flannel的配置

[root@k8s-master01 kubernetes]# cat kube-flannel.yml   #flannel的配置文件

---

kind: ClusterRole    #定义一个ClusterRole

apiVersion: rbac.authorization.k8s.io/v1beta1

metadata:

  name: flannel

rules:

  - apiGroups:

      - ""

    resources:

      - pods

    verbs:

      - get

  - apiGroups:

      - ""

    resources:

      - nodes

    verbs:

      - list

      - watch

  - apiGroups:

      - ""

    resources:

      - nodes/status

    verbs:

      - patch

---

kind: ClusterRoleBinding  #定义了一个ClusterRoleBinding

apiVersion: rbac.authorization.k8s.io/v1beta1

metadata:

  name: flannel

roleRef:

  apiGroup: rbac.authorization.k8s.io

  kind: ClusterRole

  name: flannel

subjects:

- kind: ServiceAccount

  name: flannel

  namespace: kube-system

---

apiVersion: v1

kind: ServiceAccount   #定义了一个ServiceAccount

metadata:

  name: flannel

  namespace: kube-system

---

kind: ConfigMap

apiVersion: v1

metadata:

  name: kube-flannel-cfg

  namespace: kube-system

  labels:

    tier: node

    app: flannel

data:

  cni-conf.json: |

    {

      "name": "cbr0",

      "plugins": [

        {

          "type": "flannel",

          "delegate": {

            "hairpinMode": true,

            "isDefaultGateway": true

          }

        },

        {

          "type": "portmap",

          "capabilities": {

            "portMappings": true

          }

        }

      ]

    }

  net-conf.json: |

    {

      "Network": "10.244.0.0/16",

      "Backend": {

        "Type": "vxlan"

      }

    }

---

......(以下省略)　　

查看flannel创建的pod信息

[root@k8s-master01 kubernetes]# kubectl get pod -n kube-system

NAME                                   READY     STATUS    RESTARTS   AGE

etcd-k8s-master01                      /       Running             32d

kube-apiserver-k8s-master01            /       Running             32d

kube-controller-manager-k8s-master01   /       Running             7d

kube-dns-86f4d74b45-72kdh              /       Running             32d

kube-flannel-ds-amd64-847wt            /       Running             32d

kube-flannel-ds-amd64-9v9t6            /       Running             32d

kube-flannel-ds-amd64-k4blq            /       Running             32d

kube-proxy-8l9tf                       /       Running             32d

kube-proxy-m6pqm                       /       Running             32d

kube-proxy-scj8n                       /       Running             32d

kube-scheduler-k8s-master01            /       Running             32d

[root@k8s-master01 kubernetes]# kubectl get pod kube-flannel-ds-amd64-847wt -n kube-system  -o yaml

......(省略)

  serviceAccount: flannel

  serviceAccountName: flannel  #表示当前的pod在启动容器时，运行的进程与APIserver进行通讯的时候，会以serviceAccountName的账号与APIserver进行连接，从而获得该serviceaccount的权限

.....(省略)　

下面是一张我个人总结的关于user绑定到不同的Role和Binding时所拥有的权限边界

User

Binding 类型

Role 类型

权限

RoleBinding

Role

namespace

ClusterRoleBinding

ClusterRole

Cluster

RoleBinding

ClusterRole

namespace

参考文档：https://www.kubernetes.org.cn/4062.html　　

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