K8S进阶实践 之 鉴权控制（ServiceAccount&RBAC）

一、RBAC的四种资源

1、Role

一个Role只能授权访问单个namespace

## 示例定义一个名为pod-reader的角色，该角色具有读取default这个命名空间下的pods的权限
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
namespace: default
name: pod-reader
rules:
- apiGroups: [""] # "" 代表所有
resources: ["pods"]
verbs: ["get", "watch", "list"]

## apiGroups: "","apps", "autoscaling", "batch", kubectl api-versions
## resources: "services", "pods","deployments"... kubectl api-resources
## verbs: "get", "list", "watch", "create", "update", "patch", "delete", "exec"

2、ClusterRole

一个ClusterRole能够授予和Role一样的权限，但是它是集群范围内的。

## 定义一个集群角色，名为secret-reader，该角色可以读取所有的namespace中的secret资源
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
# "namespace" omitted since ClusterRoles are not namespaced
name: secret-reader
rules:
- apiGroups: [""]
resources: ["secrets"]
verbs: ["get", "watch", "list"]

3、Rolebinding

将role中定义的权限分配给用户和用户组。RoleBinding包含主题（users,groups,或service accounts）和授予角色的引用。对于namespace内的授权使用RoleBinding，集群范围内使用ClusterRoleBinding。

## 定义一个角色绑定，将pod-reader这个role的权限授予给jane这个User，使得jane可以在读取default这个命名空间下的所有的pod数据
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: read-pods
namespace: default
subjects:
- kind: User   #这里可以是User,Group,ServiceAccount
name: jane 
apiGroup: rbac.authorization.k8s.io
roleRef:
kind: Role #这里可以是Role或者ClusterRole,若是ClusterRole，则权限也仅限于rolebinding的内部
name: pod-reader # match the name of the Role or ClusterRole you wish to bind to
apiGroup: rbac.authorization.k8s.io

注意：rolebinding既可以绑定role，也可以绑定clusterrole，当绑定clusterrole的时候，subject的权限也会被限定于rolebinding定义的namespace内部，若想跨namespace，需要使用clusterrolebinding

## 定义一个角色绑定，将dave这个用户和secret-reader这个集群角色绑定，虽然secret-reader是集群角色，但是因为是使用rolebinding绑定的，因此dave的权限也会被限制在development这个命名空间内
apiVersion: rbac.authorization.k8s.io/v1
# This role binding allows "dave" to read secrets in the "development" namespace.
# You need to already have a ClusterRole named "secret-reader".
kind: RoleBinding
metadata:
name: read-secrets
#
# The namespace of the RoleBinding determines where the permissions are granted.
# This only grants permissions within the "development" namespace.
namespace: development
subjects:
- kind: User
name: dave # Name is case sensitive
apiGroup: rbac.authorization.k8s.io
- kind: ServiceAccount
name: dave # Name is case sensitive
namespace: luffy
roleRef:
kind: ClusterRole
name: secret-reader
apiGroup: rbac.authorization.k8s.io

考虑一个场景： 如果集群中有多个namespace分配给不同的管理员，每个namespace的权限是一样的，就可以只定义一个clusterrole，然后通过rolebinding将不同的namespace绑定到管理员身上，否则就需要每个namespace定义一个Role，然后做一次rolebinding。

4、ClusterRolebingding

允许跨namespace进行授权

apiVersion: rbac.authorization.k8s.io/v1
# This cluster role binding allows anyone in the "manager" group to read secrets in any namespace.
kind: ClusterRoleBinding
metadata:
name: read-secrets-global
subjects:
- kind: Group
name: manager # Name is case sensitive
apiGroup: rbac.authorization.k8s.io
roleRef:
kind: ClusterRole
name: secret-reader
apiGroup: rbac.authorization.k8s.io

二 、确认当前K8S集群的授权策略

前面介绍过，认证可以通过证书（kubectl），也可以通过使用ServiceAccount（服务账户）的方式来做认证。大多数时候，我们在基于k8s做二次开发时都是选择通过ServiceAccount + RBAC 的方式

三、鉴权控制实例需求描述

例子：a,b,c,d四个用户，分别权限如下：
a：授权访问查看kang空间的pods资源
b：授权查看、删除、更新kang空间的的pods资源
c：授权查看所有空间下的pods资源
d：授权查看、删除、更新所有空间下的pods资源

四、a用户授权演示

1、yaml文件

kind: Role         #创建一个role角色
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: kang
  name: reader
rules:
- apiGroups: [""] # "" 代表所有
  resources: ["pods"]  # 授权的资源
  verbs: ["get", "watch", "list"]   #可操作方法

---
apiVersion: v1 
kind: ServiceAccount        #创建一个ServiceAccount
metadata:
  name: a                   #a的ServiceAccount
  namespace: kang

---
kind: RoleBinding           #将role与ServiceAccount绑定
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: test
  namespace: kang           #RoleBinding需指定namespace空间
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
roleRef:
  kind: Role
  name: reader
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: a
  namespace: kang

2、根据yaml文件创建相关资源

3、查看a用户token信息

4、Dashboard验证权限

尝试删除其中一个pod，验证是否只有查看

五、b\c\d用户的对应yaml文件

b用户

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: kang
  name: writer
rules:
- apiGroups: [""] # "" indicates the core API group
  resources: ["pods"]
  verbs: ["get", "watch", "list","update", "patch", "delete"]

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: b
  namespace: kang

---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: writer
  namespace: kang
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
roleRef:
  kind: Role
  name: writer
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: b
  namespace: kang

c用户yaml文件

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: reader-allpod
rules:
- apiGroups: [""] # "" indicates the core API group
  resources: ["pods","namespaces"]
  verbs: ["get", "watch", "list"]

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: c
  namespace: kang

---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: reader-allpod
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
roleRef:
  kind: ClusterRole
  name: reader-allpod
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: c
  namespace: kang

d用户yaml文件

kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: writer-allpod
rules:
- apiGroups: [""] # "" indicates the core API group
  resources: ["pods","namespaces"]
  verbs: ["get", "watch", "list","update", "patch", "delete"]

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: d
  namespace: kang

---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: writer-allpod
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
roleRef:
  kind: ClusterRole
  name: writer-allpod
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: d
  namespace: kang

六、API请求方法（curl方法）