# CKA每日一题 --- Day 10

考题

创建一个Role(只有cka namespace下pods的所有操作权限)和RoleBinding(使用serviceaccount认证鉴权),使用对应serviceaccount作为认证信息对cka namespace下的pod进行操作以及对default namespace下的pods进行操作。 – Role和RoleBinding的名称的名称为cka-1202-role、cka-1202-rb

注意：请附所用命令、创建的Role、RoleBinding以及serviceaccount的完整yaml，可分多次评论。

# 答案

创建Service Account：

[root@liabio cka]# kubectl create serviceaccount cka-1202-sa -n cka  -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  creationTimestamp: "2019-12-02T23:37:42Z"
  name: cka-1202-sa
  namespace: cka
  resourceVersion: "15159020"
  selfLink: /api/v1/namespaces/cka/serviceaccounts/cka-1202-sa
  uid: 6764e90c-cb28-4de1-9109-6e3d56941fcb

1
2
3
4
5
6
7
8
9
10

创建Role：

[root@liabio cka]# kubectl create role  cka-1202-role -n cka  --verb=* --resource=pods -oyaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  creationTimestamp: "2019-12-02T23:40:26Z"
  name: cka-1202-role
  namespace: cka
  resourceVersion: "15159247"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/cka/roles/cka-1202-role
  uid: fc2c5593-2fd9-46d7-a809-99bcee32249e
rules:
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - '*'

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

创建RoleBinding：

[root@liabio cka]# kubectl create rolebinding cka-1202-rb -n cka  --role=cka-1202-role --serviceaccount=cka:cka-1202-sa  -oyaml 
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  creationTimestamp: "2019-12-02T23:46:50Z"
  name: cka-1202-rb
  namespace: cka
  resourceVersion: "15159794"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/cka/rolebindings/cka-1202-rb
  uid: c00d104e-a531-4781-90f4-2821651492bf
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: cka-1202-role
subjects:
- kind: ServiceAccount
  name: cka-1202-sa
  namespace: cka

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

验证：

获取到cka-1202-sa这个Service Account绑定的secret并base64 -d解码token字段：

[root@liabio ~]# kubectl get secret -n cka   
NAME                      TYPE                                  DATA   AGE
cka-1202-sa-token-9rgp4   kubernetes.io/service-account-token   3      42m
default-token-r77xn       kubernetes.io/service-account-token   3      4d14h
[root@liabio ~]# kubectl get secret -n cka  cka-1202-sa-token-9rgp4 -ojson | jq .data.token 
"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"
[root@liabio ~]# echo 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 | base64 -d
eyJhbGciOiJSUzI1NiIsImtpZCI6IiJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJja2EiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlY3JldC5uYW1lIjoiY2thLTEyMDItc2EtdG9rZW4tOXJncDQiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlcnZpY2UtYWNjb3VudC5uYW1lIjoiY2thLTEyMDItc2EiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlcnZpY2UtYWNjb3VudC51aWQiOiI2NzY0ZTkwYy1jYjI4LTRkZTEtOTEwOS02ZTNkNTY5NDFmY2IiLCJzdWIiOiJzeXN0ZW06c2VydmljZWFjY291bnQ6Y2thOmNrYS0xMjAyLXNhIn0.qWjrTq7DmVSSMS3Hxc4tlWx87T4koRCoVi125sesVEbvAKDi2z0Xo62Z703khmCWlY55NLOaeJKkZYxX9fLLGX2zOUeEw1omJfFFiNn54lc9HQN9Q_5fN4ra-V4VRiNnBATyn7c76hi66K5iHyZ0xlTMrpMA8W7YvNbgSZH9xghWRzzdHIJaauQpScLmJNL6lF4gydoWwGCC-PSEctjJNDm0_3I6hRHDfBswy6wKxTlxOyHtOryG4rE3g5jQfNu_A57S5Yhra0YS4zc4_DoupfP-sV57GAPKRq86lDge8z8qaHh4roI7E3Il-CEOGKRIxNvIfU_wthtk0oyinGGl2w[root@liabio ~]#

1
2
3
4
5
6
7
8

把解码后的信息添加到将添加到~/.kube/config中，注意到下面加了name为coderaction的context和name为coderaction的user

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: LS0tLS1CRUdJTiBDLQo=
    server: https://10.0.0.0:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: coderaction
  name: coderaction
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: coderaction
  user:
    token: eyJhbGciOiJSUzI1NiIsImtpZCI6IiJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJja2EiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlY3JldC5uYW1lIjoiY2thLTEyMDItc2EtdG9rZW4tOXJncDQiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlcnZpY2UtYWNjb3VudC5uYW1lIjoiY2thLTEyMDItc2EiLCJrdWJlcm5ldGVzLmlvL3NlcnZpY2VhY2NvdW50L3NlcnZpY2UtYWNjb3VudC51aWQiOiI2NzY0ZTkwYy1jYjI4LTRkZTEtOTEwOS02ZTNkNTY5NDFmY2IiLCJzdWIiOiJzeXN0ZW06c2VydmljZWFjY291bnQ6Y2thOmNrYS0xMjAyLXNhIn0.qWjrTq7DmVSSMS3Hxc4tlWx87T4koRCoVi125sesVEbvAKDi2z0Xo62Z703khmCWlY55NLOaeJKkZYxX9fLLGX2zOUeEw1omJfFFiNn54lc9HQN9Q_5fN4ra-V4VRiNnBATyn7c76hi66K5iHyZ0xlTMrpMA8W7YvNbgSZH9xghWRzzdHIJaauQpScLmJNL6lF4gydoWwGCC-PSEctjJNDm0_3I6hRHDfBswy6wKxTlxOyHtOryG4rE3g5jQfNu_A57S5Yhra0YS4zc4_DoupfP-sV57GAPKRq86lDge8z8qaHh4roI7E3Il-CEOGKRIxNvIfU_wthtk0oyinGGl2w
- name: kubernetes-admin
  user:
    client-certificate-data: LS0tLS1CRUdJTiB1M1Y2NDTnpPUT0KLS0tLS1FTkQgQ0VSVElGSUNBVEUtLS0tLQo=
    client-key-data: LS0tLS1CBS0NBUUVBdjNpTkx5eUEwaVdmOU1hUjA3cVFTOEtFWS0tLS0tCg==

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

通过切换到coderaction这个use-context可以发现，get默认分区下的Pod时提示system:serviceaccount:cka:cka-1202-sa没有权限，但可以正常获取cka namespace下的Pods

[root@liabio cka]# kubectl config use-context kubernetes-admin@kubernetes
Switched to context "kubernetes-admin@kubernetes".
[root@liabio cka]# kubectl get pod
NAME                               READY   STATUS    RESTARTS   AGE
cka-1128-01-7b8b8cb79-mll6d        1/1     Running   118        32h
[root@liabio cka]# 
[root@liabio cka]# 
[root@liabio cka]# kubectl get node
NAME     STATUS   ROLES    AGE    VERSION
liabio   Ready    master   141d   v1.15.2
[root@liabio cka]# kubectl config use-context coderaction
Switched to context "coderaction".
[root@liabio cka]# kubectl get pod
Error from server (Forbidden): pods is forbidden: User "system:serviceaccount:cka:cka-1202-sa" cannot list resource "pods" in API group "" in the namespace "default"
[root@liabio cka]# kubectl get pod -n cka
No resources found.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

# 解析

k8s对于访问 API 来说提供了两个步骤的安全措施：认证和授权。认证解决用户是谁的问题，授权解决用户能做什么的问题。通过合理的权限管理，能够保证系统的安全可靠。

k8s集群的所有操作基本上都是通过kube-apiserver这个组件进行的，它提供HTTP RESTful形式的API供集群内外客户端调用。需要注意的是：认证授权过程只存在HTTPS形式的API中。也就是说，如果客户端使用HTTP连接到kube-apiserver，那么是不会进行认证授权的。所以说，可以这么设置，在集群内部组件间通信使用HTTP，集群外部就使用HTTPS，这样既增加了安全性，也不至于太复杂。

本题主要是考察授权：基于角色的访问控制（RBAC）的考题。

RBAC官方文档： https://kubernetes.io/docs/reference/access-authn-authz/rbac/

创建RoleBinding 、Role、Service Account命令指导： https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#-em-rolebinding-em-

使用 kubeconfig 文件组织集群访问： https://kubernetes.io/docs/concepts/configuration/organize-cluster-access-kubeconfig/

context相关操作官方命令指南： https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#config

基于角色的访问控制（RBAC）是一种基于企业内各个用户的角色来调节对计算机或网络资源的访问的方法。

RBAC使用rbac.authorization.k8s.io API组驱动授权决策，使管理员可以通过Kubernetes API动态配置策略。

从1.8开始，RBAC模式是稳定的，并由rbac.authorization.k8s.io/v1 API提供支持。

要启用RBAC，请通过启动apiserver --authorization-mode=RBAC

RBAC API声明了四个顶级类型：

# Role和ClusterRole

在RBAC API中，Role包含代表一组权限的规则。权限纯粹是累加的（没有“拒绝”规则）。可以在namespace中用Role或在集群范围内用ClusterRole。

Role只能用于授予对单个名称空间内资源的访问权限。

ClusterRole由于它们是集群范围的，因此它们还可以用于授予以下权限：

集群范围内的资源（如节点）
非资源端点（例如“ /healthz”）
所有namespace中的命名空间资源（例如pod）

# RoleBinding和ClusterRoleBinding

RoleBinding向一个或一组用户授予在Role中定义的权限。它包含subjects（User，Group或Service Account），以及对所授予角色的引用。可以在namespace中使用RoleBinding或在集群范围内使用ClusterRoleBinding。

RoleBinding可以引用同一namespace下的Role。

roleRef是实际创建绑定的方式。该kind可以是Role或ClusterRole，并且name将引用具体名字的Role或ClusterRole

ClusterRoleBinding可以在集群级别和所有namespace中授予权限。

# 创建Role命令：

kubectl create role NAME --verb=verb --resource=resource.group/subresource [--resource-name=resourcename] [--dry-run]

--verb指定，对资源的操作动作集合，包括get、delete、update、create、patch、watch、list，所有操作动作为* --resource指定可操作资源类型集合； --resource-name指定可操作资源名称集合；如：

[root@liabio ~]# kubectl create role pod-reader-cka -n cka  --verb=get --verb=list --resource=pods --resource-name=readablepod --resource-name=anotherpod -oyaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  creationTimestamp: "2019-12-03T03:50:34Z"
  name: pod-reader-cka
  namespace: cka
  resourceVersion: "15179947"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/cka/roles/pod-reader-cka
  uid: 16742721-4890-43de-9725-d6c721c6e4cf
rules:
- apiGroups:
  - ""
  resourceNames:
  - readablepod
  - anotherpod
  resources:
  - pods
  verbs:
  - get
  - list

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

# 创建RoleBinding

kubectl create rolebinding NAME --clusterrole=NAME|--role=NAME [--user=username] [--group=groupname] [--serviceaccount=namespace:serviceaccountname] [--dry-run]

--role指定RoleBinding的roleRef中的Role名称； --clusterrole指定RoleBinding的roleRef中的ClusterRole名称； --serviceaccount指定RoleBinding的subjects集合； --user指定RoleBinding的subjects下User的名称；如：

[root@liabio ~]# kubectl create rolebinding admin-cka -n cka --clusterrole=admin --user=user1 --user=user2 --group=group1 -oyaml
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  creationTimestamp: "2019-12-03T03:47:55Z"
  name: admin-cka
  namespace: cka
  resourceVersion: "15179732"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/cka/rolebindings/admin-cka
  uid: 4d4eacfb-3ba0-4fa1-96c3-c624fbafb12c
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: admin
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: User
  name: user1
- apiGroup: rbac.authorization.k8s.io
  kind: User
  name: user2
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: group1

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

# 创建ServiceAccount

kubectl create serviceaccount NAME [--dry-run]

如：

[root@liabio cka]# kubectl create serviceaccount cka-1202-sa -n cka  -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  creationTimestamp: "2019-12-02T23:37:42Z"
  name: cka-1202-sa
  namespace: cka
  resourceVersion: "15159020"
  selfLink: /api/v1/namespaces/cka/serviceaccounts/cka-1202-sa
  uid: 6764e90c-cb28-4de1-9109-6e3d56941fcb