Kubernetes-dashboard的身份认证

上一篇文章中,我们成功配置安装了kubernetes-dashboard插件,但是这里似乎来了另外一个问题:我们怎样进入到dashboard?

login
如上图,kubernetes-dashboard提供了两种验证方式:kubeconfigtoken。这两种验证方式都是怎么回事呢?诶,好像有一个skip,我们点击看看。直接点击skip,我们进入到了dashboard的界面,但是似乎我们什么都做不了,页面给出了提醒,我们没有权限查看和操作集群里面的资源。该怎么办呢?下面就让我们一起来看看kubernetes里面的身份认证和权限管理吧!

要了解k8s中的身份认证和权限管理我们就必须先来了解k8s中的RBAC(Role-based access control)授权模式。

RBAC in K8s

RBAC Authorization的基本概念是RoleRoleBindingRole是一些permission的集合;而RoleBinding则是将Role授权给某些User、某些Group或某些ServiceAccount。K8s官方博客RBAC Support in Kubernetes一文的中的配图对此做了很生动的诠释:

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从上图中我们可以看到:
Role:pod-reader 拥有Pod的getlist permissions;
RoleBinding:pod-readerRole:pod-reader授权给右边的UserGroupServiceAccount

RoleRoleBinding对应的是,K8s还有ClusterRoleClusterRoleBinding的概念,它们不同之处在于:ClusterRoleClusterRoleBinding是针对整个Cluster范围内有效的,无论用户或资源所在的namespace是什么;而RoleRoleBinding的作用范围是局限在某个k8s namespace中的。

kubernetes在安装之初就已经生成了许多rolerolebindingclusterroleclusterrolebinding,它们也是属于kubernetes资源的一部分,所以可以通过getdescribe等命令查看,如下:

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[root@iZwz9f6pgul78p7die5tlzZ dashboard]# kc get role -n kube-system
NAME AGE
extension-apiserver-authentication-reader 5d
kubernetes-dashboard-minimal 2d
system::leader-locking-kube-controller-manager 5d
system::leader-locking-kube-scheduler 5d
system:controller:bootstrap-signer 5d
system:controller:cloud-provider 5d
system:controller:token-cleaner 5d
weave-net 5d
[root@iZwz9f6pgul78p7die5tlzZ dashboard]# kc describe role extension-apiserver-authentication-reader -n kube-system
Name: extension-apiserver-authentication-reader
Labels: kubernetes.io/bootstrapping=rbac-defaults
Annotations: rbac.authorization.kubernetes.io/autoupdate=true
PolicyRule:
Resources Non-Resource URLs Resource Names Verbs
--------- ----------------- -------------- -----
configmaps [] [extension-apiserver-authentication] [get]

下面截取了kubernetes-dashboard.yml文件的一部分:

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# ------------------- Dashboard Service Account ------------------- #

apiVersion: v1
kind: ServiceAccount
metadata:
labels:
k8s-app: kubernetes-dashboard
name: kubernetes-dashboard
namespace: kube-system

---
# ------------------- Dashboard Role & Role Binding ------------------- #

kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
name: kubernetes-dashboard-minimal
namespace: kube-system
rules:
# Allow Dashboard to create and watch for changes of 'kubernetes-dashboard-key-holder' secret.
- apiGroups: [""]
resources: ["secrets"]
verbs: ["create", "watch"]
- apiGroups: [""]
resources: ["secrets"]
# Allow Dashboard to get, update and delete 'kubernetes-dashboard-key-holder' secret.
resourceNames: ["kubernetes-dashboard-key-holder", "kubernetes-dashboard-certs"]
verbs: ["get", "update", "delete"]
# Allow Dashboard to get metrics from heapster.
- apiGroups: [""]
resources: ["services"]
resourceNames: ["heapster"]
verbs: ["proxy"]

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
name: kubernetes-dashboard-minimal
namespace: kube-system
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: kubernetes-dashboard-minimal
subjects:
- kind: ServiceAccount
name: kubernetes-dashboard
namespace: kube-system
---

上面这个yml文件做了这么一件事情:在kube-system命名空间中创建了一个名为kubernetes-dashboardServiceAccount。同时,在kube-system命名空间中创建了一个名为kubernetes-dashboard-minimalRole,并且定义了这个Role的权限.然后同样是在kube-system命名空间中创建了一个RoleBinding,将上面的RoleServiceAccount绑定在一起了。这样kubernetes-dashboard就有了kubernetes-dashboard-minimal所定义的权限了。有一点需要注意:这里的kubernetes-dashboard这个ServiceAccount是当用户直接点击skip进入到dashboard时所使用的账户。

测试环境中的认证

如果是在测试环境中,我们图个简单,不考虑安全性的情况之下。可以考虑让外部用户直接点击skip进入到dashboard,并且拥有所有的权限。这一点可以通过将cluster-admin这个拥有全集群最高权限的ClusterRole绑定到默认使用的ServiceAccount--kubernetes-dashboard,具体的做法是:
创建文件:dashboard-admin.yml,填写下列内容:

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apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: kubernetes-dashboard
labels:
k8s-app: kubernetes-dashboard
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: cluster-admin
subjects:
- kind: ServiceAccount
name: kubernetes-dashboard
namespace: kube-system

执行下面的命令来创建一个ClusterRoleBinding:

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$ kubectl create -f dashboard-admin.yml

这样,我们就可以直接点击skip进入dashboard,并且拥有全部的权限。

基于token的认证

下面我们来说说token这种方式。点击选择:Token单选框,提示你输入token。token从哪里获取,我们从来没有生成过token?其实当前K8s中已经有了很多token:

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[root@iZwz9f6pgul78p7die5tlzZ dashboard]# kc get secret -n kube-system
NAME TYPE DATA AGE
attachdetach-controller-token-vkm75 kubernetes.io/service-account-token 3 5d
bootstrap-signer-token-k59x3 kubernetes.io/service-account-token 3 5d
bootstrap-token-ff4535 bootstrap.kubernetes.io/token 5 5d
certificate-controller-token-z3qpm kubernetes.io/service-account-token 3 5d
daemon-set-controller-token-3lbtj kubernetes.io/service-account-token 3 5d
default-token-8372f kubernetes.io/service-account-token 3 5d
deployment-controller-token-pb2wl kubernetes.io/service-account-token 3 5d
disruption-controller-token-jwjlt kubernetes.io/service-account-token 3 5d
endpoint-controller-token-t3h87 kubernetes.io/service-account-token 3 5d
generic-garbage-collector-token-sm8lt kubernetes.io/service-account-token 3 5d
heapster-token-zqld8 kubernetes.io/service-account-token 3 6h
horizontal-pod-autoscaler-token-v6wjc kubernetes.io/service-account-token 3 5d
job-controller-token-hfl7h kubernetes.io/service-account-token 3 5d
kube-dns-token-rfkvx kubernetes.io/service-account-token 3 5d
kube-proxy-token-r017j kubernetes.io/service-account-token 3 5d
kubernetes-dashboard-certs Opaque 2 2d
kubernetes-dashboard-key-holder Opaque 2 4d
kubernetes-dashboard-token-jzx4v kubernetes.io/service-account-token 3 2d
namespace-controller-token-3j3sn kubernetes.io/service-account-token 3 5d
node-controller-token-cnjsn kubernetes.io/service-account-token 3 5d
persistent-volume-binder-token-p1cwr kubernetes.io/service-account-token 3 5d
pod-garbage-collector-token-rbw2m kubernetes.io/service-account-token 3 5d
replicaset-controller-token-pt682 kubernetes.io/service-account-token 3 5d
replication-controller-token-s2kb7 kubernetes.io/service-account-token 3 5d
resourcequota-controller-token-xlrrh kubernetes.io/service-account-token 3 5d
service-account-controller-token-zlcph kubernetes.io/service-account-token 3 5d
service-controller-token-0cqs6 kubernetes.io/service-account-token 3 5d
statefulset-controller-token-0p29q kubernetes.io/service-account-token 3 5d
token-cleaner-token-cq9nk kubernetes.io/service-account-token 3 5d
ttl-controller-token-gndzv kubernetes.io/service-account-token 3 5d
weave-net-token-w6grc kubernetes.io/service-account-token 3 5d
[root@iZwz9f6pgul78p7die5tlzZ dashboard]# kc describe secret attachdetach-controller-token-vkm75 -n kube-system
Name: attachdetach-controller-token-vkm75
Namespace: kube-system
Labels: <none>
Annotations: kubernetes.io/service-account.name=attachdetach-controller
kubernetes.io/service-account.uid=691cdfc2-4612-11e8-8dc4-00163e0a39da

Type: kubernetes.io/service-account-token

Data
====
ca.crt: 1025 bytes
namespace: 11 bytes
token: eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.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.ZBoh8-i6882nHH_oaEhtUw7L-M-2kGgrV3dRqAFw1bQUbenOYCK_xqQFeW0gTpEmYa_-k2cukfHKgqtyCF2U_hr1mXikc4aAZzJubnszQhNnASzHFihi5AkZfxBBiqYjd8WUaUSms1VbvImvmSg_Ndrw3-SSB0B0b-sWEH4dAwcXx1_hN2V3GBXZjjdFHT51U6ogvwzs-YJ_Uk5GqWIPxPNHhGMFQtQL3vVIHpxumtG6xdoVRuDitMl0gH71gugSgjabNLPMjIHmApbI3BIeH9bX9jO271OdTzNGvKaBOx2xLRJBTvrk4bSyZsSdqrLkWlUVgCTw7VNLKpmgfNTMDQ

如上,这里有很多的secret存在于系统之中,每个secret都对应了一个token,但是这些token所对应的权限都不相同,所以不一定会符合我们的要求。

这里我们需要创建一个名为admin的ServiceAccount并绑定名为cluster-admin的ClusterRole角色(该角色拥有集群最高权限),使用下面的yaml文件创建admin用户并赋予他管理员权限,然后可以通过token登陆dashbaord。这种认证方式本质上是通过ServiceAccount的身份认证加上Bearer token请求API server的方式实现。
admin-token.yml

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kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
name: admin
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
roleRef:
kind: ClusterRole
name: cluster-admin
apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
name: admin
namespace: kube-system
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: admin
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
addonmanager.kubernetes.io/mode: Reconcile

运行下面的命令:

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$ kubectl create -f admin-token.yml

然后我们可以通过如下的命令来获取admin ServiceAccount的token:

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[root@iZwz9f6pgul78p7die5tlzZ ~]# kc get secret -n kube-system | grep admin
admin-token-whj4t kubernetes.io/service-account-token 3 1d
[root@iZwz9f6pgul78p7die5tlzZ ~]# kc describe secret/admin-token-whj4t -n kube-system
Name: admin-token-whj4t
Namespace: kube-system
Labels: <none>
Annotations: kubernetes.io/service-account.name=admin
kubernetes.io/service-account.uid=f2e69a6e-4a03-11e8-8dc4-00163e0a39da

Type: kubernetes.io/service-account-token

Data
====
ca.crt: 1025 bytes
namespace: 11 bytes
token: eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJhZG1pbi10b2tlbi13aGo0dCIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50Lm5hbWUiOiJhZG1pbiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50LnVpZCI6ImYyZTY5YTZlLTRhMDMtMTFlOC04ZGM0LTAwMTYzZTBhMzlkYSIsInN1YiI6InN5c3RlbTpzZXJ2aWNlYWNjb3VudDprdWJlLXN5c3RlbTphZG1pbiJ9.Nq6N7E7xY09sITcqa0WP3OeNo6Sp_se69q9aH3oM-gWDx7Sp_sbRn1VIBE-op9yG4XRbkoam-KVYhyX7QVATesYCF1fZ0p0ENcctAhmO9aEoQ1GS5I6W3DWrUXgWgaZJSrNHt-czHC_WUB3ilggaDcOEAqPEb3gYqrezyEarclQPNQZfHo3UNWjhjCqmm2vOEweCbyn9o0t8QHTTT_Pp26Bq1ho2B4HqGEeM8RHa175mG18eJQ5aRYuMM70Yp0uNyyMQmXnPTNzX0uHvU9uq-dSxxDRlq5bRg_l5bravtCsr51I-VMU9FyWd3OJWK0z1hrO76X1JrWfsbmzY3rVCSg

如上,我们得到了该用户的token,注意:这里的token是进行base64编码后的结果,而我们需要的是解码之后的结果,直接获取解码之后的token可以通过下面的命令实现:

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$ kubectl -n kube-system get secret admin-token-whj4t -o jsonpath={.data.token}|base64 -d

这样,我们将解码之后的token复制出来,填入dashboard认证表单中就可以进入dashboard并且获取全集群的最高权限。

基于kubeconfig的认证

如何生成kubeconfig文件请参考创建用户认证授权的kubeconfig文件

注意参考文章中生成的kubeconfig文件中没有token字段,如果我们要使用kubeconfig登录dashboard则需要手动添加该字段。

对于访问dashboard时候使用的kubeconfig文件如brand.kubeconfig必须追到token字段,否则认证不会通过。而使用kubectl命令时的用的kubeconfig文件则不需要包含token字段。

kubeconfig的认证可以让拥有该kubeconfig的用户只拥有一个或几个命名空间的操作权限,这相比与上面的token的方式更加的精确和安全。kubeconfig也可以针对kubectl:

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$ cp -f brand.kubeconfig ~/.kube/config

这样,该用户就只具有brand.kubeconfig文件所确定的命名空间的操作权限了。

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