kubernetes RBAC实战

环境准备

先用kubeadm安装好kubernetes集群，[包地址在此](https://market.aliyun.com/products/56014009/cmxz022571.html#sku=yuncode1657100000) 好用又方便，服务周到，童叟无欺

本文目的，让名为devuser的用户只能有权限访问特定namespace下的pod

命令行kubectl访问

安装cfssl

 此工具生成证书非常方便, pem证书与crt证书,编码一致可直接使用

 wget https://pkg.cfssl.org/R1.2/cfssl_linux-amd64
 chmod +x cfssl_linux-amd64
 mv cfssl_linux-amd64 /bin/cfssl

wget https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64
 chmod +x cfssljson_linux-amd64
 mv cfssljson_linux-amd64 /bin/cfssljson

wget https://pkg.cfssl.org/R1.2/cfssl-certinfo_linux-amd64
 chmod +x cfssl-certinfo_linux-amd64
 mv cfssl-certinfo_linux-amd64 /bin/cfssl-certinfo

签发客户端证书

根据ca证书与么钥签发用户证书

根证书已经在/etc/kubernetes/pki目录下了

[root@master1 ~]# ls /etc/kubernetes/pki/
 apiserver.crt ca-config.json devuser-csr.json front-proxy-ca.key sa.pub
 apiserver.key ca.crt devuser-key.pem front-proxy-client.crt
 apiserver-kubelet-client.crt ca.key devuser.pem front-proxy-client.key
 apiserver-kubelet-client.key devuser.csr front-proxy-ca.crt sa.key

注意以下几个文件： `ca.crt ca.key ca-config.json devuser-csr.json`

创建ca-config.json文件

cat > ca-config.json < devuser-csr.json < 校验证书
cfssl-certinfo -cert kubernetes.pem

生成config文件

kubeadm已经生成了admin.conf，我们可以直接利用这个文件，省的自己再去配置集群参数

$ cp /etc/kubernetes/admin.conf devuser.kubeconfig

设置客户端认证参数:

kubectl config set-credentials devuser \
 --client-certificate=/etc/kubernetes/ssl/devuser.pem \
 --client-key=/etc/kubernetes/ssl/devuser-key.pem \
 --embed-certs=true \
 --kubeconfig=devuser.kubeconfig

设置上下文参数：

kubectl config set-context kubernetes \
 --cluster=kubernetes \
 --user=devuser \
 --namespace=kube-system \
 --kubeconfig=devuser.kubeconfig

设置莫认上下文：

kubectl config use-context kubernetes --kubeconfig=devuser.kubeconfig

以上执行一个步骤就可以看一下 devuser.kubeconfig的变化。里面最主要的三个东西

• cluster: 集群信息，包含集群地址与公钥
• user: 用户信息，客户端证书与私钥，正真的信息是从证书里读取出来的，人能看到的只是给人看的。
• context: 维护一个三元组，namespace cluster 与 user

创建角色

创建一个叫pod-reader的角色

[root@master1 ~]# cat pod-reader.yaml
 kind: Role
 apiVersion: rbac.authorization.k8s.io/v1
 metadata:
 namespace: kube-system
 name: pod-reader
 rules:
 - apiGroups: [""] # "" indicates the core API group
 resources: ["pods"]
 verbs: ["get", "watch", "list"]

kubectl create -f pod-reader.yaml

绑定用户

创建一个角色绑定，把pod-reader角色绑定到 devuser上

[root@master1 ~]# cat devuser-role-bind.yaml
 kind: RoleBinding
 apiVersion: rbac.authorization.k8s.io/v1
 metadata:
 name: read-pods
 namespace: kube-system
 subjects:
 - kind: User
 name: devuser # 目标用户
 apiGroup: rbac.authorization.k8s.io
 roleRef:
 kind: Role
 name: pod-reader # 角色信息
 apiGroup: rbac.authorization.k8s.io

kubectl create -f devuser-role-bind.yaml

使用新的config文件

$ rm .kube/config && cp devuser.kubeconfig .kube/config

效果, 已经没有别的namespace的权限了，也不能访问node信息了：

[root@master1 ~]# kubectl get node
 Error from server (Forbidden): nodes is forbidden: User "devuser" cannot list nodes at the cluster scope

[root@master1 ~]# kubectl get pod -n kube-system
 NAME READY STATUS RESTARTS AGE
 calico-kube-controllers-55449f8d88-74x8f 1/1 Running 0 8d
 calico-node-clpqr 2/2 Running 0 8d
 kube-apiserver-master1 1/1 Running 2 8d
 kube-controller-manager-master1 1/1 Running 1 8d
 kube-dns-545bc4bfd4-p6trj 3/3 Running 0 8d
 kube-proxy-tln54 1/1 Running 0 8d
 kube-scheduler-master1 1/1 Running 1 8d

[root@master1 ~]# kubectl get pod -n default
 Error from server (Forbidden): pods is forbidden: User "devuser" cannot list pods in the namespace "default": role.rbac.authorization.k8s.io "pod-reader" not found

dashboard访问

service account原理

k8s里面有两种用户，一种是User，一种就是service account，User给人用的，service account给进程用的，让进程有相关的权限。

如dasboard就是一个进程，我们就可以创建一个service account给它，让它去访问k8s。

我们看一下是如何把admin权限赋给dashboard的：

╰─➤ cat dashboard-admin.yaml
 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

把 kubernetes-dashboard 这个ServiceAccount绑定到cluster-admin这个ClusterRole上，这个cluster role非常牛逼，啥权限都有

[root@master1 ~]# kubectl describe clusterrole cluster-admin -n kube-system
 Name: cluster-admin
 Labels: kubernetes.io/bootstrapping=rbac-defaults
 Annotations: rbac.authorization.kubernetes.io/autoupdate=true
 PolicyRule:
 Resources Non-Resource URLs Resource Names Verbs
 --------- ----------------- -------------- -----
 [*] [] [*]
 *.* [] [] [*]

而创建dashboard时创建了这个service account:

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

然后deployment里指定service account

volumes:
 - name: kubernetes-dashboard-certs
 secret:
 secretName: kubernetes-dashboard-certs
 - name: tmp-volume
 emptyDir: {}
 serviceAccountName: kubernetes-dashboard

更安全的做法

[root@master1 ~]# cat admin-token.yaml
 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

[root@master1 ~]# kubectl get secret -n kube-system|grep admin
 admin-token-7rdhf kubernetes.io/service-account-token 3 14m

[root@master1 ~]# kubectl describe secret admin-token-7rdhf -n kube-system
 Name: admin-token-7rdhf
 Namespace: kube-system
 Labels:
 Annotations: kubernetes.io/service-account.name=admin
 kubernetes.io/service-account.uid=affe82d4-d10b-11e7-ad03-00163e01d684

Type: kubernetes.io/service-account-token

Data
 ====
 ca.crt: 1025 bytes
 namespace: 11 bytes
 token: eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJhZG1pbi10b2tlbi03cmRoZiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50Lm5hbWUiOiJhZG1pbiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50LnVpZCI6ImFmZmU4MmQ0LWQxMGItMTFlNy1hZDAzLTAwMTYzZTAxZDY4NCIsInN1YiI6InN5c3RlbTpzZXJ2aWNlYWNjb3VudDprdWJlLXN5c3RlbTphZG1pbiJ9.jSfQhFsY7V0ZmfqxM8lM_UUOoUhI86axDSeyVVtldSUY-BeP2Nw4q-ooKGJTBBsrOWvMiQePcQxJTKR1K4EIfnA2FOnVm4IjMa40pr7-oRVY37YnR_1LMalG9vrWmqFiqIsKe9hjkoFDuCaP7UIuv16RsV7hRlL4IToqmJMyJ1xj2qb1oW4P1pdaRr4Pw02XBz9yBpD1fs-lbwheu1UKcEnbHS_0S3zlmAgCrpwDFl2UYOmgUKQVpJhX4wBRRQbwo1Sn4rEFVI1NIa9l_lM7Mf6YEquLHRu3BCZTdu9YfY9pevQz4OfHE0NOvDIqmGRL8Z9kPADAXbljWzcD1m1xCQ

用此token在界面上登录即可

kubernetes RBAC实战 kubernetes 用户角色访问控制，dashboard访问，kubectl配置生成