kubernetes RBAC实战 kubernetes 用户角色访问控制，dashboard访问，

摘要：这个用户或者组用于后面的角色绑定使用生成的证书就会生成下面的文件校验证书生成文件已经生成了，我们可以直接利用这个文件，省的自己再去配置集群参数设置客户端认证参数设置上下文参数设置莫认上下文以上执行一个步骤就可以看一下的变化。

先用kubeadm安装好kubernetes集群，kubernetes1.8.2安装包 | kubernetes1.9.2安装包好用又方便，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

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

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 <
创建devuser-csr.json文件：
k8s的用户名就是从CN上获取的。 组是从O上获取的。这个用户或者组用于后面的角色绑定使用
cat > devuser-csr.json <
生成user的证书：
$ cfssl gencert -ca=ca.crt -ca-key=ca.key -config=ca-config.json -profile=kubernetes devuser-csr.json | cfssljson -bare devuser
就会生成下面的文件：
devuser.csr  devuser-key.pem  devuser.pem
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