为K8S集群建立只读权限帐号
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kubernetes RBAC实战
环境准备
先用kubeadm安装好kubernetes集群，包地址在此 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
[[email protected] ~]# 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 <<EOF
{
"signing": {
"default": {
"expiry": "87600h"
},
"profiles": {
"kubernetes": {
"usages": [
"signing",
"key encipherment",
"server auth",
"client auth"
],
"expiry": "87600h"
}
}
}
}
EOF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 <<EOF
{
"CN": "devuser",
"hosts": [],
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "CN",
"ST": "BeiJing",
"L": "BeiJing",
"O": "k8s",
"OU": "System"
}
]
}
EOF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
[[email protected] ~]# 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
[[email protected] ~]# 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.iokubectl 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：
[[email protected] ~]# kubectl get node
Error from server (Forbidden): nodes is forbidden: User "devuser" cannot list nodes at the cluster scope
[[email protected] ~]# 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
[[email protected] ~]# 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 founddashboard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
[[email protected] ~]# 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
[[email protected] ~]# 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[[email protected] ~]# kubectl get secret -n kube-system|grep admin
admin-token-7rdhf kubernetes.io/service-account-token 3 14m[[email protected] ~]# kubectl describe secret admin-token-7rdhf -n kube-system
Name: admin-token-7rdhf
Namespace: kube-system
Labels: <none>
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
原文：https://studygolang.com/articles/11730?fr=sidebar
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