• openshift 使用curl命令访问apiserver


    openshift版本:openshift v3.6.173.0.5

    使用oc(同kubectl)命令访问apiserver资源的时候,会使用到/root/.kube/config文件中使用的配置。

    使用user访问apiserver

    oc命令使用config中定义的user和证书(公钥和私钥)访问apiserver。使用如下命令查看当前使用的config上下文:monitor为当前的namespace,test-openshfit-com:8443为apiserver暴露的server,system:admin为访问apiserver使用的user名称

    # oc config current-context
    monitor/test-openshfit-com:8443/system:admin

    查看system:admin对应的证书(下面使用变量代替)

    users:
    - name: system:admin/test-openshift-com:8443
      user:
        client-certificate-data: ${CA}
        client-key-data: ${KEY}

    导出证书,将下面decode出的内容分别保存到/home/ca.cert,/home/ca.key

    # echo -n ${CA}|base64 --decode   #/home/ca.cert
    # echo -n ${KEY}|base64 --decode  #/home/ca.key

    使用如下方式即可访问cluster范围内的资源,该方式与oc命令的原理一样。下面以访问servers为例

    APISERVER=$(kubectl config view --minify -o jsonpath='{.clusters[0].cluster.server}')
    curl $APISERVER/api/v1/services --cert /home/ca.cert --key /home/ca.key --user system:admin

     

    使用serviceaccount访问apiserver

    serviceaccount除了可以为pod提供secret外,还可以作为访问apiserver资源的凭证。使用如下命令创建一个名为curltest的serviceaccount,并获取其token

    oc create serviceaccount curltest
    APISERVER=$(kubectl config view --minify -o jsonpath='{.clusters[0].cluster.server}')
    TOKEN=$(oc serviceaccounts get-token curltest)

    使用如下命令进行rolebinding之后就可以查看namespaces为monitor下面的资源,但不可以查看其他namespace的资源。system:master可以看作一个超级账户,可参见user-facing-roles

    oc policy add-role-to-user system:master -z curltest
    curl $APISERVER/api/v1/namespaces/monitor/services --header "Authorization: Bearer $TOKEN"

    使用下面命令查看当前rolebinding情况,可以查看当前serveraccount可进行的操作权限。注:openshift的add-role-to-user/add-cluster-role-to-user其实就是kubernetes进行rolebinding/clusterrolebinding的操作,将一个role权限赋予一个user或serviceaccount。

    # oc describe rolebinding system:master
    Name:                   system:master
    Namespace:              monitor
    Created:                5 minutes ago
    Labels:                 <none>
    Annotations:            <none>
    Role:                   /system:master
    Users:                  <none>
    Groups:                 <none>
    ServiceAccounts:        curltest
    Subjects:               <none>
    Verbs                   Non-Resource URLs       Resource Names  API Groups      Resources
    [*]                     []                      []              [*]             [*]
    [*]                     [*]                     []              []              []

    使用如下命令进行clusterrolebinding之后就可以访问cluster范围内的资源,首先需要删除先前的rolebinding

    oc policy remove-role-from-user system:master -z curltest
    oadm policy add-cluster-role-to-user system:master -z curltest
    TOKEN=$(oc serviceaccounts get-token curltest)
    curl $APISERVER/api/v1/services --header "Authorization: Bearer $TOKEN"

    查看clusterrolebinding情况

    # oc describe clusterrolebinding system:master
    Name:                   system:masters
    Created:                2 weeks ago
    Labels:                 <none>
    Annotations:            <none>
    Role:                   /system:master
    Users:                  <none>
    Groups:                 system:masters
    ServiceAccounts:        monitor/curltest
    Subjects:               <none>
    Verbs                   Non-Resource URLs       Resource Names  API Groups      Resources
    [*]                     []                      []              [*]             [*]
    [*]                     [*]                     []              []              []

    环境清理

    oadm policy remove-cluster-role-from-user system:master -z liu
    oc delete sa curltest

    下面演示pod如何使用serviceaccount访问apiserver资源,参照在Kubernetes Pod中使用Service Account访问API Server

    首先安装minikube和go,方法可以参见https://www.cnblogs.com/charlieroro/p/10434138.html。minikube启动时直接使用docker驱动即可:minikube start --vm-driver=none

    对client-go的操作步骤用于生成测试镜像,可以直接下载已经打包好的镜像(docker pull docker push woodliu268/k8s-example)来跳过下面相关操作

    安装client-go,client使用了go module方式来管理包依赖(client-go根目录下使用go.mod和go.sum来管理包),参见Installing client-go

    export GO111MODULE=on
    go mod init
    go get k8s.io/client-go@master

    修改client-go/examples/in-cluster-client-configuration/main.go目录下,将panic全部修改为fmt.Println,执行如下命令编译为可执行程序main

    go build -o main main.go

    Dockerfile内容如下,编译为docker镜像

    FROM debian
    COPY main /root/main
    RUN chmod +x /root/main
    WORKDIR /root
    ENTRYPOINT ["/root/main"]
    docker build -t k8s/example1:latest .

    使用如下deployment创建pod,默认创建的default命名空间

    # cat deployment.yaml
    apiVersion: extensions/v1beta1
    kind: Deployment
    metadata:
      name: k8s-example
    spec:
      replicas: 1
      template:
        metadata:
          labels:
            run: k8s-example
        spec:
          containers:
          - name: k8s-example
            image: k8s/example1:latest
            imagePullPolicy: IfNotPresent

    kubectl log -f k8s-example-7747697dbf-772df时发现有如下错误。说明pod使用用户system:serviceaccount:default:default访问apiserver的时候访问失败

    pods is forbidden: User "system:serviceaccount:default:default" cannot list resource "pods" in API group "" at the cluster scope
    There are 0 pods in the cluster

    由于需要在cluster范围内访问pod资源,下面创建clusterrole和clusterrolebinding(参考Using RBAC Authorization),并赋予system:serviceaccount:default:default list pod的权限

    # cat clusterrole.yaml
    kind: ClusterRole
    apiVersion: rbac.authorization.k8s.io/v1
    metadata:
      namespace: default
      name: pod-reader
    rules:
    - apiGroups: [""]
      resources: ["pods"]
      verbs: ["get", "watch", "list"]
    # cat clusterrolebinding.yaml kind: ClusterRoleBinding apiVersion: rbac.authorization.k8s.io
    /v1 metadata: name: read-pods namespace: default subjects: - kind: User name: system:serviceaccount:default:default apiGroup: rbac.authorization.k8s.io roleRef: kind: ClusterRole name: pod-reader apiGroup: rbac.authorization.k8s.io

    重新创建deployment,查看pod日志,可以正常读取cluster的pod信息

    There are 10 pods in the cluster

    PS:

    • 使用kubectl get RESOURECE -v=NUM可以查看kubectl的与apiserver的交互,RESOURECE为pod,service等;NUM取值为6-8
    • 使用oc config use-context可以设置kubeconfig文件中的current-context字段
    • Service account 验证时用户名 system:serviceaccount:(NAMESPACE):(SERVICEACCOUNT),被指定到组 system:serviceaccounts 和 system:serviceaccounts:(NAMESPACE)
    • 应用程序可能会在如yaml模板中使用serviceaccount挂载到pod中的tls证书来访问apiserver资源

    参考:

    https://kubernetes.io/docs/reference/access-authn-authz/rbac/

    https://docs.openshift.com/container-platform/3.5/rest_api/index.html

    https://docs.openshift.com/container-platform/3.9/admin_guide/manage_rbac.html

    https://docs.openshift.com/enterprise/3.0/admin_guide/manage_authorization_policy.html

    https://jimmysong.io/posts/user-authentication-in-kubernetes/

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  • 原文地址:https://www.cnblogs.com/charlieroro/p/10815091.html
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