kubernetes中的AOP - 准入控制

2019-11-21  本文已影响0人  doublegao

1.Admission Controllers

在整体的流程中可以理解为过滤器，拦截器甚至是AOP中的切面。准入控制是通过一个个插件实现，每个插件实现特定功能。例如ServiceAccount插件就是为了完成验证工作,MutatingAdmissionWebhook 和ValidatingAdmissionWebhook是为了实现动态注入控制。

2.kubernetes本身有哪些webhook

image.png

其中
NamespaceLifecycle, LimitRanger, ServiceAccount, TaintNodesByCondition, Priority, DefaultTolerationSeconds, DefaultStorageClass, StorageObjectInUseProtection, PersistentVolumeClaimResize, MutatingAdmissionWebhook, ValidatingAdmissionWebhook, ResourceQuota是默认开启的

3.动态准入控制 Dynamic Admission Control

上面所说的准入控制都是kubernetes自身的，并且是编译时织如。对于面向定制化、插件化的kubernetes提供了运行时的动态实现，可以让开发人员实现相关插件，动态织入并生效。

4.如何实现自己的准入控制插件

首先了解下Admission webhooks，它是接收许可请求并对其执行操作的HTTP回调，Admission webhooks有两个两种类型validating admission Webhook和mutating admission webhook。

注意:为了保证对象的最终状态，都应该有一个validating admission Webhook去验证，因为准入控制产检有后多个，在后续进过其他插件式对象数据可能会被修改。

Admission webhooks属于kubernetes控制面的一部分。

4.1、使用Admission webhooks的条件
4.2、kubernetes有哪些API

既然webhook是http的回调，那么首先得了解kubernetes中有哪些API接口

[root@node4 pki]# kubectl get --raw=/api/v1 |jq . |grep name\":
      "name": "bindings",
      "name": "componentstatuses",
      "name": "configmaps",
      "name": "endpoints",
      "name": "events",
      "name": "limitranges",
      "name": "namespaces",
      "name": "namespaces/finalize",
      "name": "namespaces/status",
      "name": "nodes",
      "name": "nodes/proxy",
      "name": "nodes/status",
      "name": "persistentvolumeclaims",
      "name": "persistentvolumeclaims/status",
      "name": "persistentvolumes",
      "name": "persistentvolumes/status",
      "name": "pods",
      "name": "pods/attach",
      "name": "pods/binding",
      "name": "pods/eviction",
      "name": "pods/exec",
      "name": "pods/log",
      "name": "pods/portforward",
      "name": "pods/proxy",
      "name": "pods/status",
      "name": "podtemplates",
      "name": "replicationcontrollers",
      "name": "replicationcontrollers/scale",
      "name": "replicationcontrollers/status",
      "name": "resourcequotas",
      "name": "resourcequotas/status",
      "name": "secrets",
      "name": "serviceaccounts",
      "name": "services",
      "name": "services/proxy",
      "name": "services/status",

kubernetes中资源是有类型和版本的，不同的资源类型和版本API也不同，其他可自行查看,常用的如下

[root@node4 pki]# kubectl get --raw=/apis/extensions/v1beta1 |jq . |grep name\":
[root@node4 pki]# kubectl get --raw=/apis/batch/v1 |jq . |grep name\":
[root@node4 pki]# kubectl get --raw=/apis/apps/v1 |jq . |grep name\":
4.3、针对特定的接口添加回调函数

以下两个场景来举例说明。创建namespaces时通过webhook添加label，创建pod是为其注入新的容器（istio中的sidecar实现类似）。

注册回调事件

http.HandleFunc("/namespaces", serveNamespaces)
http.HandleFunc("/pods", servePods)
server := &http.Server{
    Addr:      ":443",
    TLSConfig: configTLS(config),
}

将请求报文体转换为AdmissionReview

var body []byte
    if r.Body != nil {
        if data, err := ioutil.ReadAll(r.Body); err == nil {
            body = data
        }
    }

    // verify the content type is accurate
    contentType := r.Header.Get("Content-Type")
    if contentType != "application/json" {
        klog.Errorf("contentType=%s, expect application/json", contentType)
        return
    }

    klog.V(2).Info(fmt.Sprintf("handling request: %s", body))

    // The AdmissionReview that was sent to the webhook
    requestedAdmissionReview := v1beta1.AdmissionReview{}

    // The AdmissionReview that will be returned
    responseAdmissionReview := v1beta1.AdmissionReview{}

    deserializer := codecs.UniversalDeserializer()
    if _, _, err := deserializer.Decode(body, nil, &requestedAdmissionReview); err != nil {
        klog.Error(err)
        responseAdmissionReview.Response = toAdmissionResponse(err)
    } else {
        // pass to admitFunc
        responseAdmissionReview.Response = admit(requestedAdmissionReview)
    }

给pod注入label和sidecar 容器

func mutatePods(ar v1beta1.AdmissionReview) *v1beta1.AdmissionResponse {
    data,_ := json.Marshal(ar.Request.Object)
    fmt.Println(string(data))
    klog.V(2).Info("mutating pods")
    podResource := metav1.GroupVersionResource{Group: "", Version: "v1", Resource: "pods"}
    if ar.Request.Resource != podResource {
        klog.Errorf("expect resource to be %s", podResource)
        return nil
    }

    raw := ar.Request.Object.Raw
    pod := corev1.Pod{}
    deserializer := codecs.UniversalDeserializer()
    if _, _, err := deserializer.Decode(raw, nil, &pod); err != nil {
        klog.Error(err)
        return toAdmissionResponse(err)
    }
    reviewResponse := v1beta1.AdmissionResponse{}
    reviewResponse.Allowed = true
    fmt.Println("为了测试，此处指定只有pod name=demo时才注入")
    if pod.Name == "demo" {
        saMountName,saMount := getSAMount(pod.Spec.Containers)
        fmt.Println("原pod的secretMount的挂载名称："+saMountName)

        needAddedContainers := injectPod(saMount);
        patch := injectLabels()
        for _, container := range needAddedContainers{
            patch = append(patch, PatchOperation{
                Op:    "add",
                Path:  "/spec/containers/-",//此处虚注意，如果是数组类型，非第一个需要加上“/-”
                Value: container,
            })
        }
        patchBytes ,_ := json.Marshal(patch)
        reviewResponse.Patch = patchBytes
        fmt.Println("==========" + string(reviewResponse.Patch))
        pt := v1beta1.PatchTypeJSONPatch
        reviewResponse.PatchType = &pt
    }
    return &reviewResponse
}

func injectPod(secretMount corev1.VolumeMount) []corev1.Container{
    return []corev1.Container{
        {
            Name: "agent",
            Image: "prima/filebeat:6",
            ImagePullPolicy: corev1.PullIfNotPresent,
            VolumeMounts: []corev1.VolumeMount{secretMount},
        },
    }
}


//获取原容器中serviceaccount的挂载目录
func getSAMount(originContainer []corev1.Container)(string,corev1.VolumeMount){
    mountName := ""
    var mount corev1.VolumeMount
    // find service account secret volume mount(/var/run/secrets/kubernetes.io/serviceaccount,
    // https://kubernetes.io/docs/reference/access-authn-authz/service-accounts-admin/#service-account-automation) from app container
    for _, add := range originContainer {
        for _, vmount := range add.VolumeMounts {
            if vmount.MountPath == "/var/run/secrets/kubernetes.io/serviceaccount" {
                mountName = vmount.Name
                mount = vmount
            }
        }
    }
    return mountName,mount
}

func injectLabels() []PatchOperation{
    return []PatchOperation{
        {
            Op: "add",
            Path: "/metadata/labels",
            Value: map[string]string{
                "webhook-label": "HelloWebhook",
            },
        },
    }
}
4.4、如何部署admission webhook服务

部署admission webhook需要创建MutatingWebhookConfiguration和ValidatingWebhookConfiguration两个配置文件。

一个配置文件中可以包含多个webhook的配置，多个配置通过名称区分。Configuration的版本目前有v1和v1beta1,相比v1,v1beta1功能更加健壮，同时审核日志和度量更易于与激活的配置匹配。

①为webhook生成证书，此处使用cfssl

准备生成证书的配置文件
ca-csr.json

{
    "CN": "etcd",
    "key": {
        "algo": "rsa",
        "size": 2048
    },
    "names": [{
        "C": "CN",
        "ST": "NanJing",
        "L": "NanJing",
        "O": "Kubernetes",
        "OU": "Kubernetes-manual"
    }]
}

webhook-csr.json

{
    "CN": "webhook",
        "hosts": [
      "webhook.default.svc",
      "10.48.17.175",
          "localhost",
          "kubernetes",
          "kubernetes.default",
          "kubernetes.default.svc",
          "kubernetes.default.svc.cluster",
          "kubernetes.default.svc.cluster.local"
        ],

    "key": {
        "algo": "rsa",
        "size": 2048
    },
    "names": [{
        "C": "CN",
        "ST": "NanJing",
        "L": "NanJing",
        "O": "Kubernetes",
        "OU": "Kubernetes-manual"
    }]
}

生成配置证书文件

# 产生根证书
[root@node4 pki]# cfssl gencert -initca ca-csr.json | cfssljson -bare ca
[root@node4 pki]# cfssl gencert \
  -ca=ca.pem \
  -ca-key=ca-key.pem \
  -config=ca-config.json \
  -profile=kubernetes \
  webhook-csr.json | cfssljson -bare webhook
[root@node4 pki]# ll
total 36
-rw-r--r-- 1 root root  342 Nov 20 11:31 ca-config.json
-rw-r--r-- 1 root root 1017 Nov 20 11:27 ca.csr
-rw-r--r-- 1 root root  250 Nov 20 11:31 ca-csr.json
-rw------- 1 root root 1675 Nov 20 11:31 ca-key.pem
-rw-r--r-- 1 root root 1391 Nov 20 11:27 ca.pem
-rw-r--r-- 1 root root 1289 Nov 20 11:31 webhook.csr
-rw-r--r-- 1 root root  550 Nov 20 11:31 webhook-csr.json
-rw------- 1 root root 1675 Nov 20 11:31 webhook-key.pem
-rw-r--r-- 1 root root 1675 Nov 20 11:31 webhook.pem

②部署为webhook server

webhook server的部署可以通过deployment部署在集群内也可以部署在集群外，此处为了调试，直接在外部启动（注意证书生成时要指定外部的IP）,可以通过tls-cert-file和tls-private-key-file指定证书所在位置。

    var config Config
    config.CertFile ="F:/pki/webhook/webhook.pem"
    config.KeyFile="F:/pki/webhook/webhook-key.pem"
    config.addFlags()

    flag.Parse()
    http.HandleFunc("/namespaces", serveNamespaces)
    http.HandleFunc("/pods", servePods)
    http.HandleFunc("/ping", pong)
    server := &http.Server{
        Addr:      ":443",
        TLSConfig: configTLS(config),
    }
    fmt.Println("start ......")
    server.ListenAndServeTLS("", "")

③配置ValidatingWebhookConfiguration和MutatingWebhookConfiguration规则

MutatingWebhookConfiguration.yaml

kind: MutatingWebhookConfiguration
metadata:
  name: pod-webhook
webhooks:
  - name: pod.cloud.org
    failurePolicy: Fail
    clientConfig:
      url: "https://10.48.17.175:443/pods"
      caBundle: "Ci0tLS0tQk...<base64-encoded PEM bundle containing the CA that signed the webhook's serving certificate>...tLS0K"
    rules:
      - operations: [ "CREATE" ]
        apiGroups: [""]
        apiVersions: ["v1"]
        resources: ["pods"]
        scope: "*"

ValidatingWebhookConfiguration.yaml

kind: ValidatingWebhookConfiguration
metadata:
  name: pod-webhook
webhooks:
  - name: pod.cloud.org
    failurePolicy: Fail
    clientConfig:
      url: "https://10.48.17.175:443/pods"
      caBundle: "Ci0tLS0tQk...<base64-encoded PEM bundle containing the CA that signed the webhook's serving certificate>...tLS0K"
    rules:
      - operations: [ "CREATE" ]
        apiGroups: [""]
        apiVersions: ["v1"]
        resources: ["pods"]
        scope: "*"

除此之外，在1.15+版本中，可以规则还可以增加对象标签匹配、命名空间匹配，策略匹配（matchPolicy）。

apiVersion: admissionregistration.k8s.io/v1beta1
kind: MutatingWebhookConfiguration
webhooks:
- name: my-webhook.example.com
  objectSelector:
    matchLabels:
      foo: bar
  namespaceSelector:
     matchExpressions:
     - key: runlevel
       operator: NotIn
       values: ["0","1"]
  rules:
  - operations: ["CREATE"]
    apiGroups: ["*"]
    apiVersions: ["*"]
    resources: ["*"]
    scope: "*"

④部署配置

[root@node4 webhook]# kubectl apply -f MutatingWebhookConfiguration.yaml
[root@node4 webhook]# kubectl apply -f ValidatingWebhookConfiguration.yaml

只有匹配上述规则的请求才会被发送到对应的webhook

5.webhook测试

5.1测试名称为demo的pod

编写pod编排文件

apiVersion: v1
kind: Pod
metadata:
  name: demo
  namespace: webhook
spec:
  containers:
  - name: demo
    image: nginx:1.11.7
    imagePullPolicy: IfNotPresent

部署pod测试

[root@node4 webhook]# kubectl create ns webhook
namespace/webhook created
[root@node4 webhook]# kubectl apply -f nginx-pod.yaml 
pod/demo created

查看webhook打印的日志

image.png

查看标签和容器是否被注入

标签已被注入

image.png

容器已被注入

image.png

5.1测试名称为demo-webhook的pod

标签未注入


image.png

demo源码地址

上一篇下一篇

猜你喜欢

热点阅读