Kubernetes系统安全-准入控制(admission control)

　　　　　　　　　　　　　　　Kubernetes系统安全-准入控制(admission control)

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　作者：尹正杰

版权声明：原创作品，谢绝转载！否则将追究法律责任。 

 

 

 

一.准入控制(admission control)概述

1>.常见的准入控制器(Admission Controllers)

　　AlwaysAdmit(DEPRECATED):
　　　　该准入控制器已被废弃,总是允许，所有的请求(包括不符合定义)的规则都允许，如果有不符合的规则请求会日志记录而已，和临时关闭selinux的功能有点像。
　　AlwaysPullImages:
　　　　无论你拉取镜像的规则定义成什么类型，总是会去拉取镜像，也就是强制避免使用本地镜像，即无视本地镜像定义的拉取规则。
　　AlwaysDeny(DEPRECATED):
　　　　该准入控制器已被废弃,和AlwaysAdmit相反，所有请求(包括符合定义)的规则拒绝。
　　DefaultStorageClass:
　　　　指定默认的存储类。
　　DefaultTolerationSeconds
　　DenyEscalatingExec
　　EventRateLimit(alpha)
　　ExtendedResourceToleration
　　ImagePolicyWebhook
　　Initializers(alpha)
　　LimitPodHardAnitiAffinityTopology
　　LimitRanger:
　　　　允许在名称空间中创建一个LimitRange资源，任何Pod都需要指定一个资源上限和下限的范围，若未指定会使用默认值。
　　MutaingAdmission Webhook(beta in 1.9)
　　NamespaceAutoProvision
　　NamespaceExists:
　　　　检查名称空间是否存在的控制器。
　　NamespaceLifecycle
　　NodeRestriction
　　OwnerReferencesPermissionEnforcement
　　PodNodeSelector
　　PersistentVolumeClaimResize
　　PodPreset
　　PodSecurityPolicy:
　　　　为Pod定义安全策略。
　　PodTolerationRestriction
　　Priority
　　ResourceQuota:
　　　　允许在名称空间中创建一个ResourceQuota资源,可以明确指定Pod使用资源的配额，比如内存不允许超过20G，允许使用的总的PVC数量等K8S集群资源。
　　SecurityContextDeny
　　ServiceAccount:
　　　　比如创建的Pod内部默认有一个存储卷，每个存储卷对应了一个secret用于ApiServer认证,这就是ServiceAccount来定义的。
　　Storage Object in Use Protection
　　ValidatingAdmission Webhook(alpha in 1.8;beta in 1.9)　　

2>.打开或者关闭控制器

　　Kubernetes API server标志enable adminimission plugins接受在修改集群中的对象之前要调用的许可控制插件的逗号分隔列表。使用"--enable-admission-plugins="指定，如下图所示。

　　Kubernetes API服务器标志disable admission plugins接受一个逗号分隔的要禁用的许可控制插件列表，即使它们在默认启用的插件列表中。使用"--disable-admission-plugins="。

 

二.LimitRange and LimitRanger

　　Pod 对象虽然支持使用requests和limits进行可用计算资源配置，但它们却非强制选项;

　　LimitRange的主要目的是确保请求和/限制根据其规范自动关联到容器;

　　如果容器是在具有默认内存限制的命名空间中创建的，并且该容器未指定其自己的内存限制，则会为该容器分配默认内存限制;

　　由limit range对象定义的限制范围枚举pod和container级别的命名空间中的计算资源约束，并指定pod或container可以消耗的资源量。

　　对项目中的每个LimitRange对象评估所有资源创建和修改请求，如果资源未设置显式值，并且约束支持默认值，则将默认值应用于资源。

　　LimitRanger将观察传入的请求，并确保它不违反命名空间中LimitRange对象中枚举的任何约束:
　　　　所有资源创建和修改请求都是根据命名空间中的每个LimitRange对象计算的;
　　　　如果资源违反任何枚举约束，则资源将被拒绝。
　　　　如果资源未设置显式值，并且约束支持默认值，则将默认值应用于资源。

　　LimitRanger还可用于将默认资源请求应用于未指定任何的pod；当前，默认LimitRanger将0.1 CPU需求应用于默认命名空间中的所有pod。

1>.创建LimitRange资源

[root@master200.yinzhengjie.org.cn ~]# vim /yinzhengjie/data/k8s/manifests/limitrange-demo.yaml 
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# cat /yinzhengjie/data/k8s/manifests/limitrange-demo.yaml 
apiVersion: v1
kind: LimitRange
metadata:
  name: cpu-limit-range
  namespace: yinzhengjie-admission-control
spec:
  limits:
  - default:
      cpu: 1000m
    defaultRequest:
      cpu: 1000m
    min:
      cpu: 500m
    max:
      cpu: 2000m
    maxLimitRequestRatio:
      cpu: 4
    type: Container
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl create ns yinzhengjie-admission-control
namespace/yinzhengjie-admission-control created
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl get ns
NAME                            STATUS   AGE
default                         Active   15d
develop                         Active   13h
kube-node-lease                 Active   15d
kube-public                     Active   15d
kube-system                     Active   15d
kubernetes-dashboard            Active   14h
yinzhengjie-admission-control   Active   7s
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl apply -f /yinzhengjie/data/k8s/manifests/limitrange-demo.yaml 
limitrange/cpu-limit-range created
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl describe limitrange cpu-limit-range -n yinzhengjie-admission-control
Name:       cpu-limit-range
Namespace:  yinzhengjie-admission-control
Type        Resource  Min   Max  Default Request  Default Limit  Max Limit/Request Ratio
----        --------  ---   ---  ---------------  -------------  -----------------------
Container   cpu       500m  2    1                1              4
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 

2>.使用默认的LimitRange

[root@master200.yinzhengjie.org.cn ~]# vim /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# cat /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: yinzhengjie-admission-control
spec:
  containers:
  - image: ikubernetes/myapp:v1
    imagePullPolicy: IfNotPresent
    name: myapp
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl apply -f /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
pod/pod-demo created
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl get pods -n yinzhengjie-admission-control
NAME       READY   STATUS    RESTARTS   AGE
pod-demo   1/1     Running   0          18s
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl describe pods -n yinzhengjie-admission-control
Name:         pod-demo
Namespace:    yinzhengjie-admission-control
Priority:     0
Node:         node203.yinzhengjie.org.cn/172.200.1.203
Start Time:   Thu, 20 Feb 2020 03:37:13 +0800
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"pod-demo","namespace":"yinzhengjie-admission-control"},"spec":{"conta...
              kubernetes.io/limit-ranger: LimitRanger plugin set: cpu request for container myapp; cpu limit for container myapp
Status:       Running
IP:           10.244.3.4
IPs:
  IP:  10.244.3.4
Containers:
  myapp:
    Container ID:   docker://503619b6cd5b1f6e7a0f0394d9710df9d6fe6621c16fdd06466520e3df2989e7
    Image:          ikubernetes/myapp:v1
    Image ID:       docker-pullable://ikubernetes/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Thu, 20 Feb 2020 03:37:22 +0800
    Ready:          True
    Restart Count:  0
    Limits:
      cpu:  1
    Requests:
      cpu:        1
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-r5wq6 (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-r5wq6:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-r5wq6
    Optional:    false
QoS Class:       Burstable
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From                                 Message
  ----    ------     ----  ----                                 -------
  Normal  Scheduled  25s   default-scheduler                    Successfully assigned yinzhengjie-admission-control/pod-demo to node203.yinzhengjie.org.cn
  Normal  Pulling    24s   kubelet, node203.yinzhengjie.org.cn  Pulling image "ikubernetes/myapp:v1"
  Normal  Pulled     16s   kubelet, node203.yinzhengjie.org.cn  Successfully pulled image "ikubernetes/myapp:v1"
  Normal  Created    16s   kubelet, node203.yinzhengjie.org.cn  Created container myapp
  Normal  Started    16s   kubelet, node203.yinzhengjie.org.cn  Started container myapp
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl get pods -n yinzhengjie-admission-control
NAME       READY   STATUS    RESTARTS   AGE
pod-demo   1/1     Running   0          2m21s
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl delete -f /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
pod "pod-demo" deleted
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl get pods -n yinzhengjie-admission-control
No resources found in yinzhengjie-admission-control namespace.
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 

3>.使用自定义的LimitRange(如果指定的资源范围不在范围内则会无法创建Pod)

[root@master200.yinzhengjie.org.cn ~]# vim /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# cat /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: yinzhengjie-admission-control
spec:
  containers:
  - image: ikubernetes/myapp:v1
    imagePullPolicy: IfNotPresent
    name: myapp
    resources:
      requests:
        cpu: 500m
      limits:
        cpu: 1500m
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl describe limitrange cpu-limit-range -n yinzhengjie-admission-control
Name:       cpu-limit-range
Namespace:  yinzhengjie-admission-control
Type        Resource  Min   Max  Default Request  Default Limit  Max Limit/Request Ratio
----        --------  ---   ---  ---------------  -------------  -----------------------
Container   cpu       500m  2    1                1              4
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl apply -f /yinzhengjie/data/k8s/manifests/pod/test-limit-range.yaml
pod/pod-demo created
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl get pods -n yinzhengjie-admission-control pod-demo -o wide
NAME       READY   STATUS    RESTARTS   AGE   IP           NODE                         NOMINATED NODE   READINESS GATES
pod-demo   1/1     Running   0          59s   10.244.3.5   node203.yinzhengjie.org.cn   <none>           <none>
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl describe pods -n yinzhengjie-admission-control pod-demo
Name:         pod-demo
Namespace:    yinzhengjie-admission-control
Priority:     0
Node:         node203.yinzhengjie.org.cn/172.200.1.203
Start Time:   Thu, 20 Feb 2020 03:49:42 +0800
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"pod-demo","namespace":"yinzhengjie-admission-control"},"spec":{"conta...
Status:       Running
IP:           10.244.3.5
IPs:
  IP:  10.244.3.5
Containers:
  myapp:
    Container ID:   docker://a991046c9cff1008ae93458dfd90c729794ac7a794df9e9507c92b8aa84646c3
    Image:          ikubernetes/myapp:v1
    Image ID:       docker-pullable://ikubernetes/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Thu, 20 Feb 2020 03:49:43 +0800
    Ready:          True
    Restart Count:  0
    Limits:
      cpu:  1500m
    Requests:
      cpu:        500m
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-r5wq6 (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-r5wq6:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-r5wq6
    Optional:    false
QoS Class:       Burstable
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From                                 Message
  ----    ------     ----  ----                                 -------
  Normal  Scheduled  23s   default-scheduler                    Successfully assigned yinzhengjie-admission-control/pod-demo to node203.yinzhengjie.org.cn
  Normal  Pulled     22s   kubelet, node203.yinzhengjie.org.cn  Container image "ikubernetes/myapp:v1" already present on machine
  Normal  Created    22s   kubelet, node203.yinzhengjie.org.cn  Created container myapp
  Normal  Started    22s   kubelet, node203.yinzhengjie.org.cn  Started container myapp
[root@master200.yinzhengjie.org.cn ~]# 

 

三.ResourceQuota

　　由ResourceQuota对象定义的资源配额提供限制每个命名空间聚合资源消耗的约束。

　　它可以按类型限制可以在命名空间中创建的对象的数量，以及该命名空间中的资源可能消耗的计算资源和存储的总量。

　　LimitRange用于定义单个Pod对象上计算资源的requests及limits，而ResourceQuota则负责为整个namespace设定资源配额。

　　当特定命名空间中存在资源配额时，将在该命名空间中强制资源配额。

　　ResourceQuota对象的生效依赖于ResourceQuota Admission Controller.

1>.创建resourcequota资源

[root@master200.yinzhengjie.org.cn ~]# vim /yinzhengjie/data/k8s/manifests/basic/resoucequota-demo.yaml 
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# cat /yinzhengjie/data/k8s/manifests/basic/resoucequota-demo.yaml 
apiVersion: v1
kind: ResourceQuota
metadata:
  name: quota-example
  namespace: yinzhengjie-admission-control
spec:
  hard:
    pods: "5"
    requests.cpu: "1"
    requests.memory: 1Gi
    limits.cpu: "2"
    limits.memory: 2Gi
    count/deployments.apps: "2"
    count/deployments.extensions: "2"
    persistentvolumeclaims: "2"
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl apply -f /yinzhengjie/data/k8s/manifests/basic/resoucequota-demo.yaml 
resourcequota/quota-example created
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# kubectl get resourcequota -n yinzhengjie-admission-control
NAME            CREATED AT
quota-example   2020-02-19T20:38:34Z
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl describe resourcequota -n yinzhengjie-admission-control
Name:                         quota-example
Namespace:                    yinzhengjie-admission-control
Resource                      Used   Hard
--------                      ----   ----
count/deployments.apps        0      2
count/deployments.extensions  0      2
limits.cpu                    1500m  2
limits.memory                 0      2Gi
persistentvolumeclaims        0      2
pods                          1      5
requests.cpu                  500m   1
requests.memory               0      1Gi
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 

2>.使用自定义的resourcequota的资源限制

[root@master200.yinzhengjie.org.cn ~]# kubectl describe resourcequota -n yinzhengjie-admission-control
Name:                         quota-example
Namespace:                    yinzhengjie-admission-control
Resource                      Used   Hard
--------                      ----   ----
count/deployments.apps        0      2
count/deployments.extensions  0      2
limits.cpu                    1500m  2
limits.memory                 0      2Gi
persistentvolumeclaims        0      2
pods                          1      5
requests.cpu                  500m   1
requests.memory               0      1Gi
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# vim /yinzhengjie/data/k8s/manifests/basic/pod-demo.yaml 
[root@master200.yinzhengjie.org.cn ~]# 
[root@master200.yinzhengjie.org.cn ~]# cat /yinzhengjie/data/k8s/manifests/basic/pod-demo.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: mynginx
  namespace: yinzhengjie-admission-control
  labels:
    app: pod-demo
    rel: stable
spec:
  containers:
  - name: mynginx
    image: nginx:1.14-alpine
    resources:
      requests:
        cpu: 500m
        memory: 500Mi
      limits:
        cpu: 500m
        memory: 1Gi
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl apply -f /yinzhengjie/data/k8s/manifests/basic/pod-demo.yaml 
pod/mynginx created
[root@master200.yinzhengjie.org.cn ~]# 

[root@master200.yinzhengjie.org.cn ~]# kubectl describe resourcequota -n yinzhengjie-admission-control
Name:                         quota-example
Namespace:                    yinzhengjie-admission-control
Resource                      Used   Hard
--------                      ----   ----
count/deployments.apps        0      2
count/deployments.extensions  0      2
limits.cpu                    2      2
limits.memory                 1Gi    2Gi
persistentvolumeclaims        0      2
pods                          2      5
requests.cpu                  1      1
requests.memory               500Mi  1Gi
[root@master200.yinzhengjie.org.cn ~]# 

 

四.PodSecurityPolicy(定义Pod的安全策略)

1>.定义受限制的pod的安全策略参考配置清单 

[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# cat psp-restricted.yaml 
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: restricted
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: 'docker/default'
    seccomp.security.alpha.kubernetes.io/defaultProfileName:  'docker/default'
spec:
  privileged: false
  allowPrivilegeEscalation: false
  requiredDropCapabilities:
    - ALL
  volumes:
    - 'configMap'
    - 'emptyDir'
    - 'projected'
    - 'secret'
    - 'downwardAPI'
    - 'persistentVolumeClaim'
  hostNetwork: false
  hostIPC: false
  hostPID: false
  runAsUser:
    rule: 'MustRunAsNonRoot'
  seLinux:
    rule: 'RunAsAny'
  supplementalGroups:
    rule: 'MustRunAs'
    ranges:
      - min: 1
        max: 65535
  fsGroup:
    rule: 'MustRunAs'
    ranges:
      - min: 1
        max: 65535
  readOnlyRootFilesystem: false
[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# 

2>.定义有特权的pod的安全策略参考配置清单

[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# cat psp-privileged.yaml 
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: privileged
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
spec:
  privileged: true
  allowPrivilegeEscalation: true
  allowedCapabilities:
  - '*'
  volumes:
  - '*'
  hostNetwork: true
  hostPorts:
  - min: 0
    max: 65535
  hostIPC: true
  hostPID: true
  runAsUser:
    rule: 'RunAsAny'
  seLinux:
    rule: 'RunAsAny'
  supplementalGroups:
    rule: 'RunAsAny'
  fsGroup:
    rule: 'RunAsAny'
[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# 

3>.安全策略调用参考配置文件

[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# cat clusterrole-with-psp.yaml 
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: psp:restricted
rules:
- apiGroups: ['policy']
  resources: ['podsecuritypolicies']
  verbs:     ['use']
  resourceNames:
  - restricted
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: psp:privileged
rules:
- apiGroups: ['policy']
  resources: ['podsecuritypolicies']
  verbs:     ['use']
  resourceNames:
  - privileged
[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# 

[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# cat clusterrolebinding-with-psp.yaml 
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: restricted-psp-user
roleRef:
  kind: ClusterRole
  name: psp:restricted
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: Group
  apiGroup: rbac.authorization.k8s.io
  name: system:authenticated
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: privileged-psp-user
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: psp:privileged
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:masters
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:node
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:serviceaccounts:kube-system
[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# 
[root@master200.yinzhengjie.org.cn ~/Kubernetes_Advanced_Practical/chapter10]# 

 

五.准入控制器扩展

　　Admission Controllers代码必须要编译进kube-apiserver,且只能在程序启动时进行配置，于是，Kubernetes又特地引入了Admission Webhooks(beta in 1.9)和Initializers(alpha)来尝试突破此限制，以允许用户单独开发主奴人控制器并运行时进行配置。

　　允许webhook是接收请求并对其执行操作的HTTP回调。
　　　　您可以定义两种类型的许可Webhook，验证许可Webhook和变异许可Webhook。
　　　　通过验证许可webhook，您可以拒绝执行自定义许可策略的请求
　　　　使用变异的允许webhook，您可以更改请求以强制使用自定义默认值。