本文接上一篇介绍如何从pod内部访问kubernetes API server。所有的pod默认都关联上一个serviceAccount，只要该serviceAccount有权限访问你访问的资源对象，就可以直接访问。

我们使用default namespace中default serviceAccount，提前创建了一个role并将default和该role进行roleBinding。

前提

先创建role， kubectl create -f role.yaml

[root@node1 yqyaml]# cat role.yaml
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  namespace: default
  name: pod-reader
rules:
  - apiGroups: [""] # The API group "" indicates the core API Group.
    resources:
    - configmaps
    - secrets
    - nodes
    - nodes/metrics
    - nodes/stats
    - nodes/log
    - nodes/spec
    - nodes/proxy
    - pods
    - services
    - resourcequotas
    - replicationcontrollers
    - limitranges
    - persistentvolumeclaims
    - persistentvolumes
    - namespaces
    - endpoints
    - proxy
    verbs:
    - list
    - watch
    - get
  - apiGroups:
    - extensions
    resources:
    - daemonsets
    - deployments
    - replicasets
    - ingresses
    verbs:
    - list
    - watch
  - apiGroups:
    - apps
    resources:
    - statefulsets
    - daemonsets
    - deployments
    - replicasets
    verbs:
    - list
    - watch
  - apiGroups:
    - batch
    resources:
    - cronjobs
    - jobs
    verbs:
    - list
    - watch
  - apiGroups:
    - autoscaling
    resources:
    - horizontalpodautoscalers
    verbs:
    - list
    - watch
  - apiGroups:
    - authentication.k8s.io
    resources:
    - tokenreviews
    verbs:
    - create
  - apiGroups:
    - authorization.k8s.io
    resources:
    - subjectaccessreviews
    verbs:
    - create
    nonResourceURLs: []
[root@node1 yqyaml]#

然后绑定role和serviceAccount
kubectl create -f roleBinding1.yaml

[root@node1 yqyaml]# cat roleBinding1.yaml
# This role binding allows "test-deri" to read pods in the namespace "test-deri"
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: default-role-binding
  namespace: default
subjects:
  - kind: ServiceAccount # May be "User", "Group" or "ServiceAccount"
    name: default
roleRef:
  kind: Role
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io
[root@node1 yqyaml]#

最后检查绑定关系. 检查已经创建的role和roleBinding

[root@node1 yqyaml]# kubectl get serviceaccount
NAME         SECRETS   AGE
default      1         18d
myaccount2   1         8h
test1        1         4h58m
yqaccount    1         44h
[root@node1 yqyaml]# kubectl get role
NAME          AGE
pod-reader    45h
pod-reader2   45h
[root@node1 yqyaml]# kubectl get rolebinding
NAME                      AGE
default-role-binding      45h
default-role-binding2     44h
yqaccount-role-binding2   44h
[root@node1 yqyaml]#

解释：我的kubernetes上default空间已经创建很多role和serviceAccount，你只需要确保刚才提到的role pod-reader 和 rolebinding default-role-binding 存在就行。

简单的带有curl的镜像（非必须）

我先制作了一个简单的镜像，镜像只有curl工具, 可以直接使用其他任何带有curl工具的镜像。略过本步

Dockerfile文件

FROM alpine:latest
RUN apk add --update curl && rm -rf /var/cache/apk/*

然后执行命令（在Dockerfile文件所在目录执行，后者指定Dockerfile文件路径）

 docker build -t  local/curl:v1 .

执行完成后，查看生成的镜像：

[root@node1 dockerFiles]# docker images -a|grep local
local/curl                                           v1                  fa8e179516ee        46 hours ago        6.95MB
[root@node1 dockerFiles]#

pod yaml文件

可以发下明我意的pod中镜像文件是local/curl:v1，就是刚才生成的镜像。它的运行命令是 [ "/bin/sh", "-c", "sleep 60000" ]

[root@node1 yqyaml]# cat curlPodWithEnv.yaml
apiVersion: v1
kind: Pod
metadata:
  name: curl-yqaccount-meta-status-pod
spec:
  containers:
    - name: test-container
      image: local/curl:v1
      command: [ "/bin/sh", "-c", "sleep 60000" ]
      env:
        - name: SPECIAL_METADATA_NAME
          valueFrom:
            fieldRef:
             fieldPath: metadata.name
        - name: SPECIAL_HOST_IP
          valueFrom:
            fieldRef:
              fieldPath: status.hostIP
  restartPolicy: Never
[root@node1 yqyaml]#

访问 API Server

1，先进入的pod的容器中

2，执行如下命令获得token

 TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)

3，访问API server
其中API server的地址和端口可以通过env命令获取

curl --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt -H "Authorization: Bearer $TOKEN" -s  https://10.1.0.1:443/api/v1/namespaces/default/pods/

需要强调的是因为我的role配置的不同，导致不能直接访问https://10.1.0.1:443，但是可以访问https://10.1.0.1:443/api/v1/namespaces/default/pods/

podAccessAPIServer01.png

 # curl --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt -H "Authorization: Bearer $TOKEN" -s  https://10.1.0.1:443/api
{
  "kind": "APIVersions",
  "versions": [
    "v1"
  ],
  "serverAddressByClientCIDRs": [
    {
      "clientCIDR": "0.0.0.0/0",
      "serverAddress": "192.168.119.142:6443"
    }
  ]
}/ #

还可以在pod内删除其他pod

 curl -s  https://10.1.0.1/api/v1/namespaces/default/pods/{xxxpod} -X DELETE  -H "Authorization: Bearer $TOKEN"    --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt

podAccessAPIDeletePod.png

提示：我的default serviceAccount绑定了两个role，另外一个role是pod-reader2

[root@node1 yqyaml]# cat simpleRole.yaml
kind: Role
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  namespace: default
  name: pod-reader2
rules:
  - apiGroups:
    - '*'
    resources:
    - '*'
    verbs:
    - '*'

如取消关联pod-reader2，按我的default serviceaccount可以访问获取pod list但是不能删除，可以参考如下结果

podCanDelete.png

curl

curl的使用方法，请参考阮一峰老师的博客，http://www.ruanyifeng.com/blog/2019/09/curl-reference.html

pod内访问kubernetes API server

前提

简单的带有curl的镜像（非必须）

pod yaml文件

访问 API Server

curl

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