Kubernetes RBAC 之 ServiceAccount

Kubernetes RBAC 之 ServiceAccount

定义

RABC 英文全称是 Role-Based Access Control，它通过角色绑定账户，来使得账户拥有某些操控 K8S 集群的权限。ServiceAccount 是集群内部 Pod 访问集群所使用的服务账户，它包括了 Namespace、Token、Ca 证书，并且通过目录挂载的方式绑定 Pod。当 Pod 运行起来的时候，就会使用这些信息与 ApiServer 进行通信。

使用

1. 创建 sa 账户 sa-test

   kubectl create sa sa-test
   

2. 创建绑定 sa-test 账户的 Pod

   apiVersion: v1
   kind: Pod
   metadata:
     name: rbac-sa
     namespace: default
     labels:
       app:  nginx
   spec:
     serviceAccountName: sa-test
     containers:
       - name:  curl-nginx
         ports:
           - containerPort: 80
         image: curl-nginx:1.0
         imagePullPolicy: IfNotPresent
   

3. 访问新建立 Pod，发现没有权限访问 ApiServer

   root@k8s-master1:~# kubectl exec -it rbac-sa -- /bin/sh
   / # cd /var/run/secrets/kubernetes.io/serviceaccount/
   /var/run/secrets/kubernetes.io/serviceaccount # ls -l
   total 0
   lrwxrwxrwx    1 root     root            13 Jul  6 02:59 ca.crt -> ..data/ca.crt
   lrwxrwxrwx    1 root     root            16 Jul  6 02:59 namespace -> ..data/namespace
   lrwxrwxrwx    1 root     root            12 Jul  6 02:59 token -> ..data/token
   
   /var/run/secrets/kubernetes.io/serviceaccount # curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat ./token)"  https://kubernetes/api/v1/namespaces/kube-system
   {
     "kind": "Status",
     "apiVersion": "v1",
     "metadata": {},
     "status": "Failure",
     "message": "namespaces \"kube-system\" is forbidden: User \"system:serviceaccount:default:sa-test\" cannot get resource \"namespaces\" in API group \"\" in the namespace \"kube-system\"",
     "reason": "Forbidden",
     "details": {
       "name": "kube-system",
       "kind": "namespaces"
     },
     "code": 403
   }
   /var/run/secrets/kubernetes.io/serviceaccount #
   

4. 赋予 sa-test 权限

   root@k8s-master1:~# kubectl create clusterrolebinding sa-test-admin --clusterrole=cluster-admin  --serviceaccount=default:sa-test
   clusterrolebinding.rbac.authorization.k8s.io/sa-test-admin created
   

5. 再次访问

   root@k8s-master1:~# kubectl exec -it rbac-sa -- /bin/sh
   / # curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat ./token)"  https://kubernetes/api/v1/namespaces/kube-system
   /var/run/secrets/kubernetes.io/serviceaccount # curl --cacert ./ca.crt  -H "Authorization: Bearer $(cat ./token)"  https://kubernetes/api/v1/namespaces/kube-system
   {
     "kind": "Namespace",
     "apiVersion": "v1",
     "metadata": {
       "name": "kube-system",
       "uid": "6a42a1bb-6375-4658-9948-7f395e509197",
       "resourceVersion": "26",
       "creationTimestamp": "2024-05-13T00:41:10Z",
       "labels": {
         "kubernetes.io/metadata.name": "kube-system"
       },
       "managedFields": [
         {
           "manager": "kube-apiserver",
           "operation": "Update",
           "apiVersion": "v1",
           "time": "2024-05-13T00:41:10Z",
           "fieldsType": "FieldsV1",
           "fieldsV1": {
             "f:metadata": {
               "f:labels": {
                 ".": {},
                 "f:kubernetes.io/metadata.name": {}
               }
             }
           }
         }
       ]
     },
     "spec": {
       "finalizers": [
         "kubernetes"
       ]
     },
     "status": {
       "phase": "Active"
     }
   }/var/run/secrets/kubernetes.io/serviceaccount #