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

创建 sa 账户 sa-test
shell 复制代码
```
kubectl create sa sa-test
```

创建绑定 sa-test 账户的 Pod

yaml 复制代码

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

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 #

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

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 #