kubernetes 系统 :discovery role mechanism

Question

我想了解 system:discovery 角色在 kubernetes 中是如何工作的。我能够在下面看到非资源 url 是 system:discovery 角色中包含的特权

root@kubemas:~# kubectl describe clusterrole system:discovery
Name:         system:discovery
Labels:       kubernetes.io/bootstrapping=rbac-defaults
Annotations:  rbac.authorization.kubernetes.io/autoupdate: true
PolicyRule:
  Resources  Non-Resource URLs  Resource Names  Verbs
  ---------  -----------------  --------------  -----
             [/api/*]           []              [get]
             [/api]             []              [get]
             [/apis/*]          []              [get]
             [/apis]            []              [get]
             [/healthz]         []              [get]
             [/livez]           []              [get]
             [/openapi/*]       []              [get]
             [/openapi]         []              [get]
             [/readyz]          []              [get]
             [/version/]        []              [get]
             [/version]         []              [get]

来自 clusterrolebinding 描述，

root@kubemas:~# kubectl describe clusterrolebindings.rbac.authorization.k8s.io system:discovery
Name:         system:discovery
Labels:       kubernetes.io/bootstrapping=rbac-defaults
Annotations:  rbac.authorization.kubernetes.io/autoupdate: true
Role:
  Kind:  ClusterRole
  Name:  system:discovery
Subjects:
  Kind   Name                  Namespace
  ----   ----                  ---------
  Group  system:authenticated  

我只能看到 system:authenticated 组可以访问非资源 url。如果我执行以下命令，我可以理解，请求用户是 system:anonymous，属于 system:unathenticated 组，因此不允许看到输出

root@kubemas:~# curl -k https://192.168.56.101:6443/api
{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {

  },
  "status": "Failure",
  "message": "forbidden: User \"system:anonymous\" cannot get path \"/api\"",
  "reason": "Forbidden",
  "details": {

  },
  "code": 403

但是我期望下面的请求会得到同样的结果，我正在尝试获取也是非资源 url 的 kubernetes 版本。但是我能够无错误地获得版本输出。所以这是如何工作的。我是误解了这个机制？

root@kubemas:~# curl -k https://192.168.56.101:6443/version
{
  "major": "1",
  "minor": "18",
  "gitVersion": "v1.18.3",
  "gitCommit": "2e7996e3e2712684bc73f0dec0200d64eec7fe40",
  "gitTreeState": "clean",
  "buildDate": "2020-05-20T12:43:34Z",
  "goVersion": "go1.13.9",
  "compiler": "gc",
  "platform": "linux/amd64"
}root@kubemas:~#

Answer 1

system:public-info-viewer 是可以访问 /version 的集群角色。此 clusterole 绑定(bind)到 system:authenticated 和 system:unauthenticated 组。由于它绑定(bind)到 system:unauthenticated 组，您可以访问它。

来自docs

This clusterole Allows read-only access to non-sensitive information about the cluster. Introduced in Kubernetes v1.14.

kubectl describe clusterrole system:public-info-viewer
Name:         system:public-info-viewer
Labels:       kubernetes.io/bootstrapping=rbac-defaults
Annotations:  rbac.authorization.kubernetes.io/autoupdate: true
PolicyRule:
  Resources  Non-Resource URLs  Resource Names  Verbs
  ---------  -----------------  --------------  -----
             [/healthz]         []              [get]
             [/livez]           []              [get]
             [/readyz]          []              [get]
             [/version/]        []              [get]
             [/version]         []              [get]