如何使用curl通路k8s的apiserver

作者：牧原

使用TOKEN授權通路api-server在k8s運維場景中比較常見，

apiserver有三種級别的用戶端認證方式

1、HTTPS證書認證：基于CA根證書簽名的雙向數字證書認證方式

2、HTTP Token認證：通過一個Token來識别合法使用者

3、HTTP Base認證：通過使用者名+密碼的認證方式

通常的運維場景使用第二種Token較為友善Token的權限是關聯service account,

# kubectl describe secrets admin-token-2q28f -n kube-system

Name:         admin-token-2q28f
Namespace:    kube-system
Labels:       <none>
Annotations:  kubernetes.io/service-account.name: admin
              kubernetes.io/service-account.uid: 93316ffa-7545-11e9-b617-00163e06992d
Type:  kubernetes.io/service-account-token
Data
====
ca.crt:     1419 bytes
namespace:  11 bytes
token:      eyJhbGciOiJ******           

Service Account 的權限來自Clusterrolebinding-->ClusterRole

# kubectl describe serviceaccount admin -n kube-system

Name:                admin
Namespace:           kube-system
Labels:              <none>
Annotations:         kubectl.kubernetes.io/last-applied-configuration:
                       {"apiVersion":"v1","kind":"ServiceAccount","metadata":{"annotations":{},"name":"admin","namespace":"kube-system"}}
Image pull secrets:  <none>
Mountable secrets:   admin-token-2q28f
Tokens:              admin-token-2q28f
Events:              <none>           

通過clusterrolebinding 可以拿到ClusterRole對應的rolename

# kubectl get clusterrolebinding admin -o yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"rbac.authorization.k8s.io/v1beta1","kind":"ClusterRoleBinding","metadata":{"annotations":{},"name":"admin"},"roleRef":{"apiGroup":"rbac.authorization.k8s.io","kind":"ClusterRole","name":"cluster-admin"},"subjects":[{"kind":"ServiceAccount","name":"admin","namespace":"kube-system"}]}
  creationTimestamp: 2019-05-13T06:08:49Z
  name: admin
  resourceVersion: "1523"
  selfLink: /apis/rbac.authorization.k8s.io/v1/clusterrolebindings/admin
  uid: 93356439-7545-11e9-b617-00163e06992d
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: admin
  namespace: kube-system           

這個role是什麼權限?

# kubectl get clusterrole cluster-admin -o yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  creationTimestamp: 2019-05-13T06:01:10Z
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: cluster-admin
  resourceVersion: "55"
  selfLink: /apis/rbac.authorization.k8s.io/v1/clusterroles/cluster-admin
  uid: 817e2b9e-7544-11e9-9766-00163e0e34c8
rules:
- apiGroups:
  - '*'
  resources:
  - '*'
  verbs:
  - '*'
- nonResourceURLs:
  - '*'
  verbs:
  - '*'           

從clusterrole權限來看，admin關聯的權限還是比較大的，正常的叢集運維中建議根據自身的真實需要，去定制權限

https://kubernetes.io/docs/reference/access-authn-authz/rbac/

了解完這些，分享一個小技巧，這樣後面客戶再有curl通路apiserver的需求，我相信你沒問題了！

# kubectl describe secrets $(kubectl get secrets -n kube-system |grep admin |cut -f1 -d ' ') -n kube-system |grep -E '^token' |cut -f2 -d':'|tr -d '\t'|tr -d ' '

eyJhbGciOiJSUzI1NiIsImtpZCI6IiJ9.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNlYWNjb3VudC9uYW1lc3BhY2UiOiJrdWJlLXN5c3RlbSIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VjcmV0Lm5hbWUiOiJhZG1pbi10b2tlbi0ycTI4ZiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50Lm5hbWUiOiJhZG1pbiIsImt1YmVybmV0ZXMuaW8vc2VydmljZWFjY291bnQvc2VydmljZS1hY2NvdW50LnVpZCI6IjkzMzE2ZmZhLTc1NDUtMTFlOS1iNjE3LTAwMTYzZTA2OTkyZCIsInN1YiI6InN5c3RlbTpzZXJ2aWNlYWNjb3VudDprdWJlLXN5c3RlbTphZG1pbiJ9.EQzj2LsWn2k31m-ksn9GmB1bZTi1Xjw1fnmWFgRKlwhS2QAaVnDXfV_TgUovpq5oWKh7h0gTVaNaK4KKK76yAv6GfMehpOdIO5xHCfQAWVRhla1cwUDC64tz7vJ1zGcx_lz4hKfhdXN1T8FYS0B0hf3h2OloAMfCZTzDjRWz24GVwH-WRTEwY_5tav65GiZzBTsnz1vV7NOcx-Kl8AK2HbowtBYqK05x7oOmp84FiQMwpYU-7g0c03h61zev4lvf0e-HFtqKiByPi8gD-uiVRvE-xayOz5oIESWw2GfhzfNf_uyR7eLplCKUBecVMtwVsBauNaeqU-IIJW5VIHAOxw
# TOKEN=$(kubectl describe secrets $(kubectl get secrets -n kube-system |grep admin |cut -f1 -d ' ') -n kube-system |grep -E '^token' |cut -f2 -d':'|tr -d '\t'|tr -d ' ')

# kubectl config view |grep server|cut -f 2- -d ":" | tr -d " "

https://192.168.0.130:6443
# APISERVER=$(kubectl config view |grep server|cut -f 2- -d ":" | tr -d " ")           

使用curl通路apiserver

# curl -H "Authorization: Bearer $TOKEN" $APISERVER/api  --insecure

{
  "kind": "APIVersions",
  "versions": [
    "v1"
  ],
  "serverAddressByClientCIDRs": [
    {
      "clientCIDR": "0.0.0.0/0",
      "serverAddress": "192.168.0.130:6443"
    }
  ]
}