kubernetes API 访问控制 1.Authentication（认证）：认证方式现共有8种，可以启用一种或多种认证方式，只要有一种认证方式通过，就不再 进行其它方式的认证。通常启用X509 Client Certs和Service Accout Tokens两种认证方式。 Kubernetes集群有两类用户：由Kubernetes管理的Service Accounts （服务账户）和 （Users Accounts） 普通账户。 k8s中账号的概念不是我们理解的账号，它并不真的存在， 它只是形式上存在。
2.Authorization（授权）：必须经过认证阶段，才到授权请求，根据所有授权策略匹配请求资源属性，决定允许或拒 绝请求。授权方式现共有6种，AlwaysDeny、AlwaysAllow、ABAC、RBAC、Webhook、 Node。默认集群强制开启RBAC。
3.Admission Control（准入控制）： 用于拦截请求的一种方式，运行在认证、授权之后，是权限认证链上的最后一环，对请求 API资源对象进行修改和校验。
访问k8s的API Server的客户端主要分为两类： • kubectl ： 用户家目录中的 .kube/config 里面保存了客户端访问API Server的密钥相关信息， 这样当用kubectl访问k8s时，它就会自动读取该配置文件，向API Server发起认证，然后完成操作请求。 • pod： Pod中的进程需要访问API Server，如果是人去访问或编写的脚本去访问，这类访问 使用的账号为：UserAccount；而Pod自身去连接API Server时，使用的账号是： ServiceAccount，生产中后者使用居多。
• kubectl向apiserver发起的命令,采用的是http方式,其实就是对URL发起增删改查的操作。 kubectl proxy --port=8888 & curl http://localhost:8888/api/v1/namespaces/default curl http://localhost:8888/apis/apps/v1/namespaces/default/deployments 以上两种api的区别是： • api它是一个特殊链接,只有在核心v1群组中的对象才能使用。 • apis 它是一般API访问的入口固定格式名。
UserAccount与serviceaccount： • 用户账户是针对人而言的。 服务账户是针对运行在 pod 中的进程而言的。 • 用户账户是全局性的。 其名称在集群各 namespace 中都是全局唯一的，未来的用户资源不会做 namespace 隔离， 服务账户是 namespace 隔离的。 • 通常情况下，集群的用户账户可能会从企业数据库进行同步，其创建需要特殊权限，并且涉及到复杂的业务流程。 服务账户创建的目的是为了更轻量，允许集群用户为了具体的任务创建服务账户 ( 即权限最小化原则 )。
kubectl create serviceaccount admin serviceaccount/admin created创建serviceaccount kubectl describe sa admin 此时k8s为用户自动生成认证信息，但没有授权
[kubeadm@server1 cm]$ kubectl get sa NAME SECRETS AGE default 1 15d nfs-client-provisioner 1 2d2h [kubeadm@server1 cm]$ kubectl create serviceaccount admin serviceaccount/admin created [kubeadm@server1 cm]$ kubectl get sa NAME SECRETS AGE admin 1 1s default 1 15d nfs-client-provisioner 1 2d2h [kubeadm@server1 cm]$ kubectl describe sa admin Name: admin Namespace: default Labels: <none> Annotations: <none> Image pull secrets: <none> Mountable secrets: admin-token-vlffb Tokens: admin-token-vlffb Events: <none>kubectl patch serviceaccount admin -p '{"imagePullSecrets": [{"name": "myregistrykey"}]}'添加secrets到serviceaccount中
[kubeadm@server1 cm]$ kubectl patch serviceaccount admin -p '{"imagePullSecrets": [{"name": "myregistrykey"}]}' serviceaccount/admin patched [kubeadm@server1 cm]$ kubectl describe sa admin Name: admin Namespace: default Labels: <none> Annotations: <none> Image pull secrets: myregistrykey Mountable secrets: admin-token-vlffb Tokens: admin-token-vlffb Events: <none>将认证信息添加到serviceAccount中，要比直接在Pod指定imagePullSecrets要安全很多。
在默认sa default中,可以这样设置
[kubeadm@server1 cm]$ vim pod.yml [kubeadm@server1 cm]$ cat pod.yml apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: game2048 image: reg.red.org/private/game2048 [kubeadm@server1 cm]$ kubectl patch serviceaccount default -p '{"imagePullSecrets": [{"name": "myregistrykey"}]}' serviceaccount/default patched [kubeadm@server1 cm]$ kubectl describe sa default Name: default Namespace: default Labels: <none> Annotations: <none> Image pull secrets: myregistrykey Mountable secrets: default-token-5qqxc Tokens: default-token-5qqxc Events: <none> [kubeadm@server1 cm]$ kubectl apply -f pod.yml pod/mypod created [kubeadm@server1 cm]$ kubectl get pod NAME READY STATUS RESTARTS AGE mypod 1/1 Running 0 4s[kubeadm@server1 pki]$ kubectl config set-credentials test --client-certificate=/etc/kubernetes/pki/test.crt --client-key=/etc/kubernetes/pki/test.key --embed-certs=true User "test" set. [kubeadm@server1 pki]$ kubectl config set-context test@kubernetes --cluster=kubernetes --user=test Context "test@kubernetes" created. [kubeadm@server1 pki]$ kubectl config view apiVersion: v1 clusters: - cluster: certificate-authority-data: DATA+OMITTED server: https://192.168.43.11:6443 name: kubernetes contexts: - context: cluster: kubernetes user: kubernetes-admin name: kubernetes-admin@kubernetes - context: cluster: kubernetes user: test name: test@kubernetes current-context: kubernetes-admin@kubernetes kind: Config preferences: {} users: - name: kubernetes-admin user: client-certificate-data: REDACTED client-key-data: REDACTED - name: test user: client-certificate-data: REDACTED client-key-data: REDACTED [kubeadm@server1 pki]$ kubectl config use-context test@kubernetes Switched to context "test@kubernetes". [kubeadm@server1 pki]$ kubectl get pod Error from server (Forbidden): pods is forbidden: User "test" cannot list resource "pods" in API group "" in the namespace "default"
RBAC（Role Based Access Control）：基于角色访问控制授权 • 允许管理员通过Kubernetes API动态配置授权策略。RBAC就是用户通过角色与权限进行关联。 • RBAC只有授权，没有拒绝授权，所以只需要定义允许该用户做什么即可。
• RBAC包括四种类型：Role、ClusterRole、RoleBinding、ClusterRoleBinding。 RBAC的三个基本概念： • Subject：被作用者，它表示k8s中的三类主体， user， group， serviceAccount • Role：角色，它其实是一组规则，定义了一组对 Kubernetes API 对象的操作权限。 • RoleBinding：定义了“被作用者”和“角色”的绑定关系。
Role 和 ClusterRole • Role是一系列的权限的集合，Role只能授予单个namespace 中资源的访问权限。 • ClusterRole 跟 Role 类似，但是可以在集群中全局使用。
RoleBinding是将Role中定义的权限授予给用户或用户组。它包含一个subjects 列表(users，groups service accounts)，并引用该Role。 • RoleBinding是对某个namespace 内授权，ClusterRoleBinding适用在集群范围内使用。
RoleBinding示例：
[kubeadm@server1 rbac]$ vim role.yml [kubeadm@server1 rbac]$ cat role.yml kind: Role apiVersion: rbac.authorization.k8s.io/v1 metadata: namespace: default name: myrole rules: - apiGroups: [""] resources: ["pods"] verbs: ["get", "watch", "list", "create", "update", "patch", "delete"] --- kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: test-read-pods namespace: default subjects: - kind: User name: test apiGroup: rbac.authorization.k8s.io roleRef: kind: Role name: myrole apiGroup: rbac.authorization.k8s.io [kubeadm@server1 rbac]$ kubectl apply -f role.yml role.rbac.authorization.k8s.io/myrole unchanged rolebinding.rbac.authorization.k8s.io/test-read-pods created [kubeadm@server1 rbac]$ kubectl config use-context admin@kubernetes error: no context exists with the name: "admin@kubernetes" [kubeadm@server1 rbac]$ kubectl config use-context test@kubernetes Switched to context "test@kubernetes". [kubeadm@server1 rbac]$ kubectl get pod NAME READY STATUS RESTARTS AGE nfs-client-provisioner-96649cd96-pntbp 1/1 Running 1 22h
== ClusterRole示例， 使用rolebinding绑定clusterRole==
[kubeadm@server1 rbac]$ vim role.yml [kubeadm@server1 rbac]$ kubectl config use-context kubernetes-admin@kubernetes Switched to context "kubernetes-admin@kubernetes". [kubeadm@server1 rbac]$ cat role.yml kind: Role apiVersion: rbac.authorization.k8s.io/v1 metadata: namespace: default name: myrole rules: - apiGroups: [""] resources: ["pods"] verbs: ["get", "watch", "list", "create", "update", "patch", "delete"] --- kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: test-read-pods namespace: default subjects: - kind: User name: test apiGroup: rbac.authorization.k8s.io roleRef: kind: Role name: myrole apiGroup: rbac.authorization.k8s.io --- kind: ClusterRole apiVersion: rbac.authorization.k8s.io/v1 metadata: name: myclusterrole rules: - apiGroups: [""] resources: ["pods"] verbs: ["get", "watch", "list", "delete", "create", "update"] - apiGroups: ["extensions", "apps"] resources: ["deployments"] verbs: ["get", "list", "watch", "create", "update", "patch", "delete"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: rolebind-myclusterrole namespace: default roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: myclusterrole subjects: - apiGroup: rbac.authorization.k8s.io kind: User name: test [kubeadm@server1 rbac]$ kubectl apply -f role.yml role.rbac.authorization.k8s.io/myrole unchanged rolebinding.rbac.authorization.k8s.io/test-read-pods unchanged clusterrole.rbac.authorization.k8s.io/myclusterrole created rolebinding.rbac.authorization.k8s.io/rolebind-myclusterrole created [kubeadm@server1 rbac]$ kubectl config use-context test@kubernetes Switched to context "test@kubernetes". [kubeadm@server1 rbac]$ cd ../mainfest/ [kubeadm@server1 mainfest]$ kubectl apply -f deployment.yml deployment.apps/deployment-myapp created [kubeadm@server1 mainfest]$ kubectl get pod NAME READY STATUS RESTARTS AGE deployment-myapp-7449b5b68f-hmmd2 1/1 Running 0 5s deployment-myapp-7449b5b68f-kvczp 1/1 Running 0 5s deployment-myapp-7449b5b68f-l8lkf 1/1 Running 0 5s deployment-myapp-7449b5b68f-ndxql 1/1 Running 0 5s nfs-client-provisioner-96649cd96-pntbp 1/1 Running 1 22h [kubeadm@server1 mainfest]$ kubectl get pod -n kube-system Error from server (Forbidden): pods is forbidden: User "test" cannot list resource "pods" in API group "" in the namespace "kube-system" [kubeadm@server1 mainfest]$ kubectl delete -f deploy error: the path "deploy" does not exist [kubeadm@server1 mainfest]$ kubectl delete -f deployment.yml deployment.apps "deployment-myapp" deleted
创建clusterrolebinding
[kubeadm@server1 rbac]$ cat role.yml kind: Role apiVersion: rbac.authorization.k8s.io/v1 metadata: namespace: default name: myrole rules: - apiGroups: [""] resources: ["pods"] verbs: ["get", "watch", "list", "create", "update", "patch", "delete"] --- kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: test-read-pods namespace: default subjects: - kind: User name: test apiGroup: rbac.authorization.k8s.io roleRef: kind: Role name: myrole apiGroup: rbac.authorization.k8s.io --- kind: ClusterRole apiVersion: rbac.authorization.k8s.io/v1 metadata: name: myclusterrole rules: - apiGroups: [""] resources: ["pods"] verbs: ["get", "watch", "list", "delete", "create", "update"] - apiGroups: ["extensions", "apps"] resources: ["deployments"] verbs: ["get", "list", "watch", "create", "update", "patch", "delete"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: rolebind-myclusterrole namespace: default roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: myclusterrole subjects: - apiGroup: rbac.authorization.k8s.io kind: User name: test --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: clusterrolebinding-myclusterrole roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: myclusterrole subjects: - apiGroup: rbac.authorization.k8s.io kind: User name: test [kubeadm@server1 rbac]$ kubectl apply -f role.yml role.rbac.authorization.k8s.io/myrole unchanged rolebinding.rbac.authorization.k8s.io/test-read-pods unchanged clusterrole.rbac.authorization.k8s.io/myclusterrole unchanged rolebinding.rbac.authorization.k8s.io/rolebind-myclusterrole unchanged clusterrolebinding.rbac.authorization.k8s.io/clusterrolebinding-myclusterrole created [kubeadm@server1 rbac]$ kubectl config use-context test@kubernetes Switched to context "test@kubernetes". [kubeadm@server1 rbac]$ kubectl config get-contexts CURRENT NAME CLUSTER AUTHINFO NAMESPACE kubernetes-admin@kubernetes kubernetes kubernetes-admin * test@kubernetes kubernetes test [kubeadm@server1 rbac]$ kubectl get pod -n kube-system NAME READY STATUS RESTARTS AGE coredns-698fcc7d7c-nsg7m 1/1 Running 1 23h coredns-698fcc7d7c-qp2ht 1/1 Running 1 22h etcd-server1 1/1 Running 11 15d kube-apiserver-server1 1/1 Running 12 15d kube-controller-manager-server1 1/1 Running 11 15d kube-flannel-ds-amd64-99khf 1/1 Running 2 23h kube-flannel-ds-amd64-gsszl 1/1 Running 6 7d21h kube-flannel-ds-amd64-p2mqf 1/1 Running 6 7d21h kube-proxy-4xlms 1/1 Running 14 8d kube-proxy-gx7jc 1/1 Running 14 8d kube-proxy-n58d5 1/1 Running 14 8d kube-scheduler-server1 1/1 Running 11 15d [kubeadm@server1 rbac]$ kubectl get namespaces Error from server (Forbidden): namespaces is forbidden: User "test" cannot list resource "namespaces" in API group "" at the cluster scope [kubeadm@server1 rbac]$ kubectl config use-context kubernetes-admin@kubernetes Switched to context "kubernetes-admin@kubernetes". [kubeadm@server1 rbac]$ kubectl get namespaces NAME STATUS AGE default Active 15d ingress-nginx Active 6d23h kube-node-lease Active 15d kube-public Active 15d kube-system Active 15d
服务账户准入控制器（Service account admission controller） • 如果该 pod 没有 ServiceAccount 设置，将其 ServiceAccount 设为 default。 • 保证 pod 所关联的 ServiceAccount 存在，否则拒绝该 pod。 • 如果 pod 不包含 ImagePullSecrets 设置，那么 将 ServiceAccount 中的 ImagePullSecrets 信息添加到 pod 中。 • 将一个包含用于 API 访问的 token 的 volume 添加到 pod 中。 • 将挂载于 /var/run/secrets/kubernetes.io/serviceaccount 的 volumeSource 添加到 pod 下的每个容器中。
Token 控制器（Token controller） • 检测服务账户的创建，并且创建相应的 Secret 以支持 API 访问。 • 检测服务账户的删除，并且删除所有相应的服务账户 Token Secret。 • 检测 Secret 的增加，保证相应的服务账户存在，如有需要，为 Secret 增加 token。 • 检测 Secret 的删除，如有需要，从相应的服务账户中移除引用。
服务账户控制器（Service account controller） • 服务账户管理器管理各命名空间下的服务账户，并且保证每个活跃的命名空间下存在 一个名为 “default” 的服务账户
Kubernetes 还拥有“用户组”（Group）的概念： • ServiceAccount对应内置“用户”的名字是： • system:serviceaccount:<ServiceAccount名字 > • 而用户组所对应的内置名字是： • system:serviceaccounts:<Namespace名字 >
示例1：表示mynamespace中的所有ServiceAccount
subjects: - kind: Group name: system:s= erviceaccounts:mynamespace apiGroup: rbac.authorization.k8s.io示例2：表示整个系统中的所有ServiceAccount
subjects: - kind: Group name: system:serviceaccounts apiGroup: rbac.authorization.k8s.ioKubernetes 还提供了四个预先定义好的 ClusterRole 来供用户直接使用： • cluster-amdin • admin • edit • view kubectl get clusterrole
[kubeadm@server1 rbac]$ kubectl describe clusterrole cluster-admin role.yml Name: cluster-admin Labels: kubernetes.io/bootstrapping=rbac-defaults Annotations: rbac.authorization.kubernetes.io/autoupdate: true PolicyRule: Resources Non-Resource URLs Resource Names Verbs --------- ----------------- -------------- ----- *.* [] [] [*] [*] [] [*] Error from server (NotFound): clusterroles.rbac.authorization.k8s.io "role.yml" not found