## 前言 在上一篇[**APIServer-P3-APIServer的认证机制**](https://github.com/yinwenqin/kubeSourceCodeNote/blob/master/apiServer/Kubernetes%E6%BA%90%E7%A0%81%E5%AD%A6%E4%B9%A0-APIServer-P3-APIServer%E7%9A%84%E8%AE%A4%E8%AF%81%E6%9C%BA%E5%88%B6.md)中，讲述了请求进入后的认证过程，在通过认证之后，请求将进入鉴权环节，本篇就此展开。 ## 审查请求属性 Kubernetes 仅审查以下 API 请求属性： - **用户** - 身份验证期间提供的 `user` 字符串。 - **组** - 经过身份验证的用户所属的组名列表。 - **额外信息** - 由身份验证层提供的任意字符串键到字符串值的映射。 - **API** - 指示请求是否针对 API 资源。 - **请求路径** - 各种非资源端点的路径，如 `/api` 或 `/healthz`。 - **API 请求动词** - API 动词 `get`、`list`、`create`、`update`、`patch`、`watch`、 `proxy`、`redirect`、`delete` 和 `deletecollection` 用于资源请求。 要确定资源 API 端点的请求动词，请参阅 [确定请求动词](https://kubernetes.io/zh/docs/reference/access-authn-authz/authorization/#determine-the-request-verb)。 - **HTTP 请求动词** - HTTP 动词 `get`、`post`、`put` 和 `delete` 用于非资源请求。 - **Resource** - 正在访问的资源的 ID 或名称（仅限资源请求）- 对于使用 `get`、`update`、`patch` 和 `delete` 动词的资源请求，你必须提供资源名称。 - **子资源** - 正在访问的子资源（仅限资源请求）。 - **名字空间** - 正在访问的对象的名称空间（仅适用于名字空间资源请求）。 - **API 组** - 正在访问的 [API 组](https://kubernetes.io/zh/docs/concepts/overview/kubernetes-api/#api-groups) （仅限资源请求）。空字符串表示[核心 API 组](https://kubernetes.io/zh/docs/reference/using-api/#api-groups) ## 鉴权的描述 ### 鉴权策略分类 目前支持6种鉴权策略，每种鉴权策略对应一个鉴权器，使用的鉴权策略需要在APIServer启动时以参数`--authorization-mode`的形式指定，多种策略同时指定时使用','号连接： 策略分类有： - `--authorization-mode=ABAC` 基于属性的访问控制（ABAC）模式允许你 使用本地文件配置策略。 - `--authorization-mode=RBAC` 基于角色的访问控制（RBAC）模式允许你使用 Kubernetes API 创建和存储策略。 - `--authorization-mode=Webhook` WebHook 是一种 HTTP 回调模式，允许你使用远程 REST 端点管理鉴权。 - `--authorization-mode=Node` 节点鉴权是一种特殊用途的鉴权模式，专门对 kubelet 发出的 API 请求执行鉴权。 - `--authorization-mode=AlwaysDeny` 该标志阻止所有请求。仅将此标志用于测试。 - `--authorization-mode=AlwaysAllow` 此标志允许所有请求。仅在你不需要 API 请求 的鉴权时才使用此标志。 与上一篇的认证模块不同的是，当配置多个鉴权模块时，鉴权模块按**顺序**检查，靠前的模块具有更高的优先级来允许或拒绝请求。 来看看现有的kubeadm部署集群启用的鉴权策略: ![](https://mycloudn.upweto.top/20210203155452.png) 可以看到，默认启用了Node授权和RBAC授权模块。 ### 鉴权结果 对于每一个请求的鉴权结果，有专门为其设计的健全结果描述结构体，如下: `vendor/k8s.io/apiserver/pkg/authorization/authorizer/interfaces.go:148` ```go type Decision int const ( // 拒绝 DecisionDeny Decision = iota // 允许，则鉴权流程视为成功，请求顺利进入 DecisionAllow // 无操作，进入下一个鉴权模块，相当于pass DecisionNoOpinion ) ``` ### 鉴权接口方法 `vendor/k8s.io/apiserver/pkg/authorization/authorizer/interfaces.go:69` ```go // Authorizer makes an authorization decision based on information gained by making // zero or more calls to methods of the Attributes interface. It returns nil when an action is // authorized, otherwise it returns an error. type Authorizer interface { Authorize(a Attributes) (authorized Decision, reason string, err error) } ``` 所有的鉴权模块(鉴权器)都要实现这个`Authorize`方法,返回鉴权结果。 ### 规则解析器 规则解析器可以根据认证之后所得到的用户信息，获取该用户对应的资源对象的操作权限。 ```go // RuleResolver provides a mechanism for resolving the list of rules that apply to a given user within a namespace. type RuleResolver interface { // RulesFor get the list of cluster wide rules, the list of rules in the specific namespace, incomplete status and errors. RulesFor(user user.Info, namespace string) ([]ResourceRuleInfo, []NonResourceRuleInfo, bool, error) } ``` 以这里的返回值类型`ResourceRuleInfo`为例，默认的`DefaultResourceRuleInfo`结构体是这样的: `vendor/k8s.io/apiserver/pkg/authorization/authorizer/rule.go:31` ```go // DefaultResourceRuleInfo holds information that describes a rule for the resource type DefaultResourceRuleInfo struct { Verbs []string APIGroups []string Resources []string ResourceNames []string } ``` 例如对pod资源的任意操作权限的描述可以描述为: ```go DefaultResourceRuleInfo{ Verbs []string{"*"} APIGroups []string{"*"} Resources []string{"pod"} } ``` 这个DefaultResourceRuleInfo对象描述的规则是，允许对所有api group 的pod资源进行的所有类型的操作，包括{"get", "list", "update", "patch","create", "delete", "watch", "deletecollection"}操作。 ### 鉴权流程图 ![](https://mycloudn.upweto.top/20210203180748.png) ## 鉴权器 `AlwaysAllow`和`AlwaysDeny`这两种鉴权器很少使用，就不看了，直接略过. ### ABAC鉴权器 #### 简介 基于属性的访问控制（Attribute-based access control - ABAC）定义了访问控制范例，其中通过使用将属性组合在一起的策略来向用户授予访问权限。 启用ABAC鉴权器需要额外增加一个`--authorization-policy-file=SOME_FILENAME`参数，指定一个json格式的文件预设鉴权策略，是一种静态的权限配置方式。json格式样例如下： ```json // 授予pod资源的任意操作权限给用户podManager { "apiVersion":"abac.authorization.kubernetes.io/v1beta1", "kind":"Policy", "spec":{ "user":"podManager", "namespace":"*", "resource":"pods", "readonly":true } } ``` #### 代码实现 `pkg/auth/authorizer/abac/abac.go:224` ```go // Authorizer implements authorizer.Authorize func (pl policyList) Authorize(a authorizer.Attributes) (authorizer.Decision, string, error) { for _, p := range pl { if matches(*p, a) { return authorizer.DecisionAllow, "", nil } } return authorizer.DecisionNoOpinion, "No policy matched.", nil } ``` --> `pkg/auth/authorizer/abac/abac.go:117` ```go func matches(p abac.Policy, a authorizer.Attributes) bool { if subjectMatches(p, a.GetUser()) { // 操作类型与规则匹配 if verbMatches(p, a) { // Resource and non-resource requests are mutually exclusive, at most one will match a policy // 资源类型与规则匹配(包含namespace/APIGroup/Resource) if resourceMatches(p, a) { return true } // 针对非资源对象的操作匹配(请求路径匹配) if nonResourceMatches(p, a) { return true } } } return false } ``` ### RBAC鉴权器 #### 简介 基于角色（Role）的访问控制（RBAC）是一种基于组织中用户的角色来调节控制对 计算机或网络资源的访问的方法。 RBAC 鉴权机制使用 `rbac.authorization.k8s.io` [API 组](https://kubernetes.io/zh/docs/concepts/overview/kubernetes-api/#api-groups) 来驱动鉴权决定，允许你通过 Kubernetes API 动态配置策略。 通过创建`Role` 或` ClusterRole`来描述具体的资源授权策略，再通过创建RoleBinding/ClusterRoleBinding将策略绑定到用户/群组/服务上。 RBAC模式的详细描述和使用样例请参考我之前的文章： [k8s(十四)、RBAC权限控制](https://blog.upweto.top/2018/12/06/k8s(%E5%8D%81%E5%9B%9B)%E3%80%81RBAC%E6%9D%83%E9%99%90%E6%8E%A7%E5%88%B6.html) #### 代码实现 `plugin/pkg/auth/authorizer/rbac/rbac.go:74` ```go func (r *RBACAuthorizer) Authorize(requestAttributes authorizer.Attributes) (authorizer.Decision, string, error) { ruleCheckingVisitor := &authorizingVisitor{requestAttributes: requestAttributes} // 规则解析器解析请求的属性，返回鉴权结果，判断匹配用的是ruleCheckingVisitor.visit方法 r.authorizationRuleResolver.VisitRulesFor(requestAttributes.GetUser(), requestAttributes.GetNamespace(), ruleCheckingVisitor.visit) if ruleCheckingVisitor.allowed { return authorizer.DecisionAllow, ruleCheckingVisitor.reason, nil } ... reason := "" if len(ruleCheckingVisitor.errors) > 0 { reason = fmt.Sprintf("RBAC: %v", utilerrors.NewAggregate(ruleCheckingVisitor.errors)) } return authorizer.DecisionNoOpinion, reason, nil } ``` 对比规则和请求属性，返回true or false的visit方法： `plugin/pkg/auth/authorizer/rbac/rbac.go:62` ```go func (v *authorizingVisitor) visit(source fmt.Stringer, rule *rbacv1.PolicyRule, err error) bool { if rule != nil && RuleAllows(v.requestAttributes, rule) { // 请求与规则匹配，则鉴权成功 v.allowed = true v.reason = fmt.Sprintf("RBAC: allowed by %s", source.String()) // 返回false是为了提前break鉴权过程 return false } if err != nil { v.errors = append(v.errors, err) } return true } ``` 获取规则并调用visit方法的是`VisitRulesFor`接口方法，找一下`VisitRulesFor`方法: `pkg/registry/rbac/validation/rule.go:178` ```go func (r *DefaultRuleResolver) VisitRulesFor(user user.Info, namespace string, visitor func(source fmt.Stringer, rule *rbacv1.PolicyRule, err error) bool) { // 先拿到所有的ClusterRoleBinding对象，ClusterRoleBinding资源是cluster级别的，不区分命名空间 if clusterRoleBindings, err := r.clusterRoleBindingLister.ListClusterRoleBindings(); err != nil { if !visitor(nil, nil, err) { return } } else { sourceDescriber := &clusterRoleBindingDescriber{} for _, clusterRoleBinding := range clusterRoleBindings { // clusterRoleBinding.Subjects指定的绑定的用户对象，对比请求的所属用户，不匹配则continue subjectIndex, applies := appliesTo(user, clusterRoleBinding.Subjects, "") if !applies { continue } rules, err := r.GetRoleReferenceRules(clusterRoleBinding.RoleRef, "") if err != nil { if !visitor(nil, nil, err) { return } continue } sourceDescriber.binding = clusterRoleBinding sourceDescriber.subject = &clusterRoleBinding.Subjects[subjectIndex] for i := range rules { // visit方法返回false是代表鉴权成功了，提前break鉴权过程 if !visitor(sourceDescriber, &rules[i], nil) { return } } } } // 如果指定了namespace，再取命名空间级别的roleBinding资源对象，重复一次上面的过程 if len(namespace) > 0 { if roleBindings, err := r.roleBindingLister.ListRoleBindings(namespace); err != nil { if !visitor(nil, nil, err) { return } } else { sourceDescriber := &roleBindingDescriber{} for _, roleBinding := range roleBindings { subjectIndex, applies := appliesTo(user, roleBinding.Subjects, namespace) if !applies { continue } rules, err := r.GetRoleReferenceRules(roleBinding.RoleRef, namespace) if err != nil { if !visitor(nil, nil, err) { return } continue } sourceDescriber.binding = roleBinding sourceDescriber.subject = &roleBinding.Subjects[subjectIndex] for i := range rules { if !visitor(sourceDescriber, &rules[i], nil) { return } } } } } } ``` #### 过程总结 参考代码片中的注释，rbac鉴权过程如下: - 1.取到所有的clusterRoleBinding/roleBindings资源对象，遍历它们对比请求用户 - 2.对比roleBindings/clusterRoleBinding指向的用户(主体)与请求用户，相同则选中，不相同continue - 3.对比规则与请求属性，符合则提前结束鉴权 ### Node鉴权器 上面有提过，node鉴权器是专为kubelet组件设计的，按照kubeadm集群的默认配置，它是排序在第一位的鉴权器，为什么把它放在后面再讲呢，因为node鉴权器本质上也是利用了rbac鉴权器，是通过为`system:node`这个内置用户授权来实现的，来看一下。 #### 默认Node规则生成 `plugin/pkg/auth/authorizer/rbac/bootstrappolicy/policy.go:97` ```go func NodeRules() []rbacv1.PolicyRule { nodePolicyRules := []rbacv1.PolicyRule{ // Needed to check API access. These creates are non-mutating rbacv1helpers.NewRule("create").Groups(authenticationGroup).Resources("tokenreviews").RuleOrDie(), rbacv1helpers.NewRule("create").Groups(authorizationGroup).Resources("subjectaccessreviews", "localsubjectaccessreviews").RuleOrDie(), // Needed to build serviceLister, to populate env vars for services rbacv1helpers.NewRule(Read...).Groups(legacyGroup).Resources("services").RuleOrDie(), // Nodes can register Node API objects and report status. // Use the NodeRestriction admission plugin to limit a node to creating/updating its own API object. rbacv1helpers.NewRule("create", "get", "list", "watch").Groups(legacyGroup).Resources("nodes").RuleOrDie(), rbacv1helpers.NewRule("update", "patch").Groups(legacyGroup).Resources("nodes/status").RuleOrDie(), rbacv1helpers.NewRule("update", "patch").Groups(legacyGroup).Resources("nodes").RuleOrDie(), // TODO: restrict to the bound node as creator in the NodeRestrictions admission plugin rbacv1helpers.NewRule("create", "update", "patch").Groups(legacyGroup).Resources("events").RuleOrDie(), // TODO: restrict to pods scheduled on the bound node once field selectors are supported by list/watch authorization rbacv1helpers.NewRule(Read...).Groups(legacyGroup).Resources("pods").RuleOrDie(), // Needed for the node to create/delete mirror pods. // Use the NodeRestriction admission plugin to limit a node to creating/deleting mirror pods bound to itself. rbacv1helpers.NewRule("create", "delete").Groups(legacyGroup).Resources("pods").RuleOrDie(), // Needed for the node to report status of pods it is running. // Use the NodeRestriction admission plugin to limit a node to updating status of pods bound to itself. rbacv1helpers.NewRule("update", "patch").Groups(legacyGroup).Resources("pods/status").RuleOrDie(), // Needed for the node to create pod evictions. // Use the NodeRestriction admission plugin to limit a node to creating evictions for pods bound to itself. rbacv1helpers.NewRule("create").Groups(legacyGroup).Resources("pods/eviction").RuleOrDie(), // Needed for imagepullsecrets, rbd/ceph and secret volumes, and secrets in envs // Needed for configmap volume and envs // Use the Node authorization mode to limit a node to get secrets/configmaps referenced by pods bound to itself. rbacv1helpers.NewRule("get", "list", "watch").Groups(legacyGroup).Resources("secrets", "configmaps").RuleOrDie(), // Needed for persistent volumes // Use the Node authorization mode to limit a node to get pv/pvc objects referenced by pods bound to itself. rbacv1helpers.NewRule("get").Groups(legacyGroup).Resources("persistentvolumeclaims", "persistentvolumes").RuleOrDie(), // TODO: add to the Node authorizer and restrict to endpoints referenced by pods or PVs bound to the node // Needed for glusterfs volumes rbacv1helpers.NewRule("get").Groups(legacyGroup).Resources("endpoints").RuleOrDie(), // Used to create a certificatesigningrequest for a node-specific client certificate, and watch // for it to be signed. This allows the kubelet to rotate it's own certificate. rbacv1helpers.NewRule("create", "get", "list", "watch").Groups(certificatesGroup).Resources("certificatesigningrequests").RuleOrDie(), } if utilfeature.DefaultFeatureGate.Enabled(features.ExpandPersistentVolumes) { // Use the Node authorization mode to limit a node to update status of pvc objects referenced by pods bound to itself. // Use the NodeRestriction admission plugin to limit a node to just update the status stanza. pvcStatusPolicyRule := rbacv1helpers.NewRule("get", "update", "patch").Groups(legacyGroup).Resources("persistentvolumeclaims/status").RuleOrDie() nodePolicyRules = append(nodePolicyRules, pvcStatusPolicyRule) } if utilfeature.DefaultFeatureGate.Enabled(features.TokenRequest) { // Use the Node authorization to limit a node to create tokens for service accounts running on that node // Use the NodeRestriction admission plugin to limit a node to create tokens bound to pods on that node tokenRequestRule := rbacv1helpers.NewRule("create").Groups(legacyGroup).Resources("serviceaccounts/token").RuleOrDie() nodePolicyRules = append(nodePolicyRules, tokenRequestRule) } // CSI if utilfeature.DefaultFeatureGate.Enabled(features.CSIPersistentVolume) { volAttachRule := rbacv1helpers.NewRule("get").Groups(storageGroup).Resources("volumeattachments").RuleOrDie() nodePolicyRules = append(nodePolicyRules, volAttachRule) if utilfeature.DefaultFeatureGate.Enabled(features.CSIDriverRegistry) { csiDriverRule := rbacv1helpers.NewRule("get", "watch", "list").Groups("storage.k8s.io").Resources("csidrivers").RuleOrDie() nodePolicyRules = append(nodePolicyRules, csiDriverRule) } } if utilfeature.DefaultFeatureGate.Enabled(features.KubeletPluginsWatcher) && utilfeature.DefaultFeatureGate.Enabled(features.CSINodeInfo) { csiNodeInfoRule := rbacv1helpers.NewRule("get", "create", "update", "patch", "delete").Groups("storage.k8s.io").Resources("csinodes").RuleOrDie() nodePolicyRules = append(nodePolicyRules, csiNodeInfoRule) } // Node leases if utilfeature.DefaultFeatureGate.Enabled(features.NodeLease) { nodePolicyRules = append(nodePolicyRules, rbacv1helpers.NewRule("get", "create", "update", "patch", "delete").Groups("coordination.k8s.io").Resources("leases").RuleOrDie()) } // RuntimeClass if utilfeature.DefaultFeatureGate.Enabled(features.RuntimeClass) { nodePolicyRules = append(nodePolicyRules, rbacv1helpers.NewRule("get", "list", "watch").Groups("node.k8s.io").Resources("runtimeclasses").RuleOrDie()) } return nodePolicyRules } ``` 这里初始化了kubelet工作所需要的资源的权限，如(node/pod/cm/secret/pvc等) #### Authorize代码实现 `plugin/pkg/auth/authorizer/node/node_authorizer.go:80` ```go func (r *NodeAuthorizer) Authorize(attrs authorizer.Attributes) (authorizer.Decision, string, error) { // 判断是不是node发起的请求(所属的group是不是system:node) nodeName, isNode := r.identifier.NodeIdentity(attrs.GetUser()) if !isNode { // reject requests from non-nodes return authorizer.DecisionNoOpinion, "", nil } if len(nodeName) == 0 { // reject requests from unidentifiable nodes klog.V(2).Infof("NODE DENY: unknown node for user %q", attrs.GetUser().GetName()) return authorizer.DecisionNoOpinion, fmt.Sprintf("unknown node for user %q", attrs.GetUser().GetName()), nil } // subdivide access to specific resources if attrs.IsResourceRequest() { // 根据请求属性(路径)获取资源类型，不同类型资源不同的方式处理 requestResource := schema.GroupResource{Group: attrs.GetAPIGroup(), Resource: attrs.GetResource()} switch requestResource { case secretResource: return r.authorizeReadNamespacedObject(nodeName, secretVertexType, attrs) case configMapResource: return r.authorizeReadNamespacedObject(nodeName, configMapVertexType, attrs) case pvcResource: if r.features.Enabled(features.ExpandPersistentVolumes) { if attrs.GetSubresource() == "status" { return r.authorizeStatusUpdate(nodeName, pvcVertexType, attrs) } } return r.authorizeGet(nodeName, pvcVertexType, attrs) case pvResource: return r.authorizeGet(nodeName, pvVertexType, attrs) case vaResource: if r.features.Enabled(features.CSIPersistentVolume) { return r.authorizeGet(nodeName, vaVertexType, attrs) } return authorizer.DecisionNoOpinion, fmt.Sprintf("disabled by feature gate %s", features.CSIPersistentVolume), nil case svcAcctResource: if r.features.Enabled(features.TokenRequest) { return r.authorizeCreateToken(nodeName, serviceAccountVertexType, attrs) } return authorizer.DecisionNoOpinion, fmt.Sprintf("disabled by feature gate %s", features.TokenRequest), nil case leaseResource: if r.features.Enabled(features.NodeLease) { return r.authorizeLease(nodeName, attrs) } return authorizer.DecisionNoOpinion, fmt.Sprintf("disabled by feature gate %s", features.NodeLease), nil case csiNodeResource: if r.features.Enabled(features.KubeletPluginsWatcher) && r.features.Enabled(features.CSINodeInfo) { return r.authorizeCSINode(nodeName, attrs) } return authorizer.DecisionNoOpinion, fmt.Sprintf("disabled by feature gates %s and %s", features.KubeletPluginsWatcher, features.CSINodeInfo), nil } } // Access to other resources is not subdivided, so just evaluate against the statically defined node rules if rbac.RulesAllow(attrs, r.nodeRules...) { return authorizer.DecisionAllow, "", nil } return authorizer.DecisionNoOpinion, "", nil } ``` ### WebHook鉴权器 #### 简介 与上一篇中的WebHook认证器类似，WebHook鉴权器也是依赖于集群外部的鉴权服务器，将鉴权请求POST发送给外部的鉴权服务器。 `Webhook` 模式需要一个 HTTP 配置文件，通过 `--authorization-webhook-config-file=SOME_FILENAME` 的参数声明。 配置文件的格式使用 [kubeconfig](https://kubernetes.io/zh/docs/tasks/access-application-cluster/configure-access-multiple-clusters/)。在文件中，"users" 代表着 API 服务器的 webhook，而 "cluster" 代表着远程服务。 使用 HTTPS 客户端认证的配置例子： ```yaml # Kubernetes API 版本 apiVersion: v1 # API 对象种类 kind: Config # clusters 代表远程服务。 clusters: - name: name-of-remote-authz-service cluster: # 对远程服务进行身份认证的 CA。 certificate-authority: /path/to/ca.pem # 远程服务的查询 URL。必须使用 'https'。 server: https://authz.example.com/authorize # users 代表 API 服务器的 webhook 配置 users: - name: name-of-api-server user: client-certificate: /path/to/cert.pem # webhook plugin 使用 cert client-key: /path/to/key.pem # cert 所对应的 key # kubeconfig 文件必须有 context。需要提供一个给 API 服务器。 current-context: webhook contexts: - context: cluster: name-of-remote-authz-service user: name-of-api-server name: webhook ``` > 摘自官方文档[Webhook 模式](https://kubernetes.io/zh/docs/reference/access-authn-authz/webhook/) #### 代码实现 `vendor/k8s.io/apiserver/plugin/pkg/authorizer/webhook/webhook.go:152` ```go func (w *WebhookAuthorizer) Authorize(attr authorizer.Attributes) (decision authorizer.Decision, reason string, err error) { r := &authorization.SubjectAccessReview{} if user := attr.GetUser(); user != nil { r.Spec = authorization.SubjectAccessReviewSpec{ User: user.GetName(), UID: user.GetUID(), Groups: user.GetGroups(), Extra: convertToSARExtra(user.GetExtra()), } } if attr.IsResourceRequest() { r.Spec.ResourceAttributes = &authorization.ResourceAttributes{ Namespace: attr.GetNamespace(), Verb: attr.GetVerb(), Group: attr.GetAPIGroup(), Version: attr.GetAPIVersion(), Resource: attr.GetResource(), Subresource: attr.GetSubresource(), Name: attr.GetName(), } } else { r.Spec.NonResourceAttributes = &authorization.NonResourceAttributes{ Path: attr.GetPath(), Verb: attr.GetVerb(), } } // 将请求的主体/资源/操作等字段放在一个json里 key, err := json.Marshal(r.Spec) if err != nil { return w.decisionOnError, "", err } // 从本地的缓存里取，有则不发起远端post请求了 if entry, ok := w.responseCache.Get(string(key)); ok { r.Status = entry.(authorization.SubjectAccessReviewStatus) } else { var ( result *authorization.SubjectAccessReview err error ) webhook.WithExponentialBackoff(w.initialBackoff, func() error { // 缓存里没有，则发起post请求给远端鉴权服务器 result, err = w.subjectAccessReview.Create(r) return err }) if err != nil { // An error here indicates bad configuration or an outage. Log for debugging. klog.Errorf("Failed to make webhook authorizer request: %v", err) return w.decisionOnError, "", err } r.Status = result.Status // 长度不超过10000则缓存结果 if shouldCache(attr) { if r.Status.Allowed { w.responseCache.Add(string(key), r.Status, w.authorizedTTL) } else { w.responseCache.Add(string(key), r.Status, w.unauthorizedTTL) } } } switch { // 根据远端鉴权服务器的响应状态，返回鉴权结果 case r.Status.Denied && r.Status.Allowed: return authorizer.DecisionDeny, r.Status.Reason, fmt.Errorf("webhook subject access review returned both allow and deny response") case r.Status.Denied: return authorizer.DecisionDeny, r.Status.Reason, nil case r.Status.Allowed: return authorizer.DecisionAllow, r.Status.Reason, nil default: return authorizer.DecisionNoOpinion, r.Status.Reason, nil } } ``` ## 总结 鉴权的流程与认证的流程大体类似，但也有所不同，例如认证器链的执行顺序是无序的，而鉴权器链的执行顺序是有序的(按参数指定的顺序)。另外鉴权器的数量没有认证器那么多，因此相对容易理解一些。