Kubernetes WebHook 入门 -- 入门案例: apiserver 接入 github

博客原文

k8s 集群配置

vip 地址: https://11.0.1.100:16443

介绍

Webhook就是一种HTTP回调，用于在某种情况下执行某些动作，Webhook不是K8S独有的，很多场景下都可以进行Webhook，比如在提交完代码后调用一个Webhook自动构建docker镜像

K8S中提供了自定义资源类型和自定义控制器来扩展功能，还提供了动态准入控制，其实就是通过Webhook来实现准入控制，分为两种：验证性质的准入 Webhook （Validating Admission Webhook） 和 修改性质的准入 Webhook （Mutating Admission Webhook）

Admission Webhook有哪些使用场景？如下

• 在资源持久化到ETCD之前进行修改（Mutating Webhook），比如增加init Container或者sidecar Container
• 在资源持久化到ETCD之前进行校验（Validating Webhook），不满足条件的资源直接拒绝并给出相应信息

现在非常火热的的 Service Mesh 应用istio就是通过 mutating webhooks 来自动将Envoy这个 sidecar 容器注入到 Pod 中去的：
https://istio.io/docs/setup/kubernetes/sidecar-injection/。

更多详情介绍可参考：
https://kubernetes.io/zh/docs/reference/access-authn-authz/extensible-admission-controllers/

Admission Webhook

上面提到K8S的动态准入控制是通过Webhook来实现的，那么它到底是在哪个环节执行的？请看下图

综上, k8s webhook 可分为两类:

1. Mutating Webhook: 这类 webhook 可以更改请求对象
2. Validating Webhook: 这类 webhook 不能去更改请求对象, 就算更改也会被忽略, 用于写入 etcd 前的验证逻辑

WebHook 入门实践: github 认证接入

源码地址: https://github.com/Ai-feier/k8s-webhook/tree/main/auth-github

写一个用于认证校验的 mutating webhook

请求流程:

1. 拦截 apiserver 请求
2. 将请求(TokenReview)中的 token 发送给 github 用于验证
3. 将 github 返回的用户信息填入 TokenReview

web 服务器

package mainimport ("context""encoding/json""github.com/google/go-github/github""golang.org/x/oauth2"authentication "k8s.io/api/authentication/v1beta1""log""net/http"
)func main() {http.HandleFunc("/authenticate", func(writer http.ResponseWriter, request *http.Request) {// 获取请求中的 TokonReviewdecoder := json.NewDecoder(request.Body)var tokenReview authentication.TokenReviewif err := decoder.Decode(&tokenReview); err != nil {log.Println("decode error: ", err)// 响应返回错误writer.WriteHeader(http.StatusBadRequest)_ = json.NewEncoder(writer).Encode(map[string]interface{}{"apiVersion": "authentication.k8s.io/v1beta1","kind":       "TokenReview","status": authentication.TokenReviewStatus{Authenticated: false,},})return}log.Println("receive request")// 检查用户// 创建 oauth2 对象, 发送给 githuboauthToken := oauth2.StaticTokenSource(&oauth2.Token{AccessToken: tokenReview.Spec.Token, // tokenReview 的 token})oauthClient := oauth2.NewClient(context.Background(), oauthToken)client := github.NewClient(oauthClient)user, _, err := client.Users.Get(context.Background(), "")if err != nil {log.Println("github auth error: ", err)writer.WriteHeader(http.StatusUnauthorized)_ = json.NewEncoder(writer).Encode(map[string]any{"apiVersion": "authentication.k8s.io/v1beta1","kind":       "TokenReview","status": authentication.TokenReviewStatus{Authenticated: false, // 返回认证失败},})return}// 认证成功log.Println("github login success, as: ", *user.Login)status := authentication.TokenReviewStatus{Authenticated: true,User: authentication.UserInfo{Username: *user.Login,UID: *user.Login,},}json.NewEncoder(writer).Encode(map[string]any{"apiVersion": "authentication.k8s.io/v1beta1","kind":       "TokenReview","status": status,})})log.Println(http.ListenAndServe(":3000", nil))
}

Dockerfile 镜像制作

本项目是使用 go 作为 web 服务器, go 提供一种非常好用的编译特性 – 交叉编译

在 dockerfile 中我们选择的 busybox 作为基础镜像, 但默认 busybox 架构为 x86_64(uname -m查看), 所以可以使用 amd64/busybox 或交叉编译 go 代码

当出现这类问题 exec /usr/bin/sh: exec format error 多半是架构问题

推荐: Golang交叉编译详解 – CSDN

amd64

FROM golang:1.20 as builderWORKDIR /appCOPY . .# go 交叉编译: amd64
RUN go env -w  GOPROXY=https://goproxy.cn,direct && go mod tidy && \CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o main main.go RUN chmod +x /app/mainFROM amd64/busyboxCOPY --from=builder /app/main .EXPOSE 3000/tcpCMD ["/main"]

x86_64

FROM golang:1.20 as builderWORKDIR /appCOPY . .# go 交叉编译: x86
RUN go env -w  GOPROXY=https://goproxy.cn,direct && go mod tidy && \CGO_ENABLED=0 GOOS=linux GOARCH=386 go build -o main main.go RUN chmod +x /app/mainFROM busyboxCOPY --from=builder /app/main .EXPOSE 3000/tcpCMD ["/main"]

构造镜像

$ docker build -t aifeierwithinmkt/auth-github-webhook:amd64 -f Dockerfile_amd64 .$ docker build -t aifeierwithinmkt/auth-github-webhook:x86 -f Dockerfile_x86 .$ docker tag aifeierwithinmkt/auth-github-webhook:amd64 aifeierwithinmkt/auth-github-webhook

检验镜像

$ docker run --rm -p 3000:3000 -d aifeierwithinmkt/auth-github-webhook:amd64
$ docker run --rm -p 3001:3000 -d aifeierwithinmkt/auth-github-webhook:x86$ curl 127.0.0.1:3000/authenticate
{"apiVersion":"authentication.k8s.io/v1beta1","kind":"TokenReview","status":{"user":{}}}
$ curl 127.0.0.1:3001/authenticate
{"apiVersion":"authentication.k8s.io/v1beta1","kind":"TokenReview","status":{"user":{}}}

镜像服务正常

Makefile

build_amd64:mkdir -p bin/amd64CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o bin/amd64/main .build_x86:mkdir -p bin/x86CGO_ENABLED=0 GOOS=linux GOARCH=386 go build -o bin/x86/main .	

webhook 接入 apiserver

webhook.yaml

apiVersion: v1
clusters:
- cluster:server: http://192.168.1.7:3000/authenticatename: github-authn
contexts:
- context:cluster: github-authnuser: authn-apiservername: webhook
current-context: webhook
kind: Config
preferences: {}
users:
- name: authn-apiserveruser:client-certificate-data: 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client-key-data: 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

该配置与 kubeconfig 配置相同, 直接在 kubeconfig 的基础上修改就行, 重要的是 cluster 的 server (即提供服务的地址

apiserver 挂载 webconfig

# 修改 apiserver 配置参数, 增加:
- --authentication-token-webhook-config-file=/etc/config/webhook.yaml# 相应增加挂载卷volumes:- hostPath:path: /etc/configtype: DirectoryOrCreatename: auth-webhookvolumeMounts:- mountPath: /etc/configname: auth-webhookreadOnly: true

1. 修改 manifest 后 apiserver 理论上会自动重启, 如果没有则 systemctl restart kubelet
2. 本文实验主题为认证 webhook 可直接使用 --authentication-token-webhook-config-file, 如需自定义 mutatingwebhook 请参考: mutatingwebhook

在 github 中创建认证 token

setting -> Developer Settings -> Personal access tokens (classic)

将 token 添加到 kubeconfig

# 在 kubeconfig 下增加一个 user
- name: githubuseruser:token: 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

验证

$ k get po --user githubuser
Error from server (Forbidden): pods is forbidden: User "Ai-feier" cannot list resource "pods" in API group "" in the namespace "default"

授权验证

$ k create clusterrolebinding testview --clusterrole view --user Ai-feier
$ k get po --user githubuser
NAME                         READY   STATUS    RESTARTS      AGE
nginx-kusc00401              0/1     Pending   0             4d23h
testnginx-5cdb847cd9-7nm4k   1/1     Running   1 (29h ago)   43h
testnginx-5cdb847cd9-llmxf   1/1     Running   1 (29h ago)   43h
testnginx-5cdb847cd9-qfsdn   1/1     Running   1 (29h ago)   43h
web-server                   0/1     Pending   0             4d22h

参考

1. https://kubernetes.io/zh-cn/docs/reference/access-authn-authz/extensible-admission-controllers/