362 lines
11 KiB
Markdown
362 lines
11 KiB
Markdown
# 创建 kubernetes 各组件 TLS 加密通信的证书和秘钥
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`kubernetes` 系统的各组件需要使用 `TLS` 证书对通信进行加密，本文档使用 `CloudFlare` 的 PKI 工具集 [cfssl](https://github.com/cloudflare/cfssl) 来生成 Certificate Authority (CA) 和其它证书；
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**生成的 CA 证书和秘钥文件如下：**
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+ ca-key.pem
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+ ca.pem
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+ kubernetes-key.pem
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+ kubernetes.pem
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+ kube-proxy.pem
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+ kube-proxy-key.pem
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+ admin.pem
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+ admin-key.pem
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**使用证书的组件如下：**
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+ etcd：使用 ca.pem、kubernetes-key.pem、kubernetes.pem；
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+ kube-apiserver：使用 ca.pem、kubernetes-key.pem、kubernetes.pem；
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+ kubelet：使用 ca.pem；
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+ kube-proxy：使用 ca.pem、kube-proxy-key.pem、kube-proxy.pem；
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+ kubectl：使用 ca.pem、admin-key.pem、admin.pem；
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`kube-controller`、`kube-scheduler` 当前需要和 `kube-apiserver` 部署在同一台机器上且使用非安全端口通信，故不需要证书。
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## 安装 `CFSSL`
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**方式一：直接使用二进制源码包安装**
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``` bash
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$ wget https://pkg.cfssl.org/R1.2/cfssl_linux-amd64
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$ chmod +x cfssl_linux-amd64
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$ sudo mv cfssl_linux-amd64 /root/local/bin/cfssl
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$ wget https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64
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$ chmod +x cfssljson_linux-amd64
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$ sudo mv cfssljson_linux-amd64 /root/local/bin/cfssljson
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$ wget https://pkg.cfssl.org/R1.2/cfssl-certinfo_linux-amd64
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$ chmod +x cfssl-certinfo_linux-amd64
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$ sudo mv cfssl-certinfo_linux-amd64 /root/local/bin/cfssl-certinfo
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$ export PATH=/root/local/bin:$PATH
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```
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**方式二：使用go命令安装**
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我们的系统中安装了Go1.7.5，使用以下命令安装更快捷：
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```
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$go get -u github.com/cloudflare/cfssl/cmd/...
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$echo $GOPATH
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/usr/local
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$ls /usr/local/bin/cfssl*
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cfssl cfssl-bundle cfssl-certinfo cfssljson cfssl-newkey cfssl-scan
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```
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在`$GOPATH/bin`目录下得到以cfssl开头的几个命令。
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## 创建 CA (Certificate Authority)
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**创建 CA 配置文件**
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``` bash
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$ mkdir /root/ssl
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$ cd /root/ssl
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$ cfssl print-defaults config > config.json
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$ cfssl print-defaults csr > csr.json
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$ cat ca-config.json
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{
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"signing": {
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"default": {
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"expiry": "8760h"
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},
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"profiles": {
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"kubernetes": {
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"usages": [
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"signing",
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"key encipherment",
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"server auth",
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"client auth"
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],
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"expiry": "8760h"
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}
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}
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}
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}
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```
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字段说明
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+ `ca-config.json`：可以定义多个 profiles，分别指定不同的过期时间、使用场景等参数；后续在签名证书时使用某个 profile；
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+ `signing`：表示该证书可用于签名其它证书；生成的 ca.pem 证书中 `CA=TRUE`；
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+ `server auth`：表示client可以用该 CA 对server提供的证书进行验证；
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+ `client auth`：表示server可以用该CA对client提供的证书进行验证；
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**创建 CA 证书签名请求**
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``` bash
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$ cat ca-csr.json
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{
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"CN": "kubernetes",
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"key": {
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"algo": "rsa",
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"size": 2048
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},
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"names": [
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{
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"C": "CN",
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"ST": "BeiJing",
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"L": "BeiJing",
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"O": "k8s",
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"OU": "System"
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}
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]
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}
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```
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+ "CN"：`Common Name`，kube-apiserver 从证书中提取该字段作为请求的用户名 (User Name)；浏览器使用该字段验证网站是否合法；
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+ "O"：`Organization`，kube-apiserver 从证书中提取该字段作为请求用户所属的组 (Group)；
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**生成 CA 证书和私钥**
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``` bash
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$ cfssl gencert -initca ca-csr.json | cfssljson -bare ca
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$ ls ca*
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ca-config.json ca.csr ca-csr.json ca-key.pem ca.pem
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```
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## 创建 kubernetes 证书
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创建 kubernetes 证书签名请求
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``` bash
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$ cat kubernetes-csr.json
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{
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"CN": "kubernetes",
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"hosts": [
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"127.0.0.1",
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"172.20.0.112",
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"172.20.0.113",
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"172.20.0.114",
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"172.20.0.115",
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"10.254.0.1",
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"kubernetes",
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"kubernetes.default",
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"kubernetes.default.svc",
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"kubernetes.default.svc.cluster",
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"kubernetes.default.svc.cluster.local"
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],
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"key": {
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"algo": "rsa",
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"size": 2048
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},
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"names": [
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{
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"C": "CN",
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"ST": "BeiJing",
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"L": "BeiJing",
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"O": "k8s",
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"OU": "System"
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}
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]
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}
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```
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+ 如果 hosts 字段不为空则需要指定授权使用该证书的 **IP 或域名列表**，由于该证书后续被 `etcd` 集群和 `kubernetes master` 集群使用，所以上面分别指定了 `etcd` 集群、`kubernetes master` 集群的主机 IP 和 **`kubernetes` 服务的服务 IP**（一般是 `kue-apiserver` 指定的 `service-cluster-ip-range` 网段的第一个IP，如 10.254.0.1。
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**生成 kubernetes 证书和私钥**
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``` bash
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$ cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=kubernetes kubernetes-csr.json | cfssljson -bare kubernetes
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$ ls kuberntes*
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kubernetes.csr kubernetes-csr.json kubernetes-key.pem kubernetes.pem
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```
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或者直接在命令行上指定相关参数：
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``` bash
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$ echo '{"CN":"kubernetes","hosts":[""],"key":{"algo":"rsa","size":2048}}' | cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=kubernetes -hostname="127.0.0.1,172.20.0.112,172.20.0.113,172.20.0.114,172.20.0.115,kubernetes,kubernetes.default" - | cfssljson -bare kubernetes
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```
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## 创建 admin 证书
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创建 admin 证书签名请求
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``` bash
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$ cat admin-csr.json
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{
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"CN": "admin",
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"hosts": [],
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"key": {
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"algo": "rsa",
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"size": 2048
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},
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"names": [
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{
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"C": "CN",
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"ST": "BeiJing",
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"L": "BeiJing",
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"O": "system:masters",
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"OU": "System"
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}
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]
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}
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```
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+ 后续 `kube-apiserver` 使用 `RBAC` 对客户端(如 `kubelet`、`kube-proxy`、`Pod`)请求进行授权；
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+ `kube-apiserver` 预定义了一些 `RBAC` 使用的 `RoleBindings`，如 `cluster-admin` 将 Group `system:masters` 与 Role `cluster-admin` 绑定，该 Role 授予了调用`kube-apiserver` 的**所有 API**的权限；
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+ OU 指定该证书的 Group 为 `system:masters`，`kubelet` 使用该证书访问 `kube-apiserver` 时 ，由于证书被 CA 签名，所以认证通过，同时由于证书用户组为经过预授权的 `system:masters`，所以被授予访问所有 API 的权限；
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生成 admin 证书和私钥
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``` bash
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$ cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=kubernetes admin-csr.json | cfssljson -bare admin
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$ ls admin*
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admin.csr admin-csr.json admin-key.pem admin.pem
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```
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## 创建 kube-proxy 证书
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创建 kube-proxy 证书签名请求
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``` bash
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$ cat kube-proxy-csr.json
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{
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"CN": "system:kube-proxy",
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"hosts": [],
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"key": {
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"algo": "rsa",
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"size": 2048
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},
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"names": [
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{
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"C": "CN",
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"ST": "BeiJing",
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"L": "BeiJing",
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"O": "k8s",
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"OU": "System"
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}
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]
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}
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```
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+ CN 指定该证书的 User 为 `system:kube-proxy`；
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+ `kube-apiserver` 预定义的 RoleBinding `cluster-admin` 将User `system:kube-proxy` 与 Role `system:node-proxier` 绑定，该 Role 授予了调用 `kube-apiserver` Proxy 相关 API 的权限；
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生成 kube-proxy 客户端证书和私钥
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``` bash
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$ cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=kubernetes kube-proxy-csr.json | cfssljson -bare kube-proxy
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$ ls kube-proxy*
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kube-proxy.csr kube-proxy-csr.json kube-proxy-key.pem kube-proxy.pem
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```
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## 校验证书
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以 kubernetes 证书为例
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### 使用 `opsnssl` 命令
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``` bash
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$ openssl x509 -noout -text -in kubernetes.pem
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...
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Signature Algorithm: sha256WithRSAEncryption
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Issuer: C=CN, ST=BeiJing, L=BeiJing, O=k8s, OU=System, CN=Kubernetes
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Validity
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Not Before: Apr 5 05:36:00 2017 GMT
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Not After : Apr 5 05:36:00 2018 GMT
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Subject: C=CN, ST=BeiJing, L=BeiJing, O=k8s, OU=System, CN=kubernetes
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...
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X509v3 extensions:
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X509v3 Key Usage: critical
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Digital Signature, Key Encipherment
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X509v3 Extended Key Usage:
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TLS Web Server Authentication, TLS Web Client Authentication
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X509v3 Basic Constraints: critical
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CA:FALSE
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X509v3 Subject Key Identifier:
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DD:52:04:43:10:13:A9:29:24:17:3A:0E:D7:14:DB:36:F8:6C:E0:E0
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X509v3 Authority Key Identifier:
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keyid:44:04:3B:60:BD:69:78:14:68:AF:A0:41:13:F6:17:07:13:63:58:CD
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X509v3 Subject Alternative Name:
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DNS:kubernetes, DNS:kubernetes.default, DNS:kubernetes.default.svc, DNS:kubernetes.default.svc.cluster, DNS:kubernetes.default.svc.cluster.local, IP Address:127.0.0.1, IP Address:172.20.0.112, IP Address:172.20.0.113, IP Address:172.20.0.114, IP Address:172.20.0.115, IP Address:10.254.0.1
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...
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```
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+ 确认 `Issuer` 字段的内容和 `ca-csr.json` 一致；
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+ 确认 `Subject` 字段的内容和 `kubernetes-csr.json` 一致；
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+ 确认 `X509v3 Subject Alternative Name` 字段的内容和 `kubernetes-csr.json` 一致；
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+ 确认 `X509v3 Key Usage、Extended Key Usage` 字段的内容和 `ca-config.json` 中 `kubernetes` profile 一致；
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### 使用 `cfssl-certinfo` 命令
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``` bash
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$ cfssl-certinfo -cert kubernetes.pem
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...
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{
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"subject": {
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"common_name": "kubernetes",
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"country": "CN",
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"organization": "k8s",
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"organizational_unit": "System",
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"locality": "BeiJing",
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"province": "BeiJing",
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"names": [
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"CN",
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"BeiJing",
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"BeiJing",
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"k8s",
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"System",
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"kubernetes"
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]
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},
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"issuer": {
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"common_name": "Kubernetes",
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"country": "CN",
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"organization": "k8s",
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"organizational_unit": "System",
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"locality": "BeiJing",
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"province": "BeiJing",
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"names": [
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"CN",
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"BeiJing",
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"BeiJing",
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"k8s",
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"System",
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"Kubernetes"
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]
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},
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"serial_number": "174360492872423263473151971632292895707129022309",
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"sans": [
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"kubernetes",
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"kubernetes.default",
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"kubernetes.default.svc",
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"kubernetes.default.svc.cluster",
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"kubernetes.default.svc.cluster.local",
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"127.0.0.1",
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"10.64.3.7",
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"10.254.0.1"
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],
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"not_before": "2017-04-05T05:36:00Z",
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"not_after": "2018-04-05T05:36:00Z",
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"sigalg": "SHA256WithRSA",
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...
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```
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## 分发证书
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将生成的证书和秘钥文件（后缀名为`.pem`）拷贝到所有机器的 `/etc/kubernetes/ssl` 目录下备用；
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``` bash
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$ sudo mkdir -p /etc/kubernetes/ssl
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$ sudo cp *.pem /etc/kubernetes/ssl
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```
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## 参考
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+ [Generate self-signed certificates](https://coreos.com/os/docs/latest/generate-self-signed-certificates.html)
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+ [Setting up a Certificate Authority and Creating TLS Certificates](https://github.com/kelseyhightower/kubernetes-the-hard-way/blob/master/docs/02-certificate-authority.md)
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+ [Client Certificates V/s Server Certificates](https://blogs.msdn.microsoft.com/kaushal/2012/02/17/client-certificates-vs-server-certificates/)
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+ [数字证书及 CA 的扫盲介绍](http://blog.jobbole.com/104919/) |