kubernetes kubectl 簽名TLS證書

kubernetes 集羣可以爲證書籤名，用於集羣內部的TLS通信，ca就是集羣的ca，每個pod裏面serviceaccount的secret都帶着。

1. 創建證書籤名請求-csr

$ cat <<EOF | ./cfssl genkey - | ./cfssljson -bare server
{
  "hosts": [
    "nginx.default.svc.cluster.local"
  ],
  "CN": "nginx.default.svc.cluster.local",
  "key": {
    "algo": "ecdsa",
    "size": 256
  }
}
EOF
2020/06/03 10:49:59 [INFO] generate received request
2020/06/03 10:49:59 [INFO] received CSR
2020/06/03 10:49:59 [INFO] generating key: ecdsa-256
2020/06/03 10:49:59 [INFO] encoded CSR

生成了私鑰文件 server-key.pem 和簽名請求文件 server.csr

2. 創建發送給 Kubernetes API的 csr 對象

$ cat <<EOF | kubectl apply -f -
apiVersion: certificates.k8s.io/v1beta1
kind: CertificateSigningRequest
metadata:
  name: my-svc.default
spec:
  request: $(cat server.csr | base64 | tr -d '\n')
  usages:
  - digital signature
  - key encipherment
  - server auth
EOF
certificatesigningrequest.certificates.k8s.io/my-svc.default created

查看csr對象，狀態爲Pending

$ k get csr
NAME             AGE     SIGNERNAME                     REQUESTOR          CONDITION
my-svc.default   6m25s   kubernetes.io/legacy-unknown   kubernetes-admin   Pending

3. 批准證書籤名請求

$ k certificate approve my-svc.default
certificatesigningrequest.certificates.k8s.io/my-svc.default approved

$ k get csr
NAME             AGE   SIGNERNAME                     REQUESTOR          CONDITION
my-svc.default   11m   kubernetes.io/legacy-unknown   kubernetes-admin   Approved,Issued

4. 下載證書文件

$ k get csr my-svc.default -o jsonpath='{.status.certificate}' | base64 --decode > server.crt

得到證書文件 server.crt

5. 使用 server.crt 和 server-key.pem 創建 https server

5.1 創建證書和私鑰的secret

k create secret generic https --from-file=server.crt --from-file=server-key.pem

5.2 創建nginx配置文件的cm

$ cat <<EOF | k apply -f -
> apiVersion: v1
> kind: ConfigMap
> metadata:
>   name: nginx
> data:
>   my-nginx-config.conf: |
>     server {
>       listen 80;
>       listen 443 ssl;
>       server_name www.example.com;
>       ssl_certificate certs/server.pem;
>       ssl_certificate_key certs/server-key.pem;
>       ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
>       ssl_ciphers HIGH:!aNULL:!MD5;
>
>       location / {
>         root /usr/share/nginx/html;
>         index index.html index.htm;
>       }
>     }
> EOF
configmap/nginx created

5.3 創建nginx部署

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      initContainers:
      - name: page-initiator
        image: busybox
        imagePullPolicy: Never
        command: ['sh', '-c', 'echo $HOSTNAME > /data/index.html']
        volumeMounts:
        - mountPath: /data
          name: page-volume
      containers:
      - image: nginx:1.7.9
        name: nginx
        imagePullPolicy: Never
        volumeMounts:
        - mountPath: /usr/share/nginx
          name: page-volume
        - mountPath: /etc/nginx/certs
          name: certs
          readOnly: true
        - mountPath: /etc/nginx/conf.d
          name: config
          readOnly: true
        ports:
        - containerPort: 80
        - containerPort: 443
      volumes:
      - name: page-volume
        emptyDir: {}
      - name: certs
        secret:
          secretName: https
      - name: config
        configMap:
          name: nginx
          items:
            - key:  my-nginx-config.conf
              path: https.conf

6. 在pod中使用 serviceaccount 帶的 ca.crt 訪問 https 站點

$ k run curl --image=curlimages/curl --command -- sleep infinity
$ k exec -it curl-9c984d666-9hlfc -- sh
$ curl https://nginx.default.svc.cluster.local --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
nginx-7464848dfc-twmtv