实践说明

​ 在Kubernetes中添加一个普通用户，目前有两种通信方式，一种是外部认证，比如AD域管理，另外一种也是常用的TLS及数字证书的通信场景，后者是Kubernetes组件内部基本的安全通信方式。以下操作采用后者进行操作，为了简化操作，将证书和用户创建配置进行脚本化。

实践操作

1. 证书签署请求准备工作

$ cat bin/csr-gen.go 
package main 

import (
  "crypto/rand"
  "crypto/rsa"
  "crypto/x509"
  "crypto/x509/pkix"
  "encoding/asn1"
  "encoding/pem"
  "os"
)

func main() {
  name := os.Args[1]
  user := os.Args[2]

  key, err := rsa.GenerateKey(rand.Reader, 1024)
  if err != nil {
    panic(err)
  }

  keyDer := x509.MarshalPKCS1PrivateKey(key)
  keyBlock := pem.Block {
    Type: "RSA PRIVATE KEY",
    Bytes: keyDer,
  }
  keyFile, err := os.Create(name + "-key.pem")
  if err != nil {
    panic(err)
  }
  pem.Encode(keyFile, &keyBlock)
  keyFile.Close()

  //CN值，作为kubeconfig作为用户名使用，非常重要
  commonName := user
  emailAddress := "[email protected]"
  //用户组
  org := "kubernetes"
  orgUnit := "kubernetes"
  city := "GuangZhou"
  state := "WA"
  country := "CN"

  subject := pkix.Name {
    CommonName:          commonName,
    Country:             []string{country},
    Locality:            []string{city},
    Organization:        []string{org},
    OrganizationalUnit:  []string{orgUnit},
    Province:            []string{state},
  }
  asn1, err := asn1.Marshal(subject.ToRDNSequence())
  if err != nil {
     panic(err)
  }

  csr := x509.CertificateRequest{
     RawSubject:          asn1,
     EmailAddresses:      []string{emailAddress},
     SignatureAlgorithm:   x509.SHA256WithRSA,
  }

  bytes, err := x509.CreateCertificateRequest(rand.Reader, &csr, key)
  if err != nil {
     panic(err)
  }
  csrFile, err := os.Create(name + ".csr")
  if err != nil {
    panic(err)
  }

  pem.Encode(csrFile, &pem.Block{Type: "CERTIFICATE REQUEST", Bytes:bytes})
  csrFile.Close()
}
$ cat bin/k8s-gen-cert.sh 
#!/bin/bash

#向K8s发起证书申请请求名称
csr_name="my-client-usr"

#Kubeconfig 用户标识名称
name="${1:-lvzhiqiang}"

#证书申请文件
csr="${2}"

cat <<EOF | kubectl create -f -
apiVersion: certificates.k8s.io/v1beta1
kind: CertificateSigningRequest
metadata:
  name: ${csr_name}
spec:
  groups:
  - system:authenticated
  request: $(cat ${csr} | base64 | tr -d '\n')
  usages:
  - digital signature
  - key encipherment
  - client auth
EOF

echo
echo "Approving signing request."
kubectl certificate approve ${csr_name}

echo 
echo "Downloading certificate."
kubectl get csr ${csr_name} -o jsonpath='{.status.certificate}' \
  | base64 --decode > $(basename ${csr} .csr).crt

echo 
echo "Cleaning up"
kubectl delete csr ${csr_name}

echo 
echo "Add the following to the 'users' list in your kubeconfig file:"
echo "- name: ${name}"
echo "  user:"
echo "    client-certficate: ${PWD}/$(basename ${csr} .csr).crt"
echo "    client-key: ${PWD}/$(basename ${csr} .csr)-key.pem"
echo 
echo "Next you may want to add role-binding for this user."
$ kubectl delete csr my-client-usr
$ go version 
go version go1.15.7 linux/amd64
$ go run  bin/csr-gen.go client lvzhiqiang
$ sh bin/k8s-gen-cert.sh lvzhiqiang client.csr
certificatesigningrequest.certificates.k8s.io/my-client-usr created

#同意签署请求
Approving signing request.
certificatesigningrequest.certificates.k8s.io/my-client-usr approved
#下载CRT证书文件
Downloading certificate.

Cleaning up
certificatesigningrequest.certificates.k8s.io "my-client-usr" deleted

Add the following to the 'users' list in your kubeconfig file:
- name: lvzhiqiang
  user:
    #客户端证书文件和Key
    client-certficate: /root/create-k8s-user/client.crt
    client-key: /root/create-k8s-user/client-key.pem

Next you may want to add role-binding for this user.

2. 配置Kubeconfig和命名空间

$ kubectl config set-credentials lvzhiqiang --client-key=/root/create-k8s-user/client-key.pem --client-certificate=/root/create-k8s-user/client.crt --embed-certs=true
$ kubectl config set-context lvzhiqiang --cluster=kubernetes --user=lvzhiqiang
$ ns="developer"
$ kubectl create namespace ${ns}
$ kubectl annotate namespace ${ns} annotation_key=annotation_value

3. 角色绑定

$ cat rolebinding.yaml 
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: developer
  namespace: developer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: edit
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: User
  name: lvzhiqiang
$ kubectl apply  -f rolebinding.yaml

4. 测试

$ kubectl run demo-dev01 --image=nginx:latest -n developer
$ kubectl config use-context lvzhiqiang 
$ kubectl get pods -n developer #这里要指定命名空间，除非在kubeconfig配置的时候指定了默认命名空间
NAME         READY   STATUS    RESTARTS   AGE
demo-dev01   1/1     Running   0          21m

5. 补充

复制 /root/.kube/config 一份出来，然后将该文件里关于管理员的配置信息去掉，保留刚创建的普通用户信息，然后拷贝给其他开发用户使用。

实践参考资料

1.https://kubernetes.io/zh/docs/reference/access-authn-authz/certificate-signing-requests/
2.https://kubernetes.io/zh/docs/reference/access-authn-authz/rbac/#user-facing-roles

3.《Kubernetes实战》