1、生成服务器私钥
 openssl genrsa -out client.key 4096
  2、生成证书签名请求(CSR)
 openssl req -new -key client.key -out client.csr
  3、使用上一步的证书签名请求签发证书
 openssl x509 -req -days 365 -in client.csr -signkey client.key -out client.crt
   二、一步生成证书
 openssl req -new -x509 -newkey rsa:4096 -keyout client.key -out client.crt
  参考网址:https://docs.azure.cn/zh-cn/articles/azure-operations-guide/application-gateway/aog-application-gateway-howto-create-self-signed-cert-via-openssl