2018-12-28

Letsencrypt通过DNS的TXT记录来验证域名有效性

说明

我们在使用letsencrypt获取免费的HTTPS证书的时候，letsencrypt需要对域名进行验证。默认情况下它的验证方式是这样的：

certbot程序在web目录的根目录下放置一个文件。
letsencrypt的服务器通过域名来访问这个文件，来验证你申请的域名是属于你的
但有时候我们想为内网的某台主机设置HTTPS，因为内网的主机无法被letsencrypt的服务器访问到，certbot --nginx certonly就会出现Connection refused的错误。

为了解决上述问题，我们可以更改验证方式，使用DNS记录来验证域名。

安装部署

参考官方文档依次进行以下操作：

安装第三方软件源：

1 2	$ sudo yum -y install yum-utils $ sudo yum-config-manager --enable rhui-REGION-rhel-server-extras rhui-REGION-rhel-server-optional

安装python2-certbot-nginx

1	$ sudo yum install python2-certbot-nginx

测试certbot

1	$ sudo certbot --nginx

如有报错则执行以下操作修复：

1
2
3

$ sudo pip install requests urllib3 pyOpenSSL --force --upgrade
$ sudo pip install --upgrade --force-reinstall 'requests==2.6.0'
$ sudo pip install idna==2.6 urllib3==1.22

手动配置DNS的TXT记录验证域名

运行

1	$ sudo certbot --manual --preferred-challenges dns certonly

输入域名（多个域名需以逗号或空格分开）并同意记录本机IP

[root@MyPrecious ~]# certbot --manual --preferred-challenges dns certonly
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator manual, Installer None
Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org
Please enter in your domain name(s) (comma and/or space separated)  (Enter 'c'
to cancel): *.opstrip.com,opstrip.com
Obtaining a new certificate
Performing the following challenges:
dns-01 challenge for opstrip.com
    
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
NOTE: The IP of this machine will be publicly logged as having requested this
certificate. If you're running certbot in manual mode on a machine that is not
your server, please ensure you're okay with that.
    
Are you OK with your IP being logged?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
(Y)es/(N)o: y

后开始获取证书，会有类似以下提示：

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Please deploy a DNS TXT record under the name
_acme-challenge.opstrip.com with the following value:
    
On6MxDvMMz-nRST-PAu3VHQoMQ2nuzYbvtA4Gw13EiM
    
Before continuing, verify the record is deployed.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Press Enter to Continue

此时certbot程序就会暂停，等待我们去添加DNS记录。

根据以上提示，在opstrip.com域名解析下，新增一条TXT解析，
解析类型为TXT
主机记录为_acme-challenge
记录值为On6MxDvMMz-nRST-PAu3VHQoMQ2nuzYbvtA4Gw13EiM
添加完成后执行

1	dig -t txt _acme-challenge.opstrip.com

若返回有以上记录值则配置生效。回车以继续下一个域名。
当依次完成所有的域名验证时，返回以下内容

Waiting for verification...
Resetting dropped connection: acme-v02.api.letsencrypt.org
Resetting dropped connection: acme-v02.api.letsencrypt.org
	
Cleaning up challenges
Resetting dropped connection: acme-v02.api.letsencrypt.org
	
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/opstrip.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/opstrip.com/privkey.pem
   Your cert will expire on 2019-03-28. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - If you like Certbot, please consider supporting our work by:
    
   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

表示证书已成功获取。如果验证失败请等待DNS记录更新并多试几次。
其中，/etc/letsencrypt/live/opstrip.com/fullchain.pem为带证书链的公钥，/etc/letsencrypt/live/opstrip.com/privkey.pem为对应的私钥。

证书续签

在crontab中添加以下任务

1	0 0,12 * * * python -c 'import random; import time; time.sleep(random.random() * 3600)' && certbot renew

官方建议每天运行两次，是站点保持在线状态以免证书被吊销。在证书到期或续订之前不会执行任何操作。

参考来源：

本文标题:Letsencrypt通过DNS的TXT记录来验证域名有效性

文章作者:Jeff

发布时间:2018-12-28, 20:15:14

最后更新:2019-01-05, 01:07:43

原始链接:https://opstrip.com/2018/12/28/Getting-Letsencrypt-Certificate-with-DNS-TXT/

许可协议: "署名-非商用-相同方式共享 4.0" 转载请保留原文链接及作者。