相关知识
HTTP/HTTPS 是什么?
SSL/TLS 是什么？
为什么要部署 HTTPS？
怎么部署 HTTPS 呢？
怎么获得 SSL 安全证书呢？
Let’s Encrypt 简介
Certbot 简介
实际操作
Certbot 使用方法
Certbot 的官网是https://certbot.eff.org/, 我们打开这个链接，选择自己使用的 web server 和操作系统。选择完之后，官网就会显示出对应的安装操作步骤。
以目前我所使用的服务器为例，web server 使用Nginx(1.12)，操作系统是CentOS(7.3)。因为 Certbot 打包在EPEL中，所以在安装 Certbot 之前要先安装EPEL
yum -y install epel-release然后按着官网给出的步骤提示命令安装 Certbot
yum install python2-certbot-nginx安装完毕后，继续输入官网提示命令
certbot --nginx运行此命令会自动获取证书，并且 Certbot 会自动编辑Nginx配置文件配置HTTPS服务。
ImportError: No module named 'requests.packages.urllib3'可以看出是缺少一个模块包，看配置命令在命令台的输出，Certbot 是用 python 来写 Nginx 配置。既然是用的 python，可以通过 pip list 命令查看 python 的依赖包列表。但是查看是已经存在的，这个问题很快通过 Certbot 在 github 上的一个 Issues 找到了答案（Issues链接）。目前看是包的版本依赖有问题，执行以下命令进行依赖包的重装
pip uninstall requests
pip uninstall urllib3
yum remove python-urllib3
yum remove python-requests
yum install python-urllib3
yum install python-requests
yum install certbot再次执行 certbot --nginx 命令成功。命令执行后首先会提示输入一个邮箱地址，主要作用是订阅一些通知，输入后回车。
[root@izuf6fco0zwyipdq9485s2z ~]# certbot --nginx
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator nginx, Installer nginx
▽
Enter email address (used for urgent renewal and security notices) (Enter 'c' to
cancel): demo@mail.com // 演示邮箱
Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -回车后 Certbot 就会自动请求下载 Let's Encrypt 证书，并设置 Nginx 配置文件。期间会有一些同意相关协议和选择哪个网站配置的交互，这个看输出文字就能明白意思。
...
▽
server {
(A)gree/(C)ancel: a
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Would you be willing to share your email address with the Electronic Frontier
Foundation, a founding partner of the Let's Encrypt project and the non-profit
organization that develops Certbot? We'd like to send you email about our work
encrypting the web, EFF news, campaigns, and ways to support digital freedom.
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(Y)es/(N)o: y
Starting new HTTPS connection (1): supporters.eff.org
Which names would you like to activate HTTPS for?
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1: kisstime.top
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Select the appropriate numbers separated by commas and/or spaces, or leave input
blank to select all options shown (Enter 'c' to cancel): 1
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for kisstime.top
Cleaning up challenges
...An unexpected error occurred:
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe5 in position 2: ordinal not in range(128)
Please see the logfiles in /var/log/letsencrypt for more details.熟悉 python 的同学应该对这个错误比较了解。不过博主 python 还是用的比较少，花了点时间了解了一下。
self.response.out.write("你好"+self.request.get("argu"))那理解了这个错误原因后，我这边首先想到的就是网站的 Nginx 配置文件中是否含有中文。打开一看，确实存在中文注释。将注释去掉，重新执行命令成功不在报错
接着命令交互会提示是否将所有HTTP重定向到HTTPS，我这边选择全部重定向也就是「2」。
Cleaning up challenges
Deploying Certificate to VirtualHost: //这边会显示你的网站配置文件目录
Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.
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1: No redirect - Make no further changes to the webserver configuration.
2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for
new sites, or if you're confident your site works on HTTPS. You can undo this
change by editing your web server's configuration.
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Select the appropriate number [1-2] then [enter] (press 'c' to cancel): 2
Redirecting all traffic on port 80 to ssl in //这边会显示你的网站配置文件目录
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Congratulations! You have successfully enabled https://kisstime.top
You should test your configuration at:
https://www.ssllabs.com/ssltest/analyze.html?d=kisstime.top
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IMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at:
.../fullchain.pem
Your key file has been saved at:
.../privkey.pem
Your cert will expire on 2019-02-14. To obtain a new or tweaked
version of this certificate in the future, simply run certbot again
with the "certonly" option. 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-leOK，当完成上面最后一步后，输入如上信息后就表明 HTTPS 配置成功了！我们可以通过提示中的 网址来测试网站是否能够 HTTPS 来进行访问
You should test your configuration at:
https://www.ssllabs.com/ssltest/analyze.html?d=kisstime.top事实证明，高兴的太早了。。。通过测试网站和直接访问域名发现网站都是访问不了。思考了一下，确认下服务器的443端口是否开启，我这边用的是阿里云的服务器，登录控制台查看安全组规则，发现确实是443端口没有开启，配置开启后，重新访问成功。
其他
Nginx的设置说明
基本上 Certbot 会在对应的 Nginx 配置文件加上下面的参数：
server {
# ... other configs
# SSL 设置
listen 443 ssl;
# set crt and key
ssl_certificate .../fullchain.pem;
ssl_certificate_key .../privkey.pem;
# include 基本的 ssl 设置
include .../options-ssl-nginx.conf;
# Certbot 也会生成一把 Diffie-Hellman 密钥
ssl_dhparam .../ssl-dhparams.pem;
# ... other configs
}自动更新证书
Let’s Encrypt 免费SSL证书用起来非常方便，但每次申请只有三个月有效期，在每次到期之前都需要重新申请，Certbot 已经提供了一键续订的命令
certbot renew我们可以通过添加此条命令的cron作业（或systemd计时器）来安排证书的自动续订
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
0 0,12 * * * certbot renew --quiet Certbot 的 log 路径
Certbot 的 log 预设路径在 /var/log/letsencrypt，有需要可以去确认查看。
相关第三方
certbot-auto是对脚本certbot的封装，可以设置系统环境或自动升级。
参考资料
牛顿曾经说过：如果说我看得比别人更远些，那是因为我站在巨人的肩膀上。（If I have seen further, it is by standing on the shoulders of giants.）感谢。
- https://certbot.eff.org/
- https://linuxstory.org/deploy-lets-encrypt-ssl-certificate-with-certbot
- https://blog.csdn.net/use_my_heart/article/details/51303317
- https://blog.hellojcc.tw/2018/05/02/setup-https-with-letsencrypt-on-nginx/