申請設定 Let's Encrypt 免費 SSL 憑證(CentOS + Apache/Nginx)

因為 Google Chrome 自 2018/05/01 對於沒有合法的 SSL 網站憑證, 就會出現警告, 所以就出現要買 SSL 網站憑證的議題, 針對個人網站或是非正式的公司網站, 採用 Let's Encrypt 免費網站 SSL 憑證似乎是個不錯的選擇.

• 這過程會檢查與安裝 python packages 並讀取 web server 的設定, 查看目前的網站網址, 如果有設定 Virtual Host 多網址, 也可以選擇產生多網域的憑證¹⁾
• 原則上只要最後詢問 Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access. 是否要讓瀏覽 http 網址自動轉至 https 的問題後, 出現以下的訊息, 就表示已自動將 web server 的設定都改好

  :
  Congratulations! You have successfully enabled https://www.ichiayi.com
  
  You should test your configuration at:
  https://www.ssllabs.com/ssltest/analyze.html?d=www.ichiayi.com
  :

• https://www.ssllabs.com/ssltest/analyze.html?d=[網址]
• 測試結果如下圖所示
  
• 其中檢測 CAA Record 這一項需要在 DNS 設定, 如果想完整設定可使用以下網站協助產生設定資料
  https://sslmate.com/caa/
  當 DNS 完成設定後, 可以使用以下網站功能檢測
  https://caatest.co.uk/

• 必須要將 /etc/httpd/conf.d/ssl.conf 內的 “SSL Virtual Host Context” 底下預設 VirtualHost 整個拿掉才能正常運作

  :
  ##
  ## SSL Virtual Host Context
  ##
  
  #<VirtualHost _default_:443>
  #:
  #:
  #</VirtualHost>

• certbot-auto 會自動產生 /etc/httpd/conf/httpd-le-ssl.conf 定義 VirtualHost, 如果沒有產生要直接修改 ssl.conf 點這裡看 wiki.ichiayi.com 範例

  :
  :
      # Explictly disable SSL compression (should default to off anyway...)
      # Note enabling SSL compression makes Apache vulnerable to CRIME attack.
      SSLCompression off
  
      # Default certificate file to use (provided by TurnKey)
      #SSLCertificateFile /etc/ssl/private/cert.pem
      SSLCertificateFile /etc/letsencrypt/live/wiki.ichiayi.com/cert.pem
      SSLCertificateKeyFile /etc/letsencrypt/live/wiki.ichiayi.com/privkey.pem
  
  </IfModule>

  <note> * 如果之後增加 VirtualHost 透過

  certbot-auto --apache certonly

  產生憑證後, 需要到 /etc/httpd/conf/httpd-le-ssl.conf 手動加上定義 * 如果想要讓連上 http: 自動轉 https: 則在 /etc/httpd/conf/httpd.conf 內定義, 點這裡看範例|

  :
  :
  <VirtualHost *:80>
  ServerName www.ichiayi.com
  ServerAdmin [email protected]
  DocumentRoot /var/www/www.ichiayi.com_html
  CustomLog logs/www.ichiayi.com-access_log common
  ErrorLog logs/www.ichiayi.com-error_log
  Redirect permanent / https://www.ichiayi.com/
  </VirtualHost>
  :

  </note> ===== nginx 相關設定 ===== * 原則上會由 certbot-auto 自動完成修改, 但如果出現問題需要手動處理可以檢查 nginx 內的網站設定檔目錄 /etc/nginx/conf.d * Exp. www.ichiayi.com 的設定檔路徑 : ++/etc/nginx/conf.d/www_ichiayi.conf

  server {
          server_name     www.ichiayi.com;
  
          access_log /var/log/nginx/www.ichiayi.com.access.log main;
          error_log /var/log/nginx/www.ichiayi.com.error.log;
  
          location / {
         :
         :
          }
  
      listen 443 ssl; # managed by Certbot
      ssl_certificate /etc/letsencrypt/live/www.ichiayi.com/fullchain.pem; # managed by Certbot
      ssl_certificate_key /etc/letsencrypt/live/www.ichiayi.com/privkey.pem; # managed by Certbot
      include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
      ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
  
  }
  
  server {
      if ($host = www.ichiayi.com) {
          return 301 https://$host$request_uri;
      } # managed by Certbot
  
  
          listen  80;
          server_name     www.ichiayi.com;
      return 404; # managed by Certbot
  
  
  }

• 因為免費憑證只有 3 個月的有效期, 所以自動檢查與更新是很重要
• certbot 就具有自動更新的功能, 可設定每天檢查三次(00:00 08:00 16:00), 執行時先隨機取 3600 中的一個秒數等待, 避免造成同時間大家一起連上 Let's Encrypt 主機, 方式如下
  • CentOS 7

    vi /etc/crontab

    :
    # let's encrypt
    0 */8 * * * root python -c 'import random; import time; time.sleep(random.random() * 3600)' && certbot renew > /tmp/cert-bot_renew.log

    service crond restart

• 之後就可以在 /tmp/cert-bot_renew.log 看到檢查更新的紀錄

1. 執行以下的語法

   /root/lets-encrypt/certbot-auto -d ichiayi.com -d *.ichiayi.com --manual --preferred-challenges dns certonly --server https://acme-v02.api.letsencrypt.org/directory

2. 當出現以下第二次的 Before continuing, verify the record is deployed. 必須去設定 ichiayi.com 的 DNS

   Please deploy a DNS TXT record under the name
   _acme-challenge.ichiayi.com with the following value:
   
   0sGmQQTfit9lW3okOa4jaYmefNQS4FsF6zZgEtyppKw
   
   Before continuing, verify the record is deployed.
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   Press Enter to Continue
   
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   Please deploy a DNS TXT record under the name
   _acme-challenge.ichiayi.com with the following value:
   
   fEsd-DYrN-AB_XVWb-Aa9Yx9OxCofBlFkxNmt7RWiCk
   
   Before continuing, verify the record is deployed.

3. 將前面兩次出現的 hash 值正確設定到 ichiayi.com 的 DNS TXT Record 內, Exp.

   :
   ;
   $TTL 86400      ; 1 day -- ; 3 hours
   $ORIGIN ichiayi.com.
   @               IN SOA  ns1 server (
                                   2018123100 ; serial
                                   28800       ; refresh (2 hours)
                                   14400        ; retry (15 minutes)
                                   720000     ; expire (1 week)
                                   86400      ; minimum (12 hours)
                                   )
                           NS      ns4.everplast.net.
                           NS      ns7.ichiayi.com.
   ;
   ; lets-encrypt SSL Cert
   _acme-challenge IN TXT  "0sGmQQTfit9lW3okOa4jaYmefNQS4FsF6zZgEtyppKw"
   _acme-challenge IN TXT  "fEsd-DYrN-AB_XVWb-Aa9Yx9OxCofBlFkxNmt7RWiCk"
   ;
   :

4. 重新啟動 DNS 讓這兩個 TXT 生效, 可透過 nslookup 指定詢問 server 8.8.8.8 來確認

   C:\Users\jonathan>nslookup
   預設伺服器:  UnKnown
   Address:  192.168.1.5
   > server 8.8.8.8
   預設伺服器:  google-public-dns-a.google.com
   Address:  8.8.8.8
   > _acme-challenge.ichiayi.com
   伺服器:  google-public-dns-a.google.com
   Address:  8.8.8.8
   名稱:    _acme-challenge.ichiayi.com
   > set type=txt
   > _acme-challenge.ichiayi.com
   伺服器:  google-public-dns-a.google.com
   Address:  8.8.8.8
   未經授權的回答:
   _acme-challenge.ichiayi.com  text =
           "fEsd-DYrN-AB_XVWb-Aa9Yx9OxCofBlFkxNmt7RWiCk"
   _acme-challenge.ichiayi.com  text =
           "0sGmQQTfit9lW3okOa4jaYmefNQS4FsF6zZgEtyppKw"

5. 確認可以正確查詢到這兩個新增的 TXT Record 後才可執行下一步, 當出現以下訊息就表示正確產生

   :
   Waiting for verification...
   Cleaning up challenges
   
   IMPORTANT NOTES:
    - Congratulations! Your certificate and chain have been saved at:
      /etc/letsencrypt/live/ichiayi.com/fullchain.pem
      Your key file has been saved at:
      /etc/letsencrypt/live/ichiayi.com/privkey.pem
      Your cert will expire on 2019-03-31. To obtain a new or tweaked
      version of this certificate in the future, simply run certbot-auto
      again. To non-interactively renew *all* of your certificates, run
      "certbot-auto renew"
    - Your account credentials have been saved in your Certbot
      configuration directory at /etc/letsencrypt. You should make a
      secure backup of this folder now. This configuration directory will
      also contain certificates and private keys obtained by Certbot so
      making regular backups of this folder is ideal.
    - 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

• /root/lets-encrypt/certbot-auto (下載時指定位置)
• /etc/letsencrypt/ 存放執行 certbot-auto 自動申請 SSL 相關憑證與檔案
• /var/log/letsencrypt/ 存放執行 certbot-auto 的紀錄檔案

• 因為部份網站是內部網站, 並無法對外透過 Web 方式認證自動更新憑證, 所以需要透過 DNS 即時建立 TXT Record 來認證, 如要自動認證, 就需要透過 DNS 提供整合 API 才能達成

• https://certbot.eff.org/lets-encrypt/centos6-apache
• https://certbot.eff.org/lets-encrypt/centosrhel7-other
• https://gitpress.io/@chchang/ubuntu-letsencrypt-cloudflare-wildcard
• https://blog.anzupop.com/posts/acquire-lets-encrypt-certs-using-dns-cloudflare-plugin/
• https://serverfault.com/questions/744960/configuring-ssl-with-virtual-hosts-under-apache-and-centos
• https://sslmate.com/caa/
• https://blog.heckel.xyz/2018/08/05/issuing-lets-encrypt-certificates-for-65000-internal-servers/
• https://community.letsencrypt.org/t/how-to-manually-renew-a-certificate/11263/3
• https://certbot.eff.org/docs/using.html#pre-and-post-validation-hooks
• https://dafzheng.wordpress.com/2018/03/08/%E5%9C%A8nginx%E4%B8%8A%E4%BD%BF%E7%94%A8lets-encrypt%E5%B0%87%E7%B6%B2%E9%A0%81%E8%A8%AD%E6%88%90https/