Get your free SSL certification and extend it automatically

Why SSL?

The primary reason why SSL is used is to keep sensitive information sent across the Internet encrypted so that only the intended recipient can access it. This is important because the information you send on the Internet is passed from computer to computer to get to the destination server. Any computer in between you and the server can see your credit card numbers, usernames and passwords, and other sensitive information if it is not encrypted with an SSL certificate. When an SSL certificate is used, the information becomes unreadable to everyone except for the server you are sending the information to. This protects it from hackers and identity thieves.

Why letsencrypt.org ?

Let’s Encrypt is a free, automated, and open certificate authority (CA), run for the public’s benefit. It is a service provided by the Internet Security Research Group (ISRG).
https://letsencrypt.org/about/
Advantage:

• Subdomain support
• Wildcard support
• API support
• Free

Disadvantage:

• Short period, 3 months mostly
• Command line skill needed
  

How to

We set up certification for apache as an example.

1. Generate your certificaton

   wget https://dl.eff.org/certbot-auto
   chmod a+x certbot-auto
   sudo ./certbot-auto --manual certonly

   Note:

   Separate sub-domain by comma
   Wildcard only support validate through DNS 

   In the end, you could find your cert in

   /etc/letsencrypt/live/www.yourdomain.com/

2. Apply it to Apache

   yum install mod_ssl openssl

   Edit the configuration file

   vi /etc/httpd/conf.d/ssl.conf

   Find and update

   SSLEngine on
   SSLProtocol all -SSLv2
   SSLCipherSuite DEFAULT:!EXP:!SSLv2:!DES:!IDEA:!SEED:+3DES
   
   SSLCertificateKeyFile /etc/letsencrypt/live/www.yourdomain.com/privkey.pem
   SSLCertificateFile /etc/letsencrypt/live/www.yourdomain.com/cert.pem
   SSLCertificateChainFile /etc/letsencrypt/live/www.yourdomain.com/chain.pem

   Save and restart Apache

   service restart httpd

Renew the certification

As we told, we need to renew the certification almost every 3 months.

Manually

./certbot-auto renew

Automatically

Setting up some hooks, we could make the domain validation automatically.

1. Set up and DSN modifying hook base on cloudflare.com

   vi /etc/letsencrypt/renewal/msg2.xyz.sh

   #!/bin/bash
   curl --tlsv1.2   -X PUT "https://api.cloudflare.com/client/v4/zones/ZONEID/dns_records/RECORDID" \
    -H "X-Auth-Email: [email protected]" \
    -H "X-Auth-Key: APIAUTHKEY" \
    -H "Content-Type: application/json" \
    --data '{"type":"TXT","name":"_acme-challenge.msg2.xyz","content":"'${CERTBOT_VALIDATION}'","ttl":120,"proxied":false}'
   sleep 5

   More about the API https://api.cloudflare.com/#dns-records-for-a-zone-update-dns-record

2. Run renew with --manual-auth-hook

   ./certbot-auto renew --manual-auth-hook /etc/letsencrypt/renewal/msg2.xyz.sh

   The validation will go through automatically with our hook. Just like:

   Saving debug log to /var/log/letsencrypt/letsencrypt.log
   
   ` - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   Processing /etc/letsencrypt/renewal/msg2.xyz.conf
   `- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   Plugins selected: Authenticator manual, Installer None
   Renewing an existing certificate
   Running deploy-hook command: /etc/letsencrypt/renewal-hooks/deploy/httpd.sh
   `- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   new certificate deployed without reload, fullchain is
   /etc/letsencrypt/live/msg2.xyz/fullchain.pem
   `- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   
   `- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   
   Congratulations, all renewals succeeded. The following certs have been renewed:
     /etc/letsencrypt/live/msg2.xyz/fullchain.pem (success)
   `- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

   Note: Certbo will remember the hook in the next time

Restart Apache with the renewal-hooks

Although the certification is in the newest version, we need to restart httpd service to make it effect the frontend. We could also do it automatically by the renewal-hooks.

vi /etc/letsencrypt/renewal-hooks/deploy/httpd.sh

#!/bin/sh
set -e
service httpd restart > /dev/null

Don't forget

chmod +x /etc/letsencrypt/renewal-hooks/deploy/httpd.sh

Make it as a cron job

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