firewalld Whitelist source IP addresses in CentOS 7

I'd accomplish this by adding sources to a zone. First checkout which sources there are for your zone:

firewall-cmd --permanent --zone=public --list-sources

If there are none, you can start to add them, this is your "whitelist"

firewall-cmd --permanent --zone=public --add-source=192.168.100.0/24
firewall-cmd --permanent --zone=public --add-source=192.168.222.123/32

(That adds a whole /24 and a single IP, just so you have a reference for both a subnet and a single IP)

Set the range of ports you'd like open:

firewall-cmd --permanent --zone=public --add-port=1-3389/tcp
firewall-cmd --permanent --zone=public --add-port=1-3389/udp

This just does ports 1 through 22. You can widen this, if you'd like.

Now, reload what you've done.

firewall-cmd --reload

And check your work:

 firewall-cmd --zone=public --list-all

managed server