Access NAS from WAN

I wanted to install a Hard drive on my openwrt, so that a machine on lan side (192.168.1.x) can access the files on my harddrive.
This seems to be pretty easy and it works.

Is it possible to access this drive from my wan-side computer (192.168.178.x) and even save files on this network drive although it is configured on the lan side?

I read something about the port 445? is this the only port I have to open?
Thanks to help out a noob :wink:

Port 445 is for samba, but there are other ports too, like 139.

Google samba firewall ports.