ProxyCommand Example

Solution:
SSH to firewall, have it run Netcat to connect to actual destination.

home$ cat ~/.ssh/config
  Host work-desktop
  Hostname 192.168.16.80
  HostKeyAlias work-desktop
  ProxyCommand=ssh firewall.my_company.com /usr/bin/nc %h 22
  
  Host work-www
  Hostname 192.168.20.04
  HostKeyAlias work-www
  ProxyCommand=ssh firewall.my_company.com /usr/bin/nc %h 22
  
home$ scp -pr work-desktop:cvs .