Hi. What is the most secure and convenient way to transfer files between two or more Workstation VMs? Whonix wiki doesn’t have any information about this. I am not interested in connections between Gateway and Workstation, just between multiple Workstations. Is setting up an SSH server on Workstations machine and then use Secure Copy will be a good choice? Any risks that an attacker can reach my Workstation machine through SSH?
You can setup shared folders between two guests. Both Virtualbox & KVM have documentation on this.
But that is not secure approach I guess because shared folders rely on non-free VirtualBox guest additions. More secure is to set up an SSH server inside one of Workstations inside internal virtual interface and then secure copy files to them. I think so. So could you tell me what is more secure?
Not non-free. See:
VirtualBox Guest Additions ISO Freedom vs Non-Freedom
Use KVM and apply the same concept. No closed plugins of any type are ever needed.