DS remote access guidelines for UNIX servers.

DarkScience remote access information:

Guidelines follow;
* sshd will listen on port 22 and 2222
* firewall will allow all connections to 2222
* global inbound connections on 2222 will have a rate limit
* firewall will allow connections to 22 from -ONLY- other DS hosts.
* mandatory allowed hosts are: phobos.drk.sc and deimos.drk.sc ; you may add more as you wish, but those are required.
* sshd will have a hardcoded list of AllowUsers.
* only staff may be contained in AllowUsers.
* sshd will only accept public-keys
* ssh version 2 will be required, version 1 is deprecated.
* where possible sshd will be configured to allow ed25519 in liu of RSA