Assuming that the users have dynamic IPs (so I can't whitelist) and that setting up a VPN is not an option, is it a valid approach to restrict access to an administration area by only allowing IPs that are currently connected via SSH on the server? Are there any security issues with this?
What if the server in which the user is logged in via SSH isn't the same as the site's server. Is it OK to have the site call a service on that other server that would tell if an specific IP is logged in? Any implications that I'm not aware of?
PS: I'd still be asking for password over SSL and implementing other basic security measures, the question is about restricting access.
PPS: I understand the usability issues, assume users are always logged in via SSH.