[CentOS] Client backup solution with web interface

I have tried to google for this kind of application, but have not found.

There should be a web interface, where the client (person) could start an rsync backup of his/her workstation to a remote server (= the web server machine).

I need this because the client has a dynamic ip, so the ssh key authentication on the server never works un-interactively - because every time the cient ip has changed, and the script asks:

The authenticity of host ##.##.##.## can't be established. RSA key fingerprint is ##########. Are you sure you want to continue connecting (yes/no)?

Or could there be some other approach to this?

- Jussi