Cloudinit is used by many cloud images e.g. on EC2 to obtain their initial configuration, like IP address, ssh keys and the like. Is there a way of using it with VirtualBox in a similar way?

I'm looking for a way of putting an ssh authorized_keys file on an VirtualBox instance without having to hard-code it into the image itself.

There is a section on "No Cloud" here but I'm not entirely understanding how this would apply to VirtualBox. Can I generate a /dev/sdb with the files in question, and provide this to VirtualBox as a second drive before booting the instance, and it somehow magically will pick the info up?