Is there a way of restricting read/write access to files to drag and drop?
The idea is that my application is effectively put into a chroot-like prison (perhaps, with the exception of a configuration directory with quota, say), so that I have full control over which files can be actually accessed. After a second thought, this is probably an old idea floating around in this community, but I have not found any hints, yet.
This is a good idea, but the problem is always with the X server. Any X application can listen for events (key logger) or create them. So, a sandboxed program can just searh for an xterm and start typing commands! Apart from that, there's nothing stopping you doing it now (you can even run the program on a different machine; it can still get the dragged data, provided host names in DnD are turned on in ROX-Filer's config box).
See Plash: the Principle of Least Authority shell for an experimental implementation of this.