usb data filtering

I need a device which makes usb disks read only. It will be a bridge between PC and USB disk (hard disk, stick, etc). PC will be able to read everything in usb disk but not able write. If there is no usb disk connected to the device it will not allow PC to detect itself.
If you think that it is possible to do it with beaglebone with or without linux, please guide me.

Thanks in advance,


The bbb supports the usb gadget driver that will provide access to the
local filesystems (emmc etc) via the mini-usb-b port. I'd imagine you could
modify this configuration to mount, as read-only, your eventual target
disk, which is plugged into the host-a usb port.

So it seems like this could be doable. I'd wonder what kind of performance
you might get.