Messages in this thread | | | Date | Sat, 31 Jul 2004 16:02:57 -0500 | From | Zinx Verituse <> | Subject | Re: ide-cd problems |
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On Sat, Jul 31, 2004 at 10:00:36PM +0200, Jens Axboe wrote: > On Sat, Jul 31 2004, Zinx Verituse wrote: > > On Sat, Jul 31, 2004 at 05:36:10PM +0200, Jens Axboe wrote: > > > On Fri, Jul 30 2004, Zinx Verituse wrote: > > > > I'm going to bump this topic a bit, since it's been a while.. > > > > There are still some issues with ide-cd's SG_IO, listed from > > > > most important as percieved by me to least: > > > > > > > > * Read-only access grants you the ability to write/blank media in the drive > > > > * (with above) You can open the device only in read-only mode. > > > > > > That's by design. Search linux-scsi or this list for why that is so. > > > > The only thing I can find on the linux-scsi list is refering to sg > > devices, which are on a different device node from the non-generic > > device. This means you can still allow users read access to the disk > > without allowing them to send random commands to the disk -- this isn't > > currently possible with the IDE interface, since the device with > > generic access is the same as the one with the original read/cdrom > > commands access. > > > > As it is, it's impossible grant users read-only access to an IDE cd-rom > > without allowing them to do things like replacing the firmware with a > > malicious/non-working one. > > > > Generic access allowing such things is fine; but only if we can grant > > non-generic access without granting generic access. > > If you want it to work that way, you have the have a pass-through filter > in the kernel knowing what commands are out there (including vendor > specific ones). That's just too ugly and not really doable or > maintainable, sorry. > > If you have access to issue ioctls to the device, you have access to > send it arbitrary commands - period.
I don't believe command filtering is neccessary, since all of the ide-cd ioctls are still there (ioctls that allow playing, reading, etc) Only the SG_IO ioctl itself would have to be checked (i.e., not each individual command available with SG_IO, just the overall ioctl itself, categorizing all of SG_IO more or less as raw IO. If this isn't doable with the current design, then the ide-cd interface should at least be very conspicuously documented as being extremely insecure as far as "read" access is concerned, as I know I wouldn't expect users to be able to overwrite my drive's firmware simply by granting the read access.
-- Zinx Verituse http://zinx.xmms.org/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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