Messages in this thread | | | Date | Tue, 18 Jul 2006 10:14:48 -0400 | From | "Dmitry Torokhov" <> | Subject | Re: input/eventX permissions, force feedback |
| |
On 7/18/06, Anssi Hannula <anssi.hannula@gmail.com> wrote: > Dmitry Torokhov wrote: > > Hi Anssi, > > > > On 7/18/06, Anssi Hannula <anssi.hannula@gmail.com> wrote: > > > >> Currently most distributions have /dev/input/event* strictly as 0600 > >> root:root or 0640 root:root. The user logged in will not have rights to > >> the device, unlike /dev/input/js*, as he could read all passwords from > >> the keyboard device. > >> > >> This is a problem, because /dev/input/event* is used for force feedback > >> and should therefore be user-accessible. > >> > >> I can think of the following solutions to this problem: > >> > >> 1. Some creative udev rule to chmod /dev/input/event* less strictly when > >> it has a /dev/input/js* and is thus a gaming device. > >> > >> 2. Some creative udev rule to chmod /dev/input/event* more strictly when > >> it is a keyboard. > >> > >> 3. Have another force feedback interface also in /dev/input/js*. > >> > > > > You can do it in udev looking either at MODALIAS or at EV and ABS > > environment variables. I think it is pretty safe to say that a device > > with EV_ABS, EV_FF, ABS_X and ABS_Y is a force-feedback joystick-type > > device and not a keyboard. > > Okay, thanks. But I think it'd be more consistant if all devices that > have js* entries would have the relaxed perms in event*. Looking at > joydev.c, that seems to be devices where EV_ABS && (ABS_X || ABS_WHEEL > || ABS_THROTTLE) && !(EV_KEY && BTN_TOUCH). >
OK, you can do that too.
> There's another problem, too: > Some distros (Fedora, Mandriva...) don't use groups with /dev/input/jsX, > they use pam_console to chmod the device to the console owner. > Unfortunately, it allows to specify the permissions based on device file > names only. > > To solve this problem, I see two solutions: > > 1. Have the pam_console_apply program extended so that it can perform > more complex matches (but what kind of matches would those be?). > > 2. Have udev create symlinks like the following case: > /dev/input/event3 > /dev/input/js0 > /dev/input/jsevent0 => event3 > Then pam_console_apply could match jsevent[0-9]* and it would follow the > symlink, thus chowning event3 to the wanted user. > > Unfortunately neither look too good to me. Do you have any other ideas? >
I think this is really up to particular destribution to decide how they want to handle security/granting access. One could even imagine writing SELinux policies...
> > Another solution would be to relax permissions if user is also console > > owner (home box installation). > > I thought of that too, but I thought it's too big a security risk, as > it's not guaranteed that somebody else won't temporarily login on > another terminal. >
That is what you are doing with pam_console_apply, don't you?
-- Dmitry - 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/
| |