Re: input/eventX permissions, force feedback

From: Andrey Borzenkov
Date: Tue Jul 18 2006 - 12:49:21 EST

Dmitry Torokhov wrote:

> Hi Anssi,
> On 7/18/06, Anssi Hannula <anssi.hannula@xxxxxxxxx> 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.

You could also have udev create specific symlink for such devices,
say /dev/input/ff* and make a rule for pam_console to change their
permissions. That is finally what is done e.g. for CD-ROMs (cdrom ->


> Another solution would be to relax permissions if user is also console
> owner (home box installation).
> One thing is for sure - I do not like #3 at all ;)

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