* USB HID devices not linked to RNG
@ 2015-09-07 0:10 Stephan Mueller
2015-09-07 0:12 ` Stephan Mueller
0 siblings, 1 reply; 6+ messages in thread
From: Stephan Mueller @ 2015-09-07 0:10 UTC (permalink / raw)
To: linux-crypto, linux-input; +Cc: tytso
Hi,
While analyzing the entropy sources for the random number generator in
drivers/char/random.c, I saw that a USB mouse and a USB keyboard does trigger
the add_input_randomness function to be triggered.
Is that intended?
--
Ciao
Stephan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: USB HID devices not linked to RNG
2015-09-07 0:10 USB HID devices not linked to RNG Stephan Mueller
@ 2015-09-07 0:12 ` Stephan Mueller
2015-09-07 20:07 ` Mike Mestnik
0 siblings, 1 reply; 6+ messages in thread
From: Stephan Mueller @ 2015-09-07 0:12 UTC (permalink / raw)
To: linux-crypto; +Cc: linux-input, tytso
Am Montag, 7. September 2015, 02:10:16 schrieb Stephan Mueller:
Hi Stephan,
> Hi,
>
> While analyzing the entropy sources for the random number generator in
> drivers/char/random.c, I saw that a USB mouse and a USB keyboard does
> trigger the add_input_randomness function to be triggered.
I need to reread what I write :-)
I mean that the USB mouse and USB keyboard does *not* trigger the
add_input_randomness function.
>
> Is that intended?
--
Ciao
Stephan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: USB HID devices not linked to RNG
2015-09-07 0:12 ` Stephan Mueller
@ 2015-09-07 20:07 ` Mike Mestnik
2015-09-07 21:09 ` Stephan Mueller
0 siblings, 1 reply; 6+ messages in thread
From: Mike Mestnik @ 2015-09-07 20:07 UTC (permalink / raw)
To: Stephan Mueller; +Cc: linux-crypto, linux-input, tytso
This is just an off the wall guess. Wouldn't such entropy already be
collected at a lower level, like raw usb traffic?
On Sun, Sep 6, 2015 at 7:12 PM, Stephan Mueller <smueller@chronox.de> wrote:
> Am Montag, 7. September 2015, 02:10:16 schrieb Stephan Mueller:
>
> Hi Stephan,
>
>> Hi,
>>
>> While analyzing the entropy sources for the random number generator in
>> drivers/char/random.c, I saw that a USB mouse and a USB keyboard does
>> trigger the add_input_randomness function to be triggered.
>
> I need to reread what I write :-)
>
> I mean that the USB mouse and USB keyboard does *not* trigger the
> add_input_randomness function.
>
>>
>> Is that intended?
>
>
> --
> Ciao
> Stephan
> --
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: USB HID devices not linked to RNG
2015-09-07 20:07 ` Mike Mestnik
@ 2015-09-07 21:09 ` Stephan Mueller
2015-09-09 5:40 ` Dmitry Torokhov
0 siblings, 1 reply; 6+ messages in thread
From: Stephan Mueller @ 2015-09-07 21:09 UTC (permalink / raw)
To: Mike Mestnik; +Cc: linux-crypto, linux-input, tytso
Am Montag, 7. September 2015, 15:07:47 schrieb Mike Mestnik:
Hi Mike,
>This is just an off the wall guess. Wouldn't such entropy already be
>collected at a lower level, like raw usb traffic?
The RNG collects data from interrupts (that also covers normal PS/2 mice and
keyboards), block devices and HID (it hooks itself into the input layer).
So, raw USB traffic is not a source of entropy other than for the interrupts
the base PCI traffic would generate.
What I am wondering: isn't the USB mouse/keyboard support hooking into the
kernel's input layer?
Ciao
Stephan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: USB HID devices not linked to RNG
2015-09-07 21:09 ` Stephan Mueller
@ 2015-09-09 5:40 ` Dmitry Torokhov
2015-09-09 12:24 ` Stephan Mueller
0 siblings, 1 reply; 6+ messages in thread
From: Dmitry Torokhov @ 2015-09-09 5:40 UTC (permalink / raw)
To: Stephan Mueller
Cc: Mike Mestnik, linux-crypto, linux-input, Theodore Ts'o
On Mon, Sep 7, 2015 at 2:09 PM, Stephan Mueller <smueller@chronox.de> wrote:
> Am Montag, 7. September 2015, 15:07:47 schrieb Mike Mestnik:
>
> Hi Mike,
>
>>This is just an off the wall guess. Wouldn't such entropy already be
>>collected at a lower level, like raw usb traffic?
>
> The RNG collects data from interrupts (that also covers normal PS/2 mice and
> keyboards), block devices and HID (it hooks itself into the input layer).
>
> So, raw USB traffic is not a source of entropy other than for the interrupts
> the base PCI traffic would generate.
>
> What I am wondering: isn't the USB mouse/keyboard support hooking into the
> kernel's input layer?
All input devices add randomness, however I think for mouse
add_input_randomness() will drop majority of events since they are
likely have the same value (well, depends on which direction you are
moving the mouse)...
--
Dmitry
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: USB HID devices not linked to RNG
2015-09-09 5:40 ` Dmitry Torokhov
@ 2015-09-09 12:24 ` Stephan Mueller
0 siblings, 0 replies; 6+ messages in thread
From: Stephan Mueller @ 2015-09-09 12:24 UTC (permalink / raw)
To: Dmitry Torokhov
Cc: Mike Mestnik, linux-crypto, linux-input, Theodore Ts'o
Am Dienstag, 8. September 2015, 22:40:07 schrieb Dmitry Torokhov:
Hi Dmitry,
>
>All input devices add randomness, however I think for mouse
>add_input_randomness() will drop majority of events since they are
>likely have the same value (well, depends on which direction you are
>moving the mouse)...
I agree that such mechanism is present, but it is implemented by
add_input_randomness:
/* ignore autorepeat and the like */
if (value == last_value)
return;
So, when we install a probe at the entry into add_input_randomness, we should
see invocations.
The problem now is that add_input_randomness is not called at all.
Simply use the following code as a systemtap script, load it and move a USB
mouse or type on a USB keyboard:
probe kernel.function("add_input_randomness") {
printf("add_input_randomness triggered\n");
}
Expected behavior: tons of printouts should be received (as it is the case
with PS/2 mice and keyboards).
Actual behavior: no printout when moving USB HID.
Ciao
Stephan
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-09-09 12:24 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2015-09-07 0:10 USB HID devices not linked to RNG Stephan Mueller
2015-09-07 0:12 ` Stephan Mueller
2015-09-07 20:07 ` Mike Mestnik
2015-09-07 21:09 ` Stephan Mueller
2015-09-09 5:40 ` Dmitry Torokhov
2015-09-09 12:24 ` Stephan Mueller
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