* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
@ 2016-10-22 13:53 Corentin Labbe
2016-10-24 20:10 ` Maxime Ripard
0 siblings, 1 reply; 7+ messages in thread
From: Corentin Labbe @ 2016-10-22 13:53 UTC (permalink / raw)
To: linux-arm-kernel
Since SID's content is constant over reboot, it must not be used
as source of randomness.
This patch remove the use of SID content as source of randomness.
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
---
drivers/nvmem/sunxi_sid.c | 21 ---------------------
1 file changed, 21 deletions(-)
diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c
index 1567ccc..c82d5d1 100644
--- a/drivers/nvmem/sunxi_sid.c
+++ b/drivers/nvmem/sunxi_sid.c
@@ -21,8 +21,6 @@
#include <linux/nvmem-provider.h>
#include <linux/of.h>
#include <linux/platform_device.h>
-#include <linux/slab.h>
-#include <linux/random.h>
static struct nvmem_config econfig = {
.name = "sunxi-sid",
@@ -70,8 +68,6 @@ static int sunxi_sid_probe(struct platform_device *pdev)
struct resource *res;
struct nvmem_device *nvmem;
struct sunxi_sid *sid;
- int ret, i, size;
- char *randomness;
sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
if (!sid)
@@ -82,7 +78,6 @@ static int sunxi_sid_probe(struct platform_device *pdev)
if (IS_ERR(sid->base))
return PTR_ERR(sid->base);
- size = resource_size(res) - 1;
econfig.size = resource_size(res);
econfig.dev = dev;
econfig.reg_read = sunxi_sid_read;
@@ -91,25 +86,9 @@ static int sunxi_sid_probe(struct platform_device *pdev)
if (IS_ERR(nvmem))
return PTR_ERR(nvmem);
- randomness = kzalloc(sizeof(u8) * (size), GFP_KERNEL);
- if (!randomness) {
- ret = -EINVAL;
- goto err_unreg_nvmem;
- }
-
- for (i = 0; i < size; i++)
- randomness[i] = sunxi_sid_read_byte(sid, i);
-
- add_device_randomness(randomness, size);
- kfree(randomness);
-
platform_set_drvdata(pdev, nvmem);
return 0;
-
-err_unreg_nvmem:
- nvmem_unregister(nvmem);
- return ret;
}
static int sunxi_sid_remove(struct platform_device *pdev)
--
2.7.3
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
2016-10-22 13:53 [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness Corentin Labbe
@ 2016-10-24 20:10 ` Maxime Ripard
2016-10-25 5:38 ` LABBE Corentin
0 siblings, 1 reply; 7+ messages in thread
From: Maxime Ripard @ 2016-10-24 20:10 UTC (permalink / raw)
To: linux-arm-kernel
On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote:
> Since SID's content is constant over reboot,
That's not true, at least not across all the Allwinner SoCs, and
especially not on the A10 and A20 that this driver supports.
> it must not be used as source of randomness.
And I don't think that's true either. A constant entropy provider will
not add any entropy, but will not remove any, would it?
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
2016-10-24 20:10 ` Maxime Ripard
@ 2016-10-25 5:38 ` LABBE Corentin
2016-10-25 7:06 ` Jean-Francois Moine
2016-10-25 13:26 ` Maxime Ripard
0 siblings, 2 replies; 7+ messages in thread
From: LABBE Corentin @ 2016-10-25 5:38 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Oct 24, 2016 at 10:10:20PM +0200, Maxime Ripard wrote:
> On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote:
> > Since SID's content is constant over reboot,
>
> That's not true, at least not across all the Allwinner SoCs, and
> especially not on the A10 and A20 that this driver supports.
>
On my cubieboard2 (A20)
hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000200
cubiedev ~ # reboot
cubiedev ~ # hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000200
So clearly for me its constant.
> > it must not be used as source of randomness.
>
> And I don't think that's true either. A constant entropy provider will
> not add any entropy, but will not remove any, would it?
I cced linux-crypto at the begining for confirmation on that.
But the problem is increased as a part of the content is predicatable over same type of device (at least the thirst bytes and all the zeros).
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
2016-10-25 5:38 ` LABBE Corentin
@ 2016-10-25 7:06 ` Jean-Francois Moine
2016-10-28 12:37 ` LABBE Corentin
2016-10-25 13:26 ` Maxime Ripard
1 sibling, 1 reply; 7+ messages in thread
From: Jean-Francois Moine @ 2016-10-25 7:06 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, 25 Oct 2016 07:38:55 +0200
LABBE Corentin <clabbe.montjoie@gmail.com> wrote:
> > On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote:
> > > Since SID's content is constant over reboot,
> >
> > That's not true, at least not across all the Allwinner SoCs, and
> > especially not on the A10 and A20 that this driver supports.
> >
>
> On my cubieboard2 (A20)
> hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000200
> cubiedev ~ # reboot
> cubiedev ~ # hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000200
>
> So clearly for me its constant.
Even after power off/power on?
--
Ken ar c'henta? | ** Breizh ha Linux atav! **
Jef | http://moinejf.free.fr/
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
2016-10-25 7:06 ` Jean-Francois Moine
@ 2016-10-28 12:37 ` LABBE Corentin
0 siblings, 0 replies; 7+ messages in thread
From: LABBE Corentin @ 2016-10-28 12:37 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Oct 25, 2016 at 09:06:34AM +0200, Jean-Francois Moine wrote:
> On Tue, 25 Oct 2016 07:38:55 +0200
> LABBE Corentin <clabbe.montjoie@gmail.com> wrote:
>
> > > On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote:
> > > > Since SID's content is constant over reboot,
> > >
> > > That's not true, at least not across all the Allwinner SoCs, and
> > > especially not on the A10 and A20 that this driver supports.
> > >
> >
> > On my cubieboard2 (A20)
> > hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> > 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000200
> > cubiedev ~ # reboot
> > cubiedev ~ # hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> > 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000200
> >
> > So clearly for me its constant.
>
> Even after power off/power on?
Yes, even after remove of any power supply.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
2016-10-25 5:38 ` LABBE Corentin
2016-10-25 7:06 ` Jean-Francois Moine
@ 2016-10-25 13:26 ` Maxime Ripard
2016-11-10 15:14 ` Corentin Labbe
1 sibling, 1 reply; 7+ messages in thread
From: Maxime Ripard @ 2016-10-25 13:26 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Oct 25, 2016 at 07:38:55AM +0200, LABBE Corentin wrote:
> On Mon, Oct 24, 2016 at 10:10:20PM +0200, Maxime Ripard wrote:
> > On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote:
> > > Since SID's content is constant over reboot,
> >
> > That's not true, at least not across all the Allwinner SoCs, and
> > especially not on the A10 and A20 that this driver supports.
> >
>
> On my cubieboard2 (A20)
> hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000200
> cubiedev ~ # reboot
> cubiedev ~ # hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000200
>
> So clearly for me its constant.
It's constant across reboots, but not across devices. Each device have
a different SID content, therefore it's a relevant source of entropy
in the system.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness
2016-10-25 13:26 ` Maxime Ripard
@ 2016-11-10 15:14 ` Corentin Labbe
0 siblings, 0 replies; 7+ messages in thread
From: Corentin Labbe @ 2016-11-10 15:14 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Oct 25, 2016 at 03:26:48PM +0200, Maxime Ripard wrote:
> On Tue, Oct 25, 2016 at 07:38:55AM +0200, LABBE Corentin wrote:
> > On Mon, Oct 24, 2016 at 10:10:20PM +0200, Maxime Ripard wrote:
> > > On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote:
> > > > Since SID's content is constant over reboot,
> > >
> > > That's not true, at least not across all the Allwinner SoCs, and
> > > especially not on the A10 and A20 that this driver supports.
> > >
> >
> > On my cubieboard2 (A20)
> > hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> > 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000200
> > cubiedev ~ # reboot
> > cubiedev ~ # hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem
> > 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur|
> > 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000200
> >
> > So clearly for me its constant.
>
> It's constant across reboots, but not across devices. Each device have
> a different SID content, therefore it's a relevant source of entropy
> in the system.
>
Not the 3 leading digit and not the tailing zeros which are the same accross device.
So only 50% of data are really different accross devices.
Perhaps a "random-range" property could be used ?
Herbert, does it is safe to add that 50% duplicate content via add_device_randomness() ?
Reading add_device_randomness doc, it seems finally it is safe, but if you could confirm it.
Regards
^ permalink raw reply [flat|nested] 7+ messages in thread
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2016-10-22 13:53 [PATCH] nvmem: sunxi-sid: SID content is not a valid source of randomness Corentin Labbe
2016-10-24 20:10 ` Maxime Ripard
2016-10-25 5:38 ` LABBE Corentin
2016-10-25 7:06 ` Jean-Francois Moine
2016-10-28 12:37 ` LABBE Corentin
2016-10-25 13:26 ` Maxime Ripard
2016-11-10 15:14 ` Corentin Labbe
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