* [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: srinivas.kandagatla, maxime.ripard, wens
Cc: linux-arm-kernel, linux-kernel, linux-crypto, Corentin Labbe
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
* Re: [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: Corentin Labbe
Cc: srinivas.kandagatla, wens, linux-kernel, linux-arm-kernel, linux-crypto
[-- Attachment #1: Type: text/plain, Size: 538 bytes --]
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
* Re: [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: Maxime Ripard
Cc: srinivas.kandagatla, wens, linux-kernel, linux-arm-kernel, linux-crypto
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
* Re: [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: LABBE Corentin
Cc: Maxime Ripard, wens, srinivas.kandagatla, linux-kernel,
linux-arm-kernel, linux-crypto
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'hentañ | ** Breizh ha Linux atav! **
Jef | http://moinejf.free.fr/
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [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: LABBE Corentin
Cc: srinivas.kandagatla, wens, linux-kernel, linux-arm-kernel, linux-crypto
[-- Attachment #1: Type: text/plain, Size: 1646 bytes --]
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
* Re: [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: Jean-Francois Moine
Cc: Maxime Ripard, wens, srinivas.kandagatla, linux-kernel,
linux-arm-kernel, linux-crypto
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
* Re: [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: Maxime Ripard, herbert
Cc: srinivas.kandagatla, wens, linux-kernel, linux-arm-kernel, linux-crypto
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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