Re: [PATCH v7 0/3] hwrng: add hwrng support for Rockchip RK3568

Dragan Simic
2024-07-17T03:35:15Z

Hello Chen-Yu,

On 2024-07-17 04:58, Chen-Yu Tsai wrote:
> On Wed, Jul 17, 2024 at 10:25 AM Daniel Golle <daniel@makrotopia.org>
> wrote:
>>
>> On Tue, Jul 16, 2024 at 07:19:35PM +0200, Diederik de Haas wrote:
>> > On Tuesday, 16 July 2024 18:53:43 CEST Diederik de Haas wrote:
>> > > rngtest: FIPS 140-2(2001-10-10) Long run: 0
>> >
>> > I don't know if it means something, but I noticed that I have
>> > ``Long run: 0`` with all my poor results,
>> > while Chen-Yu had ``Long run: 1``.
>> >
>> > Different SoC (RK3399), but Anand had ``Long run: 0`` too on their
>> > very poor result (100% failure):
>> > https://lore.kernel.org/linux-rockchip/CANAwSgTTzZOwBaR9zjJ5VMpxm5BydtW6rB2S7jg+dnoX8hAoWg@mail.gmail.com/
>>
>> The conclusions I draw from that rather ugly situation are:
>> - The hwrng should not be enabled by default, but it should by done
>> for each board on which it is known to work well.
>> - RK_RNG_SAMPLE_CNT as well as the assumed rng quality should be
>> defined in DT for each board:
>> * introduce new 'rochchip,rng-sample-count' property
>> * read 'quality' property already used for timeriomem_rng
>>
>> I will prepare a follow-up patch taking those conclusions into
>> account.
>>
>> Just for completeness, here my test result on the NanoPi R5C:
>> root@OpenWrt:~# cat /dev/hwrng | rngtest -c 1000
>> rngtest 6.15
>> Copyright (c) 2004 by Henrique de Moraes Holschuh
>> This is free software; see the source for copying conditions. There
>> is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
>> PARTICULAR PURPOSE.
>>
>> rngtest: starting FIPS tests...
>> rngtest: bits received from input: 20000032
>> rngtest: FIPS 140-2 successes: 875
>> rngtest: FIPS 140-2 failures: 125
>> rngtest: FIPS 140-2(2001-10-10) Monobit: 123
>> rngtest: FIPS 140-2(2001-10-10) Poker: 5
>> rngtest: FIPS 140-2(2001-10-10) Runs: 4
>> rngtest: FIPS 140-2(2001-10-10) Long run: 0
>> rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
>> rngtest: input channel speed: (min=85.171; avg=141.102;
>> max=4882812.500)Kibits/s
>> rngtest: FIPS tests speed: (min=17.809; avg=19.494;
>> max=60.169)Mibits/s
>> rngtest: Program run time: 139628605 microseconds
>
> I doubt this is per-board. The RNG is inside the SoC, so it
> could be a chip quality thing.

Totally agreed. I see no way how a board design could affect the
HWRNGs built into Rockchip SoCs. I even checked the RK3399 and
RK3566 Hardware Design Guides to be extra sure.

> On the RK3399 we also saw wildly varying results.

In my opinion, that qualifies the RK3399's HWRNG as unsuitable for
general use. Having a HWRNG that fails to pass the tests on _some_
units is simply not acceptable from the security standpoint.