[dm-devel] [PATCH v2] hex2bin: make the function hex_to_bin constant-time

[Milan Broz]

On 04/05/2022 11:20, Andy Shevchenko wrote:
> On Wed, May 04, 2022 at 04:57:35AM -0400, Mikulas Patocka wrote:
>> On Wed, 4 May 2022, Stafford Horne wrote:
>>> On Mon, Apr 25, 2022 at 08:07:48AM -0400, Mikulas Patocka wrote:
> 
> ...
> 
>>> Just a heads up it seems this patch is causing some instability with crypto self
>>> tests on OpenRISC when using a PREEMPT kernel (no SMP).
>>>
>>> This was reported by Jason A. Donenfeld as it came up in wireguard testing.
>>>
>>> I am trying to figure out if this is an OpenRISC PREEMPT issue or something
>>> else.
> 
>> That patch is so simple that I can't imagine how could it break the
>> curve25519 test. Are you sure that you bisected it correctly?
> 
> Can you provide a test cases for hex_to_bin()?

BTW we use exactly the same code from Mikulas in cryptsetup now (actually the report
was initiated from here :) and I added some tests for this code,
you can probably adapt it (we just use generic wrapper around it):

https://gitlab.com/cryptsetup/cryptsetup/-/commit/2d8cdb2e356d187658efa6efc7bfa146be5d3f60#d9c94cde02e4509f6d12c3edd40f8a9138696807_0_176

(it calls this: https://gitlab.com/cryptsetup/cryptsetup/-/commit/ff14c17de794fe85299d90e34e12a677e6148b71 )

I do not have OpenRISC available, but it would be interesting to run cryptsetup/tests/vectors-test there...

Milan