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From: NRK <nrk@disroot.org>
To: musl@lists.openwall.com
Subject: Re: [musl] [C23 string conversion 1/3] C23: add the new memset_explicit function
Date: Sun, 28 May 2023 16:13:18 +0600	[thread overview]
Message-ID: <20230528101318.qewkay4z7s3bdj46@gen2.localdomain> (raw)
In-Reply-To: <b1a510c14f340b855a5900178e0191891751c8fa.1684932960.git.Jens.Gustedt@inria.fr>

Hi Jens,

On Fri, May 26, 2023 at 11:25:43AM +0200, Jens Gustedt wrote:
> By having a slow bytewise copy, we intent also to have predictable
> timing, such that we can avoid side-channel attacks.

I don't believe `volatile` provides any guarantee of emitting
constant-time operations (which can be CPU dependent). But even if it
happens to work out in practice, from a user/non-cryptographer's
perspective, I feel like claims like "avoiding side-channel attacks"
needs much more substantiation than just slapping a `volatile` on top of
a pointer.

But as I've said, not a cryptographer, so please *do* correct me if I'm
wrong or am being unnecessarily paranoid.

P.S: even if the claim is correct, other major implementation would also
have to agree to provide such guarantee in a documented manner for this
to be useful to the users. Otherwise, users will have to resort to
hard-coded libc checks or simply not rely on this property at all.

- NRK

  parent reply	other threads:[~2023-05-28 10:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-26  9:25 [musl] [C23 string conversion 0/3] Jens Gustedt
2023-05-26  9:25 ` [musl] [C23 string conversion 1/3] C23: add the new memset_explicit function Jens Gustedt
2023-05-26  9:52   ` Joakim Sindholt
2023-05-26 10:18     ` Jₑₙₛ Gustedt
2023-05-26 20:16       ` Rich Felker
2023-05-26 20:35         ` Jₑₙₛ Gustedt
2023-05-26 20:57           ` Rich Felker
2023-05-27  6:49             ` Jₑₙₛ Gustedt
2023-05-27 13:52               ` Rich Felker
2023-05-28 10:13   ` NRK [this message]
2023-05-29  7:48     ` Jₑₙₛ Gustedt
2023-05-26  9:25 ` [musl] [C23 string conversion 2/3] C23: implement the c8rtomb and mbrtoc8 functions Jens Gustedt
2023-05-26  9:25 ` [musl] [C23 string conversion 3/3] C23: add the new include guards for string.h and wchar.h Jens Gustedt

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