linux-kernel - Re: [v5 PATCH 7/7] crypto: stm32 - Save and restore between each request

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Date:   Wed, 8 Mar 2023 17:13:58 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Lionel Debieve <lionel.debieve@...s.st.com>,
        Li kunyu <kunyu@...china.com>, davem@...emloft.net,
        linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com, mcoquelin.stm32@...il.com
Subject: Re: [v5 PATCH 7/7] crypto: stm32 - Save and restore between each
 request

On Wed, Mar 08, 2023 at 10:05:14AM +0100, Linus Walleij wrote:
>
> So for Ux500 at least I suppose it would be best to inhibit .import and
> .export when using HMAC with long keys unless I can figure out exactly
> what the issue is here. I wonder if that is possible?
> Or do I have to remove it from the HMAC algos altogether?

If the hardware is buggered it's not a big deal if it's just HMAC.
Because any HMAC hash can easily be broken down into three underlying
hash operations.

But let me digest your new information first, and see if we can
figure out a way to get it to work.  If not then we could just disable
hmac (unless we can get confirmation from stm32 hardware we should
just disable it for everything in stm32) and I'll fix the generic
hmac to actually work with hardware drivers.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt