linux-kernel - Re: [PATCH] crypto: ccree: fix iv copying for small buffers

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Message-ID: <20180619142713.dzipyarpb23a7qne@gondor.apana.org.au>
Date:   Tue, 19 Jun 2018 22:27:13 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Gilad Ben-Yossef <gilad@...yossef.com>
Cc:     "David S. Miller" <davem@...emloft.net>, hadar.gat@....com,
        Ofir Drang <ofir.drang@....com>, stable@...r.kernel.org,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: ccree: fix iv copying for small buffers

On Sun, Jun 17, 2018 at 01:06:42PM +0300, Gilad Ben-Yossef wrote:
>
> It was ctr(aes). I wrongly assumed that we are supposed to unconditionally
> copy
> the cipher-text block post operation and let the caller do with it what it
> wants and so the
> code now does that for all cipher operations unconditionally.

For CTR it doesn't matter whether the last block is less than a
block, you should still increment the counter.

> So what is a good description of what we are supposed to provide in that
> field post operation?
> The next IV? but as you stated, that is not necessarily useful for all
> ciphers.

When in doubt, please refer to the generic implementation.  If
that is still unclear or if it seems wrong, please post to the
list.

Cheers,
-- 
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