Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201201194556.5220-1-ardb@kernel.org> <20201201215722.GA31941@gondor.apana.org.au>
In-Reply-To: <20201201215722.GA31941@gondor.apana.org.au>
From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Tue, 1 Dec 2020 23:01:57 +0100
Message-ID: <CAMj1kXHb27ugTWuQZhPD0DvjtgYC8t_pj+igqK7dNfh+WsUS4w@mail.gmail.com>
Subject: Re: [PATCH v2] crypto: aesni - add ccm(aes) algorithm implementation
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Ben Greear <greearb@candelatech.com>,
        Steve deRosier <derosier@cal-sierra.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, 1 Dec 2020 at 22:57, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Tue, Dec 01, 2020 at 08:45:56PM +0100, Ard Biesheuvel wrote:
> > Add ccm(aes) implementation from linux-wireless mailing list (see
> > http://permalink.gmane.org/gmane.linux.kernel.wireless.general/126679).
> >
> > This eliminates FPU context store/restore overhead existing in more
> > general ccm_base(ctr(aes-aesni),aes-aesni) case in MAC calculation.
> >
> > Suggested-by: Ben Greear <greearb@candelatech.com>
> > Co-developed-by: Steve deRosier <derosier@cal-sierra.com>
> > Signed-off-by: Steve deRosier <derosier@cal-sierra.com>
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> > v2: avoid the SIMD helper, as it produces an CRYPTO_ALG_ASYNC aead, which
> >     is not usable by the 802.11 ccmp driver
>
> Sorry, but this is not the way to go.  Please fix wireless to
> use the async interface instead.
>

This is not the first time this has come up. The point is that CCMP in
the wireless stack is not used in 99% of the cases, given that any
wifi hardware built in the last ~10 years can do it in hardware. Only
in exceptional cases, such as Ben's, is there a need for exercising
this interface.

Also, care to explain why we have synchronous AEADs in the first place
if they are not supposed to be used?