linux-kernel - Re: [PATCH] crypto: gcm

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Message-ID: <20190530142734.qlhgzeal22zxfhk5@gondor.apana.org.au>
Date:   Thu, 30 May 2019 22:27:34 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Iuliana Prodan <iuliana.prodan@....com>,
        Eric Biggers <ebiggers@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Horia Geanta <horia.geanta@....com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH] crypto: gcm - fix cacheline sharing

On Thu, May 30, 2019 at 03:55:07PM +0200, Ard Biesheuvel wrote:
>
> > Would this work?

I see.  You need to preserve the original IV.

> > diff --git a/drivers/crypto/caam/caamalg.c b/drivers/crypto/caam/caamalg.c
> > index c0ece44f303b..2ef2f76a3cb8 100644
> > --- a/drivers/crypto/caam/caamalg.c
> > +++ b/drivers/crypto/caam/caamalg.c
> > @@ -1832,22 +1832,25 @@ static int skcipher_decrypt(struct
> > skcipher_request *req)
> >         struct caam_ctx *ctx = crypto_skcipher_ctx(skcipher);
> >         int ivsize = crypto_skcipher_ivsize(skcipher);
> >         struct device *jrdev = ctx->jrdev;
> > +       u8 out_iv[AES_BLOCK_SIZE];
> >         u32 *desc;
> >         int ret = 0;
> >
> > -       /* allocate extended descriptor */
> > -       edesc = skcipher_edesc_alloc(req, DESC_JOB_IO_LEN * CAAM_CMD_SZ);
> > -       if (IS_ERR(edesc))
> > -               return PTR_ERR(edesc);
> > -
> >         /*
> >          * The crypto API expects us to set the IV (req->iv) to the last
> >          * ciphertext block.
> >          */
> >         if (ivsize)
> > -               scatterwalk_map_and_copy(req->iv, req->src, req->cryptlen -
> > +               scatterwalk_map_and_copy(out_iv, req->src, req->cryptlen -
> >                                          ivsize, ivsize, 0);
> >
> > +       /* allocate extended descriptor */
> > +       edesc = skcipher_edesc_alloc(req, DESC_JOB_IO_LEN * CAAM_CMD_SZ);
> > +       if (IS_ERR(edesc))
> > +               return PTR_ERR(edesc);
> > +
> > +       memcpy(req->iv, out_iv, ivsize);
> > +
> >         /* Create and submit job descriptor*/
> >         init_skcipher_job(req, edesc, false);
> >         desc = edesc->hw_desc;
> 
> Umm never mind
> 
> /me hides in shame

So why doesn't this work?

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