Date:   Tue, 2 Apr 2019 19:15:57 +0300
From:   Vitaly Chikunov <vt@altlinux.org>
To:     Eric Biggers <ebiggers@kernel.org>, linux-crypto@vger.kernel.org
Subject: Re: [RFC/RFT PATCH 09/18] crypto: streebog - fix unaligned memory
 accesses
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        linux-crypto@vger.kernel.org
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 <20190331200428.26597-10-ebiggers@kernel.org>
 <20190331214717.4erxk2racxphfbha@altlinux.org>
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Eric,

On Mon, Apr 01, 2019 at 12:47:19AM +0300, Vitaly Chikunov wrote:
> On Sun, Mar 31, 2019 at 01:04:19PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Don't cast the data buffer directly to streebog_uint512, as this
> > violates alignment rules.
> > 
> > Fixes: fe18957e8e87 ("crypto: streebog - add Streebog hash function")
> > Cc: Vitaly Chikunov <vt@altlinux.org>
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > ---
> >  crypto/streebog_generic.c | 25 +++++++++++++------------
> >  include/crypto/streebog.h |  5 ++++-
> >  2 files changed, 17 insertions(+), 13 deletions(-)
> > 
> > diff --git a/crypto/streebog_generic.c b/crypto/streebog_generic.c
> > index 5a2eafed9c29f..b82fc3d79aa15 100644
> > --- a/crypto/streebog_generic.c
> > +++ b/crypto/streebog_generic.c
> > @@ -996,7 +996,7 @@ static void streebog_add512(const struct streebog_uint512 *x,
> >  
> >  static void streebog_g(struct streebog_uint512 *h,
> >  		       const struct streebog_uint512 *N,
> > -		       const u8 *m)
> > +		       const struct streebog_uint512 *m)
> >  {
> >  	struct streebog_uint512 Ki, data;
> >  	unsigned int i;
> > @@ -1005,7 +1005,7 @@ static void streebog_g(struct streebog_uint512 *h,
> >  
> >  	/* Starting E() */
> >  	Ki = data;
> > -	streebog_xlps(&Ki, (const struct streebog_uint512 *)&m[0], &data);
> > +	streebog_xlps(&Ki, m, &data);
> >  
> >  	for (i = 0; i < 11; i++)
> >  		streebog_round(i, &Ki, &data);
> > @@ -1015,16 +1015,19 @@ static void streebog_g(struct streebog_uint512 *h,
> >  	/* E() done */
> >  
> >  	streebog_xor(&data, h, &data);
> > -	streebog_xor(&data, (const struct streebog_uint512 *)&m[0], h);
> > +	streebog_xor(&data, m, h);
> >  }
> >  
> >  static void streebog_stage2(struct streebog_state *ctx, const u8 *data)
> >  {
> > -	streebog_g(&ctx->h, &ctx->N, data);
> > +	struct streebog_uint512 m;
> > +
> > +	memcpy(&m, data, sizeof(m));
> > +
> > +	streebog_g(&ctx->h, &ctx->N, &m);
> >  
> >  	streebog_add512(&ctx->N, &buffer512, &ctx->N);
> > -	streebog_add512(&ctx->Sigma, (const struct streebog_uint512 *)data,
> > -			&ctx->Sigma);
> > +	streebog_add512(&ctx->Sigma, &m, &ctx->Sigma);
> >  }
> 
> As I understand, this is the actual fix.

Probably, even better would be to use CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
to optimize out memcpy() for such architectures.

Thanks,

> Reviewed-by: Vitaly Chikunov <vt@altlinux.org>
> 
> Thanks much!
> 
> >  
> >  static void streebog_stage3(struct streebog_state *ctx)
> > @@ -1034,13 +1037,11 @@ static void streebog_stage3(struct streebog_state *ctx)
> >  	buf.qword[0] = cpu_to_le64(ctx->fillsize << 3);
> >  	streebog_pad(ctx);
> >  
> > -	streebog_g(&ctx->h, &ctx->N, (const u8 *)&ctx->buffer);
> > +	streebog_g(&ctx->h, &ctx->N, &ctx->m);
> >  	streebog_add512(&ctx->N, &buf, &ctx->N);
> > -	streebog_add512(&ctx->Sigma,
> > -			(const struct streebog_uint512 *)&ctx->buffer[0],
> > -			&ctx->Sigma);
> > -	streebog_g(&ctx->h, &buffer0, (const u8 *)&ctx->N);
> > -	streebog_g(&ctx->h, &buffer0, (const u8 *)&ctx->Sigma);
> > +	streebog_add512(&ctx->Sigma, &ctx->m, &ctx->Sigma);
> > +	streebog_g(&ctx->h, &buffer0, &ctx->N);
> > +	streebog_g(&ctx->h, &buffer0, &ctx->Sigma);
> >  	memcpy(&ctx->hash, &ctx->h, sizeof(struct streebog_uint512));
> >  }
> >  
> > diff --git a/include/crypto/streebog.h b/include/crypto/streebog.h
> > index 856e32af86574..cae1b4a019713 100644
> > --- a/include/crypto/streebog.h
> > +++ b/include/crypto/streebog.h
> > @@ -23,7 +23,10 @@ struct streebog_uint512 {
> >  };
> >  
> >  struct streebog_state {
> > -	u8 buffer[STREEBOG_BLOCK_SIZE];
> > +	union {
> > +		u8 buffer[STREEBOG_BLOCK_SIZE];
> > +		struct streebog_uint512 m;
> > +	};
> >  	struct streebog_uint512 hash;
> >  	struct streebog_uint512 h;
> >  	struct streebog_uint512 N;
> > -- 
> > 2.21.0