Date:   Mon, 1 Apr 2019 00:47:19 +0300
From:   Vitaly Chikunov <vt@altlinux.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     linux-crypto@vger.kernel.org
Subject: Re: [RFC/RFT PATCH 09/18] crypto: streebog - fix unaligned memory
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        linux-crypto@vger.kernel.org
References: <20190331200428.26597-1-ebiggers@kernel.org>
 <20190331200428.26597-10-ebiggers@kernel.org>
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Eric,

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.

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