linux-kernel - Re: [PATCH 1/5] crypto: chacha20 - Fix unaligned access when loading constants

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAKv+Gu8gQF2CpH_n5ox5KjFzJstnayEk5QAuqVZ5dO7hZ+qMfg@mail.gmail.com>
Date:   Wed, 22 Nov 2017 20:26:31 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Theodore Ts'o" <tytso@....edu>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Martin Willi <martin@...ongswan.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH 1/5] crypto: chacha20 - Fix unaligned access when loading constants

On 22 November 2017 at 19:51, Eric Biggers <ebiggers3@...il.com> wrote:
> From: Eric Biggers <ebiggers@...gle.com>
>
> The four 32-bit constants for the initial state of ChaCha20 were loaded
> from a char array which is not guaranteed to have the needed alignment.
>
> Fix it by just assigning the constants directly instead.
>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

I'm not thrilled about the open coded hex numbers but I don't care
enough to object.

Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

> ---
>  crypto/chacha20_generic.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/crypto/chacha20_generic.c b/crypto/chacha20_generic.c
> index 4a45fa4890c0..ec84e7837aac 100644
> --- a/crypto/chacha20_generic.c
> +++ b/crypto/chacha20_generic.c
> @@ -41,12 +41,10 @@ static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
>
>  void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
>  {
> -       static const char constant[16] = "expand 32-byte k";
> -
> -       state[0]  = le32_to_cpuvp(constant +  0);
> -       state[1]  = le32_to_cpuvp(constant +  4);
> -       state[2]  = le32_to_cpuvp(constant +  8);
> -       state[3]  = le32_to_cpuvp(constant + 12);
> +       state[0]  = 0x61707865; /* "expa" */
> +       state[1]  = 0x3320646e; /* "nd 3" */
> +       state[2]  = 0x79622d32; /* "2-by" */
> +       state[3]  = 0x6b206574; /* "te k" */
>         state[4]  = ctx->key[0];
>         state[5]  = ctx->key[1];
>         state[6]  = ctx->key[2];
> --
> 2.15.0.448.gf294e3d99a-goog
>