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SubjectRe: [PATCH 1/5] crypto: chacha20 - Fix unaligned access when loading constants
On 22 November 2017 at 19:51, Eric Biggers <ebiggers3@gmail.com> wrote:
> From: Eric Biggers <ebiggers@google.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@google.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@linaro.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
>

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