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SubjectRe: [PATCH 2/5] crypto: chacha20 - Use unaligned access macros when loading key and IV
On 22 November 2017 at 19:51, Eric Biggers <ebiggers3@gmail.com> wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> The generic ChaCha20 implementation has a cra_alignmask of 3, which
> ensures that the key passed into crypto_chacha20_setkey() and the IV
> passed into crypto_chacha20_init() are 4-byte aligned. However, these
> functions are also called from the ARM and ARM64 implementations of
> ChaCha20, which intentionally do not have a cra_alignmask set. This is
> broken because 32-bit words are being loaded from potentially-unaligned
> buffers without the unaligned access macros.
>
> Fix it by using the unaligned access macros when loading the key and IV.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

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

> ---
> crypto/chacha20_generic.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/crypto/chacha20_generic.c b/crypto/chacha20_generic.c
> index ec84e7837aac..b5a10ebf1b82 100644
> --- a/crypto/chacha20_generic.c
> +++ b/crypto/chacha20_generic.c
> @@ -9,16 +9,12 @@
> * (at your option) any later version.
> */
>
> +#include <asm/unaligned.h>
> #include <crypto/algapi.h>
> #include <crypto/chacha20.h>
> #include <crypto/internal/skcipher.h>
> #include <linux/module.h>
>
> -static inline u32 le32_to_cpuvp(const void *p)
> -{
> - return le32_to_cpup(p);
> -}
> -
> static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
> unsigned int bytes)
> {
> @@ -53,10 +49,10 @@ void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
> state[9] = ctx->key[5];
> state[10] = ctx->key[6];
> state[11] = ctx->key[7];
> - state[12] = le32_to_cpuvp(iv + 0);
> - state[13] = le32_to_cpuvp(iv + 4);
> - state[14] = le32_to_cpuvp(iv + 8);
> - state[15] = le32_to_cpuvp(iv + 12);
> + state[12] = get_unaligned_le32(iv + 0);
> + state[13] = get_unaligned_le32(iv + 4);
> + state[14] = get_unaligned_le32(iv + 8);
> + state[15] = get_unaligned_le32(iv + 12);
> }
> EXPORT_SYMBOL_GPL(crypto_chacha20_init);
>
> @@ -70,7 +66,7 @@ int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
> return -EINVAL;
>
> for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
> - ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
> + ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
>
> return 0;
> }
> --
> 2.15.0.448.gf294e3d99a-goog
>

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