Re: [PATCH 4/6] crypto: sha256 - Use get_unaligned_be32 to get input, memzero_explicit

Eric Biggers
2019-08-17T05:37:31Z

On Fri, Aug 16, 2019 at 11:16:09PM +0200, Hans de Goede wrote:
> Use get_unaligned_be32 in the lib/crypto/sha256.c sha256_transform()
> implementation so that it can be used with unaligned buffers too,
> making it more generic.
>
> And use memzero_explicit for better clearing of sensitive data.
>
> Note unlike other patches in this series this commit actually makes
> functional changes to the sha256 code as used by the purgatory code.
>
> This fully aligns the lib/crypto/sha256.c sha256_transform()
> implementation with the one from crypto/sha256_generic.c allowing us
> to remove the latter in further patches in this series.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> lib/crypto/sha256.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
> index b8114028d06f..09a435d845fc 100644
> --- a/lib/crypto/sha256.c
> +++ b/lib/crypto/sha256.c
> @@ -14,7 +14,7 @@
> #include <linux/bitops.h>
> #include <linux/string.h>
> #include <crypto/sha256.h>
> -#include <asm/byteorder.h>
> +#include <asm/unaligned.h>
>
> static inline u32 Ch(u32 x, u32 y, u32 z)
> {
> @@ -33,7 +33,7 @@ static inline u32 Maj(u32 x, u32 y, u32 z)
>
> static inline void LOAD_OP(int I, u32 *W, const u8 *input)
> {
> - W[I] = __be32_to_cpu(((__be32 *)(input))[I]);
> + W[I] = get_unaligned_be32((__u32 *)input + I);
> }
>
> static inline void BLEND_OP(int I, u32 *W)
> @@ -201,7 +201,7 @@ static void sha256_transform(u32 *state, const u8 *input)
>
> /* clear any sensitive info... */
> a = b = c = d = e = f = g = h = t1 = t2 = 0;
> - memset(W, 0, 64 * sizeof(u32));
> + memzero_explicit(W, 64 * sizeof(u32));
> }
>

There's also an unaligned access in sha256_final() which needs to be fixed.

- Eric