Re: [PATCH v2 07/10] cryptodisk: Replace some literals with constants in grub_cryptodisk_endecrypt.

[Glenn Washburn]

Daniel, Patrick,

Have either of you had a chance to review this patch?  Daniel, this is
my interpretation of what you suggested earlier to remove constant
literals in this message:
https://lists.gnu.org/archive/html/grub-devel/2020-09/msg00069.html

I'm going to make a v3 patchset with Patrick's suggested changes.
Please reply to that patch.

Glenn

On Sat,  3 Oct 2020 17:55:31 -0500
Glenn Washburn <development@efficientek.com> wrote:

> This should improve readability of code by providing clues as to what
> the value represents.
> 
> Signed-off-by: Glenn Washburn <development@efficientek.com>
> ---
>  grub-core/disk/cryptodisk.c | 12 +++++++-----
>  include/grub/types.h        |  3 +++
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
> index 623f0f396..1a91c2d55 100644
> --- a/grub-core/disk/cryptodisk.c
> +++ b/grub-core/disk/cryptodisk.c
> @@ -297,19 +297,21 @@ grub_cryptodisk_endecrypt (struct
> grub_cryptodisk *dev, }
>         break;
>       case GRUB_CRYPTODISK_MODE_IV_BYTECOUNT64:
> -       iv[1] = grub_cpu_to_le32 (sector >> (32 -
> log_sector_size));
> +       /* The IV is the 64 bit byte offset of the sector. */
> +       iv[1] = grub_cpu_to_le32 (sector >> (GRUB_TYPE_BIT(iv[0])
> +                                            - log_sector_size));
>         iv[0] = grub_cpu_to_le32 ((sector << log_sector_size)
> -                                 & 0xFFFFFFFF);
> +                                 & GRUB_TYPE_MAX(iv[0]));
>         break;
>       case GRUB_CRYPTODISK_MODE_IV_BENBI:
>         {
>           grub_uint64_t num = (sector << dev->benbi_log) + 1;
> -         iv[sz - 2] = grub_cpu_to_be32 (num >> 32);
> -         iv[sz - 1] = grub_cpu_to_be32 (num & 0xFFFFFFFF);
> +         iv[sz - 2] = grub_cpu_to_be32 (num >>
> GRUB_TYPE_BIT(iv[0]));
> +         iv[sz - 1] = grub_cpu_to_be32 (num &
> GRUB_TYPE_MAX(iv[0])); }
>         break;
>       case GRUB_CRYPTODISK_MODE_IV_ESSIV:
> -       iv[0] = grub_cpu_to_le32 (sector & 0xFFFFFFFF);
> +       iv[0] = grub_cpu_to_le32 (sector & GRUB_TYPE_MAX(iv[0]));
>         err = grub_crypto_ecb_encrypt (dev->essiv_cipher, iv, iv,
>                                        dev->cipher->cipher->blocksize);
>         if (err)
> diff --git a/include/grub/types.h b/include/grub/types.h
> index 035a4b528..8b4267ebd 100644
> --- a/include/grub/types.h
> +++ b/include/grub/types.h
> @@ -319,4 +319,7 @@ static inline void grub_set_unaligned64 (void
> *ptr, grub_uint64_t val) 
>  #define GRUB_CHAR_BIT 8
>  
> +#define GRUB_TYPE_BIT(type) (sizeof(type) * GRUB_CHAR_BIT)
> +#define GRUB_TYPE_MAX(type) ((2 * ((1ULL << (GRUB_TYPE_BIT(type) -
> 1)) - 1)) + 1) +
>  #endif /* ! GRUB_TYPES_HEADER */