Re: [PATCH v3 07/10] cryptodisk: Replace some literals with constants in grub_cryptodisk_endecrypt.

[Patrick Steinhardt]

On Mon, Oct 26, 2020 at 06:25:53PM +0000, Glenn Washburn wrote:
> Oct 23, 2020 1:00:59 PM Patrick Steinhardt <ps@pks.im>:
> 
> > On Mon, Oct 19, 2020 at 06:09:55PM -0500, Glenn Washburn 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)
> >
> > Hum. I'd rather name this `GRUB_TYPE_BITS`, as the current name implies
> > that we only get a single bit. Other than that the change looks good to
> > me and I agree that it helps readability.
> >
> > Patrick
> 
> Yes, I would've liked to also, but I decided to stick with the naming
> convention as can be seen in the definition of GRUB_CHAR_BIT above it.
> Should there be a separate patch renaming GRUB_CHAR_BIT also?

Nah, your naming makes sense in that context. Let's keep it as-is in
this patch.

Patrick

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