Re: [PATCH v6 5/6] cryptodisk: enable the backends to implement key files

[Glenn Washburn]

There are a couple issues with format string conversions that do not
currently cause building to fail.  However, they will when/if my strict
format string checking for grub_error is accepted.  Its best to fix
them anyway.

On Wed, 19 Aug 2020 17:09:13 +0200
Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org> wrote:

> From: John Lane <john@lane.uk.net>
> 
> Signed-off-by: John Lane <john@lane.uk.net>
> GNUtoo@cyberdimension.org: rebase, patch split, small fixes, commit
> message Signed-off-by: Denis 'GNUtoo' Carikli
> <GNUtoo@cyberdimension.org> Reviewed-by: Patrick Steinhardt
> <ps@pks.im> ---
> Changelog since v3:
> -------------------
> - Fixed the size formating with PRIuGRUB_SIZE
> - Added Reviewed-by
> 
> ChangeLog since v4:
> -------------------
> - Style fixes:
>   - Added missing space between function and '('
>   - Removed trailing backslashes in split strings
> 
> ChangeLog since v5:
> -------------------
> - No changes
> ---
>  grub-core/disk/cryptodisk.c | 87
> ++++++++++++++++++++++++++++++++++++- grub-core/disk/geli.c       |
> 7 +-- grub-core/disk/luks.c       |  7 ++-
>  grub-core/disk/luks2.c      |  7 +--
>  include/grub/cryptodisk.h   |  5 ++-
>  include/grub/file.h         |  2 +
>  6 files changed, 106 insertions(+), 9 deletions(-)
> 
> diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
> index 6ad2e486e..dd94736d3 100644
> --- a/grub-core/disk/cryptodisk.c
> +++ b/grub-core/disk/cryptodisk.c
> @@ -42,6 +42,9 @@ static const struct grub_arg_option options[] =
>      {"all", 'a', 0, N_("Mount all."), 0, 0},
>      {"boot", 'b', 0, N_("Mount all volumes with `boot' flag set."),
> 0, 0}, {"header", 'H', 0, N_("Read header from file"), 0,
> ARG_TYPE_STRING},
> +    {"keyfile", 'k', 0, N_("Key file"), 0, ARG_TYPE_STRING},
> +    {"keyfile-offset", 'O', 0, N_("Key file offset (bytes)"), 0,
> ARG_TYPE_INT},
> +    {"keyfile-size", 'S', 0, N_("Key file data size (bytes)"), 0,
> ARG_TYPE_INT}, {0, 0, 0, 0, 0, 0}
>    };
>  
> @@ -972,6 +975,8 @@ grub_util_cryptodisk_get_uuid (grub_disk_t disk)
>  static int check_boot, have_it;
>  static char *search_uuid;
>  static grub_file_t hdr;
> +static grub_uint8_t *key,
> keyfile_buffer[GRUB_CRYPTODISK_MAX_KEYFILE_SIZE]; +static
> grub_ssize_t key_size; 
>  static void
>  cryptodisk_close (grub_cryptodisk_t dev)
> @@ -1002,7 +1007,7 @@ grub_cryptodisk_scan_device_real (const char
> *name, grub_disk_t source) if (!dev)
>        continue;
>      
> -    err = cr->recover_key (source, dev, hdr);
> +    err = cr->recover_key (source, dev, hdr, key, key_size);
>      if (err)
>      {
>        cryptodisk_close (dev);
> @@ -1112,6 +1117,86 @@ grub_cmd_cryptomount (grub_extcmd_context_t
> ctxt, int argc, char **args) hdr = NULL;
>  
>    have_it = 0;
> +  key = NULL;
> +
> +  if (state[4].set) /* keyfile */
> +    {
> +      const char *p = NULL;
> +      grub_file_t keyfile;
> +      int keyfile_offset;
> +      grub_size_t requested_keyfile_size = 0;
> +
> +
> +      if (state[5].set) /* keyfile-offset */
> +     {
> +       keyfile_offset = grub_strtoul (state[5].arg, &p, 0);
> +
> +       if (grub_errno != GRUB_ERR_NONE)
> +         return grub_errno;
> +
> +       if (*p != '\0')
> +         return grub_error (GRUB_ERR_BAD_ARGUMENT,
> +                            N_("unrecognized number"));
> +     }
> +      else
> +     {
> +       keyfile_offset = 0;
> +     }
> +
> +      if (state[6].set) /* keyfile-size */
> +     {
> +       requested_keyfile_size = grub_strtoul (state[6].arg, &p,
> 0); +
> +       if (*p != '\0')
> +         return grub_error (GRUB_ERR_BAD_ARGUMENT,
> +                            N_("unrecognized number"));
> +
> +       if (grub_errno != GRUB_ERR_NONE)
> +         return grub_errno;
> +
> +       if (requested_keyfile_size >
> GRUB_CRYPTODISK_MAX_KEYFILE_SIZE)
> +         return grub_error (GRUB_ERR_OUT_OF_RANGE,
> +                           N_("Key file size exceeds maximum (%"
> +                              PRIuGRUB_SIZE ")\n"),
> +                           GRUB_CRYPTODISK_MAX_KEYFILE_SIZE);

The macro GRUB_CRYPTODISK_MAX_KEYFILE_SIZE gets expanded to an integer
literal which gets type cast as an int, but PRIuGRUB_SIZE expects long
or long long.  I'd say use "%d" instead of PRIuGRUB_SIZE because
GRUB_CRYPTODISK_MAX_KEYFILE_SIZE is a literal and won't change with
architecture.

> +       if (requested_keyfile_size == 0)
> +         return grub_error (GRUB_ERR_OUT_OF_RANGE,
> +                           N_("Key file size is 0\n"));
> +     }
> +
> +      keyfile = grub_file_open (state[4].arg,
> +
> GRUB_FILE_TYPE_CRYPTODISK_ENCRYPTION_KEY);
> +      if (!keyfile)
> +     return grub_errno;
> +
> +      if (grub_file_seek (keyfile, keyfile_offset) == (grub_off_t)-1)
> +     return grub_errno;
> +
> +      if (requested_keyfile_size)
> +     {
> +       if (requested_keyfile_size > (keyfile->size -
> keyfile_offset))
> +         return grub_error (GRUB_ERR_FILE_READ_ERROR,
> +                            N_("Keyfile is too small: "
> +                               "requested %" PRIuGRUB_SIZE "
> bytes, "
> +                               "but the file only has %"
> PRIuGRUB_SIZE
> +                               " bytes.\n"),
> +                            requested_keyfile_size,
> +                            keyfile->size);

The type of keyfile->size is grub_off_t which is typedef'd from
grub_uint64_t.  There is no problem when building for x86_64 because
PRIuGRUB_SIZE expands to %llu, which accepts a 64-bit uint.  But when
compiling for i386, PRIuGRUB_SIZE expands to %lu, which accepts a
32-bit uint.  This will cause the strict format string checking to fail
the build.  I recommend changing the second PRIuGRUB_SIZE to
PRIuGRUB_UINT64_T.

> +
> +       key_size = requested_keyfile_size;
> +     }
> +      else
> +     {
> +       key_size = keyfile->size - keyfile_offset;
> +     }
> +
> +      if (grub_file_read (keyfile, keyfile_buffer, key_size) !=
> key_size)
> +     return grub_error (GRUB_ERR_FILE_READ_ERROR,
> +                        (N_("Error reading key file\n")));
> +      key = keyfile_buffer;
> +    }
> +
>    if (state[0].set)
>      {
>        grub_cryptodisk_t dev;