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Re: [PATCH v6 07/12] luks2: Better error handling when setting up the cr
From: |
Daniel Kiper |
Subject: |
Re: [PATCH v6 07/12] luks2: Better error handling when setting up the cryptodisk |
Date: |
Thu, 3 Dec 2020 14:31:49 +0100 |
User-agent: |
NeoMutt/20170113 (1.7.2) |
On Fri, Nov 27, 2020 at 03:03:39AM -0600, Glenn Washburn wrote:
> First, check to make sure that source disk has a known size. If not, print
> debug message and return error. There are 4 cases where
> GRUB_DISK_SIZE_UNKNOWN is set (biosdisk, obdisk, ofdisk, and uboot), and in
> all those cases processing continues. So this is probably a bit
> conservative. However, 3 of the cases seem pathological, and the other,
> biosdisk, happens when booting from a cd. Since I doubt booting from a LUKS2
> volume on a cd is a big use case, we'll error until someone complains.
>
> Do some sanity checking on data coming from the luks header. If segment.size
> is "dynamic",
>
> Check for errors from grub_strtoull when converting segment size from
> string. If a GRUB_ERR_BAD_NUMBER error was returned, then the string was
> not a valid parsable number, so skip the key. If GRUB_ERR_OUT_OF_RANGE was
> returned, then there was an overflow in converting to a 64-bit unsigned
> integer. So this could be a very large disk (perhaps large raid array).
> In this case, we want to continue to try to use this key so long as the
> source disk's size is greater than this segment size. Otherwise, this is
> an invalid segment, and continue on to the next key.
>
> Signed-off-by: Glenn Washburn <development@efficientek.com>
> ---
> grub-core/disk/luks2.c | 80 ++++++++++++++++++++++++++++++++++++++++--
> include/grub/disk.h | 16 +++++++++
> 2 files changed, 93 insertions(+), 3 deletions(-)
>
> diff --git a/grub-core/disk/luks2.c b/grub-core/disk/luks2.c
> index b7ed0642e..01f9608e5 100644
> --- a/grub-core/disk/luks2.c
> +++ b/grub-core/disk/luks2.c
> @@ -597,12 +597,26 @@ luks2_recover_key (grub_disk_t source,
> goto err;
> }
>
> + if (source->total_sectors == GRUB_DISK_SIZE_UNKNOWN)
> + {
> + /* FIXME: Allow use of source disk, and maybe cause errors in read. */
> + grub_dprintf ("luks2", "Source disk %s has an unknown size, "
> + "conservatively returning error\n", source->name);
> + ret = grub_error (GRUB_ERR_BUG, "Unknown size of luks2 source device");
> + goto err;
> + }
> +
> /* Try all keyslot */
> for (i = 0; i < size; i++)
> {
> + typeof(source->total_sectors) max_crypt_sectors = 0;
> +
> + grub_errno = GRUB_ERR_NONE;
> ret = luks2_get_keyslot (&keyslot, &digest, &segment, json, i);
> if (ret)
> goto err;
> + if (grub_errno != GRUB_ERR_NONE)
> + grub_dprintf ("luks2", "Ignoring unhandled error %d from
> luks2_get_keyslot\n", grub_errno);
>
> if (keyslot.priority == 0)
> {
> @@ -616,11 +630,71 @@ luks2_recover_key (grub_disk_t source,
> crypt->offset_sectors = grub_divmod64 (segment.offset,
> segment.sector_size, NULL);
> crypt->log_sector_size = sizeof (unsigned int) * 8
> - __builtin_clz ((unsigned int) segment.sector_size) - 1;
> + /* Set to the source disk size, which is the maximum we allow. */
> + max_crypt_sectors = grub_disk_convert_sector(source,
> + source->total_sectors,
> + crypt->log_sector_size);
> +
> + if (max_crypt_sectors < crypt->offset_sectors)
> + {
> + grub_dprintf ("luks2", "Segment \"%"PRIuGRUB_UINT64_T"\" has offset"
> + " %"PRIuGRUB_UINT64_T" which is greater than"
> + " source disk size %"PRIuGRUB_UINT64_T","
> + " skipping\n",
> + segment.slot_key, crypt->offset_sectors,
> + max_crypt_sectors);
> + continue;
> + }
> +
> if (grub_strcmp (segment.size, "dynamic") == 0)
> - crypt->total_sectors = (grub_disk_get_size (source) >>
> (crypt->log_sector_size - source->log_sector_size))
> - - crypt->offset_sectors;
> + crypt->total_sectors = max_crypt_sectors - crypt->offset_sectors;
> else
> - crypt->total_sectors = grub_strtoull (segment.size, NULL, 10) >>
> crypt->log_sector_size;
> + {
> + grub_errno = GRUB_ERR_NONE;
> + crypt->total_sectors = grub_strtoull (segment.size, NULL, 10) >>
> crypt->log_sector_size;
I think ">>" should not happen here...
> + if (grub_errno == GRUB_ERR_NONE)
> + ;
It should happen here... Or to be exact...
crypt->total_sectors = ALIGN_UP (crypt->total_sectors, 1 <<
crypt->log_sector_size); // Am I right?
crypt->total_sectors >>= crypt->log_sector_size;
> + else if(grub_errno == GRUB_ERR_BAD_NUMBER)
Missing space before "("...
> + {
> + /* TODO: Unparsable number-string, try to use the whole disk */
> + grub_dprintf ("luks2", "Segment \"%"PRIuGRUB_UINT64_T"\" size"
> + " \"%s\" is not a parsable number\n",
> + segment.slot_key, segment.size);
crypt->total_sectors = max_crypt_sectors; ?
> + continue;
...and then drop continue?
> + }
> + else if(grub_errno == GRUB_ERR_OUT_OF_RANGE)
> + {
> + /*
> + * There was an overflow in parsing segment.size, so disk must
> + * be very large or the string is incorrect.
> + */
> + grub_dprintf ("luks2", "Segment \"%"PRIuGRUB_UINT64_T"\" size"
> + " %s overflowed 64-bit unsigned integer,"
> + " the end of the crypto device will be"
> + " inaccessible\n",
> + segment.slot_key, segment.size);
> + if (crypt->total_sectors > max_crypt_sectors)
> + crypt->total_sectors = max_crypt_sectors;
> + }
> + }
> +
> + if (crypt->total_sectors == 0)
> + {
> + grub_dprintf ("luks2", "Segment \"%"PRIuGRUB_UINT64_T"\" has zero"
> + " sectors, skipping\n",
> + segment.slot_key);
> + continue;
> + }
> + else if (max_crypt_sectors < (crypt->offset_sectors +
> crypt->total_sectors))
> + {
> + grub_dprintf ("luks2", "Segment \"%"PRIuGRUB_UINT64_T"\" has last"
> + " data position greater than source disk size,"
> + " the end of the crypto device will be"
> + " inaccessible\n",
> + segment.slot_key);
> + /* Allow decryption up to the end of the source disk. */
> + crypt->total_sectors = max_crypt_sectors - crypt->offset_sectors;
> + }
>
> ret = luks2_decrypt_key (candidate_key, source, crypt, &keyslot,
> (const grub_uint8_t *) passphrase, grub_strlen
> (passphrase));
> diff --git a/include/grub/disk.h b/include/grub/disk.h
> index 132a1bb75..1a9e8fcf4 100644
> --- a/include/grub/disk.h
> +++ b/include/grub/disk.h
> @@ -174,6 +174,22 @@ typedef struct grub_disk_memberlist
> *grub_disk_memberlist_t;
> /* Return value of grub_disk_get_size() in case disk size is unknown. */
> #define GRUB_DISK_SIZE_UNKNOWN 0xffffffffffffffffULL
>
> +/* Convert sector number from disk sized sectors to a log-size sized sector.
> */
> +static inline grub_disk_addr_t
> +grub_disk_convert_sector (grub_disk_t disk,
> + grub_disk_addr_t sector,
> + grub_size_t log_sector_size)
> +{
> + if (disk->log_sector_size < log_sector_size)
> + {
> + /* Round up to the nearest log_sector_size sized sector. */
> + sector += 1ULL << ((log_sector_size / disk->log_sector_size) - 1);
ALIGN_UP()?
> + return sector >> (log_sector_size - disk->log_sector_size);
> + }
> + else
> + return sector << (disk->log_sector_size - log_sector_size);
> +}
> +
> /* Convert to GRUB native disk sized sector from disk sized sector. */
> static inline grub_disk_addr_t
> grub_disk_from_native_sector (grub_disk_t disk, grub_disk_addr_t sector)
Daniel
- Re: [PATCH v6 07/12] luks2: Better error handling when setting up the cryptodisk,
Daniel Kiper <=