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gpt: improve validation of GPT headers

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Adds basic validation of all the disk locations in the headers, reducing
the chance of corrupting weird locations on disk.
This commit is contained in:
Michael Marineau 2016-08-10 18:26:03 -07:00
parent 1c205c2c4d
commit 8278022a0b
1 changed files with 48 additions and 0 deletions

48
grub-core/lib/gpt.c
View file

@ -224,6 +224,7 @@ grub_gpt_header_check (struct grub_gpt_header *gpt,
unsigned int log_sector_size)
{
grub_uint32_t crc = 0, size;
grub_uint64_t start, end;
if (grub_memcmp (gpt->magic, grub_gpt_magic, sizeof (grub_gpt_magic)) != 0)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid GPT signature");
@ -245,9 +246,35 @@ grub_gpt_header_check (struct grub_gpt_header *gpt,
if (size < 128 || size % 128)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid GPT entry size");
/* And of course there better be some space for partitions! */
start = grub_le_to_cpu64 (gpt->start);
end = grub_le_to_cpu64 (gpt->end);
if (start > end)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid usable sectors");
return GRUB_ERR_NONE;
}
static int
grub_gpt_headers_equal (grub_gpt_t gpt)
{
/* Assume headers passed grub_gpt_header_check so skip magic and version.
* Individual fields must be checked instead of just using memcmp because
* crc32, header, alternate, and partitions will all normally differ. */
if (gpt->primary.headersize != gpt->backup.headersize ||
gpt->primary.header_lba != gpt->backup.alternate_lba ||
gpt->primary.start != gpt->backup.start ||
gpt->primary.end != gpt->backup.end ||
gpt->primary.maxpart != gpt->backup.maxpart ||
gpt->primary.partentry_size != gpt->backup.partentry_size ||
gpt->primary.partentry_crc32 != gpt->backup.partentry_crc32)
return 0;
return grub_memcmp(&gpt->primary.guid, &gpt->backup.guid,
sizeof(grub_gpt_guid_t)) == 0;
}
static grub_err_t
grub_gpt_check_primary (grub_gpt_t gpt)
{
@ -273,6 +300,12 @@ grub_gpt_check_primary (grub_gpt_t gpt)
if (grub_gpt_header_check (&gpt->primary, gpt->log_sector_size))
return grub_errno;
if (primary != 1)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid primary GPT LBA");
if (entries <= 1 || entries+entries_len > start)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid entries location");
if (backup <= end)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid backup GPT LBA");
return GRUB_ERR_NONE;
}
@ -302,6 +335,12 @@ grub_gpt_check_backup (grub_gpt_t gpt)
if (grub_gpt_header_check (&gpt->backup, gpt->log_sector_size))
return grub_errno;
if (primary != 1)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid primary GPT LBA");
if (entries <= end || entries+entries_len > backup)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid entries location");
if (backup <= end)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid backup GPT LBA");
return GRUB_ERR_NONE;
}
@ -354,6 +393,15 @@ grub_gpt_read_backup (grub_disk_t disk, grub_gpt_t gpt)
if (grub_gpt_check_backup (gpt))
return grub_errno;
/* Ensure the backup header thinks it is located where we found it. */
if (grub_le_to_cpu64 (gpt->backup.header_lba) != sector)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid backup GPT LBA");
/* If both primary and backup are valid but differ prefer the primary. */
if ((gpt->status & GRUB_GPT_PRIMARY_HEADER_VALID) &&
!grub_gpt_headers_equal(gpt))
return grub_error (GRUB_ERR_BAD_PART_TABLE, "backup GPT of of sync");
gpt->status |= GRUB_GPT_BACKUP_HEADER_VALID;
return GRUB_ERR_NONE;
}