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qcrypto-luks: simplify the math used for keyslot locations

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Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Maxim Levitsky 2019-09-26 00:35:25 +03:00 committed by Daniel P. Berrangé
parent 3994a7c909
commit bd56a55a94
1 changed files with 40 additions and 23 deletions
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63
crypto/block-luks.c
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@ -409,6 +409,30 @@ qcrypto_block_luks_essiv_cipher(QCryptoCipherAlgorithm cipher,
}
}
/*
* Returns number of sectors needed to store the key material
* given number of anti forensic stripes
*/
static int
qcrypto_block_luks_splitkeylen_sectors(const QCryptoBlockLUKS *luks,
unsigned int header_sectors,
unsigned int stripes)
{
/*
* This calculation doesn't match that shown in the spec,
* but instead follows the cryptsetup implementation.
*/
size_t splitkeylen = luks->header.master_key_len * stripes;
/* First align the key material size to block size*/
size_t splitkeylen_sectors =
DIV_ROUND_UP(splitkeylen, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE);
/* Then also align the key material size to the size of the header */
return ROUND_UP(splitkeylen_sectors, header_sectors);
}
/*
* Stores the main LUKS header, taking care of endianess
*/
@ -1114,7 +1138,8 @@ qcrypto_block_luks_create(QCryptoBlock *block,
QCryptoBlockCreateOptionsLUKS luks_opts;
Error *local_err = NULL;
g_autofree uint8_t *masterkey = NULL;
size_t splitkeylen = 0;
size_t header_sectors;
size_t split_key_sectors;
size_t i;
g_autofree char *password = NULL;
const char *cipher_alg;
@ -1333,37 +1358,29 @@ qcrypto_block_luks_create(QCryptoBlock *block,
goto error;
}
/* start with the sector that follows the header*/
header_sectors = QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
split_key_sectors =
qcrypto_block_luks_splitkeylen_sectors(luks,
header_sectors,
QCRYPTO_BLOCK_LUKS_STRIPES);
/* Although LUKS has multiple key slots, we're just going
* to use the first key slot */
splitkeylen = luks->header.master_key_len * QCRYPTO_BLOCK_LUKS_STRIPES;
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
luks->header.key_slots[i].active = QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED;
luks->header.key_slots[i].stripes = QCRYPTO_BLOCK_LUKS_STRIPES;
QCryptoBlockLUKSKeySlot *slot = &luks->header.key_slots[i];
slot->active = QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED;
/* This calculation doesn't match that shown in the spec,
* but instead follows the cryptsetup implementation.
*/
luks->header.key_slots[i].key_offset_sector =
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE) +
(ROUND_UP(DIV_ROUND_UP(splitkeylen, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE),
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE)) * i);
slot->key_offset_sector = header_sectors + i * split_key_sectors;
slot->stripes = QCRYPTO_BLOCK_LUKS_STRIPES;
}
/* The total size of the LUKS headers is the partition header + key
* slot headers, rounded up to the nearest sector, combined with
* the size of each master key material region, also rounded up
* to the nearest sector */
luks->header.payload_offset_sector =
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE) +
(ROUND_UP(DIV_ROUND_UP(splitkeylen, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE),
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE)) *
QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
luks->header.payload_offset_sector = header_sectors +
QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS * split_key_sectors;
block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
block->payload_offset = luks->header.payload_offset_sector *