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dm crypt: implement eboiv - encrypted byte-offset initialization vector

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This IV is used in some BitLocker devices with CBC encryption mode.

IV is encrypted little-endian byte-offset (with the same key and cipher
as the volume).

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Milan Broz 2019-07-09 15:22:14 +02:00 committed by Mike Snitzer
parent 6028a7a5a3
commit b9411d73bd
1 changed files with 81 additions and 1 deletions
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82
drivers/md/dm-crypt.c
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@ -120,6 +120,10 @@ struct iv_tcw_private {
u8 *whitening;
};
struct iv_eboiv_private {
struct crypto_cipher *tfm;
};
/*
* Crypt: maps a linear range of a block device
* and encrypts / decrypts at the same time.
@ -159,6 +163,7 @@ struct crypt_config {
struct iv_benbi_private benbi;
struct iv_lmk_private lmk;
struct iv_tcw_private tcw;
struct iv_eboiv_private eboiv;
} iv_gen_private;
u64 iv_offset;
unsigned int iv_size;
@ -290,6 +295,10 @@ static struct crypto_aead *any_tfm_aead(struct crypt_config *cc)
* is calculated from initial key, sector number and mixed using CRC32.
* Note that this encryption scheme is vulnerable to watermarking attacks
* and should be used for old compatible containers access only.
*
* eboiv: Encrypted byte-offset IV (used in Bitlocker in CBC mode)
* The IV is encrypted little-endian byte-offset (with the same key
* and cipher as the volume).
*/
static int crypt_iv_plain_gen(struct crypt_config *cc, u8 *iv,
@ -838,6 +847,67 @@ static int crypt_iv_random_gen(struct crypt_config *cc, u8 *iv,
return 0;
}
static void crypt_iv_eboiv_dtr(struct crypt_config *cc)
{
struct iv_eboiv_private *eboiv = &cc->iv_gen_private.eboiv;
crypto_free_cipher(eboiv->tfm);
eboiv->tfm = NULL;
}
static int crypt_iv_eboiv_ctr(struct crypt_config *cc, struct dm_target *ti,
const char *opts)
{
struct iv_eboiv_private *eboiv = &cc->iv_gen_private.eboiv;
struct crypto_cipher *tfm;
tfm = crypto_alloc_cipher(cc->cipher, 0, 0);
if (IS_ERR(tfm)) {
ti->error = "Error allocating crypto tfm for EBOIV";
return PTR_ERR(tfm);
}
if (crypto_cipher_blocksize(tfm) != cc->iv_size) {
ti->error = "Block size of EBOIV cipher does "
"not match IV size of block cipher";
crypto_free_cipher(tfm);
return -EINVAL;
}
eboiv->tfm = tfm;
return 0;
}
static int crypt_iv_eboiv_init(struct crypt_config *cc)
{
struct iv_eboiv_private *eboiv = &cc->iv_gen_private.eboiv;
int err;
err = crypto_cipher_setkey(eboiv->tfm, cc->key, cc->key_size);
if (err)
return err;
return 0;
}
static int crypt_iv_eboiv_wipe(struct crypt_config *cc)
{
/* Called after cc->key is set to random key in crypt_wipe() */
return crypt_iv_eboiv_init(cc);
}
static int crypt_iv_eboiv_gen(struct crypt_config *cc, u8 *iv,
struct dm_crypt_request *dmreq)
{
struct iv_eboiv_private *eboiv = &cc->iv_gen_private.eboiv;
memset(iv, 0, cc->iv_size);
*(__le64 *)iv = cpu_to_le64(dmreq->iv_sector * cc->sector_size);
crypto_cipher_encrypt_one(eboiv->tfm, iv, iv);
return 0;
}
static const struct crypt_iv_operations crypt_iv_plain_ops = {
.generator = crypt_iv_plain_gen
};
@ -890,6 +960,14 @@ static struct crypt_iv_operations crypt_iv_random_ops = {
.generator = crypt_iv_random_gen
};
static struct crypt_iv_operations crypt_iv_eboiv_ops = {
.ctr = crypt_iv_eboiv_ctr,
.dtr = crypt_iv_eboiv_dtr,
.init = crypt_iv_eboiv_init,
.wipe = crypt_iv_eboiv_wipe,
.generator = crypt_iv_eboiv_gen
};
/*
* Integrity extensions
*/
@ -2293,6 +2371,8 @@ static int crypt_ctr_ivmode(struct dm_target *ti, const char *ivmode)
cc->iv_gen_ops = &crypt_iv_benbi_ops;
else if (strcmp(ivmode, "null") == 0)
cc->iv_gen_ops = &crypt_iv_null_ops;
else if (strcmp(ivmode, "eboiv") == 0)
cc->iv_gen_ops = &crypt_iv_eboiv_ops;
else if (strcmp(ivmode, "lmk") == 0) {
cc->iv_gen_ops = &crypt_iv_lmk_ops;
/*
@ -3093,7 +3173,7 @@ static void crypt_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type crypt_target = {
.name = "crypt",
.version = {1, 18, 1},
.version = {1, 19, 0},
.module = THIS_MODULE,
.ctr = crypt_ctr,
.dtr = crypt_dtr,