On Thu, 4 Jul 2019 at 16:28, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > > (+ Eric) > > On Thu, 4 Jul 2019 at 15:29, Milan Broz <gmazyland@xxxxxxxxx> wrote: > > > > Hi Herbert, > > > > I have a question about the crypto_cipher API in dm-crypt: > > > > We are apparently trying to deprecate cryto_cipher API (see the ESSIV patchset), > > but I am not sure what API now should be used instead. > > > > Not precisely - what I would like to do is to make the cipher part of > the internal crypto API. The reason is that there are too many > occurrences where non-trivial chaining modes have been cobbled > together from the cipher API. > > > See the patch below - all we need is to one block encryption for IV. > > > > This algorithm makes sense only for FDE (old compatible Bitlocker devices), > > I really do not want this to be shared in some crypto module... > > > > What API should I use here? Sync skcipher? Is the crypto_cipher API > > really a problem in this case? > > > > Are arbitrary ciphers supported? Or are you only interested in AES? In > the former case, I'd suggest the sync skcipher API to instantiate > "ecb(%s)", otherwise, use the upcoming AES library interface. > Actually, if CBC is the only supported mode, you could also use the skcipher itself to encrypt a single block of input (just encrypt the IV using CBC but with an IV of all zeroes) > > On 04/07/2019 15:10, Milan Broz wrote: > > > This IV is used in some BitLocker devices with CBC encryption mode. > > > > > > NOTE: maybe we need to use another crypto API if the bare cipher > > > API is going to be deprecated. > > > > > > Signed-off-by: Milan Broz <gmazyland@xxxxxxxxx> > > > --- > > > drivers/md/dm-crypt.c | 82 ++++++++++++++++++++++++++++++++++++++++++- > > > 1 file changed, 81 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c > > > index 96ead4492787..a5ffa1ac6a28 100644 > > > --- a/drivers/md/dm-crypt.c > > > +++ b/drivers/md/dm-crypt.c > > > @@ -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, > > >