On Mon, 1 Jul 2019 at 10:59, Milan Broz <gmazyland@xxxxxxxxx> wrote:
>
> On 28/06/2019 17:21, Ard Biesheuvel wrote:
> > Replace the explicit ESSIV handling in the dm-crypt driver with calls
> > into the crypto API, which now possesses the capability to perform
> > this processing within the crypto subsystem.
> >
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>
> > drivers/md/dm-crypt.c | 200 ++++----------------
>
> ...
>
> > -/* Wipe salt and reset key derived from volume key */
> > -static int crypt_iv_essiv_wipe(struct crypt_config *cc)
>
> Do I understand it correctly, that this is now called inside the whole cipher
> set key in wipe command (in crypt_wipe_key())?
>
> (Wipe message is meant to suspend the device and wipe all key material
> from memory without actually destroying the device.)
>
Yes, setting the random key in wipe() triggers the SHA256 operation as
normal, which is slightly wasteful but not a big deal imo.
> > -{
> > - struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
> > - unsigned salt_size = crypto_shash_digestsize(essiv->hash_tfm);
> > - struct crypto_cipher *essiv_tfm;
> > - int r, err = 0;
> > -
> > - memset(essiv->salt, 0, salt_size);
> > -
> > - essiv_tfm = cc->iv_private;
> > - r = crypto_cipher_setkey(essiv_tfm, essiv->salt, salt_size);
> > - if (r)
> > - err = r;
> > -
> > - return err;
> > -}
>
> ...
>
> > @@ -2435,9 +2281,19 @@ static int crypt_ctr_cipher_new(struct dm_target *ti, char *cipher_in, char *key
> > }
> >
> > ret = crypt_ctr_blkdev_cipher(cc, cipher_api);
> > - if (ret < 0) {
> > - ti->error = "Cannot allocate cipher string";
> > - return -ENOMEM;
> > + if (ret < 0)
> > + goto bad_mem;
> > +
> > + if (*ivmode && !strcmp(*ivmode, "essiv")) {
> > + if (!*ivopts) {
> > + ti->error = "Digest algorithm missing for ESSIV mode";
> > + return -EINVAL;
> > + }
> > + ret = snprintf(buf, CRYPTO_MAX_ALG_NAME, "essiv(%s,%s,%s)",
> > + cipher_api, cc->cipher, *ivopts);
> > + if (ret < 0 || ret >= CRYPTO_MAX_ALG_NAME)
> > + goto bad_mem;
>
> Hm, nitpicking, but goto from only one place while we have another -ENOMEM above...
>
> Just place this here without goto?
>
OK
> > + ti->error = "Cannot allocate cipher string";
> > + return -ENOMEM;
>
> Otherwise
>
> Reviewed-by: Milan Broz <gmazyland@xxxxxxxxx>
>
> Thanks,
> Milan
