[dm-devel] [PATCH v7 2/7] fs: crypto: invoke crypto API for ESSIV handling

[Ard Biesheuvel]

On Tue, 2 Jul 2019 at 23:55, Eric Biggers <ebiggers at kernel.org> wrote:
>
> Hi Ard,
>
> On Tue, Jul 02, 2019 at 06:48:10PM +0200, Ard Biesheuvel wrote:
> > Instead of open coding the calculations for ESSIV handling, use a
> > ESSIV skcipher which does all of this under the hood.
> >
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> > ---
> >  fs/crypto/Kconfig           |  1 +
> >  fs/crypto/crypto.c          |  5 --
> >  fs/crypto/fscrypt_private.h |  9 --
> >  fs/crypto/keyinfo.c         | 95 +-------------------
> >  4 files changed, 5 insertions(+), 105 deletions(-)
> >
> > diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> > index 24ed99e2eca0..b0292da8613c 100644
> > --- a/fs/crypto/Kconfig
> > +++ b/fs/crypto/Kconfig
> > @@ -5,6 +5,7 @@ config FS_ENCRYPTION
> >       select CRYPTO_AES
> >       select CRYPTO_CBC
> >       select CRYPTO_ECB
> > +     select CRYPTO_ESSIV
> >       select CRYPTO_XTS
> >       select CRYPTO_CTS
> >       select CRYPTO_SHA256
> > diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
> > index 335a362ee446..c53ce262a06c 100644
> > --- a/fs/crypto/crypto.c
> > +++ b/fs/crypto/crypto.c
> > @@ -136,9 +136,6 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
> >
> >       if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
> >               memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
> > -
> > -     if (ci->ci_essiv_tfm != NULL)
> > -             crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
> >  }
> >
> >  int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
> > @@ -492,8 +489,6 @@ static void __exit fscrypt_exit(void)
> >               destroy_workqueue(fscrypt_read_workqueue);
> >       kmem_cache_destroy(fscrypt_ctx_cachep);
> >       kmem_cache_destroy(fscrypt_info_cachep);
> > -
> > -     fscrypt_essiv_cleanup();
> >  }
> >  module_exit(fscrypt_exit);
> >
> > diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
> > index 7da276159593..59d0cba9cfb9 100644
> > --- a/fs/crypto/fscrypt_private.h
> > +++ b/fs/crypto/fscrypt_private.h
> > @@ -61,12 +61,6 @@ struct fscrypt_info {
> >       /* The actual crypto transform used for encryption and decryption */
> >       struct crypto_skcipher *ci_ctfm;
> >
> > -     /*
> > -      * Cipher for ESSIV IV generation.  Only set for CBC contents
> > -      * encryption, otherwise is NULL.
> > -      */
> > -     struct crypto_cipher *ci_essiv_tfm;
> > -
> >       /*
> >        * Encryption mode used for this inode.  It corresponds to either
> >        * ci_data_mode or ci_filename_mode, depending on the inode type.
> > @@ -166,9 +160,6 @@ struct fscrypt_mode {
> >       int keysize;
> >       int ivsize;
> >       bool logged_impl_name;
> > -     bool needs_essiv;
> >  };
> >
> > -extern void __exit fscrypt_essiv_cleanup(void);
> > -
> >  #endif /* _FSCRYPT_PRIVATE_H */
> > diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
> > index dcd91a3fbe49..f39667d4316a 100644
> > --- a/fs/crypto/keyinfo.c
> > +++ b/fs/crypto/keyinfo.c
> > @@ -13,14 +13,10 @@
> >  #include <linux/hashtable.h>
> >  #include <linux/scatterlist.h>
> >  #include <linux/ratelimit.h>
> > -#include <crypto/aes.h>
> >  #include <crypto/algapi.h>
> > -#include <crypto/sha.h>
> >  #include <crypto/skcipher.h>
> >  #include "fscrypt_private.h"
> >
> > -static struct crypto_shash *essiv_hash_tfm;
> > -
> >  /* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */
> >  static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
> >  static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
> > @@ -144,10 +140,9 @@ static struct fscrypt_mode available_modes[] = {
> >       },
> >       [FS_ENCRYPTION_MODE_AES_128_CBC] = {
> >               .friendly_name = "AES-128-CBC",
> > -             .cipher_str = "cbc(aes)",
> > +             .cipher_str = "essiv(cbc(aes),aes,sha256)",
> >               .keysize = 16,
> > -             .ivsize = 16,
> > -             .needs_essiv = true,
> > +             .ivsize = 8,
>
> As I said before, this needs to be kept as .ivsize = 16.
>
> This bug actually causes the generic/549 test to fail.
>

Ugh, yes, I intended to fix that. Apologies for the sloppiness, I have
been trying to wrap this up in time for my holidays, but the end
result is quite the opposite :-)

> Otherwise this patch looks good.  FYI: to avoid conflicts with planned fscrypt
> work I'd prefer to take this patch through the fscrypt.git tree after the ESSIV
> template is merged, rather than have Herbert take it through cryptodev.  (Unless
> he's going to apply this whole series for v5.3, in which case I'm fine with him
> taking the fscrypt patch too, though it seems too late for that.)
>

I agree that the fscrypt and dm-crypt changes should not be merged for v5.3

I know that Herbert typically prefers not to take any new code without
any of its users, but perhaps we can make an exception in this case,
and merge patches #1, #5, #6 and #7 now (which is mostly risk free
since no code uses essiv yet, and patch #5 is a straight-forward
refactor) and take the fscrypt and dm-crypt patches through their
respective trees for the next cycle.