[v11,1/4] crypto: essiv - create wrapper template for ESSIV generation
diff mbox series

Message ID 20190814163746.3525-2-ard.biesheuvel@linaro.org
State Not Applicable
Headers show
Series
  • crypto: switch to crypto API for ESSIV generation
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Commit Message

Ard Biesheuvel Aug. 14, 2019, 4:37 p.m. UTC
Implement a template that wraps a (skcipher,shash) or (aead,shash) tuple
so that we can consolidate the ESSIV handling in fscrypt and dm-crypt and
move it into the crypto API. This will result in better test coverage, and
will allow future changes to make the bare cipher interface internal to the
crypto subsystem, in order to increase robustness of the API against misuse.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 crypto/Kconfig  |  28 +
 crypto/Makefile |   1 +
 crypto/essiv.c  | 667 ++++++++++++++++++++
 3 files changed, 696 insertions(+)

Comments

Herbert Xu Aug. 15, 2019, 2:37 a.m. UTC | #1
On Wed, Aug 14, 2019 at 07:37:43PM +0300, Ard Biesheuvel wrote:
>
> +	/* Block cipher, e.g., "aes" */
> +	crypto_set_spawn(&ictx->essiv_cipher_spawn, inst);
> +	err = crypto_grab_spawn(&ictx->essiv_cipher_spawn, essiv_cipher_name,
> +				CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK);
> +	if (err)
> +		goto out_drop_skcipher;
> +	essiv_cipher_alg = ictx->essiv_cipher_spawn.alg;
> +
> +	/* Synchronous hash, e.g., "sha256" */
> +	_hash_alg = crypto_alg_mod_lookup(shash_name,
> +					  CRYPTO_ALG_TYPE_SHASH,
> +					  CRYPTO_ALG_TYPE_MASK);
> +	if (IS_ERR(_hash_alg)) {
> +		err = PTR_ERR(_hash_alg);
> +		goto out_drop_essiv_cipher;
> +	}
> +	hash_alg = __crypto_shash_alg(_hash_alg);
> +	err = crypto_init_shash_spawn(&ictx->hash_spawn, hash_alg, inst);
> +	if (err)
> +		goto out_put_hash;

I wouldn't use spawns for these two algorithms.  The point of
spawns is mainly to serve as a notification channel so we can
tear down the top-level instance when a better underlying spawn
implementation is added to the system.

For these two algorithms, we don't really care about their performance
to do such a tear-down since they only operate on small pieces of
data.

Therefore just keep things simple and allocate them in the tfm
init function.

Thanks,
Ard Biesheuvel Aug. 15, 2019, 4:59 a.m. UTC | #2
On Thu, 15 Aug 2019 at 05:37, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Wed, Aug 14, 2019 at 07:37:43PM +0300, Ard Biesheuvel wrote:
> >
> > +     /* Block cipher, e.g., "aes" */
> > +     crypto_set_spawn(&ictx->essiv_cipher_spawn, inst);
> > +     err = crypto_grab_spawn(&ictx->essiv_cipher_spawn, essiv_cipher_name,
> > +                             CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK);
> > +     if (err)
> > +             goto out_drop_skcipher;
> > +     essiv_cipher_alg = ictx->essiv_cipher_spawn.alg;
> > +
> > +     /* Synchronous hash, e.g., "sha256" */
> > +     _hash_alg = crypto_alg_mod_lookup(shash_name,
> > +                                       CRYPTO_ALG_TYPE_SHASH,
> > +                                       CRYPTO_ALG_TYPE_MASK);
> > +     if (IS_ERR(_hash_alg)) {
> > +             err = PTR_ERR(_hash_alg);
> > +             goto out_drop_essiv_cipher;
> > +     }
> > +     hash_alg = __crypto_shash_alg(_hash_alg);
> > +     err = crypto_init_shash_spawn(&ictx->hash_spawn, hash_alg, inst);
> > +     if (err)
> > +             goto out_put_hash;
>
> I wouldn't use spawns for these two algorithms.  The point of
> spawns is mainly to serve as a notification channel so we can
> tear down the top-level instance when a better underlying spawn
> implementation is added to the system.
>
> For these two algorithms, we don't really care about their performance
> to do such a tear-down since they only operate on small pieces of
> data.
>
> Therefore just keep things simple and allocate them in the tfm
> init function.
>

So how do I ensure that the cipher and shash are actually loaded at
create() time, and that they are still loaded at TFM init time?
Herbert Xu Aug. 15, 2019, 5:13 a.m. UTC | #3
On Thu, Aug 15, 2019 at 07:59:34AM +0300, Ard Biesheuvel wrote:
>
> So how do I ensure that the cipher and shash are actually loaded at
> create() time, and that they are still loaded at TFM init time?

If they're not available at TFM init then you just fail the init
and therefore the TFM allocation.  What is the problem?

IOW the presence of the block cipher and unkeyed hash does not
affect the creation of the instance object.

Cheers,
Ard Biesheuvel Aug. 15, 2019, 5:15 a.m. UTC | #4
On Thu, 15 Aug 2019 at 08:13, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Thu, Aug 15, 2019 at 07:59:34AM +0300, Ard Biesheuvel wrote:
> >
> > So how do I ensure that the cipher and shash are actually loaded at
> > create() time, and that they are still loaded at TFM init time?
>
> If they're not available at TFM init then you just fail the init
> and therefore the TFM allocation.  What is the problem?
>
> IOW the presence of the block cipher and unkeyed hash does not
> affect the creation of the instance object.
>

Right.

So what about checking that the cipher key size matches the shash
digest size, or that the cipher block size matches the skcipher IV
size? This all moves to the TFM init function?

Are there any existing templates that use this approach?
Herbert Xu Aug. 15, 2019, 11:35 a.m. UTC | #5
On Thu, Aug 15, 2019 at 08:15:29AM +0300, Ard Biesheuvel wrote:
> 
> So what about checking that the cipher key size matches the shash
> digest size, or that the cipher block size matches the skcipher IV
> size? This all moves to the TFM init function?

I don't think you need to check those things.  If the shash produces
an incorrect key size the setkey will just fail naturally.  As to
the block size matching the IV size, in the kernel it's not actually
possible to get an underlying cipher with different block size
than the cbc mode that you used to derive it.

The size checks that we have in general are to stop people from
making crazy combinations such as lrw(des3_ede), it's not there
to test the correctness of a given implementation.  That is,
we assume that whoever provides "aes" will give it the correct
geometry for it.

Sure we haven't made it explicit (which we should at some point)
but as it stands, it can only occur if we have a bug or someone
loads a malicious kernel module in which case none of this matters.

> Are there any existing templates that use this approach?

I'm not sure of templates doing this but this is similar to fallbacks.
In fact we don't check any gemoetry on the fallbacks at all.

Cheers,
Ard Biesheuvel Aug. 15, 2019, 5:46 p.m. UTC | #6
On Thu, 15 Aug 2019 at 14:35, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Thu, Aug 15, 2019 at 08:15:29AM +0300, Ard Biesheuvel wrote:
> >
> > So what about checking that the cipher key size matches the shash
> > digest size, or that the cipher block size matches the skcipher IV
> > size? This all moves to the TFM init function?
>
> I don't think you need to check those things.  If the shash produces
> an incorrect key size the setkey will just fail naturally.  As to
> the block size matching the IV size, in the kernel it's not actually
> possible to get an underlying cipher with different block size
> than the cbc mode that you used to derive it.
>

dm-crypt permits any skcipher to be used with ESSIV, so the template
does not enforce CBC to be used.

> The size checks that we have in general are to stop people from
> making crazy combinations such as lrw(des3_ede), it's not there
> to test the correctness of a given implementation.  That is,
> we assume that whoever provides "aes" will give it the correct
> geometry for it.
>
> Sure we haven't made it explicit (which we should at some point)
> but as it stands, it can only occur if we have a bug or someone
> loads a malicious kernel module in which case none of this matters.
>

OK.

> > Are there any existing templates that use this approach?
>
> I'm not sure of templates doing this but this is similar to fallbacks.
> In fact we don't check any gemoetry on the fallbacks at all.
>

OK, so one other thing: how should I populate the cra_name template
field if someone instantiates essiv(cbc(aes),sha256-ce)? We won't know
until TFM init time what cra_name allocating the sha256-ce shash
actually produces, so the only way to populate those names is to use
the bare string supplied by the caller, which could be bogus.

To me, it seems like retaining the spawn for the shash is more
idiomatic, and avoids strange issues like the one above. Dropping the
spawn for the encapsulated cipher (which is tightly coupled to the
skcipher/aead being encapsulated) does seem feasible, so I'll go with
that.
Ard Biesheuvel Aug. 15, 2019, 5:59 p.m. UTC | #7
On Thu, 15 Aug 2019 at 20:46, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
> On Thu, 15 Aug 2019 at 14:35, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> >
> > On Thu, Aug 15, 2019 at 08:15:29AM +0300, Ard Biesheuvel wrote:
> > >
> > > So what about checking that the cipher key size matches the shash
> > > digest size, or that the cipher block size matches the skcipher IV
> > > size? This all moves to the TFM init function?
> >
> > I don't think you need to check those things.  If the shash produces
> > an incorrect key size the setkey will just fail naturally.  As to
> > the block size matching the IV size, in the kernel it's not actually
> > possible to get an underlying cipher with different block size
> > than the cbc mode that you used to derive it.
> >
>
> dm-crypt permits any skcipher to be used with ESSIV, so the template
> does not enforce CBC to be used.
>
> > The size checks that we have in general are to stop people from
> > making crazy combinations such as lrw(des3_ede), it's not there
> > to test the correctness of a given implementation.  That is,
> > we assume that whoever provides "aes" will give it the correct
> > geometry for it.
> >
> > Sure we haven't made it explicit (which we should at some point)
> > but as it stands, it can only occur if we have a bug or someone
> > loads a malicious kernel module in which case none of this matters.
> >
>
> OK.
>
> > > Are there any existing templates that use this approach?
> >
> > I'm not sure of templates doing this but this is similar to fallbacks.
> > In fact we don't check any gemoetry on the fallbacks at all.
> >
>
> OK, so one other thing: how should I populate the cra_name template
> field if someone instantiates essiv(cbc(aes),sha256-ce)? We won't know
> until TFM init time what cra_name allocating the sha256-ce shash
> actually produces, so the only way to populate those names is to use
> the bare string supplied by the caller, which could be bogus.
>
> To me, it seems like retaining the spawn for the shash is more
> idiomatic, and avoids strange issues like the one above. Dropping the
> spawn for the encapsulated cipher (which is tightly coupled to the
> skcipher/aead being encapsulated) does seem feasible, so I'll go with
> that.

Actually, I should be able to lookup the alg without using it to
create a spawn. Let me try that instead.

Patch
diff mbox series

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 8880c1fc51d8..dbceaed65e52 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -482,6 +482,34 @@  config CRYPTO_ADIANTUM
 
 	  If unsure, say N.
 
+config CRYPTO_ESSIV
+	tristate "ESSIV support for block encryption"
+	select CRYPTO_AUTHENC
+	help
+	  Encrypted salt-sector initialization vector (ESSIV) is an IV
+	  generation method that is used in some cases by fscrypt and/or
+	  dm-crypt. It uses the hash of the block encryption key as the
+	  symmetric key for a block encryption pass applied to the input
+	  IV, making low entropy IV sources more suitable for block
+	  encryption.
+
+	  This driver implements a crypto API template that can be
+	  instantiated either as a skcipher or as a aead (depending on the
+	  type of the first template argument), and which defers encryption
+	  and decryption requests to the encapsulated cipher after applying
+	  ESSIV to the input IV. Note that in the aead case, it is assumed
+	  that the keys are presented in the same format used by the authenc
+	  template, and that the IV appears at the end of the authenticated
+	  associated data (AAD) region (which is how dm-crypt uses it.)
+
+	  Note that the use of ESSIV is not recommended for new deployments,
+	  and so this only needs to be enabled when interoperability with
+	  existing encrypted volumes of filesystems is required, or when
+	  building for a particular system that requires it (e.g., when
+	  the SoC in question has accelerated CBC but not XTS, making CBC
+	  combined with ESSIV the only feasible mode for h/w accelerated
+	  block encryption)
+
 comment "Hash modes"
 
 config CRYPTO_CMAC
diff --git a/crypto/Makefile b/crypto/Makefile
index cfcc954e59f9..c204029f21ab 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -145,6 +145,7 @@  obj-$(CONFIG_CRYPTO_USER_API_AEAD) += algif_aead.o
 obj-$(CONFIG_CRYPTO_ZSTD) += zstd.o
 obj-$(CONFIG_CRYPTO_OFB) += ofb.o
 obj-$(CONFIG_CRYPTO_ECC) += ecc.o
+obj-$(CONFIG_CRYPTO_ESSIV) += essiv.o
 
 ecdh_generic-y += ecdh.o
 ecdh_generic-y += ecdh_helper.o
diff --git a/crypto/essiv.c b/crypto/essiv.c
new file mode 100644
index 000000000000..b662b8b06f30
--- /dev/null
+++ b/crypto/essiv.c
@@ -0,0 +1,667 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ESSIV skcipher and aead template for block encryption
+ *
+ * This template encapsulates the ESSIV IV generation algorithm used by
+ * dm-crypt and fscrypt, which converts the initial vector for the skcipher
+ * used for block encryption, by encrypting it using the hash of the
+ * skcipher key as encryption key. Usually, the input IV is a 64-bit sector
+ * number in LE representation zero-padded to the size of the IV, but this
+ * is not assumed by this driver.
+ *
+ * The typical use of this template is to instantiate the skcipher
+ * 'essiv(cbc(aes),sha256)', which is the only instantiation used by
+ * fscrypt, and the most relevant one for dm-crypt. However, dm-crypt
+ * also permits ESSIV to be used in combination with the authenc template,
+ * e.g., 'essiv(authenc(hmac(sha256),cbc(aes)),sha256)', in which case
+ * we need to instantiate an aead that accepts the same special key format
+ * as the authenc template, and deals with the way the encrypted IV is
+ * embedded into the AAD area of the aead request. This means the AEAD
+ * flavor produced by this template is tightly coupled to the way dm-crypt
+ * happens to use it.
+ *
+ * Copyright (c) 2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>
+ *
+ * Heavily based on:
+ * adiantum length-preserving encryption mode
+ *
+ * Copyright 2018 Google LLC
+ */
+
+#include <crypto/authenc.h>
+#include <crypto/internal/aead.h>
+#include <crypto/internal/hash.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/scatterwalk.h>
+#include <linux/module.h>
+
+#include "internal.h"
+
+struct essiv_instance_ctx {
+	union {
+		struct crypto_skcipher_spawn	skcipher_spawn;
+		struct crypto_aead_spawn	aead_spawn;
+	} u;
+	struct crypto_spawn			essiv_cipher_spawn;
+	struct crypto_shash_spawn		hash_spawn;
+};
+
+struct essiv_tfm_ctx {
+	union {
+		struct crypto_skcipher	*skcipher;
+		struct crypto_aead	*aead;
+	} u;
+	struct crypto_cipher		*essiv_cipher;
+	struct crypto_shash		*hash;
+	int				ivoffset;
+};
+
+struct essiv_aead_request_ctx {
+	struct scatterlist		sg[4];
+	u8				*assoc;
+	struct aead_request		aead_req;
+};
+
+static int essiv_skcipher_setkey(struct crypto_skcipher *tfm,
+				 const u8 *key, unsigned int keylen)
+{
+	struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
+	SHASH_DESC_ON_STACK(desc, tctx->hash);
+	u8 salt[HASH_MAX_DIGESTSIZE];
+	int err;
+
+	crypto_skcipher_clear_flags(tctx->u.skcipher, CRYPTO_TFM_REQ_MASK);
+	crypto_skcipher_set_flags(tctx->u.skcipher,
+				  crypto_skcipher_get_flags(tfm) &
+				  CRYPTO_TFM_REQ_MASK);
+	err = crypto_skcipher_setkey(tctx->u.skcipher, key, keylen);
+	crypto_skcipher_set_flags(tfm,
+				  crypto_skcipher_get_flags(tctx->u.skcipher) &
+				  CRYPTO_TFM_RES_MASK);
+	if (err)
+		return err;
+
+	desc->tfm = tctx->hash;
+	err = crypto_shash_digest(desc, key, keylen, salt);
+	if (err)
+		return err;
+
+	crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
+	crypto_cipher_set_flags(tctx->essiv_cipher,
+				crypto_skcipher_get_flags(tfm) &
+				CRYPTO_TFM_REQ_MASK);
+	err = crypto_cipher_setkey(tctx->essiv_cipher, salt,
+				   crypto_shash_digestsize(tctx->hash));
+	crypto_skcipher_set_flags(tfm,
+				  crypto_cipher_get_flags(tctx->essiv_cipher) &
+				  CRYPTO_TFM_RES_MASK);
+
+	return err;
+}
+
+static int essiv_aead_setkey(struct crypto_aead *tfm, const u8 *key,
+			     unsigned int keylen)
+{
+	struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
+	SHASH_DESC_ON_STACK(desc, tctx->hash);
+	struct crypto_authenc_keys keys;
+	u8 salt[HASH_MAX_DIGESTSIZE];
+	int err;
+
+	crypto_aead_clear_flags(tctx->u.aead, CRYPTO_TFM_REQ_MASK);
+	crypto_aead_set_flags(tctx->u.aead, crypto_aead_get_flags(tfm) &
+					    CRYPTO_TFM_REQ_MASK);
+	err = crypto_aead_setkey(tctx->u.aead, key, keylen);
+	crypto_aead_set_flags(tfm, crypto_aead_get_flags(tctx->u.aead) &
+				   CRYPTO_TFM_RES_MASK);
+	if (err)
+		return err;
+
+	if (crypto_authenc_extractkeys(&keys, key, keylen) != 0) {
+		crypto_aead_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+		return -EINVAL;
+	}
+
+	desc->tfm = tctx->hash;
+	err = crypto_shash_init(desc) ?:
+	      crypto_shash_update(desc, keys.enckey, keys.enckeylen) ?:
+	      crypto_shash_finup(desc, keys.authkey, keys.authkeylen, salt);
+	if (err)
+		return err;
+
+	crypto_cipher_clear_flags(tctx->essiv_cipher, CRYPTO_TFM_REQ_MASK);
+	crypto_cipher_set_flags(tctx->essiv_cipher, crypto_aead_get_flags(tfm) &
+						    CRYPTO_TFM_REQ_MASK);
+	err = crypto_cipher_setkey(tctx->essiv_cipher, salt,
+				   crypto_shash_digestsize(tctx->hash));
+	crypto_aead_set_flags(tfm, crypto_cipher_get_flags(tctx->essiv_cipher) &
+				   CRYPTO_TFM_RES_MASK);
+
+	return err;
+}
+
+static int essiv_aead_setauthsize(struct crypto_aead *tfm,
+				  unsigned int authsize)
+{
+	struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
+
+	return crypto_aead_setauthsize(tctx->u.aead, authsize);
+}
+
+static void essiv_skcipher_done(struct crypto_async_request *areq, int err)
+{
+	struct skcipher_request *req = areq->data;
+
+	skcipher_request_complete(req, err);
+}
+
+static int essiv_skcipher_crypt(struct skcipher_request *req, bool enc)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	const struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
+	struct skcipher_request *subreq = skcipher_request_ctx(req);
+
+	crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
+
+	skcipher_request_set_tfm(subreq, tctx->u.skcipher);
+	skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
+				   req->iv);
+	skcipher_request_set_callback(subreq, skcipher_request_flags(req),
+				      essiv_skcipher_done, req);
+
+	return enc ? crypto_skcipher_encrypt(subreq) :
+		     crypto_skcipher_decrypt(subreq);
+}
+
+static int essiv_skcipher_encrypt(struct skcipher_request *req)
+{
+	return essiv_skcipher_crypt(req, true);
+}
+
+static int essiv_skcipher_decrypt(struct skcipher_request *req)
+{
+	return essiv_skcipher_crypt(req, false);
+}
+
+static void essiv_aead_done(struct crypto_async_request *areq, int err)
+{
+	struct aead_request *req = areq->data;
+	struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
+
+	if (rctx->assoc)
+		kfree(rctx->assoc);
+	aead_request_complete(req, err);
+}
+
+static int essiv_aead_crypt(struct aead_request *req, bool enc)
+{
+	struct crypto_aead *tfm = crypto_aead_reqtfm(req);
+	const struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
+	struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
+	struct aead_request *subreq = &rctx->aead_req;
+	struct scatterlist *src = req->src;
+	int err;
+
+	crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
+
+	/*
+	 * dm-crypt embeds the sector number and the IV in the AAD region, so
+	 * we have to copy the converted IV into the right scatterlist before
+	 * we pass it on.
+	 */
+	rctx->assoc = NULL;
+	if (req->src == req->dst || !enc) {
+		scatterwalk_map_and_copy(req->iv, req->dst,
+					 req->assoclen - crypto_aead_ivsize(tfm),
+					 crypto_aead_ivsize(tfm), 1);
+	} else {
+		u8 *iv = (u8 *)aead_request_ctx(req) + tctx->ivoffset;
+		int ivsize = crypto_aead_ivsize(tfm);
+		int ssize = req->assoclen - ivsize;
+		struct scatterlist *sg;
+		int nents;
+
+		if (ssize < 0)
+			return -EINVAL;
+
+		nents = sg_nents_for_len(req->src, ssize);
+		if (nents < 0)
+			return -EINVAL;
+
+		memcpy(iv, req->iv, ivsize);
+		sg_init_table(rctx->sg, 4);
+
+		if (unlikely(nents > 1)) {
+			/*
+			 * This is a case that rarely occurs in practice, but
+			 * for correctness, we have to deal with it nonetheless.
+			 */
+			rctx->assoc = kmalloc(ssize, GFP_ATOMIC);
+			if (!rctx->assoc)
+				return -ENOMEM;
+
+			scatterwalk_map_and_copy(rctx->assoc, req->src, 0,
+						 ssize, 0);
+			sg_set_buf(rctx->sg, rctx->assoc, ssize);
+		} else {
+			sg_set_page(rctx->sg, sg_page(req->src), ssize,
+				    req->src->offset);
+		}
+
+		sg_set_buf(rctx->sg + 1, iv, ivsize);
+		sg = scatterwalk_ffwd(rctx->sg + 2, req->src, req->assoclen);
+		if (sg != rctx->sg + 2)
+			sg_chain(rctx->sg, 3, sg);
+
+		src = rctx->sg;
+	}
+
+	aead_request_set_tfm(subreq, tctx->u.aead);
+	aead_request_set_ad(subreq, req->assoclen);
+	aead_request_set_callback(subreq, aead_request_flags(req),
+				  essiv_aead_done, req);
+	aead_request_set_crypt(subreq, src, req->dst, req->cryptlen, req->iv);
+
+	err = enc ? crypto_aead_encrypt(subreq) :
+		    crypto_aead_decrypt(subreq);
+
+	if (rctx->assoc && err != -EINPROGRESS)
+		kfree(rctx->assoc);
+	return err;
+}
+
+static int essiv_aead_encrypt(struct aead_request *req)
+{
+	return essiv_aead_crypt(req, true);
+}
+
+static int essiv_aead_decrypt(struct aead_request *req)
+{
+	return essiv_aead_crypt(req, false);
+}
+
+static int essiv_init_tfm(struct essiv_instance_ctx *ictx,
+			  struct essiv_tfm_ctx *tctx)
+{
+	struct crypto_cipher *essiv_cipher;
+	struct crypto_shash *hash;
+	int err;
+
+	essiv_cipher = crypto_spawn_cipher(&ictx->essiv_cipher_spawn);
+	if (IS_ERR(essiv_cipher))
+		return PTR_ERR(essiv_cipher);
+
+	hash = crypto_spawn_shash(&ictx->hash_spawn);
+	if (IS_ERR(hash)) {
+		err = PTR_ERR(hash);
+		goto err_free_essiv_cipher;
+	}
+
+	tctx->essiv_cipher = essiv_cipher;
+	tctx->hash = hash;
+
+	return 0;
+
+err_free_essiv_cipher:
+	crypto_free_cipher(essiv_cipher);
+	return err;
+}
+
+static int essiv_skcipher_init_tfm(struct crypto_skcipher *tfm)
+{
+	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
+	struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
+	struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
+	struct crypto_skcipher *skcipher;
+	int err;
+
+	skcipher = crypto_spawn_skcipher(&ictx->u.skcipher_spawn);
+	if (IS_ERR(skcipher))
+		return PTR_ERR(skcipher);
+
+	crypto_skcipher_set_reqsize(tfm, sizeof(struct skcipher_request) +
+				         crypto_skcipher_reqsize(skcipher));
+
+	err = essiv_init_tfm(ictx, tctx);
+	if (err) {
+		crypto_free_skcipher(skcipher);
+		return err;
+	}
+
+	tctx->u.skcipher = skcipher;
+	return 0;
+}
+
+static int essiv_aead_init_tfm(struct crypto_aead *tfm)
+{
+	struct aead_instance *inst = aead_alg_instance(tfm);
+	struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
+	struct crypto_aead *aead;
+	unsigned int subreq_size;
+	int err;
+
+	BUILD_BUG_ON(offsetofend(struct essiv_aead_request_ctx, aead_req) !=
+		     sizeof(struct essiv_aead_request_ctx));
+
+	aead = crypto_spawn_aead(&ictx->u.aead_spawn);
+	if (IS_ERR(aead))
+		return PTR_ERR(aead);
+
+	subreq_size = FIELD_SIZEOF(struct essiv_aead_request_ctx, aead_req) +
+		      crypto_aead_reqsize(aead);
+
+	tctx->ivoffset = offsetof(struct essiv_aead_request_ctx, aead_req) +
+			 subreq_size;
+	crypto_aead_set_reqsize(tfm, tctx->ivoffset + crypto_aead_ivsize(aead));
+
+	err = essiv_init_tfm(ictx, tctx);
+	if (err) {
+		crypto_free_aead(aead);
+		return err;
+	}
+
+	tctx->u.aead = aead;
+	return 0;
+}
+
+static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm)
+{
+	struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
+
+	crypto_free_skcipher(tctx->u.skcipher);
+	crypto_free_cipher(tctx->essiv_cipher);
+	crypto_free_shash(tctx->hash);
+}
+
+static void essiv_aead_exit_tfm(struct crypto_aead *tfm)
+{
+	struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
+
+	crypto_free_aead(tctx->u.aead);
+	crypto_free_cipher(tctx->essiv_cipher);
+	crypto_free_shash(tctx->hash);
+}
+
+static void essiv_skcipher_free_instance(struct skcipher_instance *inst)
+{
+	struct essiv_instance_ctx *ictx = skcipher_instance_ctx(inst);
+
+	crypto_drop_skcipher(&ictx->u.skcipher_spawn);
+	crypto_drop_spawn(&ictx->essiv_cipher_spawn);
+	crypto_drop_shash(&ictx->hash_spawn);
+	kfree(inst);
+}
+
+static void essiv_aead_free_instance(struct aead_instance *inst)
+{
+	struct essiv_instance_ctx *ictx = aead_instance_ctx(inst);
+
+	crypto_drop_aead(&ictx->u.aead_spawn);
+	crypto_drop_spawn(&ictx->essiv_cipher_spawn);
+	crypto_drop_shash(&ictx->hash_spawn);
+	kfree(inst);
+}
+
+static bool parse_cipher_name(char *essiv_cipher_name, const char *cra_name)
+{
+	const char *p, *q;
+	int len;
+
+	/* find the last opening parens */
+	p = strrchr(cra_name, '(');
+	if (!p++)
+		return false;
+
+	/* find the first closing parens in the tail of the string */
+	q = strchr(p, ')');
+	if (!q)
+		return false;
+
+	len = q - p;
+	if (len >= CRYPTO_MAX_ALG_NAME)
+		return false;
+
+	memcpy(essiv_cipher_name, p, len);
+	essiv_cipher_name[len] = '\0';
+	return true;
+}
+
+static bool essiv_supported_algorithms(struct crypto_alg *essiv_cipher_alg,
+				       struct shash_alg *hash_alg,
+				       int ivsize)
+{
+	if (hash_alg->digestsize < essiv_cipher_alg->cra_cipher.cia_min_keysize ||
+	    hash_alg->digestsize > essiv_cipher_alg->cra_cipher.cia_max_keysize)
+		return false;
+
+	if (ivsize != essiv_cipher_alg->cra_blocksize)
+		return false;
+
+	if (crypto_shash_alg_has_setkey(hash_alg))
+		return false;
+
+	return true;
+}
+
+static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct crypto_attr_type *algt;
+	const char *inner_cipher_name;
+	const char *shash_name;
+	char essiv_cipher_name[CRYPTO_MAX_ALG_NAME];
+	struct skcipher_instance *skcipher_inst = NULL;
+	struct aead_instance *aead_inst = NULL;
+	struct crypto_instance *inst;
+	struct crypto_alg *base, *block_base;
+	struct essiv_instance_ctx *ictx;
+	struct skcipher_alg *skcipher_alg = NULL;
+	struct aead_alg *aead_alg = NULL;
+	struct crypto_alg *essiv_cipher_alg;
+	struct crypto_alg *_hash_alg;
+	struct shash_alg *hash_alg;
+	int ivsize;
+	u32 type;
+	int err;
+
+	algt = crypto_get_attr_type(tb);
+	if (IS_ERR(algt))
+		return PTR_ERR(algt);
+
+	inner_cipher_name = crypto_attr_alg_name(tb[1]);
+	if (IS_ERR(inner_cipher_name))
+		return PTR_ERR(inner_cipher_name);
+
+	shash_name = crypto_attr_alg_name(tb[2]);
+	if (IS_ERR(shash_name))
+		return PTR_ERR(shash_name);
+
+	type = algt->type & algt->mask;
+
+	switch (type) {
+	case CRYPTO_ALG_TYPE_BLKCIPHER:
+		skcipher_inst = kzalloc(sizeof(*skcipher_inst) +
+					sizeof(*ictx), GFP_KERNEL);
+		if (!skcipher_inst)
+			return -ENOMEM;
+		inst = skcipher_crypto_instance(skcipher_inst);
+		base = &skcipher_inst->alg.base;
+		ictx = crypto_instance_ctx(inst);
+
+		/* Symmetric cipher, e.g., "cbc(aes)" */
+		crypto_set_skcipher_spawn(&ictx->u.skcipher_spawn, inst);
+		err = crypto_grab_skcipher(&ictx->u.skcipher_spawn,
+					   inner_cipher_name, 0,
+					   crypto_requires_sync(algt->type,
+								algt->mask));
+		if (err)
+			goto out_free_inst;
+		skcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.skcipher_spawn);
+		block_base = &skcipher_alg->base;
+		ivsize = crypto_skcipher_alg_ivsize(skcipher_alg);
+		break;
+
+	case CRYPTO_ALG_TYPE_AEAD:
+		aead_inst = kzalloc(sizeof(*aead_inst) +
+				    sizeof(*ictx), GFP_KERNEL);
+		if (!aead_inst)
+			return -ENOMEM;
+		inst = aead_crypto_instance(aead_inst);
+		base = &aead_inst->alg.base;
+		ictx = crypto_instance_ctx(inst);
+
+		/* AEAD cipher, e.g., "authenc(hmac(sha256),cbc(aes))" */
+		crypto_set_aead_spawn(&ictx->u.aead_spawn, inst);
+		err = crypto_grab_aead(&ictx->u.aead_spawn,
+				       inner_cipher_name, 0,
+				       crypto_requires_sync(algt->type,
+							    algt->mask));
+		if (err)
+			goto out_free_inst;
+		aead_alg = crypto_spawn_aead_alg(&ictx->u.aead_spawn);
+		block_base = &aead_alg->base;
+		if (!strstarts(block_base->cra_name, "authenc(")) {
+			pr_warn("Only authenc() type AEADs are supported by ESSIV\n");
+			err = -EINVAL;
+			goto out_drop_skcipher;
+		}
+		ivsize = aead_alg->ivsize;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	if (!parse_cipher_name(essiv_cipher_name, block_base->cra_name)) {
+		pr_warn("Failed to parse ESSIV cipher name from skcipher cra_name\n");
+		err = -EINVAL;
+		goto out_drop_skcipher;
+	}
+
+	/* Block cipher, e.g., "aes" */
+	crypto_set_spawn(&ictx->essiv_cipher_spawn, inst);
+	err = crypto_grab_spawn(&ictx->essiv_cipher_spawn, essiv_cipher_name,
+				CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK);
+	if (err)
+		goto out_drop_skcipher;
+	essiv_cipher_alg = ictx->essiv_cipher_spawn.alg;
+
+	/* Synchronous hash, e.g., "sha256" */
+	_hash_alg = crypto_alg_mod_lookup(shash_name,
+					  CRYPTO_ALG_TYPE_SHASH,
+					  CRYPTO_ALG_TYPE_MASK);
+	if (IS_ERR(_hash_alg)) {
+		err = PTR_ERR(_hash_alg);
+		goto out_drop_essiv_cipher;
+	}
+	hash_alg = __crypto_shash_alg(_hash_alg);
+	err = crypto_init_shash_spawn(&ictx->hash_spawn, hash_alg, inst);
+	if (err)
+		goto out_put_hash;
+
+	/* Check the set of algorithms */
+	if (!essiv_supported_algorithms(essiv_cipher_alg, hash_alg, ivsize)) {
+		pr_warn("Unsupported essiv instantiation: essiv(%s,%s)\n",
+			block_base->cra_name,
+			hash_alg->base.cra_name);
+		err = -EINVAL;
+		goto out_drop_hash;
+	}
+
+	/* Instance fields */
+
+	err = -ENAMETOOLONG;
+	if (snprintf(base->cra_name, CRYPTO_MAX_ALG_NAME,
+		     "essiv(%s,%s)", block_base->cra_name,
+		     hash_alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
+		goto out_drop_hash;
+	if (snprintf(base->cra_driver_name, CRYPTO_MAX_ALG_NAME,
+		     "essiv(%s,%s)", block_base->cra_driver_name,
+		     hash_alg->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
+		goto out_drop_hash;
+
+	base->cra_flags		= block_base->cra_flags & CRYPTO_ALG_ASYNC;
+	base->cra_blocksize	= block_base->cra_blocksize;
+	base->cra_ctxsize	= sizeof(struct essiv_tfm_ctx);
+	base->cra_alignmask	= block_base->cra_alignmask;
+	base->cra_priority	= block_base->cra_priority;
+
+	if (type == CRYPTO_ALG_TYPE_BLKCIPHER) {
+		skcipher_inst->alg.setkey	= essiv_skcipher_setkey;
+		skcipher_inst->alg.encrypt	= essiv_skcipher_encrypt;
+		skcipher_inst->alg.decrypt	= essiv_skcipher_decrypt;
+		skcipher_inst->alg.init		= essiv_skcipher_init_tfm;
+		skcipher_inst->alg.exit		= essiv_skcipher_exit_tfm;
+
+		skcipher_inst->alg.min_keysize	= crypto_skcipher_alg_min_keysize(skcipher_alg);
+		skcipher_inst->alg.max_keysize	= crypto_skcipher_alg_max_keysize(skcipher_alg);
+		skcipher_inst->alg.ivsize	= ivsize;
+		skcipher_inst->alg.chunksize	= crypto_skcipher_alg_chunksize(skcipher_alg);
+		skcipher_inst->alg.walksize	= crypto_skcipher_alg_walksize(skcipher_alg);
+
+		skcipher_inst->free		= essiv_skcipher_free_instance;
+
+		err = skcipher_register_instance(tmpl, skcipher_inst);
+	} else {
+		aead_inst->alg.setkey		= essiv_aead_setkey;
+		aead_inst->alg.setauthsize	= essiv_aead_setauthsize;
+		aead_inst->alg.encrypt		= essiv_aead_encrypt;
+		aead_inst->alg.decrypt		= essiv_aead_decrypt;
+		aead_inst->alg.init		= essiv_aead_init_tfm;
+		aead_inst->alg.exit		= essiv_aead_exit_tfm;
+
+		aead_inst->alg.ivsize		= ivsize;
+		aead_inst->alg.maxauthsize	= crypto_aead_alg_maxauthsize(aead_alg);
+		aead_inst->alg.chunksize	= crypto_aead_alg_chunksize(aead_alg);
+
+		aead_inst->free			= essiv_aead_free_instance;
+
+		err = aead_register_instance(tmpl, aead_inst);
+	}
+
+	if (err)
+		goto out_drop_hash;
+
+	crypto_mod_put(_hash_alg);
+	return 0;
+
+out_drop_hash:
+	crypto_drop_shash(&ictx->hash_spawn);
+out_put_hash:
+	crypto_mod_put(_hash_alg);
+out_drop_essiv_cipher:
+	crypto_drop_spawn(&ictx->essiv_cipher_spawn);
+out_drop_skcipher:
+	if (type == CRYPTO_ALG_TYPE_BLKCIPHER)
+		crypto_drop_skcipher(&ictx->u.skcipher_spawn);
+	else
+		crypto_drop_aead(&ictx->u.aead_spawn);
+out_free_inst:
+	kfree(skcipher_inst);
+	kfree(aead_inst);
+	return err;
+}
+
+/* essiv(cipher_name, shash_name) */
+static struct crypto_template essiv_tmpl = {
+	.name	= "essiv",
+	.create	= essiv_create,
+	.module	= THIS_MODULE,
+};
+
+static int __init essiv_module_init(void)
+{
+	return crypto_register_template(&essiv_tmpl);
+}
+
+static void __exit essiv_module_exit(void)
+{
+	crypto_unregister_template(&essiv_tmpl);
+}
+
+subsys_initcall(essiv_module_init);
+module_exit(essiv_module_exit);
+
+MODULE_DESCRIPTION("ESSIV skcipher/aead wrapper for block encryption");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_CRYPTO("essiv");