| Message ID | 20190619162921.12509-2-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | crypto: switch to crypto API for ESSIV generation | expand |
On Wed, Jun 19, 2019 at 06:29:16PM +0200, Ard Biesheuvel wrote: > diff --git a/crypto/essiv.c b/crypto/essiv.c > new file mode 100644 > index 000000000000..45e9d10b8614 > --- /dev/null > +++ b/crypto/essiv.c > @@ -0,0 +1,630 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * ESSIV skcipher template for block encryption skcipher and aead A few sentences summary of what this file is for might also be useful to future readers. > + * > + * 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" > + > +#define ESSIV_IV_SIZE sizeof(u64) // IV size of the outer algo > +#define MAX_INNER_IV_SIZE 16 // max IV size of inner algo Why does the outer algorithm declare a smaller IV size? Shouldn't it just be the same as the inner algorithm's? > +struct essiv_instance_ctx { > + union { > + struct crypto_skcipher_spawn blockcipher_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 *blockcipher; > + struct crypto_aead *aead; > + } u; > + struct crypto_cipher *essiv_cipher; > + struct crypto_shash *hash; > +}; Can you fix the naming: 'blockcipher' => 'skcipher' everywhere? > +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); > + unsigned int saltsize; > + u8 *salt; > + int err; > + > + crypto_skcipher_clear_flags(tctx->u.blockcipher, CRYPTO_TFM_REQ_MASK); > + crypto_skcipher_set_flags(tctx->u.blockcipher, > + crypto_skcipher_get_flags(tfm) & > + CRYPTO_TFM_REQ_MASK); > + err = crypto_skcipher_setkey(tctx->u.blockcipher, key, keylen); > + crypto_skcipher_set_flags(tfm, > + crypto_skcipher_get_flags(tctx->u.blockcipher) & > + CRYPTO_TFM_RES_MASK); > + if (err) > + return err; > + > + saltsize = crypto_shash_digestsize(tctx->hash); > + salt = kmalloc(saltsize, GFP_KERNEL); > + if (!salt) > + return -ENOMEM; This could be a stack buffer of length HASH_MAX_DIGESTSIZE (64 bytes). Same in essiv_aead_setkey(). > + > + desc->tfm = tctx->hash; > + crypto_shash_digest(desc, key, keylen, salt); Need to check for error from crypto_shash_digest(). Similarly in essiv_aead_setkey(). > +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 *blockcipher; > + unsigned int subreq_size; > + int err; > + > + BUILD_BUG_ON(offsetofend(struct essiv_skcipher_request_ctx, > + blockcipher_req) != > + sizeof(struct essiv_skcipher_request_ctx)); > + > + blockcipher = crypto_spawn_skcipher(&ictx->u.blockcipher_spawn); > + if (IS_ERR(blockcipher)) > + return PTR_ERR(blockcipher); > + > + subreq_size = FIELD_SIZEOF(struct essiv_skcipher_request_ctx, > + blockcipher_req) + > + crypto_skcipher_reqsize(blockcipher); > + > + crypto_skcipher_set_reqsize(tfm, offsetof(struct essiv_skcipher_request_ctx, > + blockcipher_req) + subreq_size); > + > + err = essiv_init_tfm(ictx, tctx); > + if (err) > + crypto_free_skcipher(blockcipher); Should return in this error case, rather than going ahead and setting tctx->u.blockcipher. > + > + tctx->u.blockcipher = blockcipher; > + return err; > +} > + > +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); > + > + crypto_aead_set_reqsize(tfm, offsetof(struct essiv_aead_request_ctx, > + aead_req) + subreq_size); > + > + err = essiv_init_tfm(ictx, tctx); > + if (err) > + crypto_free_aead(aead); Same here. > +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 (ivsize > MAX_INNER_IV_SIZE) > + return false; > + > + return true; > +} Also check that the hash algorithm is unkeyed? > + > +static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb) > +{ > + struct crypto_attr_type *algt; > + const char *blockcipher_name; > + const char *essiv_cipher_name; > + const char *shash_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 *blockcipher_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); > + > + blockcipher_name = crypto_attr_alg_name(tb[1]); > + if (IS_ERR(blockcipher_name)) > + return PTR_ERR(blockcipher_name); > + > + essiv_cipher_name = crypto_attr_alg_name(tb[2]); > + if (IS_ERR(essiv_cipher_name)) > + return PTR_ERR(essiv_cipher_name); > + > + shash_name = crypto_attr_alg_name(tb[3]); > + 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); > + > + /* Block cipher, e.g. "cbc(aes)" */ > + crypto_set_skcipher_spawn(&ictx->u.blockcipher_spawn, inst); > + err = crypto_grab_skcipher(&ictx->u.blockcipher_spawn, > + blockcipher_name, 0, > + crypto_requires_sync(algt->type, > + algt->mask)); > + if (err) > + goto out_free_inst; > + blockcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.blockcipher_spawn); > + block_base = &blockcipher_alg->base; > + ivsize = blockcipher_alg->ivsize; This may need to be crypto_skcipher_alg_ivsize(), since the "skcipher" algorithm could actually be a "blkcipher" or "ablkcipher". > +out_drop_blockcipher: > + if (type == CRYPTO_ALG_TYPE_BLKCIPHER) { > + crypto_drop_skcipher(&ictx->u.blockcipher_spawn); > + } else { > + crypto_drop_aead(&ictx->u.aead_spawn); > + } Unnecessary braces. Thanks, - Eric
On Wed, Jun 19, 2019 at 06:04:17PM -0700, Eric Biggers wrote: > > > +#define ESSIV_IV_SIZE sizeof(u64) // IV size of the outer algo > > +#define MAX_INNER_IV_SIZE 16 // max IV size of inner algo > > Why does the outer algorithm declare a smaller IV size? Shouldn't it just be > the same as the inner algorithm's? In general we allow outer algorithms to have distinct IV sizes compared to the inner algorithm. For example, rfc4106 has a different IV size compared to gcm. In this case, the outer IV size is the block number so that's presumably why 64 bits is sufficient. Do you forsee a case where we need 128-bit block numbers? Cheers,
On Thu, Jun 20, 2019 at 09:13:25AM +0800, Herbert Xu wrote: > On Wed, Jun 19, 2019 at 06:04:17PM -0700, Eric Biggers wrote: > > > > > +#define ESSIV_IV_SIZE sizeof(u64) // IV size of the outer algo > > > +#define MAX_INNER_IV_SIZE 16 // max IV size of inner algo > > > > Why does the outer algorithm declare a smaller IV size? Shouldn't it just be > > the same as the inner algorithm's? > > In general we allow outer algorithms to have distinct IV sizes > compared to the inner algorithm. For example, rfc4106 has a > different IV size compared to gcm. > > In this case, the outer IV size is the block number so that's > presumably why 64 bits is sufficient. Do you forsee a case where > we need 128-bit block numbers? Actually this reminds me, the essiv template needs to be able to handle multiple blocks/sectors, as otherwise this will still only be able to push a single block/sector to the hardware at a time. Thanks,
On Thu, 20 Jun 2019 at 03:14, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > On Wed, Jun 19, 2019 at 06:04:17PM -0700, Eric Biggers wrote: > > > > > +#define ESSIV_IV_SIZE sizeof(u64) // IV size of the outer algo > > > +#define MAX_INNER_IV_SIZE 16 // max IV size of inner algo > > > > Why does the outer algorithm declare a smaller IV size? Shouldn't it just be > > the same as the inner algorithm's? > > In general we allow outer algorithms to have distinct IV sizes > compared to the inner algorithm. For example, rfc4106 has a > different IV size compared to gcm. > > In this case, the outer IV size is the block number so that's > presumably why 64 bits is sufficient. Do you forsee a case where > we need 128-bit block numbers? > Indeed, the whole point of this template is that it turns a 64-bit sector number into a n-bit IV, where n equals the block size of the essiv cipher, and its min/max keysize covers the digest size of the shash. I don't think it makes sense to generalize this further, and if I understand the feedback from Herbert and Gilad correctly, it would even be better to define the input IV as a LE 64-bit counter explicitly, so we can auto increment it between sectors. But that leaves the question how to convey the sector size to the template. Gilad suggests essiv(cbc(aes),aes,sha256,xxx) where xxx is the sector size, and incoming requests whose cryptlen is an exact multiple of the sector size will have their LE counter auto incremented between sectors. Note that we could make it optional for now, and default to 4k, but I will at least have to parse the argument if it is present and reject values != 4096 Is this the right approach? Or are there better ways to convey this information when instantiating the template? Also, it seems to me that the dm-crypt and fscrypt layers would require major surgery in order to take advantage of this.
On Thu, Jun 20, 2019 at 09:30:41AM +0200, Ard Biesheuvel wrote: > > Is this the right approach? Or are there better ways to convey this > information when instantiating the template? > Also, it seems to me that the dm-crypt and fscrypt layers would > require major surgery in order to take advantage of this. My preference would be to encode the sector size into the key. Hardware that can only support some sector sizes can use fallbacks as usual. Cheers,
On Thu, Jun 20, 2019 at 09:30:41AM +0200, Ard Biesheuvel wrote: > > Is this the right approach? Or are there better ways to convey this > information when instantiating the template? > Also, it seems to me that the dm-crypt and fscrypt layers would > require major surgery in order to take advantage of this. Oh and you don't have to make dm-crypt use it from the start. That is, you can just make things simple by doing it one sector at a time in the dm-crypt code even though the underlying essiv code supports multiple sectors. Someone who cares about this is sure to come along and fix it later. Cheers,
On Thu, 20 Jun 2019 at 14:53, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > On Thu, Jun 20, 2019 at 09:30:41AM +0200, Ard Biesheuvel wrote: > > > > Is this the right approach? Or are there better ways to convey this > > information when instantiating the template? > > Also, it seems to me that the dm-crypt and fscrypt layers would > > require major surgery in order to take advantage of this. > > Oh and you don't have to make dm-crypt use it from the start. That > is, you can just make things simple by doing it one sector at a > time in the dm-crypt code even though the underlying essiv code > supports multiple sectors. > > Someone who cares about this is sure to come along and fix it later. > It also depend on how realistic it is that we will need to support arbitrary sector sizes in the future. I mean, if we decide today that essiv() uses an implicit sector size of 4k, we can always add essiv64k() later, rather than adding lots of complexity now that we are never going to use. Note that ESSIV is already more or less deprecated, so there is really no point in inventing these weird and wonderful things if we want people to move to XTS and plain IV generation instead.
On Thu, 20 Jun 2019 at 15:02, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > > On Thu, 20 Jun 2019 at 14:53, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > > > On Thu, Jun 20, 2019 at 09:30:41AM +0200, Ard Biesheuvel wrote: > > > > > > Is this the right approach? Or are there better ways to convey this > > > information when instantiating the template? > > > Also, it seems to me that the dm-crypt and fscrypt layers would > > > require major surgery in order to take advantage of this. > > > > Oh and you don't have to make dm-crypt use it from the start. That > > is, you can just make things simple by doing it one sector at a > > time in the dm-crypt code even though the underlying essiv code > > supports multiple sectors. > > > > Someone who cares about this is sure to come along and fix it later. > > > > It also depend on how realistic it is that we will need to support > arbitrary sector sizes in the future. I mean, if we decide today that > essiv() uses an implicit sector size of 4k, we can always add > essiv64k() later, rather than adding lots of complexity now that we > are never going to use. Note that ESSIV is already more or less > deprecated, so there is really no point in inventing these weird and > wonderful things if we want people to move to XTS and plain IV > generation instead. Never mind, the sector size is already variable ...
On Thu, Jun 20, 2019 at 03:02:04PM +0200, Ard Biesheuvel wrote: > > It also depend on how realistic it is that we will need to support > arbitrary sector sizes in the future. I mean, if we decide today that > essiv() uses an implicit sector size of 4k, we can always add > essiv64k() later, rather than adding lots of complexity now that we > are never going to use. Note that ESSIV is already more or less > deprecated, so there is really no point in inventing these weird and > wonderful things if we want people to move to XTS and plain IV > generation instead. Well whatever we do for ESSIV should also extend to other IV generators in dm-crypt so that potentially we can have a single interface for dm-crypt multi-sector processing in future (IOW you don't have special code for ESSIV vs. other algos). That is why we should get the ESSIV interface right as it could serve as an example for future implementations. What do the dm-crypt people think? Are you ever going to need processing in units other than 4K? Cheers,
On Thu, 20 Jun 2019 at 15:40, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > On Thu, Jun 20, 2019 at 03:02:04PM +0200, Ard Biesheuvel wrote: > > > > It also depend on how realistic it is that we will need to support > > arbitrary sector sizes in the future. I mean, if we decide today that > > essiv() uses an implicit sector size of 4k, we can always add > > essiv64k() later, rather than adding lots of complexity now that we > > are never going to use. Note that ESSIV is already more or less > > deprecated, so there is really no point in inventing these weird and > > wonderful things if we want people to move to XTS and plain IV > > generation instead. > > Well whatever we do for ESSIV should also extend to other IV > generators in dm-crypt so that potentially we can have a single > interface for dm-crypt multi-sector processing in future (IOW > you don't have special code for ESSIV vs. other algos). > > That is why we should get the ESSIV interface right as it could > serve as an example for future implementations. > > What do the dm-crypt people think? Are you ever going to need > processing in units other than 4K? > We'd need at least 512 and 4k for dm-crypt, but I don't think the sector size is limited at all tbh
On Thu, Jun 20, 2019 at 09:30:41AM +0200, Ard Biesheuvel wrote: > On Thu, 20 Jun 2019 at 03:14, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > > > On Wed, Jun 19, 2019 at 06:04:17PM -0700, Eric Biggers wrote: > > > > > > > +#define ESSIV_IV_SIZE sizeof(u64) // IV size of the outer algo > > > > +#define MAX_INNER_IV_SIZE 16 // max IV size of inner algo > > > > > > Why does the outer algorithm declare a smaller IV size? Shouldn't it just be > > > the same as the inner algorithm's? > > > > In general we allow outer algorithms to have distinct IV sizes > > compared to the inner algorithm. For example, rfc4106 has a > > different IV size compared to gcm. > > > > In this case, the outer IV size is the block number so that's > > presumably why 64 bits is sufficient. Do you forsee a case where > > we need 128-bit block numbers? > > > > Indeed, the whole point of this template is that it turns a 64-bit > sector number into a n-bit IV, where n equals the block size of the > essiv cipher, and its min/max keysize covers the digest size of the > shash. > > I don't think it makes sense to generalize this further, and if I > understand the feedback from Herbert and Gilad correctly, it would > even be better to define the input IV as a LE 64-bit counter > explicitly, so we can auto increment it between sectors. > I was understanding ESSIV at a more abstract level, where you pass in some IV (which may or may not contain a sector number of some particular length and endianness) and it encrypts it. I see that both fscrypt and dm-crypt use the convention of a __le64 sector number though, so it's probably reasonable to define the IV to be that. A brief comment explaining this might be helpful, though. - Eric
On Thu, Jun 20, 2019 at 03:53:45PM +0200, Ard Biesheuvel wrote: > > We'd need at least 512 and 4k for dm-crypt, but I don't think the > sector size is limited at all tbh In that case my preference would be to encode this into the key and hardware that encounters unsupported sector sizes can use a fallback. Thanks,
On Fri, 21 Jun 2019 at 03:07, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > On Thu, Jun 20, 2019 at 03:53:45PM +0200, Ard Biesheuvel wrote: > > > > We'd need at least 512 and 4k for dm-crypt, but I don't think the > > sector size is limited at all tbh > > In that case my preference would be to encode this into the key > and hardware that encounters unsupported sector sizes can use a > fallback. > OTOH, it also depends on what makes sense to implement in practice. Gilad, I suppose sector size 512 is an obvious win, since the OS always fetches at least 8 consective ones at a time. Do you see a benefit for other sector sizes as well?
On 20/06/2019 15:40, Herbert Xu wrote: > On Thu, Jun 20, 2019 at 03:02:04PM +0200, Ard Biesheuvel wrote: >> >> It also depend on how realistic it is that we will need to support >> arbitrary sector sizes in the future. I mean, if we decide today that >> essiv() uses an implicit sector size of 4k, we can always add >> essiv64k() later, rather than adding lots of complexity now that we >> are never going to use. Note that ESSIV is already more or less >> deprecated, so there is really no point in inventing these weird and >> wonderful things if we want people to move to XTS and plain IV >> generation instead. > > Well whatever we do for ESSIV should also extend to other IV > generators in dm-crypt so that potentially we can have a single > interface for dm-crypt multi-sector processing in future (IOW > you don't have special code for ESSIV vs. other algos). > > That is why we should get the ESSIV interface right as it could > serve as an example for future implementations. > > What do the dm-crypt people think? Are you ever going to need > processing in units other than 4K? For the "technical" limit, dm-crypt supports 512, 1024, 2048 and 4096-byte encryption sector size (power of two) since commit 8f0009a225171cc1b76a6b443de5137b26e1374b. As the commit says, the 4k limit is because of page limit where whole IO must fit (4k is minimal page size). I do not want to introduce devices that are created on some architecture and cannot be opened elsewhere with a smaller page size. But maybe some reason appears, or there is some trick we did not tried... (I guess fs has the same limits?) Milan
diff --git a/crypto/Kconfig b/crypto/Kconfig index 3d056e7da65f..1aa47087c1a2 100644 --- a/crypto/Kconfig +++ b/crypto/Kconfig @@ -1917,6 +1917,10 @@ config CRYPTO_STATS config CRYPTO_HASH_INFO bool +config CRYPTO_ESSIV + tristate + select CRYPTO_AUTHENC + source "drivers/crypto/Kconfig" source "crypto/asymmetric_keys/Kconfig" source "certs/Kconfig" diff --git a/crypto/Makefile b/crypto/Makefile index 266a4cdbb9e2..ad1d99ba6d56 100644 --- a/crypto/Makefile +++ b/crypto/Makefile @@ -148,6 +148,7 @@ 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..45e9d10b8614 --- /dev/null +++ b/crypto/essiv.c @@ -0,0 +1,630 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * ESSIV skcipher template for block encryption + * + * 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" + +#define ESSIV_IV_SIZE sizeof(u64) // IV size of the outer algo +#define MAX_INNER_IV_SIZE 16 // max IV size of inner algo + +struct essiv_instance_ctx { + union { + struct crypto_skcipher_spawn blockcipher_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 *blockcipher; + struct crypto_aead *aead; + } u; + struct crypto_cipher *essiv_cipher; + struct crypto_shash *hash; +}; + +struct essiv_skcipher_request_ctx { + u8 iv[MAX_INNER_IV_SIZE]; + struct skcipher_request blockcipher_req; +}; + +struct essiv_aead_request_ctx { + u8 iv[MAX_INNER_IV_SIZE]; + struct scatterlist src[4], dst[4]; + 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); + unsigned int saltsize; + u8 *salt; + int err; + + crypto_skcipher_clear_flags(tctx->u.blockcipher, CRYPTO_TFM_REQ_MASK); + crypto_skcipher_set_flags(tctx->u.blockcipher, + crypto_skcipher_get_flags(tfm) & + CRYPTO_TFM_REQ_MASK); + err = crypto_skcipher_setkey(tctx->u.blockcipher, key, keylen); + crypto_skcipher_set_flags(tfm, + crypto_skcipher_get_flags(tctx->u.blockcipher) & + CRYPTO_TFM_RES_MASK); + if (err) + return err; + + saltsize = crypto_shash_digestsize(tctx->hash); + salt = kmalloc(saltsize, GFP_KERNEL); + if (!salt) + return -ENOMEM; + + desc->tfm = tctx->hash; + crypto_shash_digest(desc, key, keylen, salt); + + 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, saltsize); + crypto_skcipher_set_flags(tfm, + crypto_cipher_get_flags(tctx->essiv_cipher) & + CRYPTO_TFM_RES_MASK); + + kzfree(salt); + 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; + unsigned int saltsize; + u8 *salt; + 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; + } + + saltsize = crypto_shash_digestsize(tctx->hash); + salt = kmalloc(saltsize, GFP_KERNEL); + if (!salt) + return -ENOMEM; + + desc->tfm = tctx->hash; + crypto_shash_init(desc); + crypto_shash_update(desc, keys.enckey, keys.enckeylen); + crypto_shash_finup(desc, keys.authkey, keys.authkeylen, salt); + + 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, saltsize); + crypto_aead_set_flags(tfm, crypto_cipher_get_flags(tctx->essiv_cipher) & + CRYPTO_TFM_RES_MASK); + + kzfree(salt); + 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 void essiv_aead_done(struct crypto_async_request *areq, int err) +{ + struct aead_request *req = areq->data; + + aead_request_complete(req, err); +} + +static void essiv_skcipher_prepare_subreq(struct skcipher_request *req) +{ + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + const struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); + struct essiv_skcipher_request_ctx *rctx = skcipher_request_ctx(req); + struct skcipher_request *subreq = &rctx->blockcipher_req; + + memset(rctx->iv, 0, crypto_cipher_blocksize(tctx->essiv_cipher)); + memcpy(rctx->iv, req->iv, crypto_skcipher_ivsize(tfm)); + + crypto_cipher_encrypt_one(tctx->essiv_cipher, rctx->iv, rctx->iv); + + skcipher_request_set_tfm(subreq, tctx->u.blockcipher); + skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen, + rctx->iv); + skcipher_request_set_callback(subreq, req->base.flags, + essiv_skcipher_done, req); +} + +static int essiv_aead_prepare_subreq(struct aead_request *req) +{ + 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); + int ivsize = crypto_cipher_blocksize(tctx->essiv_cipher); + int ssize = req->assoclen - crypto_aead_ivsize(tfm); + struct aead_request *subreq = &rctx->aead_req; + struct scatterlist *sg; + + /* + * dm-crypt embeds the sector number and the IV in the AAD region so we + * have to splice the converted IV into the subrequest that we pass on + * to the AEAD transform. This means we are tightly coupled to dm-crypt, + * but that should be the only user of this code in AEAD mode. + */ + if (ssize < 0 || sg_nents_for_len(req->src, ssize) != 1) + return -EINVAL; + + memset(rctx->iv, 0, ivsize); + memcpy(rctx->iv, req->iv, crypto_aead_ivsize(tfm)); + + crypto_cipher_encrypt_one(tctx->essiv_cipher, rctx->iv, rctx->iv); + + sg_init_table(rctx->src, 4); + sg_set_page(rctx->src, sg_page(req->src), ssize, req->src->offset); + sg_set_buf(rctx->src + 1, rctx->iv, ivsize); + sg = scatterwalk_ffwd(rctx->src + 2, req->src, req->assoclen); + if (sg != rctx->src + 2) + sg_chain(rctx->src, 3, sg); + + sg_init_table(rctx->dst, 4); + sg_set_page(rctx->dst, sg_page(req->dst), ssize, req->dst->offset); + sg_set_buf(rctx->dst + 1, rctx->iv, ivsize); + sg = scatterwalk_ffwd(rctx->dst + 2, req->dst, req->assoclen); + if (sg != rctx->dst + 2) + sg_chain(rctx->dst, 3, sg); + + aead_request_set_tfm(subreq, tctx->u.aead); + aead_request_set_crypt(subreq, rctx->src, rctx->dst, req->cryptlen, + rctx->iv); + aead_request_set_ad(subreq, ssize + ivsize); + aead_request_set_callback(subreq, req->base.flags, essiv_aead_done, req); + + return 0; +} + +static int essiv_skcipher_encrypt(struct skcipher_request *req) +{ + struct essiv_skcipher_request_ctx *rctx = skcipher_request_ctx(req); + + essiv_skcipher_prepare_subreq(req); + return crypto_skcipher_encrypt(&rctx->blockcipher_req); +} + +static int essiv_aead_encrypt(struct aead_request *req) +{ + struct essiv_aead_request_ctx *rctx = aead_request_ctx(req); + int err; + + err = essiv_aead_prepare_subreq(req); + if (err) + return err; + return crypto_aead_encrypt(&rctx->aead_req); +} + +static int essiv_skcipher_decrypt(struct skcipher_request *req) +{ + struct essiv_skcipher_request_ctx *rctx = skcipher_request_ctx(req); + + essiv_skcipher_prepare_subreq(req); + return crypto_skcipher_decrypt(&rctx->blockcipher_req); +} + +static int essiv_aead_decrypt(struct aead_request *req) +{ + struct essiv_aead_request_ctx *rctx = aead_request_ctx(req); + int err; + + err = essiv_aead_prepare_subreq(req); + if (err) + return err; + + essiv_aead_prepare_subreq(req); + return crypto_aead_decrypt(&rctx->aead_req); +} + +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 *blockcipher; + unsigned int subreq_size; + int err; + + BUILD_BUG_ON(offsetofend(struct essiv_skcipher_request_ctx, + blockcipher_req) != + sizeof(struct essiv_skcipher_request_ctx)); + + blockcipher = crypto_spawn_skcipher(&ictx->u.blockcipher_spawn); + if (IS_ERR(blockcipher)) + return PTR_ERR(blockcipher); + + subreq_size = FIELD_SIZEOF(struct essiv_skcipher_request_ctx, + blockcipher_req) + + crypto_skcipher_reqsize(blockcipher); + + crypto_skcipher_set_reqsize(tfm, offsetof(struct essiv_skcipher_request_ctx, + blockcipher_req) + subreq_size); + + err = essiv_init_tfm(ictx, tctx); + if (err) + crypto_free_skcipher(blockcipher); + + tctx->u.blockcipher = blockcipher; + return err; +} + +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); + + crypto_aead_set_reqsize(tfm, offsetof(struct essiv_aead_request_ctx, + aead_req) + subreq_size); + + err = essiv_init_tfm(ictx, tctx); + if (err) + crypto_free_aead(aead); + + tctx->u.aead = aead; + return err; +} + +static void essiv_skcipher_exit_tfm(struct crypto_skcipher *tfm) +{ + struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm); + + crypto_free_skcipher(tctx->u.blockcipher); + 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.blockcipher_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 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 (ivsize > MAX_INNER_IV_SIZE) + return false; + + return true; +} + +static int essiv_create(struct crypto_template *tmpl, struct rtattr **tb) +{ + struct crypto_attr_type *algt; + const char *blockcipher_name; + const char *essiv_cipher_name; + const char *shash_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 *blockcipher_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); + + blockcipher_name = crypto_attr_alg_name(tb[1]); + if (IS_ERR(blockcipher_name)) + return PTR_ERR(blockcipher_name); + + essiv_cipher_name = crypto_attr_alg_name(tb[2]); + if (IS_ERR(essiv_cipher_name)) + return PTR_ERR(essiv_cipher_name); + + shash_name = crypto_attr_alg_name(tb[3]); + 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); + + /* Block cipher, e.g. "cbc(aes)" */ + crypto_set_skcipher_spawn(&ictx->u.blockcipher_spawn, inst); + err = crypto_grab_skcipher(&ictx->u.blockcipher_spawn, + blockcipher_name, 0, + crypto_requires_sync(algt->type, + algt->mask)); + if (err) + goto out_free_inst; + blockcipher_alg = crypto_spawn_skcipher_alg(&ictx->u.blockcipher_spawn); + block_base = &blockcipher_alg->base; + ivsize = blockcipher_alg->ivsize; + 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, + blockcipher_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; + ivsize = aead_alg->ivsize; + break; + + default: + return -EINVAL; + } + + /* 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_blockcipher; + 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: (%s,%s,%s)\n", + block_base->cra_name, + essiv_cipher_alg->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,%s)", block_base->cra_name, + essiv_cipher_alg->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,%s)", + block_base->cra_driver_name, + essiv_cipher_alg->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(blockcipher_alg); + skcipher_inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(blockcipher_alg); + skcipher_inst->alg.ivsize = ESSIV_IV_SIZE; + skcipher_inst->alg.chunksize = blockcipher_alg->chunksize; + skcipher_inst->alg.walksize = blockcipher_alg->walksize; + + 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 = ESSIV_IV_SIZE; + aead_inst->alg.maxauthsize = aead_alg->maxauthsize; + aead_inst->alg.chunksize = aead_alg->chunksize; + + 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_blockcipher: + if (type == CRYPTO_ALG_TYPE_BLKCIPHER) { + crypto_drop_skcipher(&ictx->u.blockcipher_spawn); + } else { + crypto_drop_aead(&ictx->u.aead_spawn); + } +out_free_inst: + kfree(skcipher_inst); + kfree(aead_inst); + return err; +} + +/* essiv(blockcipher_name, 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");
Implement a template that wraps a (skcipher,cipher,shash) or (aead,cipher,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 | 4 + crypto/Makefile | 1 + crypto/essiv.c | 630 ++++++++++++++++++++ 3 files changed, 635 insertions(+)