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linux-next/crypto/cts.c
Ard Biesheuvel db91af0fbe crypto: algapi - make crypto_xor() and crypto_inc() alignment agnostic 
Instead of unconditionally forcing 4 byte alignment for all generic
chaining modes that rely on crypto_xor() or crypto_inc() (which may
result in unnecessary copying of data when the underlying hardware
can perform unaligned accesses efficiently), make those functions
deal with unaligned input explicitly, but only if the Kconfig symbol
HAVE_EFFICIENT_UNALIGNED_ACCESS is set. This will allow us to drop
the alignmasks from the CBC, CMAC, CTR, CTS, PCBC and SEQIV drivers.

For crypto_inc(), this simply involves making the 4-byte stride
conditional on HAVE_EFFICIENT_UNALIGNED_ACCESS being set, given that
it typically operates on 16 byte buffers.

For crypto_xor(), an algorithm is implemented that simply runs through
the input using the largest strides possible if unaligned accesses are
allowed. If they are not, an optimal sequence of memory accesses is
emitted that takes the relative alignment of the input buffers into
account, e.g., if the relative misalignment of dst and src is 4 bytes,
the entire xor operation will be completed using 4 byte loads and stores
(modulo unaligned bits at the start and end). Note that all expressions
involving misalign are simply eliminated by the compiler when
HAVE_EFFICIENT_UNALIGNED_ACCESS is defined.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2017-02-11 17:52:28 +08:00

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/*
* CTS: Cipher Text Stealing mode
*
* COPYRIGHT (c) 2008
* The Regents of the University of Michigan
* ALL RIGHTS RESERVED
*
* Permission is granted to use, copy, create derivative works
* and redistribute this software and such derivative works
* for any purpose, so long as the name of The University of
* Michigan is not used in any advertising or publicity
* pertaining to the use of distribution of this software
* without specific, written prior authorization. If the
* above copyright notice or any other identification of the
* University of Michigan is included in any copy of any
* portion of this software, then the disclaimer below must
* also be included.
*
* THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
* FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
* PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
* MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
* WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
* REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
* FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
* CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
* OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
* IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGES.
*/
/* Derived from various:
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*/
/*
* This is the Cipher Text Stealing mode as described by
* Section 8 of rfc2040 and referenced by rfc3962.
* rfc3962 includes errata information in its Appendix A.
*/
#include <crypto/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/log2.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <crypto/scatterwalk.h>
#include <linux/slab.h>
#include <linux/compiler.h>
struct crypto_cts_ctx {
struct crypto_skcipher *child;
};
struct crypto_cts_reqctx {
struct scatterlist sg[2];
unsigned offset;
struct skcipher_request subreq;
};
static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req)
{
struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
struct crypto_skcipher *child = ctx->child;
return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
crypto_skcipher_alignmask(tfm) + 1);
}
static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key,
unsigned int keylen)
{
struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
struct crypto_skcipher *child = ctx->child;
int err;
crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
CRYPTO_TFM_REQ_MASK);
err = crypto_skcipher_setkey(child, key, keylen);
crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
CRYPTO_TFM_RES_MASK);
return err;
}
static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
{
struct skcipher_request *req = areq->data;
if (err == -EINPROGRESS)
return;
skcipher_request_complete(req, err);
}
static int cts_cbc_encrypt(struct skcipher_request *req)
{
struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct skcipher_request *subreq = &rctx->subreq;
int bsize = crypto_skcipher_blocksize(tfm);
u8 d[bsize * 2] __aligned(__alignof__(u32));
struct scatterlist *sg;
unsigned int offset;
int lastn;
offset = rctx->offset;
lastn = req->cryptlen - offset;
sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
memset(d, 0, bsize);
scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
memzero_explicit(d, sizeof(d));
skcipher_request_set_callback(subreq, req->base.flags &
CRYPTO_TFM_REQ_MAY_BACKLOG,
cts_cbc_crypt_done, req);
skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
return crypto_skcipher_encrypt(subreq);
}
static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
{
struct skcipher_request *req = areq->data;
if (err)
goto out;
err = cts_cbc_encrypt(req);
if (err == -EINPROGRESS ||
(err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
return;
out:
skcipher_request_complete(req, err);
}
static int crypto_cts_encrypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
struct skcipher_request *subreq = &rctx->subreq;
int bsize = crypto_skcipher_blocksize(tfm);
unsigned int nbytes = req->cryptlen;
int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
unsigned int offset;
skcipher_request_set_tfm(subreq, ctx->child);
if (cbc_blocks <= 0) {
skcipher_request_set_callback(subreq, req->base.flags,
req->base.complete,
req->base.data);
skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
req->iv);
return crypto_skcipher_encrypt(subreq);
}
offset = cbc_blocks * bsize;
rctx->offset = offset;
skcipher_request_set_callback(subreq, req->base.flags,
crypto_cts_encrypt_done, req);
skcipher_request_set_crypt(subreq, req->src, req->dst,
offset, req->iv);
return crypto_skcipher_encrypt(subreq) ?:
cts_cbc_encrypt(req);
}
static int cts_cbc_decrypt(struct skcipher_request *req)
{
struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct skcipher_request *subreq = &rctx->subreq;
int bsize = crypto_skcipher_blocksize(tfm);
u8 d[bsize * 2] __aligned(__alignof__(u32));
struct scatterlist *sg;
unsigned int offset;
u8 *space;
int lastn;
offset = rctx->offset;
lastn = req->cryptlen - offset;
sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
/* 1. Decrypt Cn-1 (s) to create Dn */
scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
space = crypto_cts_reqctx_space(req);
crypto_xor(d + bsize, space, bsize);
/* 2. Pad Cn with zeros at the end to create C of length BB */
memset(d, 0, bsize);
scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
/* 3. Exclusive-or Dn with C to create Xn */
/* 4. Select the first Ln bytes of Xn to create Pn */
crypto_xor(d + bsize, d, lastn);
/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
/* 6. Decrypt En to create Pn-1 */
scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
memzero_explicit(d, sizeof(d));
skcipher_request_set_callback(subreq, req->base.flags &
CRYPTO_TFM_REQ_MAY_BACKLOG,
cts_cbc_crypt_done, req);
skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
return crypto_skcipher_decrypt(subreq);
}
static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
{
struct skcipher_request *req = areq->data;
if (err)
goto out;
err = cts_cbc_decrypt(req);
if (err == -EINPROGRESS ||
(err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
return;
out:
skcipher_request_complete(req, err);
}
static int crypto_cts_decrypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
struct skcipher_request *subreq = &rctx->subreq;
int bsize = crypto_skcipher_blocksize(tfm);
unsigned int nbytes = req->cryptlen;
int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
unsigned int offset;
u8 *space;
skcipher_request_set_tfm(subreq, ctx->child);
if (cbc_blocks <= 0) {
skcipher_request_set_callback(subreq, req->base.flags,
req->base.complete,
req->base.data);
skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
req->iv);
return crypto_skcipher_decrypt(subreq);
}
skcipher_request_set_callback(subreq, req->base.flags,
crypto_cts_decrypt_done, req);
space = crypto_cts_reqctx_space(req);
offset = cbc_blocks * bsize;
rctx->offset = offset;
if (cbc_blocks <= 1)
memcpy(space, req->iv, bsize);
else
scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
bsize, 0);
skcipher_request_set_crypt(subreq, req->src, req->dst,
offset, req->iv);
return crypto_skcipher_decrypt(subreq) ?:
cts_cbc_decrypt(req);
}
static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
{
struct skcipher_instance *inst = skcipher_alg_instance(tfm);
struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
struct crypto_skcipher *cipher;
unsigned reqsize;
unsigned bsize;
unsigned align;
cipher = crypto_spawn_skcipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
ctx->child = cipher;
align = crypto_skcipher_alignmask(tfm);
bsize = crypto_skcipher_blocksize(cipher);
reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
crypto_skcipher_reqsize(cipher),
crypto_tfm_ctx_alignment()) +
(align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
crypto_skcipher_set_reqsize(tfm, reqsize);
return 0;
}
static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
{
struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
crypto_free_skcipher(ctx->child);
}
static void crypto_cts_free(struct skcipher_instance *inst)
{
crypto_drop_skcipher(skcipher_instance_ctx(inst));
kfree(inst);
}
static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb)
{
struct crypto_skcipher_spawn *spawn;
struct skcipher_instance *inst;
struct crypto_attr_type *algt;
struct skcipher_alg *alg;
const char *cipher_name;
int err;
algt = crypto_get_attr_type(tb);
if (IS_ERR(algt))
return PTR_ERR(algt);
if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
return -EINVAL;
cipher_name = crypto_attr_alg_name(tb[1]);
if (IS_ERR(cipher_name))
return PTR_ERR(cipher_name);
inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
if (!inst)
return -ENOMEM;
spawn = skcipher_instance_ctx(inst);
crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
err = crypto_grab_skcipher(spawn, cipher_name, 0,
crypto_requires_sync(algt->type,
algt->mask));
if (err)
goto err_free_inst;
alg = crypto_spawn_skcipher_alg(spawn);
err = -EINVAL;
if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
goto err_drop_spawn;
if (strncmp(alg->base.cra_name, "cbc(", 4))
goto err_drop_spawn;
err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
&alg->base);
if (err)
goto err_drop_spawn;
inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
inst->alg.base.cra_priority = alg->base.cra_priority;
inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
inst->alg.ivsize = alg->base.cra_blocksize;
inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
inst->alg.init = crypto_cts_init_tfm;
inst->alg.exit = crypto_cts_exit_tfm;
inst->alg.setkey = crypto_cts_setkey;
inst->alg.encrypt = crypto_cts_encrypt;
inst->alg.decrypt = crypto_cts_decrypt;
inst->free = crypto_cts_free;
err = skcipher_register_instance(tmpl, inst);
if (err)
goto err_drop_spawn;
out:
return err;
err_drop_spawn:
crypto_drop_skcipher(spawn);
err_free_inst:
kfree(inst);
goto out;
}
static struct crypto_template crypto_cts_tmpl = {
.name = "cts",
.create = crypto_cts_create,
.module = THIS_MODULE,
};
static int __init crypto_cts_module_init(void)
{
return crypto_register_template(&crypto_cts_tmpl);
}
static void __exit crypto_cts_module_exit(void)
{
crypto_unregister_template(&crypto_cts_tmpl);
}
module_init(crypto_cts_module_init);
module_exit(crypto_cts_module_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
MODULE_ALIAS_CRYPTO("cts");
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