[linux.git] / crypto / cts.c

/*
 * 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 <[email protected]>
 */

/*
 * 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/algapi.h>
#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;

	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
					 CRYPTO_TFM_REQ_MASK);
	return crypto_skcipher_setkey(child, key, keylen);
}

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[MAX_CIPHER_BLOCKSIZE * 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)
		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;
	unsigned int offset;

	skcipher_request_set_tfm(subreq, ctx->child);

	if (nbytes < bsize)
		return -EINVAL;

	if (nbytes == bsize) {
		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 = rounddown(nbytes - 1, 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[MAX_CIPHER_BLOCKSIZE * 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)
		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;
	unsigned int offset;
	u8 *space;

	skcipher_request_set_tfm(subreq, ctx->child);

	if (nbytes < bsize)
		return -EINVAL;

	if (nbytes == bsize) {
		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 = rounddown(nbytes - 1, bsize);
	rctx->offset = offset;

	if (offset <= bsize)
		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 skcipher_alg *alg;
	u32 mask;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
	if (err)
		return err;

	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
	if (!inst)
		return -ENOMEM;

	spawn = skcipher_instance_ctx(inst);

	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
				   crypto_attr_alg_name(tb[1]), 0, 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_free_inst;

	if (strncmp(alg->base.cra_name, "cbc(", 4))
		goto err_free_inst;

	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
				  &alg->base);
	if (err)
		goto err_free_inst;

	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) {
err_free_inst:
		crypto_cts_free(inst);
	}
	return err;
}

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);
}

subsys_initcall(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");
Commit	Line	Data
76cb9521 KC	1	/*
	2	* CTS: Cipher Text Stealing mode
	3	*
	4	* COPYRIGHT (c) 2008
	5	* The Regents of the University of Michigan
	6	* ALL RIGHTS RESERVED
	7	*
	8	* Permission is granted to use, copy, create derivative works
	9	* and redistribute this software and such derivative works
	10	* for any purpose, so long as the name of The University of
	11	* Michigan is not used in any advertising or publicity
	12	* pertaining to the use of distribution of this software
	13	* without specific, written prior authorization. If the
	14	* above copyright notice or any other identification of the
	15	* University of Michigan is included in any copy of any
	16	* portion of this software, then the disclaimer below must
	17	* also be included.
	18	*
	19	* THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
	20	* FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
	21	* PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
	22	* MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
	23	* WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
	24	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
	25	* REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
	26	* FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
	27	* CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
	28	* OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
	29	* IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
	30	* SUCH DAMAGES.
	31	*/
	32
	33	/* Derived from various:
	34	* Copyright (c) 2006 Herbert Xu <[email protected]>
	35	*/
	36
	37	/*
	38	* This is the Cipher Text Stealing mode as described by
	39	* Section 8 of rfc2040 and referenced by rfc3962.
	40	* rfc3962 includes errata information in its Appendix A.
	41	*/
	42
6650c4de	43	#include <crypto/algapi.h>
0605c41c	44	#include <crypto/internal/skcipher.h>
76cb9521 KC	45	#include <linux/err.h>
	46	#include <linux/init.h>
	47	#include <linux/kernel.h>
	48	#include <linux/log2.h>
	49	#include <linux/module.h>
	50	#include <linux/scatterlist.h>
	51	#include <crypto/scatterwalk.h>
	52	#include <linux/slab.h>
d8c34b94	53	#include <linux/compiler.h>
76cb9521 KC	54
76cb9521 KC	55	struct crypto_cts_ctx {
0605c41c	56	struct crypto_skcipher *child;
76cb9521 KC	57	};
76cb9521 KC	58
0605c41c HX	59	struct crypto_cts_reqctx {
	60	struct scatterlist sg[2];
	61	unsigned offset;
	62	struct skcipher_request subreq;
	63	};
	64
	65	static inline u8 crypto_cts_reqctx_space(struct skcipher_request req)
76cb9521	66	{
0605c41c HX	67	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	68	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	69	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	70	struct crypto_skcipher *child = ctx->child;
76cb9521	71
0605c41c HX	72	return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
0605c41c HX	73	crypto_skcipher_alignmask(tfm) + 1);
76cb9521 KC	74	}
76cb9521 KC	75
0605c41c HX	76	static int crypto_cts_setkey(struct crypto_skcipher parent, const u8 key,
0605c41c HX	77	unsigned int keylen)
76cb9521	78	{
0605c41c HX	79	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
0605c41c HX	80	struct crypto_skcipher *child = ctx->child;
76cb9521	81
0605c41c HX	82	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	83	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
	84	CRYPTO_TFM_REQ_MASK);
af5034e8	85	return crypto_skcipher_setkey(child, key, keylen);
0605c41c	86	}
76cb9521	87
0605c41c HX	88	static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
	89	{
	90	struct skcipher_request *req = areq->data;
c4913c7b	91
0605c41c HX	92	if (err == -EINPROGRESS)
0605c41c HX	93	return;
76cb9521	94
0605c41c HX	95	skcipher_request_complete(req, err);
0605c41c HX	96	}
76cb9521	97
0605c41c HX	98	static int cts_cbc_encrypt(struct skcipher_request *req)
	99	{
	100	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	101	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	102	struct skcipher_request *subreq = &rctx->subreq;
	103	int bsize = crypto_skcipher_blocksize(tfm);
6650c4de	104	u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));
0605c41c HX	105	struct scatterlist *sg;
	106	unsigned int offset;
	107	int lastn;
	108
	109	offset = rctx->offset;
	110	lastn = req->cryptlen - offset;
	111
	112	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	113	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	114
	115	memset(d, 0, bsize);
	116	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	117
	118	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
	119	memzero_explicit(d, sizeof(d));
	120
	121	skcipher_request_set_callback(subreq, req->base.flags &
	122	CRYPTO_TFM_REQ_MAY_BACKLOG,
	123	cts_cbc_crypt_done, req);
	124	skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
	125	return crypto_skcipher_encrypt(subreq);
	126	}
76cb9521	127
0605c41c HX	128	static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
	129	{
	130	struct skcipher_request *req = areq->data;
76cb9521	131
0605c41c HX	132	if (err)
0605c41c HX	133	goto out;
76cb9521	134
0605c41c	135	err = cts_cbc_encrypt(req);
4e5b0ad5	136	if (err == -EINPROGRESS \|\| err == -EBUSY)
0605c41c	137	return;
76cb9521	138
0605c41c HX	139	out:
	140	skcipher_request_complete(req, err);
	141	}
76cb9521	142
0605c41c HX	143	static int crypto_cts_encrypt(struct skcipher_request *req)
	144	{
	145	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	146	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	147	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	148	struct skcipher_request *subreq = &rctx->subreq;
	149	int bsize = crypto_skcipher_blocksize(tfm);
	150	unsigned int nbytes = req->cryptlen;
0605c41c HX	151	unsigned int offset;
	152
	153	skcipher_request_set_tfm(subreq, ctx->child);
	154
c31a8719 EB	155	if (nbytes < bsize)
	156	return -EINVAL;
	157
	158	if (nbytes == bsize) {
0605c41c HX	159	skcipher_request_set_callback(subreq, req->base.flags,
	160	req->base.complete,
	161	req->base.data);
	162	skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
	163	req->iv);
	164	return crypto_skcipher_encrypt(subreq);
	165	}
76cb9521	166
c31a8719	167	offset = rounddown(nbytes - 1, bsize);
0605c41c	168	rctx->offset = offset;
76cb9521	169
0605c41c HX	170	skcipher_request_set_callback(subreq, req->base.flags,
	171	crypto_cts_encrypt_done, req);
	172	skcipher_request_set_crypt(subreq, req->src, req->dst,
	173	offset, req->iv);
76cb9521	174
0605c41c HX	175	return crypto_skcipher_encrypt(subreq) ?:
0605c41c HX	176	cts_cbc_encrypt(req);
76cb9521 KC	177	}
76cb9521 KC	178
0605c41c	179	static int cts_cbc_decrypt(struct skcipher_request *req)
76cb9521	180	{
0605c41c HX	181	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	182	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	183	struct skcipher_request *subreq = &rctx->subreq;
	184	int bsize = crypto_skcipher_blocksize(tfm);
6650c4de	185	u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));
0605c41c HX	186	struct scatterlist *sg;
	187	unsigned int offset;
	188	u8 *space;
	189	int lastn;
	190
	191	offset = rctx->offset;
	192	lastn = req->cryptlen - offset;
	193
	194	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	195
	196	/* 1. Decrypt Cn-1 (s) to create Dn */
	197	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	198	space = crypto_cts_reqctx_space(req);
	199	crypto_xor(d + bsize, space, bsize);
	200	/* 2. Pad Cn with zeros at the end to create C of length BB */
	201	memset(d, 0, bsize);
	202	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	203	/* 3. Exclusive-or Dn with C to create Xn */
	204	/* 4. Select the first Ln bytes of Xn to create Pn */
	205	crypto_xor(d + bsize, d, lastn);
	206
	207	/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
	208	memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
	209	/* 6. Decrypt En to create Pn-1 */
76cb9521	210
0605c41c HX	211	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
0605c41c HX	212	memzero_explicit(d, sizeof(d));
76cb9521	213
0605c41c HX	214	skcipher_request_set_callback(subreq, req->base.flags &
	215	CRYPTO_TFM_REQ_MAY_BACKLOG,
	216	cts_cbc_crypt_done, req);
	217
	218	skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
	219	return crypto_skcipher_decrypt(subreq);
76cb9521 KC	220	}
76cb9521 KC	221
0605c41c	222	static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
76cb9521	223	{
0605c41c	224	struct skcipher_request *req = areq->data;
76cb9521	225
0605c41c HX	226	if (err)
0605c41c HX	227	goto out;
c4913c7b	228
0605c41c	229	err = cts_cbc_decrypt(req);
4e5b0ad5	230	if (err == -EINPROGRESS \|\| err == -EBUSY)
0605c41c	231	return;
76cb9521	232
0605c41c HX	233	out:
	234	skcipher_request_complete(req, err);
	235	}
76cb9521	236
0605c41c HX	237	static int crypto_cts_decrypt(struct skcipher_request *req)
	238	{
	239	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	240	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	241	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	242	struct skcipher_request *subreq = &rctx->subreq;
	243	int bsize = crypto_skcipher_blocksize(tfm);
	244	unsigned int nbytes = req->cryptlen;
0605c41c HX	245	unsigned int offset;
	246	u8 *space;
	247
	248	skcipher_request_set_tfm(subreq, ctx->child);
	249
c31a8719 EB	250	if (nbytes < bsize)
	251	return -EINVAL;
	252
	253	if (nbytes == bsize) {
0605c41c HX	254	skcipher_request_set_callback(subreq, req->base.flags,
	255	req->base.complete,
	256	req->base.data);
	257	skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
	258	req->iv);
	259	return crypto_skcipher_decrypt(subreq);
	260	}
7185ad26	261
0605c41c HX	262	skcipher_request_set_callback(subreq, req->base.flags,
0605c41c HX	263	crypto_cts_decrypt_done, req);
76cb9521	264
0605c41c	265	space = crypto_cts_reqctx_space(req);
76cb9521	266
c31a8719	267	offset = rounddown(nbytes - 1, bsize);
0605c41c	268	rctx->offset = offset;
76cb9521	269
c31a8719	270	if (offset <= bsize)
0605c41c HX	271	memcpy(space, req->iv, bsize);
	272	else
	273	scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
	274	bsize, 0);
76cb9521	275
0605c41c HX	276	skcipher_request_set_crypt(subreq, req->src, req->dst,
0605c41c HX	277	offset, req->iv);
76cb9521	278
0605c41c HX	279	return crypto_skcipher_decrypt(subreq) ?:
0605c41c HX	280	cts_cbc_decrypt(req);
76cb9521 KC	281	}
76cb9521 KC	282
0605c41c	283	static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
76cb9521	284	{
0605c41c HX	285	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	286	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
	287	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	288	struct crypto_skcipher *cipher;
	289	unsigned reqsize;
	290	unsigned bsize;
	291	unsigned align;
	292
60425a8b	293	cipher = crypto_spawn_skcipher(spawn);
76cb9521 KC	294	if (IS_ERR(cipher))
	295	return PTR_ERR(cipher);
	296
	297	ctx->child = cipher;
0605c41c HX	298
	299	align = crypto_skcipher_alignmask(tfm);
	300	bsize = crypto_skcipher_blocksize(cipher);
	301	reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
	302	crypto_skcipher_reqsize(cipher),
	303	crypto_tfm_ctx_alignment()) +
	304	(align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
	305
	306	crypto_skcipher_set_reqsize(tfm, reqsize);
	307
76cb9521 KC	308	return 0;
	309	}
	310
0605c41c	311	static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
76cb9521	312	{
0605c41c HX	313	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	314
	315	crypto_free_skcipher(ctx->child);
76cb9521 KC	316	}
76cb9521 KC	317
0605c41c	318	static void crypto_cts_free(struct skcipher_instance *inst)
76cb9521	319	{
0605c41c HX	320	crypto_drop_skcipher(skcipher_instance_ctx(inst));
	321	kfree(inst);
	322	}
	323
	324	static int crypto_cts_create(struct crypto_template tmpl, struct rtattr *tb)
	325	{
	326	struct crypto_skcipher_spawn *spawn;
	327	struct skcipher_instance *inst;
0605c41c	328	struct skcipher_alg *alg;
b9f76ddd	329	u32 mask;
76cb9521 KC	330	int err;
76cb9521 KC	331
7bcb2c99 EB	332	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
	333	if (err)
	334	return err;
b9f76ddd	335
0605c41c HX	336	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
	337	if (!inst)
	338	return -ENOMEM;
	339
	340	spawn = skcipher_instance_ctx(inst);
	341
b9f76ddd	342	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
3ff2bab8	343	crypto_attr_alg_name(tb[1]), 0, mask);
76cb9521	344	if (err)
0605c41c	345	goto err_free_inst;
76cb9521	346
0605c41c	347	alg = crypto_spawn_skcipher_alg(spawn);
76cb9521	348
0605c41c HX	349	err = -EINVAL;
0605c41c HX	350	if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
3ff2bab8	351	goto err_free_inst;
76cb9521	352
0605c41c	353	if (strncmp(alg->base.cra_name, "cbc(", 4))
3ff2bab8	354	goto err_free_inst;
988dc017	355
0605c41c HX	356	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
	357	&alg->base);
	358	if (err)
3ff2bab8	359	goto err_free_inst;
76cb9521	360
0605c41c HX	361	inst->alg.base.cra_priority = alg->base.cra_priority;
	362	inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
	363	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
76cb9521	364
0605c41c HX	365	inst->alg.ivsize = alg->base.cra_blocksize;
	366	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
	367	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
	368	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
76cb9521	369
0605c41c	370	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
76cb9521	371
0605c41c HX	372	inst->alg.init = crypto_cts_init_tfm;
0605c41c HX	373	inst->alg.exit = crypto_cts_exit_tfm;
76cb9521	374
0605c41c HX	375	inst->alg.setkey = crypto_cts_setkey;
	376	inst->alg.encrypt = crypto_cts_encrypt;
	377	inst->alg.decrypt = crypto_cts_decrypt;
76cb9521	378
0605c41c	379	inst->free = crypto_cts_free;
76cb9521	380
0605c41c	381	err = skcipher_register_instance(tmpl, inst);
3ff2bab8	382	if (err) {
0605c41c	383	err_free_inst:
3ff2bab8 EB	384	crypto_cts_free(inst);
	385	}
	386	return err;
76cb9521 KC	387	}
	388
	389	static struct crypto_template crypto_cts_tmpl = {
	390	.name = "cts",
0605c41c	391	.create = crypto_cts_create,
76cb9521 KC	392	.module = THIS_MODULE,
	393	};
	394
	395	static int __init crypto_cts_module_init(void)
	396	{
	397	return crypto_register_template(&crypto_cts_tmpl);
	398	}
	399
	400	static void __exit crypto_cts_module_exit(void)
	401	{
	402	crypto_unregister_template(&crypto_cts_tmpl);
	403	}
	404
c4741b23	405	subsys_initcall(crypto_cts_module_init);
76cb9521 KC	406	module_exit(crypto_cts_module_exit);
	407
	408	MODULE_LICENSE("Dual BSD/GPL");
	409	MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
4943ba16	410	MODULE_ALIAS_CRYPTO("cts");