[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;
	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[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 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);
}

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 KC	81	int err;
76cb9521 KC	82
0605c41c HX	83	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	84	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
	85	CRYPTO_TFM_REQ_MASK);
	86	err = crypto_skcipher_setkey(child, key, keylen);
	87	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
	88	CRYPTO_TFM_RES_MASK);
	89	return err;
	90	}
76cb9521	91
0605c41c HX	92	static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
	93	{
	94	struct skcipher_request *req = areq->data;
c4913c7b	95
0605c41c HX	96	if (err == -EINPROGRESS)
0605c41c HX	97	return;
76cb9521	98
0605c41c HX	99	skcipher_request_complete(req, err);
0605c41c HX	100	}
76cb9521	101
0605c41c HX	102	static int cts_cbc_encrypt(struct skcipher_request *req)
	103	{
	104	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	105	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	106	struct skcipher_request *subreq = &rctx->subreq;
	107	int bsize = crypto_skcipher_blocksize(tfm);
6650c4de	108	u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));
0605c41c HX	109	struct scatterlist *sg;
	110	unsigned int offset;
	111	int lastn;
	112
	113	offset = rctx->offset;
	114	lastn = req->cryptlen - offset;
	115
	116	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	117	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	118
	119	memset(d, 0, bsize);
	120	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	121
	122	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
	123	memzero_explicit(d, sizeof(d));
	124
	125	skcipher_request_set_callback(subreq, req->base.flags &
	126	CRYPTO_TFM_REQ_MAY_BACKLOG,
	127	cts_cbc_crypt_done, req);
	128	skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
	129	return crypto_skcipher_encrypt(subreq);
	130	}
76cb9521	131
0605c41c HX	132	static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
	133	{
	134	struct skcipher_request *req = areq->data;
76cb9521	135
0605c41c HX	136	if (err)
0605c41c HX	137	goto out;
76cb9521	138
0605c41c	139	err = cts_cbc_encrypt(req);
4e5b0ad5	140	if (err == -EINPROGRESS \|\| err == -EBUSY)
0605c41c	141	return;
76cb9521	142
0605c41c HX	143	out:
	144	skcipher_request_complete(req, err);
	145	}
76cb9521	146
0605c41c HX	147	static int crypto_cts_encrypt(struct skcipher_request *req)
	148	{
	149	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	150	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	151	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	152	struct skcipher_request *subreq = &rctx->subreq;
	153	int bsize = crypto_skcipher_blocksize(tfm);
	154	unsigned int nbytes = req->cryptlen;
0605c41c HX	155	unsigned int offset;
	156
	157	skcipher_request_set_tfm(subreq, ctx->child);
	158
c31a8719 EB	159	if (nbytes < bsize)
	160	return -EINVAL;
	161
	162	if (nbytes == bsize) {
0605c41c HX	163	skcipher_request_set_callback(subreq, req->base.flags,
	164	req->base.complete,
	165	req->base.data);
	166	skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
	167	req->iv);
	168	return crypto_skcipher_encrypt(subreq);
	169	}
76cb9521	170
c31a8719	171	offset = rounddown(nbytes - 1, bsize);
0605c41c	172	rctx->offset = offset;
76cb9521	173
0605c41c HX	174	skcipher_request_set_callback(subreq, req->base.flags,
	175	crypto_cts_encrypt_done, req);
	176	skcipher_request_set_crypt(subreq, req->src, req->dst,
	177	offset, req->iv);
76cb9521	178
0605c41c HX	179	return crypto_skcipher_encrypt(subreq) ?:
0605c41c HX	180	cts_cbc_encrypt(req);
76cb9521 KC	181	}
76cb9521 KC	182
0605c41c	183	static int cts_cbc_decrypt(struct skcipher_request *req)
76cb9521	184	{
0605c41c HX	185	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	186	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	187	struct skcipher_request *subreq = &rctx->subreq;
	188	int bsize = crypto_skcipher_blocksize(tfm);
6650c4de	189	u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));
0605c41c HX	190	struct scatterlist *sg;
	191	unsigned int offset;
	192	u8 *space;
	193	int lastn;
	194
	195	offset = rctx->offset;
	196	lastn = req->cryptlen - offset;
	197
	198	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	199
	200	/* 1. Decrypt Cn-1 (s) to create Dn */
	201	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	202	space = crypto_cts_reqctx_space(req);
	203	crypto_xor(d + bsize, space, bsize);
	204	/* 2. Pad Cn with zeros at the end to create C of length BB */
	205	memset(d, 0, bsize);
	206	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	207	/* 3. Exclusive-or Dn with C to create Xn */
	208	/* 4. Select the first Ln bytes of Xn to create Pn */
	209	crypto_xor(d + bsize, d, lastn);
	210
	211	/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
	212	memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
	213	/* 6. Decrypt En to create Pn-1 */
76cb9521	214
0605c41c HX	215	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
0605c41c HX	216	memzero_explicit(d, sizeof(d));
76cb9521	217
0605c41c HX	218	skcipher_request_set_callback(subreq, req->base.flags &
	219	CRYPTO_TFM_REQ_MAY_BACKLOG,
	220	cts_cbc_crypt_done, req);
	221
	222	skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
	223	return crypto_skcipher_decrypt(subreq);
76cb9521 KC	224	}
76cb9521 KC	225
0605c41c	226	static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
76cb9521	227	{
0605c41c	228	struct skcipher_request *req = areq->data;
76cb9521	229
0605c41c HX	230	if (err)
0605c41c HX	231	goto out;
c4913c7b	232
0605c41c	233	err = cts_cbc_decrypt(req);
4e5b0ad5	234	if (err == -EINPROGRESS \|\| err == -EBUSY)
0605c41c	235	return;
76cb9521	236
0605c41c HX	237	out:
	238	skcipher_request_complete(req, err);
	239	}
76cb9521	240
0605c41c HX	241	static int crypto_cts_decrypt(struct skcipher_request *req)
	242	{
	243	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	244	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	245	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	246	struct skcipher_request *subreq = &rctx->subreq;
	247	int bsize = crypto_skcipher_blocksize(tfm);
	248	unsigned int nbytes = req->cryptlen;
0605c41c HX	249	unsigned int offset;
	250	u8 *space;
	251
	252	skcipher_request_set_tfm(subreq, ctx->child);
	253
c31a8719 EB	254	if (nbytes < bsize)
	255	return -EINVAL;
	256
	257	if (nbytes == bsize) {
0605c41c HX	258	skcipher_request_set_callback(subreq, req->base.flags,
	259	req->base.complete,
	260	req->base.data);
	261	skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
	262	req->iv);
	263	return crypto_skcipher_decrypt(subreq);
	264	}
7185ad26	265
0605c41c HX	266	skcipher_request_set_callback(subreq, req->base.flags,
0605c41c HX	267	crypto_cts_decrypt_done, req);
76cb9521	268
0605c41c	269	space = crypto_cts_reqctx_space(req);
76cb9521	270
c31a8719	271	offset = rounddown(nbytes - 1, bsize);
0605c41c	272	rctx->offset = offset;
76cb9521	273
c31a8719	274	if (offset <= bsize)
0605c41c HX	275	memcpy(space, req->iv, bsize);
	276	else
	277	scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
	278	bsize, 0);
76cb9521	279
0605c41c HX	280	skcipher_request_set_crypt(subreq, req->src, req->dst,
0605c41c HX	281	offset, req->iv);
76cb9521	282
0605c41c HX	283	return crypto_skcipher_decrypt(subreq) ?:
0605c41c HX	284	cts_cbc_decrypt(req);
76cb9521 KC	285	}
76cb9521 KC	286
0605c41c	287	static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
76cb9521	288	{
0605c41c HX	289	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	290	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
	291	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	292	struct crypto_skcipher *cipher;
	293	unsigned reqsize;
	294	unsigned bsize;
	295	unsigned align;
	296
60425a8b	297	cipher = crypto_spawn_skcipher(spawn);
76cb9521 KC	298	if (IS_ERR(cipher))
	299	return PTR_ERR(cipher);
	300
	301	ctx->child = cipher;
0605c41c HX	302
	303	align = crypto_skcipher_alignmask(tfm);
	304	bsize = crypto_skcipher_blocksize(cipher);
	305	reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
	306	crypto_skcipher_reqsize(cipher),
	307	crypto_tfm_ctx_alignment()) +
	308	(align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
	309
	310	crypto_skcipher_set_reqsize(tfm, reqsize);
	311
76cb9521 KC	312	return 0;
	313	}
	314
0605c41c	315	static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
76cb9521	316	{
0605c41c HX	317	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	318
	319	crypto_free_skcipher(ctx->child);
76cb9521 KC	320	}
76cb9521 KC	321
0605c41c	322	static void crypto_cts_free(struct skcipher_instance *inst)
76cb9521	323	{
0605c41c HX	324	crypto_drop_skcipher(skcipher_instance_ctx(inst));
	325	kfree(inst);
	326	}
	327
	328	static int crypto_cts_create(struct crypto_template tmpl, struct rtattr *tb)
	329	{
	330	struct crypto_skcipher_spawn *spawn;
	331	struct skcipher_instance *inst;
	332	struct crypto_attr_type *algt;
	333	struct skcipher_alg *alg;
	334	const char *cipher_name;
76cb9521 KC	335	int err;
76cb9521 KC	336
0605c41c HX	337	algt = crypto_get_attr_type(tb);
	338	if (IS_ERR(algt))
	339	return PTR_ERR(algt);
	340
	341	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
	342	return -EINVAL;
	343
	344	cipher_name = crypto_attr_alg_name(tb[1]);
	345	if (IS_ERR(cipher_name))
	346	return PTR_ERR(cipher_name);
	347
	348	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
	349	if (!inst)
	350	return -ENOMEM;
	351
	352	spawn = skcipher_instance_ctx(inst);
	353
	354	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
a35528ec EB	355	err = crypto_grab_skcipher(spawn, cipher_name, 0,
	356	crypto_requires_sync(algt->type,
	357	algt->mask));
76cb9521	358	if (err)
0605c41c	359	goto err_free_inst;
76cb9521	360
0605c41c	361	alg = crypto_spawn_skcipher_alg(spawn);
76cb9521	362
0605c41c HX	363	err = -EINVAL;
	364	if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
	365	goto err_drop_spawn;
76cb9521	366
0605c41c HX	367	if (strncmp(alg->base.cra_name, "cbc(", 4))
0605c41c HX	368	goto err_drop_spawn;
988dc017	369
0605c41c HX	370	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
	371	&alg->base);
	372	if (err)
	373	goto err_drop_spawn;
76cb9521	374
0605c41c HX	375	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
	376	inst->alg.base.cra_priority = alg->base.cra_priority;
	377	inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
	378	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
76cb9521	379
0605c41c HX	380	inst->alg.ivsize = alg->base.cra_blocksize;
	381	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
	382	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
	383	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
76cb9521	384
0605c41c	385	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
76cb9521	386
0605c41c HX	387	inst->alg.init = crypto_cts_init_tfm;
0605c41c HX	388	inst->alg.exit = crypto_cts_exit_tfm;
76cb9521	389
0605c41c HX	390	inst->alg.setkey = crypto_cts_setkey;
	391	inst->alg.encrypt = crypto_cts_encrypt;
	392	inst->alg.decrypt = crypto_cts_decrypt;
76cb9521	393
0605c41c	394	inst->free = crypto_cts_free;
76cb9521	395
0605c41c HX	396	err = skcipher_register_instance(tmpl, inst);
	397	if (err)
	398	goto err_drop_spawn;
	399
	400	out:
	401	return err;
	402
	403	err_drop_spawn:
	404	crypto_drop_skcipher(spawn);
	405	err_free_inst:
76cb9521	406	kfree(inst);
0605c41c	407	goto out;
76cb9521 KC	408	}
	409
	410	static struct crypto_template crypto_cts_tmpl = {
	411	.name = "cts",
0605c41c	412	.create = crypto_cts_create,
76cb9521 KC	413	.module = THIS_MODULE,
	414	};
	415
	416	static int __init crypto_cts_module_init(void)
	417	{
	418	return crypto_register_template(&crypto_cts_tmpl);
	419	}
	420
	421	static void __exit crypto_cts_module_exit(void)
	422	{
	423	crypto_unregister_template(&crypto_cts_tmpl);
	424	}
	425
c4741b23	426	subsys_initcall(crypto_cts_module_init);
76cb9521 KC	427	module_exit(crypto_cts_module_exit);
	428
	429	MODULE_LICENSE("Dual BSD/GPL");
	430	MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
4943ba16	431	MODULE_ALIAS_CRYPTO("cts");