[deliverable/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 <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/algapi.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>

struct crypto_cts_ctx {
	struct crypto_blkcipher *child;
};

static int crypto_cts_setkey(struct crypto_tfm *parent, const u8 *key,
			     unsigned int keylen)
{
	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(parent);
	struct crypto_blkcipher *child = ctx->child;
	int err;

	crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
				       CRYPTO_TFM_REQ_MASK);
	err = crypto_blkcipher_setkey(child, key, keylen);
	crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
				     CRYPTO_TFM_RES_MASK);
	return err;
}

static int cts_cbc_encrypt(struct crypto_cts_ctx *ctx,
			   struct blkcipher_desc *desc,
			   struct scatterlist *dst,
			   struct scatterlist *src,
			   unsigned int offset,
			   unsigned int nbytes)
{
	int bsize = crypto_blkcipher_blocksize(desc->tfm);
	u8 tmp[bsize], tmp2[bsize];
	struct blkcipher_desc lcldesc;
	struct scatterlist sgsrc[1], sgdst[1];
	int lastn = nbytes - bsize;
	u8 iv[bsize];
	u8 s[bsize * 2], d[bsize * 2];
	int err;

	if (lastn < 0)
		return -EINVAL;

	sg_init_table(sgsrc, 1);
	sg_init_table(sgdst, 1);

	memset(s, 0, sizeof(s));
	scatterwalk_map_and_copy(s, src, offset, nbytes, 0);

	memcpy(iv, desc->info, bsize);

	lcldesc.tfm = ctx->child;
	lcldesc.info = iv;
	lcldesc.flags = desc->flags;

	sg_set_buf(&sgsrc[0], s, bsize);
	sg_set_buf(&sgdst[0], tmp, bsize);
	err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);

	memcpy(d + bsize, tmp, lastn);

	lcldesc.info = tmp;

	sg_set_buf(&sgsrc[0], s + bsize, bsize);
	sg_set_buf(&sgdst[0], tmp2, bsize);
	err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);

	memcpy(d, tmp2, bsize);

	scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);

	memcpy(desc->info, tmp2, bsize);

	return err;
}

static int crypto_cts_encrypt(struct blkcipher_desc *desc,
			      struct scatterlist *dst, struct scatterlist *src,
			      unsigned int nbytes)
{
	struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	int bsize = crypto_blkcipher_blocksize(desc->tfm);
	int tot_blocks = (nbytes + bsize - 1) / bsize;
	int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
	struct blkcipher_desc lcldesc;
	int err;

	lcldesc.tfm = ctx->child;
	lcldesc.info = desc->info;
	lcldesc.flags = desc->flags;

	if (tot_blocks == 1) {
		err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src, bsize);
	} else if (nbytes <= bsize * 2) {
		err = cts_cbc_encrypt(ctx, desc, dst, src, 0, nbytes);
	} else {
		/* do normal function for tot_blocks - 2 */
		err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src,
							cbc_blocks * bsize);
		if (err == 0) {
			/* do cts for final two blocks */
			err = cts_cbc_encrypt(ctx, desc, dst, src,
						cbc_blocks * bsize,
						nbytes - (cbc_blocks * bsize));
		}
	}

	return err;
}

static int cts_cbc_decrypt(struct crypto_cts_ctx *ctx,
			   struct blkcipher_desc *desc,
			   struct scatterlist *dst,
			   struct scatterlist *src,
			   unsigned int offset,
			   unsigned int nbytes)
{
	int bsize = crypto_blkcipher_blocksize(desc->tfm);
	u8 tmp[bsize];
	struct blkcipher_desc lcldesc;
	struct scatterlist sgsrc[1], sgdst[1];
	int lastn = nbytes - bsize;
	u8 iv[bsize];
	u8 s[bsize * 2], d[bsize * 2];
	int err;

	if (lastn < 0)
		return -EINVAL;

	sg_init_table(sgsrc, 1);
	sg_init_table(sgdst, 1);

	scatterwalk_map_and_copy(s, src, offset, nbytes, 0);

	lcldesc.tfm = ctx->child;
	lcldesc.info = iv;
	lcldesc.flags = desc->flags;

	/* 1. Decrypt Cn-1 (s) to create Dn (tmp)*/
	memset(iv, 0, sizeof(iv));
	sg_set_buf(&sgsrc[0], s, bsize);
	sg_set_buf(&sgdst[0], tmp, bsize);
	err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
	if (err)
		return err;
	/* 2. Pad Cn with zeros at the end to create C of length BB */
	memset(iv, 0, sizeof(iv));
	memcpy(iv, s + bsize, lastn);
	/* 3. Exclusive-or Dn (tmp) with C (iv) to create Xn (tmp) */
	crypto_xor(tmp, iv, bsize);
	/* 4. Select the first Ln bytes of Xn (tmp) to create Pn */
	memcpy(d + bsize, tmp, lastn);

	/* 5. Append the tail (BB - Ln) bytes of Xn (tmp) to Cn to create En */
	memcpy(s + bsize + lastn, tmp + lastn, bsize - lastn);
	/* 6. Decrypt En to create Pn-1 */
	memset(iv, 0, sizeof(iv));
	sg_set_buf(&sgsrc[0], s + bsize, bsize);
	sg_set_buf(&sgdst[0], d, bsize);
	err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);

	/* XOR with previous block */
	crypto_xor(d, desc->info, bsize);

	scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);

	memcpy(desc->info, s, bsize);
	return err;
}

static int crypto_cts_decrypt(struct blkcipher_desc *desc,
			      struct scatterlist *dst, struct scatterlist *src,
			      unsigned int nbytes)
{
	struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	int bsize = crypto_blkcipher_blocksize(desc->tfm);
	int tot_blocks = (nbytes + bsize - 1) / bsize;
	int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
	struct blkcipher_desc lcldesc;
	int err;

	lcldesc.tfm = ctx->child;
	lcldesc.info = desc->info;
	lcldesc.flags = desc->flags;

	if (tot_blocks == 1) {
		err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src, bsize);
	} else if (nbytes <= bsize * 2) {
		err = cts_cbc_decrypt(ctx, desc, dst, src, 0, nbytes);
	} else {
		/* do normal function for tot_blocks - 2 */
		err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src,
							cbc_blocks * bsize);
		if (err == 0) {
			/* do cts for final two blocks */
			err = cts_cbc_decrypt(ctx, desc, dst, src,
						cbc_blocks * bsize,
						nbytes - (cbc_blocks * bsize));
		}
	}
	return err;
}

static int crypto_cts_init_tfm(struct crypto_tfm *tfm)
{
	struct crypto_instance *inst = (void *)tfm->__crt_alg;
	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
	struct crypto_blkcipher *cipher;

	cipher = crypto_spawn_blkcipher(spawn);
	if (IS_ERR(cipher))
		return PTR_ERR(cipher);

	ctx->child = cipher;
	return 0;
}

static void crypto_cts_exit_tfm(struct crypto_tfm *tfm)
{
	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
	crypto_free_blkcipher(ctx->child);
}

static struct crypto_instance *crypto_cts_alloc(struct rtattr **tb)
{
	struct crypto_instance *inst;
	struct crypto_alg *alg;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
	if (err)
		return ERR_PTR(err);

	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
				  CRYPTO_ALG_TYPE_MASK);
	err = PTR_ERR(alg);
	if (IS_ERR(alg))
		return ERR_PTR(err);

	inst = ERR_PTR(-EINVAL);
	if (!is_power_of_2(alg->cra_blocksize))
		goto out_put_alg;

	inst = crypto_alloc_instance("cts", alg);
	if (IS_ERR(inst))
		goto out_put_alg;

	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
	inst->alg.cra_priority = alg->cra_priority;
	inst->alg.cra_blocksize = alg->cra_blocksize;
	inst->alg.cra_alignmask = alg->cra_alignmask;
	inst->alg.cra_type = &crypto_blkcipher_type;

	/* We access the data as u32s when xoring. */
	inst->alg.cra_alignmask |= __alignof__(u32) - 1;

	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
	inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
	inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize;

	inst->alg.cra_blkcipher.geniv = "seqiv";

	inst->alg.cra_ctxsize = sizeof(struct crypto_cts_ctx);

	inst->alg.cra_init = crypto_cts_init_tfm;
	inst->alg.cra_exit = crypto_cts_exit_tfm;

	inst->alg.cra_blkcipher.setkey = crypto_cts_setkey;
	inst->alg.cra_blkcipher.encrypt = crypto_cts_encrypt;
	inst->alg.cra_blkcipher.decrypt = crypto_cts_decrypt;

out_put_alg:
	crypto_mod_put(alg);
	return inst;
}

static void crypto_cts_free(struct crypto_instance *inst)
{
	crypto_drop_spawn(crypto_instance_ctx(inst));
	kfree(inst);
}

static struct crypto_template crypto_cts_tmpl = {
	.name = "cts",
	.alloc = crypto_cts_alloc,
	.free = crypto_cts_free,
	.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");
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 <herbert@gondor.apana.org.au>
	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
	43	#include <crypto/algapi.h>
	44	#include <linux/err.h>
	45	#include <linux/init.h>
	46	#include <linux/kernel.h>
	47	#include <linux/log2.h>
	48	#include <linux/module.h>
	49	#include <linux/scatterlist.h>
	50	#include <crypto/scatterwalk.h>
	51	#include <linux/slab.h>
	52
	53	struct crypto_cts_ctx {
	54	struct crypto_blkcipher *child;
	55	};
	56
	57	static int crypto_cts_setkey(struct crypto_tfm parent, const u8 key,
	58	unsigned int keylen)
	59	{
	60	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(parent);
	61	struct crypto_blkcipher *child = ctx->child;
	62	int err;
	63
	64	crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
65	crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
66	CRYPTO_TFM_REQ_MASK);
67	err = crypto_blkcipher_setkey(child, key, keylen);
68	crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
69	CRYPTO_TFM_RES_MASK);
70	return err;
71	}
72
73	static int cts_cbc_encrypt(struct crypto_cts_ctx *ctx,
74	struct blkcipher_desc *desc,
75	struct scatterlist *dst,
76	struct scatterlist *src,
77	unsigned int offset,
78	unsigned int nbytes)
79	{
80	int bsize = crypto_blkcipher_blocksize(desc->tfm);
81	u8 tmp[bsize], tmp2[bsize];
82	struct blkcipher_desc lcldesc;
83	struct scatterlist sgsrc[1], sgdst[1];
84	int lastn = nbytes - bsize;
85	u8 iv[bsize];
86	u8 s[bsize * 2], d[bsize * 2];
87	int err;
88
89	if (lastn < 0)
90	return -EINVAL;
91
c4913c7b AD	92	sg_init_table(sgsrc, 1);
	93	sg_init_table(sgdst, 1);
	94
76cb9521 KC	95	memset(s, 0, sizeof(s));
	96	scatterwalk_map_and_copy(s, src, offset, nbytes, 0);
	97
	98	memcpy(iv, desc->info, bsize);
	99
	100	lcldesc.tfm = ctx->child;
	101	lcldesc.info = iv;
	102	lcldesc.flags = desc->flags;
	103
	104	sg_set_buf(&sgsrc[0], s, bsize);
	105	sg_set_buf(&sgdst[0], tmp, bsize);
	106	err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
	107
	108	memcpy(d + bsize, tmp, lastn);
	109
	110	lcldesc.info = tmp;
	111
	112	sg_set_buf(&sgsrc[0], s + bsize, bsize);
	113	sg_set_buf(&sgdst[0], tmp2, bsize);
	114	err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
	115
	116	memcpy(d, tmp2, bsize);
	117
	118	scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);
	119
	120	memcpy(desc->info, tmp2, bsize);
	121
	122	return err;
	123	}
	124
	125	static int crypto_cts_encrypt(struct blkcipher_desc *desc,
	126	struct scatterlist dst, struct scatterlist src,
	127	unsigned int nbytes)
	128	{
	129	struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	130	int bsize = crypto_blkcipher_blocksize(desc->tfm);
	131	int tot_blocks = (nbytes + bsize - 1) / bsize;
	132	int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
	133	struct blkcipher_desc lcldesc;
	134	int err;
	135
	136	lcldesc.tfm = ctx->child;
	137	lcldesc.info = desc->info;
	138	lcldesc.flags = desc->flags;
	139
	140	if (tot_blocks == 1) {
	141	err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src, bsize);
	142	} else if (nbytes <= bsize * 2) {
	143	err = cts_cbc_encrypt(ctx, desc, dst, src, 0, nbytes);
	144	} else {
	145	/* do normal function for tot_blocks - 2 */
	146	err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src,
	147	cbc_blocks * bsize);
	148	if (err == 0) {
	149	/* do cts for final two blocks */
	150	err = cts_cbc_encrypt(ctx, desc, dst, src,
	151	cbc_blocks * bsize,
	152	nbytes - (cbc_blocks * bsize));
	153	}
	154	}
	155
	156	return err;
	157	}
	158
159	static int cts_cbc_decrypt(struct crypto_cts_ctx *ctx,
160	struct blkcipher_desc *desc,
161	struct scatterlist *dst,
162	struct scatterlist *src,
163	unsigned int offset,
164	unsigned int nbytes)
165	{
166	int bsize = crypto_blkcipher_blocksize(desc->tfm);
167	u8 tmp[bsize];
168	struct blkcipher_desc lcldesc;
169	struct scatterlist sgsrc[1], sgdst[1];
170	int lastn = nbytes - bsize;
171	u8 iv[bsize];
172	u8 s[bsize * 2], d[bsize * 2];
173	int err;
174
175	if (lastn < 0)
176	return -EINVAL;
177
c4913c7b AD	178	sg_init_table(sgsrc, 1);
	179	sg_init_table(sgdst, 1);
	180
76cb9521 KC	181	scatterwalk_map_and_copy(s, src, offset, nbytes, 0);
	182
	183	lcldesc.tfm = ctx->child;
	184	lcldesc.info = iv;
	185	lcldesc.flags = desc->flags;
	186
	187	/* 1. Decrypt Cn-1 (s) to create Dn (tmp)*/
	188	memset(iv, 0, sizeof(iv));
	189	sg_set_buf(&sgsrc[0], s, bsize);
	190	sg_set_buf(&sgdst[0], tmp, bsize);
	191	err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
	192	if (err)
	193	return err;
	194	/* 2. Pad Cn with zeros at the end to create C of length BB */
	195	memset(iv, 0, sizeof(iv));
	196	memcpy(iv, s + bsize, lastn);
	197	/* 3. Exclusive-or Dn (tmp) with C (iv) to create Xn (tmp) */
	198	crypto_xor(tmp, iv, bsize);
	199	/* 4. Select the first Ln bytes of Xn (tmp) to create Pn */
	200	memcpy(d + bsize, tmp, lastn);
	201
	202	/* 5. Append the tail (BB - Ln) bytes of Xn (tmp) to Cn to create En */
	203	memcpy(s + bsize + lastn, tmp + lastn, bsize - lastn);
	204	/* 6. Decrypt En to create Pn-1 */
	205	memset(iv, 0, sizeof(iv));
	206	sg_set_buf(&sgsrc[0], s + bsize, bsize);
	207	sg_set_buf(&sgdst[0], d, bsize);
	208	err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
	209
	210	/* XOR with previous block */
	211	crypto_xor(d, desc->info, bsize);
	212
	213	scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);
	214
	215	memcpy(desc->info, s, bsize);
	216	return err;
	217	}
	218
	219	static int crypto_cts_decrypt(struct blkcipher_desc *desc,
	220	struct scatterlist dst, struct scatterlist src,
	221	unsigned int nbytes)
	222	{
	223	struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
	224	int bsize = crypto_blkcipher_blocksize(desc->tfm);
	225	int tot_blocks = (nbytes + bsize - 1) / bsize;
	226	int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
	227	struct blkcipher_desc lcldesc;
	228	int err;
	229
	230	lcldesc.tfm = ctx->child;
	231	lcldesc.info = desc->info;
	232	lcldesc.flags = desc->flags;
	233
	234	if (tot_blocks == 1) {
	235	err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src, bsize);
	236	} else if (nbytes <= bsize * 2) {
	237	err = cts_cbc_decrypt(ctx, desc, dst, src, 0, nbytes);
	238	} else {
	239	/* do normal function for tot_blocks - 2 */
	240	err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src,
	241	cbc_blocks * bsize);
	242	if (err == 0) {
	243	/* do cts for final two blocks */
	244	err = cts_cbc_decrypt(ctx, desc, dst, src,
245	cbc_blocks * bsize,
246	nbytes - (cbc_blocks * bsize));
247	}
248	}
249	return err;
250	}
251
252	static int crypto_cts_init_tfm(struct crypto_tfm *tfm)
253	{
254	struct crypto_instance inst = (void )tfm->__crt_alg;
255	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
256	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
257	struct crypto_blkcipher *cipher;
258
259	cipher = crypto_spawn_blkcipher(spawn);
260	if (IS_ERR(cipher))
261	return PTR_ERR(cipher);
262
263	ctx->child = cipher;
264	return 0;
265	}
266
267	static void crypto_cts_exit_tfm(struct crypto_tfm *tfm)
268	{
269	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
270	crypto_free_blkcipher(ctx->child);
271	}
272
273	static struct crypto_instance crypto_cts_alloc(struct rtattr *tb)
274	{
275	struct crypto_instance *inst;
276	struct crypto_alg *alg;
277	int err;
278
279	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
280	if (err)
281	return ERR_PTR(err);
282
283	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
284	CRYPTO_ALG_TYPE_MASK);
285	err = PTR_ERR(alg);
286	if (IS_ERR(alg))
287	return ERR_PTR(err);
288
289	inst = ERR_PTR(-EINVAL);
290	if (!is_power_of_2(alg->cra_blocksize))
291	goto out_put_alg;
292
293	inst = crypto_alloc_instance("cts", alg);
294	if (IS_ERR(inst))
295	goto out_put_alg;
296
297	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
298	inst->alg.cra_priority = alg->cra_priority;
299	inst->alg.cra_blocksize = alg->cra_blocksize;
300	inst->alg.cra_alignmask = alg->cra_alignmask;
301	inst->alg.cra_type = &crypto_blkcipher_type;
302
303	/* We access the data as u32s when xoring. */
304	inst->alg.cra_alignmask \|= __alignof__(u32) - 1;
305
306	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
307	inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
308	inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize;
309
310	inst->alg.cra_blkcipher.geniv = "seqiv";
311
312	inst->alg.cra_ctxsize = sizeof(struct crypto_cts_ctx);
313
314	inst->alg.cra_init = crypto_cts_init_tfm;
315	inst->alg.cra_exit = crypto_cts_exit_tfm;
316
317	inst->alg.cra_blkcipher.setkey = crypto_cts_setkey;
318	inst->alg.cra_blkcipher.encrypt = crypto_cts_encrypt;
319	inst->alg.cra_blkcipher.decrypt = crypto_cts_decrypt;
320
321	out_put_alg:
322	crypto_mod_put(alg);
323	return inst;
324	}
325
326	static void crypto_cts_free(struct crypto_instance *inst)
327	{
328	crypto_drop_spawn(crypto_instance_ctx(inst));
329	kfree(inst);
330	}
331
332	static struct crypto_template crypto_cts_tmpl = {
333	.name = "cts",
334	.alloc = crypto_cts_alloc,
335	.free = crypto_cts_free,
336	.module = THIS_MODULE,
337	};
338
339	static int __init crypto_cts_module_init(void)
340	{
341	return crypto_register_template(&crypto_cts_tmpl);
342	}
343
344	static void __exit crypto_cts_module_exit(void)
345	{
346	crypto_unregister_template(&crypto_cts_tmpl);
347	}
348
349	module_init(crypto_cts_module_init);
350	module_exit(crypto_cts_module_exit);
351
352	MODULE_LICENSE("Dual BSD/GPL");
353	MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");