[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/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>

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] __attribute__ ((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] __attribute__ ((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_skcipher2(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_skcipher2(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;

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

	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");
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
0605c41c	43	#include <crypto/internal/skcipher.h>
76cb9521 KC	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 {
0605c41c	54	struct crypto_skcipher *child;
76cb9521 KC	55	};
76cb9521 KC	56
0605c41c HX	57	struct crypto_cts_reqctx {
	58	struct scatterlist sg[2];
	59	unsigned offset;
	60	struct skcipher_request subreq;
	61	};
	62
	63	static inline u8 crypto_cts_reqctx_space(struct skcipher_request req)
76cb9521	64	{
0605c41c HX	65	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	66	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	67	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	68	struct crypto_skcipher *child = ctx->child;
76cb9521	69
0605c41c HX	70	return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
0605c41c HX	71	crypto_skcipher_alignmask(tfm) + 1);
76cb9521 KC	72	}
76cb9521 KC	73
0605c41c HX	74	static int crypto_cts_setkey(struct crypto_skcipher parent, const u8 key,
0605c41c HX	75	unsigned int keylen)
76cb9521	76	{
0605c41c HX	77	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
0605c41c HX	78	struct crypto_skcipher *child = ctx->child;
76cb9521 KC	79	int err;
76cb9521 KC	80
0605c41c HX	81	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	82	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
	83	CRYPTO_TFM_REQ_MASK);
	84	err = crypto_skcipher_setkey(child, key, keylen);
	85	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
	86	CRYPTO_TFM_RES_MASK);
	87	return err;
	88	}
76cb9521	89
0605c41c HX	90	static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
	91	{
	92	struct skcipher_request *req = areq->data;
c4913c7b	93
0605c41c HX	94	if (err == -EINPROGRESS)
0605c41c HX	95	return;
76cb9521	96
0605c41c HX	97	skcipher_request_complete(req, err);
0605c41c HX	98	}
76cb9521	99
0605c41c HX	100	static int cts_cbc_encrypt(struct skcipher_request *req)
	101	{
	102	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	103	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	104	struct skcipher_request *subreq = &rctx->subreq;
	105	int bsize = crypto_skcipher_blocksize(tfm);
	106	u8 d[bsize * 2] __attribute__ ((aligned(__alignof__(u32))));
	107	struct scatterlist *sg;
	108	unsigned int offset;
	109	int lastn;
	110
	111	offset = rctx->offset;
	112	lastn = req->cryptlen - offset;
	113
	114	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	115	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	116
	117	memset(d, 0, bsize);
	118	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	119
	120	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
	121	memzero_explicit(d, sizeof(d));
	122
	123	skcipher_request_set_callback(subreq, req->base.flags &
	124	CRYPTO_TFM_REQ_MAY_BACKLOG,
	125	cts_cbc_crypt_done, req);
	126	skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
	127	return crypto_skcipher_encrypt(subreq);
	128	}
76cb9521	129
0605c41c HX	130	static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
	131	{
	132	struct skcipher_request *req = areq->data;
76cb9521	133
0605c41c HX	134	if (err)
0605c41c HX	135	goto out;
76cb9521	136
0605c41c HX	137	err = cts_cbc_encrypt(req);
	138	if (err == -EINPROGRESS \|\|
	139	(err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
	140	return;
76cb9521	141
0605c41c HX	142	out:
	143	skcipher_request_complete(req, err);
	144	}
76cb9521	145
0605c41c HX	146	static int crypto_cts_encrypt(struct skcipher_request *req)
	147	{
	148	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	149	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	150	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	151	struct skcipher_request *subreq = &rctx->subreq;
	152	int bsize = crypto_skcipher_blocksize(tfm);
	153	unsigned int nbytes = req->cryptlen;
	154	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
	155	unsigned int offset;
	156
	157	skcipher_request_set_tfm(subreq, ctx->child);
	158
	159	if (cbc_blocks <= 0) {
	160	skcipher_request_set_callback(subreq, req->base.flags,
	161	req->base.complete,
	162	req->base.data);
	163	skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
	164	req->iv);
	165	return crypto_skcipher_encrypt(subreq);
	166	}
76cb9521	167
0605c41c HX	168	offset = cbc_blocks * bsize;
0605c41c HX	169	rctx->offset = offset;
76cb9521	170
0605c41c HX	171	skcipher_request_set_callback(subreq, req->base.flags,
	172	crypto_cts_encrypt_done, req);
	173	skcipher_request_set_crypt(subreq, req->src, req->dst,
	174	offset, req->iv);
76cb9521	175
0605c41c HX	176	return crypto_skcipher_encrypt(subreq) ?:
0605c41c HX	177	cts_cbc_encrypt(req);
76cb9521 KC	178	}
76cb9521 KC	179
0605c41c	180	static int cts_cbc_decrypt(struct skcipher_request *req)
76cb9521	181	{
0605c41c HX	182	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	183	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	184	struct skcipher_request *subreq = &rctx->subreq;
	185	int bsize = crypto_skcipher_blocksize(tfm);
	186	u8 d[bsize * 2] __attribute__ ((aligned(__alignof__(u32))));
	187	struct scatterlist *sg;
	188	unsigned int offset;
	189	u8 *space;
	190	int lastn;
	191
	192	offset = rctx->offset;
	193	lastn = req->cryptlen - offset;
	194
	195	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	196
	197	/* 1. Decrypt Cn-1 (s) to create Dn */
	198	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	199	space = crypto_cts_reqctx_space(req);
	200	crypto_xor(d + bsize, space, bsize);
	201	/* 2. Pad Cn with zeros at the end to create C of length BB */
	202	memset(d, 0, bsize);
	203	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	204	/* 3. Exclusive-or Dn with C to create Xn */
	205	/* 4. Select the first Ln bytes of Xn to create Pn */
	206	crypto_xor(d + bsize, d, lastn);
	207
	208	/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
	209	memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
	210	/* 6. Decrypt En to create Pn-1 */
76cb9521	211
0605c41c HX	212	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
0605c41c HX	213	memzero_explicit(d, sizeof(d));
76cb9521	214
0605c41c HX	215	skcipher_request_set_callback(subreq, req->base.flags &
	216	CRYPTO_TFM_REQ_MAY_BACKLOG,
	217	cts_cbc_crypt_done, req);
	218
	219	skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
	220	return crypto_skcipher_decrypt(subreq);
76cb9521 KC	221	}
76cb9521 KC	222
0605c41c	223	static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
76cb9521	224	{
0605c41c	225	struct skcipher_request *req = areq->data;
76cb9521	226
0605c41c HX	227	if (err)
0605c41c HX	228	goto out;
c4913c7b	229
0605c41c HX	230	err = cts_cbc_decrypt(req);
	231	if (err == -EINPROGRESS \|\|
	232	(err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
	233	return;
76cb9521	234
0605c41c HX	235	out:
	236	skcipher_request_complete(req, err);
	237	}
76cb9521	238
0605c41c HX	239	static int crypto_cts_decrypt(struct skcipher_request *req)
	240	{
	241	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	242	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	243	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	244	struct skcipher_request *subreq = &rctx->subreq;
	245	int bsize = crypto_skcipher_blocksize(tfm);
	246	unsigned int nbytes = req->cryptlen;
	247	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
	248	unsigned int offset;
	249	u8 *space;
	250
	251	skcipher_request_set_tfm(subreq, ctx->child);
	252
	253	if (cbc_blocks <= 0) {
	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
0605c41c HX	267	offset = cbc_blocks * bsize;
0605c41c HX	268	rctx->offset = offset;
76cb9521	269
0605c41c HX	270	if (cbc_blocks <= 1)
	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
	293	cipher = crypto_spawn_skcipher2(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;
	328	struct crypto_attr_type *algt;
	329	struct skcipher_alg *alg;
	330	const char *cipher_name;
76cb9521 KC	331	int err;
76cb9521 KC	332
0605c41c HX	333	algt = crypto_get_attr_type(tb);
	334	if (IS_ERR(algt))
	335	return PTR_ERR(algt);
	336
	337	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
	338	return -EINVAL;
	339
	340	cipher_name = crypto_attr_alg_name(tb[1]);
	341	if (IS_ERR(cipher_name))
	342	return PTR_ERR(cipher_name);
	343
	344	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
	345	if (!inst)
	346	return -ENOMEM;
	347
	348	spawn = skcipher_instance_ctx(inst);
	349
	350	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
	351	err = crypto_grab_skcipher2(spawn, cipher_name, 0,
	352	crypto_requires_sync(algt->type,
	353	algt->mask));
76cb9521	354	if (err)
0605c41c	355	goto err_free_inst;
76cb9521	356
0605c41c	357	alg = crypto_spawn_skcipher_alg(spawn);
76cb9521	358
0605c41c HX	359	err = -EINVAL;
	360	if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
	361	goto err_drop_spawn;
76cb9521	362
0605c41c HX	363	if (strncmp(alg->base.cra_name, "cbc(", 4))
0605c41c HX	364	goto err_drop_spawn;
988dc017	365
0605c41c HX	366	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
	367	&alg->base);
	368	if (err)
	369	goto err_drop_spawn;
76cb9521	370
0605c41c HX	371	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
	372	inst->alg.base.cra_priority = alg->base.cra_priority;
	373	inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
	374	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
76cb9521 KC	375
76cb9521 KC	376	/* We access the data as u32s when xoring. */
0605c41c	377	inst->alg.base.cra_alignmask \|= __alignof__(u32) - 1;
76cb9521	378
0605c41c HX	379	inst->alg.ivsize = alg->base.cra_blocksize;
	380	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
	381	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
	382	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
76cb9521	383
0605c41c	384	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
76cb9521	385
0605c41c HX	386	inst->alg.init = crypto_cts_init_tfm;
0605c41c HX	387	inst->alg.exit = crypto_cts_exit_tfm;
76cb9521	388
0605c41c HX	389	inst->alg.setkey = crypto_cts_setkey;
	390	inst->alg.encrypt = crypto_cts_encrypt;
	391	inst->alg.decrypt = crypto_cts_decrypt;
76cb9521	392
0605c41c	393	inst->free = crypto_cts_free;
76cb9521	394
0605c41c HX	395	err = skcipher_register_instance(tmpl, inst);
	396	if (err)
	397	goto err_drop_spawn;
	398
	399	out:
	400	return err;
	401
	402	err_drop_spawn:
	403	crypto_drop_skcipher(spawn);
	404	err_free_inst:
76cb9521	405	kfree(inst);
0605c41c	406	goto out;
76cb9521 KC	407	}
	408
	409	static struct crypto_template crypto_cts_tmpl = {
	410	.name = "cts",
0605c41c	411	.create = crypto_cts_create,
76cb9521 KC	412	.module = THIS_MODULE,
	413	};
	414
	415	static int __init crypto_cts_module_init(void)
	416	{
	417	return crypto_register_template(&crypto_cts_tmpl);
	418	}
	419
	420	static void __exit crypto_cts_module_exit(void)
	421	{
	422	crypto_unregister_template(&crypto_cts_tmpl);
	423	}
	424
	425	module_init(crypto_cts_module_init);
	426	module_exit(crypto_cts_module_exit);
	427
	428	MODULE_LICENSE("Dual BSD/GPL");
	429	MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
4943ba16	430	MODULE_ALIAS_CRYPTO("cts");