[mirror_ubuntu-bionic-kernel.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/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/log2.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <crypto/scatterwalk.h>
#include <linux/slab.h>
#include <linux/compiler.h>

struct crypto_cts_ctx {
	struct crypto_skcipher *child;
};

struct crypto_cts_reqctx {
	struct scatterlist sg[2];
	unsigned offset;
	struct skcipher_request subreq;
};

static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req)
{
	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *child = ctx->child;

	return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
			 crypto_skcipher_alignmask(tfm) + 1);
}

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

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

static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
{
	struct skcipher_request *req = areq->data;

	if (err == -EINPROGRESS)
		return;

	skcipher_request_complete(req, err);
}

static int cts_cbc_encrypt(struct skcipher_request *req)
{
	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct skcipher_request *subreq = &rctx->subreq;
	int bsize = crypto_skcipher_blocksize(tfm);
	u8 d[bsize * 2] __aligned(__alignof__(u32));
	struct scatterlist *sg;
	unsigned int offset;
	int lastn;

	offset = rctx->offset;
	lastn = req->cryptlen - offset;

	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);

	memset(d, 0, bsize);
	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);

	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
	memzero_explicit(d, sizeof(d));

	skcipher_request_set_callback(subreq, req->base.flags &
					      CRYPTO_TFM_REQ_MAY_BACKLOG,
				      cts_cbc_crypt_done, req);
	skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
	return crypto_skcipher_encrypt(subreq);
}

static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
{
	struct skcipher_request *req = areq->data;

	if (err)
		goto out;

	err = cts_cbc_encrypt(req);
	if (err == -EINPROGRESS || err == -EBUSY)
		return;

out:
	skcipher_request_complete(req, err);
}

static int crypto_cts_encrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct skcipher_request *subreq = &rctx->subreq;
	int bsize = crypto_skcipher_blocksize(tfm);
	unsigned int nbytes = req->cryptlen;
	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
	unsigned int offset;

	skcipher_request_set_tfm(subreq, ctx->child);

	if (cbc_blocks <= 0) {
		skcipher_request_set_callback(subreq, req->base.flags,
					      req->base.complete,
					      req->base.data);
		skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
					   req->iv);
		return crypto_skcipher_encrypt(subreq);
	}

	offset = cbc_blocks * bsize;
	rctx->offset = offset;

	skcipher_request_set_callback(subreq, req->base.flags,
				      crypto_cts_encrypt_done, req);
	skcipher_request_set_crypt(subreq, req->src, req->dst,
				   offset, req->iv);

	return crypto_skcipher_encrypt(subreq) ?:
	       cts_cbc_encrypt(req);
}

static int cts_cbc_decrypt(struct skcipher_request *req)
{
	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct skcipher_request *subreq = &rctx->subreq;
	int bsize = crypto_skcipher_blocksize(tfm);
	u8 d[bsize * 2] __aligned(__alignof__(u32));
	struct scatterlist *sg;
	unsigned int offset;
	u8 *space;
	int lastn;

	offset = rctx->offset;
	lastn = req->cryptlen - offset;

	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);

	/* 1. Decrypt Cn-1 (s) to create Dn */
	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	space = crypto_cts_reqctx_space(req);
	crypto_xor(d + bsize, space, bsize);
	/* 2. Pad Cn with zeros at the end to create C of length BB */
	memset(d, 0, bsize);
	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	/* 3. Exclusive-or Dn with C to create Xn */
	/* 4. Select the first Ln bytes of Xn to create Pn */
	crypto_xor(d + bsize, d, lastn);

	/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
	memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
	/* 6. Decrypt En to create Pn-1 */

	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
	memzero_explicit(d, sizeof(d));

	skcipher_request_set_callback(subreq, req->base.flags &
					      CRYPTO_TFM_REQ_MAY_BACKLOG,
				      cts_cbc_crypt_done, req);

	skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
	return crypto_skcipher_decrypt(subreq);
}

static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
{
	struct skcipher_request *req = areq->data;

	if (err)
		goto out;

	err = cts_cbc_decrypt(req);
	if (err == -EINPROGRESS || err == -EBUSY)
		return;

out:
	skcipher_request_complete(req, err);
}

static int crypto_cts_decrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct skcipher_request *subreq = &rctx->subreq;
	int bsize = crypto_skcipher_blocksize(tfm);
	unsigned int nbytes = req->cryptlen;
	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
	unsigned int offset;
	u8 *space;

	skcipher_request_set_tfm(subreq, ctx->child);

	if (cbc_blocks <= 0) {
		skcipher_request_set_callback(subreq, req->base.flags,
					      req->base.complete,
					      req->base.data);
		skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
					   req->iv);
		return crypto_skcipher_decrypt(subreq);
	}

	skcipher_request_set_callback(subreq, req->base.flags,
				      crypto_cts_decrypt_done, req);

	space = crypto_cts_reqctx_space(req);

	offset = cbc_blocks * bsize;
	rctx->offset = offset;

	if (cbc_blocks <= 1)
		memcpy(space, req->iv, bsize);
	else
		scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
					 bsize, 0);

	skcipher_request_set_crypt(subreq, req->src, req->dst,
				   offset, req->iv);

	return crypto_skcipher_decrypt(subreq) ?:
	       cts_cbc_decrypt(req);
}

static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *cipher;
	unsigned reqsize;
	unsigned bsize;
	unsigned align;

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

	ctx->child = cipher;

	align = crypto_skcipher_alignmask(tfm);
	bsize = crypto_skcipher_blocksize(cipher);
	reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
			crypto_skcipher_reqsize(cipher),
			crypto_tfm_ctx_alignment()) +
		  (align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;

	crypto_skcipher_set_reqsize(tfm, reqsize);

	return 0;
}

static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
{
	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);

	crypto_free_skcipher(ctx->child);
}

static void crypto_cts_free(struct skcipher_instance *inst)
{
	crypto_drop_skcipher(skcipher_instance_ctx(inst));
	kfree(inst);
}

static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb)
{
	struct crypto_skcipher_spawn *spawn;
	struct skcipher_instance *inst;
	struct crypto_attr_type *algt;
	struct skcipher_alg *alg;
	const char *cipher_name;
	int err;

	algt = crypto_get_attr_type(tb);
	if (IS_ERR(algt))
		return PTR_ERR(algt);

	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
		return -EINVAL;

	cipher_name = crypto_attr_alg_name(tb[1]);
	if (IS_ERR(cipher_name))
		return PTR_ERR(cipher_name);

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

	spawn = skcipher_instance_ctx(inst);

	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
	err = crypto_grab_skcipher(spawn, cipher_name, 0,
				   crypto_requires_sync(algt->type,
							algt->mask));
	if (err)
		goto err_free_inst;

	alg = crypto_spawn_skcipher_alg(spawn);

	err = -EINVAL;
	if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
		goto err_drop_spawn;

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

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

	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
	inst->alg.base.cra_priority = alg->base.cra_priority;
	inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;

	inst->alg.ivsize = alg->base.cra_blocksize;
	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);

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

	inst->alg.init = crypto_cts_init_tfm;
	inst->alg.exit = crypto_cts_exit_tfm;

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

	inst->free = crypto_cts_free;

	err = skcipher_register_instance(tmpl, inst);
	if (err)
		goto err_drop_spawn;

out:
	return err;

err_drop_spawn:
	crypto_drop_skcipher(spawn);
err_free_inst:
	kfree(inst);
	goto out;
}

static struct crypto_template crypto_cts_tmpl = {
	.name = "cts",
	.create = crypto_cts_create,
	.module = THIS_MODULE,
};

static int __init crypto_cts_module_init(void)
{
	return crypto_register_template(&crypto_cts_tmpl);
}

static void __exit crypto_cts_module_exit(void)
{
	crypto_unregister_template(&crypto_cts_tmpl);
}

module_init(crypto_cts_module_init);
module_exit(crypto_cts_module_exit);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
MODULE_ALIAS_CRYPTO("cts");
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
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>
d8c34b94	52	#include <linux/compiler.h>
76cb9521 KC	53
76cb9521 KC	54	struct crypto_cts_ctx {
0605c41c	55	struct crypto_skcipher *child;
76cb9521 KC	56	};
76cb9521 KC	57
0605c41c HX	58	struct crypto_cts_reqctx {
	59	struct scatterlist sg[2];
	60	unsigned offset;
	61	struct skcipher_request subreq;
	62	};
	63
	64	static inline u8 crypto_cts_reqctx_space(struct skcipher_request req)
76cb9521	65	{
0605c41c HX	66	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	67	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	68	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	69	struct crypto_skcipher *child = ctx->child;
76cb9521	70
0605c41c HX	71	return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
0605c41c HX	72	crypto_skcipher_alignmask(tfm) + 1);
76cb9521 KC	73	}
76cb9521 KC	74
0605c41c HX	75	static int crypto_cts_setkey(struct crypto_skcipher parent, const u8 key,
0605c41c HX	76	unsigned int keylen)
76cb9521	77	{
0605c41c HX	78	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
0605c41c HX	79	struct crypto_skcipher *child = ctx->child;
76cb9521 KC	80	int err;
76cb9521 KC	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);
	85	err = crypto_skcipher_setkey(child, key, keylen);
	86	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
	87	CRYPTO_TFM_RES_MASK);
	88	return err;
	89	}
76cb9521	90
0605c41c HX	91	static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
	92	{
	93	struct skcipher_request *req = areq->data;
c4913c7b	94
0605c41c HX	95	if (err == -EINPROGRESS)
0605c41c HX	96	return;
76cb9521	97
0605c41c HX	98	skcipher_request_complete(req, err);
0605c41c HX	99	}
76cb9521	100
0605c41c HX	101	static int cts_cbc_encrypt(struct skcipher_request *req)
	102	{
	103	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	104	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	105	struct skcipher_request *subreq = &rctx->subreq;
	106	int bsize = crypto_skcipher_blocksize(tfm);
d8c34b94	107	u8 d[bsize * 2] __aligned(__alignof__(u32));
0605c41c HX	108	struct scatterlist *sg;
	109	unsigned int offset;
	110	int lastn;
	111
	112	offset = rctx->offset;
	113	lastn = req->cryptlen - offset;
	114
	115	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
	116	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
	117
	118	memset(d, 0, bsize);
	119	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
	120
	121	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
	122	memzero_explicit(d, sizeof(d));
	123
	124	skcipher_request_set_callback(subreq, req->base.flags &
	125	CRYPTO_TFM_REQ_MAY_BACKLOG,
	126	cts_cbc_crypt_done, req);
	127	skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
	128	return crypto_skcipher_encrypt(subreq);
	129	}
76cb9521	130
0605c41c HX	131	static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
	132	{
	133	struct skcipher_request *req = areq->data;
76cb9521	134
0605c41c HX	135	if (err)
0605c41c HX	136	goto out;
76cb9521	137
0605c41c	138	err = cts_cbc_encrypt(req);
4e5b0ad5	139	if (err == -EINPROGRESS \|\| err == -EBUSY)
0605c41c	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);
d8c34b94	186	u8 d[bsize * 2] __aligned(__alignof__(u32));
0605c41c HX	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	230	err = cts_cbc_decrypt(req);
4e5b0ad5	231	if (err == -EINPROGRESS \|\| err == -EBUSY)
0605c41c	232	return;
76cb9521	233
0605c41c HX	234	out:
	235	skcipher_request_complete(req, err);
	236	}
76cb9521	237
0605c41c HX	238	static int crypto_cts_decrypt(struct skcipher_request *req)
	239	{
	240	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	241	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
	242	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	243	struct skcipher_request *subreq = &rctx->subreq;
	244	int bsize = crypto_skcipher_blocksize(tfm);
	245	unsigned int nbytes = req->cryptlen;
	246	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
	247	unsigned int offset;
	248	u8 *space;
	249
	250	skcipher_request_set_tfm(subreq, ctx->child);
	251
	252	if (cbc_blocks <= 0) {
	253	skcipher_request_set_callback(subreq, req->base.flags,
	254	req->base.complete,
	255	req->base.data);
	256	skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
	257	req->iv);
	258	return crypto_skcipher_decrypt(subreq);
	259	}
7185ad26	260
0605c41c HX	261	skcipher_request_set_callback(subreq, req->base.flags,
0605c41c HX	262	crypto_cts_decrypt_done, req);
76cb9521	263
0605c41c	264	space = crypto_cts_reqctx_space(req);
76cb9521	265
0605c41c HX	266	offset = cbc_blocks * bsize;
0605c41c HX	267	rctx->offset = offset;
76cb9521	268
0605c41c HX	269	if (cbc_blocks <= 1)
	270	memcpy(space, req->iv, bsize);
	271	else
	272	scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
	273	bsize, 0);
76cb9521	274
0605c41c HX	275	skcipher_request_set_crypt(subreq, req->src, req->dst,
0605c41c HX	276	offset, req->iv);
76cb9521	277
0605c41c HX	278	return crypto_skcipher_decrypt(subreq) ?:
0605c41c HX	279	cts_cbc_decrypt(req);
76cb9521 KC	280	}
76cb9521 KC	281
0605c41c	282	static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
76cb9521	283	{
0605c41c HX	284	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	285	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
	286	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	287	struct crypto_skcipher *cipher;
	288	unsigned reqsize;
	289	unsigned bsize;
	290	unsigned align;
	291
60425a8b	292	cipher = crypto_spawn_skcipher(spawn);
76cb9521 KC	293	if (IS_ERR(cipher))
	294	return PTR_ERR(cipher);
	295
	296	ctx->child = cipher;
0605c41c HX	297
	298	align = crypto_skcipher_alignmask(tfm);
	299	bsize = crypto_skcipher_blocksize(cipher);
	300	reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
	301	crypto_skcipher_reqsize(cipher),
	302	crypto_tfm_ctx_alignment()) +
	303	(align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
	304
	305	crypto_skcipher_set_reqsize(tfm, reqsize);
	306
76cb9521 KC	307	return 0;
	308	}
	309
0605c41c	310	static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
76cb9521	311	{
0605c41c HX	312	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
	313
	314	crypto_free_skcipher(ctx->child);
76cb9521 KC	315	}
76cb9521 KC	316
0605c41c	317	static void crypto_cts_free(struct skcipher_instance *inst)
76cb9521	318	{
0605c41c HX	319	crypto_drop_skcipher(skcipher_instance_ctx(inst));
	320	kfree(inst);
	321	}
	322
	323	static int crypto_cts_create(struct crypto_template tmpl, struct rtattr *tb)
	324	{
	325	struct crypto_skcipher_spawn *spawn;
	326	struct skcipher_instance *inst;
	327	struct crypto_attr_type *algt;
	328	struct skcipher_alg *alg;
	329	const char *cipher_name;
76cb9521 KC	330	int err;
76cb9521 KC	331
0605c41c HX	332	algt = crypto_get_attr_type(tb);
	333	if (IS_ERR(algt))
	334	return PTR_ERR(algt);
	335
	336	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
	337	return -EINVAL;
	338
	339	cipher_name = crypto_attr_alg_name(tb[1]);
	340	if (IS_ERR(cipher_name))
	341	return PTR_ERR(cipher_name);
	342
	343	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
	344	if (!inst)
	345	return -ENOMEM;
	346
	347	spawn = skcipher_instance_ctx(inst);
	348
	349	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
a35528ec EB	350	err = crypto_grab_skcipher(spawn, cipher_name, 0,
	351	crypto_requires_sync(algt->type,
	352	algt->mask));
76cb9521	353	if (err)
0605c41c	354	goto err_free_inst;
76cb9521	355
0605c41c	356	alg = crypto_spawn_skcipher_alg(spawn);
76cb9521	357
0605c41c HX	358	err = -EINVAL;
	359	if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
	360	goto err_drop_spawn;
76cb9521	361
0605c41c HX	362	if (strncmp(alg->base.cra_name, "cbc(", 4))
0605c41c HX	363	goto err_drop_spawn;
988dc017	364
0605c41c HX	365	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
	366	&alg->base);
	367	if (err)
	368	goto err_drop_spawn;
76cb9521	369
0605c41c HX	370	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
	371	inst->alg.base.cra_priority = alg->base.cra_priority;
	372	inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
	373	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
76cb9521	374
0605c41c HX	375	inst->alg.ivsize = alg->base.cra_blocksize;
	376	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
	377	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
	378	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
76cb9521	379
0605c41c	380	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
76cb9521	381
0605c41c HX	382	inst->alg.init = crypto_cts_init_tfm;
0605c41c HX	383	inst->alg.exit = crypto_cts_exit_tfm;
76cb9521	384
0605c41c HX	385	inst->alg.setkey = crypto_cts_setkey;
	386	inst->alg.encrypt = crypto_cts_encrypt;
	387	inst->alg.decrypt = crypto_cts_decrypt;
76cb9521	388
0605c41c	389	inst->free = crypto_cts_free;
76cb9521	390
0605c41c HX	391	err = skcipher_register_instance(tmpl, inst);
	392	if (err)
	393	goto err_drop_spawn;
	394
	395	out:
	396	return err;
	397
	398	err_drop_spawn:
	399	crypto_drop_skcipher(spawn);
	400	err_free_inst:
76cb9521	401	kfree(inst);
0605c41c	402	goto out;
76cb9521 KC	403	}
	404
	405	static struct crypto_template crypto_cts_tmpl = {
	406	.name = "cts",
0605c41c	407	.create = crypto_cts_create,
76cb9521 KC	408	.module = THIS_MODULE,
	409	};
	410
	411	static int __init crypto_cts_module_init(void)
	412	{
	413	return crypto_register_template(&crypto_cts_tmpl);
	414	}
	415
	416	static void __exit crypto_cts_module_exit(void)
	417	{
	418	crypto_unregister_template(&crypto_cts_tmpl);
	419	}
	420
	421	module_init(crypto_cts_module_init);
	422	module_exit(crypto_cts_module_exit);
	423
	424	MODULE_LICENSE("Dual BSD/GPL");
	425	MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
4943ba16	426	MODULE_ALIAS_CRYPTO("cts");