[linux-2.6-block.git] / crypto / cfb.c

//SPDX-License-Identifier: GPL-2.0
/*
 * CFB: Cipher FeedBack mode
 *
 * Copyright (c) 2018 James.Bottomley@HansenPartnership.com
 *
 * CFB is a stream cipher mode which is layered on to a block
 * encryption scheme.  It works very much like a one time pad where
 * the pad is generated initially from the encrypted IV and then
 * subsequently from the encrypted previous block of ciphertext.  The
 * pad is XOR'd into the plain text to get the final ciphertext.
 *
 * The scheme of CFB is best described by wikipedia:
 *
 * https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#CFB
 *
 * Note that since the pad for both encryption and decryption is
 * generated by an encryption operation, CFB never uses the block
 * decryption function.
 */

#include <crypto/algapi.h>
#include <crypto/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/types.h>

struct crypto_cfb_ctx {
	struct crypto_cipher *child;
};

static unsigned int crypto_cfb_bsize(struct crypto_skcipher *tfm)
{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_cipher *child = ctx->child;

	return crypto_cipher_blocksize(child);
}

static void crypto_cfb_encrypt_one(struct crypto_skcipher *tfm,
					  const u8 *src, u8 *dst)
{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);

	crypto_cipher_encrypt_one(ctx->child, dst, src);
}

/* final encrypt and decrypt is the same */
static void crypto_cfb_final(struct skcipher_walk *walk,
			     struct crypto_skcipher *tfm)
{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	const unsigned long alignmask = crypto_skcipher_alignmask(tfm);
	u8 tmp[bsize + alignmask];
	u8 *stream = PTR_ALIGN(tmp + 0, alignmask + 1);
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	u8 *iv = walk->iv;
	unsigned int nbytes = walk->nbytes;

	crypto_cfb_encrypt_one(tfm, iv, stream);
	crypto_xor_cpy(dst, stream, src, nbytes);
}

static int crypto_cfb_encrypt_segment(struct skcipher_walk *walk,
				      struct crypto_skcipher *tfm)
{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	u8 *iv = walk->iv;

	do {
		crypto_cfb_encrypt_one(tfm, iv, dst);
		crypto_xor(dst, src, bsize);
		memcpy(iv, dst, bsize);

		src += bsize;
		dst += bsize;
	} while ((nbytes -= bsize) >= bsize);

	return nbytes;
}

static int crypto_cfb_encrypt_inplace(struct skcipher_walk *walk,
				      struct crypto_skcipher *tfm)
{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *iv = walk->iv;
	u8 tmp[bsize];

	do {
		crypto_cfb_encrypt_one(tfm, iv, tmp);
		crypto_xor(src, tmp, bsize);
		iv = src;

		src += bsize;
	} while ((nbytes -= bsize) >= bsize);

	memcpy(walk->iv, iv, bsize);

	return nbytes;
}

static int crypto_cfb_encrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct skcipher_walk walk;
	unsigned int bsize = crypto_cfb_bsize(tfm);
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while (walk.nbytes >= bsize) {
		if (walk.src.virt.addr == walk.dst.virt.addr)
			err = crypto_cfb_encrypt_inplace(&walk, tfm);
		else
			err = crypto_cfb_encrypt_segment(&walk, tfm);
		err = skcipher_walk_done(&walk, err);
	}

	if (walk.nbytes) {
		crypto_cfb_final(&walk, tfm);
		err = skcipher_walk_done(&walk, 0);
	}

	return err;
}

static int crypto_cfb_decrypt_segment(struct skcipher_walk *walk,
				      struct crypto_skcipher *tfm)
{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	u8 *iv = walk->iv;

	do {
		crypto_cfb_encrypt_one(tfm, iv, dst);
		crypto_xor(dst, iv, bsize);
		iv = src;

		src += bsize;
		dst += bsize;
	} while ((nbytes -= bsize) >= bsize);

	memcpy(walk->iv, iv, bsize);

	return nbytes;
}

static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
				      struct crypto_skcipher *tfm)
{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *iv = walk->iv;
	u8 tmp[bsize];

	do {
		crypto_cfb_encrypt_one(tfm, iv, tmp);
		memcpy(iv, src, bsize);
		crypto_xor(src, tmp, bsize);
		src += bsize;
	} while ((nbytes -= bsize) >= bsize);

	memcpy(walk->iv, iv, bsize);

	return nbytes;
}

static int crypto_cfb_decrypt_blocks(struct skcipher_walk *walk,
				     struct crypto_skcipher *tfm)
{
	if (walk->src.virt.addr == walk->dst.virt.addr)
		return crypto_cfb_decrypt_inplace(walk, tfm);
	else
		return crypto_cfb_decrypt_segment(walk, tfm);
}

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

	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &
				       CRYPTO_TFM_REQ_MASK);
	err = crypto_cipher_setkey(child, key, keylen);
	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
					  CRYPTO_TFM_RES_MASK);
	return err;
}

static int crypto_cfb_decrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct skcipher_walk walk;
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while (walk.nbytes >= bsize) {
		err = crypto_cfb_decrypt_blocks(&walk, tfm);
		err = skcipher_walk_done(&walk, err);
	}

	if (walk.nbytes) {
		crypto_cfb_final(&walk, tfm);
		err = skcipher_walk_done(&walk, 0);
	}

	return err;
}

static int crypto_cfb_init_tfm(struct crypto_skcipher *tfm)
{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_cipher *cipher;

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

	ctx->child = cipher;
	return 0;
}

static void crypto_cfb_exit_tfm(struct crypto_skcipher *tfm)
{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);

	crypto_free_cipher(ctx->child);
}

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

static int crypto_cfb_create(struct crypto_template *tmpl, struct rtattr **tb)
{
	struct skcipher_instance *inst;
	struct crypto_attr_type *algt;
	struct crypto_spawn *spawn;
	struct crypto_alg *alg;
	u32 mask;
	int err;

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

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

	algt = crypto_get_attr_type(tb);
	err = PTR_ERR(algt);
	if (IS_ERR(algt))
		goto err_free_inst;

	mask = CRYPTO_ALG_TYPE_MASK |
		crypto_requires_off(algt->type, algt->mask,
				    CRYPTO_ALG_NEED_FALLBACK);

	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
	err = PTR_ERR(alg);
	if (IS_ERR(alg))
		goto err_free_inst;

	spawn = skcipher_instance_ctx(inst);
	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
				CRYPTO_ALG_TYPE_MASK);
	crypto_mod_put(alg);
	if (err)
		goto err_free_inst;

	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cfb", alg);
	if (err)
		goto err_drop_spawn;

	inst->alg.base.cra_priority = alg->cra_priority;
	/* we're a stream cipher independend of the crypto cra_blocksize */
	inst->alg.base.cra_blocksize = 1;
	inst->alg.base.cra_alignmask = alg->cra_alignmask;

	inst->alg.ivsize = alg->cra_blocksize;
	inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
	inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;

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

	inst->alg.init = crypto_cfb_init_tfm;
	inst->alg.exit = crypto_cfb_exit_tfm;

	inst->alg.setkey = crypto_cfb_setkey;
	inst->alg.encrypt = crypto_cfb_encrypt;
	inst->alg.decrypt = crypto_cfb_decrypt;

	inst->free = crypto_cfb_free;

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

out:
	return err;

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

static struct crypto_template crypto_cfb_tmpl = {
	.name = "cfb",
	.create = crypto_cfb_create,
	.module = THIS_MODULE,
};

static int __init crypto_cfb_module_init(void)
{
	return crypto_register_template(&crypto_cfb_tmpl);
}

static void __exit crypto_cfb_module_exit(void)
{
	crypto_unregister_template(&crypto_cfb_tmpl);
}

module_init(crypto_cfb_module_init);
module_exit(crypto_cfb_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("CFB block cipher algorithm");
MODULE_ALIAS_CRYPTO("cfb");
Commit	Line	Data
a7d85e06 JB	1	//SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* CFB: Cipher FeedBack mode
	4	*
	5	* Copyright (c) 2018 James.Bottomley@HansenPartnership.com
	6	*
	7	* CFB is a stream cipher mode which is layered on to a block
	8	* encryption scheme. It works very much like a one time pad where
	9	* the pad is generated initially from the encrypted IV and then
	10	* subsequently from the encrypted previous block of ciphertext. The
	11	* pad is XOR'd into the plain text to get the final ciphertext.
	12	*
	13	* The scheme of CFB is best described by wikipedia:
	14	*
	15	* https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#CFB
	16	*
	17	* Note that since the pad for both encryption and decryption is
	18	* generated by an encryption operation, CFB never uses the block
	19	* decryption function.
	20	*/
	21
	22	#include <crypto/algapi.h>
	23	#include <crypto/internal/skcipher.h>
	24	#include <linux/err.h>
	25	#include <linux/init.h>
	26	#include <linux/kernel.h>
	27	#include <linux/module.h>
	28	#include <linux/slab.h>
	29	#include <linux/string.h>
	30	#include <linux/types.h>
	31
	32	struct crypto_cfb_ctx {
	33	struct crypto_cipher *child;
	34	};
	35
	36	static unsigned int crypto_cfb_bsize(struct crypto_skcipher *tfm)
	37	{
	38	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
	39	struct crypto_cipher *child = ctx->child;
	40
	41	return crypto_cipher_blocksize(child);
	42	}
	43
	44	static void crypto_cfb_encrypt_one(struct crypto_skcipher *tfm,
	45	const u8 src, u8 dst)
	46	{
	47	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
	48
	49	crypto_cipher_encrypt_one(ctx->child, dst, src);
	50	}
	51
	52	/* final encrypt and decrypt is the same */
	53	static void crypto_cfb_final(struct skcipher_walk *walk,
	54	struct crypto_skcipher *tfm)
	55	{
	56	const unsigned int bsize = crypto_cfb_bsize(tfm);
	57	const unsigned long alignmask = crypto_skcipher_alignmask(tfm);
	58	u8 tmp[bsize + alignmask];
	59	u8 *stream = PTR_ALIGN(tmp + 0, alignmask + 1);
	60	u8 *src = walk->src.virt.addr;
	61	u8 *dst = walk->dst.virt.addr;
	62	u8 *iv = walk->iv;
	63	unsigned int nbytes = walk->nbytes;
	64
65	crypto_cfb_encrypt_one(tfm, iv, stream);
66	crypto_xor_cpy(dst, stream, src, nbytes);
67	}
68
69	static int crypto_cfb_encrypt_segment(struct skcipher_walk *walk,
70	struct crypto_skcipher *tfm)
71	{
72	const unsigned int bsize = crypto_cfb_bsize(tfm);
73	unsigned int nbytes = walk->nbytes;
74	u8 *src = walk->src.virt.addr;
75	u8 *dst = walk->dst.virt.addr;
76	u8 *iv = walk->iv;
77
78	do {
79	crypto_cfb_encrypt_one(tfm, iv, dst);
80	crypto_xor(dst, src, bsize);
81	memcpy(iv, dst, bsize);
82
83	src += bsize;
84	dst += bsize;
85	} while ((nbytes -= bsize) >= bsize);
86
87	return nbytes;
88	}
89
90	static int crypto_cfb_encrypt_inplace(struct skcipher_walk *walk,
91	struct crypto_skcipher *tfm)
92	{
93	const unsigned int bsize = crypto_cfb_bsize(tfm);
94	unsigned int nbytes = walk->nbytes;
95	u8 *src = walk->src.virt.addr;
96	u8 *iv = walk->iv;
97	u8 tmp[bsize];
98
99	do {
100	crypto_cfb_encrypt_one(tfm, iv, tmp);
101	crypto_xor(src, tmp, bsize);
102	iv = src;
103
104	src += bsize;
105	} while ((nbytes -= bsize) >= bsize);
106
107	memcpy(walk->iv, iv, bsize);
108
109	return nbytes;
110	}
111
112	static int crypto_cfb_encrypt(struct skcipher_request *req)
113	{
114	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
115	struct skcipher_walk walk;
116	unsigned int bsize = crypto_cfb_bsize(tfm);
117	int err;
118
119	err = skcipher_walk_virt(&walk, req, false);
120
121	while (walk.nbytes >= bsize) {
122	if (walk.src.virt.addr == walk.dst.virt.addr)
123	err = crypto_cfb_encrypt_inplace(&walk, tfm);
124	else
125	err = crypto_cfb_encrypt_segment(&walk, tfm);
126	err = skcipher_walk_done(&walk, err);
127	}
128
129	if (walk.nbytes) {
130	crypto_cfb_final(&walk, tfm);
131	err = skcipher_walk_done(&walk, 0);
132	}
133
134	return err;
135	}
136
137	static int crypto_cfb_decrypt_segment(struct skcipher_walk *walk,
138	struct crypto_skcipher *tfm)
139	{
140	const unsigned int bsize = crypto_cfb_bsize(tfm);
141	unsigned int nbytes = walk->nbytes;
142	u8 *src = walk->src.virt.addr;
143	u8 *dst = walk->dst.virt.addr;
144	u8 *iv = walk->iv;
145
146	do {
147	crypto_cfb_encrypt_one(tfm, iv, dst);
148	crypto_xor(dst, iv, bsize);
149	iv = src;
150
151	src += bsize;
152	dst += bsize;
153	} while ((nbytes -= bsize) >= bsize);
154
155	memcpy(walk->iv, iv, bsize);
156
157	return nbytes;
158	}
159
160	static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
161	struct crypto_skcipher *tfm)
162	{
163	const unsigned int bsize = crypto_cfb_bsize(tfm);
164	unsigned int nbytes = walk->nbytes;
165	u8 *src = walk->src.virt.addr;
166	u8 *iv = walk->iv;
167	u8 tmp[bsize];
168
169	do {
170	crypto_cfb_encrypt_one(tfm, iv, tmp);
171	memcpy(iv, src, bsize);
172	crypto_xor(src, tmp, bsize);
173	src += bsize;
174	} while ((nbytes -= bsize) >= bsize);
175
176	memcpy(walk->iv, iv, bsize);
177
178	return nbytes;
179	}
180
181	static int crypto_cfb_decrypt_blocks(struct skcipher_walk *walk,
182	struct crypto_skcipher *tfm)
183	{
184	if (walk->src.virt.addr == walk->dst.virt.addr)
185	return crypto_cfb_decrypt_inplace(walk, tfm);
186	else
187	return crypto_cfb_decrypt_segment(walk, tfm);
188	}
189
190	static int crypto_cfb_setkey(struct crypto_skcipher parent, const u8 key,
191	unsigned int keylen)
192	{
193	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(parent);
194	struct crypto_cipher *child = ctx->child;
195	int err;
196
197	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
198	crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &
199	CRYPTO_TFM_REQ_MASK);
200	err = crypto_cipher_setkey(child, key, keylen);
201	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
202	CRYPTO_TFM_RES_MASK);
203	return err;
204	}
205
206	static int crypto_cfb_decrypt(struct skcipher_request *req)
207	{
208	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
209	struct skcipher_walk walk;
210	const unsigned int bsize = crypto_cfb_bsize(tfm);
211	int err;
212
213	err = skcipher_walk_virt(&walk, req, false);
214
215	while (walk.nbytes >= bsize) {
216	err = crypto_cfb_decrypt_blocks(&walk, tfm);
217	err = skcipher_walk_done(&walk, err);
218	}
219
220	if (walk.nbytes) {
221	crypto_cfb_final(&walk, tfm);
222	err = skcipher_walk_done(&walk, 0);
223	}
224
225	return err;
226	}
227
228	static int crypto_cfb_init_tfm(struct crypto_skcipher *tfm)
229	{
230	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
231	struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
232	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
233	struct crypto_cipher *cipher;
234
235	cipher = crypto_spawn_cipher(spawn);
236	if (IS_ERR(cipher))
237	return PTR_ERR(cipher);
238
239	ctx->child = cipher;
240	return 0;
241	}
242
243	static void crypto_cfb_exit_tfm(struct crypto_skcipher *tfm)
244	{
245	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
246
247	crypto_free_cipher(ctx->child);
248	}
249
250	static void crypto_cfb_free(struct skcipher_instance *inst)
251	{
252	crypto_drop_skcipher(skcipher_instance_ctx(inst));
253	kfree(inst);
254	}
255
256	static int crypto_cfb_create(struct crypto_template tmpl, struct rtattr *tb)
257	{
258	struct skcipher_instance *inst;
259	struct crypto_attr_type *algt;
260	struct crypto_spawn *spawn;
261	struct crypto_alg *alg;
262	u32 mask;
263	int err;
264
265	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);
266	if (err)
267	return err;
268
269	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
270	if (!inst)
271	return -ENOMEM;
272
273	algt = crypto_get_attr_type(tb);
274	err = PTR_ERR(algt);
275	if (IS_ERR(algt))
276	goto err_free_inst;
277
278	mask = CRYPTO_ALG_TYPE_MASK \|
279	crypto_requires_off(algt->type, algt->mask,
280	CRYPTO_ALG_NEED_FALLBACK);
281
282	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
283	err = PTR_ERR(alg);
284	if (IS_ERR(alg))
285	goto err_free_inst;
286
287	spawn = skcipher_instance_ctx(inst);
288	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
289	CRYPTO_ALG_TYPE_MASK);
290	crypto_mod_put(alg);
291	if (err)
292	goto err_free_inst;
293
294	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cfb", alg);
295	if (err)
296	goto err_drop_spawn;
297
298	inst->alg.base.cra_priority = alg->cra_priority;
299	/* we're a stream cipher independend of the crypto cra_blocksize */
300	inst->alg.base.cra_blocksize = 1;
301	inst->alg.base.cra_alignmask = alg->cra_alignmask;
302
303	inst->alg.ivsize = alg->cra_blocksize;
304	inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
305	inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;
306
307	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cfb_ctx);
308
309	inst->alg.init = crypto_cfb_init_tfm;
310	inst->alg.exit = crypto_cfb_exit_tfm;
311
312	inst->alg.setkey = crypto_cfb_setkey;
313	inst->alg.encrypt = crypto_cfb_encrypt;
314	inst->alg.decrypt = crypto_cfb_decrypt;
315
316	inst->free = crypto_cfb_free;
317
318	err = skcipher_register_instance(tmpl, inst);
319	if (err)
320	goto err_drop_spawn;
321
322	out:
323	return err;
324
325	err_drop_spawn:
326	crypto_drop_spawn(spawn);
327	err_free_inst:
328	kfree(inst);
329	goto out;
330	}
331
332	static struct crypto_template crypto_cfb_tmpl = {
333	.name = "cfb",
334	.create = crypto_cfb_create,
335	.module = THIS_MODULE,
336	};
337
338	static int __init crypto_cfb_module_init(void)
339	{
340	return crypto_register_template(&crypto_cfb_tmpl);
341	}
342
343	static void __exit crypto_cfb_module_exit(void)
344	{
345	crypto_unregister_template(&crypto_cfb_tmpl);
346	}
347
348	module_init(crypto_cfb_module_init);
349	module_exit(crypto_cfb_module_exit);
350
351	MODULE_LICENSE("GPL");
352	MODULE_DESCRIPTION("CFB block cipher algorithm");
353	MODULE_ALIAS_CRYPTO("cfb");