1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* XTS: as defined in IEEE1619/D16
3  *	http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
4  *
5  * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
6  *
7  * Based on ecb.c
8  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
9  */
10 #include <crypto/internal/skcipher.h>
11 #include <crypto/scatterwalk.h>
12 #include <linux/err.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/scatterlist.h>
17 #include <linux/slab.h>
18 
19 #include <crypto/xts.h>
20 #include <crypto/b128ops.h>
21 #include <crypto/gf128mul.h>
22 
23 struct xts_tfm_ctx {
24 	struct crypto_skcipher *child;
25 	struct crypto_cipher *tweak;
26 };
27 
28 struct xts_instance_ctx {
29 	struct crypto_skcipher_spawn spawn;
30 	char name[CRYPTO_MAX_ALG_NAME];
31 };
32 
33 struct xts_request_ctx {
34 	le128 t;
35 	struct scatterlist *tail;
36 	struct scatterlist sg[2];
37 	struct skcipher_request subreq;
38 };
39 
xts_setkey(struct crypto_skcipher * parent,const u8 * key,unsigned int keylen)40 static int xts_setkey(struct crypto_skcipher *parent, const u8 *key,
41 		      unsigned int keylen)
42 {
43 	struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(parent);
44 	struct crypto_skcipher *child;
45 	struct crypto_cipher *tweak;
46 	int err;
47 
48 	err = xts_verify_key(parent, key, keylen);
49 	if (err)
50 		return err;
51 
52 	keylen /= 2;
53 
54 	/* we need two cipher instances: one to compute the initial 'tweak'
55 	 * by encrypting the IV (usually the 'plain' iv) and the other
56 	 * one to encrypt and decrypt the data */
57 
58 	/* tweak cipher, uses Key2 i.e. the second half of *key */
59 	tweak = ctx->tweak;
60 	crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
61 	crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
62 				       CRYPTO_TFM_REQ_MASK);
63 	err = crypto_cipher_setkey(tweak, key + keylen, keylen);
64 	if (err)
65 		return err;
66 
67 	/* data cipher, uses Key1 i.e. the first half of *key */
68 	child = ctx->child;
69 	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
70 	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
71 					 CRYPTO_TFM_REQ_MASK);
72 	return crypto_skcipher_setkey(child, key, keylen);
73 }
74 
75 /*
76  * We compute the tweak masks twice (both before and after the ECB encryption or
77  * decryption) to avoid having to allocate a temporary buffer and/or make
78  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
79  * just doing the gf128mul_x_ble() calls again.
80  */
xts_xor_tweak(struct skcipher_request * req,bool second_pass,bool enc)81 static int xts_xor_tweak(struct skcipher_request *req, bool second_pass,
82 			 bool enc)
83 {
84 	struct xts_request_ctx *rctx = skcipher_request_ctx(req);
85 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
86 	const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);
87 	const int bs = XTS_BLOCK_SIZE;
88 	struct skcipher_walk w;
89 	le128 t = rctx->t;
90 	int err;
91 
92 	if (second_pass) {
93 		req = &rctx->subreq;
94 		/* set to our TFM to enforce correct alignment: */
95 		skcipher_request_set_tfm(req, tfm);
96 	}
97 	err = skcipher_walk_virt(&w, req, false);
98 
99 	while (w.nbytes) {
100 		unsigned int avail = w.nbytes;
101 		le128 *wsrc;
102 		le128 *wdst;
103 
104 		wsrc = w.src.virt.addr;
105 		wdst = w.dst.virt.addr;
106 
107 		do {
108 			if (unlikely(cts) &&
109 			    w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
110 				if (!enc) {
111 					if (second_pass)
112 						rctx->t = t;
113 					gf128mul_x_ble(&t, &t);
114 				}
115 				le128_xor(wdst, &t, wsrc);
116 				if (enc && second_pass)
117 					gf128mul_x_ble(&rctx->t, &t);
118 				skcipher_walk_done(&w, avail - bs);
119 				return 0;
120 			}
121 
122 			le128_xor(wdst++, &t, wsrc++);
123 			gf128mul_x_ble(&t, &t);
124 		} while ((avail -= bs) >= bs);
125 
126 		err = skcipher_walk_done(&w, avail);
127 	}
128 
129 	return err;
130 }
131 
xts_xor_tweak_pre(struct skcipher_request * req,bool enc)132 static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc)
133 {
134 	return xts_xor_tweak(req, false, enc);
135 }
136 
xts_xor_tweak_post(struct skcipher_request * req,bool enc)137 static int xts_xor_tweak_post(struct skcipher_request *req, bool enc)
138 {
139 	return xts_xor_tweak(req, true, enc);
140 }
141 
xts_cts_done(struct crypto_async_request * areq,int err)142 static void xts_cts_done(struct crypto_async_request *areq, int err)
143 {
144 	struct skcipher_request *req = areq->data;
145 	le128 b;
146 
147 	if (!err) {
148 		struct xts_request_ctx *rctx = skcipher_request_ctx(req);
149 
150 		scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
151 		le128_xor(&b, &rctx->t, &b);
152 		scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
153 	}
154 
155 	skcipher_request_complete(req, err);
156 }
157 
xts_cts_final(struct skcipher_request * req,int (* crypt)(struct skcipher_request * req))158 static int xts_cts_final(struct skcipher_request *req,
159 			 int (*crypt)(struct skcipher_request *req))
160 {
161 	const struct xts_tfm_ctx *ctx =
162 		crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
163 	int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
164 	struct xts_request_ctx *rctx = skcipher_request_ctx(req);
165 	struct skcipher_request *subreq = &rctx->subreq;
166 	int tail = req->cryptlen % XTS_BLOCK_SIZE;
167 	le128 b[2];
168 	int err;
169 
170 	rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst,
171 				      offset - XTS_BLOCK_SIZE);
172 
173 	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
174 	b[1] = b[0];
175 	scatterwalk_map_and_copy(b, req->src, offset, tail, 0);
176 
177 	le128_xor(b, &rctx->t, b);
178 
179 	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1);
180 
181 	skcipher_request_set_tfm(subreq, ctx->child);
182 	skcipher_request_set_callback(subreq, req->base.flags, xts_cts_done,
183 				      req);
184 	skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail,
185 				   XTS_BLOCK_SIZE, NULL);
186 
187 	err = crypt(subreq);
188 	if (err)
189 		return err;
190 
191 	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
192 	le128_xor(b, &rctx->t, b);
193 	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
194 
195 	return 0;
196 }
197 
xts_encrypt_done(struct crypto_async_request * areq,int err)198 static void xts_encrypt_done(struct crypto_async_request *areq, int err)
199 {
200 	struct skcipher_request *req = areq->data;
201 
202 	if (!err) {
203 		struct xts_request_ctx *rctx = skcipher_request_ctx(req);
204 
205 		rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
206 		err = xts_xor_tweak_post(req, true);
207 
208 		if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
209 			err = xts_cts_final(req, crypto_skcipher_encrypt);
210 			if (err == -EINPROGRESS)
211 				return;
212 		}
213 	}
214 
215 	skcipher_request_complete(req, err);
216 }
217 
xts_decrypt_done(struct crypto_async_request * areq,int err)218 static void xts_decrypt_done(struct crypto_async_request *areq, int err)
219 {
220 	struct skcipher_request *req = areq->data;
221 
222 	if (!err) {
223 		struct xts_request_ctx *rctx = skcipher_request_ctx(req);
224 
225 		rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
226 		err = xts_xor_tweak_post(req, false);
227 
228 		if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
229 			err = xts_cts_final(req, crypto_skcipher_decrypt);
230 			if (err == -EINPROGRESS)
231 				return;
232 		}
233 	}
234 
235 	skcipher_request_complete(req, err);
236 }
237 
xts_init_crypt(struct skcipher_request * req,crypto_completion_t compl)238 static int xts_init_crypt(struct skcipher_request *req,
239 			  crypto_completion_t compl)
240 {
241 	const struct xts_tfm_ctx *ctx =
242 		crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
243 	struct xts_request_ctx *rctx = skcipher_request_ctx(req);
244 	struct skcipher_request *subreq = &rctx->subreq;
245 
246 	if (req->cryptlen < XTS_BLOCK_SIZE)
247 		return -EINVAL;
248 
249 	skcipher_request_set_tfm(subreq, ctx->child);
250 	skcipher_request_set_callback(subreq, req->base.flags, compl, req);
251 	skcipher_request_set_crypt(subreq, req->dst, req->dst,
252 				   req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);
253 
254 	/* calculate first value of T */
255 	crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
256 
257 	return 0;
258 }
259 
xts_encrypt(struct skcipher_request * req)260 static int xts_encrypt(struct skcipher_request *req)
261 {
262 	struct xts_request_ctx *rctx = skcipher_request_ctx(req);
263 	struct skcipher_request *subreq = &rctx->subreq;
264 	int err;
265 
266 	err = xts_init_crypt(req, xts_encrypt_done) ?:
267 	      xts_xor_tweak_pre(req, true) ?:
268 	      crypto_skcipher_encrypt(subreq) ?:
269 	      xts_xor_tweak_post(req, true);
270 
271 	if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
272 		return err;
273 
274 	return xts_cts_final(req, crypto_skcipher_encrypt);
275 }
276 
xts_decrypt(struct skcipher_request * req)277 static int xts_decrypt(struct skcipher_request *req)
278 {
279 	struct xts_request_ctx *rctx = skcipher_request_ctx(req);
280 	struct skcipher_request *subreq = &rctx->subreq;
281 	int err;
282 
283 	err = xts_init_crypt(req, xts_decrypt_done) ?:
284 	      xts_xor_tweak_pre(req, false) ?:
285 	      crypto_skcipher_decrypt(subreq) ?:
286 	      xts_xor_tweak_post(req, false);
287 
288 	if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
289 		return err;
290 
291 	return xts_cts_final(req, crypto_skcipher_decrypt);
292 }
293 
xts_init_tfm(struct crypto_skcipher * tfm)294 static int xts_init_tfm(struct crypto_skcipher *tfm)
295 {
296 	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
297 	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
298 	struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
299 	struct crypto_skcipher *child;
300 	struct crypto_cipher *tweak;
301 
302 	child = crypto_spawn_skcipher(&ictx->spawn);
303 	if (IS_ERR(child))
304 		return PTR_ERR(child);
305 
306 	ctx->child = child;
307 
308 	tweak = crypto_alloc_cipher(ictx->name, 0, 0);
309 	if (IS_ERR(tweak)) {
310 		crypto_free_skcipher(ctx->child);
311 		return PTR_ERR(tweak);
312 	}
313 
314 	ctx->tweak = tweak;
315 
316 	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
317 					 sizeof(struct xts_request_ctx));
318 
319 	return 0;
320 }
321 
xts_exit_tfm(struct crypto_skcipher * tfm)322 static void xts_exit_tfm(struct crypto_skcipher *tfm)
323 {
324 	struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
325 
326 	crypto_free_skcipher(ctx->child);
327 	crypto_free_cipher(ctx->tweak);
328 }
329 
xts_free_instance(struct skcipher_instance * inst)330 static void xts_free_instance(struct skcipher_instance *inst)
331 {
332 	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
333 
334 	crypto_drop_skcipher(&ictx->spawn);
335 	kfree(inst);
336 }
337 
xts_create(struct crypto_template * tmpl,struct rtattr ** tb)338 static int xts_create(struct crypto_template *tmpl, struct rtattr **tb)
339 {
340 	struct skcipher_instance *inst;
341 	struct xts_instance_ctx *ctx;
342 	struct skcipher_alg *alg;
343 	const char *cipher_name;
344 	u32 mask;
345 	int err;
346 
347 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
348 	if (err)
349 		return err;
350 
351 	cipher_name = crypto_attr_alg_name(tb[1]);
352 	if (IS_ERR(cipher_name))
353 		return PTR_ERR(cipher_name);
354 
355 	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
356 	if (!inst)
357 		return -ENOMEM;
358 
359 	ctx = skcipher_instance_ctx(inst);
360 
361 	err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst),
362 				   cipher_name, 0, mask);
363 	if (err == -ENOENT) {
364 		err = -ENAMETOOLONG;
365 		if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
366 			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
367 			goto err_free_inst;
368 
369 		err = crypto_grab_skcipher(&ctx->spawn,
370 					   skcipher_crypto_instance(inst),
371 					   ctx->name, 0, mask);
372 	}
373 
374 	if (err)
375 		goto err_free_inst;
376 
377 	alg = crypto_skcipher_spawn_alg(&ctx->spawn);
378 
379 	err = -EINVAL;
380 	if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
381 		goto err_free_inst;
382 
383 	if (crypto_skcipher_alg_ivsize(alg))
384 		goto err_free_inst;
385 
386 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
387 				  &alg->base);
388 	if (err)
389 		goto err_free_inst;
390 
391 	err = -EINVAL;
392 	cipher_name = alg->base.cra_name;
393 
394 	/* Alas we screwed up the naming so we have to mangle the
395 	 * cipher name.
396 	 */
397 	if (!strncmp(cipher_name, "ecb(", 4)) {
398 		unsigned len;
399 
400 		len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
401 		if (len < 2 || len >= sizeof(ctx->name))
402 			goto err_free_inst;
403 
404 		if (ctx->name[len - 1] != ')')
405 			goto err_free_inst;
406 
407 		ctx->name[len - 1] = 0;
408 
409 		if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
410 			     "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
411 			err = -ENAMETOOLONG;
412 			goto err_free_inst;
413 		}
414 	} else
415 		goto err_free_inst;
416 
417 	inst->alg.base.cra_priority = alg->base.cra_priority;
418 	inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
419 	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
420 				       (__alignof__(u64) - 1);
421 
422 	inst->alg.ivsize = XTS_BLOCK_SIZE;
423 	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
424 	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
425 
426 	inst->alg.base.cra_ctxsize = sizeof(struct xts_tfm_ctx);
427 
428 	inst->alg.init = xts_init_tfm;
429 	inst->alg.exit = xts_exit_tfm;
430 
431 	inst->alg.setkey = xts_setkey;
432 	inst->alg.encrypt = xts_encrypt;
433 	inst->alg.decrypt = xts_decrypt;
434 
435 	inst->free = xts_free_instance;
436 
437 	err = skcipher_register_instance(tmpl, inst);
438 	if (err) {
439 err_free_inst:
440 		xts_free_instance(inst);
441 	}
442 	return err;
443 }
444 
445 static struct crypto_template xts_tmpl = {
446 	.name = "xts",
447 	.create = xts_create,
448 	.module = THIS_MODULE,
449 };
450 
xts_module_init(void)451 static int __init xts_module_init(void)
452 {
453 	return crypto_register_template(&xts_tmpl);
454 }
455 
xts_module_exit(void)456 static void __exit xts_module_exit(void)
457 {
458 	crypto_unregister_template(&xts_tmpl);
459 }
460 
461 subsys_initcall(xts_module_init);
462 module_exit(xts_module_exit);
463 
464 MODULE_LICENSE("GPL");
465 MODULE_DESCRIPTION("XTS block cipher mode");
466 MODULE_ALIAS_CRYPTO("xts");
467