xref: /openbmc/linux/crypto/xts.c (revision 3b23dc52) 
1 /* XTS: as defined in IEEE1619/D16
2  *	http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
3  *	(sector sizes which are not a multiple of 16 bytes are,
4  *	however currently unsupported)
5  *
6  * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
7  *
8  * Based on ecb.c
9  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
10  *
11  * This program is free software; you can redistribute it and/or modify it
12  * under the terms of the GNU General Public License as published by the Free
13  * Software Foundation; either version 2 of the License, or (at your option)
14  * any later version.
15  */
16 #include <crypto/internal/skcipher.h>
17 #include <crypto/scatterwalk.h>
18 #include <linux/err.h>
19 #include <linux/init.h>
20 #include <linux/kernel.h>
21 #include <linux/module.h>
22 #include <linux/scatterlist.h>
23 #include <linux/slab.h>
24 
25 #include <crypto/xts.h>
26 #include <crypto/b128ops.h>
27 #include <crypto/gf128mul.h>
28 
29 #define XTS_BUFFER_SIZE 128u
30 
31 struct priv {
32 	struct crypto_skcipher *child;
33 	struct crypto_cipher *tweak;
34 };
35 
36 struct xts_instance_ctx {
37 	struct crypto_skcipher_spawn spawn;
38 	char name[CRYPTO_MAX_ALG_NAME];
39 };
40 
41 struct rctx {
42 	le128 buf[XTS_BUFFER_SIZE / sizeof(le128)];
43 
44 	le128 t;
45 
46 	le128 *ext;
47 
48 	struct scatterlist srcbuf[2];
49 	struct scatterlist dstbuf[2];
50 	struct scatterlist *src;
51 	struct scatterlist *dst;
52 
53 	unsigned int left;
54 
55 	struct skcipher_request subreq;
56 };
57 
58 static int setkey(struct crypto_skcipher *parent, const u8 *key,
59 		  unsigned int keylen)
60 {
61 	struct priv *ctx = crypto_skcipher_ctx(parent);
62 	struct crypto_skcipher *child;
63 	struct crypto_cipher *tweak;
64 	int err;
65 
66 	err = xts_verify_key(parent, key, keylen);
67 	if (err)
68 		return err;
69 
70 	keylen /= 2;
71 
72 	/* we need two cipher instances: one to compute the initial 'tweak'
73 	 * by encrypting the IV (usually the 'plain' iv) and the other
74 	 * one to encrypt and decrypt the data */
75 
76 	/* tweak cipher, uses Key2 i.e. the second half of *key */
77 	tweak = ctx->tweak;
78 	crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
79 	crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
80 				       CRYPTO_TFM_REQ_MASK);
81 	err = crypto_cipher_setkey(tweak, key + keylen, keylen);
82 	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
83 					  CRYPTO_TFM_RES_MASK);
84 	if (err)
85 		return err;
86 
87 	/* data cipher, uses Key1 i.e. the first half of *key */
88 	child = ctx->child;
89 	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
90 	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
91 					 CRYPTO_TFM_REQ_MASK);
92 	err = crypto_skcipher_setkey(child, key, keylen);
93 	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
94 					  CRYPTO_TFM_RES_MASK);
95 
96 	return err;
97 }
98 
99 static int post_crypt(struct skcipher_request *req)
100 {
101 	struct rctx *rctx = skcipher_request_ctx(req);
102 	le128 *buf = rctx->ext ?: rctx->buf;
103 	struct skcipher_request *subreq;
104 	const int bs = XTS_BLOCK_SIZE;
105 	struct skcipher_walk w;
106 	struct scatterlist *sg;
107 	unsigned offset;
108 	int err;
109 
110 	subreq = &rctx->subreq;
111 	err = skcipher_walk_virt(&w, subreq, false);
112 
113 	while (w.nbytes) {
114 		unsigned int avail = w.nbytes;
115 		le128 *wdst;
116 
117 		wdst = w.dst.virt.addr;
118 
119 		do {
120 			le128_xor(wdst, buf++, wdst);
121 			wdst++;
122 		} while ((avail -= bs) >= bs);
123 
124 		err = skcipher_walk_done(&w, avail);
125 	}
126 
127 	rctx->left -= subreq->cryptlen;
128 
129 	if (err || !rctx->left)
130 		goto out;
131 
132 	rctx->dst = rctx->dstbuf;
133 
134 	scatterwalk_done(&w.out, 0, 1);
135 	sg = w.out.sg;
136 	offset = w.out.offset;
137 
138 	if (rctx->dst != sg) {
139 		rctx->dst[0] = *sg;
140 		sg_unmark_end(rctx->dst);
141 		scatterwalk_crypto_chain(rctx->dst, sg_next(sg), 0, 2);
142 	}
143 	rctx->dst[0].length -= offset - sg->offset;
144 	rctx->dst[0].offset = offset;
145 
146 out:
147 	return err;
148 }
149 
150 static int pre_crypt(struct skcipher_request *req)
151 {
152 	struct rctx *rctx = skcipher_request_ctx(req);
153 	le128 *buf = rctx->ext ?: rctx->buf;
154 	struct skcipher_request *subreq;
155 	const int bs = XTS_BLOCK_SIZE;
156 	struct skcipher_walk w;
157 	struct scatterlist *sg;
158 	unsigned cryptlen;
159 	unsigned offset;
160 	bool more;
161 	int err;
162 
163 	subreq = &rctx->subreq;
164 	cryptlen = subreq->cryptlen;
165 
166 	more = rctx->left > cryptlen;
167 	if (!more)
168 		cryptlen = rctx->left;
169 
170 	skcipher_request_set_crypt(subreq, rctx->src, rctx->dst,
171 				   cryptlen, NULL);
172 
173 	err = skcipher_walk_virt(&w, subreq, false);
174 
175 	while (w.nbytes) {
176 		unsigned int avail = w.nbytes;
177 		le128 *wsrc;
178 		le128 *wdst;
179 
180 		wsrc = w.src.virt.addr;
181 		wdst = w.dst.virt.addr;
182 
183 		do {
184 			*buf++ = rctx->t;
185 			le128_xor(wdst++, &rctx->t, wsrc++);
186 			gf128mul_x_ble(&rctx->t, &rctx->t);
187 		} while ((avail -= bs) >= bs);
188 
189 		err = skcipher_walk_done(&w, avail);
190 	}
191 
192 	skcipher_request_set_crypt(subreq, rctx->dst, rctx->dst,
193 				   cryptlen, NULL);
194 
195 	if (err || !more)
196 		goto out;
197 
198 	rctx->src = rctx->srcbuf;
199 
200 	scatterwalk_done(&w.in, 0, 1);
201 	sg = w.in.sg;
202 	offset = w.in.offset;
203 
204 	if (rctx->src != sg) {
205 		rctx->src[0] = *sg;
206 		sg_unmark_end(rctx->src);
207 		scatterwalk_crypto_chain(rctx->src, sg_next(sg), 0, 2);
208 	}
209 	rctx->src[0].length -= offset - sg->offset;
210 	rctx->src[0].offset = offset;
211 
212 out:
213 	return err;
214 }
215 
216 static int init_crypt(struct skcipher_request *req, crypto_completion_t done)
217 {
218 	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
219 	struct rctx *rctx = skcipher_request_ctx(req);
220 	struct skcipher_request *subreq;
221 	gfp_t gfp;
222 
223 	subreq = &rctx->subreq;
224 	skcipher_request_set_tfm(subreq, ctx->child);
225 	skcipher_request_set_callback(subreq, req->base.flags, done, req);
226 
227 	gfp = req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL :
228 							   GFP_ATOMIC;
229 	rctx->ext = NULL;
230 
231 	subreq->cryptlen = XTS_BUFFER_SIZE;
232 	if (req->cryptlen > XTS_BUFFER_SIZE) {
233 		unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);
234 
235 		rctx->ext = kmalloc(n, gfp);
236 		if (rctx->ext)
237 			subreq->cryptlen = n;
238 	}
239 
240 	rctx->src = req->src;
241 	rctx->dst = req->dst;
242 	rctx->left = req->cryptlen;
243 
244 	/* calculate first value of T */
245 	crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
246 
247 	return 0;
248 }
249 
250 static void exit_crypt(struct skcipher_request *req)
251 {
252 	struct rctx *rctx = skcipher_request_ctx(req);
253 
254 	rctx->left = 0;
255 
256 	if (rctx->ext)
257 		kzfree(rctx->ext);
258 }
259 
260 static int do_encrypt(struct skcipher_request *req, int err)
261 {
262 	struct rctx *rctx = skcipher_request_ctx(req);
263 	struct skcipher_request *subreq;
264 
265 	subreq = &rctx->subreq;
266 
267 	while (!err && rctx->left) {
268 		err = pre_crypt(req) ?:
269 		      crypto_skcipher_encrypt(subreq) ?:
270 		      post_crypt(req);
271 
272 		if (err == -EINPROGRESS || err == -EBUSY)
273 			return err;
274 	}
275 
276 	exit_crypt(req);
277 	return err;
278 }
279 
280 static void encrypt_done(struct crypto_async_request *areq, int err)
281 {
282 	struct skcipher_request *req = areq->data;
283 	struct skcipher_request *subreq;
284 	struct rctx *rctx;
285 
286 	rctx = skcipher_request_ctx(req);
287 
288 	if (err == -EINPROGRESS) {
289 		if (rctx->left != req->cryptlen)
290 			return;
291 		goto out;
292 	}
293 
294 	subreq = &rctx->subreq;
295 	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
296 
297 	err = do_encrypt(req, err ?: post_crypt(req));
298 	if (rctx->left)
299 		return;
300 
301 out:
302 	skcipher_request_complete(req, err);
303 }
304 
305 static int encrypt(struct skcipher_request *req)
306 {
307 	return do_encrypt(req, init_crypt(req, encrypt_done));
308 }
309 
310 static int do_decrypt(struct skcipher_request *req, int err)
311 {
312 	struct rctx *rctx = skcipher_request_ctx(req);
313 	struct skcipher_request *subreq;
314 
315 	subreq = &rctx->subreq;
316 
317 	while (!err && rctx->left) {
318 		err = pre_crypt(req) ?:
319 		      crypto_skcipher_decrypt(subreq) ?:
320 		      post_crypt(req);
321 
322 		if (err == -EINPROGRESS || err == -EBUSY)
323 			return err;
324 	}
325 
326 	exit_crypt(req);
327 	return err;
328 }
329 
330 static void decrypt_done(struct crypto_async_request *areq, int err)
331 {
332 	struct skcipher_request *req = areq->data;
333 	struct skcipher_request *subreq;
334 	struct rctx *rctx;
335 
336 	rctx = skcipher_request_ctx(req);
337 
338 	if (err == -EINPROGRESS) {
339 		if (rctx->left != req->cryptlen)
340 			return;
341 		goto out;
342 	}
343 
344 	subreq = &rctx->subreq;
345 	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
346 
347 	err = do_decrypt(req, err ?: post_crypt(req));
348 	if (rctx->left)
349 		return;
350 
351 out:
352 	skcipher_request_complete(req, err);
353 }
354 
355 static int decrypt(struct skcipher_request *req)
356 {
357 	return do_decrypt(req, init_crypt(req, decrypt_done));
358 }
359 
360 static int init_tfm(struct crypto_skcipher *tfm)
361 {
362 	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
363 	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
364 	struct priv *ctx = crypto_skcipher_ctx(tfm);
365 	struct crypto_skcipher *child;
366 	struct crypto_cipher *tweak;
367 
368 	child = crypto_spawn_skcipher(&ictx->spawn);
369 	if (IS_ERR(child))
370 		return PTR_ERR(child);
371 
372 	ctx->child = child;
373 
374 	tweak = crypto_alloc_cipher(ictx->name, 0, 0);
375 	if (IS_ERR(tweak)) {
376 		crypto_free_skcipher(ctx->child);
377 		return PTR_ERR(tweak);
378 	}
379 
380 	ctx->tweak = tweak;
381 
382 	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
383 					 sizeof(struct rctx));
384 
385 	return 0;
386 }
387 
388 static void exit_tfm(struct crypto_skcipher *tfm)
389 {
390 	struct priv *ctx = crypto_skcipher_ctx(tfm);
391 
392 	crypto_free_skcipher(ctx->child);
393 	crypto_free_cipher(ctx->tweak);
394 }
395 
396 static void free(struct skcipher_instance *inst)
397 {
398 	crypto_drop_skcipher(skcipher_instance_ctx(inst));
399 	kfree(inst);
400 }
401 
402 static int create(struct crypto_template *tmpl, struct rtattr **tb)
403 {
404 	struct skcipher_instance *inst;
405 	struct crypto_attr_type *algt;
406 	struct xts_instance_ctx *ctx;
407 	struct skcipher_alg *alg;
408 	const char *cipher_name;
409 	u32 mask;
410 	int err;
411 
412 	algt = crypto_get_attr_type(tb);
413 	if (IS_ERR(algt))
414 		return PTR_ERR(algt);
415 
416 	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
417 		return -EINVAL;
418 
419 	cipher_name = crypto_attr_alg_name(tb[1]);
420 	if (IS_ERR(cipher_name))
421 		return PTR_ERR(cipher_name);
422 
423 	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
424 	if (!inst)
425 		return -ENOMEM;
426 
427 	ctx = skcipher_instance_ctx(inst);
428 
429 	crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));
430 
431 	mask = crypto_requires_off(algt->type, algt->mask,
432 				   CRYPTO_ALG_NEED_FALLBACK |
433 				   CRYPTO_ALG_ASYNC);
434 
435 	err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);
436 	if (err == -ENOENT) {
437 		err = -ENAMETOOLONG;
438 		if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
439 			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
440 			goto err_free_inst;
441 
442 		err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);
443 	}
444 
445 	if (err)
446 		goto err_free_inst;
447 
448 	alg = crypto_skcipher_spawn_alg(&ctx->spawn);
449 
450 	err = -EINVAL;
451 	if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
452 		goto err_drop_spawn;
453 
454 	if (crypto_skcipher_alg_ivsize(alg))
455 		goto err_drop_spawn;
456 
457 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
458 				  &alg->base);
459 	if (err)
460 		goto err_drop_spawn;
461 
462 	err = -EINVAL;
463 	cipher_name = alg->base.cra_name;
464 
465 	/* Alas we screwed up the naming so we have to mangle the
466 	 * cipher name.
467 	 */
468 	if (!strncmp(cipher_name, "ecb(", 4)) {
469 		unsigned len;
470 
471 		len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
472 		if (len < 2 || len >= sizeof(ctx->name))
473 			goto err_drop_spawn;
474 
475 		if (ctx->name[len - 1] != ')')
476 			goto err_drop_spawn;
477 
478 		ctx->name[len - 1] = 0;
479 
480 		if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
481 			     "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
482 			err = -ENAMETOOLONG;
483 			goto err_drop_spawn;
484 		}
485 	} else
486 		goto err_drop_spawn;
487 
488 	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
489 	inst->alg.base.cra_priority = alg->base.cra_priority;
490 	inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
491 	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
492 				       (__alignof__(u64) - 1);
493 
494 	inst->alg.ivsize = XTS_BLOCK_SIZE;
495 	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
496 	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
497 
498 	inst->alg.base.cra_ctxsize = sizeof(struct priv);
499 
500 	inst->alg.init = init_tfm;
501 	inst->alg.exit = exit_tfm;
502 
503 	inst->alg.setkey = setkey;
504 	inst->alg.encrypt = encrypt;
505 	inst->alg.decrypt = decrypt;
506 
507 	inst->free = free;
508 
509 	err = skcipher_register_instance(tmpl, inst);
510 	if (err)
511 		goto err_drop_spawn;
512 
513 out:
514 	return err;
515 
516 err_drop_spawn:
517 	crypto_drop_skcipher(&ctx->spawn);
518 err_free_inst:
519 	kfree(inst);
520 	goto out;
521 }
522 
523 static struct crypto_template crypto_tmpl = {
524 	.name = "xts",
525 	.create = create,
526 	.module = THIS_MODULE,
527 };
528 
529 static int __init crypto_module_init(void)
530 {
531 	return crypto_register_template(&crypto_tmpl);
532 }
533 
534 static void __exit crypto_module_exit(void)
535 {
536 	crypto_unregister_template(&crypto_tmpl);
537 }
538 
539 module_init(crypto_module_init);
540 module_exit(crypto_module_exit);
541 
542 MODULE_LICENSE("GPL");
543 MODULE_DESCRIPTION("XTS block cipher mode");
544 MODULE_ALIAS_CRYPTO("xts");
545