Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
/* XTS: as defined in IEEE1619/D16
 *	http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
 *	(sector sizes which are not a multiple of 16 bytes are,
 *	however currently unsupported)
 *
 * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
 *
 * Based on ecb.c
 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 */
#include <crypto/internal/skcipher.h>
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>

#include <crypto/xts.h>
#include <crypto/b128ops.h>
#include <crypto/gf128mul.h>

#define XTS_BUFFER_SIZE 128u

struct priv {
	struct crypto_skcipher *child;
	struct crypto_cipher *tweak;
};

struct xts_instance_ctx {
	struct crypto_skcipher_spawn spawn;
	char name[CRYPTO_MAX_ALG_NAME];
};

struct rctx {
	le128 buf[XTS_BUFFER_SIZE / sizeof(le128)];

	le128 t;

	le128 *ext;

	struct scatterlist srcbuf[2];
	struct scatterlist dstbuf[2];
	struct scatterlist *src;
	struct scatterlist *dst;

	unsigned int left;

	struct skcipher_request subreq;
};

static int setkey(struct crypto_skcipher *parent, const u8 *key,
		  unsigned int keylen)
{
	struct priv *ctx = crypto_skcipher_ctx(parent);
	struct crypto_skcipher *child;
	struct crypto_cipher *tweak;
	int err;

	err = xts_verify_key(parent, key, keylen);
	if (err)
		return err;

	keylen /= 2;

	/* we need two cipher instances: one to compute the initial 'tweak'
	 * by encrypting the IV (usually the 'plain' iv) and the other
	 * one to encrypt and decrypt the data */

	/* tweak cipher, uses Key2 i.e. the second half of *key */
	tweak = ctx->tweak;
	crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
	crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
				       CRYPTO_TFM_REQ_MASK);
	err = crypto_cipher_setkey(tweak, key + keylen, keylen);
	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
					  CRYPTO_TFM_RES_MASK);
	if (err)
		return err;

	/* data cipher, uses Key1 i.e. the first half of *key */
	child = ctx->child;
	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 int post_crypt(struct skcipher_request *req)
{
	struct rctx *rctx = skcipher_request_ctx(req);
	le128 *buf = rctx->ext ?: rctx->buf;
	struct skcipher_request *subreq;
	const int bs = XTS_BLOCK_SIZE;
	struct skcipher_walk w;
	struct scatterlist *sg;
	unsigned offset;
	int err;

	subreq = &rctx->subreq;
	err = skcipher_walk_virt(&w, subreq, false);

	while (w.nbytes) {
		unsigned int avail = w.nbytes;
		le128 *wdst;

		wdst = w.dst.virt.addr;

		do {
			le128_xor(wdst, buf++, wdst);
			wdst++;
		} while ((avail -= bs) >= bs);

		err = skcipher_walk_done(&w, avail);
	}

	rctx->left -= subreq->cryptlen;

	if (err || !rctx->left)
		goto out;

	rctx->dst = rctx->dstbuf;

	scatterwalk_done(&w.out, 0, 1);
	sg = w.out.sg;
	offset = w.out.offset;

	if (rctx->dst != sg) {
		rctx->dst[0] = *sg;
		sg_unmark_end(rctx->dst);
		scatterwalk_crypto_chain(rctx->dst, sg_next(sg), 0, 2);
	}
	rctx->dst[0].length -= offset - sg->offset;
	rctx->dst[0].offset = offset;

out:
	return err;
}

static int pre_crypt(struct skcipher_request *req)
{
	struct rctx *rctx = skcipher_request_ctx(req);
	le128 *buf = rctx->ext ?: rctx->buf;
	struct skcipher_request *subreq;
	const int bs = XTS_BLOCK_SIZE;
	struct skcipher_walk w;
	struct scatterlist *sg;
	unsigned cryptlen;
	unsigned offset;
	bool more;
	int err;

	subreq = &rctx->subreq;
	cryptlen = subreq->cryptlen;

	more = rctx->left > cryptlen;
	if (!more)
		cryptlen = rctx->left;

	skcipher_request_set_crypt(subreq, rctx->src, rctx->dst,
				   cryptlen, NULL);

	err = skcipher_walk_virt(&w, subreq, false);

	while (w.nbytes) {
		unsigned int avail = w.nbytes;
		le128 *wsrc;
		le128 *wdst;

		wsrc = w.src.virt.addr;
		wdst = w.dst.virt.addr;

		do {
			*buf++ = rctx->t;
			le128_xor(wdst++, &rctx->t, wsrc++);
			gf128mul_x_ble(&rctx->t, &rctx->t);
		} while ((avail -= bs) >= bs);

		err = skcipher_walk_done(&w, avail);
	}

	skcipher_request_set_crypt(subreq, rctx->dst, rctx->dst,
				   cryptlen, NULL);

	if (err || !more)
		goto out;

	rctx->src = rctx->srcbuf;

	scatterwalk_done(&w.in, 0, 1);
	sg = w.in.sg;
	offset = w.in.offset;

	if (rctx->src != sg) {
		rctx->src[0] = *sg;
		sg_unmark_end(rctx->src);
		scatterwalk_crypto_chain(rctx->src, sg_next(sg), 0, 2);
	}
	rctx->src[0].length -= offset - sg->offset;
	rctx->src[0].offset = offset;

out:
	return err;
}

static int init_crypt(struct skcipher_request *req, crypto_completion_t done)
{
	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
	struct rctx *rctx = skcipher_request_ctx(req);
	struct skcipher_request *subreq;
	gfp_t gfp;

	subreq = &rctx->subreq;
	skcipher_request_set_tfm(subreq, ctx->child);
	skcipher_request_set_callback(subreq, req->base.flags, done, req);

	gfp = req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL :
							   GFP_ATOMIC;
	rctx->ext = NULL;

	subreq->cryptlen = XTS_BUFFER_SIZE;
	if (req->cryptlen > XTS_BUFFER_SIZE) {
		unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);

		rctx->ext = kmalloc(n, gfp);
		if (rctx->ext)
			subreq->cryptlen = n;
	}

	rctx->src = req->src;
	rctx->dst = req->dst;
	rctx->left = req->cryptlen;

	/* calculate first value of T */
	crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);

	return 0;
}

static void exit_crypt(struct skcipher_request *req)
{
	struct rctx *rctx = skcipher_request_ctx(req);

	rctx->left = 0;

	if (rctx->ext)
		kzfree(rctx->ext);
}

static int do_encrypt(struct skcipher_request *req, int err)
{
	struct rctx *rctx = skcipher_request_ctx(req);
	struct skcipher_request *subreq;

	subreq = &rctx->subreq;

	while (!err && rctx->left) {
		err = pre_crypt(req) ?:
		      crypto_skcipher_encrypt(subreq) ?:
		      post_crypt(req);

		if (err == -EINPROGRESS ||
		    (err == -EBUSY &&
		     req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
			return err;
	}

	exit_crypt(req);
	return err;
}

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

	rctx = skcipher_request_ctx(req);

	if (err == -EINPROGRESS) {
		if (rctx->left != req->cryptlen)
			return;
		goto out;
	}

	subreq = &rctx->subreq;
	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;

	err = do_encrypt(req, err ?: post_crypt(req));
	if (rctx->left)
		return;

out:
	skcipher_request_complete(req, err);
}

static int encrypt(struct skcipher_request *req)
{
	return do_encrypt(req, init_crypt(req, encrypt_done));
}

static int do_decrypt(struct skcipher_request *req, int err)
{
	struct rctx *rctx = skcipher_request_ctx(req);
	struct skcipher_request *subreq;

	subreq = &rctx->subreq;

	while (!err && rctx->left) {
		err = pre_crypt(req) ?:
		      crypto_skcipher_decrypt(subreq) ?:
		      post_crypt(req);

		if (err == -EINPROGRESS ||
		    (err == -EBUSY &&
		     req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
			return err;
	}

	exit_crypt(req);
	return err;
}

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

	rctx = skcipher_request_ctx(req);

	if (err == -EINPROGRESS) {
		if (rctx->left != req->cryptlen)
			return;
		goto out;
	}

	subreq = &rctx->subreq;
	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;

	err = do_decrypt(req, err ?: post_crypt(req));
	if (rctx->left)
		return;

out:
	skcipher_request_complete(req, err);
}

static int decrypt(struct skcipher_request *req)
{
	return do_decrypt(req, init_crypt(req, decrypt_done));
}

int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
	      struct scatterlist *ssrc, unsigned int nbytes,
	      struct xts_crypt_req *req)
{
	const unsigned int bsize = XTS_BLOCK_SIZE;
	const unsigned int max_blks = req->tbuflen / bsize;
	struct blkcipher_walk walk;
	unsigned int nblocks;
	le128 *src, *dst, *t;
	le128 *t_buf = req->tbuf;
	int err, i;

	BUG_ON(max_blks < 1);

	blkcipher_walk_init(&walk, sdst, ssrc, nbytes);

	err = blkcipher_walk_virt(desc, &walk);
	nbytes = walk.nbytes;
	if (!nbytes)
		return err;

	nblocks = min(nbytes / bsize, max_blks);
	src = (le128 *)walk.src.virt.addr;
	dst = (le128 *)walk.dst.virt.addr;

	/* calculate first value of T */
	req->tweak_fn(req->tweak_ctx, (u8 *)&t_buf[0], walk.iv);

	i = 0;
	goto first;

	for (;;) {
		do {
			for (i = 0; i < nblocks; i++) {
				gf128mul_x_ble(&t_buf[i], t);
first:
				t = &t_buf[i];

				/* PP <- T xor P */
				le128_xor(dst + i, t, src + i);
			}

			/* CC <- E(Key2,PP) */
			req->crypt_fn(req->crypt_ctx, (u8 *)dst,
				      nblocks * bsize);

			/* C <- T xor CC */
			for (i = 0; i < nblocks; i++)
				le128_xor(dst + i, dst + i, &t_buf[i]);

			src += nblocks;
			dst += nblocks;
			nbytes -= nblocks * bsize;
			nblocks = min(nbytes / bsize, max_blks);
		} while (nblocks > 0);

		*(le128 *)walk.iv = *t;

		err = blkcipher_walk_done(desc, &walk, nbytes);
		nbytes = walk.nbytes;
		if (!nbytes)
			break;

		nblocks = min(nbytes / bsize, max_blks);
		src = (le128 *)walk.src.virt.addr;
		dst = (le128 *)walk.dst.virt.addr;
	}

	return err;
}
EXPORT_SYMBOL_GPL(xts_crypt);

static int init_tfm(struct crypto_skcipher *tfm)
{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
	struct priv *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_skcipher *child;
	struct crypto_cipher *tweak;

	child = crypto_spawn_skcipher(&ictx->spawn);
	if (IS_ERR(child))
		return PTR_ERR(child);

	ctx->child = child;

	tweak = crypto_alloc_cipher(ictx->name, 0, 0);
	if (IS_ERR(tweak)) {
		crypto_free_skcipher(ctx->child);
		return PTR_ERR(tweak);
	}

	ctx->tweak = tweak;

	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
					 sizeof(struct rctx));

	return 0;
}

static void exit_tfm(struct crypto_skcipher *tfm)
{
	struct priv *ctx = crypto_skcipher_ctx(tfm);

	crypto_free_skcipher(ctx->child);
	crypto_free_cipher(ctx->tweak);
}

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

static int create(struct crypto_template *tmpl, struct rtattr **tb)
{
	struct skcipher_instance *inst;
	struct crypto_attr_type *algt;
	struct xts_instance_ctx *ctx;
	struct skcipher_alg *alg;
	const char *cipher_name;
	u32 mask;
	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(*ctx), GFP_KERNEL);
	if (!inst)
		return -ENOMEM;

	ctx = skcipher_instance_ctx(inst);

	crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));

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

	err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);
	if (err == -ENOENT) {
		err = -ENAMETOOLONG;
		if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
			goto err_free_inst;

		err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);
	}

	if (err)
		goto err_free_inst;

	alg = crypto_skcipher_spawn_alg(&ctx->spawn);

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

	if (crypto_skcipher_alg_ivsize(alg))
		goto err_drop_spawn;

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

	err = -EINVAL;
	cipher_name = alg->base.cra_name;

	/* Alas we screwed up the naming so we have to mangle the
	 * cipher name.
	 */
	if (!strncmp(cipher_name, "ecb(", 4)) {
		unsigned len;

		len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
		if (len < 2 || len >= sizeof(ctx->name))
			goto err_drop_spawn;

		if (ctx->name[len - 1] != ')')
			goto err_drop_spawn;

		ctx->name[len - 1] = 0;

		if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
			     "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME)
			return -ENAMETOOLONG;
	} else
		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 = XTS_BLOCK_SIZE;
	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
				       (__alignof__(u64) - 1);

	inst->alg.ivsize = XTS_BLOCK_SIZE;
	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;

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

	inst->alg.init = init_tfm;
	inst->alg.exit = exit_tfm;

	inst->alg.setkey = setkey;
	inst->alg.encrypt = encrypt;
	inst->alg.decrypt = decrypt;

	inst->free = free;

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

out:
	return err;

err_drop_spawn:
	crypto_drop_skcipher(&ctx->spawn);
err_free_inst:
	kfree(inst);
	goto out;
}

static struct crypto_template crypto_tmpl = {
	.name = "xts",
	.create = create,
	.module = THIS_MODULE,
};

static int __init crypto_module_init(void)
{
	return crypto_register_template(&crypto_tmpl);
}

static void __exit crypto_module_exit(void)
{
	crypto_unregister_template(&crypto_tmpl);
}

module_init(crypto_module_init);
module_exit(crypto_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("XTS block cipher mode");
MODULE_ALIAS_CRYPTO("xts");