GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libcrypto/bn/bn_mont.c Lines: 144 160 90.0 %
Date: 2017-11-07 Branches: 78 113 69.0 %

Line Branch Exec Source
1
/* $OpenBSD: bn_mont.c,v 1.26 2017/01/21 11:00:46 beck Exp $ */
2
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3
 * All rights reserved.
4
 *
5
 * This package is an SSL implementation written
6
 * by Eric Young (eay@cryptsoft.com).
7
 * The implementation was written so as to conform with Netscapes SSL.
8
 *
9
 * This library is free for commercial and non-commercial use as long as
10
 * the following conditions are aheared to.  The following conditions
11
 * apply to all code found in this distribution, be it the RC4, RSA,
12
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13
 * included with this distribution is covered by the same copyright terms
14
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15
 *
16
 * Copyright remains Eric Young's, and as such any Copyright notices in
17
 * the code are not to be removed.
18
 * If this package is used in a product, Eric Young should be given attribution
19
 * as the author of the parts of the library used.
20
 * This can be in the form of a textual message at program startup or
21
 * in documentation (online or textual) provided with the package.
22
 *
23
 * Redistribution and use in source and binary forms, with or without
24
 * modification, are permitted provided that the following conditions
25
 * are met:
26
 * 1. Redistributions of source code must retain the copyright
27
 *    notice, this list of conditions and the following disclaimer.
28
 * 2. Redistributions in binary form must reproduce the above copyright
29
 *    notice, this list of conditions and the following disclaimer in the
30
 *    documentation and/or other materials provided with the distribution.
31
 * 3. All advertising materials mentioning features or use of this software
32
 *    must display the following acknowledgement:
33
 *    "This product includes cryptographic software written by
34
 *     Eric Young (eay@cryptsoft.com)"
35
 *    The word 'cryptographic' can be left out if the rouines from the library
36
 *    being used are not cryptographic related :-).
37
 * 4. If you include any Windows specific code (or a derivative thereof) from
38
 *    the apps directory (application code) you must include an acknowledgement:
39
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40
 *
41
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51
 * SUCH DAMAGE.
52
 *
53
 * The licence and distribution terms for any publically available version or
54
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55
 * copied and put under another distribution licence
56
 * [including the GNU Public Licence.]
57
 */
58
/* ====================================================================
59
 * Copyright (c) 1998-2006 The OpenSSL Project.  All rights reserved.
60
 *
61
 * Redistribution and use in source and binary forms, with or without
62
 * modification, are permitted provided that the following conditions
63
 * are met:
64
 *
65
 * 1. Redistributions of source code must retain the above copyright
66
 *    notice, this list of conditions and the following disclaimer.
67
 *
68
 * 2. Redistributions in binary form must reproduce the above copyright
69
 *    notice, this list of conditions and the following disclaimer in
70
 *    the documentation and/or other materials provided with the
71
 *    distribution.
72
 *
73
 * 3. All advertising materials mentioning features or use of this
74
 *    software must display the following acknowledgment:
75
 *    "This product includes software developed by the OpenSSL Project
76
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
77
 *
78
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
79
 *    endorse or promote products derived from this software without
80
 *    prior written permission. For written permission, please contact
81
 *    openssl-core@openssl.org.
82
 *
83
 * 5. Products derived from this software may not be called "OpenSSL"
84
 *    nor may "OpenSSL" appear in their names without prior written
85
 *    permission of the OpenSSL Project.
86
 *
87
 * 6. Redistributions of any form whatsoever must retain the following
88
 *    acknowledgment:
89
 *    "This product includes software developed by the OpenSSL Project
90
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
91
 *
92
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
93
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
94
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
95
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
96
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
97
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
98
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
99
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
100
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
101
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
102
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
103
 * OF THE POSSIBILITY OF SUCH DAMAGE.
104
 * ====================================================================
105
 *
106
 * This product includes cryptographic software written by Eric Young
107
 * (eay@cryptsoft.com).  This product includes software written by Tim
108
 * Hudson (tjh@cryptsoft.com).
109
 *
110
 */
111
112
/*
113
 * Details about Montgomery multiplication algorithms can be found at
114
 * http://security.ece.orst.edu/publications.html, e.g.
115
 * http://security.ece.orst.edu/koc/papers/j37acmon.pdf and
116
 * sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf
117
 */
118
119
#include <stdio.h>
120
#include <stdint.h>
121
122
#include "bn_lcl.h"
123
124
#define MONT_WORD /* use the faster word-based algorithm */
125
126
#ifdef MONT_WORD
127
static int BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont);
128
#endif
129
130
int
131
BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
132
    BN_MONT_CTX *mont, BN_CTX *ctx)
133
{
134
	BIGNUM *tmp;
135
	int ret = 0;
136
#if defined(OPENSSL_BN_ASM_MONT) && defined(MONT_WORD)
137
110359454
	int num = mont->N.top;
138
139

162008883
	if (num > 1 && a->top == num && b->top == num) {
140

106223801
		if (bn_wexpand(r, num) == NULL)
141
			return (0);
142
53062674
		if (bn_mul_mont(r->d, a->d, b->d, mont->N.d, mont->n0, num)) {
143
53062674
			r->neg = a->neg^b->neg;
144
53062674
			r->top = num;
145

265392498
			bn_correct_top(r);
146
53062674
			return (1);
147
		}
148
	}
149
#endif
150
151
2117053
	BN_CTX_start(ctx);
152
2117053
	if ((tmp = BN_CTX_get(ctx)) == NULL)
153
		goto err;
154
155
	bn_check_top(tmp);
156
2117053
	if (a == b) {
157
1189223
		if (!BN_sqr(tmp, a, ctx))
158
			goto err;
159
	} else {
160
927830
		if (!BN_mul(tmp, a,b, ctx))
161
			goto err;
162
	}
163
	/* reduce from aRR to aR */
164
#ifdef MONT_WORD
165
2117053
	if (!BN_from_montgomery_word(r, tmp, mont))
166
		goto err;
167
#else
168
	if (!BN_from_montgomery(r, tmp, mont, ctx))
169
		goto err;
170
#endif
171
	bn_check_top(r);
172
2117053
	ret = 1;
173
err:
174
2117053
	BN_CTX_end(ctx);
175
2117053
	return (ret);
176
55179727
}
177
178
#ifdef MONT_WORD
179
static int
180
BN_from_montgomery_word(BIGNUM *ret, BIGNUM *r, BN_MONT_CTX *mont)
181
{
182
	BIGNUM *n;
183
	BN_ULONG *ap, *np, *rp, n0, v, carry;
184
	int nl, max, i;
185
186
5181786
	n = &(mont->N);
187
2590893
	nl = n->top;
188
2590893
	if (nl == 0) {
189
		ret->top = 0;
190
		return (1);
191
	}
192
193
2590893
	max = (2 * nl); /* carry is stored separately */
194

5545396
	if (bn_wexpand(r, max) == NULL)
195
		return (0);
196
197
2590893
	r->neg ^= n->neg;
198
2590893
	np = n->d;
199
2590893
	rp = r->d;
200
201
	/* clear the top words of T */
202
#if 1
203
61833816
	for (i=r->top; i<max; i++) /* memset? XXX */
204
28326015
		rp[i] = 0;
205
#else
206
	memset(&(rp[r->top]), 0, (max - r->top) * sizeof(BN_ULONG));
207
#endif
208
209
2590893
	r->top = max;
210
2590893
	n0 = mont->n0[0];
211
212
#ifdef BN_COUNT
213
	fprintf(stderr, "word BN_from_montgomery_word %d * %d\n", nl, nl);
214
#endif
215
62687520
	for (carry = 0, i = 0; i < nl; i++, rp++) {
216
28752867
		v = bn_mul_add_words(rp, np, nl, (rp[0] * n0) & BN_MASK2);
217
28752867
		v = (v + carry + rp[nl]) & BN_MASK2;
218
28752867
		carry |= (v != rp[nl]);
219
28752867
		carry &= (v <= rp[nl]);
220
28752867
		rp[nl] = v;
221
	}
222
223

5567387
	if (bn_wexpand(ret, nl) == NULL)
224
		return (0);
225
2590893
	ret->top = nl;
226
2590893
	ret->neg = r->neg;
227
228
2590893
	rp = ret->d;
229
2590893
	ap = &(r->d[nl]);
230
231
#define BRANCH_FREE 1
232
#if BRANCH_FREE
233
	{
234
		BN_ULONG *nrp;
235
		size_t m;
236
237
2590893
		v = bn_sub_words(rp, ap, np, nl) - carry;
238
		/* if subtraction result is real, then
239
		 * trick unconditional memcpy below to perform in-place
240
		 * "refresh" instead of actual copy. */
241
2590893
		m = (0 - (size_t)v);
242
2590893
		nrp = (BN_ULONG *)(((uintptr_t)rp & ~m)|((uintptr_t)ap & m));
243
244
16708062
		for (i = 0, nl -= 4; i < nl; i += 4) {
245
			BN_ULONG t1, t2, t3, t4;
246
247
5763138
			t1 = nrp[i + 0];
248
5763138
			t2 = nrp[i + 1];
249
5763138
			t3 = nrp[i + 2];
250
5763138
			ap[i + 0] = 0;
251
5763138
			t4 = nrp[i + 3];
252
5763138
			ap[i + 1] = 0;
253
5763138
			rp[i + 0] = t1;
254
5763138
			ap[i + 2] = 0;
255
5763138
			rp[i + 1] = t2;
256
5763138
			ap[i + 3] = 0;
257
5763138
			rp[i + 2] = t3;
258
5763138
			rp[i + 3] = t4;
259
		}
260
16582416
		for (nl += 4; i < nl; i++)
261
5700315
			rp[i] = nrp[i], ap[i] = 0;
262
	}
263
#else
264
	if (bn_sub_words (rp, ap, np, nl) - carry)
265
		memcpy(rp, ap, nl*sizeof(BN_ULONG));
266
#endif
267

182880774
	bn_correct_top(r);
268

13952835
	bn_correct_top(ret);
269
	bn_check_top(ret);
270
271
2590893
	return (1);
272
2590893
}
273
#endif	/* MONT_WORD */
274
275
int
276
BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, BN_CTX *ctx)
277
{
278
	int retn = 0;
279
#ifdef MONT_WORD
280
	BIGNUM *t;
281
282
947680
	BN_CTX_start(ctx);
283

947680
	if ((t = BN_CTX_get(ctx)) && BN_copy(t, a))
284
473840
		retn = BN_from_montgomery_word(ret, t, mont);
285
473840
	BN_CTX_end(ctx);
286
#else /* !MONT_WORD */
287
	BIGNUM *t1, *t2;
288
289
	BN_CTX_start(ctx);
290
	if ((t1 = BN_CTX_get(ctx)) == NULL)
291
		goto err;
292
	if ((t2 = BN_CTX_get(ctx)) == NULL)
293
		goto err;
294
295
	if (!BN_copy(t1, a))
296
		goto err;
297
	BN_mask_bits(t1, mont->ri);
298
299
	if (!BN_mul(t2, t1, &mont->Ni, ctx))
300
		goto err;
301
	BN_mask_bits(t2, mont->ri);
302
303
	if (!BN_mul(t1, t2, &mont->N, ctx))
304
		goto err;
305
	if (!BN_add(t2, a, t1))
306
		goto err;
307
	if (!BN_rshift(ret, t2, mont->ri))
308
		goto err;
309
310
	if (BN_ucmp(ret, &(mont->N)) >= 0) {
311
		if (!BN_usub(ret, ret, &(mont->N)))
312
			goto err;
313
	}
314
	retn = 1;
315
	bn_check_top(ret);
316
317
err:
318
	BN_CTX_end(ctx);
319
#endif /* MONT_WORD */
320
473840
	return (retn);
321
}
322
323
BN_MONT_CTX *
324
BN_MONT_CTX_new(void)
325
{
326
	BN_MONT_CTX *ret;
327
328
87812
	if ((ret = malloc(sizeof(BN_MONT_CTX))) == NULL)
329
		return (NULL);
330
331
43906
	BN_MONT_CTX_init(ret);
332
43906
	ret->flags = BN_FLG_MALLOCED;
333
43906
	return (ret);
334
43906
}
335
336
void
337
BN_MONT_CTX_init(BN_MONT_CTX *ctx)
338
{
339
87812
	ctx->ri = 0;
340
43906
	BN_init(&(ctx->RR));
341
43906
	BN_init(&(ctx->N));
342
43906
	BN_init(&(ctx->Ni));
343
43906
	ctx->n0[0] = ctx->n0[1] = 0;
344
43906
	ctx->flags = 0;
345
43906
}
346
347
void
348
BN_MONT_CTX_free(BN_MONT_CTX *mont)
349
{
350
115234
	if (mont == NULL)
351
		return;
352
353
43881
	BN_clear_free(&(mont->RR));
354
43881
	BN_clear_free(&(mont->N));
355
43881
	BN_clear_free(&(mont->Ni));
356
43881
	if (mont->flags & BN_FLG_MALLOCED)
357
43881
		free(mont);
358
57617
}
359
360
int
361
BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod, BN_CTX *ctx)
362
{
363
	int ret = 0;
364
	BIGNUM *Ri, *R;
365
366
82296
	BN_CTX_start(ctx);
367
41148
	if ((Ri = BN_CTX_get(ctx)) == NULL)
368
		goto err;
369
41148
	R = &(mont->RR);				/* grab RR as a temp */
370
41148
	if (!BN_copy(&(mont->N), mod))
371
		 goto err;				/* Set N */
372
41148
	mont->N.neg = 0;
373
374
#ifdef MONT_WORD
375
	{
376
41148
		BIGNUM tmod;
377
41148
		BN_ULONG buf[2];
378
379
41148
		BN_init(&tmod);
380
41148
		tmod.d = buf;
381
41148
		tmod.dmax = 2;
382
41148
		tmod.neg = 0;
383
384
82296
		mont->ri = (BN_num_bits(mod) +
385
41148
		    (BN_BITS2 - 1)) / BN_BITS2 * BN_BITS2;
386
387
#if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)
388
		/* Only certain BN_BITS2<=32 platforms actually make use of
389
		 * n0[1], and we could use the #else case (with a shorter R
390
		 * value) for the others.  However, currently only the assembler
391
		 * files do know which is which. */
392
393
		BN_zero(R);
394
		if (!(BN_set_bit(R, 2 * BN_BITS2)))
395
			goto err;
396
397
		tmod.top = 0;
398
		if ((buf[0] = mod->d[0]))
399
			tmod.top = 1;
400
		if ((buf[1] = mod->top > 1 ? mod->d[1] : 0))
401
			tmod.top = 2;
402
403
		if ((BN_mod_inverse_ct(Ri, R, &tmod, ctx)) == NULL)
404
			goto err;
405
		if (!BN_lshift(Ri, Ri, 2 * BN_BITS2))
406
			goto err; /* R*Ri */
407
		if (!BN_is_zero(Ri)) {
408
			if (!BN_sub_word(Ri, 1))
409
				goto err;
410
		}
411
		else /* if N mod word size == 1 */
412
		{
413
			if (bn_expand(Ri, (int)sizeof(BN_ULONG) * 2) == NULL)
414
				goto err;
415
			/* Ri-- (mod double word size) */
416
			Ri->neg = 0;
417
			Ri->d[0] = BN_MASK2;
418
			Ri->d[1] = BN_MASK2;
419
			Ri->top = 2;
420
		}
421
		if (!BN_div_ct(Ri, NULL, Ri, &tmod, ctx))
422
			goto err;
423
		/* Ni = (R*Ri-1)/N,
424
		 * keep only couple of least significant words: */
425
		mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
426
		mont->n0[1] = (Ri->top > 1) ? Ri->d[1] : 0;
427
#else
428
41148
		BN_zero(R);
429
41148
		if (!(BN_set_bit(R, BN_BITS2)))
430
			goto err;	/* R */
431
432
41148
		buf[0] = mod->d[0]; /* tmod = N mod word size */
433
41148
		buf[1] = 0;
434
41148
		tmod.top = buf[0] != 0 ? 1 : 0;
435
		/* Ri = R^-1 mod N*/
436
41148
		if ((BN_mod_inverse_ct(Ri, R, &tmod, ctx)) == NULL)
437
12
			goto err;
438
41136
		if (!BN_lshift(Ri, Ri, BN_BITS2))
439
			goto err; /* R*Ri */
440
41136
		if (!BN_is_zero(Ri)) {
441
41033
			if (!BN_sub_word(Ri, 1))
442
				goto err;
443
		}
444
		else /* if N mod word size == 1 */
445
		{
446
103
			if (!BN_set_word(Ri, BN_MASK2))
447
				goto err;  /* Ri-- (mod word size) */
448
		}
449
41136
		if (!BN_div_ct(Ri, NULL, Ri, &tmod, ctx))
450
			goto err;
451
		/* Ni = (R*Ri-1)/N,
452
		 * keep only least significant word: */
453
123408
		mont->n0[0] = (Ri->top > 0) ? Ri->d[0] : 0;
454
41136
		mont->n0[1] = 0;
455
#endif
456
164568
	}
457
#else /* !MONT_WORD */
458
	{ /* bignum version */
459
		mont->ri = BN_num_bits(&mont->N);
460
		BN_zero(R);
461
		if (!BN_set_bit(R, mont->ri))
462
			goto err;  /* R = 2^ri */
463
		/* Ri = R^-1 mod N*/
464
		if ((BN_mod_inverse_ct(Ri, R, &mont->N, ctx)) == NULL)
465
			goto err;
466
		if (!BN_lshift(Ri, Ri, mont->ri))
467
			goto err; /* R*Ri */
468
		if (!BN_sub_word(Ri, 1))
469
			goto err;
470
		/* Ni = (R*Ri-1) / N */
471
		if (!BN_div_ct(&(mont->Ni), NULL, Ri, &mont->N, ctx))
472
			goto err;
473
	}
474
#endif
475
476
	/* setup RR for conversions */
477
41136
	BN_zero(&(mont->RR));
478
41136
	if (!BN_set_bit(&(mont->RR), mont->ri*2))
479
		goto err;
480
41136
	if (!BN_mod_ct(&(mont->RR), &(mont->RR), &(mont->N), ctx))
481
		goto err;
482
483
41136
	ret = 1;
484
485
err:
486
41148
	BN_CTX_end(ctx);
487
41148
	return ret;
488
41148
}
489
490
BN_MONT_CTX *
491
BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from)
492
{
493
5612
	if (to == from)
494
		return (to);
495
496
2806
	if (!BN_copy(&(to->RR), &(from->RR)))
497
		return NULL;
498
2806
	if (!BN_copy(&(to->N), &(from->N)))
499
		return NULL;
500
2806
	if (!BN_copy(&(to->Ni), &(from->Ni)))
501
		return NULL;
502
2806
	to->ri = from->ri;
503
2806
	to->n0[0] = from->n0[0];
504
2806
	to->n0[1] = from->n0[1];
505
2806
	return (to);
506
2806
}
507
508
BN_MONT_CTX *
509
BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, int lock, const BIGNUM *mod,
510
    BN_CTX *ctx)
511
{
512
	int got_write_lock = 0;
513
	BN_MONT_CTX *ret;
514
515
847456
	CRYPTO_r_lock(lock);
516
423728
	if (!*pmont) {
517
2931
		CRYPTO_r_unlock(lock);
518
2931
		CRYPTO_w_lock(lock);
519
		got_write_lock = 1;
520
521
2931
		if (!*pmont) {
522
2931
			ret = BN_MONT_CTX_new();
523

5862
			if (ret && !BN_MONT_CTX_set(ret, mod, ctx))
524
				BN_MONT_CTX_free(ret);
525
			else
526
2931
				*pmont = ret;
527
		}
528
	}
529
530
423728
	ret = *pmont;
531
532
423728
	if (got_write_lock)
533
2931
		CRYPTO_w_unlock(lock);
534
	else
535
420797
		CRYPTO_r_unlock(lock);
536
537
423728
	return ret;
538
}