1/*
2 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <assert.h>
11#include <limits.h>
12#include "internal/cryptlib.h"
13#include "bn_local.h"
14#include <openssl/opensslconf.h>
15#include "internal/constant_time.h"
16
17/* This stuff appears to be completely unused, so is deprecated */
18#ifndef OPENSSL_NO_DEPRECATED_0_9_8
19/*-
20 * For a 32 bit machine
21 * 2 - 4 == 128
22 * 3 - 8 == 256
23 * 4 - 16 == 512
24 * 5 - 32 == 1024
25 * 6 - 64 == 2048
26 * 7 - 128 == 4096
27 * 8 - 256 == 8192
28 */
29static int bn_limit_bits = 0;
30static int bn_limit_num = 8; /* (1<<bn_limit_bits) */
31static int bn_limit_bits_low = 0;
32static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */
33static int bn_limit_bits_high = 0;
34static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */
35static int bn_limit_bits_mont = 0;
36static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */
37
38void BN_set_params(int mult, int high, int low, int mont)
39{
40 if (mult >= 0) {
41 if (mult > (int)(sizeof(int) * 8) - 1)
42 mult = sizeof(int) * 8 - 1;
43 bn_limit_bits = mult;
44 bn_limit_num = 1 << mult;
45 }
46 if (high >= 0) {
47 if (high > (int)(sizeof(int) * 8) - 1)
48 high = sizeof(int) * 8 - 1;
49 bn_limit_bits_high = high;
50 bn_limit_num_high = 1 << high;
51 }
52 if (low >= 0) {
53 if (low > (int)(sizeof(int) * 8) - 1)
54 low = sizeof(int) * 8 - 1;
55 bn_limit_bits_low = low;
56 bn_limit_num_low = 1 << low;
57 }
58 if (mont >= 0) {
59 if (mont > (int)(sizeof(int) * 8) - 1)
60 mont = sizeof(int) * 8 - 1;
61 bn_limit_bits_mont = mont;
62 bn_limit_num_mont = 1 << mont;
63 }
64}
65
66int BN_get_params(int which)
67{
68 if (which == 0)
69 return bn_limit_bits;
70 else if (which == 1)
71 return bn_limit_bits_high;
72 else if (which == 2)
73 return bn_limit_bits_low;
74 else if (which == 3)
75 return bn_limit_bits_mont;
76 else
77 return 0;
78}
79#endif
80
81const BIGNUM *BN_value_one(void)
82{
83 static const BN_ULONG data_one = 1L;
84 static const BIGNUM const_one =
85 { (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA };
86
87 return &const_one;
88}
89
90int BN_num_bits_word(BN_ULONG l)
91{
92 BN_ULONG x, mask;
93 int bits = (l != 0);
94
95#if BN_BITS2 > 32
96 x = l >> 32;
97 mask = (0 - x) & BN_MASK2;
98 mask = (0 - (mask >> (BN_BITS2 - 1)));
99 bits += 32 & mask;
100 l ^= (x ^ l) & mask;
101#endif
102
103 x = l >> 16;
104 mask = (0 - x) & BN_MASK2;
105 mask = (0 - (mask >> (BN_BITS2 - 1)));
106 bits += 16 & mask;
107 l ^= (x ^ l) & mask;
108
109 x = l >> 8;
110 mask = (0 - x) & BN_MASK2;
111 mask = (0 - (mask >> (BN_BITS2 - 1)));
112 bits += 8 & mask;
113 l ^= (x ^ l) & mask;
114
115 x = l >> 4;
116 mask = (0 - x) & BN_MASK2;
117 mask = (0 - (mask >> (BN_BITS2 - 1)));
118 bits += 4 & mask;
119 l ^= (x ^ l) & mask;
120
121 x = l >> 2;
122 mask = (0 - x) & BN_MASK2;
123 mask = (0 - (mask >> (BN_BITS2 - 1)));
124 bits += 2 & mask;
125 l ^= (x ^ l) & mask;
126
127 x = l >> 1;
128 mask = (0 - x) & BN_MASK2;
129 mask = (0 - (mask >> (BN_BITS2 - 1)));
130 bits += 1 & mask;
131
132 return bits;
133}
134
135/*
136 * This function still leaks `a->dmax`: it's caller's responsibility to
137 * expand the input `a` in advance to a public length.
138 */
139static ossl_inline
140int bn_num_bits_consttime(const BIGNUM *a)
141{
142 int j, ret;
143 unsigned int mask, past_i;
144 int i = a->top - 1;
145 bn_check_top(a);
146
147 for (j = 0, past_i = 0, ret = 0; j < a->dmax; j++) {
148 mask = constant_time_eq_int(i, j); /* 0xff..ff if i==j, 0x0 otherwise */
149
150 ret += BN_BITS2 & (~mask & ~past_i);
151 ret += BN_num_bits_word(a->d[j]) & mask;
152
153 past_i |= mask; /* past_i will become 0xff..ff after i==j */
154 }
155
156 /*
157 * if BN_is_zero(a) => i is -1 and ret contains garbage, so we mask the
158 * final result.
159 */
160 mask = ~(constant_time_eq_int(i, ((int)-1)));
161
162 return ret & mask;
163}
164
165int BN_num_bits(const BIGNUM *a)
166{
167 int i = a->top - 1;
168 bn_check_top(a);
169
170 if (a->flags & BN_FLG_CONSTTIME) {
171 /*
172 * We assume that BIGNUMs flagged as CONSTTIME have also been expanded
173 * so that a->dmax is not leaking secret information.
174 *
175 * In other words, it's the caller's responsibility to ensure `a` has
176 * been preallocated in advance to a public length if we hit this
177 * branch.
178 *
179 */
180 return bn_num_bits_consttime(a);
181 }
182
183 if (BN_is_zero(a))
184 return 0;
185
186 return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
187}
188
189static void bn_free_d(BIGNUM *a, int clear)
190{
191 if (BN_get_flags(a, BN_FLG_SECURE))
192 OPENSSL_secure_clear_free(a->d, a->dmax * sizeof(a->d[0]));
193 else if (clear != 0)
194 OPENSSL_clear_free(a->d, a->dmax * sizeof(a->d[0]));
195 else
196 OPENSSL_free(a->d);
197}
198
199
200void BN_clear_free(BIGNUM *a)
201{
202 if (a == NULL)
203 return;
204 if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA))
205 bn_free_d(a, 1);
206 if (BN_get_flags(a, BN_FLG_MALLOCED)) {
207 OPENSSL_cleanse(a, sizeof(*a));
208 OPENSSL_free(a);
209 }
210}
211
212void BN_free(BIGNUM *a)
213{
214 if (a == NULL)
215 return;
216 if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
217 bn_free_d(a, 0);
218 if (a->flags & BN_FLG_MALLOCED)
219 OPENSSL_free(a);
220}
221
222void bn_init(BIGNUM *a)
223{
224 static BIGNUM nilbn;
225
226 *a = nilbn;
227 bn_check_top(a);
228}
229
230BIGNUM *BN_new(void)
231{
232 BIGNUM *ret;
233
234 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
235 BNerr(BN_F_BN_NEW, ERR_R_MALLOC_FAILURE);
236 return NULL;
237 }
238 ret->flags = BN_FLG_MALLOCED;
239 bn_check_top(ret);
240 return ret;
241}
242
243 BIGNUM *BN_secure_new(void)
244 {
245 BIGNUM *ret = BN_new();
246 if (ret != NULL)
247 ret->flags |= BN_FLG_SECURE;
248 return ret;
249 }
250
251/* This is used by bn_expand2() */
252/* The caller MUST check that words > b->dmax before calling this */
253static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
254{
255 BN_ULONG *a = NULL;
256
257 if (words > (INT_MAX / (4 * BN_BITS2))) {
258 BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_BIGNUM_TOO_LONG);
259 return NULL;
260 }
261 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
262 BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
263 return NULL;
264 }
265 if (BN_get_flags(b, BN_FLG_SECURE))
266 a = OPENSSL_secure_zalloc(words * sizeof(*a));
267 else
268 a = OPENSSL_zalloc(words * sizeof(*a));
269 if (a == NULL) {
270 BNerr(BN_F_BN_EXPAND_INTERNAL, ERR_R_MALLOC_FAILURE);
271 return NULL;
272 }
273
274 assert(b->top <= words);
275 if (b->top > 0)
276 memcpy(a, b->d, sizeof(*a) * b->top);
277
278 return a;
279}
280
281/*
282 * This is an internal function that should not be used in applications. It
283 * ensures that 'b' has enough room for a 'words' word number and initialises
284 * any unused part of b->d with leading zeros. It is mostly used by the
285 * various BIGNUM routines. If there is an error, NULL is returned. If not,
286 * 'b' is returned.
287 */
288
289BIGNUM *bn_expand2(BIGNUM *b, int words)
290{
291 if (words > b->dmax) {
292 BN_ULONG *a = bn_expand_internal(b, words);
293 if (!a)
294 return NULL;
295 if (b->d != NULL)
296 bn_free_d(b, 1);
297 b->d = a;
298 b->dmax = words;
299 }
300
301 return b;
302}
303
304BIGNUM *BN_dup(const BIGNUM *a)
305{
306 BIGNUM *t;
307
308 if (a == NULL)
309 return NULL;
310 bn_check_top(a);
311
312 t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
313 if (t == NULL)
314 return NULL;
315 if (!BN_copy(t, a)) {
316 BN_free(t);
317 return NULL;
318 }
319 bn_check_top(t);
320 return t;
321}
322
323BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
324{
325 bn_check_top(b);
326
327 if (a == b)
328 return a;
329 if (bn_wexpand(a, b->top) == NULL)
330 return NULL;
331
332 if (b->top > 0)
333 memcpy(a->d, b->d, sizeof(b->d[0]) * b->top);
334
335 a->neg = b->neg;
336 a->top = b->top;
337 a->flags |= b->flags & BN_FLG_FIXED_TOP;
338 bn_check_top(a);
339 return a;
340}
341
342#define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
343 | BN_FLG_CONSTTIME \
344 | BN_FLG_SECURE \
345 | BN_FLG_FIXED_TOP))
346#define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
347
348void BN_swap(BIGNUM *a, BIGNUM *b)
349{
350 int flags_old_a, flags_old_b;
351 BN_ULONG *tmp_d;
352 int tmp_top, tmp_dmax, tmp_neg;
353
354 bn_check_top(a);
355 bn_check_top(b);
356
357 flags_old_a = a->flags;
358 flags_old_b = b->flags;
359
360 tmp_d = a->d;
361 tmp_top = a->top;
362 tmp_dmax = a->dmax;
363 tmp_neg = a->neg;
364
365 a->d = b->d;
366 a->top = b->top;
367 a->dmax = b->dmax;
368 a->neg = b->neg;
369
370 b->d = tmp_d;
371 b->top = tmp_top;
372 b->dmax = tmp_dmax;
373 b->neg = tmp_neg;
374
375 a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
376 b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
377 bn_check_top(a);
378 bn_check_top(b);
379}
380
381void BN_clear(BIGNUM *a)
382{
383 if (a == NULL)
384 return;
385 bn_check_top(a);
386 if (a->d != NULL)
387 OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
388 a->neg = 0;
389 a->top = 0;
390 a->flags &= ~BN_FLG_FIXED_TOP;
391}
392
393BN_ULONG BN_get_word(const BIGNUM *a)
394{
395 if (a->top > 1)
396 return BN_MASK2;
397 else if (a->top == 1)
398 return a->d[0];
399 /* a->top == 0 */
400 return 0;
401}
402
403int BN_set_word(BIGNUM *a, BN_ULONG w)
404{
405 bn_check_top(a);
406 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
407 return 0;
408 a->neg = 0;
409 a->d[0] = w;
410 a->top = (w ? 1 : 0);
411 a->flags &= ~BN_FLG_FIXED_TOP;
412 bn_check_top(a);
413 return 1;
414}
415
416BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
417{
418 unsigned int i, m;
419 unsigned int n;
420 BN_ULONG l;
421 BIGNUM *bn = NULL;
422
423 if (ret == NULL)
424 ret = bn = BN_new();
425 if (ret == NULL)
426 return NULL;
427 bn_check_top(ret);
428 /* Skip leading zero's. */
429 for ( ; len > 0 && *s == 0; s++, len--)
430 continue;
431 n = len;
432 if (n == 0) {
433 ret->top = 0;
434 return ret;
435 }
436 i = ((n - 1) / BN_BYTES) + 1;
437 m = ((n - 1) % (BN_BYTES));
438 if (bn_wexpand(ret, (int)i) == NULL) {
439 BN_free(bn);
440 return NULL;
441 }
442 ret->top = i;
443 ret->neg = 0;
444 l = 0;
445 while (n--) {
446 l = (l << 8L) | *(s++);
447 if (m-- == 0) {
448 ret->d[--i] = l;
449 l = 0;
450 m = BN_BYTES - 1;
451 }
452 }
453 /*
454 * need to call this due to clear byte at top if avoiding having the top
455 * bit set (-ve number)
456 */
457 bn_correct_top(ret);
458 return ret;
459}
460
461typedef enum {big, little} endianess_t;
462
463/* ignore negative */
464static
465int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen, endianess_t endianess)
466{
467 int n;
468 size_t i, lasti, j, atop, mask;
469 BN_ULONG l;
470
471 /*
472 * In case |a| is fixed-top, BN_num_bytes can return bogus length,
473 * but it's assumed that fixed-top inputs ought to be "nominated"
474 * even for padded output, so it works out...
475 */
476 n = BN_num_bytes(a);
477 if (tolen == -1) {
478 tolen = n;
479 } else if (tolen < n) { /* uncommon/unlike case */
480 BIGNUM temp = *a;
481
482 bn_correct_top(&temp);
483 n = BN_num_bytes(&temp);
484 if (tolen < n)
485 return -1;
486 }
487
488 /* Swipe through whole available data and don't give away padded zero. */
489 atop = a->dmax * BN_BYTES;
490 if (atop == 0) {
491 OPENSSL_cleanse(to, tolen);
492 return tolen;
493 }
494
495 lasti = atop - 1;
496 atop = a->top * BN_BYTES;
497 if (endianess == big)
498 to += tolen; /* start from the end of the buffer */
499 for (i = 0, j = 0; j < (size_t)tolen; j++) {
500 unsigned char val;
501 l = a->d[i / BN_BYTES];
502 mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
503 val = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
504 if (endianess == big)
505 *--to = val;
506 else
507 *to++ = val;
508 i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
509 }
510
511 return tolen;
512}
513
514int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
515{
516 if (tolen < 0)
517 return -1;
518 return bn2binpad(a, to, tolen, big);
519}
520
521int BN_bn2bin(const BIGNUM *a, unsigned char *to)
522{
523 return bn2binpad(a, to, -1, big);
524}
525
526BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
527{
528 unsigned int i, m;
529 unsigned int n;
530 BN_ULONG l;
531 BIGNUM *bn = NULL;
532
533 if (ret == NULL)
534 ret = bn = BN_new();
535 if (ret == NULL)
536 return NULL;
537 bn_check_top(ret);
538 s += len;
539 /* Skip trailing zeroes. */
540 for ( ; len > 0 && s[-1] == 0; s--, len--)
541 continue;
542 n = len;
543 if (n == 0) {
544 ret->top = 0;
545 return ret;
546 }
547 i = ((n - 1) / BN_BYTES) + 1;
548 m = ((n - 1) % (BN_BYTES));
549 if (bn_wexpand(ret, (int)i) == NULL) {
550 BN_free(bn);
551 return NULL;
552 }
553 ret->top = i;
554 ret->neg = 0;
555 l = 0;
556 while (n--) {
557 s--;
558 l = (l << 8L) | *s;
559 if (m-- == 0) {
560 ret->d[--i] = l;
561 l = 0;
562 m = BN_BYTES - 1;
563 }
564 }
565 /*
566 * need to call this due to clear byte at top if avoiding having the top
567 * bit set (-ve number)
568 */
569 bn_correct_top(ret);
570 return ret;
571}
572
573int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
574{
575 if (tolen < 0)
576 return -1;
577 return bn2binpad(a, to, tolen, little);
578}
579
580BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret)
581{
582#ifdef B_ENDIAN
583 return BN_bin2bn(s, len, ret);
584#else
585 return BN_lebin2bn(s, len, ret);
586#endif
587}
588
589int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen)
590{
591#ifdef B_ENDIAN
592 return BN_bn2binpad(a, to, tolen);
593#else
594 return BN_bn2lebinpad(a, to, tolen);
595#endif
596}
597
598int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
599{
600 int i;
601 BN_ULONG t1, t2, *ap, *bp;
602
603 bn_check_top(a);
604 bn_check_top(b);
605
606 i = a->top - b->top;
607 if (i != 0)
608 return i;
609 ap = a->d;
610 bp = b->d;
611 for (i = a->top - 1; i >= 0; i--) {
612 t1 = ap[i];
613 t2 = bp[i];
614 if (t1 != t2)
615 return ((t1 > t2) ? 1 : -1);
616 }
617 return 0;
618}
619
620int BN_cmp(const BIGNUM *a, const BIGNUM *b)
621{
622 int i;
623 int gt, lt;
624 BN_ULONG t1, t2;
625
626 if ((a == NULL) || (b == NULL)) {
627 if (a != NULL)
628 return -1;
629 else if (b != NULL)
630 return 1;
631 else
632 return 0;
633 }
634
635 bn_check_top(a);
636 bn_check_top(b);
637
638 if (a->neg != b->neg) {
639 if (a->neg)
640 return -1;
641 else
642 return 1;
643 }
644 if (a->neg == 0) {
645 gt = 1;
646 lt = -1;
647 } else {
648 gt = -1;
649 lt = 1;
650 }
651
652 if (a->top > b->top)
653 return gt;
654 if (a->top < b->top)
655 return lt;
656 for (i = a->top - 1; i >= 0; i--) {
657 t1 = a->d[i];
658 t2 = b->d[i];
659 if (t1 > t2)
660 return gt;
661 if (t1 < t2)
662 return lt;
663 }
664 return 0;
665}
666
667int BN_set_bit(BIGNUM *a, int n)
668{
669 int i, j, k;
670
671 if (n < 0)
672 return 0;
673
674 i = n / BN_BITS2;
675 j = n % BN_BITS2;
676 if (a->top <= i) {
677 if (bn_wexpand(a, i + 1) == NULL)
678 return 0;
679 for (k = a->top; k < i + 1; k++)
680 a->d[k] = 0;
681 a->top = i + 1;
682 a->flags &= ~BN_FLG_FIXED_TOP;
683 }
684
685 a->d[i] |= (((BN_ULONG)1) << j);
686 bn_check_top(a);
687 return 1;
688}
689
690int BN_clear_bit(BIGNUM *a, int n)
691{
692 int i, j;
693
694 bn_check_top(a);
695 if (n < 0)
696 return 0;
697
698 i = n / BN_BITS2;
699 j = n % BN_BITS2;
700 if (a->top <= i)
701 return 0;
702
703 a->d[i] &= (~(((BN_ULONG)1) << j));
704 bn_correct_top(a);
705 return 1;
706}
707
708int BN_is_bit_set(const BIGNUM *a, int n)
709{
710 int i, j;
711
712 bn_check_top(a);
713 if (n < 0)
714 return 0;
715 i = n / BN_BITS2;
716 j = n % BN_BITS2;
717 if (a->top <= i)
718 return 0;
719 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
720}
721
722int BN_mask_bits(BIGNUM *a, int n)
723{
724 int b, w;
725
726 bn_check_top(a);
727 if (n < 0)
728 return 0;
729
730 w = n / BN_BITS2;
731 b = n % BN_BITS2;
732 if (w >= a->top)
733 return 0;
734 if (b == 0)
735 a->top = w;
736 else {
737 a->top = w + 1;
738 a->d[w] &= ~(BN_MASK2 << b);
739 }
740 bn_correct_top(a);
741 return 1;
742}
743
744void BN_set_negative(BIGNUM *a, int b)
745{
746 if (b && !BN_is_zero(a))
747 a->neg = 1;
748 else
749 a->neg = 0;
750}
751
752int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
753{
754 int i;
755 BN_ULONG aa, bb;
756
757 if (n == 0)
758 return 0;
759
760 aa = a[n - 1];
761 bb = b[n - 1];
762 if (aa != bb)
763 return ((aa > bb) ? 1 : -1);
764 for (i = n - 2; i >= 0; i--) {
765 aa = a[i];
766 bb = b[i];
767 if (aa != bb)
768 return ((aa > bb) ? 1 : -1);
769 }
770 return 0;
771}
772
773/*
774 * Here follows a specialised variants of bn_cmp_words(). It has the
775 * capability of performing the operation on arrays of different sizes. The
776 * sizes of those arrays is expressed through cl, which is the common length
777 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
778 * two lengths, calculated as len(a)-len(b). All lengths are the number of
779 * BN_ULONGs...
780 */
781
782int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
783{
784 int n, i;
785 n = cl - 1;
786
787 if (dl < 0) {
788 for (i = dl; i < 0; i++) {
789 if (b[n - i] != 0)
790 return -1; /* a < b */
791 }
792 }
793 if (dl > 0) {
794 for (i = dl; i > 0; i--) {
795 if (a[n + i] != 0)
796 return 1; /* a > b */
797 }
798 }
799 return bn_cmp_words(a, b, cl);
800}
801
802/*-
803 * Constant-time conditional swap of a and b.
804 * a and b are swapped if condition is not 0.
805 * nwords is the number of words to swap.
806 * Assumes that at least nwords are allocated in both a and b.
807 * Assumes that no more than nwords are used by either a or b.
808 */
809void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
810{
811 BN_ULONG t;
812 int i;
813
814 if (a == b)
815 return;
816
817 bn_wcheck_size(a, nwords);
818 bn_wcheck_size(b, nwords);
819
820 condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
821
822 t = (a->top ^ b->top) & condition;
823 a->top ^= t;
824 b->top ^= t;
825
826 t = (a->neg ^ b->neg) & condition;
827 a->neg ^= t;
828 b->neg ^= t;
829
830 /*-
831 * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
832 * is actually to treat it as it's read-only data, and some (if not most)
833 * of it does reside in read-only segment. In other words observation of
834 * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
835 * condition. It would either cause SEGV or effectively cause data
836 * corruption.
837 *
838 * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
839 * preserved.
840 *
841 * BN_FLG_SECURE: must be preserved, because it determines how x->d was
842 * allocated and hence how to free it.
843 *
844 * BN_FLG_CONSTTIME: sufficient to mask and swap
845 *
846 * BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
847 * the data, so the d array may be padded with additional 0 values (i.e.
848 * top could be greater than the minimal value that it could be). We should
849 * be swapping it
850 */
851
852#define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
853
854 t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
855 a->flags ^= t;
856 b->flags ^= t;
857
858 /* conditionally swap the data */
859 for (i = 0; i < nwords; i++) {
860 t = (a->d[i] ^ b->d[i]) & condition;
861 a->d[i] ^= t;
862 b->d[i] ^= t;
863 }
864}
865
866#undef BN_CONSTTIME_SWAP_FLAGS
867
868/* Bits of security, see SP800-57 */
869
870int BN_security_bits(int L, int N)
871{
872 int secbits, bits;
873 if (L >= 15360)
874 secbits = 256;
875 else if (L >= 7680)
876 secbits = 192;
877 else if (L >= 3072)
878 secbits = 128;
879 else if (L >= 2048)
880 secbits = 112;
881 else if (L >= 1024)
882 secbits = 80;
883 else
884 return 0;
885 if (N == -1)
886 return secbits;
887 bits = N / 2;
888 if (bits < 80)
889 return 0;
890 return bits >= secbits ? secbits : bits;
891}
892
893void BN_zero_ex(BIGNUM *a)
894{
895 a->neg = 0;
896 a->top = 0;
897 a->flags &= ~BN_FLG_FIXED_TOP;
898}
899
900int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
901{
902 return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
903}
904
905int BN_is_zero(const BIGNUM *a)
906{
907 return a->top == 0;
908}
909
910int BN_is_one(const BIGNUM *a)
911{
912 return BN_abs_is_word(a, 1) && !a->neg;
913}
914
915int BN_is_word(const BIGNUM *a, const BN_ULONG w)
916{
917 return BN_abs_is_word(a, w) && (!w || !a->neg);
918}
919
920int BN_is_odd(const BIGNUM *a)
921{
922 return (a->top > 0) && (a->d[0] & 1);
923}
924
925int BN_is_negative(const BIGNUM *a)
926{
927 return (a->neg != 0);
928}
929
930int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
931 BN_CTX *ctx)
932{
933 return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
934}
935
936void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
937{
938 dest->d = b->d;
939 dest->top = b->top;
940 dest->dmax = b->dmax;
941 dest->neg = b->neg;
942 dest->flags = ((dest->flags & BN_FLG_MALLOCED)
943 | (b->flags & ~BN_FLG_MALLOCED)
944 | BN_FLG_STATIC_DATA | flags);
945}
946
947BN_GENCB *BN_GENCB_new(void)
948{
949 BN_GENCB *ret;
950
951 if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
952 BNerr(BN_F_BN_GENCB_NEW, ERR_R_MALLOC_FAILURE);
953 return NULL;
954 }
955
956 return ret;
957}
958
959void BN_GENCB_free(BN_GENCB *cb)
960{
961 if (cb == NULL)
962 return;
963 OPENSSL_free(cb);
964}
965
966void BN_set_flags(BIGNUM *b, int n)
967{
968 b->flags |= n;
969}
970
971int BN_get_flags(const BIGNUM *b, int n)
972{
973 return b->flags & n;
974}
975
976/* Populate a BN_GENCB structure with an "old"-style callback */
977void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
978 void *cb_arg)
979{
980 BN_GENCB *tmp_gencb = gencb;
981 tmp_gencb->ver = 1;
982 tmp_gencb->arg = cb_arg;
983 tmp_gencb->cb.cb_1 = callback;
984}
985
986/* Populate a BN_GENCB structure with a "new"-style callback */
987void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
988 void *cb_arg)
989{
990 BN_GENCB *tmp_gencb = gencb;
991 tmp_gencb->ver = 2;
992 tmp_gencb->arg = cb_arg;
993 tmp_gencb->cb.cb_2 = callback;
994}
995
996void *BN_GENCB_get_arg(BN_GENCB *cb)
997{
998 return cb->arg;
999}
1000
1001BIGNUM *bn_wexpand(BIGNUM *a, int words)
1002{
1003 return (words <= a->dmax) ? a : bn_expand2(a, words);
1004}
1005
1006void bn_correct_top(BIGNUM *a)
1007{
1008 BN_ULONG *ftl;
1009 int tmp_top = a->top;
1010
1011 if (tmp_top > 0) {
1012 for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
1013 ftl--;
1014 if (*ftl != 0)
1015 break;
1016 }
1017 a->top = tmp_top;
1018 }
1019 if (a->top == 0)
1020 a->neg = 0;
1021 a->flags &= ~BN_FLG_FIXED_TOP;
1022 bn_pollute(a);
1023}
1024