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1 /*
2 * Copyright 1995-2022 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 "internal/endian.h"
14 #include "bn_local.h"
15 #include <openssl/opensslconf.h>
16 #include "internal/constant_time.h"
17
18 /* This stuff appears to be completely unused, so is deprecated */
19 #ifndef OPENSSL_NO_DEPRECATED_0_9_8
20 /*-
21 * For a 32 bit machine
22 * 2 - 4 == 128
23 * 3 - 8 == 256
24 * 4 - 16 == 512
25 * 5 - 32 == 1024
26 * 6 - 64 == 2048
27 * 7 - 128 == 4096
28 * 8 - 256 == 8192
29 */
30 static int bn_limit_bits = 0;
31 static int bn_limit_num = 8; /* (1<<bn_limit_bits) */
32 static int bn_limit_bits_low = 0;
33 static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */
34 static int bn_limit_bits_high = 0;
35 static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */
36 static int bn_limit_bits_mont = 0;
37 static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */
38
39 void BN_set_params(int mult, int high, int low, int mont)
40 {
41 if (mult >= 0) {
42 if (mult > (int)(sizeof(int) * 8) - 1)
43 mult = sizeof(int) * 8 - 1;
44 bn_limit_bits = mult;
45 bn_limit_num = 1 << mult;
46 }
47 if (high >= 0) {
48 if (high > (int)(sizeof(int) * 8) - 1)
49 high = sizeof(int) * 8 - 1;
50 bn_limit_bits_high = high;
51 bn_limit_num_high = 1 << high;
52 }
53 if (low >= 0) {
54 if (low > (int)(sizeof(int) * 8) - 1)
55 low = sizeof(int) * 8 - 1;
56 bn_limit_bits_low = low;
57 bn_limit_num_low = 1 << low;
58 }
59 if (mont >= 0) {
60 if (mont > (int)(sizeof(int) * 8) - 1)
61 mont = sizeof(int) * 8 - 1;
62 bn_limit_bits_mont = mont;
63 bn_limit_num_mont = 1 << mont;
64 }
65 }
66
67 int BN_get_params(int which)
68 {
69 if (which == 0)
70 return bn_limit_bits;
71 else if (which == 1)
72 return bn_limit_bits_high;
73 else if (which == 2)
74 return bn_limit_bits_low;
75 else if (which == 3)
76 return bn_limit_bits_mont;
77 else
78 return 0;
79 }
80 #endif
81
82 const BIGNUM *BN_value_one(void)
83 {
84 static const BN_ULONG data_one = 1L;
85 static const BIGNUM const_one =
86 { (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA };
87
88 return &const_one;
89 }
90
91 /*
92 * Old Visual Studio ARM compiler miscompiles BN_num_bits_word()
93 * https://mta.openssl.org/pipermail/openssl-users/2018-August/008465.html
94 */
95 #if defined(_MSC_VER) && defined(_ARM_) && defined(_WIN32_WCE) \
96 && _MSC_VER>=1400 && _MSC_VER<1501
97 # define MS_BROKEN_BN_num_bits_word
98 # pragma optimize("", off)
99 #endif
100 int BN_num_bits_word(BN_ULONG l)
101 {
102 BN_ULONG x, mask;
103 int bits = (l != 0);
104
105 #if BN_BITS2 > 32
106 x = l >> 32;
107 mask = (0 - x) & BN_MASK2;
108 mask = (0 - (mask >> (BN_BITS2 - 1)));
109 bits += 32 & mask;
110 l ^= (x ^ l) & mask;
111 #endif
112
113 x = l >> 16;
114 mask = (0 - x) & BN_MASK2;
115 mask = (0 - (mask >> (BN_BITS2 - 1)));
116 bits += 16 & mask;
117 l ^= (x ^ l) & mask;
118
119 x = l >> 8;
120 mask = (0 - x) & BN_MASK2;
121 mask = (0 - (mask >> (BN_BITS2 - 1)));
122 bits += 8 & mask;
123 l ^= (x ^ l) & mask;
124
125 x = l >> 4;
126 mask = (0 - x) & BN_MASK2;
127 mask = (0 - (mask >> (BN_BITS2 - 1)));
128 bits += 4 & mask;
129 l ^= (x ^ l) & mask;
130
131 x = l >> 2;
132 mask = (0 - x) & BN_MASK2;
133 mask = (0 - (mask >> (BN_BITS2 - 1)));
134 bits += 2 & mask;
135 l ^= (x ^ l) & mask;
136
137 x = l >> 1;
138 mask = (0 - x) & BN_MASK2;
139 mask = (0 - (mask >> (BN_BITS2 - 1)));
140 bits += 1 & mask;
141
142 return bits;
143 }
144 #ifdef MS_BROKEN_BN_num_bits_word
145 # pragma optimize("", on)
146 #endif
147
148 /*
149 * This function still leaks `a->dmax`: it's caller's responsibility to
150 * expand the input `a` in advance to a public length.
151 */
152 static ossl_inline
153 int bn_num_bits_consttime(const BIGNUM *a)
154 {
155 int j, ret;
156 unsigned int mask, past_i;
157 int i = a->top - 1;
158 bn_check_top(a);
159
160 for (j = 0, past_i = 0, ret = 0; j < a->dmax; j++) {
161 mask = constant_time_eq_int(i, j); /* 0xff..ff if i==j, 0x0 otherwise */
162
163 ret += BN_BITS2 & (~mask & ~past_i);
164 ret += BN_num_bits_word(a->d[j]) & mask;
165
166 past_i |= mask; /* past_i will become 0xff..ff after i==j */
167 }
168
169 /*
170 * if BN_is_zero(a) => i is -1 and ret contains garbage, so we mask the
171 * final result.
172 */
173 mask = ~(constant_time_eq_int(i, ((int)-1)));
174
175 return ret & mask;
176 }
177
178 int BN_num_bits(const BIGNUM *a)
179 {
180 int i = a->top - 1;
181 bn_check_top(a);
182
183 if (a->flags & BN_FLG_CONSTTIME) {
184 /*
185 * We assume that BIGNUMs flagged as CONSTTIME have also been expanded
186 * so that a->dmax is not leaking secret information.
187 *
188 * In other words, it's the caller's responsibility to ensure `a` has
189 * been preallocated in advance to a public length if we hit this
190 * branch.
191 *
192 */
193 return bn_num_bits_consttime(a);
194 }
195
196 if (BN_is_zero(a))
197 return 0;
198
199 return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
200 }
201
202 static void bn_free_d(BIGNUM *a, int clear)
203 {
204 if (BN_get_flags(a, BN_FLG_SECURE))
205 OPENSSL_secure_clear_free(a->d, a->dmax * sizeof(a->d[0]));
206 else if (clear != 0)
207 OPENSSL_clear_free(a->d, a->dmax * sizeof(a->d[0]));
208 else
209 OPENSSL_free(a->d);
210 }
211
212
213 void BN_clear_free(BIGNUM *a)
214 {
215 if (a == NULL)
216 return;
217 if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA))
218 bn_free_d(a, 1);
219 if (BN_get_flags(a, BN_FLG_MALLOCED)) {
220 OPENSSL_cleanse(a, sizeof(*a));
221 OPENSSL_free(a);
222 }
223 }
224
225 void BN_free(BIGNUM *a)
226 {
227 if (a == NULL)
228 return;
229 if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
230 bn_free_d(a, 0);
231 if (a->flags & BN_FLG_MALLOCED)
232 OPENSSL_free(a);
233 }
234
235 void bn_init(BIGNUM *a)
236 {
237 static BIGNUM nilbn;
238
239 *a = nilbn;
240 bn_check_top(a);
241 }
242
243 BIGNUM *BN_new(void)
244 {
245 BIGNUM *ret;
246
247 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
248 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
249 return NULL;
250 }
251 ret->flags = BN_FLG_MALLOCED;
252 bn_check_top(ret);
253 return ret;
254 }
255
256 BIGNUM *BN_secure_new(void)
257 {
258 BIGNUM *ret = BN_new();
259 if (ret != NULL)
260 ret->flags |= BN_FLG_SECURE;
261 return ret;
262 }
263
264 /* This is used by bn_expand2() */
265 /* The caller MUST check that words > b->dmax before calling this */
266 static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
267 {
268 BN_ULONG *a = NULL;
269
270 if (words > (INT_MAX / (4 * BN_BITS2))) {
271 ERR_raise(ERR_LIB_BN, BN_R_BIGNUM_TOO_LONG);
272 return NULL;
273 }
274 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
275 ERR_raise(ERR_LIB_BN, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
276 return NULL;
277 }
278 if (BN_get_flags(b, BN_FLG_SECURE))
279 a = OPENSSL_secure_zalloc(words * sizeof(*a));
280 else
281 a = OPENSSL_zalloc(words * sizeof(*a));
282 if (a == NULL) {
283 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
284 return NULL;
285 }
286
287 assert(b->top <= words);
288 if (b->top > 0)
289 memcpy(a, b->d, sizeof(*a) * b->top);
290
291 return a;
292 }
293
294 /*
295 * This is an internal function that should not be used in applications. It
296 * ensures that 'b' has enough room for a 'words' word number and initialises
297 * any unused part of b->d with leading zeros. It is mostly used by the
298 * various BIGNUM routines. If there is an error, NULL is returned. If not,
299 * 'b' is returned.
300 */
301
302 BIGNUM *bn_expand2(BIGNUM *b, int words)
303 {
304 if (words > b->dmax) {
305 BN_ULONG *a = bn_expand_internal(b, words);
306 if (!a)
307 return NULL;
308 if (b->d != NULL)
309 bn_free_d(b, 1);
310 b->d = a;
311 b->dmax = words;
312 }
313
314 return b;
315 }
316
317 BIGNUM *BN_dup(const BIGNUM *a)
318 {
319 BIGNUM *t;
320
321 if (a == NULL)
322 return NULL;
323 bn_check_top(a);
324
325 t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
326 if (t == NULL)
327 return NULL;
328 if (!BN_copy(t, a)) {
329 BN_free(t);
330 return NULL;
331 }
332 bn_check_top(t);
333 return t;
334 }
335
336 BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
337 {
338 int bn_words;
339
340 bn_check_top(b);
341
342 bn_words = BN_get_flags(b, BN_FLG_CONSTTIME) ? b->dmax : b->top;
343
344 if (a == b)
345 return a;
346 if (bn_wexpand(a, bn_words) == NULL)
347 return NULL;
348
349 if (b->top > 0)
350 memcpy(a->d, b->d, sizeof(b->d[0]) * bn_words);
351
352 a->neg = b->neg;
353 a->top = b->top;
354 a->flags |= b->flags & BN_FLG_FIXED_TOP;
355 bn_check_top(a);
356 return a;
357 }
358
359 #define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
360 | BN_FLG_CONSTTIME \
361 | BN_FLG_SECURE \
362 | BN_FLG_FIXED_TOP))
363 #define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
364
365 void BN_swap(BIGNUM *a, BIGNUM *b)
366 {
367 int flags_old_a, flags_old_b;
368 BN_ULONG *tmp_d;
369 int tmp_top, tmp_dmax, tmp_neg;
370
371 bn_check_top(a);
372 bn_check_top(b);
373
374 flags_old_a = a->flags;
375 flags_old_b = b->flags;
376
377 tmp_d = a->d;
378 tmp_top = a->top;
379 tmp_dmax = a->dmax;
380 tmp_neg = a->neg;
381
382 a->d = b->d;
383 a->top = b->top;
384 a->dmax = b->dmax;
385 a->neg = b->neg;
386
387 b->d = tmp_d;
388 b->top = tmp_top;
389 b->dmax = tmp_dmax;
390 b->neg = tmp_neg;
391
392 a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
393 b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
394 bn_check_top(a);
395 bn_check_top(b);
396 }
397
398 void BN_clear(BIGNUM *a)
399 {
400 if (a == NULL)
401 return;
402 bn_check_top(a);
403 if (a->d != NULL)
404 OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
405 a->neg = 0;
406 a->top = 0;
407 a->flags &= ~BN_FLG_FIXED_TOP;
408 }
409
410 BN_ULONG BN_get_word(const BIGNUM *a)
411 {
412 if (a->top > 1)
413 return BN_MASK2;
414 else if (a->top == 1)
415 return a->d[0];
416 /* a->top == 0 */
417 return 0;
418 }
419
420 int BN_set_word(BIGNUM *a, BN_ULONG w)
421 {
422 bn_check_top(a);
423 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
424 return 0;
425 a->neg = 0;
426 a->d[0] = w;
427 a->top = (w ? 1 : 0);
428 a->flags &= ~BN_FLG_FIXED_TOP;
429 bn_check_top(a);
430 return 1;
431 }
432
433 typedef enum {BIG, LITTLE} endianess_t;
434 typedef enum {SIGNED, UNSIGNED} signedness_t;
435
436 static BIGNUM *bin2bn(const unsigned char *s, int len, BIGNUM *ret,
437 endianess_t endianess, signedness_t signedness)
438 {
439 int inc;
440 const unsigned char *s2;
441 int inc2;
442 int neg = 0, xor = 0, carry = 0;
443 unsigned int i;
444 unsigned int n;
445 BIGNUM *bn = NULL;
446
447 if (ret == NULL)
448 ret = bn = BN_new();
449 if (ret == NULL)
450 return NULL;
451 bn_check_top(ret);
452
453 /*
454 * The loop that does the work iterates from least to most
455 * significant BIGNUM chunk, so we adapt parameters to transfer
456 * input bytes accordingly.
457 */
458 if (endianess == LITTLE) {
459 s2 = s + len - 1;
460 inc2 = -1;
461 inc = 1;
462 } else {
463 s2 = s;
464 inc2 = 1;
465 inc = -1;
466 s += len - 1;
467 }
468
469 /* Take note of the signedness of the input bytes*/
470 if (signedness == SIGNED) {
471 neg = !!(*s2 & 0x80);
472 xor = neg ? 0xff : 0x00;
473 carry = neg;
474 }
475
476 /*
477 * Skip leading sign extensions (the value of |xor|).
478 * This is the only spot where |s2| and |inc2| are used.
479 */
480 for ( ; len > 0 && *s2 == xor; s2 += inc2, len--)
481 continue;
482
483 /*
484 * If there was a set of 0xff, we backtrack one byte unless the next
485 * one has a sign bit, as the last 0xff is then part of the actual
486 * number, rather then a mere sign extension.
487 */
488 if (xor == 0xff) {
489 if (len == 0 || !(*s2 & 0x80))
490 len++;
491 }
492 /* If it was all zeros, we're done */
493 if (len == 0) {
494 ret->top = 0;
495 return ret;
496 }
497 n = ((len - 1) / BN_BYTES) + 1; /* Number of resulting bignum chunks */
498 if (!ossl_assert(bn_wexpand(ret, (int)n) != NULL)) {
499 BN_free(bn);
500 return NULL;
501 }
502 ret->top = n;
503 ret->neg = neg;
504 for (i = 0; n-- > 0; i++) {
505 BN_ULONG l = 0; /* Accumulator */
506 unsigned int m = 0; /* Offset in a bignum chunk, in bits */
507
508 for (; len > 0 && m < BN_BYTES * 8; len--, s += inc, m += 8) {
509 BN_ULONG byte_xored = *s ^ xor;
510 BN_ULONG byte = (byte_xored + carry) & 0xff;
511
512 carry = byte_xored > byte; /* Implicit 1 or 0 */
513 l |= (byte << m);
514 }
515 ret->d[i] = l;
516 }
517 /*
518 * need to call this due to clear byte at top if avoiding having the top
519 * bit set (-ve number)
520 */
521 bn_correct_top(ret);
522 return ret;
523 }
524
525 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
526 {
527 return bin2bn(s, len, ret, BIG, UNSIGNED);
528 }
529
530 BIGNUM *BN_signed_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
531 {
532 return bin2bn(s, len, ret, BIG, SIGNED);
533 }
534
535 static int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen,
536 endianess_t endianess, signedness_t signedness)
537 {
538 int inc;
539 int n, n8;
540 int xor = 0, carry = 0, ext = 0;
541 size_t i, lasti, j, atop, mask;
542 BN_ULONG l;
543
544 /*
545 * In case |a| is fixed-top, BN_num_bits can return bogus length,
546 * but it's assumed that fixed-top inputs ought to be "nominated"
547 * even for padded output, so it works out...
548 */
549 n8 = BN_num_bits(a);
550 n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
551
552 /* Take note of the signedness of the bignum */
553 if (signedness == SIGNED) {
554 xor = a->neg ? 0xff : 0x00;
555 carry = a->neg;
556
557 /*
558 * if |n * 8 == n|, then the MSbit is set, otherwise unset.
559 * We must compensate with one extra byte if that doesn't
560 * correspond to the signedness of the bignum with regards
561 * to 2's complement.
562 */
563 ext = (n * 8 == n8)
564 ? !a->neg /* MSbit set on nonnegative bignum */
565 : a->neg; /* MSbit unset on negative bignum */
566 }
567
568 if (tolen == -1) {
569 tolen = n + ext;
570 } else if (tolen < n + ext) { /* uncommon/unlike case */
571 BIGNUM temp = *a;
572
573 bn_correct_top(&temp);
574 n8 = BN_num_bits(&temp);
575 n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
576 if (tolen < n + ext)
577 return -1;
578 }
579
580 /* Swipe through whole available data and don't give away padded zero. */
581 atop = a->dmax * BN_BYTES;
582 if (atop == 0) {
583 if (tolen != 0)
584 memset(to, '\0', tolen);
585 return tolen;
586 }
587
588 /*
589 * The loop that does the work iterates from least significant
590 * to most significant BIGNUM limb, so we adapt parameters to
591 * transfer output bytes accordingly.
592 */
593 if (endianess == LITTLE) {
594 inc = 1;
595 } else {
596 inc = -1;
597 to += tolen - 1; /* Move to the last byte, not beyond */
598 }
599
600 lasti = atop - 1;
601 atop = a->top * BN_BYTES;
602 for (i = 0, j = 0; j < (size_t)tolen; j++) {
603 unsigned char byte, byte_xored;
604
605 l = a->d[i / BN_BYTES];
606 mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
607 byte = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
608 byte_xored = byte ^ xor;
609 *to = (unsigned char)(byte_xored + carry);
610 carry = byte_xored > *to; /* Implicit 1 or 0 */
611 to += inc;
612 i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
613 }
614
615 return tolen;
616 }
617
618 int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
619 {
620 if (tolen < 0)
621 return -1;
622 return bn2binpad(a, to, tolen, BIG, UNSIGNED);
623 }
624
625 int BN_signed_bn2bin(const BIGNUM *a, unsigned char *to, int tolen)
626 {
627 if (tolen < 0)
628 return -1;
629 return bn2binpad(a, to, tolen, BIG, SIGNED);
630 }
631
632 int BN_bn2bin(const BIGNUM *a, unsigned char *to)
633 {
634 return bn2binpad(a, to, -1, BIG, UNSIGNED);
635 }
636
637 BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
638 {
639 return bin2bn(s, len, ret, LITTLE, UNSIGNED);
640 }
641
642 BIGNUM *BN_signed_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
643 {
644 return bin2bn(s, len, ret, LITTLE, SIGNED);
645 }
646
647 int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
648 {
649 if (tolen < 0)
650 return -1;
651 return bn2binpad(a, to, tolen, LITTLE, UNSIGNED);
652 }
653
654 int BN_signed_bn2lebin(const BIGNUM *a, unsigned char *to, int tolen)
655 {
656 if (tolen < 0)
657 return -1;
658 return bn2binpad(a, to, tolen, LITTLE, SIGNED);
659 }
660
661 BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret)
662 {
663 DECLARE_IS_ENDIAN;
664
665 if (IS_LITTLE_ENDIAN)
666 return BN_lebin2bn(s, len, ret);
667 return BN_bin2bn(s, len, ret);
668 }
669
670 BIGNUM *BN_signed_native2bn(const unsigned char *s, int len, BIGNUM *ret)
671 {
672 DECLARE_IS_ENDIAN;
673
674 if (IS_LITTLE_ENDIAN)
675 return BN_signed_lebin2bn(s, len, ret);
676 return BN_signed_bin2bn(s, len, ret);
677 }
678
679 int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen)
680 {
681 DECLARE_IS_ENDIAN;
682
683 if (IS_LITTLE_ENDIAN)
684 return BN_bn2lebinpad(a, to, tolen);
685 return BN_bn2binpad(a, to, tolen);
686 }
687
688 int BN_signed_bn2native(const BIGNUM *a, unsigned char *to, int tolen)
689 {
690 DECLARE_IS_ENDIAN;
691
692 if (IS_LITTLE_ENDIAN)
693 return BN_signed_bn2lebin(a, to, tolen);
694 return BN_signed_bn2bin(a, to, tolen);
695 }
696
697 int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
698 {
699 int i;
700 BN_ULONG t1, t2, *ap, *bp;
701
702 bn_check_top(a);
703 bn_check_top(b);
704
705 i = a->top - b->top;
706 if (i != 0)
707 return i;
708 ap = a->d;
709 bp = b->d;
710 for (i = a->top - 1; i >= 0; i--) {
711 t1 = ap[i];
712 t2 = bp[i];
713 if (t1 != t2)
714 return ((t1 > t2) ? 1 : -1);
715 }
716 return 0;
717 }
718
719 int BN_cmp(const BIGNUM *a, const BIGNUM *b)
720 {
721 int i;
722 int gt, lt;
723 BN_ULONG t1, t2;
724
725 if ((a == NULL) || (b == NULL)) {
726 if (a != NULL)
727 return -1;
728 else if (b != NULL)
729 return 1;
730 else
731 return 0;
732 }
733
734 bn_check_top(a);
735 bn_check_top(b);
736
737 if (a->neg != b->neg) {
738 if (a->neg)
739 return -1;
740 else
741 return 1;
742 }
743 if (a->neg == 0) {
744 gt = 1;
745 lt = -1;
746 } else {
747 gt = -1;
748 lt = 1;
749 }
750
751 if (a->top > b->top)
752 return gt;
753 if (a->top < b->top)
754 return lt;
755 for (i = a->top - 1; i >= 0; i--) {
756 t1 = a->d[i];
757 t2 = b->d[i];
758 if (t1 > t2)
759 return gt;
760 if (t1 < t2)
761 return lt;
762 }
763 return 0;
764 }
765
766 int BN_set_bit(BIGNUM *a, int n)
767 {
768 int i, j, k;
769
770 if (n < 0)
771 return 0;
772
773 i = n / BN_BITS2;
774 j = n % BN_BITS2;
775 if (a->top <= i) {
776 if (bn_wexpand(a, i + 1) == NULL)
777 return 0;
778 for (k = a->top; k < i + 1; k++)
779 a->d[k] = 0;
780 a->top = i + 1;
781 a->flags &= ~BN_FLG_FIXED_TOP;
782 }
783
784 a->d[i] |= (((BN_ULONG)1) << j);
785 bn_check_top(a);
786 return 1;
787 }
788
789 int BN_clear_bit(BIGNUM *a, int n)
790 {
791 int i, j;
792
793 bn_check_top(a);
794 if (n < 0)
795 return 0;
796
797 i = n / BN_BITS2;
798 j = n % BN_BITS2;
799 if (a->top <= i)
800 return 0;
801
802 a->d[i] &= (~(((BN_ULONG)1) << j));
803 bn_correct_top(a);
804 return 1;
805 }
806
807 int BN_is_bit_set(const BIGNUM *a, int n)
808 {
809 int i, j;
810
811 bn_check_top(a);
812 if (n < 0)
813 return 0;
814 i = n / BN_BITS2;
815 j = n % BN_BITS2;
816 if (a->top <= i)
817 return 0;
818 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
819 }
820
821 int BN_mask_bits(BIGNUM *a, int n)
822 {
823 int b, w;
824
825 bn_check_top(a);
826 if (n < 0)
827 return 0;
828
829 w = n / BN_BITS2;
830 b = n % BN_BITS2;
831 if (w >= a->top)
832 return 0;
833 if (b == 0)
834 a->top = w;
835 else {
836 a->top = w + 1;
837 a->d[w] &= ~(BN_MASK2 << b);
838 }
839 bn_correct_top(a);
840 return 1;
841 }
842
843 void BN_set_negative(BIGNUM *a, int b)
844 {
845 if (b && !BN_is_zero(a))
846 a->neg = 1;
847 else
848 a->neg = 0;
849 }
850
851 int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
852 {
853 int i;
854 BN_ULONG aa, bb;
855
856 if (n == 0)
857 return 0;
858
859 aa = a[n - 1];
860 bb = b[n - 1];
861 if (aa != bb)
862 return ((aa > bb) ? 1 : -1);
863 for (i = n - 2; i >= 0; i--) {
864 aa = a[i];
865 bb = b[i];
866 if (aa != bb)
867 return ((aa > bb) ? 1 : -1);
868 }
869 return 0;
870 }
871
872 /*
873 * Here follows a specialised variants of bn_cmp_words(). It has the
874 * capability of performing the operation on arrays of different sizes. The
875 * sizes of those arrays is expressed through cl, which is the common length
876 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
877 * two lengths, calculated as len(a)-len(b). All lengths are the number of
878 * BN_ULONGs...
879 */
880
881 int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
882 {
883 int n, i;
884 n = cl - 1;
885
886 if (dl < 0) {
887 for (i = dl; i < 0; i++) {
888 if (b[n - i] != 0)
889 return -1; /* a < b */
890 }
891 }
892 if (dl > 0) {
893 for (i = dl; i > 0; i--) {
894 if (a[n + i] != 0)
895 return 1; /* a > b */
896 }
897 }
898 return bn_cmp_words(a, b, cl);
899 }
900
901 /*-
902 * Constant-time conditional swap of a and b.
903 * a and b are swapped if condition is not 0.
904 * nwords is the number of words to swap.
905 * Assumes that at least nwords are allocated in both a and b.
906 * Assumes that no more than nwords are used by either a or b.
907 */
908 void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
909 {
910 BN_ULONG t;
911 int i;
912
913 if (a == b)
914 return;
915
916 bn_wcheck_size(a, nwords);
917 bn_wcheck_size(b, nwords);
918
919 condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
920
921 t = (a->top ^ b->top) & condition;
922 a->top ^= t;
923 b->top ^= t;
924
925 t = (a->neg ^ b->neg) & condition;
926 a->neg ^= t;
927 b->neg ^= t;
928
929 /*-
930 * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
931 * is actually to treat it as it's read-only data, and some (if not most)
932 * of it does reside in read-only segment. In other words observation of
933 * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
934 * condition. It would either cause SEGV or effectively cause data
935 * corruption.
936 *
937 * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
938 * preserved.
939 *
940 * BN_FLG_SECURE: must be preserved, because it determines how x->d was
941 * allocated and hence how to free it.
942 *
943 * BN_FLG_CONSTTIME: sufficient to mask and swap
944 *
945 * BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
946 * the data, so the d array may be padded with additional 0 values (i.e.
947 * top could be greater than the minimal value that it could be). We should
948 * be swapping it
949 */
950
951 #define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
952
953 t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
954 a->flags ^= t;
955 b->flags ^= t;
956
957 /* conditionally swap the data */
958 for (i = 0; i < nwords; i++) {
959 t = (a->d[i] ^ b->d[i]) & condition;
960 a->d[i] ^= t;
961 b->d[i] ^= t;
962 }
963 }
964
965 #undef BN_CONSTTIME_SWAP_FLAGS
966
967 /* Bits of security, see SP800-57 */
968
969 int BN_security_bits(int L, int N)
970 {
971 int secbits, bits;
972 if (L >= 15360)
973 secbits = 256;
974 else if (L >= 7680)
975 secbits = 192;
976 else if (L >= 3072)
977 secbits = 128;
978 else if (L >= 2048)
979 secbits = 112;
980 else if (L >= 1024)
981 secbits = 80;
982 else
983 return 0;
984 if (N == -1)
985 return secbits;
986 bits = N / 2;
987 if (bits < 80)
988 return 0;
989 return bits >= secbits ? secbits : bits;
990 }
991
992 void BN_zero_ex(BIGNUM *a)
993 {
994 a->neg = 0;
995 a->top = 0;
996 a->flags &= ~BN_FLG_FIXED_TOP;
997 }
998
999 int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
1000 {
1001 return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
1002 }
1003
1004 int BN_is_zero(const BIGNUM *a)
1005 {
1006 return a->top == 0;
1007 }
1008
1009 int BN_is_one(const BIGNUM *a)
1010 {
1011 return BN_abs_is_word(a, 1) && !a->neg;
1012 }
1013
1014 int BN_is_word(const BIGNUM *a, const BN_ULONG w)
1015 {
1016 return BN_abs_is_word(a, w) && (!w || !a->neg);
1017 }
1018
1019 int BN_is_odd(const BIGNUM *a)
1020 {
1021 return (a->top > 0) && (a->d[0] & 1);
1022 }
1023
1024 int BN_is_negative(const BIGNUM *a)
1025 {
1026 return (a->neg != 0);
1027 }
1028
1029 int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
1030 BN_CTX *ctx)
1031 {
1032 return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
1033 }
1034
1035 void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
1036 {
1037 dest->d = b->d;
1038 dest->top = b->top;
1039 dest->dmax = b->dmax;
1040 dest->neg = b->neg;
1041 dest->flags = ((dest->flags & BN_FLG_MALLOCED)
1042 | (b->flags & ~BN_FLG_MALLOCED)
1043 | BN_FLG_STATIC_DATA | flags);
1044 }
1045
1046 BN_GENCB *BN_GENCB_new(void)
1047 {
1048 BN_GENCB *ret;
1049
1050 if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
1051 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
1052 return NULL;
1053 }
1054
1055 return ret;
1056 }
1057
1058 void BN_GENCB_free(BN_GENCB *cb)
1059 {
1060 if (cb == NULL)
1061 return;
1062 OPENSSL_free(cb);
1063 }
1064
1065 void BN_set_flags(BIGNUM *b, int n)
1066 {
1067 b->flags |= n;
1068 }
1069
1070 int BN_get_flags(const BIGNUM *b, int n)
1071 {
1072 return b->flags & n;
1073 }
1074
1075 /* Populate a BN_GENCB structure with an "old"-style callback */
1076 void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
1077 void *cb_arg)
1078 {
1079 BN_GENCB *tmp_gencb = gencb;
1080 tmp_gencb->ver = 1;
1081 tmp_gencb->arg = cb_arg;
1082 tmp_gencb->cb.cb_1 = callback;
1083 }
1084
1085 /* Populate a BN_GENCB structure with a "new"-style callback */
1086 void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
1087 void *cb_arg)
1088 {
1089 BN_GENCB *tmp_gencb = gencb;
1090 tmp_gencb->ver = 2;
1091 tmp_gencb->arg = cb_arg;
1092 tmp_gencb->cb.cb_2 = callback;
1093 }
1094
1095 void *BN_GENCB_get_arg(BN_GENCB *cb)
1096 {
1097 return cb->arg;
1098 }
1099
1100 BIGNUM *bn_wexpand(BIGNUM *a, int words)
1101 {
1102 return (words <= a->dmax) ? a : bn_expand2(a, words);
1103 }
1104
1105 void bn_correct_top(BIGNUM *a)
1106 {
1107 BN_ULONG *ftl;
1108 int tmp_top = a->top;
1109
1110 if (tmp_top > 0) {
1111 for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
1112 ftl--;
1113 if (*ftl != 0)
1114 break;
1115 }
1116 a->top = tmp_top;
1117 }
1118 if (a->top == 0)
1119 a->neg = 0;
1120 a->flags &= ~BN_FLG_FIXED_TOP;
1121 bn_pollute(a);
1122 }