1 /*
2 * Copyright 1995-2020 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
BN_set_params(int mult,int high,int low,int mont)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
BN_get_params(int which)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
BN_value_one(void)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
BN_num_bits_word(BN_ULONG l)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
bn_num_bits_consttime(const BIGNUM * a)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
BN_num_bits(const BIGNUM * a)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
bn_free_d(BIGNUM * a,int clear)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
BN_clear_free(BIGNUM * a)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
BN_free(BIGNUM * a)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
bn_init(BIGNUM * a)235 void bn_init(BIGNUM *a)
236 {
237 static BIGNUM nilbn;
238
239 *a = nilbn;
240 bn_check_top(a);
241 }
242
BN_new(void)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
BN_secure_new(void)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 */
bn_expand_internal(const BIGNUM * b,int words)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
bn_expand2(BIGNUM * b,int words)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
BN_dup(const BIGNUM * a)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
BN_copy(BIGNUM * a,const BIGNUM * b)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
BN_swap(BIGNUM * a,BIGNUM * b)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
BN_clear(BIGNUM * a)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
BN_get_word(const BIGNUM * a)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
BN_set_word(BIGNUM * a,BN_ULONG w)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
BN_bin2bn(const unsigned char * s,int len,BIGNUM * ret)433 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
434 {
435 unsigned int i, m;
436 unsigned int n;
437 BN_ULONG l;
438 BIGNUM *bn = NULL;
439
440 if (ret == NULL)
441 ret = bn = BN_new();
442 if (ret == NULL)
443 return NULL;
444 bn_check_top(ret);
445 /* Skip leading zero's. */
446 for ( ; len > 0 && *s == 0; s++, len--)
447 continue;
448 n = len;
449 if (n == 0) {
450 ret->top = 0;
451 return ret;
452 }
453 i = ((n - 1) / BN_BYTES) + 1;
454 m = ((n - 1) % (BN_BYTES));
455 if (bn_wexpand(ret, (int)i) == NULL) {
456 BN_free(bn);
457 return NULL;
458 }
459 ret->top = i;
460 ret->neg = 0;
461 l = 0;
462 while (n--) {
463 l = (l << 8L) | *(s++);
464 if (m-- == 0) {
465 ret->d[--i] = l;
466 l = 0;
467 m = BN_BYTES - 1;
468 }
469 }
470 /*
471 * need to call this due to clear byte at top if avoiding having the top
472 * bit set (-ve number)
473 */
474 bn_correct_top(ret);
475 return ret;
476 }
477
478 typedef enum {big, little} endianess_t;
479
480 /* ignore negative */
481 static
bn2binpad(const BIGNUM * a,unsigned char * to,int tolen,endianess_t endianess)482 int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen, endianess_t endianess)
483 {
484 int n;
485 size_t i, lasti, j, atop, mask;
486 BN_ULONG l;
487
488 /*
489 * In case |a| is fixed-top, BN_num_bytes can return bogus length,
490 * but it's assumed that fixed-top inputs ought to be "nominated"
491 * even for padded output, so it works out...
492 */
493 n = BN_num_bytes(a);
494 if (tolen == -1) {
495 tolen = n;
496 } else if (tolen < n) { /* uncommon/unlike case */
497 BIGNUM temp = *a;
498
499 bn_correct_top(&temp);
500 n = BN_num_bytes(&temp);
501 if (tolen < n)
502 return -1;
503 }
504
505 /* Swipe through whole available data and don't give away padded zero. */
506 atop = a->dmax * BN_BYTES;
507 if (atop == 0) {
508 OPENSSL_cleanse(to, tolen);
509 return tolen;
510 }
511
512 lasti = atop - 1;
513 atop = a->top * BN_BYTES;
514 if (endianess == big)
515 to += tolen; /* start from the end of the buffer */
516 for (i = 0, j = 0; j < (size_t)tolen; j++) {
517 unsigned char val;
518 l = a->d[i / BN_BYTES];
519 mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
520 val = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
521 if (endianess == big)
522 *--to = val;
523 else
524 *to++ = val;
525 i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
526 }
527
528 return tolen;
529 }
530
BN_bn2binpad(const BIGNUM * a,unsigned char * to,int tolen)531 int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
532 {
533 if (tolen < 0)
534 return -1;
535 return bn2binpad(a, to, tolen, big);
536 }
537
BN_bn2bin(const BIGNUM * a,unsigned char * to)538 int BN_bn2bin(const BIGNUM *a, unsigned char *to)
539 {
540 return bn2binpad(a, to, -1, big);
541 }
542
BN_lebin2bn(const unsigned char * s,int len,BIGNUM * ret)543 BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
544 {
545 unsigned int i, m;
546 unsigned int n;
547 BN_ULONG l;
548 BIGNUM *bn = NULL;
549
550 if (ret == NULL)
551 ret = bn = BN_new();
552 if (ret == NULL)
553 return NULL;
554 bn_check_top(ret);
555 s += len;
556 /* Skip trailing zeroes. */
557 for ( ; len > 0 && s[-1] == 0; s--, len--)
558 continue;
559 n = len;
560 if (n == 0) {
561 ret->top = 0;
562 return ret;
563 }
564 i = ((n - 1) / BN_BYTES) + 1;
565 m = ((n - 1) % (BN_BYTES));
566 if (bn_wexpand(ret, (int)i) == NULL) {
567 BN_free(bn);
568 return NULL;
569 }
570 ret->top = i;
571 ret->neg = 0;
572 l = 0;
573 while (n--) {
574 s--;
575 l = (l << 8L) | *s;
576 if (m-- == 0) {
577 ret->d[--i] = l;
578 l = 0;
579 m = BN_BYTES - 1;
580 }
581 }
582 /*
583 * need to call this due to clear byte at top if avoiding having the top
584 * bit set (-ve number)
585 */
586 bn_correct_top(ret);
587 return ret;
588 }
589
BN_bn2lebinpad(const BIGNUM * a,unsigned char * to,int tolen)590 int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
591 {
592 if (tolen < 0)
593 return -1;
594 return bn2binpad(a, to, tolen, little);
595 }
596
BN_native2bn(const unsigned char * s,int len,BIGNUM * ret)597 BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret)
598 {
599 DECLARE_IS_ENDIAN;
600
601 if (IS_LITTLE_ENDIAN)
602 return BN_lebin2bn(s, len, ret);
603 return BN_bin2bn(s, len, ret);
604 }
605
BN_bn2nativepad(const BIGNUM * a,unsigned char * to,int tolen)606 int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen)
607 {
608 DECLARE_IS_ENDIAN;
609
610 if (IS_LITTLE_ENDIAN)
611 return BN_bn2lebinpad(a, to, tolen);
612 return BN_bn2binpad(a, to, tolen);
613 }
614
BN_ucmp(const BIGNUM * a,const BIGNUM * b)615 int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
616 {
617 int i;
618 BN_ULONG t1, t2, *ap, *bp;
619
620 bn_check_top(a);
621 bn_check_top(b);
622
623 i = a->top - b->top;
624 if (i != 0)
625 return i;
626 ap = a->d;
627 bp = b->d;
628 for (i = a->top - 1; i >= 0; i--) {
629 t1 = ap[i];
630 t2 = bp[i];
631 if (t1 != t2)
632 return ((t1 > t2) ? 1 : -1);
633 }
634 return 0;
635 }
636
BN_cmp(const BIGNUM * a,const BIGNUM * b)637 int BN_cmp(const BIGNUM *a, const BIGNUM *b)
638 {
639 int i;
640 int gt, lt;
641 BN_ULONG t1, t2;
642
643 if ((a == NULL) || (b == NULL)) {
644 if (a != NULL)
645 return -1;
646 else if (b != NULL)
647 return 1;
648 else
649 return 0;
650 }
651
652 bn_check_top(a);
653 bn_check_top(b);
654
655 if (a->neg != b->neg) {
656 if (a->neg)
657 return -1;
658 else
659 return 1;
660 }
661 if (a->neg == 0) {
662 gt = 1;
663 lt = -1;
664 } else {
665 gt = -1;
666 lt = 1;
667 }
668
669 if (a->top > b->top)
670 return gt;
671 if (a->top < b->top)
672 return lt;
673 for (i = a->top - 1; i >= 0; i--) {
674 t1 = a->d[i];
675 t2 = b->d[i];
676 if (t1 > t2)
677 return gt;
678 if (t1 < t2)
679 return lt;
680 }
681 return 0;
682 }
683
BN_set_bit(BIGNUM * a,int n)684 int BN_set_bit(BIGNUM *a, int n)
685 {
686 int i, j, k;
687
688 if (n < 0)
689 return 0;
690
691 i = n / BN_BITS2;
692 j = n % BN_BITS2;
693 if (a->top <= i) {
694 if (bn_wexpand(a, i + 1) == NULL)
695 return 0;
696 for (k = a->top; k < i + 1; k++)
697 a->d[k] = 0;
698 a->top = i + 1;
699 a->flags &= ~BN_FLG_FIXED_TOP;
700 }
701
702 a->d[i] |= (((BN_ULONG)1) << j);
703 bn_check_top(a);
704 return 1;
705 }
706
BN_clear_bit(BIGNUM * a,int n)707 int BN_clear_bit(BIGNUM *a, int n)
708 {
709 int i, j;
710
711 bn_check_top(a);
712 if (n < 0)
713 return 0;
714
715 i = n / BN_BITS2;
716 j = n % BN_BITS2;
717 if (a->top <= i)
718 return 0;
719
720 a->d[i] &= (~(((BN_ULONG)1) << j));
721 bn_correct_top(a);
722 return 1;
723 }
724
BN_is_bit_set(const BIGNUM * a,int n)725 int BN_is_bit_set(const BIGNUM *a, int n)
726 {
727 int i, j;
728
729 bn_check_top(a);
730 if (n < 0)
731 return 0;
732 i = n / BN_BITS2;
733 j = n % BN_BITS2;
734 if (a->top <= i)
735 return 0;
736 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
737 }
738
BN_mask_bits(BIGNUM * a,int n)739 int BN_mask_bits(BIGNUM *a, int n)
740 {
741 int b, w;
742
743 bn_check_top(a);
744 if (n < 0)
745 return 0;
746
747 w = n / BN_BITS2;
748 b = n % BN_BITS2;
749 if (w >= a->top)
750 return 0;
751 if (b == 0)
752 a->top = w;
753 else {
754 a->top = w + 1;
755 a->d[w] &= ~(BN_MASK2 << b);
756 }
757 bn_correct_top(a);
758 return 1;
759 }
760
BN_set_negative(BIGNUM * a,int b)761 void BN_set_negative(BIGNUM *a, int b)
762 {
763 if (b && !BN_is_zero(a))
764 a->neg = 1;
765 else
766 a->neg = 0;
767 }
768
bn_cmp_words(const BN_ULONG * a,const BN_ULONG * b,int n)769 int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
770 {
771 int i;
772 BN_ULONG aa, bb;
773
774 if (n == 0)
775 return 0;
776
777 aa = a[n - 1];
778 bb = b[n - 1];
779 if (aa != bb)
780 return ((aa > bb) ? 1 : -1);
781 for (i = n - 2; i >= 0; i--) {
782 aa = a[i];
783 bb = b[i];
784 if (aa != bb)
785 return ((aa > bb) ? 1 : -1);
786 }
787 return 0;
788 }
789
790 /*
791 * Here follows a specialised variants of bn_cmp_words(). It has the
792 * capability of performing the operation on arrays of different sizes. The
793 * sizes of those arrays is expressed through cl, which is the common length
794 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
795 * two lengths, calculated as len(a)-len(b). All lengths are the number of
796 * BN_ULONGs...
797 */
798
bn_cmp_part_words(const BN_ULONG * a,const BN_ULONG * b,int cl,int dl)799 int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
800 {
801 int n, i;
802 n = cl - 1;
803
804 if (dl < 0) {
805 for (i = dl; i < 0; i++) {
806 if (b[n - i] != 0)
807 return -1; /* a < b */
808 }
809 }
810 if (dl > 0) {
811 for (i = dl; i > 0; i--) {
812 if (a[n + i] != 0)
813 return 1; /* a > b */
814 }
815 }
816 return bn_cmp_words(a, b, cl);
817 }
818
819 /*-
820 * Constant-time conditional swap of a and b.
821 * a and b are swapped if condition is not 0.
822 * nwords is the number of words to swap.
823 * Assumes that at least nwords are allocated in both a and b.
824 * Assumes that no more than nwords are used by either a or b.
825 */
BN_consttime_swap(BN_ULONG condition,BIGNUM * a,BIGNUM * b,int nwords)826 void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
827 {
828 BN_ULONG t;
829 int i;
830
831 if (a == b)
832 return;
833
834 bn_wcheck_size(a, nwords);
835 bn_wcheck_size(b, nwords);
836
837 condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
838
839 t = (a->top ^ b->top) & condition;
840 a->top ^= t;
841 b->top ^= t;
842
843 t = (a->neg ^ b->neg) & condition;
844 a->neg ^= t;
845 b->neg ^= t;
846
847 /*-
848 * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
849 * is actually to treat it as it's read-only data, and some (if not most)
850 * of it does reside in read-only segment. In other words observation of
851 * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
852 * condition. It would either cause SEGV or effectively cause data
853 * corruption.
854 *
855 * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
856 * preserved.
857 *
858 * BN_FLG_SECURE: must be preserved, because it determines how x->d was
859 * allocated and hence how to free it.
860 *
861 * BN_FLG_CONSTTIME: sufficient to mask and swap
862 *
863 * BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
864 * the data, so the d array may be padded with additional 0 values (i.e.
865 * top could be greater than the minimal value that it could be). We should
866 * be swapping it
867 */
868
869 #define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
870
871 t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
872 a->flags ^= t;
873 b->flags ^= t;
874
875 /* conditionally swap the data */
876 for (i = 0; i < nwords; i++) {
877 t = (a->d[i] ^ b->d[i]) & condition;
878 a->d[i] ^= t;
879 b->d[i] ^= t;
880 }
881 }
882
883 #undef BN_CONSTTIME_SWAP_FLAGS
884
885 /* Bits of security, see SP800-57 */
886
BN_security_bits(int L,int N)887 int BN_security_bits(int L, int N)
888 {
889 int secbits, bits;
890 if (L >= 15360)
891 secbits = 256;
892 else if (L >= 7680)
893 secbits = 192;
894 else if (L >= 3072)
895 secbits = 128;
896 else if (L >= 2048)
897 secbits = 112;
898 else if (L >= 1024)
899 secbits = 80;
900 else
901 return 0;
902 if (N == -1)
903 return secbits;
904 bits = N / 2;
905 if (bits < 80)
906 return 0;
907 return bits >= secbits ? secbits : bits;
908 }
909
BN_zero_ex(BIGNUM * a)910 void BN_zero_ex(BIGNUM *a)
911 {
912 a->neg = 0;
913 a->top = 0;
914 a->flags &= ~BN_FLG_FIXED_TOP;
915 }
916
BN_abs_is_word(const BIGNUM * a,const BN_ULONG w)917 int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
918 {
919 return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
920 }
921
BN_is_zero(const BIGNUM * a)922 int BN_is_zero(const BIGNUM *a)
923 {
924 return a->top == 0;
925 }
926
BN_is_one(const BIGNUM * a)927 int BN_is_one(const BIGNUM *a)
928 {
929 return BN_abs_is_word(a, 1) && !a->neg;
930 }
931
BN_is_word(const BIGNUM * a,const BN_ULONG w)932 int BN_is_word(const BIGNUM *a, const BN_ULONG w)
933 {
934 return BN_abs_is_word(a, w) && (!w || !a->neg);
935 }
936
BN_is_odd(const BIGNUM * a)937 int BN_is_odd(const BIGNUM *a)
938 {
939 return (a->top > 0) && (a->d[0] & 1);
940 }
941
BN_is_negative(const BIGNUM * a)942 int BN_is_negative(const BIGNUM *a)
943 {
944 return (a->neg != 0);
945 }
946
BN_to_montgomery(BIGNUM * r,const BIGNUM * a,BN_MONT_CTX * mont,BN_CTX * ctx)947 int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
948 BN_CTX *ctx)
949 {
950 return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
951 }
952
BN_with_flags(BIGNUM * dest,const BIGNUM * b,int flags)953 void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
954 {
955 dest->d = b->d;
956 dest->top = b->top;
957 dest->dmax = b->dmax;
958 dest->neg = b->neg;
959 dest->flags = ((dest->flags & BN_FLG_MALLOCED)
960 | (b->flags & ~BN_FLG_MALLOCED)
961 | BN_FLG_STATIC_DATA | flags);
962 }
963
BN_GENCB_new(void)964 BN_GENCB *BN_GENCB_new(void)
965 {
966 BN_GENCB *ret;
967
968 if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
969 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
970 return NULL;
971 }
972
973 return ret;
974 }
975
BN_GENCB_free(BN_GENCB * cb)976 void BN_GENCB_free(BN_GENCB *cb)
977 {
978 if (cb == NULL)
979 return;
980 OPENSSL_free(cb);
981 }
982
BN_set_flags(BIGNUM * b,int n)983 void BN_set_flags(BIGNUM *b, int n)
984 {
985 b->flags |= n;
986 }
987
BN_get_flags(const BIGNUM * b,int n)988 int BN_get_flags(const BIGNUM *b, int n)
989 {
990 return b->flags & n;
991 }
992
993 /* Populate a BN_GENCB structure with an "old"-style callback */
BN_GENCB_set_old(BN_GENCB * gencb,void (* callback)(int,int,void *),void * cb_arg)994 void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
995 void *cb_arg)
996 {
997 BN_GENCB *tmp_gencb = gencb;
998 tmp_gencb->ver = 1;
999 tmp_gencb->arg = cb_arg;
1000 tmp_gencb->cb.cb_1 = callback;
1001 }
1002
1003 /* Populate a BN_GENCB structure with a "new"-style callback */
BN_GENCB_set(BN_GENCB * gencb,int (* callback)(int,int,BN_GENCB *),void * cb_arg)1004 void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
1005 void *cb_arg)
1006 {
1007 BN_GENCB *tmp_gencb = gencb;
1008 tmp_gencb->ver = 2;
1009 tmp_gencb->arg = cb_arg;
1010 tmp_gencb->cb.cb_2 = callback;
1011 }
1012
BN_GENCB_get_arg(BN_GENCB * cb)1013 void *BN_GENCB_get_arg(BN_GENCB *cb)
1014 {
1015 return cb->arg;
1016 }
1017
bn_wexpand(BIGNUM * a,int words)1018 BIGNUM *bn_wexpand(BIGNUM *a, int words)
1019 {
1020 return (words <= a->dmax) ? a : bn_expand2(a, words);
1021 }
1022
bn_correct_top(BIGNUM * a)1023 void bn_correct_top(BIGNUM *a)
1024 {
1025 BN_ULONG *ftl;
1026 int tmp_top = a->top;
1027
1028 if (tmp_top > 0) {
1029 for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
1030 ftl--;
1031 if (*ftl != 0)
1032 break;
1033 }
1034 a->top = tmp_top;
1035 }
1036 if (a->top == 0)
1037 a->neg = 0;
1038 a->flags &= ~BN_FLG_FIXED_TOP;
1039 bn_pollute(a);
1040 }
1041