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1/* $OpenBSD: bn_lib.c,v 1.34 2015/09/10 15:56:25 jsing 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#ifndef BN_DEBUG
60# undef NDEBUG /* avoid conflicting definitions */
61# define NDEBUG
62#endif
63
64#include <assert.h>
65#include <limits.h>
66#include <stdio.h>
67#include <string.h>
68
69#include <openssl/opensslconf.h>
70
71#include <openssl/err.h>
72
73#include "bn_lcl.h"
74
75/* This stuff appears to be completely unused, so is deprecated */
76#ifndef OPENSSL_NO_DEPRECATED
77/* For a 32 bit machine
78 * 2 - 4 == 128
79 * 3 - 8 == 256
80 * 4 - 16 == 512
81 * 5 - 32 == 1024
82 * 6 - 64 == 2048
83 * 7 - 128 == 4096
84 * 8 - 256 == 8192
85 */
86static int bn_limit_bits = 0;
87static int bn_limit_num = 8; /* (1<<bn_limit_bits) */
88static int bn_limit_bits_low = 0;
89static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */
90static int bn_limit_bits_high = 0;
91static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */
92static int bn_limit_bits_mont = 0;
93static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */
94
95void
96BN_set_params(int mult, int high, int low, int mont)
97{
98 if (mult >= 0) {
99 if (mult > (int)(sizeof(int) * 8) - 1)
100 mult = sizeof(int) * 8 - 1;
101 bn_limit_bits = mult;
102 bn_limit_num = 1 << mult;
103 }
104 if (high >= 0) {
105 if (high > (int)(sizeof(int) * 8) - 1)
106 high = sizeof(int) * 8 - 1;
107 bn_limit_bits_high = high;
108 bn_limit_num_high = 1 << high;
109 }
110 if (low >= 0) {
111 if (low > (int)(sizeof(int) * 8) - 1)
112 low = sizeof(int) * 8 - 1;
113 bn_limit_bits_low = low;
114 bn_limit_num_low = 1 << low;
115 }
116 if (mont >= 0) {
117 if (mont > (int)(sizeof(int) * 8) - 1)
118 mont = sizeof(int) * 8 - 1;
119 bn_limit_bits_mont = mont;
120 bn_limit_num_mont = 1 << mont;
121 }
122}
123
124int
125BN_get_params(int which)
126{
127 if (which == 0)
128 return (bn_limit_bits);
129 else if (which == 1)
130 return (bn_limit_bits_high);
131 else if (which == 2)
132 return (bn_limit_bits_low);
133 else if (which == 3)
134 return (bn_limit_bits_mont);
135 else
136 return (0);
137}
138#endif
139
140const BIGNUM *
141BN_value_one(void)
142{
143 static const BN_ULONG data_one = 1L;
144 static const BIGNUM const_one = {
145 (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA
146 };
147
148 return (&const_one);
149}
150
151int
152BN_num_bits_word(BN_ULONG l)
153{
154 static const unsigned char bits[256] = {
155 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
156 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
157 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
158 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
159 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
160 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
161 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
162 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
163 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
164 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
165 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
166 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
167 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
168 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
169 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
170 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
171 };
172
173#ifdef _LP64
174 if (l & 0xffffffff00000000L) {
175 if (l & 0xffff000000000000L) {
176 if (l & 0xff00000000000000L) {
177 return (bits[(int)(l >> 56)] + 56);
178 } else
179 return (bits[(int)(l >> 48)] + 48);
180 } else {
181 if (l & 0x0000ff0000000000L) {
182 return (bits[(int)(l >> 40)] + 40);
183 } else
184 return (bits[(int)(l >> 32)] + 32);
185 }
186 } else
187#endif
188 {
189 if (l & 0xffff0000L) {
190 if (l & 0xff000000L)
191 return (bits[(int)(l >> 24L)] + 24);
192 else
193 return (bits[(int)(l >> 16L)] + 16);
194 } else {
195 if (l & 0xff00L)
196 return (bits[(int)(l >> 8)] + 8);
197 else
198 return (bits[(int)(l)]);
199 }
200 }
201}
202
203int
204BN_num_bits(const BIGNUM *a)
205{
206 int i = a->top - 1;
207
208 bn_check_top(a);
209
210 if (BN_is_zero(a))
211 return 0;
212 return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
213}
214
215void
216BN_clear_free(BIGNUM *a)
217{
218 int i;
219
220 if (a == NULL)
221 return;
222 bn_check_top(a);
223 if (a->d != NULL && !(BN_get_flags(a, BN_FLG_STATIC_DATA))) {
224 explicit_bzero(a->d, a->dmax * sizeof(a->d[0]));
225 free(a->d);
226 }
227 i = BN_get_flags(a, BN_FLG_MALLOCED);
228 explicit_bzero(a, sizeof(BIGNUM));
229 if (i)
230 free(a);
231}
232
233void
234BN_free(BIGNUM *a)
235{
236 BN_clear_free(a);
237}
238
239void
240BN_init(BIGNUM *a)
241{
242 memset(a, 0, sizeof(BIGNUM));
243 bn_check_top(a);
244}
245
246BIGNUM *
247BN_new(void)
248{
249 BIGNUM *ret;
250
251 if ((ret = malloc(sizeof(BIGNUM))) == NULL) {
252 BNerr(BN_F_BN_NEW, ERR_R_MALLOC_FAILURE);
253 return (NULL);
254 }
255 ret->flags = BN_FLG_MALLOCED;
256 ret->top = 0;
257 ret->neg = 0;
258 ret->dmax = 0;
259 ret->d = NULL;
260 bn_check_top(ret);
261 return (ret);
262}
263
264/* This is used both by bn_expand2() and bn_dup_expand() */
265/* The caller MUST check that words > b->dmax before calling this */
266static BN_ULONG *
267bn_expand_internal(const BIGNUM *b, int words)
268{
269 BN_ULONG *A, *a = NULL;
270 const BN_ULONG *B;
271 int i;
272
273 bn_check_top(b);
274
275 if (words > (INT_MAX/(4*BN_BITS2))) {
276 BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_BIGNUM_TOO_LONG);
277 return NULL;
278 }
279 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
280 BNerr(BN_F_BN_EXPAND_INTERNAL,
281 BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
282 return (NULL);
283 }
284 a = A = reallocarray(NULL, words, sizeof(BN_ULONG));
285 if (A == NULL) {
286 BNerr(BN_F_BN_EXPAND_INTERNAL, ERR_R_MALLOC_FAILURE);
287 return (NULL);
288 }
289#if 1
290 B = b->d;
291 /* Check if the previous number needs to be copied */
292 if (B != NULL) {
293 for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) {
294 /*
295 * The fact that the loop is unrolled
296 * 4-wise is a tribute to Intel. It's
297 * the one that doesn't have enough
298 * registers to accomodate more data.
299 * I'd unroll it 8-wise otherwise:-)
300 *
301 * <appro@fy.chalmers.se>
302 */
303 BN_ULONG a0, a1, a2, a3;
304 a0 = B[0];
305 a1 = B[1];
306 a2 = B[2];
307 a3 = B[3];
308 A[0] = a0;
309 A[1] = a1;
310 A[2] = a2;
311 A[3] = a3;
312 }
313 switch (b->top & 3) {
314 case 3:
315 A[2] = B[2];
316 case 2:
317 A[1] = B[1];
318 case 1:
319 A[0] = B[0];
320 }
321 }
322
323#else
324 memset(A, 0, sizeof(BN_ULONG) * words);
325 memcpy(A, b->d, sizeof(b->d[0]) * b->top);
326#endif
327
328 return (a);
329}
330
331/* This is an internal function that can be used instead of bn_expand2()
332 * when there is a need to copy BIGNUMs instead of only expanding the
333 * data part, while still expanding them.
334 * Especially useful when needing to expand BIGNUMs that are declared
335 * 'const' and should therefore not be changed.
336 * The reason to use this instead of a BN_dup() followed by a bn_expand2()
337 * is memory allocation overhead. A BN_dup() followed by a bn_expand2()
338 * will allocate new memory for the BIGNUM data twice, and free it once,
339 * while bn_dup_expand() makes sure allocation is made only once.
340 */
341
342#ifndef OPENSSL_NO_DEPRECATED
343BIGNUM *
344bn_dup_expand(const BIGNUM *b, int words)
345{
346 BIGNUM *r = NULL;
347
348 bn_check_top(b);
349
350 /* This function does not work if
351 * words <= b->dmax && top < words
352 * because BN_dup() does not preserve 'dmax'!
353 * (But bn_dup_expand() is not used anywhere yet.)
354 */
355
356 if (words > b->dmax) {
357 BN_ULONG *a = bn_expand_internal(b, words);
358
359 if (a) {
360 r = BN_new();
361 if (r) {
362 r->top = b->top;
363 r->dmax = words;
364 r->neg = b->neg;
365 r->d = a;
366 } else {
367 /* r == NULL, BN_new failure */
368 free(a);
369 }
370 }
371 /* If a == NULL, there was an error in allocation in
372 bn_expand_internal(), and NULL should be returned */
373 } else {
374 r = BN_dup(b);
375 }
376
377 bn_check_top(r);
378 return r;
379}
380#endif
381
382/* This is an internal function that should not be used in applications.
383 * It ensures that 'b' has enough room for a 'words' word number
384 * and initialises any unused part of b->d with leading zeros.
385 * It is mostly used by the various BIGNUM routines. If there is an error,
386 * NULL is returned. If not, 'b' is returned. */
387
388BIGNUM *
389bn_expand2(BIGNUM *b, int words)
390{
391 bn_check_top(b);
392
393 if (words > b->dmax) {
394 BN_ULONG *a = bn_expand_internal(b, words);
395 if (!a)
396 return NULL;
397 if (b->d) {
398 explicit_bzero(b->d, b->dmax * sizeof(b->d[0]));
399 free(b->d);
400 }
401 b->d = a;
402 b->dmax = words;
403 }
404
405/* None of this should be necessary because of what b->top means! */
406#if 0
407 /* NB: bn_wexpand() calls this only if the BIGNUM really has to grow */
408 if (b->top < b->dmax) {
409 int i;
410 BN_ULONG *A = &(b->d[b->top]);
411 for (i = (b->dmax - b->top) >> 3; i > 0; i--, A += 8) {
412 A[0] = 0;
413 A[1] = 0;
414 A[2] = 0;
415 A[3] = 0;
416 A[4] = 0;
417 A[5] = 0;
418 A[6] = 0;
419 A[7] = 0;
420 }
421 for (i = (b->dmax - b->top)&7; i > 0; i--, A++)
422 A[0] = 0;
423 assert(A == &(b->d[b->dmax]));
424 }
425#endif
426 bn_check_top(b);
427 return b;
428}
429
430BIGNUM *
431BN_dup(const BIGNUM *a)
432{
433 BIGNUM *t;
434
435 if (a == NULL)
436 return NULL;
437 bn_check_top(a);
438
439 t = BN_new();
440 if (t == NULL)
441 return NULL;
442 if (!BN_copy(t, a)) {
443 BN_free(t);
444 return NULL;
445 }
446 bn_check_top(t);
447 return t;
448}
449
450BIGNUM *
451BN_copy(BIGNUM *a, const BIGNUM *b)
452{
453 int i;
454 BN_ULONG *A;
455 const BN_ULONG *B;
456
457 bn_check_top(b);
458
459 if (a == b)
460 return (a);
461 if (bn_wexpand(a, b->top) == NULL)
462 return (NULL);
463
464#if 1
465 A = a->d;
466 B = b->d;
467 for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) {
468 BN_ULONG a0, a1, a2, a3;
469 a0 = B[0];
470 a1 = B[1];
471 a2 = B[2];
472 a3 = B[3];
473 A[0] = a0;
474 A[1] = a1;
475 A[2] = a2;
476 A[3] = a3;
477 }
478 switch (b->top & 3) {
479 case 3:
480 A[2] = B[2];
481 case 2:
482 A[1] = B[1];
483 case 1:
484 A[0] = B[0];
485 }
486#else
487 memcpy(a->d, b->d, sizeof(b->d[0]) * b->top);
488#endif
489
490 a->top = b->top;
491 a->neg = b->neg;
492 bn_check_top(a);
493 return (a);
494}
495
496void
497BN_swap(BIGNUM *a, BIGNUM *b)
498{
499 int flags_old_a, flags_old_b;
500 BN_ULONG *tmp_d;
501 int tmp_top, tmp_dmax, tmp_neg;
502
503 bn_check_top(a);
504 bn_check_top(b);
505
506 flags_old_a = a->flags;
507 flags_old_b = b->flags;
508
509 tmp_d = a->d;
510 tmp_top = a->top;
511 tmp_dmax = a->dmax;
512 tmp_neg = a->neg;
513
514 a->d = b->d;
515 a->top = b->top;
516 a->dmax = b->dmax;
517 a->neg = b->neg;
518
519 b->d = tmp_d;
520 b->top = tmp_top;
521 b->dmax = tmp_dmax;
522 b->neg = tmp_neg;
523
524 a->flags = (flags_old_a & BN_FLG_MALLOCED) |
525 (flags_old_b & BN_FLG_STATIC_DATA);
526 b->flags = (flags_old_b & BN_FLG_MALLOCED) |
527 (flags_old_a & BN_FLG_STATIC_DATA);
528 bn_check_top(a);
529 bn_check_top(b);
530}
531
532void
533BN_clear(BIGNUM *a)
534{
535 bn_check_top(a);
536 if (a->d != NULL)
537 memset(a->d, 0, a->dmax * sizeof(a->d[0]));
538 a->top = 0;
539 a->neg = 0;
540}
541
542BN_ULONG
543BN_get_word(const BIGNUM *a)
544{
545 if (a->top > 1)
546 return BN_MASK2;
547 else if (a->top == 1)
548 return a->d[0];
549 /* a->top == 0 */
550 return 0;
551}
552
553int
554BN_set_word(BIGNUM *a, BN_ULONG w)
555{
556 bn_check_top(a);
557 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
558 return (0);
559 a->neg = 0;
560 a->d[0] = w;
561 a->top = (w ? 1 : 0);
562 bn_check_top(a);
563 return (1);
564}
565
566BIGNUM *
567BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
568{
569 unsigned int i, m;
570 unsigned int n;
571 BN_ULONG l;
572 BIGNUM *bn = NULL;
573
574 if (ret == NULL)
575 ret = bn = BN_new();
576 if (ret == NULL)
577 return (NULL);
578 bn_check_top(ret);
579 l = 0;
580 n = len;
581 if (n == 0) {
582 ret->top = 0;
583 return (ret);
584 }
585 i = ((n - 1) / BN_BYTES) + 1;
586 m = ((n - 1) % (BN_BYTES));
587 if (bn_wexpand(ret, (int)i) == NULL) {
588 BN_free(bn);
589 return NULL;
590 }
591 ret->top = i;
592 ret->neg = 0;
593 while (n--) {
594 l = (l << 8L) | *(s++);
595 if (m-- == 0) {
596 ret->d[--i] = l;
597 l = 0;
598 m = BN_BYTES - 1;
599 }
600 }
601 /* need to call this due to clear byte at top if avoiding
602 * having the top bit set (-ve number) */
603 bn_correct_top(ret);
604 return (ret);
605}
606
607/* ignore negative */
608int
609BN_bn2bin(const BIGNUM *a, unsigned char *to)
610{
611 int n, i;
612 BN_ULONG l;
613
614 bn_check_top(a);
615 n = i=BN_num_bytes(a);
616 while (i--) {
617 l = a->d[i / BN_BYTES];
618 *(to++) = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff;
619 }
620 return (n);
621}
622
623int
624BN_ucmp(const BIGNUM *a, const BIGNUM *b)
625{
626 int i;
627 BN_ULONG t1, t2, *ap, *bp;
628
629 bn_check_top(a);
630 bn_check_top(b);
631
632 i = a->top - b->top;
633 if (i != 0)
634 return (i);
635 ap = a->d;
636 bp = b->d;
637 for (i = a->top - 1; i >= 0; i--) {
638 t1 = ap[i];
639 t2 = bp[i];
640 if (t1 != t2)
641 return ((t1 > t2) ? 1 : -1);
642 }
643 return (0);
644}
645
646int
647BN_cmp(const BIGNUM *a, const BIGNUM *b)
648{
649 int i;
650 int gt, lt;
651 BN_ULONG t1, t2;
652
653 if ((a == NULL) || (b == NULL)) {
654 if (a != NULL)
655 return (-1);
656 else if (b != NULL)
657 return (1);
658 else
659 return (0);
660 }
661
662 bn_check_top(a);
663 bn_check_top(b);
664
665 if (a->neg != b->neg) {
666 if (a->neg)
667 return (-1);
668 else
669 return (1);
670 }
671 if (a->neg == 0) {
672 gt = 1;
673 lt = -1;
674 } else {
675 gt = -1;
676 lt = 1;
677 }
678
679 if (a->top > b->top)
680 return (gt);
681 if (a->top < b->top)
682 return (lt);
683 for (i = a->top - 1; i >= 0; i--) {
684 t1 = a->d[i];
685 t2 = b->d[i];
686 if (t1 > t2)
687 return (gt);
688 if (t1 < t2)
689 return (lt);
690 }
691 return (0);
692}
693
694int
695BN_set_bit(BIGNUM *a, int n)
696{
697 int i, j, k;
698
699 if (n < 0)
700 return 0;
701
702 i = n / BN_BITS2;
703 j = n % BN_BITS2;
704 if (a->top <= i) {
705 if (bn_wexpand(a, i + 1) == NULL)
706 return (0);
707 for (k = a->top; k < i + 1; k++)
708 a->d[k] = 0;
709 a->top = i + 1;
710 }
711
712 a->d[i] |= (((BN_ULONG)1) << j);
713 bn_check_top(a);
714 return (1);
715}
716
717int
718BN_clear_bit(BIGNUM *a, int n)
719{
720 int i, j;
721
722 bn_check_top(a);
723 if (n < 0)
724 return 0;
725
726 i = n / BN_BITS2;
727 j = n % BN_BITS2;
728 if (a->top <= i)
729 return (0);
730
731 a->d[i] &= (~(((BN_ULONG)1) << j));
732 bn_correct_top(a);
733 return (1);
734}
735
736int
737BN_is_bit_set(const BIGNUM *a, int n)
738{
739 int i, j;
740
741 bn_check_top(a);
742 if (n < 0)
743 return 0;
744 i = n / BN_BITS2;
745 j = n % BN_BITS2;
746 if (a->top <= i)
747 return 0;
748 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
749}
750
751int
752BN_mask_bits(BIGNUM *a, int n)
753{
754 int b, w;
755
756 bn_check_top(a);
757 if (n < 0)
758 return 0;
759
760 w = n / BN_BITS2;
761 b = n % BN_BITS2;
762 if (w >= a->top)
763 return 0;
764 if (b == 0)
765 a->top = w;
766 else {
767 a->top = w + 1;
768 a->d[w] &= ~(BN_MASK2 << b);
769 }
770 bn_correct_top(a);
771 return (1);
772}
773
774void
775BN_set_negative(BIGNUM *a, int b)
776{
777 if (b && !BN_is_zero(a))
778 a->neg = 1;
779 else
780 a->neg = 0;
781}
782
783int
784bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
785{
786 int i;
787 BN_ULONG aa, bb;
788
789 aa = a[n - 1];
790 bb = b[n - 1];
791 if (aa != bb)
792 return ((aa > bb) ? 1 : -1);
793 for (i = n - 2; i >= 0; i--) {
794 aa = a[i];
795 bb = b[i];
796 if (aa != bb)
797 return ((aa > bb) ? 1 : -1);
798 }
799 return (0);
800}
801
802/* Here follows a specialised variants of bn_cmp_words(). It has the
803 property of performing the operation on arrays of different sizes.
804 The sizes of those arrays is expressed through cl, which is the
805 common length ( basicall, min(len(a),len(b)) ), and dl, which is the
806 delta between the two lengths, calculated as len(a)-len(b).
807 All lengths are the number of BN_ULONGs... */
808
809int
810bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
811{
812 int n, i;
813
814 n = cl - 1;
815
816 if (dl < 0) {
817 for (i = dl; i < 0; i++) {
818 if (b[n - i] != 0)
819 return -1; /* a < b */
820 }
821 }
822 if (dl > 0) {
823 for (i = dl; i > 0; i--) {
824 if (a[n + i] != 0)
825 return 1; /* a > b */
826 }
827 }
828 return bn_cmp_words(a, b, cl);
829}
830
831/*
832 * Constant-time conditional swap of a and b.
833 * a and b are swapped if condition is not 0. The code assumes that at most one bit of condition is set.
834 * nwords is the number of words to swap. The code assumes that at least nwords are allocated in both a and b,
835 * and that no more than nwords are used by either a or b.
836 * a and b cannot be the same number
837 */
838void
839BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
840{
841 BN_ULONG t;
842 int i;
843
844 bn_wcheck_size(a, nwords);
845 bn_wcheck_size(b, nwords);
846
847 assert(a != b);
848 assert((condition & (condition - 1)) == 0);
849 assert(sizeof(BN_ULONG) >= sizeof(int));
850
851 condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1;
852
853 t = (a->top^b->top) & condition;
854 a->top ^= t;
855 b->top ^= t;
856
857#define BN_CONSTTIME_SWAP(ind) \
858 do { \
859 t = (a->d[ind] ^ b->d[ind]) & condition; \
860 a->d[ind] ^= t; \
861 b->d[ind] ^= t; \
862 } while (0)
863
864
865 switch (nwords) {
866 default:
867 for (i = 10; i < nwords; i++)
868 BN_CONSTTIME_SWAP(i);
869 /* Fallthrough */
870 case 10: BN_CONSTTIME_SWAP(9); /* Fallthrough */
871 case 9: BN_CONSTTIME_SWAP(8); /* Fallthrough */
872 case 8: BN_CONSTTIME_SWAP(7); /* Fallthrough */
873 case 7: BN_CONSTTIME_SWAP(6); /* Fallthrough */
874 case 6: BN_CONSTTIME_SWAP(5); /* Fallthrough */
875 case 5: BN_CONSTTIME_SWAP(4); /* Fallthrough */
876 case 4: BN_CONSTTIME_SWAP(3); /* Fallthrough */
877 case 3: BN_CONSTTIME_SWAP(2); /* Fallthrough */
878 case 2: BN_CONSTTIME_SWAP(1); /* Fallthrough */
879 case 1:
880 BN_CONSTTIME_SWAP(0);
881 }
882#undef BN_CONSTTIME_SWAP
883}
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-12-24 19:07:00 +0000