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1/* $OpenBSD: bn_lib.c,v 1.36 2016/03/15 20:50:22 krw 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 accommodate 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
553BIGNUM *
554bn_expand(BIGNUM *a, int bits)
555{
556 if (bits > (INT_MAX - BN_BITS2 + 1))
557 return (NULL);
558
559 if (((bits + BN_BITS2 - 1) / BN_BITS2) <= a->dmax)
560 return (a);
561
562 return bn_expand2(a, (bits + BN_BITS2 - 1) / BN_BITS2);
563}
564
565int
566BN_set_word(BIGNUM *a, BN_ULONG w)
567{
568 bn_check_top(a);
569 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
570 return (0);
571 a->neg = 0;
572 a->d[0] = w;
573 a->top = (w ? 1 : 0);
574 bn_check_top(a);
575 return (1);
576}
577
578BIGNUM *
579BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
580{
581 unsigned int i, m;
582 unsigned int n;
583 BN_ULONG l;
584 BIGNUM *bn = NULL;
585
586 if (ret == NULL)
587 ret = bn = BN_new();
588 if (ret == NULL)
589 return (NULL);
590 bn_check_top(ret);
591 l = 0;
592 n = len;
593 if (n == 0) {
594 ret->top = 0;
595 return (ret);
596 }
597 i = ((n - 1) / BN_BYTES) + 1;
598 m = ((n - 1) % (BN_BYTES));
599 if (bn_wexpand(ret, (int)i) == NULL) {
600 BN_free(bn);
601 return NULL;
602 }
603 ret->top = i;
604 ret->neg = 0;
605 while (n--) {
606 l = (l << 8L) | *(s++);
607 if (m-- == 0) {
608 ret->d[--i] = l;
609 l = 0;
610 m = BN_BYTES - 1;
611 }
612 }
613 /* need to call this due to clear byte at top if avoiding
614 * having the top bit set (-ve number) */
615 bn_correct_top(ret);
616 return (ret);
617}
618
619/* ignore negative */
620int
621BN_bn2bin(const BIGNUM *a, unsigned char *to)
622{
623 int n, i;
624 BN_ULONG l;
625
626 bn_check_top(a);
627 n = i=BN_num_bytes(a);
628 while (i--) {
629 l = a->d[i / BN_BYTES];
630 *(to++) = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff;
631 }
632 return (n);
633}
634
635int
636BN_ucmp(const BIGNUM *a, const BIGNUM *b)
637{
638 int i;
639 BN_ULONG t1, t2, *ap, *bp;
640
641 bn_check_top(a);
642 bn_check_top(b);
643
644 i = a->top - b->top;
645 if (i != 0)
646 return (i);
647 ap = a->d;
648 bp = b->d;
649 for (i = a->top - 1; i >= 0; i--) {
650 t1 = ap[i];
651 t2 = bp[i];
652 if (t1 != t2)
653 return ((t1 > t2) ? 1 : -1);
654 }
655 return (0);
656}
657
658int
659BN_cmp(const BIGNUM *a, const BIGNUM *b)
660{
661 int i;
662 int gt, lt;
663 BN_ULONG t1, t2;
664
665 if ((a == NULL) || (b == NULL)) {
666 if (a != NULL)
667 return (-1);
668 else if (b != NULL)
669 return (1);
670 else
671 return (0);
672 }
673
674 bn_check_top(a);
675 bn_check_top(b);
676
677 if (a->neg != b->neg) {
678 if (a->neg)
679 return (-1);
680 else
681 return (1);
682 }
683 if (a->neg == 0) {
684 gt = 1;
685 lt = -1;
686 } else {
687 gt = -1;
688 lt = 1;
689 }
690
691 if (a->top > b->top)
692 return (gt);
693 if (a->top < b->top)
694 return (lt);
695 for (i = a->top - 1; i >= 0; i--) {
696 t1 = a->d[i];
697 t2 = b->d[i];
698 if (t1 > t2)
699 return (gt);
700 if (t1 < t2)
701 return (lt);
702 }
703 return (0);
704}
705
706int
707BN_set_bit(BIGNUM *a, int n)
708{
709 int i, j, k;
710
711 if (n < 0)
712 return 0;
713
714 i = n / BN_BITS2;
715 j = n % BN_BITS2;
716 if (a->top <= i) {
717 if (bn_wexpand(a, i + 1) == NULL)
718 return (0);
719 for (k = a->top; k < i + 1; k++)
720 a->d[k] = 0;
721 a->top = i + 1;
722 }
723
724 a->d[i] |= (((BN_ULONG)1) << j);
725 bn_check_top(a);
726 return (1);
727}
728
729int
730BN_clear_bit(BIGNUM *a, int n)
731{
732 int i, j;
733
734 bn_check_top(a);
735 if (n < 0)
736 return 0;
737
738 i = n / BN_BITS2;
739 j = n % BN_BITS2;
740 if (a->top <= i)
741 return (0);
742
743 a->d[i] &= (~(((BN_ULONG)1) << j));
744 bn_correct_top(a);
745 return (1);
746}
747
748int
749BN_is_bit_set(const BIGNUM *a, int n)
750{
751 int i, j;
752
753 bn_check_top(a);
754 if (n < 0)
755 return 0;
756 i = n / BN_BITS2;
757 j = n % BN_BITS2;
758 if (a->top <= i)
759 return 0;
760 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
761}
762
763int
764BN_mask_bits(BIGNUM *a, int n)
765{
766 int b, w;
767
768 bn_check_top(a);
769 if (n < 0)
770 return 0;
771
772 w = n / BN_BITS2;
773 b = n % BN_BITS2;
774 if (w >= a->top)
775 return 0;
776 if (b == 0)
777 a->top = w;
778 else {
779 a->top = w + 1;
780 a->d[w] &= ~(BN_MASK2 << b);
781 }
782 bn_correct_top(a);
783 return (1);
784}
785
786void
787BN_set_negative(BIGNUM *a, int b)
788{
789 if (b && !BN_is_zero(a))
790 a->neg = 1;
791 else
792 a->neg = 0;
793}
794
795int
796bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
797{
798 int i;
799 BN_ULONG aa, bb;
800
801 aa = a[n - 1];
802 bb = b[n - 1];
803 if (aa != bb)
804 return ((aa > bb) ? 1 : -1);
805 for (i = n - 2; i >= 0; i--) {
806 aa = a[i];
807 bb = b[i];
808 if (aa != bb)
809 return ((aa > bb) ? 1 : -1);
810 }
811 return (0);
812}
813
814/* Here follows a specialised variants of bn_cmp_words(). It has the
815 property of performing the operation on arrays of different sizes.
816 The sizes of those arrays is expressed through cl, which is the
817 common length ( basicall, min(len(a),len(b)) ), and dl, which is the
818 delta between the two lengths, calculated as len(a)-len(b).
819 All lengths are the number of BN_ULONGs... */
820
821int
822bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
823{
824 int n, i;
825
826 n = cl - 1;
827
828 if (dl < 0) {
829 for (i = dl; i < 0; i++) {
830 if (b[n - i] != 0)
831 return -1; /* a < b */
832 }
833 }
834 if (dl > 0) {
835 for (i = dl; i > 0; i--) {
836 if (a[n + i] != 0)
837 return 1; /* a > b */
838 }
839 }
840 return bn_cmp_words(a, b, cl);
841}
842
843/*
844 * Constant-time conditional swap of a and b.
845 * a and b are swapped if condition is not 0. The code assumes that at most one bit of condition is set.
846 * nwords is the number of words to swap. The code assumes that at least nwords are allocated in both a and b,
847 * and that no more than nwords are used by either a or b.
848 * a and b cannot be the same number
849 */
850void
851BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
852{
853 BN_ULONG t;
854 int i;
855
856 bn_wcheck_size(a, nwords);
857 bn_wcheck_size(b, nwords);
858
859 assert(a != b);
860 assert((condition & (condition - 1)) == 0);
861 assert(sizeof(BN_ULONG) >= sizeof(int));
862
863 condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1;
864
865 t = (a->top^b->top) & condition;
866 a->top ^= t;
867 b->top ^= t;
868
869#define BN_CONSTTIME_SWAP(ind) \
870 do { \
871 t = (a->d[ind] ^ b->d[ind]) & condition; \
872 a->d[ind] ^= t; \
873 b->d[ind] ^= t; \
874 } while (0)
875
876
877 switch (nwords) {
878 default:
879 for (i = 10; i < nwords; i++)
880 BN_CONSTTIME_SWAP(i);
881 /* Fallthrough */
882 case 10: BN_CONSTTIME_SWAP(9); /* Fallthrough */
883 case 9: BN_CONSTTIME_SWAP(8); /* Fallthrough */
884 case 8: BN_CONSTTIME_SWAP(7); /* Fallthrough */
885 case 7: BN_CONSTTIME_SWAP(6); /* Fallthrough */
886 case 6: BN_CONSTTIME_SWAP(5); /* Fallthrough */
887 case 5: BN_CONSTTIME_SWAP(4); /* Fallthrough */
888 case 4: BN_CONSTTIME_SWAP(3); /* Fallthrough */
889 case 3: BN_CONSTTIME_SWAP(2); /* Fallthrough */
890 case 2: BN_CONSTTIME_SWAP(1); /* Fallthrough */
891 case 1:
892 BN_CONSTTIME_SWAP(0);
893 }
894#undef BN_CONSTTIME_SWAP
895}
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