1 /*
2 * Copyright 1995-2023 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 return NULL;
249 ret->flags = BN_FLG_MALLOCED;
250 bn_check_top(ret);
251 return ret;
252 }
253
BN_secure_new(void)254 BIGNUM *BN_secure_new(void)
255 {
256 BIGNUM *ret = BN_new();
257 if (ret != NULL)
258 ret->flags |= BN_FLG_SECURE;
259 return ret;
260 }
261
262 /* This is used by bn_expand2() */
263 /* The caller MUST check that words > b->dmax before calling this */
bn_expand_internal(const BIGNUM * b,int words)264 static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
265 {
266 BN_ULONG *a = NULL;
267
268 if (words > (INT_MAX / (4 * BN_BITS2))) {
269 ERR_raise(ERR_LIB_BN, BN_R_BIGNUM_TOO_LONG);
270 return NULL;
271 }
272 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
273 ERR_raise(ERR_LIB_BN, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
274 return NULL;
275 }
276 if (BN_get_flags(b, BN_FLG_SECURE))
277 a = OPENSSL_secure_zalloc(words * sizeof(*a));
278 else
279 a = OPENSSL_zalloc(words * sizeof(*a));
280 if (a == NULL)
281 return NULL;
282
283 assert(b->top <= words);
284 if (b->top > 0)
285 memcpy(a, b->d, sizeof(*a) * b->top);
286
287 return a;
288 }
289
290 /*
291 * This is an internal function that should not be used in applications. It
292 * ensures that 'b' has enough room for a 'words' word number and initialises
293 * any unused part of b->d with leading zeros. It is mostly used by the
294 * various BIGNUM routines. If there is an error, NULL is returned. If not,
295 * 'b' is returned.
296 */
297
bn_expand2(BIGNUM * b,int words)298 BIGNUM *bn_expand2(BIGNUM *b, int words)
299 {
300 if (words > b->dmax) {
301 BN_ULONG *a = bn_expand_internal(b, words);
302 if (!a)
303 return NULL;
304 if (b->d != NULL)
305 bn_free_d(b, 1);
306 b->d = a;
307 b->dmax = words;
308 }
309
310 return b;
311 }
312
BN_dup(const BIGNUM * a)313 BIGNUM *BN_dup(const BIGNUM *a)
314 {
315 BIGNUM *t;
316
317 if (a == NULL)
318 return NULL;
319 bn_check_top(a);
320
321 t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
322 if (t == NULL)
323 return NULL;
324 if (!BN_copy(t, a)) {
325 BN_free(t);
326 return NULL;
327 }
328 bn_check_top(t);
329 return t;
330 }
331
BN_copy(BIGNUM * a,const BIGNUM * b)332 BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
333 {
334 int bn_words;
335
336 bn_check_top(b);
337
338 bn_words = BN_get_flags(b, BN_FLG_CONSTTIME) ? b->dmax : b->top;
339
340 if (a == b)
341 return a;
342 if (bn_wexpand(a, bn_words) == NULL)
343 return NULL;
344
345 if (b->top > 0)
346 memcpy(a->d, b->d, sizeof(b->d[0]) * bn_words);
347
348 a->neg = b->neg;
349 a->top = b->top;
350 a->flags |= b->flags & BN_FLG_FIXED_TOP;
351 bn_check_top(a);
352 return a;
353 }
354
355 #define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
356 | BN_FLG_CONSTTIME \
357 | BN_FLG_SECURE \
358 | BN_FLG_FIXED_TOP))
359 #define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
360
BN_swap(BIGNUM * a,BIGNUM * b)361 void BN_swap(BIGNUM *a, BIGNUM *b)
362 {
363 int flags_old_a, flags_old_b;
364 BN_ULONG *tmp_d;
365 int tmp_top, tmp_dmax, tmp_neg;
366
367 bn_check_top(a);
368 bn_check_top(b);
369
370 flags_old_a = a->flags;
371 flags_old_b = b->flags;
372
373 tmp_d = a->d;
374 tmp_top = a->top;
375 tmp_dmax = a->dmax;
376 tmp_neg = a->neg;
377
378 a->d = b->d;
379 a->top = b->top;
380 a->dmax = b->dmax;
381 a->neg = b->neg;
382
383 b->d = tmp_d;
384 b->top = tmp_top;
385 b->dmax = tmp_dmax;
386 b->neg = tmp_neg;
387
388 a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
389 b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
390 bn_check_top(a);
391 bn_check_top(b);
392 }
393
BN_clear(BIGNUM * a)394 void BN_clear(BIGNUM *a)
395 {
396 if (a == NULL)
397 return;
398 bn_check_top(a);
399 if (a->d != NULL)
400 OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
401 a->neg = 0;
402 a->top = 0;
403 a->flags &= ~BN_FLG_FIXED_TOP;
404 }
405
BN_get_word(const BIGNUM * a)406 BN_ULONG BN_get_word(const BIGNUM *a)
407 {
408 if (a->top > 1)
409 return BN_MASK2;
410 else if (a->top == 1)
411 return a->d[0];
412 /* a->top == 0 */
413 return 0;
414 }
415
BN_set_word(BIGNUM * a,BN_ULONG w)416 int BN_set_word(BIGNUM *a, BN_ULONG w)
417 {
418 bn_check_top(a);
419 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
420 return 0;
421 a->neg = 0;
422 a->d[0] = w;
423 a->top = (w ? 1 : 0);
424 a->flags &= ~BN_FLG_FIXED_TOP;
425 bn_check_top(a);
426 return 1;
427 }
428
429 typedef enum {BIG, LITTLE} endianness_t;
430 typedef enum {SIGNED, UNSIGNED} signedness_t;
431
bin2bn(const unsigned char * s,int len,BIGNUM * ret,endianness_t endianness,signedness_t signedness)432 static BIGNUM *bin2bn(const unsigned char *s, int len, BIGNUM *ret,
433 endianness_t endianness, signedness_t signedness)
434 {
435 int inc;
436 const unsigned char *s2;
437 int inc2;
438 int neg = 0, xor = 0, carry = 0;
439 unsigned int i;
440 unsigned int n;
441 BIGNUM *bn = NULL;
442
443 /* Negative length is not acceptable */
444 if (len < 0)
445 return 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 * If the input has no bits, the number is considered zero.
455 * This makes calls with s==NULL and len==0 safe.
456 */
457 if (len == 0) {
458 BN_clear(ret);
459 return ret;
460 }
461
462 /*
463 * The loop that does the work iterates from least to most
464 * significant BIGNUM chunk, so we adapt parameters to transfer
465 * input bytes accordingly.
466 */
467 if (endianness == LITTLE) {
468 s2 = s + len - 1;
469 inc2 = -1;
470 inc = 1;
471 } else {
472 s2 = s;
473 inc2 = 1;
474 inc = -1;
475 s += len - 1;
476 }
477
478 /* Take note of the signedness of the input bytes*/
479 if (signedness == SIGNED) {
480 neg = !!(*s2 & 0x80);
481 xor = neg ? 0xff : 0x00;
482 carry = neg;
483 }
484
485 /*
486 * Skip leading sign extensions (the value of |xor|).
487 * This is the only spot where |s2| and |inc2| are used.
488 */
489 for ( ; len > 0 && *s2 == xor; s2 += inc2, len--)
490 continue;
491
492 /*
493 * If there was a set of 0xff, we backtrack one byte unless the next
494 * one has a sign bit, as the last 0xff is then part of the actual
495 * number, rather then a mere sign extension.
496 */
497 if (xor == 0xff) {
498 if (len == 0 || !(*s2 & 0x80))
499 len++;
500 }
501 /* If it was all zeros, we're done */
502 if (len == 0) {
503 ret->top = 0;
504 return ret;
505 }
506 n = ((len - 1) / BN_BYTES) + 1; /* Number of resulting bignum chunks */
507 if (bn_wexpand(ret, (int)n) == NULL) {
508 BN_free(bn);
509 return NULL;
510 }
511 ret->top = n;
512 ret->neg = neg;
513 for (i = 0; n-- > 0; i++) {
514 BN_ULONG l = 0; /* Accumulator */
515 unsigned int m = 0; /* Offset in a bignum chunk, in bits */
516
517 for (; len > 0 && m < BN_BYTES * 8; len--, s += inc, m += 8) {
518 BN_ULONG byte_xored = *s ^ xor;
519 BN_ULONG byte = (byte_xored + carry) & 0xff;
520
521 carry = byte_xored > byte; /* Implicit 1 or 0 */
522 l |= (byte << m);
523 }
524 ret->d[i] = l;
525 }
526 /*
527 * need to call this due to clear byte at top if avoiding having the top
528 * bit set (-ve number)
529 */
530 bn_correct_top(ret);
531 return ret;
532 }
533
BN_bin2bn(const unsigned char * s,int len,BIGNUM * ret)534 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
535 {
536 return bin2bn(s, len, ret, BIG, UNSIGNED);
537 }
538
BN_signed_bin2bn(const unsigned char * s,int len,BIGNUM * ret)539 BIGNUM *BN_signed_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
540 {
541 return bin2bn(s, len, ret, BIG, SIGNED);
542 }
543
bn2binpad(const BIGNUM * a,unsigned char * to,int tolen,endianness_t endianness,signedness_t signedness)544 static int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen,
545 endianness_t endianness, signedness_t signedness)
546 {
547 int inc;
548 int n, n8;
549 int xor = 0, carry = 0, ext = 0;
550 size_t i, lasti, j, atop, mask;
551 BN_ULONG l;
552
553 /*
554 * In case |a| is fixed-top, BN_num_bits can return bogus length,
555 * but it's assumed that fixed-top inputs ought to be "nominated"
556 * even for padded output, so it works out...
557 */
558 n8 = BN_num_bits(a);
559 n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
560
561 /* Take note of the signedness of the bignum */
562 if (signedness == SIGNED) {
563 xor = a->neg ? 0xff : 0x00;
564 carry = a->neg;
565
566 /*
567 * if |n * 8 == n|, then the MSbit is set, otherwise unset.
568 * We must compensate with one extra byte if that doesn't
569 * correspond to the signedness of the bignum with regards
570 * to 2's complement.
571 */
572 ext = (n * 8 == n8)
573 ? !a->neg /* MSbit set on nonnegative bignum */
574 : a->neg; /* MSbit unset on negative bignum */
575 }
576
577 if (tolen == -1) {
578 tolen = n + ext;
579 } else if (tolen < n + ext) { /* uncommon/unlike case */
580 BIGNUM temp = *a;
581
582 bn_correct_top(&temp);
583 n8 = BN_num_bits(&temp);
584 n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
585 if (tolen < n + ext)
586 return -1;
587 }
588
589 /* Swipe through whole available data and don't give away padded zero. */
590 atop = a->dmax * BN_BYTES;
591 if (atop == 0) {
592 if (tolen != 0)
593 memset(to, '\0', tolen);
594 return tolen;
595 }
596
597 /*
598 * The loop that does the work iterates from least significant
599 * to most significant BIGNUM limb, so we adapt parameters to
600 * transfer output bytes accordingly.
601 */
602 if (endianness == LITTLE) {
603 inc = 1;
604 } else {
605 inc = -1;
606 to += tolen - 1; /* Move to the last byte, not beyond */
607 }
608
609 lasti = atop - 1;
610 atop = a->top * BN_BYTES;
611 for (i = 0, j = 0; j < (size_t)tolen; j++) {
612 unsigned char byte, byte_xored;
613
614 l = a->d[i / BN_BYTES];
615 mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
616 byte = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
617 byte_xored = byte ^ xor;
618 *to = (unsigned char)(byte_xored + carry);
619 carry = byte_xored > *to; /* Implicit 1 or 0 */
620 to += inc;
621 i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
622 }
623
624 return tolen;
625 }
626
BN_bn2binpad(const BIGNUM * a,unsigned char * to,int tolen)627 int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
628 {
629 if (tolen < 0)
630 return -1;
631 return bn2binpad(a, to, tolen, BIG, UNSIGNED);
632 }
633
BN_signed_bn2bin(const BIGNUM * a,unsigned char * to,int tolen)634 int BN_signed_bn2bin(const BIGNUM *a, unsigned char *to, int tolen)
635 {
636 if (tolen < 0)
637 return -1;
638 return bn2binpad(a, to, tolen, BIG, SIGNED);
639 }
640
BN_bn2bin(const BIGNUM * a,unsigned char * to)641 int BN_bn2bin(const BIGNUM *a, unsigned char *to)
642 {
643 return bn2binpad(a, to, -1, BIG, UNSIGNED);
644 }
645
BN_lebin2bn(const unsigned char * s,int len,BIGNUM * ret)646 BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
647 {
648 return bin2bn(s, len, ret, LITTLE, UNSIGNED);
649 }
650
BN_signed_lebin2bn(const unsigned char * s,int len,BIGNUM * ret)651 BIGNUM *BN_signed_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
652 {
653 return bin2bn(s, len, ret, LITTLE, SIGNED);
654 }
655
BN_bn2lebinpad(const BIGNUM * a,unsigned char * to,int tolen)656 int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
657 {
658 if (tolen < 0)
659 return -1;
660 return bn2binpad(a, to, tolen, LITTLE, UNSIGNED);
661 }
662
BN_signed_bn2lebin(const BIGNUM * a,unsigned char * to,int tolen)663 int BN_signed_bn2lebin(const BIGNUM *a, unsigned char *to, int tolen)
664 {
665 if (tolen < 0)
666 return -1;
667 return bn2binpad(a, to, tolen, LITTLE, SIGNED);
668 }
669
BN_native2bn(const unsigned char * s,int len,BIGNUM * ret)670 BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret)
671 {
672 DECLARE_IS_ENDIAN;
673
674 if (IS_LITTLE_ENDIAN)
675 return BN_lebin2bn(s, len, ret);
676 return BN_bin2bn(s, len, ret);
677 }
678
BN_signed_native2bn(const unsigned char * s,int len,BIGNUM * ret)679 BIGNUM *BN_signed_native2bn(const unsigned char *s, int len, BIGNUM *ret)
680 {
681 DECLARE_IS_ENDIAN;
682
683 if (IS_LITTLE_ENDIAN)
684 return BN_signed_lebin2bn(s, len, ret);
685 return BN_signed_bin2bn(s, len, ret);
686 }
687
BN_bn2nativepad(const BIGNUM * a,unsigned char * to,int tolen)688 int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen)
689 {
690 DECLARE_IS_ENDIAN;
691
692 if (IS_LITTLE_ENDIAN)
693 return BN_bn2lebinpad(a, to, tolen);
694 return BN_bn2binpad(a, to, tolen);
695 }
696
BN_signed_bn2native(const BIGNUM * a,unsigned char * to,int tolen)697 int BN_signed_bn2native(const BIGNUM *a, unsigned char *to, int tolen)
698 {
699 DECLARE_IS_ENDIAN;
700
701 if (IS_LITTLE_ENDIAN)
702 return BN_signed_bn2lebin(a, to, tolen);
703 return BN_signed_bn2bin(a, to, tolen);
704 }
705
BN_ucmp(const BIGNUM * a,const BIGNUM * b)706 int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
707 {
708 int i;
709 BN_ULONG t1, t2, *ap, *bp;
710
711 ap = a->d;
712 bp = b->d;
713
714 if (BN_get_flags(a, BN_FLG_CONSTTIME)
715 && a->top == b->top) {
716 int res = 0;
717
718 for (i = 0; i < b->top; i++) {
719 res = constant_time_select_int(constant_time_lt_bn(ap[i], bp[i]),
720 -1, res);
721 res = constant_time_select_int(constant_time_lt_bn(bp[i], ap[i]),
722 1, res);
723 }
724 return res;
725 }
726
727 bn_check_top(a);
728 bn_check_top(b);
729
730 i = a->top - b->top;
731 if (i != 0)
732 return i;
733
734 for (i = a->top - 1; i >= 0; i--) {
735 t1 = ap[i];
736 t2 = bp[i];
737 if (t1 != t2)
738 return ((t1 > t2) ? 1 : -1);
739 }
740 return 0;
741 }
742
BN_cmp(const BIGNUM * a,const BIGNUM * b)743 int BN_cmp(const BIGNUM *a, const BIGNUM *b)
744 {
745 int i;
746 int gt, lt;
747 BN_ULONG t1, t2;
748
749 if ((a == NULL) || (b == NULL)) {
750 if (a != NULL)
751 return -1;
752 else if (b != NULL)
753 return 1;
754 else
755 return 0;
756 }
757
758 bn_check_top(a);
759 bn_check_top(b);
760
761 if (a->neg != b->neg) {
762 if (a->neg)
763 return -1;
764 else
765 return 1;
766 }
767 if (a->neg == 0) {
768 gt = 1;
769 lt = -1;
770 } else {
771 gt = -1;
772 lt = 1;
773 }
774
775 if (a->top > b->top)
776 return gt;
777 if (a->top < b->top)
778 return lt;
779 for (i = a->top - 1; i >= 0; i--) {
780 t1 = a->d[i];
781 t2 = b->d[i];
782 if (t1 > t2)
783 return gt;
784 if (t1 < t2)
785 return lt;
786 }
787 return 0;
788 }
789
BN_set_bit(BIGNUM * a,int n)790 int BN_set_bit(BIGNUM *a, int n)
791 {
792 int i, j, k;
793
794 if (n < 0)
795 return 0;
796
797 i = n / BN_BITS2;
798 j = n % BN_BITS2;
799 if (a->top <= i) {
800 if (bn_wexpand(a, i + 1) == NULL)
801 return 0;
802 for (k = a->top; k < i + 1; k++)
803 a->d[k] = 0;
804 a->top = i + 1;
805 a->flags &= ~BN_FLG_FIXED_TOP;
806 }
807
808 a->d[i] |= (((BN_ULONG)1) << j);
809 bn_check_top(a);
810 return 1;
811 }
812
BN_clear_bit(BIGNUM * a,int n)813 int BN_clear_bit(BIGNUM *a, int n)
814 {
815 int i, j;
816
817 bn_check_top(a);
818 if (n < 0)
819 return 0;
820
821 i = n / BN_BITS2;
822 j = n % BN_BITS2;
823 if (a->top <= i)
824 return 0;
825
826 a->d[i] &= (~(((BN_ULONG)1) << j));
827 bn_correct_top(a);
828 return 1;
829 }
830
BN_is_bit_set(const BIGNUM * a,int n)831 int BN_is_bit_set(const BIGNUM *a, int n)
832 {
833 int i, j;
834
835 bn_check_top(a);
836 if (n < 0)
837 return 0;
838 i = n / BN_BITS2;
839 j = n % BN_BITS2;
840 if (a->top <= i)
841 return 0;
842 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
843 }
844
ossl_bn_mask_bits_fixed_top(BIGNUM * a,int n)845 int ossl_bn_mask_bits_fixed_top(BIGNUM *a, int n)
846 {
847 int b, w;
848
849 if (n < 0)
850 return 0;
851
852 w = n / BN_BITS2;
853 b = n % BN_BITS2;
854 if (w >= a->top)
855 return 0;
856 if (b == 0)
857 a->top = w;
858 else {
859 a->top = w + 1;
860 a->d[w] &= ~(BN_MASK2 << b);
861 }
862 a->flags |= BN_FLG_FIXED_TOP;
863 return 1;
864 }
865
BN_mask_bits(BIGNUM * a,int n)866 int BN_mask_bits(BIGNUM *a, int n)
867 {
868 int ret;
869
870 bn_check_top(a);
871 ret = ossl_bn_mask_bits_fixed_top(a, n);
872 if (ret)
873 bn_correct_top(a);
874 return ret;
875 }
876
BN_set_negative(BIGNUM * a,int b)877 void BN_set_negative(BIGNUM *a, int b)
878 {
879 if (b && !BN_is_zero(a))
880 a->neg = 1;
881 else
882 a->neg = 0;
883 }
884
bn_cmp_words(const BN_ULONG * a,const BN_ULONG * b,int n)885 int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
886 {
887 int i;
888 BN_ULONG aa, bb;
889
890 if (n == 0)
891 return 0;
892
893 aa = a[n - 1];
894 bb = b[n - 1];
895 if (aa != bb)
896 return ((aa > bb) ? 1 : -1);
897 for (i = n - 2; i >= 0; i--) {
898 aa = a[i];
899 bb = b[i];
900 if (aa != bb)
901 return ((aa > bb) ? 1 : -1);
902 }
903 return 0;
904 }
905
906 /*
907 * Here follows a specialised variants of bn_cmp_words(). It has the
908 * capability of performing the operation on arrays of different sizes. The
909 * sizes of those arrays is expressed through cl, which is the common length
910 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
911 * two lengths, calculated as len(a)-len(b). All lengths are the number of
912 * BN_ULONGs...
913 */
914
bn_cmp_part_words(const BN_ULONG * a,const BN_ULONG * b,int cl,int dl)915 int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
916 {
917 int n, i;
918 n = cl - 1;
919
920 if (dl < 0) {
921 for (i = dl; i < 0; i++) {
922 if (b[n - i] != 0)
923 return -1; /* a < b */
924 }
925 }
926 if (dl > 0) {
927 for (i = dl; i > 0; i--) {
928 if (a[n + i] != 0)
929 return 1; /* a > b */
930 }
931 }
932 return bn_cmp_words(a, b, cl);
933 }
934
935 /*-
936 * Constant-time conditional swap of a and b.
937 * a and b are swapped if condition is not 0.
938 * nwords is the number of words to swap.
939 * Assumes that at least nwords are allocated in both a and b.
940 * Assumes that no more than nwords are used by either a or b.
941 */
BN_consttime_swap(BN_ULONG condition,BIGNUM * a,BIGNUM * b,int nwords)942 void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
943 {
944 BN_ULONG t;
945 int i;
946
947 bn_wcheck_size(a, nwords);
948 bn_wcheck_size(b, nwords);
949
950 condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
951
952 t = (a->top ^ b->top) & condition;
953 a->top ^= t;
954 b->top ^= t;
955
956 t = (a->neg ^ b->neg) & condition;
957 a->neg ^= t;
958 b->neg ^= t;
959
960 /*-
961 * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
962 * is actually to treat it as it's read-only data, and some (if not most)
963 * of it does reside in read-only segment. In other words observation of
964 * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
965 * condition. It would either cause SEGV or effectively cause data
966 * corruption.
967 *
968 * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
969 * preserved.
970 *
971 * BN_FLG_SECURE: must be preserved, because it determines how x->d was
972 * allocated and hence how to free it.
973 *
974 * BN_FLG_CONSTTIME: sufficient to mask and swap
975 *
976 * BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
977 * the data, so the d array may be padded with additional 0 values (i.e.
978 * top could be greater than the minimal value that it could be). We should
979 * be swapping it
980 */
981
982 #define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
983
984 t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
985 a->flags ^= t;
986 b->flags ^= t;
987
988 /* conditionally swap the data */
989 for (i = 0; i < nwords; i++) {
990 t = (a->d[i] ^ b->d[i]) & condition;
991 a->d[i] ^= t;
992 b->d[i] ^= t;
993 }
994 }
995
996 #undef BN_CONSTTIME_SWAP_FLAGS
997
998 /* Bits of security, see SP800-57 */
999
BN_security_bits(int L,int N)1000 int BN_security_bits(int L, int N)
1001 {
1002 int secbits, bits;
1003 if (L >= 15360)
1004 secbits = 256;
1005 else if (L >= 7680)
1006 secbits = 192;
1007 else if (L >= 3072)
1008 secbits = 128;
1009 else if (L >= 2048)
1010 secbits = 112;
1011 else if (L >= 1024)
1012 secbits = 80;
1013 else
1014 return 0;
1015 if (N == -1)
1016 return secbits;
1017 bits = N / 2;
1018 if (bits < 80)
1019 return 0;
1020 return bits >= secbits ? secbits : bits;
1021 }
1022
BN_zero_ex(BIGNUM * a)1023 void BN_zero_ex(BIGNUM *a)
1024 {
1025 a->neg = 0;
1026 a->top = 0;
1027 a->flags &= ~BN_FLG_FIXED_TOP;
1028 }
1029
BN_abs_is_word(const BIGNUM * a,const BN_ULONG w)1030 int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
1031 {
1032 return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
1033 }
1034
BN_is_zero(const BIGNUM * a)1035 int BN_is_zero(const BIGNUM *a)
1036 {
1037 return a->top == 0;
1038 }
1039
BN_is_one(const BIGNUM * a)1040 int BN_is_one(const BIGNUM *a)
1041 {
1042 return BN_abs_is_word(a, 1) && !a->neg;
1043 }
1044
BN_is_word(const BIGNUM * a,const BN_ULONG w)1045 int BN_is_word(const BIGNUM *a, const BN_ULONG w)
1046 {
1047 return BN_abs_is_word(a, w) && (!w || !a->neg);
1048 }
1049
ossl_bn_is_word_fixed_top(const BIGNUM * a,const BN_ULONG w)1050 int ossl_bn_is_word_fixed_top(const BIGNUM *a, const BN_ULONG w)
1051 {
1052 int res, i;
1053 const BN_ULONG *ap = a->d;
1054
1055 if (a->neg || a->top == 0)
1056 return 0;
1057
1058 res = constant_time_select_int(constant_time_eq_bn(ap[0], w), 1, 0);
1059
1060 for (i = 1; i < a->top; i++)
1061 res = constant_time_select_int(constant_time_is_zero_bn(ap[i]),
1062 res, 0);
1063 return res;
1064 }
1065
BN_is_odd(const BIGNUM * a)1066 int BN_is_odd(const BIGNUM *a)
1067 {
1068 return (a->top > 0) && (a->d[0] & 1);
1069 }
1070
BN_is_negative(const BIGNUM * a)1071 int BN_is_negative(const BIGNUM *a)
1072 {
1073 return (a->neg != 0);
1074 }
1075
BN_to_montgomery(BIGNUM * r,const BIGNUM * a,BN_MONT_CTX * mont,BN_CTX * ctx)1076 int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
1077 BN_CTX *ctx)
1078 {
1079 return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
1080 }
1081
BN_with_flags(BIGNUM * dest,const BIGNUM * b,int flags)1082 void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
1083 {
1084 dest->d = b->d;
1085 dest->top = b->top;
1086 dest->dmax = b->dmax;
1087 dest->neg = b->neg;
1088 dest->flags = ((dest->flags & BN_FLG_MALLOCED)
1089 | (b->flags & ~BN_FLG_MALLOCED)
1090 | BN_FLG_STATIC_DATA | flags);
1091 }
1092
BN_GENCB_new(void)1093 BN_GENCB *BN_GENCB_new(void)
1094 {
1095 BN_GENCB *ret;
1096
1097 if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL)
1098 return NULL;
1099
1100 return ret;
1101 }
1102
BN_GENCB_free(BN_GENCB * cb)1103 void BN_GENCB_free(BN_GENCB *cb)
1104 {
1105 if (cb == NULL)
1106 return;
1107 OPENSSL_free(cb);
1108 }
1109
BN_set_flags(BIGNUM * b,int n)1110 void BN_set_flags(BIGNUM *b, int n)
1111 {
1112 b->flags |= n;
1113 }
1114
BN_get_flags(const BIGNUM * b,int n)1115 int BN_get_flags(const BIGNUM *b, int n)
1116 {
1117 return b->flags & n;
1118 }
1119
1120 /* 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)1121 void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
1122 void *cb_arg)
1123 {
1124 BN_GENCB *tmp_gencb = gencb;
1125 tmp_gencb->ver = 1;
1126 tmp_gencb->arg = cb_arg;
1127 tmp_gencb->cb.cb_1 = callback;
1128 }
1129
1130 /* 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)1131 void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
1132 void *cb_arg)
1133 {
1134 BN_GENCB *tmp_gencb = gencb;
1135 tmp_gencb->ver = 2;
1136 tmp_gencb->arg = cb_arg;
1137 tmp_gencb->cb.cb_2 = callback;
1138 }
1139
BN_GENCB_get_arg(BN_GENCB * cb)1140 void *BN_GENCB_get_arg(BN_GENCB *cb)
1141 {
1142 return cb->arg;
1143 }
1144
bn_wexpand(BIGNUM * a,int words)1145 BIGNUM *bn_wexpand(BIGNUM *a, int words)
1146 {
1147 return (words <= a->dmax) ? a : bn_expand2(a, words);
1148 }
1149
bn_correct_top_consttime(BIGNUM * a)1150 void bn_correct_top_consttime(BIGNUM *a)
1151 {
1152 int j, atop;
1153 BN_ULONG limb;
1154 unsigned int mask;
1155
1156 for (j = 0, atop = 0; j < a->dmax; j++) {
1157 limb = a->d[j];
1158 limb |= 0 - limb;
1159 limb >>= BN_BITS2 - 1;
1160 limb = 0 - limb;
1161 mask = (unsigned int)limb;
1162 mask &= constant_time_msb(j - a->top);
1163 atop = constant_time_select_int(mask, j + 1, atop);
1164 }
1165
1166 mask = constant_time_eq_int(atop, 0);
1167 a->top = atop;
1168 a->neg = constant_time_select_int(mask, 0, a->neg);
1169 a->flags &= ~BN_FLG_FIXED_TOP;
1170 }
1171
bn_correct_top(BIGNUM * a)1172 void bn_correct_top(BIGNUM *a)
1173 {
1174 BN_ULONG *ftl;
1175 int tmp_top = a->top;
1176
1177 if (tmp_top > 0) {
1178 for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
1179 ftl--;
1180 if (*ftl != 0)
1181 break;
1182 }
1183 a->top = tmp_top;
1184 }
1185 if (a->top == 0)
1186 a->neg = 0;
1187 a->flags &= ~BN_FLG_FIXED_TOP;
1188 bn_pollute(a);
1189 }
1190