2 * Copyright 1995-2022 The OpenSSL Project Authors. All Rights Reserved.
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
12 #include "internal/cryptlib.h"
13 #include "internal/endian.h"
15 #include <openssl/opensslconf.h>
16 #include "internal/constant_time.h"
18 /* This stuff appears to be completely unused, so is deprecated */
19 #ifndef OPENSSL_NO_DEPRECATED_0_9_8
21 * For a 32 bit machine
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) */
39 void BN_set_params(int mult, int high, int low, int mont)
42 if (mult > (int)(sizeof(int) * 8) - 1)
43 mult = sizeof(int) * 8 - 1;
45 bn_limit_num = 1 << mult;
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;
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;
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;
67 int BN_get_params(int which)
72 return bn_limit_bits_high;
74 return bn_limit_bits_low;
76 return bn_limit_bits_mont;
82 const BIGNUM *BN_value_one(void)
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 };
92 * Old Visual Studio ARM compiler miscompiles BN_num_bits_word()
93 * https://mta.openssl.org/pipermail/openssl-users/2018-August/008465.html
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)
100 int BN_num_bits_word(BN_ULONG l)
107 mask = (0 - x) & BN_MASK2;
108 mask = (0 - (mask >> (BN_BITS2 - 1)));
114 mask = (0 - x) & BN_MASK2;
115 mask = (0 - (mask >> (BN_BITS2 - 1)));
120 mask = (0 - x) & BN_MASK2;
121 mask = (0 - (mask >> (BN_BITS2 - 1)));
126 mask = (0 - x) & BN_MASK2;
127 mask = (0 - (mask >> (BN_BITS2 - 1)));
132 mask = (0 - x) & BN_MASK2;
133 mask = (0 - (mask >> (BN_BITS2 - 1)));
138 mask = (0 - x) & BN_MASK2;
139 mask = (0 - (mask >> (BN_BITS2 - 1)));
144 #ifdef MS_BROKEN_BN_num_bits_word
145 # pragma optimize("", on)
149 * This function still leaks `a->dmax`: it's caller's responsibility to
150 * expand the input `a` in advance to a public length.
153 int bn_num_bits_consttime(const BIGNUM *a)
156 unsigned int mask, past_i;
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 */
163 ret += BN_BITS2 & (~mask & ~past_i);
164 ret += BN_num_bits_word(a->d[j]) & mask;
166 past_i |= mask; /* past_i will become 0xff..ff after i==j */
170 * if BN_is_zero(a) => i is -1 and ret contains garbage, so we mask the
173 mask = ~(constant_time_eq_int(i, ((int)-1)));
178 int BN_num_bits(const BIGNUM *a)
183 if (a->flags & BN_FLG_CONSTTIME) {
185 * We assume that BIGNUMs flagged as CONSTTIME have also been expanded
186 * so that a->dmax is not leaking secret information.
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
193 return bn_num_bits_consttime(a);
199 return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
202 static void bn_free_d(BIGNUM *a, int clear)
204 if (BN_get_flags(a, BN_FLG_SECURE))
205 OPENSSL_secure_clear_free(a->d, a->dmax * sizeof(a->d[0]));
207 OPENSSL_clear_free(a->d, a->dmax * sizeof(a->d[0]));
213 void BN_clear_free(BIGNUM *a)
217 if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA))
219 if (BN_get_flags(a, BN_FLG_MALLOCED)) {
220 OPENSSL_cleanse(a, sizeof(*a));
225 void BN_free(BIGNUM *a)
229 if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
231 if (a->flags & BN_FLG_MALLOCED)
235 void bn_init(BIGNUM *a)
247 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
248 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
251 ret->flags = BN_FLG_MALLOCED;
256 BIGNUM *BN_secure_new(void)
258 BIGNUM *ret = BN_new();
260 ret->flags |= BN_FLG_SECURE;
264 /* This is used by bn_expand2() */
265 /* The caller MUST check that words > b->dmax before calling this */
266 static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
270 if (words > (INT_MAX / (4 * BN_BITS2))) {
271 ERR_raise(ERR_LIB_BN, BN_R_BIGNUM_TOO_LONG);
274 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
275 ERR_raise(ERR_LIB_BN, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
278 if (BN_get_flags(b, BN_FLG_SECURE))
279 a = OPENSSL_secure_zalloc(words * sizeof(*a));
281 a = OPENSSL_zalloc(words * sizeof(*a));
283 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
287 assert(b->top <= words);
289 memcpy(a, b->d, sizeof(*a) * b->top);
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,
302 BIGNUM *bn_expand2(BIGNUM *b, int words)
304 if (words > b->dmax) {
305 BN_ULONG *a = bn_expand_internal(b, words);
317 BIGNUM *BN_dup(const BIGNUM *a)
325 t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
328 if (!BN_copy(t, a)) {
336 BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
342 bn_words = BN_get_flags(b, BN_FLG_CONSTTIME) ? b->dmax : b->top;
346 if (bn_wexpand(a, bn_words) == NULL)
350 memcpy(a->d, b->d, sizeof(b->d[0]) * bn_words);
354 a->flags |= b->flags & BN_FLG_FIXED_TOP;
359 #define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
363 #define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
365 void BN_swap(BIGNUM *a, BIGNUM *b)
367 int flags_old_a, flags_old_b;
369 int tmp_top, tmp_dmax, tmp_neg;
374 flags_old_a = a->flags;
375 flags_old_b = b->flags;
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);
398 void BN_clear(BIGNUM *a)
404 OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
407 a->flags &= ~BN_FLG_FIXED_TOP;
410 BN_ULONG BN_get_word(const BIGNUM *a)
414 else if (a->top == 1)
420 int BN_set_word(BIGNUM *a, BN_ULONG w)
423 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
427 a->top = (w ? 1 : 0);
428 a->flags &= ~BN_FLG_FIXED_TOP;
433 typedef enum {BIG, LITTLE} endianess_t;
434 typedef enum {SIGNED, UNSIGNED} signedness_t;
436 static BIGNUM *bin2bn(const unsigned char *s, int len, BIGNUM *ret,
437 endianess_t endianess, signedness_t signedness)
440 const unsigned char *s2;
442 int neg = 0, xor = 0, carry = 0;
454 * The loop that does the work iterates from least to most
455 * significant BIGNUM chunk, so we adapt parameters to transfer
456 * input bytes accordingly.
458 if (endianess == LITTLE) {
469 /* Take note of the signedness of the input bytes*/
470 if (signedness == SIGNED) {
471 neg = !!(*s2 & 0x80);
472 xor = neg ? 0xff : 0x00;
477 * Skip leading sign extensions (the value of |xor|).
478 * This is the only spot where |s2| and |inc2| are used.
480 for ( ; len > 0 && *s2 == xor; s2 += inc2, len--)
484 * If there was a set of 0xff, we backtrack one byte unless the next
485 * one has a sign bit, as the last 0xff is then part of the actual
486 * number, rather then a mere sign extension.
489 if (len == 0 || !(*s2 & 0x80))
492 /* If it was all zeros, we're done */
497 n = ((len - 1) / BN_BYTES) + 1; /* Number of resulting bignum chunks */
498 if (!ossl_assert(bn_wexpand(ret, (int)n) != NULL)) {
504 for (i = 0; n-- > 0; i++) {
505 BN_ULONG l = 0; /* Accumulator */
506 unsigned int m = 0; /* Offset in a bignum chunk, in bits */
508 for (; len > 0 && m < BN_BYTES * 8; len--, s += inc, m += 8) {
509 BN_ULONG byte_xored = *s ^ xor;
510 BN_ULONG byte = (byte_xored + carry) & 0xff;
512 carry = byte_xored > byte; /* Implicit 1 or 0 */
518 * need to call this due to clear byte at top if avoiding having the top
519 * bit set (-ve number)
525 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
527 return bin2bn(s, len, ret, BIG, UNSIGNED);
530 BIGNUM *BN_signed_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
532 return bin2bn(s, len, ret, BIG, SIGNED);
535 static int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen,
536 endianess_t endianess, signedness_t signedness)
540 int xor = 0, carry = 0, ext = 0;
541 size_t i, lasti, j, atop, mask;
545 * In case |a| is fixed-top, BN_num_bits can return bogus length,
546 * but it's assumed that fixed-top inputs ought to be "nominated"
547 * even for padded output, so it works out...
550 n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
552 /* Take note of the signedness of the bignum */
553 if (signedness == SIGNED) {
554 xor = a->neg ? 0xff : 0x00;
558 * if |n * 8 == n|, then the MSbit is set, otherwise unset.
559 * We must compensate with one extra byte if that doesn't
560 * correspond to the signedness of the bignum with regards
564 ? !a->neg /* MSbit set on nonnegative bignum */
565 : a->neg; /* MSbit unset on negative bignum */
570 } else if (tolen < n + ext) { /* uncommon/unlike case */
573 bn_correct_top(&temp);
574 n8 = BN_num_bits(&temp);
575 n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
580 /* Swipe through whole available data and don't give away padded zero. */
581 atop = a->dmax * BN_BYTES;
584 memset(to, '\0', tolen);
589 * The loop that does the work iterates from least significant
590 * to most significant BIGNUM limb, so we adapt parameters to
591 * transfer output bytes accordingly.
593 if (endianess == LITTLE) {
597 to += tolen - 1; /* Move to the last byte, not beyond */
601 atop = a->top * BN_BYTES;
602 for (i = 0, j = 0; j < (size_t)tolen; j++) {
603 unsigned char byte, byte_xored;
605 l = a->d[i / BN_BYTES];
606 mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
607 byte = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
608 byte_xored = byte ^ xor;
609 *to = (unsigned char)(byte_xored + carry);
610 carry = byte_xored > *to; /* Implicit 1 or 0 */
612 i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
618 int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
622 return bn2binpad(a, to, tolen, BIG, UNSIGNED);
625 int BN_signed_bn2bin(const BIGNUM *a, unsigned char *to, int tolen)
629 return bn2binpad(a, to, tolen, BIG, SIGNED);
632 int BN_bn2bin(const BIGNUM *a, unsigned char *to)
634 return bn2binpad(a, to, -1, BIG, UNSIGNED);
637 BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
639 return bin2bn(s, len, ret, LITTLE, UNSIGNED);
642 BIGNUM *BN_signed_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
644 return bin2bn(s, len, ret, LITTLE, SIGNED);
647 int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
651 return bn2binpad(a, to, tolen, LITTLE, UNSIGNED);
654 int BN_signed_bn2lebin(const BIGNUM *a, unsigned char *to, int tolen)
658 return bn2binpad(a, to, tolen, LITTLE, SIGNED);
661 BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret)
665 if (IS_LITTLE_ENDIAN)
666 return BN_lebin2bn(s, len, ret);
667 return BN_bin2bn(s, len, ret);
670 BIGNUM *BN_signed_native2bn(const unsigned char *s, int len, BIGNUM *ret)
674 if (IS_LITTLE_ENDIAN)
675 return BN_signed_lebin2bn(s, len, ret);
676 return BN_signed_bin2bn(s, len, ret);
679 int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen)
683 if (IS_LITTLE_ENDIAN)
684 return BN_bn2lebinpad(a, to, tolen);
685 return BN_bn2binpad(a, to, tolen);
688 int BN_signed_bn2native(const BIGNUM *a, unsigned char *to, int tolen)
692 if (IS_LITTLE_ENDIAN)
693 return BN_signed_bn2lebin(a, to, tolen);
694 return BN_signed_bn2bin(a, to, tolen);
697 int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
700 BN_ULONG t1, t2, *ap, *bp;
710 for (i = a->top - 1; i >= 0; i--) {
714 return ((t1 > t2) ? 1 : -1);
719 int BN_cmp(const BIGNUM *a, const BIGNUM *b)
725 if ((a == NULL) || (b == NULL)) {
737 if (a->neg != b->neg) {
755 for (i = a->top - 1; i >= 0; i--) {
766 int BN_set_bit(BIGNUM *a, int n)
776 if (bn_wexpand(a, i + 1) == NULL)
778 for (k = a->top; k < i + 1; k++)
781 a->flags &= ~BN_FLG_FIXED_TOP;
784 a->d[i] |= (((BN_ULONG)1) << j);
789 int BN_clear_bit(BIGNUM *a, int n)
802 a->d[i] &= (~(((BN_ULONG)1) << j));
807 int BN_is_bit_set(const BIGNUM *a, int n)
818 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
821 int BN_mask_bits(BIGNUM *a, int n)
837 a->d[w] &= ~(BN_MASK2 << b);
843 void BN_set_negative(BIGNUM *a, int b)
845 if (b && !BN_is_zero(a))
851 int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
862 return ((aa > bb) ? 1 : -1);
863 for (i = n - 2; i >= 0; i--) {
867 return ((aa > bb) ? 1 : -1);
873 * Here follows a specialised variants of bn_cmp_words(). It has the
874 * capability of performing the operation on arrays of different sizes. The
875 * sizes of those arrays is expressed through cl, which is the common length
876 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
877 * two lengths, calculated as len(a)-len(b). All lengths are the number of
881 int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
887 for (i = dl; i < 0; i++) {
889 return -1; /* a < b */
893 for (i = dl; i > 0; i--) {
895 return 1; /* a > b */
898 return bn_cmp_words(a, b, cl);
902 * Constant-time conditional swap of a and b.
903 * a and b are swapped if condition is not 0.
904 * nwords is the number of words to swap.
905 * Assumes that at least nwords are allocated in both a and b.
906 * Assumes that no more than nwords are used by either a or b.
908 void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
916 bn_wcheck_size(a, nwords);
917 bn_wcheck_size(b, nwords);
919 condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
921 t = (a->top ^ b->top) & condition;
925 t = (a->neg ^ b->neg) & condition;
930 * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
931 * is actually to treat it as it's read-only data, and some (if not most)
932 * of it does reside in read-only segment. In other words observation of
933 * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
934 * condition. It would either cause SEGV or effectively cause data
937 * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
940 * BN_FLG_SECURE: must be preserved, because it determines how x->d was
941 * allocated and hence how to free it.
943 * BN_FLG_CONSTTIME: sufficient to mask and swap
945 * BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
946 * the data, so the d array may be padded with additional 0 values (i.e.
947 * top could be greater than the minimal value that it could be). We should
951 #define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
953 t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
957 /* conditionally swap the data */
958 for (i = 0; i < nwords; i++) {
959 t = (a->d[i] ^ b->d[i]) & condition;
965 #undef BN_CONSTTIME_SWAP_FLAGS
967 /* Bits of security, see SP800-57 */
969 int BN_security_bits(int L, int N)
989 return bits >= secbits ? secbits : bits;
992 void BN_zero_ex(BIGNUM *a)
996 a->flags &= ~BN_FLG_FIXED_TOP;
999 int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
1001 return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
1004 int BN_is_zero(const BIGNUM *a)
1009 int BN_is_one(const BIGNUM *a)
1011 return BN_abs_is_word(a, 1) && !a->neg;
1014 int BN_is_word(const BIGNUM *a, const BN_ULONG w)
1016 return BN_abs_is_word(a, w) && (!w || !a->neg);
1019 int BN_is_odd(const BIGNUM *a)
1021 return (a->top > 0) && (a->d[0] & 1);
1024 int BN_is_negative(const BIGNUM *a)
1026 return (a->neg != 0);
1029 int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
1032 return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
1035 void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
1039 dest->dmax = b->dmax;
1041 dest->flags = ((dest->flags & BN_FLG_MALLOCED)
1042 | (b->flags & ~BN_FLG_MALLOCED)
1043 | BN_FLG_STATIC_DATA | flags);
1046 BN_GENCB *BN_GENCB_new(void)
1050 if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
1051 ERR_raise(ERR_LIB_BN, ERR_R_MALLOC_FAILURE);
1058 void BN_GENCB_free(BN_GENCB *cb)
1065 void BN_set_flags(BIGNUM *b, int n)
1070 int BN_get_flags(const BIGNUM *b, int n)
1072 return b->flags & n;
1075 /* Populate a BN_GENCB structure with an "old"-style callback */
1076 void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
1079 BN_GENCB *tmp_gencb = gencb;
1081 tmp_gencb->arg = cb_arg;
1082 tmp_gencb->cb.cb_1 = callback;
1085 /* Populate a BN_GENCB structure with a "new"-style callback */
1086 void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
1089 BN_GENCB *tmp_gencb = gencb;
1091 tmp_gencb->arg = cb_arg;
1092 tmp_gencb->cb.cb_2 = callback;
1095 void *BN_GENCB_get_arg(BN_GENCB *cb)
1100 BIGNUM *bn_wexpand(BIGNUM *a, int words)
1102 return (words <= a->dmax) ? a : bn_expand2(a, words);
1105 void bn_correct_top(BIGNUM *a)
1108 int tmp_top = a->top;
1111 for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
1120 a->flags &= ~BN_FLG_FIXED_TOP;