2 * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (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"
14 #include <openssl/opensslconf.h>
15 #include "internal/constant_time.h"
17 /* This stuff appears to be completely unused, so is deprecated */
18 #if OPENSSL_API_COMPAT < 0x00908000L
20 * For a 32 bit machine
29 static int bn_limit_bits = 0;
30 static int bn_limit_num = 8; /* (1<<bn_limit_bits) */
31 static int bn_limit_bits_low = 0;
32 static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */
33 static int bn_limit_bits_high = 0;
34 static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */
35 static int bn_limit_bits_mont = 0;
36 static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */
38 void BN_set_params(int mult, int high, int low, int mont)
41 if (mult > (int)(sizeof(int) * 8) - 1)
42 mult = sizeof(int) * 8 - 1;
44 bn_limit_num = 1 << mult;
47 if (high > (int)(sizeof(int) * 8) - 1)
48 high = sizeof(int) * 8 - 1;
49 bn_limit_bits_high = high;
50 bn_limit_num_high = 1 << high;
53 if (low > (int)(sizeof(int) * 8) - 1)
54 low = sizeof(int) * 8 - 1;
55 bn_limit_bits_low = low;
56 bn_limit_num_low = 1 << low;
59 if (mont > (int)(sizeof(int) * 8) - 1)
60 mont = sizeof(int) * 8 - 1;
61 bn_limit_bits_mont = mont;
62 bn_limit_num_mont = 1 << mont;
66 int BN_get_params(int which)
71 return bn_limit_bits_high;
73 return bn_limit_bits_low;
75 return bn_limit_bits_mont;
81 const BIGNUM *BN_value_one(void)
83 static const BN_ULONG data_one = 1L;
84 static const BIGNUM const_one =
85 { (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA };
91 * Old Visual Studio ARM compiler miscompiles BN_num_bits_word()
92 * https://mta.openssl.org/pipermail/openssl-users/2018-August/008465.html
94 #if defined(_MSC_VER) && defined(_ARM_) && defined(_WIN32_WCE) \
95 && _MSC_VER>=1400 && _MSC_VER<1501
96 # define MS_BROKEN_BN_num_bits_word
97 # pragma optimize("", off)
99 int BN_num_bits_word(BN_ULONG l)
106 mask = (0 - x) & BN_MASK2;
107 mask = (0 - (mask >> (BN_BITS2 - 1)));
113 mask = (0 - x) & BN_MASK2;
114 mask = (0 - (mask >> (BN_BITS2 - 1)));
119 mask = (0 - x) & BN_MASK2;
120 mask = (0 - (mask >> (BN_BITS2 - 1)));
125 mask = (0 - x) & BN_MASK2;
126 mask = (0 - (mask >> (BN_BITS2 - 1)));
131 mask = (0 - x) & BN_MASK2;
132 mask = (0 - (mask >> (BN_BITS2 - 1)));
137 mask = (0 - x) & BN_MASK2;
138 mask = (0 - (mask >> (BN_BITS2 - 1)));
143 #ifdef MS_BROKEN_BN_num_bits_word
144 # pragma optimize("", on)
148 * This function still leaks `a->dmax`: it's caller's responsibility to
149 * expand the input `a` in advance to a public length.
152 int bn_num_bits_consttime(const BIGNUM *a)
155 unsigned int mask, past_i;
159 for (j = 0, past_i = 0, ret = 0; j < a->dmax; j++) {
160 mask = constant_time_eq_int(i, j); /* 0xff..ff if i==j, 0x0 otherwise */
162 ret += BN_BITS2 & (~mask & ~past_i);
163 ret += BN_num_bits_word(a->d[j]) & mask;
165 past_i |= mask; /* past_i will become 0xff..ff after i==j */
169 * if BN_is_zero(a) => i is -1 and ret contains garbage, so we mask the
172 mask = ~(constant_time_eq_int(i, ((int)-1)));
177 int BN_num_bits(const BIGNUM *a)
182 if (a->flags & BN_FLG_CONSTTIME) {
184 * We assume that BIGNUMs flagged as CONSTTIME have also been expanded
185 * so that a->dmax is not leaking secret information.
187 * In other words, it's the caller's responsibility to ensure `a` has
188 * been preallocated in advance to a public length if we hit this
192 return bn_num_bits_consttime(a);
198 return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
201 static void bn_free_d(BIGNUM *a, int clear)
203 if (BN_get_flags(a, BN_FLG_SECURE))
204 OPENSSL_secure_clear_free(a->d, a->dmax * sizeof(a->d[0]));
206 OPENSSL_clear_free(a->d, a->dmax * sizeof(a->d[0]));
212 void BN_clear_free(BIGNUM *a)
216 if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA))
218 if (BN_get_flags(a, BN_FLG_MALLOCED)) {
219 OPENSSL_cleanse(a, sizeof(*a));
224 void BN_free(BIGNUM *a)
228 if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
230 if (a->flags & BN_FLG_MALLOCED)
234 void bn_init(BIGNUM *a)
246 if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
247 BNerr(BN_F_BN_NEW, ERR_R_MALLOC_FAILURE);
250 ret->flags = BN_FLG_MALLOCED;
255 BIGNUM *BN_secure_new(void)
257 BIGNUM *ret = BN_new();
259 ret->flags |= BN_FLG_SECURE;
263 /* This is used by bn_expand2() */
264 /* The caller MUST check that words > b->dmax before calling this */
265 static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
269 if (words > (INT_MAX / (4 * BN_BITS2))) {
270 BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_BIGNUM_TOO_LONG);
273 if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
274 BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
277 if (BN_get_flags(b, BN_FLG_SECURE))
278 a = OPENSSL_secure_zalloc(words * sizeof(*a));
280 a = OPENSSL_zalloc(words * sizeof(*a));
282 BNerr(BN_F_BN_EXPAND_INTERNAL, ERR_R_MALLOC_FAILURE);
286 assert(b->top <= words);
288 memcpy(a, b->d, sizeof(*a) * b->top);
294 * This is an internal function that should not be used in applications. It
295 * ensures that 'b' has enough room for a 'words' word number and initialises
296 * any unused part of b->d with leading zeros. It is mostly used by the
297 * various BIGNUM routines. If there is an error, NULL is returned. If not,
301 BIGNUM *bn_expand2(BIGNUM *b, int words)
303 if (words > b->dmax) {
304 BN_ULONG *a = bn_expand_internal(b, words);
316 BIGNUM *BN_dup(const BIGNUM *a)
324 t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
327 if (!BN_copy(t, a)) {
335 BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
341 bn_words = BN_get_flags(b, BN_FLG_CONSTTIME) ? b->dmax : b->top;
345 if (bn_wexpand(a, bn_words) == NULL)
349 memcpy(a->d, b->d, sizeof(b->d[0]) * bn_words);
353 a->flags |= b->flags & BN_FLG_FIXED_TOP;
358 #define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
362 #define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
364 void BN_swap(BIGNUM *a, BIGNUM *b)
366 int flags_old_a, flags_old_b;
368 int tmp_top, tmp_dmax, tmp_neg;
373 flags_old_a = a->flags;
374 flags_old_b = b->flags;
391 a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
392 b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
397 void BN_clear(BIGNUM *a)
403 OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
406 a->flags &= ~BN_FLG_FIXED_TOP;
409 BN_ULONG BN_get_word(const BIGNUM *a)
413 else if (a->top == 1)
419 int BN_set_word(BIGNUM *a, BN_ULONG w)
422 if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
426 a->top = (w ? 1 : 0);
427 a->flags &= ~BN_FLG_FIXED_TOP;
432 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
444 /* Skip leading zero's. */
445 for ( ; len > 0 && *s == 0; s++, len--)
452 i = ((n - 1) / BN_BYTES) + 1;
453 m = ((n - 1) % (BN_BYTES));
454 if (bn_wexpand(ret, (int)i) == NULL) {
462 l = (l << 8L) | *(s++);
470 * need to call this due to clear byte at top if avoiding having the top
471 * bit set (-ve number)
477 typedef enum {big, little} endianess_t;
479 /* ignore negative */
481 int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen, endianess_t endianess)
484 size_t i, lasti, j, atop, mask;
488 * In case |a| is fixed-top, BN_num_bytes can return bogus length,
489 * but it's assumed that fixed-top inputs ought to be "nominated"
490 * even for padded output, so it works out...
495 } else if (tolen < n) { /* uncommon/unlike case */
498 bn_correct_top(&temp);
499 n = BN_num_bytes(&temp);
504 /* Swipe through whole available data and don't give away padded zero. */
505 atop = a->dmax * BN_BYTES;
507 OPENSSL_cleanse(to, tolen);
512 atop = a->top * BN_BYTES;
513 if (endianess == big)
514 to += tolen; /* start from the end of the buffer */
515 for (i = 0, j = 0; j < (size_t)tolen; j++) {
517 l = a->d[i / BN_BYTES];
518 mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
519 val = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
520 if (endianess == big)
524 i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
530 int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
534 return bn2binpad(a, to, tolen, big);
537 int BN_bn2bin(const BIGNUM *a, unsigned char *to)
539 return bn2binpad(a, to, -1, big);
542 BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
555 /* Skip trailing zeroes. */
556 for ( ; len > 0 && s[-1] == 0; s--, len--)
563 i = ((n - 1) / BN_BYTES) + 1;
564 m = ((n - 1) % (BN_BYTES));
565 if (bn_wexpand(ret, (int)i) == NULL) {
582 * need to call this due to clear byte at top if avoiding having the top
583 * bit set (-ve number)
589 int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
593 return bn2binpad(a, to, tolen, little);
596 int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
599 BN_ULONG t1, t2, *ap, *bp;
609 for (i = a->top - 1; i >= 0; i--) {
613 return ((t1 > t2) ? 1 : -1);
618 int BN_cmp(const BIGNUM *a, const BIGNUM *b)
624 if ((a == NULL) || (b == NULL)) {
636 if (a->neg != b->neg) {
654 for (i = a->top - 1; i >= 0; i--) {
665 int BN_set_bit(BIGNUM *a, int n)
675 if (bn_wexpand(a, i + 1) == NULL)
677 for (k = a->top; k < i + 1; k++)
680 a->flags &= ~BN_FLG_FIXED_TOP;
683 a->d[i] |= (((BN_ULONG)1) << j);
688 int BN_clear_bit(BIGNUM *a, int n)
701 a->d[i] &= (~(((BN_ULONG)1) << j));
706 int BN_is_bit_set(const BIGNUM *a, int n)
717 return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
720 int BN_mask_bits(BIGNUM *a, int n)
736 a->d[w] &= ~(BN_MASK2 << b);
742 void BN_set_negative(BIGNUM *a, int b)
744 if (b && !BN_is_zero(a))
750 int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
761 return ((aa > bb) ? 1 : -1);
762 for (i = n - 2; i >= 0; i--) {
766 return ((aa > bb) ? 1 : -1);
772 * Here follows a specialised variants of bn_cmp_words(). It has the
773 * capability of performing the operation on arrays of different sizes. The
774 * sizes of those arrays is expressed through cl, which is the common length
775 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
776 * two lengths, calculated as len(a)-len(b). All lengths are the number of
780 int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
786 for (i = dl; i < 0; i++) {
788 return -1; /* a < b */
792 for (i = dl; i > 0; i--) {
794 return 1; /* a > b */
797 return bn_cmp_words(a, b, cl);
801 * Constant-time conditional swap of a and b.
802 * a and b are swapped if condition is not 0.
803 * nwords is the number of words to swap.
804 * Assumes that at least nwords are allocated in both a and b.
805 * Assumes that no more than nwords are used by either a or b.
807 void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
815 bn_wcheck_size(a, nwords);
816 bn_wcheck_size(b, nwords);
818 condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
820 t = (a->top ^ b->top) & condition;
824 t = (a->neg ^ b->neg) & condition;
829 * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
830 * is actually to treat it as it's read-only data, and some (if not most)
831 * of it does reside in read-only segment. In other words observation of
832 * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
833 * condition. It would either cause SEGV or effectively cause data
836 * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
839 * BN_FLG_SECURE: must be preserved, because it determines how x->d was
840 * allocated and hence how to free it.
842 * BN_FLG_CONSTTIME: sufficient to mask and swap
844 * BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
845 * the data, so the d array may be padded with additional 0 values (i.e.
846 * top could be greater than the minimal value that it could be). We should
850 #define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
852 t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
856 /* conditionally swap the data */
857 for (i = 0; i < nwords; i++) {
858 t = (a->d[i] ^ b->d[i]) & condition;
864 #undef BN_CONSTTIME_SWAP_FLAGS
866 /* Bits of security, see SP800-57 */
868 int BN_security_bits(int L, int N)
888 return bits >= secbits ? secbits : bits;
891 void BN_zero_ex(BIGNUM *a)
895 a->flags &= ~BN_FLG_FIXED_TOP;
898 int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
900 return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
903 int BN_is_zero(const BIGNUM *a)
908 int BN_is_one(const BIGNUM *a)
910 return BN_abs_is_word(a, 1) && !a->neg;
913 int BN_is_word(const BIGNUM *a, const BN_ULONG w)
915 return BN_abs_is_word(a, w) && (!w || !a->neg);
918 int BN_is_odd(const BIGNUM *a)
920 return (a->top > 0) && (a->d[0] & 1);
923 int BN_is_negative(const BIGNUM *a)
925 return (a->neg != 0);
928 int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
931 return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
934 void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
938 dest->dmax = b->dmax;
940 dest->flags = ((dest->flags & BN_FLG_MALLOCED)
941 | (b->flags & ~BN_FLG_MALLOCED)
942 | BN_FLG_STATIC_DATA | flags);
945 BN_GENCB *BN_GENCB_new(void)
949 if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
950 BNerr(BN_F_BN_GENCB_NEW, ERR_R_MALLOC_FAILURE);
957 void BN_GENCB_free(BN_GENCB *cb)
964 void BN_set_flags(BIGNUM *b, int n)
969 int BN_get_flags(const BIGNUM *b, int n)
974 /* Populate a BN_GENCB structure with an "old"-style callback */
975 void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
978 BN_GENCB *tmp_gencb = gencb;
980 tmp_gencb->arg = cb_arg;
981 tmp_gencb->cb.cb_1 = callback;
984 /* Populate a BN_GENCB structure with a "new"-style callback */
985 void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
988 BN_GENCB *tmp_gencb = gencb;
990 tmp_gencb->arg = cb_arg;
991 tmp_gencb->cb.cb_2 = callback;
994 void *BN_GENCB_get_arg(BN_GENCB *cb)
999 BIGNUM *bn_wexpand(BIGNUM *a, int words)
1001 return (words <= a->dmax) ? a : bn_expand2(a, words);
1004 void bn_correct_top(BIGNUM *a)
1007 int tmp_top = a->top;
1010 for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
1019 a->flags &= ~BN_FLG_FIXED_TOP;