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openssl/crypto/bn/bn_lib.c
Tomas Mraz 2d285fa873 Make ossl_gen_deterministic_nonce_rfc6979() constant time 
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24265)
2024-05-02 09:16:36 +02:00

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/*
* Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <assert.h>
#include <limits.h>
#include "internal/cryptlib.h"
#include "internal/endian.h"
#include "bn_local.h"
#include <openssl/opensslconf.h>
#include "internal/constant_time.h"
/* This stuff appears to be completely unused, so is deprecated */
#ifndef OPENSSL_NO_DEPRECATED_0_9_8
/*-
* For a 32 bit machine
* 2 - 4 == 128
* 3 - 8 == 256
* 4 - 16 == 512
* 5 - 32 == 1024
* 6 - 64 == 2048
* 7 - 128 == 4096
* 8 - 256 == 8192
*/
static int bn_limit_bits = 0;
static int bn_limit_num = 8; /* (1<<bn_limit_bits) */
static int bn_limit_bits_low = 0;
static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */
static int bn_limit_bits_high = 0;
static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */
static int bn_limit_bits_mont = 0;
static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */
void BN_set_params(int mult, int high, int low, int mont)
{
if (mult >= 0) {
if (mult > (int)(sizeof(int) * 8) - 1)
mult = sizeof(int) * 8 - 1;
bn_limit_bits = mult;
bn_limit_num = 1 << mult;
}
if (high >= 0) {
if (high > (int)(sizeof(int) * 8) - 1)
high = sizeof(int) * 8 - 1;
bn_limit_bits_high = high;
bn_limit_num_high = 1 << high;
}
if (low >= 0) {
if (low > (int)(sizeof(int) * 8) - 1)
low = sizeof(int) * 8 - 1;
bn_limit_bits_low = low;
bn_limit_num_low = 1 << low;
}
if (mont >= 0) {
if (mont > (int)(sizeof(int) * 8) - 1)
mont = sizeof(int) * 8 - 1;
bn_limit_bits_mont = mont;
bn_limit_num_mont = 1 << mont;
}
}
int BN_get_params(int which)
{
if (which == 0)
return bn_limit_bits;
else if (which == 1)
return bn_limit_bits_high;
else if (which == 2)
return bn_limit_bits_low;
else if (which == 3)
return bn_limit_bits_mont;
else
return 0;
}
#endif
const BIGNUM *BN_value_one(void)
{
static const BN_ULONG data_one = 1L;
static const BIGNUM const_one =
{ (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA };
return &const_one;
}
/*
* Old Visual Studio ARM compiler miscompiles BN_num_bits_word()
* https://mta.openssl.org/pipermail/openssl-users/2018-August/008465.html
*/
#if defined(_MSC_VER) && defined(_ARM_) && defined(_WIN32_WCE) \
&& _MSC_VER>=1400 && _MSC_VER<1501
# define MS_BROKEN_BN_num_bits_word
# pragma optimize("", off)
#endif
int BN_num_bits_word(BN_ULONG l)
{
BN_ULONG x, mask;
int bits = (l != 0);
#if BN_BITS2 > 32
x = l >> 32;
mask = (0 - x) & BN_MASK2;
mask = (0 - (mask >> (BN_BITS2 - 1)));
bits += 32 & mask;
l ^= (x ^ l) & mask;
#endif
x = l >> 16;
mask = (0 - x) & BN_MASK2;
mask = (0 - (mask >> (BN_BITS2 - 1)));
bits += 16 & mask;
l ^= (x ^ l) & mask;
x = l >> 8;
mask = (0 - x) & BN_MASK2;
mask = (0 - (mask >> (BN_BITS2 - 1)));
bits += 8 & mask;
l ^= (x ^ l) & mask;
x = l >> 4;
mask = (0 - x) & BN_MASK2;
mask = (0 - (mask >> (BN_BITS2 - 1)));
bits += 4 & mask;
l ^= (x ^ l) & mask;
x = l >> 2;
mask = (0 - x) & BN_MASK2;
mask = (0 - (mask >> (BN_BITS2 - 1)));
bits += 2 & mask;
l ^= (x ^ l) & mask;
x = l >> 1;
mask = (0 - x) & BN_MASK2;
mask = (0 - (mask >> (BN_BITS2 - 1)));
bits += 1 & mask;
return bits;
}
#ifdef MS_BROKEN_BN_num_bits_word
# pragma optimize("", on)
#endif
/*
* This function still leaks `a->dmax`: it's caller's responsibility to
* expand the input `a` in advance to a public length.
*/
static ossl_inline
int bn_num_bits_consttime(const BIGNUM *a)
{
int j, ret;
unsigned int mask, past_i;
int i = a->top - 1;
bn_check_top(a);
for (j = 0, past_i = 0, ret = 0; j < a->dmax; j++) {
mask = constant_time_eq_int(i, j); /* 0xff..ff if i==j, 0x0 otherwise */
ret += BN_BITS2 & (~mask & ~past_i);
ret += BN_num_bits_word(a->d[j]) & mask;
past_i |= mask; /* past_i will become 0xff..ff after i==j */
}
/*
* if BN_is_zero(a) => i is -1 and ret contains garbage, so we mask the
* final result.
*/
mask = ~(constant_time_eq_int(i, ((int)-1)));
return ret & mask;
}
int BN_num_bits(const BIGNUM *a)
{
int i = a->top - 1;
bn_check_top(a);
if (a->flags & BN_FLG_CONSTTIME) {
/*
* We assume that BIGNUMs flagged as CONSTTIME have also been expanded
* so that a->dmax is not leaking secret information.
*
* In other words, it's the caller's responsibility to ensure `a` has
* been preallocated in advance to a public length if we hit this
* branch.
*
*/
return bn_num_bits_consttime(a);
}
if (BN_is_zero(a))
return 0;
return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
}
static void bn_free_d(BIGNUM *a, int clear)
{
if (BN_get_flags(a, BN_FLG_SECURE))
OPENSSL_secure_clear_free(a->d, a->dmax * sizeof(a->d[0]));
else if (clear != 0)
OPENSSL_clear_free(a->d, a->dmax * sizeof(a->d[0]));
else
OPENSSL_free(a->d);
}
void BN_clear_free(BIGNUM *a)
{
if (a == NULL)
return;
if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA))
bn_free_d(a, 1);
if (BN_get_flags(a, BN_FLG_MALLOCED)) {
OPENSSL_cleanse(a, sizeof(*a));
OPENSSL_free(a);
}
}
void BN_free(BIGNUM *a)
{
if (a == NULL)
return;
if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
bn_free_d(a, 0);
if (a->flags & BN_FLG_MALLOCED)
OPENSSL_free(a);
}
void bn_init(BIGNUM *a)
{
static BIGNUM nilbn;
*a = nilbn;
bn_check_top(a);
}
BIGNUM *BN_new(void)
{
BIGNUM *ret;
if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL)
return NULL;
ret->flags = BN_FLG_MALLOCED;
bn_check_top(ret);
return ret;
}
BIGNUM *BN_secure_new(void)
{
BIGNUM *ret = BN_new();
if (ret != NULL)
ret->flags |= BN_FLG_SECURE;
return ret;
}
/* This is used by bn_expand2() */
/* The caller MUST check that words > b->dmax before calling this */
static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
{
BN_ULONG *a = NULL;
if (words > (INT_MAX / (4 * BN_BITS2))) {
ERR_raise(ERR_LIB_BN, BN_R_BIGNUM_TOO_LONG);
return NULL;
}
if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
ERR_raise(ERR_LIB_BN, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
return NULL;
}
if (BN_get_flags(b, BN_FLG_SECURE))
a = OPENSSL_secure_zalloc(words * sizeof(*a));
else
a = OPENSSL_zalloc(words * sizeof(*a));
if (a == NULL)
return NULL;
assert(b->top <= words);
if (b->top > 0)
memcpy(a, b->d, sizeof(*a) * b->top);
return a;
}
/*
* This is an internal function that should not be used in applications. It
* ensures that 'b' has enough room for a 'words' word number and initialises
* any unused part of b->d with leading zeros. It is mostly used by the
* various BIGNUM routines. If there is an error, NULL is returned. If not,
* 'b' is returned.
*/
BIGNUM *bn_expand2(BIGNUM *b, int words)
{
if (words > b->dmax) {
BN_ULONG *a = bn_expand_internal(b, words);
if (!a)
return NULL;
if (b->d != NULL)
bn_free_d(b, 1);
b->d = a;
b->dmax = words;
}
return b;
}
BIGNUM *BN_dup(const BIGNUM *a)
{
BIGNUM *t;
if (a == NULL)
return NULL;
bn_check_top(a);
t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
if (t == NULL)
return NULL;
if (!BN_copy(t, a)) {
BN_free(t);
return NULL;
}
bn_check_top(t);
return t;
}
BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
{
int bn_words;
bn_check_top(b);
bn_words = BN_get_flags(b, BN_FLG_CONSTTIME) ? b->dmax : b->top;
if (a == b)
return a;
if (bn_wexpand(a, bn_words) == NULL)
return NULL;
if (b->top > 0)
memcpy(a->d, b->d, sizeof(b->d[0]) * bn_words);
a->neg = b->neg;
a->top = b->top;
a->flags |= b->flags & BN_FLG_FIXED_TOP;
bn_check_top(a);
return a;
}
#define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
| BN_FLG_CONSTTIME \
| BN_FLG_SECURE \
| BN_FLG_FIXED_TOP))
#define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
void BN_swap(BIGNUM *a, BIGNUM *b)
{
int flags_old_a, flags_old_b;
BN_ULONG *tmp_d;
int tmp_top, tmp_dmax, tmp_neg;
bn_check_top(a);
bn_check_top(b);
flags_old_a = a->flags;
flags_old_b = b->flags;
tmp_d = a->d;
tmp_top = a->top;
tmp_dmax = a->dmax;
tmp_neg = a->neg;
a->d = b->d;
a->top = b->top;
a->dmax = b->dmax;
a->neg = b->neg;
b->d = tmp_d;
b->top = tmp_top;
b->dmax = tmp_dmax;
b->neg = tmp_neg;
a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
bn_check_top(a);
bn_check_top(b);
}
void BN_clear(BIGNUM *a)
{
if (a == NULL)
return;
bn_check_top(a);
if (a->d != NULL)
OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
a->neg = 0;
a->top = 0;
a->flags &= ~BN_FLG_FIXED_TOP;
}
BN_ULONG BN_get_word(const BIGNUM *a)
{
if (a->top > 1)
return BN_MASK2;
else if (a->top == 1)
return a->d[0];
/* a->top == 0 */
return 0;
}
int BN_set_word(BIGNUM *a, BN_ULONG w)
{
bn_check_top(a);
if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
return 0;
a->neg = 0;
a->d[0] = w;
a->top = (w ? 1 : 0);
a->flags &= ~BN_FLG_FIXED_TOP;
bn_check_top(a);
return 1;
}
typedef enum {BIG, LITTLE} endianness_t;
typedef enum {SIGNED, UNSIGNED} signedness_t;
static BIGNUM *bin2bn(const unsigned char *s, int len, BIGNUM *ret,
endianness_t endianness, signedness_t signedness)
{
int inc;
const unsigned char *s2;
int inc2;
int neg = 0, xor = 0, carry = 0;
unsigned int i;
unsigned int n;
BIGNUM *bn = NULL;
/* Negative length is not acceptable */
if (len < 0)
return NULL;
if (ret == NULL)
ret = bn = BN_new();
if (ret == NULL)
return NULL;
bn_check_top(ret);
/*
* If the input has no bits, the number is considered zero.
* This makes calls with s==NULL and len==0 safe.
*/
if (len == 0) {
BN_clear(ret);
return ret;
}
/*
* The loop that does the work iterates from least to most
* significant BIGNUM chunk, so we adapt parameters to transfer
* input bytes accordingly.
*/
if (endianness == LITTLE) {
s2 = s + len - 1;
inc2 = -1;
inc = 1;
} else {
s2 = s;
inc2 = 1;
inc = -1;
s += len - 1;
}
/* Take note of the signedness of the input bytes*/
if (signedness == SIGNED) {
neg = !!(*s2 & 0x80);
xor = neg ? 0xff : 0x00;
carry = neg;
}
/*
* Skip leading sign extensions (the value of |xor|).
* This is the only spot where |s2| and |inc2| are used.
*/
for ( ; len > 0 && *s2 == xor; s2 += inc2, len--)
continue;
/*
* If there was a set of 0xff, we backtrack one byte unless the next
* one has a sign bit, as the last 0xff is then part of the actual
* number, rather then a mere sign extension.
*/
if (xor == 0xff) {
if (len == 0 || !(*s2 & 0x80))
len++;
}
/* If it was all zeros, we're done */
if (len == 0) {
ret->top = 0;
return ret;
}
n = ((len - 1) / BN_BYTES) + 1; /* Number of resulting bignum chunks */
if (bn_wexpand(ret, (int)n) == NULL) {
BN_free(bn);
return NULL;
}
ret->top = n;
ret->neg = neg;
for (i = 0; n-- > 0; i++) {
BN_ULONG l = 0; /* Accumulator */
unsigned int m = 0; /* Offset in a bignum chunk, in bits */
for (; len > 0 && m < BN_BYTES * 8; len--, s += inc, m += 8) {
BN_ULONG byte_xored = *s ^ xor;
BN_ULONG byte = (byte_xored + carry) & 0xff;
carry = byte_xored > byte; /* Implicit 1 or 0 */
l |= (byte << m);
}
ret->d[i] = l;
}
/*
* need to call this due to clear byte at top if avoiding having the top
* bit set (-ve number)
*/
bn_correct_top(ret);
return ret;
}
BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
{
return bin2bn(s, len, ret, BIG, UNSIGNED);
}
BIGNUM *BN_signed_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
{
return bin2bn(s, len, ret, BIG, SIGNED);
}
static int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen,
endianness_t endianness, signedness_t signedness)
{
int inc;
int n, n8;
int xor = 0, carry = 0, ext = 0;
size_t i, lasti, j, atop, mask;
BN_ULONG l;
/*
* In case |a| is fixed-top, BN_num_bits can return bogus length,
* but it's assumed that fixed-top inputs ought to be "nominated"
* even for padded output, so it works out...
*/
n8 = BN_num_bits(a);
n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
/* Take note of the signedness of the bignum */
if (signedness == SIGNED) {
xor = a->neg ? 0xff : 0x00;
carry = a->neg;
/*
* if |n * 8 == n|, then the MSbit is set, otherwise unset.
* We must compensate with one extra byte if that doesn't
* correspond to the signedness of the bignum with regards
* to 2's complement.
*/
ext = (n * 8 == n8)
? !a->neg /* MSbit set on nonnegative bignum */
: a->neg; /* MSbit unset on negative bignum */
}
if (tolen == -1) {
tolen = n + ext;
} else if (tolen < n + ext) { /* uncommon/unlike case */
BIGNUM temp = *a;
bn_correct_top(&temp);
n8 = BN_num_bits(&temp);
n = (n8 + 7) / 8; /* This is what BN_num_bytes() does */
if (tolen < n + ext)
return -1;
}
/* Swipe through whole available data and don't give away padded zero. */
atop = a->dmax * BN_BYTES;
if (atop == 0) {
if (tolen != 0)
memset(to, '\0', tolen);
return tolen;
}
/*
* The loop that does the work iterates from least significant
* to most significant BIGNUM limb, so we adapt parameters to
* transfer output bytes accordingly.
*/
if (endianness == LITTLE) {
inc = 1;
} else {
inc = -1;
to += tolen - 1; /* Move to the last byte, not beyond */
}
lasti = atop - 1;
atop = a->top * BN_BYTES;
for (i = 0, j = 0; j < (size_t)tolen; j++) {
unsigned char byte, byte_xored;
l = a->d[i / BN_BYTES];
mask = 0 - ((j - atop) >> (8 * sizeof(i) - 1));
byte = (unsigned char)(l >> (8 * (i % BN_BYTES)) & mask);
byte_xored = byte ^ xor;
*to = (unsigned char)(byte_xored + carry);
carry = byte_xored > *to; /* Implicit 1 or 0 */
to += inc;
i += (i - lasti) >> (8 * sizeof(i) - 1); /* stay on last limb */
}
return tolen;
}
int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
{
if (tolen < 0)
return -1;
return bn2binpad(a, to, tolen, BIG, UNSIGNED);
}
int BN_signed_bn2bin(const BIGNUM *a, unsigned char *to, int tolen)
{
if (tolen < 0)
return -1;
return bn2binpad(a, to, tolen, BIG, SIGNED);
}
int BN_bn2bin(const BIGNUM *a, unsigned char *to)
{
return bn2binpad(a, to, -1, BIG, UNSIGNED);
}
BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
{
return bin2bn(s, len, ret, LITTLE, UNSIGNED);
}
BIGNUM *BN_signed_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
{
return bin2bn(s, len, ret, LITTLE, SIGNED);
}
int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
{
if (tolen < 0)
return -1;
return bn2binpad(a, to, tolen, LITTLE, UNSIGNED);
}
int BN_signed_bn2lebin(const BIGNUM *a, unsigned char *to, int tolen)
{
if (tolen < 0)
return -1;
return bn2binpad(a, to, tolen, LITTLE, SIGNED);
}
BIGNUM *BN_native2bn(const unsigned char *s, int len, BIGNUM *ret)
{
DECLARE_IS_ENDIAN;
if (IS_LITTLE_ENDIAN)
return BN_lebin2bn(s, len, ret);
return BN_bin2bn(s, len, ret);
}
BIGNUM *BN_signed_native2bn(const unsigned char *s, int len, BIGNUM *ret)
{
DECLARE_IS_ENDIAN;
if (IS_LITTLE_ENDIAN)
return BN_signed_lebin2bn(s, len, ret);
return BN_signed_bin2bn(s, len, ret);
}
int BN_bn2nativepad(const BIGNUM *a, unsigned char *to, int tolen)
{
DECLARE_IS_ENDIAN;
if (IS_LITTLE_ENDIAN)
return BN_bn2lebinpad(a, to, tolen);
return BN_bn2binpad(a, to, tolen);
}
int BN_signed_bn2native(const BIGNUM *a, unsigned char *to, int tolen)
{
DECLARE_IS_ENDIAN;
if (IS_LITTLE_ENDIAN)
return BN_signed_bn2lebin(a, to, tolen);
return BN_signed_bn2bin(a, to, tolen);
}
int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
{
int i;
BN_ULONG t1, t2, *ap, *bp;
ap = a->d;
bp = b->d;
if (BN_get_flags(a, BN_FLG_CONSTTIME)
&& a->top == b->top) {
int res = 0;
for (i = 0; i < b->top; i++) {
res = constant_time_select_int(constant_time_lt_bn(ap[i], bp[i]),
-1, res);
res = constant_time_select_int(constant_time_lt_bn(bp[i], ap[i]),
1, res);
}
return res;
}
bn_check_top(a);
bn_check_top(b);
i = a->top - b->top;
if (i != 0)
return i;
for (i = a->top - 1; i >= 0; i--) {
t1 = ap[i];
t2 = bp[i];
if (t1 != t2)
return ((t1 > t2) ? 1 : -1);
}
return 0;
}
int BN_cmp(const BIGNUM *a, const BIGNUM *b)
{
int i;
int gt, lt;
BN_ULONG t1, t2;
if ((a == NULL) || (b == NULL)) {
if (a != NULL)
return -1;
else if (b != NULL)
return 1;
else
return 0;
}
bn_check_top(a);
bn_check_top(b);
if (a->neg != b->neg) {
if (a->neg)
return -1;
else
return 1;
}
if (a->neg == 0) {
gt = 1;
lt = -1;
} else {
gt = -1;
lt = 1;
}
if (a->top > b->top)
return gt;
if (a->top < b->top)
return lt;
for (i = a->top - 1; i >= 0; i--) {
t1 = a->d[i];
t2 = b->d[i];
if (t1 > t2)
return gt;
if (t1 < t2)
return lt;
}
return 0;
}
int BN_set_bit(BIGNUM *a, int n)
{
int i, j, k;
if (n < 0)
return 0;
i = n / BN_BITS2;
j = n % BN_BITS2;
if (a->top <= i) {
if (bn_wexpand(a, i + 1) == NULL)
return 0;
for (k = a->top; k < i + 1; k++)
a->d[k] = 0;
a->top = i + 1;
a->flags &= ~BN_FLG_FIXED_TOP;
}
a->d[i] |= (((BN_ULONG)1) << j);
bn_check_top(a);
return 1;
}
int BN_clear_bit(BIGNUM *a, int n)
{
int i, j;
bn_check_top(a);
if (n < 0)
return 0;
i = n / BN_BITS2;
j = n % BN_BITS2;
if (a->top <= i)
return 0;
a->d[i] &= (~(((BN_ULONG)1) << j));
bn_correct_top(a);
return 1;
}
int BN_is_bit_set(const BIGNUM *a, int n)
{
int i, j;
bn_check_top(a);
if (n < 0)
return 0;
i = n / BN_BITS2;
j = n % BN_BITS2;
if (a->top <= i)
return 0;
return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
}
int ossl_bn_mask_bits_fixed_top(BIGNUM *a, int n)
{
int b, w;
if (n < 0)
return 0;
w = n / BN_BITS2;
b = n % BN_BITS2;
if (w >= a->top)
return 0;
if (b == 0)
a->top = w;
else {
a->top = w + 1;
a->d[w] &= ~(BN_MASK2 << b);
}
a->flags |= BN_FLG_FIXED_TOP;
return 1;
}
int BN_mask_bits(BIGNUM *a, int n)
{
int ret;
bn_check_top(a);
ret = ossl_bn_mask_bits_fixed_top(a, n);
if (ret)
bn_correct_top(a);
return ret;
}
void BN_set_negative(BIGNUM *a, int b)
{
if (b && !BN_is_zero(a))
a->neg = 1;
else
a->neg = 0;
}
int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
{
int i;
BN_ULONG aa, bb;
if (n == 0)
return 0;
aa = a[n - 1];
bb = b[n - 1];
if (aa != bb)
return ((aa > bb) ? 1 : -1);
for (i = n - 2; i >= 0; i--) {
aa = a[i];
bb = b[i];
if (aa != bb)
return ((aa > bb) ? 1 : -1);
}
return 0;
}
/*
* Here follows a specialised variants of bn_cmp_words(). It has the
* capability of performing the operation on arrays of different sizes. The
* sizes of those arrays is expressed through cl, which is the common length
* ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
* two lengths, calculated as len(a)-len(b). All lengths are the number of
* BN_ULONGs...
*/
int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
{
int n, i;
n = cl - 1;
if (dl < 0) {
for (i = dl; i < 0; i++) {
if (b[n - i] != 0)
return -1; /* a < b */
}
}
if (dl > 0) {
for (i = dl; i > 0; i--) {
if (a[n + i] != 0)
return 1; /* a > b */
}
}
return bn_cmp_words(a, b, cl);
}
/*-
* Constant-time conditional swap of a and b.
* a and b are swapped if condition is not 0.
* nwords is the number of words to swap.
* Assumes that at least nwords are allocated in both a and b.
* Assumes that no more than nwords are used by either a or b.
*/
void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
{
BN_ULONG t;
int i;
bn_wcheck_size(a, nwords);
bn_wcheck_size(b, nwords);
condition = ((~condition & ((condition - 1))) >> (BN_BITS2 - 1)) - 1;
t = (a->top ^ b->top) & condition;
a->top ^= t;
b->top ^= t;
t = (a->neg ^ b->neg) & condition;
a->neg ^= t;
b->neg ^= t;
/*-
* BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention
* is actually to treat it as it's read-only data, and some (if not most)
* of it does reside in read-only segment. In other words observation of
* BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal
* condition. It would either cause SEGV or effectively cause data
* corruption.
*
* BN_FLG_MALLOCED: refers to BN structure itself, and hence must be
* preserved.
*
* BN_FLG_SECURE: must be preserved, because it determines how x->d was
* allocated and hence how to free it.
*
* BN_FLG_CONSTTIME: sufficient to mask and swap
*
* BN_FLG_FIXED_TOP: indicates that we haven't called bn_correct_top() on
* the data, so the d array may be padded with additional 0 values (i.e.
* top could be greater than the minimal value that it could be). We should
* be swapping it
*/
#define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME | BN_FLG_FIXED_TOP)
t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition;
a->flags ^= t;
b->flags ^= t;
/* conditionally swap the data */
for (i = 0; i < nwords; i++) {
t = (a->d[i] ^ b->d[i]) & condition;
a->d[i] ^= t;
b->d[i] ^= t;
}
}
#undef BN_CONSTTIME_SWAP_FLAGS
/* Bits of security, see SP800-57 */
int BN_security_bits(int L, int N)
{
int secbits, bits;
if (L >= 15360)
secbits = 256;
else if (L >= 7680)
secbits = 192;
else if (L >= 3072)
secbits = 128;
else if (L >= 2048)
secbits = 112;
else if (L >= 1024)
secbits = 80;
else
return 0;
if (N == -1)
return secbits;
bits = N / 2;
if (bits < 80)
return 0;
return bits >= secbits ? secbits : bits;
}
void BN_zero_ex(BIGNUM *a)
{
a->neg = 0;
a->top = 0;
a->flags &= ~BN_FLG_FIXED_TOP;
}
int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
{
return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
}
int BN_is_zero(const BIGNUM *a)
{
return a->top == 0;
}
int BN_is_one(const BIGNUM *a)
{
return BN_abs_is_word(a, 1) && !a->neg;
}
int BN_is_word(const BIGNUM *a, const BN_ULONG w)
{
return BN_abs_is_word(a, w) && (!w || !a->neg);
}
int ossl_bn_is_word_fixed_top(const BIGNUM *a, const BN_ULONG w)
{
int res, i;
const BN_ULONG *ap = a->d;
if (a->neg || a->top == 0)
return 0;
res = constant_time_select_int(constant_time_eq_bn(ap[0], w), 1, 0);
for (i = 1; i < a->top; i++)
res = constant_time_select_int(constant_time_is_zero_bn(ap[i]),
res, 0);
return res;
}
int BN_is_odd(const BIGNUM *a)
{
return (a->top > 0) && (a->d[0] & 1);
}
int BN_is_negative(const BIGNUM *a)
{
return (a->neg != 0);
}
int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
BN_CTX *ctx)
{
return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
}
void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
{
dest->d = b->d;
dest->top = b->top;
dest->dmax = b->dmax;
dest->neg = b->neg;
dest->flags = ((dest->flags & BN_FLG_MALLOCED)
| (b->flags & ~BN_FLG_MALLOCED)
| BN_FLG_STATIC_DATA | flags);
}
BN_GENCB *BN_GENCB_new(void)
{
BN_GENCB *ret;
if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL)
return NULL;
return ret;
}
void BN_GENCB_free(BN_GENCB *cb)
{
if (cb == NULL)
return;
OPENSSL_free(cb);
}
void BN_set_flags(BIGNUM *b, int n)
{
b->flags |= n;
}
int BN_get_flags(const BIGNUM *b, int n)
{
return b->flags & n;
}
/* Populate a BN_GENCB structure with an "old"-style callback */
void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
void *cb_arg)
{
BN_GENCB *tmp_gencb = gencb;
tmp_gencb->ver = 1;
tmp_gencb->arg = cb_arg;
tmp_gencb->cb.cb_1 = callback;
}
/* Populate a BN_GENCB structure with a "new"-style callback */
void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
void *cb_arg)
{
BN_GENCB *tmp_gencb = gencb;
tmp_gencb->ver = 2;
tmp_gencb->arg = cb_arg;
tmp_gencb->cb.cb_2 = callback;
}
void *BN_GENCB_get_arg(BN_GENCB *cb)
{
return cb->arg;
}
BIGNUM *bn_wexpand(BIGNUM *a, int words)
{
return (words <= a->dmax) ? a : bn_expand2(a, words);
}
void bn_correct_top_consttime(BIGNUM *a)
{
int j, atop;
BN_ULONG limb;
unsigned int mask;
for (j = 0, atop = 0; j < a->dmax; j++) {
limb = a->d[j];
limb |= 0 - limb;
limb >>= BN_BITS2 - 1;
limb = 0 - limb;
mask = (unsigned int)limb;
mask &= constant_time_msb(j - a->top);
atop = constant_time_select_int(mask, j + 1, atop);
}
mask = constant_time_eq_int(atop, 0);
a->top = atop;
a->neg = constant_time_select_int(mask, 0, a->neg);
a->flags &= ~BN_FLG_FIXED_TOP;
}
void bn_correct_top(BIGNUM *a)
{
BN_ULONG *ftl;
int tmp_top = a->top;
if (tmp_top > 0) {
for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
ftl--;
if (*ftl != 0)
break;
}
a->top = tmp_top;
}
if (a->top == 0)
a->neg = 0;
a->flags &= ~BN_FLG_FIXED_TOP;
bn_pollute(a);
}
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