ref: e86bd6a50933e99899d63de755d81b9805827a15
dir: /third_party/boringssl/src/crypto/fipsmodule/bn/shift.c/
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.] */
#include <openssl/bn.h>
#include <string.h>
#include <openssl/err.h>
#include <openssl/type_check.h>
#include "internal.h"
int BN_lshift(BIGNUM *r, const BIGNUM *a, int n) {
int i, nw, lb, rb;
BN_ULONG *t, *f;
BN_ULONG l;
if (n < 0) {
OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
return 0;
}
r->neg = a->neg;
nw = n / BN_BITS2;
if (!bn_wexpand(r, a->width + nw + 1)) {
return 0;
}
lb = n % BN_BITS2;
rb = BN_BITS2 - lb;
f = a->d;
t = r->d;
t[a->width + nw] = 0;
if (lb == 0) {
for (i = a->width - 1; i >= 0; i--) {
t[nw + i] = f[i];
}
} else {
for (i = a->width - 1; i >= 0; i--) {
l = f[i];
t[nw + i + 1] |= l >> rb;
t[nw + i] = l << lb;
}
}
OPENSSL_memset(t, 0, nw * sizeof(t[0]));
r->width = a->width + nw + 1;
bn_set_minimal_width(r);
return 1;
}
int BN_lshift1(BIGNUM *r, const BIGNUM *a) {
BN_ULONG *ap, *rp, t, c;
int i;
if (r != a) {
r->neg = a->neg;
if (!bn_wexpand(r, a->width + 1)) {
return 0;
}
r->width = a->width;
} else {
if (!bn_wexpand(r, a->width + 1)) {
return 0;
}
}
ap = a->d;
rp = r->d;
c = 0;
for (i = 0; i < a->width; i++) {
t = *(ap++);
*(rp++) = (t << 1) | c;
c = t >> (BN_BITS2 - 1);
}
if (c) {
*rp = 1;
r->width++;
}
return 1;
}
void bn_rshift_words(BN_ULONG *r, const BN_ULONG *a, unsigned shift,
size_t num) {
unsigned shift_bits = shift % BN_BITS2;
size_t shift_words = shift / BN_BITS2;
if (shift_words >= num) {
OPENSSL_memset(r, 0, num * sizeof(BN_ULONG));
return;
}
if (shift_bits == 0) {
OPENSSL_memmove(r, a + shift_words, (num - shift_words) * sizeof(BN_ULONG));
} else {
for (size_t i = shift_words; i < num - 1; i++) {
r[i - shift_words] =
(a[i] >> shift_bits) | (a[i + 1] << (BN_BITS2 - shift_bits));
}
r[num - 1 - shift_words] = a[num - 1] >> shift_bits;
}
OPENSSL_memset(r + num - shift_words, 0, shift_words * sizeof(BN_ULONG));
}
int BN_rshift(BIGNUM *r, const BIGNUM *a, int n) {
if (n < 0) {
OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
return 0;
}
if (!bn_wexpand(r, a->width)) {
return 0;
}
bn_rshift_words(r->d, a->d, n, a->width);
r->neg = a->neg;
r->width = a->width;
bn_set_minimal_width(r);
return 1;
}
int bn_rshift_secret_shift(BIGNUM *r, const BIGNUM *a, unsigned n,
BN_CTX *ctx) {
int ret = 0;
BN_CTX_start(ctx);
BIGNUM *tmp = BN_CTX_get(ctx);
if (tmp == NULL ||
!BN_copy(r, a) ||
!bn_wexpand(tmp, r->width)) {
goto err;
}
// Shift conditionally by powers of two.
unsigned max_bits = BN_BITS2 * r->width;
for (unsigned i = 0; (max_bits >> i) != 0; i++) {
BN_ULONG mask = (n >> i) & 1;
mask = 0 - mask;
bn_rshift_words(tmp->d, r->d, 1u << i, r->width);
bn_select_words(r->d, mask, tmp->d /* apply shift */,
r->d /* ignore shift */, r->width);
}
ret = 1;
err:
BN_CTX_end(ctx);
return ret;
}
void bn_rshift1_words(BN_ULONG *r, const BN_ULONG *a, size_t num) {
if (num == 0) {
return;
}
for (size_t i = 0; i < num - 1; i++) {
r[i] = (a[i] >> 1) | (a[i + 1] << (BN_BITS2 - 1));
}
r[num - 1] = a[num - 1] >> 1;
}
int BN_rshift1(BIGNUM *r, const BIGNUM *a) {
if (!bn_wexpand(r, a->width)) {
return 0;
}
bn_rshift1_words(r->d, a->d, a->width);
r->width = a->width;
r->neg = a->neg;
bn_set_minimal_width(r);
return 1;
}
int BN_set_bit(BIGNUM *a, int n) {
if (n < 0) {
return 0;
}
int i = n / BN_BITS2;
int j = n % BN_BITS2;
if (a->width <= i) {
if (!bn_wexpand(a, i + 1)) {
return 0;
}
for (int k = a->width; k < i + 1; k++) {
a->d[k] = 0;
}
a->width = i + 1;
}
a->d[i] |= (((BN_ULONG)1) << j);
return 1;
}
int BN_clear_bit(BIGNUM *a, int n) {
int i, j;
if (n < 0) {
return 0;
}
i = n / BN_BITS2;
j = n % BN_BITS2;
if (a->width <= i) {
return 0;
}
a->d[i] &= (~(((BN_ULONG)1) << j));
bn_set_minimal_width(a);
return 1;
}
int bn_is_bit_set_words(const BN_ULONG *a, size_t num, unsigned bit) {
unsigned i = bit / BN_BITS2;
unsigned j = bit % BN_BITS2;
if (i >= num) {
return 0;
}
return (a[i] >> j) & 1;
}
int BN_is_bit_set(const BIGNUM *a, int n) {
if (n < 0) {
return 0;
}
return bn_is_bit_set_words(a->d, a->width, n);
}
int BN_mask_bits(BIGNUM *a, int n) {
if (n < 0) {
return 0;
}
int w = n / BN_BITS2;
int b = n % BN_BITS2;
if (w >= a->width) {
return 1;
}
if (b == 0) {
a->width = w;
} else {
a->width = w + 1;
a->d[w] &= ~(BN_MASK2 << b);
}
bn_set_minimal_width(a);
return 1;
}
static int bn_count_low_zero_bits_word(BN_ULONG l) {
OPENSSL_STATIC_ASSERT(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
"crypto_word_t is too small");
OPENSSL_STATIC_ASSERT(sizeof(int) <= sizeof(crypto_word_t),
"crypto_word_t is too small");
OPENSSL_STATIC_ASSERT(BN_BITS2 == sizeof(BN_ULONG) * 8,
"BN_ULONG has padding bits");
// C has very bizarre rules for types smaller than an int.
OPENSSL_STATIC_ASSERT(sizeof(BN_ULONG) >= sizeof(int),
"BN_ULONG gets promoted to int");
crypto_word_t mask;
int bits = 0;
#if BN_BITS2 > 32
// Check if the lower half of |x| are all zero.
mask = constant_time_is_zero_w(l << (BN_BITS2 - 32));
// If the lower half is all zeros, it is included in the bit count and we
// count the upper half. Otherwise, we count the lower half.
bits += 32 & mask;
l = constant_time_select_w(mask, l >> 32, l);
#endif
// The remaining blocks are analogous iterations at lower powers of two.
mask = constant_time_is_zero_w(l << (BN_BITS2 - 16));
bits += 16 & mask;
l = constant_time_select_w(mask, l >> 16, l);
mask = constant_time_is_zero_w(l << (BN_BITS2 - 8));
bits += 8 & mask;
l = constant_time_select_w(mask, l >> 8, l);
mask = constant_time_is_zero_w(l << (BN_BITS2 - 4));
bits += 4 & mask;
l = constant_time_select_w(mask, l >> 4, l);
mask = constant_time_is_zero_w(l << (BN_BITS2 - 2));
bits += 2 & mask;
l = constant_time_select_w(mask, l >> 2, l);
mask = constant_time_is_zero_w(l << (BN_BITS2 - 1));
bits += 1 & mask;
return bits;
}
int BN_count_low_zero_bits(const BIGNUM *bn) {
OPENSSL_STATIC_ASSERT(sizeof(BN_ULONG) <= sizeof(crypto_word_t),
"crypto_word_t is too small");
OPENSSL_STATIC_ASSERT(sizeof(int) <= sizeof(crypto_word_t),
"crypto_word_t is too small");
int ret = 0;
crypto_word_t saw_nonzero = 0;
for (int i = 0; i < bn->width; i++) {
crypto_word_t nonzero = ~constant_time_is_zero_w(bn->d[i]);
crypto_word_t first_nonzero = ~saw_nonzero & nonzero;
saw_nonzero |= nonzero;
int bits = bn_count_low_zero_bits_word(bn->d[i]);
ret |= first_nonzero & (i * BN_BITS2 + bits);
}
// If got to the end of |bn| and saw no non-zero words, |bn| is zero. |ret|
// will then remain zero.
return ret;
}