kris/boringssl
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
6f564afbdd
boringssl/crypto/fipsmodule/bn/mul.c
David Benjamin c7b6e0a664 Don't leak widths in bn_mod_mul_montgomery_fallback. 
The fallback functions still themselves leak, but I've left TODOs there.

This only affects BN_mod_mul_montgomery on platforms where we don't use
the bn_mul_mont assembly, but BN_mul additionally affects the final
multiplication in RSA CRT.

Bug: 232
Change-Id: Ia1ae16162c38e10c056b76d6b2afbed67f1a5e16
Reviewed-on: https://boringssl-review.googlesource.com/25260
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-02-05 23:57:03 +00:00

939 lines
23 KiB
C
Raw Blame History

/* 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 <assert.h>
#include <string.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include "internal.h"
#include "../../internal.h"
#define BN_MUL_RECURSIVE_SIZE_NORMAL 16
#define BN_SQR_RECURSIVE_SIZE_NORMAL BN_MUL_RECURSIVE_SIZE_NORMAL
static void bn_mul_normal(BN_ULONG *r, const BN_ULONG *a, size_t na,
const BN_ULONG *b, size_t nb) {
if (na < nb) {
size_t itmp = na;
na = nb;
nb = itmp;
const BN_ULONG *ltmp = a;
a = b;
b = ltmp;
}
BN_ULONG *rr = &(r[na]);
if (nb == 0) {
OPENSSL_memset(r, 0, na * sizeof(BN_ULONG));
return;
}
rr[0] = bn_mul_words(r, a, na, b[0]);
for (;;) {
if (--nb == 0) {
return;
}
rr[1] = bn_mul_add_words(&(r[1]), a, na, b[1]);
if (--nb == 0) {
return;
}
rr[2] = bn_mul_add_words(&(r[2]), a, na, b[2]);
if (--nb == 0) {
return;
}
rr[3] = bn_mul_add_words(&(r[3]), a, na, b[3]);
if (--nb == 0) {
return;
}
rr[4] = bn_mul_add_words(&(r[4]), a, na, b[4]);
rr += 4;
r += 4;
b += 4;
}
}
#if !defined(OPENSSL_X86) || defined(OPENSSL_NO_ASM)
// Here follows specialised variants of bn_add_words() and bn_sub_words(). They
// have the property performing operations on arrays of different sizes. The
// sizes of those arrays is expressed through cl, which is the common length (
// basicall, 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... For the operations that require a result array as parameter,
// it must have the length cl+abs(dl). These functions should probably end up
// in bn_asm.c as soon as there are assembler counterparts for the systems that
// use assembler files.
static BN_ULONG bn_sub_part_words(BN_ULONG *r, const BN_ULONG *a,
const BN_ULONG *b, int cl, int dl) {
BN_ULONG c, t;
assert(cl >= 0);
c = bn_sub_words(r, a, b, cl);
if (dl == 0) {
return c;
}
r += cl;
a += cl;
b += cl;
if (dl < 0) {
for (;;) {
t = b[0];
r[0] = 0 - t - c;
if (t != 0) {
c = 1;
}
if (++dl >= 0) {
break;
}
t = b[1];
r[1] = 0 - t - c;
if (t != 0) {
c = 1;
}
if (++dl >= 0) {
break;
}
t = b[2];
r[2] = 0 - t - c;
if (t != 0) {
c = 1;
}
if (++dl >= 0) {
break;
}
t = b[3];
r[3] = 0 - t - c;
if (t != 0) {
c = 1;
}
if (++dl >= 0) {
break;
}
b += 4;
r += 4;
}
} else {
int save_dl = dl;
while (c) {
t = a[0];
r[0] = t - c;
if (t != 0) {
c = 0;
}
if (--dl <= 0) {
break;
}
t = a[1];
r[1] = t - c;
if (t != 0) {
c = 0;
}
if (--dl <= 0) {
break;
}
t = a[2];
r[2] = t - c;
if (t != 0) {
c = 0;
}
if (--dl <= 0) {
break;
}
t = a[3];
r[3] = t - c;
if (t != 0) {
c = 0;
}
if (--dl <= 0) {
break;
}
save_dl = dl;
a += 4;
r += 4;
}
if (dl > 0) {
if (save_dl > dl) {
switch (save_dl - dl) {
case 1:
r[1] = a[1];
if (--dl <= 0) {
break;
}
OPENSSL_FALLTHROUGH;
case 2:
r[2] = a[2];
if (--dl <= 0) {
break;
}
OPENSSL_FALLTHROUGH;
case 3:
r[3] = a[3];
if (--dl <= 0) {
break;
}
}
a += 4;
r += 4;
}
}
if (dl > 0) {
for (;;) {
r[0] = a[0];
if (--dl <= 0) {
break;
}
r[1] = a[1];
if (--dl <= 0) {
break;
}
r[2] = a[2];
if (--dl <= 0) {
break;
}
r[3] = a[3];
if (--dl <= 0) {
break;
}
a += 4;
r += 4;
}
}
}
return c;
}
#else
// On other platforms the function is defined in asm.
BN_ULONG bn_sub_part_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b,
int cl, int dl);
#endif
// Karatsuba recursive multiplication algorithm
// (cf. Knuth, The Art of Computer Programming, Vol. 2)
// r is 2*n2 words in size,
// a and b are both n2 words in size.
// n2 must be a power of 2.
// We multiply and return the result.
// t must be 2*n2 words in size
// We calculate
// a[0]*b[0]
// a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
// a[1]*b[1]
// dnX may not be positive, but n2/2+dnX has to be
static void bn_mul_recursive(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b,
int n2, int dna, int dnb, BN_ULONG *t) {
int n = n2 / 2, c1, c2;
int tna = n + dna, tnb = n + dnb;
unsigned int neg, zero;
BN_ULONG ln, lo, *p;
// Only call bn_mul_comba 8 if n2 == 8 and the
// two arrays are complete [steve]
if (n2 == 8 && dna == 0 && dnb == 0) {
bn_mul_comba8(r, a, b);
return;
}
// Else do normal multiply
if (n2 < BN_MUL_RECURSIVE_SIZE_NORMAL) {
bn_mul_normal(r, a, n2 + dna, b, n2 + dnb);
if ((dna + dnb) < 0) {
OPENSSL_memset(&r[2 * n2 + dna + dnb], 0,
sizeof(BN_ULONG) * -(dna + dnb));
}
return;
}
// TODO(davidben): This function is not constant-time, but should be. See
// https://crbug.com/boringssl/234.
// r=(a[0]-a[1])*(b[1]-b[0])
c1 = bn_cmp_part_words(a, &(a[n]), tna, n - tna);
c2 = bn_cmp_part_words(&(b[n]), b, tnb, tnb - n);
zero = neg = 0;
switch (c1 * 3 + c2) {
case -4:
bn_sub_part_words(t, &(a[n]), a, tna, tna - n); // -
bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); // -
break;
case -3:
zero = 1;
break;
case -2:
bn_sub_part_words(t, &(a[n]), a, tna, tna - n); // -
bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); // +
neg = 1;
break;
case -1:
case 0:
case 1:
zero = 1;
break;
case 2:
bn_sub_part_words(t, a, &(a[n]), tna, n - tna); // +
bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); // -
neg = 1;
break;
case 3:
zero = 1;
break;
case 4:
bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
break;
}
if (n == 4 && dna == 0 && dnb == 0) {
// XXX: bn_mul_comba4 could take extra args to do this well
if (!zero) {
bn_mul_comba4(&(t[n2]), t, &(t[n]));
} else {
OPENSSL_memset(&(t[n2]), 0, 8 * sizeof(BN_ULONG));
}
bn_mul_comba4(r, a, b);
bn_mul_comba4(&(r[n2]), &(a[n]), &(b[n]));
} else if (n == 8 && dna == 0 && dnb == 0) {
// XXX: bn_mul_comba8 could take extra args to do this well
if (!zero) {
bn_mul_comba8(&(t[n2]), t, &(t[n]));
} else {
OPENSSL_memset(&(t[n2]), 0, 16 * sizeof(BN_ULONG));
}
bn_mul_comba8(r, a, b);
bn_mul_comba8(&(r[n2]), &(a[n]), &(b[n]));
} else {
p = &(t[n2 * 2]);
if (!zero) {
bn_mul_recursive(&(t[n2]), t, &(t[n]), n, 0, 0, p);
} else {
OPENSSL_memset(&(t[n2]), 0, n2 * sizeof(BN_ULONG));
}
bn_mul_recursive(r, a, b, n, 0, 0, p);
bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]), n, dna, dnb, p);
}
// t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
// r[10] holds (a[0]*b[0])
// r[32] holds (b[1]*b[1])
c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
if (neg) {
// if t[32] is negative
c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
} else {
// Might have a carry
c1 += (int)(bn_add_words(&(t[n2]), &(t[n2]), t, n2));
}
// t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
// r[10] holds (a[0]*b[0])
// r[32] holds (b[1]*b[1])
// c1 holds the carry bits
c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
if (c1) {
p = &(r[n + n2]);
lo = *p;
ln = lo + c1;
*p = ln;
// The overflow will stop before we over write
// words we should not overwrite
if (ln < (BN_ULONG)c1) {
do {
p++;
lo = *p;
ln = lo + 1;
*p = ln;
} while (ln == 0);
}
}
}
// n+tn is the word length
// t needs to be n*4 is size, as does r
// tnX may not be negative but less than n
static void bn_mul_part_recursive(BN_ULONG *r, const BN_ULONG *a,
const BN_ULONG *b, int n, int tna, int tnb,
BN_ULONG *t) {
int i, j, n2 = n * 2;
int c1, c2, neg;
BN_ULONG ln, lo, *p;
if (n < 8) {
bn_mul_normal(r, a, n + tna, b, n + tnb);
return;
}
// TODO(davidben): This function is not constant-time, but should be. See
// https://crbug.com/boringssl/234.
// r=(a[0]-a[1])*(b[1]-b[0])
c1 = bn_cmp_part_words(a, &(a[n]), tna, n - tna);
c2 = bn_cmp_part_words(&(b[n]), b, tnb, tnb - n);
neg = 0;
switch (c1 * 3 + c2) {
case -4:
bn_sub_part_words(t, &(a[n]), a, tna, tna - n); // -
bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); // -
break;
case -3:
// break;
case -2:
bn_sub_part_words(t, &(a[n]), a, tna, tna - n); // -
bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n); // +
neg = 1;
break;
case -1:
case 0:
case 1:
// break;
case 2:
bn_sub_part_words(t, a, &(a[n]), tna, n - tna); // +
bn_sub_part_words(&(t[n]), b, &(b[n]), tnb, n - tnb); // -
neg = 1;
break;
case 3:
// break;
case 4:
bn_sub_part_words(t, a, &(a[n]), tna, n - tna);
bn_sub_part_words(&(t[n]), &(b[n]), b, tnb, tnb - n);
break;
}
if (n == 8) {
bn_mul_comba8(&(t[n2]), t, &(t[n]));
bn_mul_comba8(r, a, b);
bn_mul_normal(&(r[n2]), &(a[n]), tna, &(b[n]), tnb);
OPENSSL_memset(&(r[n2 + tna + tnb]), 0, sizeof(BN_ULONG) * (n2 - tna - tnb));
} else {
p = &(t[n2 * 2]);
bn_mul_recursive(&(t[n2]), t, &(t[n]), n, 0, 0, p);
bn_mul_recursive(r, a, b, n, 0, 0, p);
i = n / 2;
// If there is only a bottom half to the number,
// just do it
if (tna > tnb) {
j = tna - i;
} else {
j = tnb - i;
}
if (j == 0) {
bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]), i, tna - i, tnb - i, p);
OPENSSL_memset(&(r[n2 + i * 2]), 0, sizeof(BN_ULONG) * (n2 - i * 2));
} else if (j > 0) {
// eg, n == 16, i == 8 and tn == 11
bn_mul_part_recursive(&(r[n2]), &(a[n]), &(b[n]), i, tna - i, tnb - i, p);
OPENSSL_memset(&(r[n2 + tna + tnb]), 0,
sizeof(BN_ULONG) * (n2 - tna - tnb));
} else {
// (j < 0) eg, n == 16, i == 8 and tn == 5
OPENSSL_memset(&(r[n2]), 0, sizeof(BN_ULONG) * n2);
if (tna < BN_MUL_RECURSIVE_SIZE_NORMAL &&
tnb < BN_MUL_RECURSIVE_SIZE_NORMAL) {
bn_mul_normal(&(r[n2]), &(a[n]), tna, &(b[n]), tnb);
} else {
for (;;) {
i /= 2;
// these simplified conditions work
// exclusively because difference
// between tna and tnb is 1 or 0
if (i < tna || i < tnb) {
bn_mul_part_recursive(&(r[n2]), &(a[n]), &(b[n]), i, tna - i,
tnb - i, p);
break;
} else if (i == tna || i == tnb) {
bn_mul_recursive(&(r[n2]), &(a[n]), &(b[n]), i, tna - i, tnb - i,
p);
break;
}
}
}
}
}
// t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
// r[10] holds (a[0]*b[0])
// r[32] holds (b[1]*b[1])
c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
if (neg) {
// if t[32] is negative
c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
} else {
// Might have a carry
c1 += (int)(bn_add_words(&(t[n2]), &(t[n2]), t, n2));
}
// t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
// r[10] holds (a[0]*b[0])
// r[32] holds (b[1]*b[1])
// c1 holds the carry bits
c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
if (c1) {
p = &(r[n + n2]);
lo = *p;
ln = lo + c1;
*p = ln;
// The overflow will stop before we over write
// words we should not overwrite
if (ln < (BN_ULONG)c1) {
do {
p++;
lo = *p;
ln = lo + 1;
*p = ln;
} while (ln == 0);
}
}
}
// bn_mul_impl implements |BN_mul| and |bn_mul_fixed|. Note this function breaks
// |BIGNUM| invariants and may return a negative zero. This is handled by the
// callers.
static int bn_mul_impl(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
BN_CTX *ctx) {
int ret = 0;
int top, al, bl;
BIGNUM *rr;
int i;
BIGNUM *t = NULL;
int j = 0, k;
al = a->width;
bl = b->width;
if ((al == 0) || (bl == 0)) {
BN_zero(r);
return 1;
}
top = al + bl;
BN_CTX_start(ctx);
if ((r == a) || (r == b)) {
if ((rr = BN_CTX_get(ctx)) == NULL) {
goto err;
}
} else {
rr = r;
}
rr->neg = a->neg ^ b->neg;
i = al - bl;
if (i == 0) {
if (al == 8) {
if (!bn_wexpand(rr, 16)) {
goto err;
}
rr->width = 16;
bn_mul_comba8(rr->d, a->d, b->d);
goto end;
}
}
static const int kMulNormalSize = 16;
if (al >= kMulNormalSize && bl >= kMulNormalSize) {
if (i >= -1 && i <= 1) {
/* Find out the power of two lower or equal
to the longest of the two numbers */
if (i >= 0) {
j = BN_num_bits_word((BN_ULONG)al);
}
if (i == -1) {
j = BN_num_bits_word((BN_ULONG)bl);
}
j = 1 << (j - 1);
assert(j <= al || j <= bl);
k = j + j;
t = BN_CTX_get(ctx);
if (t == NULL) {
goto err;
}
if (al > j || bl > j) {
if (!bn_wexpand(t, k * 4)) {
goto err;
}
if (!bn_wexpand(rr, k * 4)) {
goto err;
}
bn_mul_part_recursive(rr->d, a->d, b->d, j, al - j, bl - j, t->d);
} else {
// al <= j || bl <= j
if (!bn_wexpand(t, k * 2)) {
goto err;
}
if (!bn_wexpand(rr, k * 2)) {
goto err;
}
bn_mul_recursive(rr->d, a->d, b->d, j, al - j, bl - j, t->d);
}
rr->width = top;
goto end;
}
}
if (!bn_wexpand(rr, top)) {
goto err;
}
rr->width = top;
bn_mul_normal(rr->d, a->d, al, b->d, bl);
end:
if (r != rr && !BN_copy(r, rr)) {
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
return ret;
}
int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx) {
if (!bn_mul_impl(r, a, b, ctx)) {
return 0;
}
// This additionally fixes any negative zeros created by |bn_mul_impl|.
bn_set_minimal_width(r);
return 1;
}
int bn_mul_fixed(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx) {
// Prevent negative zeros.
if (a->neg || b->neg) {
OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
return 0;
}
return bn_mul_impl(r, a, b, ctx);
}
int bn_mul_small(BN_ULONG *r, size_t num_r, const BN_ULONG *a, size_t num_a,
const BN_ULONG *b, size_t num_b) {
if (num_r != num_a + num_b) {
OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
// TODO(davidben): Should this call |bn_mul_comba4| too? |BN_mul| does not
// hit that code.
if (num_a == 8 && num_b == 8) {
bn_mul_comba8(r, a, b);
} else {
bn_mul_normal(r, a, num_a, b, num_b);
}
return 1;
}
// tmp must have 2*n words
static void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, size_t n,
BN_ULONG *tmp) {
if (n == 0) {
return;
}
size_t max = n * 2;
const BN_ULONG *ap = a;
BN_ULONG *rp = r;
rp[0] = rp[max - 1] = 0;
rp++;
// Compute the contribution of a[i] * a[j] for all i < j.
if (n > 1) {
ap++;
rp[n - 1] = bn_mul_words(rp, ap, n - 1, ap[-1]);
rp += 2;
}
if (n > 2) {
for (size_t i = n - 2; i > 0; i--) {
ap++;
rp[i] = bn_mul_add_words(rp, ap, i, ap[-1]);
rp += 2;
}
}
// The final result fits in |max| words, so none of the following operations
// will overflow.
// Double |r|, giving the contribution of a[i] * a[j] for all i != j.
bn_add_words(r, r, r, max);
// Add in the contribution of a[i] * a[i] for all i.
bn_sqr_words(tmp, a, n);
bn_add_words(r, r, tmp, max);
}
// r is 2*n words in size,
// a and b are both n words in size. (There's not actually a 'b' here ...)
// n must be a power of 2.
// We multiply and return the result.
// t must be 2*n words in size
// We calculate
// a[0]*b[0]
// a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
// a[1]*b[1]
static void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2,
BN_ULONG *t) {
int n = n2 / 2;
int zero, c1;
BN_ULONG ln, lo, *p;
if (n2 == 4) {
bn_sqr_comba4(r, a);
return;
} else if (n2 == 8) {
bn_sqr_comba8(r, a);
return;
}
if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) {
bn_sqr_normal(r, a, n2, t);
return;
}
// TODO(davidben): This function is not constant-time, but should be. See
// https://crbug.com/boringssl/234.
// r=(a[0]-a[1])*(a[1]-a[0])
c1 = bn_cmp_words(a, &(a[n]), n);
zero = 0;
if (c1 > 0) {
bn_sub_words(t, a, &(a[n]), n);
} else if (c1 < 0) {
bn_sub_words(t, &(a[n]), a, n);
} else {
zero = 1;
}
// The result will always be negative unless it is zero
p = &(t[n2 * 2]);
if (!zero) {
bn_sqr_recursive(&(t[n2]), t, n, p);
} else {
OPENSSL_memset(&(t[n2]), 0, n2 * sizeof(BN_ULONG));
}
bn_sqr_recursive(r, a, n, p);
bn_sqr_recursive(&(r[n2]), &(a[n]), n, p);
// t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
// r[10] holds (a[0]*b[0])
// r[32] holds (b[1]*b[1])
c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
// t[32] is negative
c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
// t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
// r[10] holds (a[0]*a[0])
// r[32] holds (a[1]*a[1])
// c1 holds the carry bits
c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
if (c1) {
p = &(r[n + n2]);
lo = *p;
ln = lo + c1;
*p = ln;
// The overflow will stop before we over write
// words we should not overwrite
if (ln < (BN_ULONG)c1) {
do {
p++;
lo = *p;
ln = lo + 1;
*p = ln;
} while (ln == 0);
}
}
}
int BN_mul_word(BIGNUM *bn, BN_ULONG w) {
if (!bn->width) {
return 1;
}
if (w == 0) {
BN_zero(bn);
return 1;
}
BN_ULONG ll = bn_mul_words(bn->d, bn->d, bn->width, w);
if (ll) {
if (!bn_wexpand(bn, bn->width + 1)) {
return 0;
}
bn->d[bn->width++] = ll;
}
return 1;
}
int bn_sqr_fixed(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx) {
int max, al;
int ret = 0;
BIGNUM *tmp, *rr;
al = a->width;
if (al <= 0) {
r->width = 0;
r->neg = 0;
return 1;
}
BN_CTX_start(ctx);
rr = (a != r) ? r : BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
if (!rr || !tmp) {
goto err;
}
max = 2 * al; // Non-zero (from above)
if (!bn_wexpand(rr, max)) {
goto err;
}
if (al == 4) {
bn_sqr_comba4(rr->d, a->d);
} else if (al == 8) {
bn_sqr_comba8(rr->d, a->d);
} else {
if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) {
BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL * 2];
bn_sqr_normal(rr->d, a->d, al, t);
} else {
int j, k;
j = BN_num_bits_word((BN_ULONG)al);
j = 1 << (j - 1);
k = j + j;
if (al == j) {
if (!bn_wexpand(tmp, k * 2)) {
goto err;
}
bn_sqr_recursive(rr->d, a->d, al, tmp->d);
} else {
if (!bn_wexpand(tmp, max)) {
goto err;
}
bn_sqr_normal(rr->d, a->d, al, tmp->d);
}
}
}
rr->neg = 0;
rr->width = max;
if (rr != r && !BN_copy(r, rr)) {
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
return ret;
}
int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx) {
if (!bn_sqr_fixed(r, a, ctx)) {
return 0;
}
bn_set_minimal_width(r);
return 1;
}
int bn_sqr_small(BN_ULONG *r, size_t num_r, const BN_ULONG *a, size_t num_a) {
if (num_r != 2 * num_a || num_a > BN_SMALL_MAX_WORDS) {
OPENSSL_PUT_ERROR(BN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
if (num_a == 4) {
bn_sqr_comba4(r, a);
} else if (num_a == 8) {
bn_sqr_comba8(r, a);
} else {
BN_ULONG tmp[2 * BN_SMALL_MAX_WORDS];
bn_sqr_normal(r, a, num_a, tmp);
OPENSSL_cleanse(tmp, 2 * num_a * sizeof(BN_ULONG));
}
return 1;
}
Reference in New Issue View Git Blame Copy Permalink