-/* crypto/bn/bn_shift.c */
-/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
- * All rights reserved.
+/*
+ * Copyright 1995-2018 The OpenSSL Project Authors. 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.]
+ * 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 "internal/cryptlib.h"
#include "bn_lcl.h"
if (r != a) {
r->neg = a->neg;
if (bn_wexpand(r, a->top + 1) == NULL)
- return (0);
+ return 0;
r->top = a->top;
} else {
if (bn_wexpand(r, a->top + 1) == NULL)
- return (0);
+ return 0;
}
ap = a->d;
rp = r->d;
r->top++;
}
bn_check_top(r);
- return (1);
+ return 1;
}
int BN_rshift1(BIGNUM *r, const BIGNUM *a)
if (BN_is_zero(a)) {
BN_zero(r);
- return (1);
+ return 1;
}
i = a->top;
ap = a->d;
j = i - (ap[i - 1] == 1);
if (a != r) {
if (bn_wexpand(r, j) == NULL)
- return (0);
+ return 0;
r->neg = a->neg;
}
rp = r->d;
c = (t & 1) ? BN_TBIT : 0;
}
r->top = j;
+ if (!r->top)
+ r->neg = 0; /* don't allow negative zero */
bn_check_top(r);
- return (1);
+ return 1;
}
int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
{
- int i, nw, lb, rb;
- BN_ULONG *t, *f;
- BN_ULONG l;
-
- bn_check_top(r);
- bn_check_top(a);
+ int ret;
if (n < 0) {
BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT);
return 0;
}
- r->neg = a->neg;
+ ret = bn_lshift_fixed_top(r, a, n);
+
+ bn_correct_top(r);
+ bn_check_top(r);
+
+ return ret;
+}
+
+/*
+ * In respect to shift factor the execution time is invariant of
+ * |n % BN_BITS2|, but not |n / BN_BITS2|. Or in other words pre-condition
+ * for constant-time-ness is |n < BN_BITS2| or |n / BN_BITS2| being
+ * non-secret.
+ */
+int bn_lshift_fixed_top(BIGNUM *r, const BIGNUM *a, int n)
+{
+ int i, nw;
+ unsigned int lb, rb;
+ BN_ULONG *t, *f;
+ BN_ULONG l, m, rmask = 0;
+
+ assert(n >= 0);
+
+ bn_check_top(r);
+ bn_check_top(a);
+
nw = n / BN_BITS2;
if (bn_wexpand(r, a->top + nw + 1) == NULL)
- return (0);
- lb = n % BN_BITS2;
- rb = BN_BITS2 - lb;
- f = a->d;
- t = r->d;
- t[a->top + nw] = 0;
- if (lb == 0)
- for (i = a->top - 1; i >= 0; i--)
- t[nw + i] = f[i];
- else
- for (i = a->top - 1; i >= 0; i--) {
- l = f[i];
- t[nw + i + 1] |= (l >> rb) & BN_MASK2;
- t[nw + i] = (l << lb) & BN_MASK2;
+ return 0;
+
+ if (a->top != 0) {
+ lb = (unsigned int)n % BN_BITS2;
+ rb = BN_BITS2 - lb;
+ rb %= BN_BITS2; /* say no to undefined behaviour */
+ rmask = (BN_ULONG)0 - rb; /* rmask = 0 - (rb != 0) */
+ rmask |= rmask >> 8;
+ f = &(a->d[0]);
+ t = &(r->d[nw]);
+ l = f[a->top - 1];
+ t[a->top] = (l >> rb) & rmask;
+ for (i = a->top - 1; i > 0; i--) {
+ m = l << lb;
+ l = f[i - 1];
+ t[i] = (m | ((l >> rb) & rmask)) & BN_MASK2;
}
- memset(t, 0, sizeof(*t) * nw);
+ t[0] = (l << lb) & BN_MASK2;
+ } else {
+ /* shouldn't happen, but formally required */
+ r->d[nw] = 0;
+ }
+ if (nw != 0)
+ memset(r->d, 0, sizeof(*t) * nw);
+
+ r->neg = a->neg;
r->top = a->top + nw + 1;
- bn_correct_top(r);
- bn_check_top(r);
- return (1);
+ r->flags |= BN_FLG_FIXED_TOP;
+
+ return 1;
}
int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
lb = BN_BITS2 - rb;
if (nw >= a->top || a->top == 0) {
BN_zero(r);
- return (1);
+ return 1;
}
i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
if (r != a) {
- r->neg = a->neg;
if (bn_wexpand(r, i) == NULL)
- return (0);
+ return 0;
+ r->neg = a->neg;
} else {
if (n == 0)
return 1; /* or the copying loop will go berserk */
if ((l = (l >> rb) & BN_MASK2))
*(t) = l;
}
+ if (!r->top)
+ r->neg = 0; /* don't allow negative zero */
bn_check_top(r);
- return (1);
+ return 1;
+}
+
+/*
+ * In respect to shift factor the execution time is invariant of
+ * |n % BN_BITS2|, but not |n / BN_BITS2|. Or in other words pre-condition
+ * for constant-time-ness for sufficiently[!] zero-padded inputs is
+ * |n < BN_BITS2| or |n / BN_BITS2| being non-secret.
+ */
+int bn_rshift_fixed_top(BIGNUM *r, const BIGNUM *a, int n)
+{
+ int i, top, nw;
+ unsigned int lb, rb;
+ BN_ULONG *t, *f;
+ BN_ULONG l, m, mask;
+
+ bn_check_top(r);
+ bn_check_top(a);
+
+ assert(n >= 0);
+
+ nw = n / BN_BITS2;
+ if (nw >= a->top) {
+ /* shouldn't happen, but formally required */
+ BN_zero(r);
+ return 1;
+ }
+
+ rb = (unsigned int)n % BN_BITS2;
+ lb = BN_BITS2 - rb;
+ lb %= BN_BITS2; /* say no to undefined behaviour */
+ mask = (BN_ULONG)0 - lb; /* mask = 0 - (lb != 0) */
+ mask |= mask >> 8;
+ top = a->top - nw;
+ if (r != a && bn_wexpand(r, top) == NULL)
+ return 0;
+
+ t = &(r->d[0]);
+ f = &(a->d[nw]);
+ l = f[0];
+ for (i = 0; i < top - 1; i++) {
+ m = f[i + 1];
+ t[i] = (l >> rb) | ((m << lb) & mask);
+ l = m;
+ }
+ t[i] = l >> rb;
+
+ r->neg = a->neg;
+ r->top = top;
+ r->flags |= BN_FLG_FIXED_TOP;
+
+ return 1;
}
projects / openssl.git / blobdiff