/*
- * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
*
- * Licensed under the OpenSSL license (the "License"). You may not use
+ * 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"
+#include "bn_local.h"
int BN_lshift1(BIGNUM *r, const BIGNUM *a)
{
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;
for (i = 0; i < a->top; i++) {
t = *(ap++);
*(rp++) = ((t << 1) | c) & BN_MASK2;
- c = (t & BN_TBIT) ? 1 : 0;
- }
- if (c) {
- *rp = 1;
- r->top++;
+ c = t >> (BN_BITS2 - 1);
}
+ *rp = c;
+ r->top += c;
bn_check_top(r);
- return (1);
+ return 1;
}
int BN_rshift1(BIGNUM *r, const BIGNUM *a)
{
BN_ULONG *ap, *rp, t, c;
- int i, j;
+ int i;
bn_check_top(r);
bn_check_top(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);
+ if (bn_wexpand(r, i) == NULL)
+ return 0;
r->neg = a->neg;
}
rp = r->d;
+ r->top = i;
t = ap[--i];
- c = (t & 1) ? BN_TBIT : 0;
- if (t >>= 1)
- rp[i] = t;
+ rp[i] = t >> 1;
+ c = t << (BN_BITS2 - 1);
+ r->top -= (t == 1);
while (i > 0) {
t = ap[--i];
rp[i] = ((t >> 1) & BN_MASK2) | c;
- c = (t & 1) ? BN_TBIT : 0;
+ c = t << (BN_BITS2 - 1);
}
- 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;
}
- nw = n / BN_BITS2;
- if (bn_wexpand(r, a->top + nw + 1) == NULL)
- return (0);
- r->neg = a->neg;
- 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;
- }
- memset(t, 0, sizeof(*t) * nw);
- r->top = a->top + nw + 1;
+ ret = bn_lshift_fixed_top(r, a, n);
+
bn_correct_top(r);
bn_check_top(r);
- return (1);
+
+ return ret;
}
-int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
+/*
+ * 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, j, nw, lb, rb;
+ int i, nw;
+ unsigned int lb, rb;
BN_ULONG *t, *f;
- BN_ULONG l, tmp;
+ 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;
+
+ 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;
+ }
+ 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;
+ r->flags |= BN_FLG_FIXED_TOP;
+
+ return 1;
+}
+
+int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
+{
+ int ret = 0;
+
if (n < 0) {
BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT);
return 0;
}
+ ret = bn_rshift_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 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;
- rb = n % BN_BITS2;
- lb = BN_BITS2 - rb;
- if (nw >= a->top || a->top == 0) {
+ if (nw >= a->top) {
+ /* shouldn't happen, but formally required */
BN_zero(r);
- return (1);
- }
- i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
- if (r != a) {
- if (bn_wexpand(r, i) == NULL)
- return (0);
- r->neg = a->neg;
- } else {
- if (n == 0)
- return 1; /* or the copying loop will go berserk */
+ return 1;
}
- f = &(a->d[nw]);
- t = r->d;
- j = a->top - nw;
- r->top = i;
+ 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;
- if (rb == 0) {
- for (i = j; i != 0; i--)
- *(t++) = *(f++);
- } else {
- l = *(f++);
- for (i = j - 1; i != 0; i--) {
- tmp = (l >> rb) & BN_MASK2;
- l = *(f++);
- *(t++) = (tmp | (l << lb)) & BN_MASK2;
- }
- if ((l = (l >> rb) & BN_MASK2))
- *(t) = l;
+ 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;
}
- if (!r->top)
- r->neg = 0; /* don't allow negative zero */
- bn_check_top(r);
- return (1);
+ t[i] = l >> rb;
+
+ r->neg = a->neg;
+ r->top = top;
+ r->flags |= BN_FLG_FIXED_TOP;
+
+ return 1;
}
projects / openssl.git / blobdiff