-/* crypto/bn/bn_exp.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.]
- */
-/* ====================================================================
- * Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
- *
- * 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 above 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 acknowledgment:
- * "This product includes software developed by the OpenSSL Project
- * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
- *
- * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
- * endorse or promote products derived from this software without
- * prior written permission. For written permission, please contact
- * openssl-core@openssl.org.
- *
- * 5. Products derived from this software may not be called "OpenSSL"
- * nor may "OpenSSL" appear in their names without prior written
- * permission of the OpenSSL Project.
- *
- * 6. Redistributions of any form whatsoever must retain the following
- * acknowledgment:
- * "This product includes software developed by the OpenSSL Project
- * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
- *
- * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
- * EXPRESSED 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 OpenSSL PROJECT OR
- * ITS 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.
- * ====================================================================
- *
- * This product includes cryptographic software written by Eric Young
- * (eay@cryptsoft.com). This product includes software written by Tim
- * Hudson (tjh@cryptsoft.com).
+/*
+ * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
*
+ * Licensed under the OpenSSL license (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 "internal/cryptlib.h"
+#include "internal/constant_time_locl.h"
#include "bn_lcl.h"
#include <stdlib.h>
# include <alloca.h>
#endif
-#undef RSAZ_ENABLED
-#if defined(OPENSSL_BN_ASM_MONT) && \
- (defined(__x86_64) || defined(__x86_64__) || \
- defined(_M_AMD64) || defined(_M_X64))
-# include "rsaz_exp.h"
-# define RSAZ_ENABLED
-#endif
+#include "rsaz_exp.h"
#undef SPARC_T4_MONT
#if defined(OPENSSL_BN_ASM_MONT) && (defined(__sparc__) || defined(__sparc))
int i, bits, ret = 0;
BIGNUM *v, *rr;
- if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) {
/* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
BNerr(BN_F_BN_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
- return -1;
+ return 0;
}
BN_CTX_start(ctx);
- if ((r == a) || (r == p))
- rr = BN_CTX_get(ctx);
- else
- rr = r;
+ rr = ((r == a) || (r == p)) ? BN_CTX_get(ctx) : r;
v = BN_CTX_get(ctx);
if (rr == NULL || v == NULL)
goto err;
goto err;
}
}
- if (r != rr)
- BN_copy(r, rr);
+ if (r != rr && BN_copy(r, rr) == NULL)
+ goto err;
+
ret = 1;
err:
BN_CTX_end(ctx);
bn_check_top(r);
- return (ret);
+ return ret;
}
int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
bn_check_top(m);
/*-
- * For even modulus m = 2^k*m_odd, it might make sense to compute
+ * For even modulus m = 2^k*m_odd, it might make sense to compute
* a^p mod m_odd and a^p mod 2^k separately (with Montgomery
* exponentiation for the odd part), using appropriate exponent
* reductions, and combine the results using the CRT.
#define RECP_MUL_MOD
#ifdef MONT_MUL_MOD
- /*
- * I have finally been able to take out this pre-condition of the top bit
- * being set. It was caused by an error in BN_div with negatives. There
- * was also another problem when for a^b%m a >= m. eay 07-May-97
- */
- /* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */
-
if (BN_is_odd(m)) {
# ifdef MONT_EXP_WORD
if (a->top == 1 && !a->neg
- && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)) {
+ && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)
+ && (BN_get_flags(a, BN_FLG_CONSTTIME) == 0)
+ && (BN_get_flags(m, BN_FLG_CONSTTIME) == 0)) {
BN_ULONG A = a->d[0];
ret = BN_mod_exp_mont_word(r, A, p, m, ctx, NULL);
} else
#endif
bn_check_top(r);
- return (ret);
+ return ret;
}
int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
BIGNUM *val[TABLE_SIZE];
BN_RECP_CTX recp;
- if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
/* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
BNerr(BN_F_BN_MOD_EXP_RECP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
- return -1;
+ return 0;
}
bits = BN_num_bits(p);
-
if (bits == 0) {
- ret = BN_one(r);
+ /* x**0 mod 1, or x**0 mod -1 is still zero. */
+ if (BN_abs_is_word(m, 1)) {
+ ret = 1;
+ BN_zero(r);
+ } else {
+ ret = BN_one(r);
+ }
return ret;
}
BN_CTX_start(ctx);
aa = BN_CTX_get(ctx);
val[0] = BN_CTX_get(ctx);
- if (!aa || !val[0])
+ if (val[0] == NULL)
goto err;
BN_RECP_CTX_init(&recp);
BN_CTX_end(ctx);
BN_RECP_CTX_free(&recp);
bn_check_top(r);
- return (ret);
+ return ret;
}
int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
BIGNUM *val[TABLE_SIZE];
BN_MONT_CTX *mont = NULL;
- if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont);
}
if (!BN_is_odd(m)) {
BNerr(BN_F_BN_MOD_EXP_MONT, BN_R_CALLED_WITH_EVEN_MODULUS);
- return (0);
+ return 0;
}
bits = BN_num_bits(p);
if (bits == 0) {
- ret = BN_one(rr);
+ /* x**0 mod 1, or x**0 mod -1 is still zero. */
+ if (BN_abs_is_word(m, 1)) {
+ ret = 1;
+ BN_zero(rr);
+ } else {
+ ret = BN_one(rr);
+ }
return ret;
}
d = BN_CTX_get(ctx);
r = BN_CTX_get(ctx);
val[0] = BN_CTX_get(ctx);
- if (!d || !r || !val[0])
+ if (val[0] == NULL)
goto err;
/*
aa = val[0];
} else
aa = a;
- if (BN_is_zero(aa)) {
- BN_zero(rr);
- ret = 1;
- goto err;
- }
- if (!BN_to_montgomery(val[0], aa, mont, ctx))
+ if (!bn_to_mont_fixed_top(val[0], aa, mont, ctx))
goto err; /* 1 */
window = BN_window_bits_for_exponent_size(bits);
if (window > 1) {
- if (!BN_mod_mul_montgomery(d, val[0], val[0], mont, ctx))
+ if (!bn_mul_mont_fixed_top(d, val[0], val[0], mont, ctx))
goto err; /* 2 */
j = 1 << (window - 1);
for (i = 1; i < j; i++) {
if (((val[i] = BN_CTX_get(ctx)) == NULL) ||
- !BN_mod_mul_montgomery(val[i], val[i - 1], d, mont, ctx))
+ !bn_mul_mont_fixed_top(val[i], val[i - 1], d, mont, ctx))
goto err;
}
}
for (i = 1; i < j; i++)
r->d[i] = (~m->d[i]) & BN_MASK2;
r->top = j;
- /*
- * Upper words will be zero if the corresponding words of 'm' were
- * 0xfff[...], so decrement r->top accordingly.
- */
- bn_correct_top(r);
+ r->flags |= BN_FLG_FIXED_TOP;
} else
#endif
- if (!BN_to_montgomery(r, BN_value_one(), mont, ctx))
+ if (!bn_to_mont_fixed_top(r, BN_value_one(), mont, ctx))
goto err;
for (;;) {
if (BN_is_bit_set(p, wstart) == 0) {
if (!start) {
- if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
+ if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx))
goto err;
}
if (wstart == 0)
/* add the 'bytes above' */
if (!start)
for (i = 0; i < j; i++) {
- if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
+ if (!bn_mul_mont_fixed_top(r, r, r, mont, ctx))
goto err;
}
/* wvalue will be an odd number < 2^window */
- if (!BN_mod_mul_montgomery(r, r, val[wvalue >> 1], mont, ctx))
+ if (!bn_mul_mont_fixed_top(r, r, val[wvalue >> 1], mont, ctx))
goto err;
/* move the 'window' down further */
if (wstart < 0)
break;
}
+ /*
+ * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery
+ * removes padding [if any] and makes return value suitable for public
+ * API consumer.
+ */
#if defined(SPARC_T4_MONT)
if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) {
j = mont->N.top; /* borrow j */
BN_MONT_CTX_free(mont);
BN_CTX_end(ctx);
bn_check_top(rr);
- return (ret);
+ return ret;
}
-#if defined(SPARC_T4_MONT)
static BN_ULONG bn_get_bits(const BIGNUM *a, int bitpos)
{
BN_ULONG ret = 0;
return ret & BN_MASK2;
}
-#endif
/*
* BN_mod_exp_mont_consttime() stores the precomputed powers in a specific
static int MOD_EXP_CTIME_COPY_TO_PREBUF(const BIGNUM *b, int top,
unsigned char *buf, int idx,
- int width)
+ int window)
{
- size_t i, j;
+ int i, j;
+ int width = 1 << window;
+ BN_ULONG *table = (BN_ULONG *)buf;
if (top > b->top)
top = b->top; /* this works because 'buf' is explicitly
* zeroed */
- for (i = 0, j = idx; i < top * sizeof b->d[0]; i++, j += width) {
- buf[j] = ((unsigned char *)b->d)[i];
+ for (i = 0, j = idx; i < top; i++, j += width) {
+ table[j] = b->d[i];
}
return 1;
static int MOD_EXP_CTIME_COPY_FROM_PREBUF(BIGNUM *b, int top,
unsigned char *buf, int idx,
- int width)
+ int window)
{
- size_t i, j;
+ int i, j;
+ int width = 1 << window;
+ /*
+ * We declare table 'volatile' in order to discourage compiler
+ * from reordering loads from the table. Concern is that if
+ * reordered in specific manner loads might give away the
+ * information we are trying to conceal. Some would argue that
+ * compiler can reorder them anyway, but it can as well be
+ * argued that doing so would be violation of standard...
+ */
+ volatile BN_ULONG *table = (volatile BN_ULONG *)buf;
if (bn_wexpand(b, top) == NULL)
return 0;
- for (i = 0, j = idx; i < top * sizeof b->d[0]; i++, j += width) {
- ((unsigned char *)b->d)[i] = buf[j];
+ if (window <= 3) {
+ for (i = 0; i < top; i++, table += width) {
+ BN_ULONG acc = 0;
+
+ for (j = 0; j < width; j++) {
+ acc |= table[j] &
+ ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1));
+ }
+
+ b->d[i] = acc;
+ }
+ } else {
+ int xstride = 1 << (window - 2);
+ BN_ULONG y0, y1, y2, y3;
+
+ i = idx >> (window - 2); /* equivalent of idx / xstride */
+ idx &= xstride - 1; /* equivalent of idx % xstride */
+
+ y0 = (BN_ULONG)0 - (constant_time_eq_int(i,0)&1);
+ y1 = (BN_ULONG)0 - (constant_time_eq_int(i,1)&1);
+ y2 = (BN_ULONG)0 - (constant_time_eq_int(i,2)&1);
+ y3 = (BN_ULONG)0 - (constant_time_eq_int(i,3)&1);
+
+ for (i = 0; i < top; i++, table += width) {
+ BN_ULONG acc = 0;
+
+ for (j = 0; j < xstride; j++) {
+ acc |= ( (table[j + 0 * xstride] & y0) |
+ (table[j + 1 * xstride] & y1) |
+ (table[j + 2 * xstride] & y2) |
+ (table[j + 3 * xstride] & y3) )
+ & ((BN_ULONG)0 - (constant_time_eq_int(j,idx)&1));
+ }
+
+ b->d[i] = acc;
+ }
}
b->top = top;
- bn_correct_top(b);
+ b->flags |= BN_FLG_FIXED_TOP;
return 1;
}
* precomputation memory layout to limit data-dependency to a minimum to
* protect secret exponents (cf. the hyper-threading timing attacks pointed
* out by Colin Percival,
- * http://www.daemong-consideredperthreading-considered-harmful/)
+ * http://www.daemonology.net/hyperthreading-considered-harmful/)
*/
int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx,
BN_MONT_CTX *in_mont)
{
- int i, bits, ret = 0, window, wvalue;
+ int i, bits, ret = 0, window, wvalue, wmask, window0;
int top;
BN_MONT_CTX *mont = NULL;
bn_check_top(p);
bn_check_top(m);
- top = m->top;
-
- if (!(m->d[0] & 1)) {
+ if (!BN_is_odd(m)) {
BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME, BN_R_CALLED_WITH_EVEN_MODULUS);
- return (0);
+ return 0;
}
- bits = BN_num_bits(p);
+
+ top = m->top;
+
+ /*
+ * Use all bits stored in |p|, rather than |BN_num_bits|, so we do not leak
+ * whether the top bits are zero.
+ */
+ bits = p->top * BN_BITS2;
if (bits == 0) {
- ret = BN_one(rr);
+ /* x**0 mod 1, or x**0 mod -1 is still zero. */
+ if (BN_abs_is_word(m, 1)) {
+ ret = 1;
+ BN_zero(rr);
+ } else {
+ ret = BN_one(rr);
+ }
return ret;
}
goto err;
}
+ if (a->neg || BN_ucmp(a, m) >= 0) {
+ BIGNUM *reduced = BN_CTX_get(ctx);
+ if (reduced == NULL
+ || !BN_nnmod(reduced, a, m, ctx)) {
+ goto err;
+ }
+ a = reduced;
+ }
+
#ifdef RSAZ_ENABLED
/*
* If the size of the operands allow it, perform the optimized
if (window >= 5) {
window = 5; /* ~5% improvement for RSA2048 sign, and even
* for RSA4096 */
- if ((top & 7) == 0)
- powerbufLen += 2 * top * sizeof(m->d[0]);
+ /* reserve space for mont->N.d[] copy */
+ powerbufLen += top * sizeof(mont->N.d[0]);
}
#endif
(void)0;
tmp.top = top;
} else
#endif
- if (!BN_to_montgomery(&tmp, BN_value_one(), mont, ctx))
+ if (!bn_to_mont_fixed_top(&tmp, BN_value_one(), mont, ctx))
goto err;
/* prepare a^1 in Montgomery domain */
- if (a->neg || BN_ucmp(a, m) >= 0) {
- if (!BN_mod(&am, a, m, ctx))
- goto err;
- if (!BN_to_montgomery(&am, &am, mont, ctx))
- goto err;
- } else if (!BN_to_montgomery(&am, a, mont, ctx))
+ if (!bn_to_mont_fixed_top(&am, a, mont, ctx))
goto err;
#if defined(SPARC_T4_MONT)
top /= 2;
bn_flip_t4(np, mont->N.d, top);
- bits--;
- for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--)
- wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+ /*
+ * The exponent may not have a whole number of fixed-size windows.
+ * To simplify the main loop, the initial window has between 1 and
+ * full-window-size bits such that what remains is always a whole
+ * number of windows
+ */
+ window0 = (bits - 1) % 5 + 1;
+ wmask = (1 << window0) - 1;
+ bits -= window0;
+ wvalue = bn_get_bits(p, bits) & wmask;
bn_gather5_t4(tmp.d, top, powerbuf, wvalue);
/*
* Scan the exponent one window at a time starting from the most
* significant bits.
*/
- while (bits >= 0) {
+ while (bits > 0) {
if (bits < stride)
- stride = bits + 1;
+ stride = bits;
bits -= stride;
- wvalue = bn_get_bits(p, bits + 1);
+ wvalue = bn_get_bits(p, bits);
if ((*pwr5_worker) (tmp.d, np, n0, powerbuf, wvalue, stride))
continue;
const BN_ULONG *not_used, const BN_ULONG *np,
const BN_ULONG *n0, int num);
- BN_ULONG *np = mont->N.d, *n0 = mont->n0, *np2;
+ BN_ULONG *n0 = mont->n0, *np;
/*
* BN_to_montgomery can contaminate words above .top [in
for (i = tmp.top; i < top; i++)
tmp.d[i] = 0;
- if (top & 7)
- np2 = np;
- else
- for (np2 = am.d + top, i = 0; i < top; i++)
- np2[2 * i] = np[i];
+ /*
+ * copy mont->N.d[] to improve cache locality
+ */
+ for (np = am.d + top, i = 0; i < top; i++)
+ np[i] = mont->N.d[i];
bn_scatter5(tmp.d, top, powerbuf, 0);
bn_scatter5(am.d, am.top, powerbuf, 1);
# if 0
for (i = 3; i < 32; i++) {
/* Calculate a^i = a^(i-1) * a */
- bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np2, n0, top, i - 1);
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
bn_scatter5(tmp.d, top, powerbuf, i);
}
# else
}
for (i = 3; i < 8; i += 2) {
int j;
- bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np2, n0, top, i - 1);
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
bn_scatter5(tmp.d, top, powerbuf, i);
for (j = 2 * i; j < 32; j *= 2) {
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
}
}
for (; i < 16; i += 2) {
- bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np2, n0, top, i - 1);
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
bn_scatter5(tmp.d, top, powerbuf, i);
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
bn_scatter5(tmp.d, top, powerbuf, 2 * i);
}
for (; i < 32; i += 2) {
- bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np2, n0, top, i - 1);
+ bn_mul_mont_gather5(tmp.d, am.d, powerbuf, np, n0, top, i - 1);
bn_scatter5(tmp.d, top, powerbuf, i);
}
# endif
- bits--;
- for (wvalue = 0, i = bits % 5; i >= 0; i--, bits--)
- wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
+ /*
+ * The exponent may not have a whole number of fixed-size windows.
+ * To simplify the main loop, the initial window has between 1 and
+ * full-window-size bits such that what remains is always a whole
+ * number of windows
+ */
+ window0 = (bits - 1) % 5 + 1;
+ wmask = (1 << window0) - 1;
+ bits -= window0;
+ wvalue = bn_get_bits(p, bits) & wmask;
bn_gather5(tmp.d, top, powerbuf, wvalue);
/*
* Scan the exponent one window at a time starting from the most
* significant bits.
*/
- if (top & 7)
- while (bits >= 0) {
- for (wvalue = 0, i = 0; i < 5; i++, bits--)
- wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
-
+ if (top & 7) {
+ while (bits > 0) {
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
bn_mul_mont(tmp.d, tmp.d, tmp.d, np, n0, top);
bn_mul_mont_gather5(tmp.d, tmp.d, powerbuf, np, n0, top,
- wvalue);
+ bn_get_bits5(p->d, bits -= 5));
+ }
} else {
- while (bits >= 0) {
- wvalue = bn_get_bits5(p->d, bits - 4);
- bits -= 5;
- bn_power5(tmp.d, tmp.d, powerbuf, np2, n0, top, wvalue);
+ while (bits > 0) {
+ bn_power5(tmp.d, tmp.d, powerbuf, np, n0, top,
+ bn_get_bits5(p->d, bits -= 5));
}
}
- ret = bn_from_montgomery(tmp.d, tmp.d, NULL, np2, n0, top);
+ ret = bn_from_montgomery(tmp.d, tmp.d, NULL, np, n0, top);
tmp.top = top;
bn_correct_top(&tmp);
if (ret) {
} else
#endif
{
- if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, numPowers))
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 0, window))
goto err;
- if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, numPowers))
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&am, top, powerbuf, 1, window))
goto err;
/*
* performance advantage of sqr over mul).
*/
if (window > 1) {
- if (!BN_mod_mul_montgomery(&tmp, &am, &am, mont, ctx))
+ if (!bn_mul_mont_fixed_top(&tmp, &am, &am, mont, ctx))
goto err;
- if (!MOD_EXP_CTIME_COPY_TO_PREBUF
- (&tmp, top, powerbuf, 2, numPowers))
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, 2,
+ window))
goto err;
for (i = 3; i < numPowers; i++) {
/* Calculate a^i = a^(i-1) * a */
- if (!BN_mod_mul_montgomery(&tmp, &am, &tmp, mont, ctx))
+ if (!bn_mul_mont_fixed_top(&tmp, &am, &tmp, mont, ctx))
goto err;
- if (!MOD_EXP_CTIME_COPY_TO_PREBUF
- (&tmp, top, powerbuf, i, numPowers))
+ if (!MOD_EXP_CTIME_COPY_TO_PREBUF(&tmp, top, powerbuf, i,
+ window))
goto err;
}
}
- bits--;
- for (wvalue = 0, i = bits % window; i >= 0; i--, bits--)
- wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
- if (!MOD_EXP_CTIME_COPY_FROM_PREBUF
- (&tmp, top, powerbuf, wvalue, numPowers))
+ /*
+ * The exponent may not have a whole number of fixed-size windows.
+ * To simplify the main loop, the initial window has between 1 and
+ * full-window-size bits such that what remains is always a whole
+ * number of windows
+ */
+ window0 = (bits - 1) % window + 1;
+ wmask = (1 << window0) - 1;
+ bits -= window0;
+ wvalue = bn_get_bits(p, bits) & wmask;
+ if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&tmp, top, powerbuf, wvalue,
+ window))
goto err;
+ wmask = (1 << window) - 1;
/*
* Scan the exponent one window at a time starting from the most
* significant bits.
*/
- while (bits >= 0) {
- wvalue = 0; /* The 'value' of the window */
+ while (bits > 0) {
- /* Scan the window, squaring the result as we go */
- for (i = 0; i < window; i++, bits--) {
- if (!BN_mod_mul_montgomery(&tmp, &tmp, &tmp, mont, ctx))
+ /* Square the result window-size times */
+ for (i = 0; i < window; i++)
+ if (!bn_mul_mont_fixed_top(&tmp, &tmp, &tmp, mont, ctx))
goto err;
- wvalue = (wvalue << 1) + BN_is_bit_set(p, bits);
- }
+ /*
+ * Get a window's worth of bits from the exponent
+ * This avoids calling BN_is_bit_set for each bit, which
+ * is not only slower but also makes each bit vulnerable to
+ * EM (and likely other) side-channel attacks like One&Done
+ * (for details see "One&Done: A Single-Decryption EM-Based
+ * Attack on OpenSSL's Constant-Time Blinded RSA" by M. Alam,
+ * H. Khan, M. Dey, N. Sinha, R. Callan, A. Zajic, and
+ * M. Prvulovic, in USENIX Security'18)
+ */
+ bits -= window;
+ wvalue = bn_get_bits(p, bits) & wmask;
/*
* Fetch the appropriate pre-computed value from the pre-buf
*/
- if (!MOD_EXP_CTIME_COPY_FROM_PREBUF
- (&am, top, powerbuf, wvalue, numPowers))
+ if (!MOD_EXP_CTIME_COPY_FROM_PREBUF(&am, top, powerbuf, wvalue,
+ window))
goto err;
/* Multiply the result into the intermediate result */
- if (!BN_mod_mul_montgomery(&tmp, &tmp, &am, mont, ctx))
+ if (!bn_mul_mont_fixed_top(&tmp, &tmp, &am, mont, ctx))
goto err;
}
}
- /* Convert the final result from montgomery to standard format */
+ /*
+ * Done with zero-padded intermediate BIGNUMs. Final BN_from_montgomery
+ * removes padding [if any] and makes return value suitable for public
+ * API consumer.
+ */
#if defined(SPARC_T4_MONT)
if (OPENSSL_sparcv9cap_P[0] & (SPARCV9_VIS3 | SPARCV9_PREFER_FPU)) {
am.d[0] = 1; /* borrow am */
OPENSSL_free(powerbufFree);
}
BN_CTX_end(ctx);
- return (ret);
+ return ret;
}
int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
int b, bits, ret = 0;
int r_is_one;
BN_ULONG w, next_w;
- BIGNUM *d, *r, *t;
+ BIGNUM *r, *t;
BIGNUM *swap_tmp;
#define BN_MOD_MUL_WORD(r, w, m) \
(BN_mul_word(r, (w)) && \
#define BN_TO_MONTGOMERY_WORD(r, w, mont) \
(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
- if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
/* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
BNerr(BN_F_BN_MOD_EXP_MONT_WORD, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
- return -1;
+ return 0;
}
bn_check_top(p);
if (!BN_is_odd(m)) {
BNerr(BN_F_BN_MOD_EXP_MONT_WORD, BN_R_CALLED_WITH_EVEN_MODULUS);
- return (0);
+ return 0;
}
if (m->top == 1)
a %= m->d[0]; /* make sure that 'a' is reduced */
bits = BN_num_bits(p);
if (bits == 0) {
- /* x**0 mod 1 is still zero. */
- if (BN_is_one(m)) {
+ /* x**0 mod 1, or x**0 mod -1 is still zero. */
+ if (BN_abs_is_word(m, 1)) {
ret = 1;
BN_zero(rr);
- } else
+ } else {
ret = BN_one(rr);
+ }
return ret;
}
if (a == 0) {
}
BN_CTX_start(ctx);
- d = BN_CTX_get(ctx);
r = BN_CTX_get(ctx);
t = BN_CTX_get(ctx);
- if (d == NULL || r == NULL || t == NULL)
+ if (t == NULL)
goto err;
if (in_mont != NULL)
BN_MONT_CTX_free(mont);
BN_CTX_end(ctx);
bn_check_top(rr);
- return (ret);
+ return ret;
}
/* The old fallback, simple version :-) */
/* Table of variables obtained from 'ctx' */
BIGNUM *val[TABLE_SIZE];
- if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+ if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+ || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
/* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
BNerr(BN_F_BN_MOD_EXP_SIMPLE, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
- return -1;
+ return 0;
}
bits = BN_num_bits(p);
-
if (bits == 0) {
- ret = BN_one(r);
+ /* x**0 mod 1, or x**0 mod -1 is still zero. */
+ if (BN_abs_is_word(m, 1)) {
+ ret = 1;
+ BN_zero(r);
+ } else {
+ ret = BN_one(r);
+ }
return ret;
}
BN_CTX_start(ctx);
d = BN_CTX_get(ctx);
val[0] = BN_CTX_get(ctx);
- if (!d || !val[0])
+ if (val[0] == NULL)
goto err;
if (!BN_nnmod(val[0], a, m, ctx))
err:
BN_CTX_end(ctx);
bn_check_top(r);
- return (ret);
+ return ret;
}
projects / openssl.git / blobdiff