40e48e5458
Co-authored-by: Nicola Tuveri <nic.tuv@gmail.com> Co-authored-by: Cesar Pereida Garcia <cesar.pereidagarcia@tut.fi> Co-authored-by: Sohaib ul Hassan <soh.19.hassan@gmail.com> Reviewed-by: Andy Polyakov <appro@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/6009)
862 lines
26 KiB
C
862 lines
26 KiB
C
/*
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* Copyright 2001-2017 The OpenSSL Project Authors. All Rights Reserved.
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* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <string.h>
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#include <openssl/err.h>
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#include "internal/cryptlib.h"
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#include "internal/bn_int.h"
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#include "ec_lcl.h"
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#include "internal/refcount.h"
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/*
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* This file implements the wNAF-based interleaving multi-exponentiation method
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* Formerly at:
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* http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#multiexp
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* You might now find it here:
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* http://link.springer.com/chapter/10.1007%2F3-540-45537-X_13
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* http://www.bmoeller.de/pdf/TI-01-08.multiexp.pdf
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* For multiplication with precomputation, we use wNAF splitting, formerly at:
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* http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#fastexp
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*/
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/* structure for precomputed multiples of the generator */
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struct ec_pre_comp_st {
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const EC_GROUP *group; /* parent EC_GROUP object */
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size_t blocksize; /* block size for wNAF splitting */
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size_t numblocks; /* max. number of blocks for which we have
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* precomputation */
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size_t w; /* window size */
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EC_POINT **points; /* array with pre-calculated multiples of
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* generator: 'num' pointers to EC_POINT
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* objects followed by a NULL */
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size_t num; /* numblocks * 2^(w-1) */
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CRYPTO_REF_COUNT references;
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CRYPTO_RWLOCK *lock;
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};
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static EC_PRE_COMP *ec_pre_comp_new(const EC_GROUP *group)
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{
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EC_PRE_COMP *ret = NULL;
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if (!group)
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return NULL;
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ret = OPENSSL_zalloc(sizeof(*ret));
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if (ret == NULL) {
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ECerr(EC_F_EC_PRE_COMP_NEW, ERR_R_MALLOC_FAILURE);
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return ret;
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}
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ret->group = group;
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ret->blocksize = 8; /* default */
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ret->w = 4; /* default */
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ret->references = 1;
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ret->lock = CRYPTO_THREAD_lock_new();
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if (ret->lock == NULL) {
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ECerr(EC_F_EC_PRE_COMP_NEW, ERR_R_MALLOC_FAILURE);
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OPENSSL_free(ret);
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return NULL;
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}
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return ret;
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}
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EC_PRE_COMP *EC_ec_pre_comp_dup(EC_PRE_COMP *pre)
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{
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int i;
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if (pre != NULL)
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CRYPTO_UP_REF(&pre->references, &i, pre->lock);
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return pre;
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}
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void EC_ec_pre_comp_free(EC_PRE_COMP *pre)
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{
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int i;
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if (pre == NULL)
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return;
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CRYPTO_DOWN_REF(&pre->references, &i, pre->lock);
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REF_PRINT_COUNT("EC_ec", pre);
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if (i > 0)
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return;
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REF_ASSERT_ISNT(i < 0);
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if (pre->points != NULL) {
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EC_POINT **pts;
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for (pts = pre->points; *pts != NULL; pts++)
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EC_POINT_free(*pts);
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OPENSSL_free(pre->points);
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}
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CRYPTO_THREAD_lock_free(pre->lock);
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OPENSSL_free(pre);
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}
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#define EC_POINT_set_flags(P, flags) do { \
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BN_set_flags((P)->X, (flags)); \
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BN_set_flags((P)->Y, (flags)); \
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BN_set_flags((P)->Z, (flags)); \
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} while(0)
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/*
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* This functions computes (in constant time) a point multiplication over the
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* EC group.
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*
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* It performs either a fixed scalar point multiplication
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* (scalar * generator)
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* when point is NULL, or a generic scalar point multiplication
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* (scalar * point)
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* when point is not NULL.
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*
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* scalar should be in the range [0,n) otherwise all constant time bets are off.
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*
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* NB: This says nothing about EC_POINT_add and EC_POINT_dbl,
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* which of course are not constant time themselves.
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*
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* The product is stored in r.
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*
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* Returns 1 on success, 0 otherwise.
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*/
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static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
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const EC_POINT *point, BN_CTX *ctx)
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{
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int i, order_bits, group_top, kbit, pbit, Z_is_one, ret;
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ret = 0;
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EC_POINT *s = NULL;
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BIGNUM *k = NULL;
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BIGNUM *lambda = NULL;
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BN_CTX *new_ctx = NULL;
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if (ctx == NULL)
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if ((ctx = new_ctx = BN_CTX_secure_new()) == NULL)
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return 0;
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if ((group->order == NULL) || (group->field == NULL))
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goto err;
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order_bits = BN_num_bits(group->order);
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s = EC_POINT_new(group);
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if (s == NULL)
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goto err;
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if (point == NULL) {
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if (group->generator == NULL)
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goto err;
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if (!EC_POINT_copy(s, group->generator))
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goto err;
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} else {
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if (!EC_POINT_copy(s, point))
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goto err;
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}
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EC_POINT_set_flags(s, BN_FLG_CONSTTIME);
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BN_CTX_start(ctx);
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lambda = BN_CTX_get(ctx);
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k = BN_CTX_get(ctx);
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if (k == NULL)
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goto err;
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/*
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* Group orders are often on a word boundary.
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* So when we pad the scalar, some timing diff might
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* pop if it needs to be expanded due to carries.
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* So expand ahead of time.
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*/
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group_top = bn_get_top(group->order);
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if ((bn_wexpand(k, group_top + 1) == NULL)
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|| (bn_wexpand(lambda, group_top + 1) == NULL))
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goto err;
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if (!BN_copy(k, scalar))
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goto err;
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BN_set_flags(k, BN_FLG_CONSTTIME);
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if ((BN_num_bits(k) > order_bits) || (BN_is_negative(k))) {
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/*
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* this is an unusual input, and we don't guarantee
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* constant-timeness
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*/
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if(!BN_nnmod(k, k, group->order, ctx))
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goto err;
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}
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if (!BN_add(lambda, k, group->order))
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goto err;
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BN_set_flags(lambda, BN_FLG_CONSTTIME);
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if (!BN_add(k, lambda, group->order))
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goto err;
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/*
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* lambda := scalar + order
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* k := scalar + 2*order
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*/
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kbit = BN_is_bit_set(lambda, order_bits);
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BN_consttime_swap(kbit, k, lambda, group_top + 1);
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group_top = bn_get_top(group->field);
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if ((bn_wexpand(s->X, group_top) == NULL)
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|| (bn_wexpand(s->Y, group_top) == NULL)
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|| (bn_wexpand(s->Z, group_top) == NULL)
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|| (bn_wexpand(r->X, group_top) == NULL)
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|| (bn_wexpand(r->Y, group_top) == NULL)
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|| (bn_wexpand(r->Z, group_top) == NULL))
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goto err;
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/* top bit is a 1, in a fixed pos */
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if (!EC_POINT_copy(r, s))
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goto err;
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EC_POINT_set_flags(r, BN_FLG_CONSTTIME);
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if (!EC_POINT_dbl(group, s, s, ctx))
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goto err;
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pbit = 0;
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#define EC_POINT_CSWAP(c, a, b, w, t) do { \
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BN_consttime_swap(c, (a)->X, (b)->X, w); \
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BN_consttime_swap(c, (a)->Y, (b)->Y, w); \
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BN_consttime_swap(c, (a)->Z, (b)->Z, w); \
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t = ((a)->Z_is_one ^ (b)->Z_is_one) & (c); \
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(a)->Z_is_one ^= (t); \
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(b)->Z_is_one ^= (t); \
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} while(0)
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for (i = order_bits - 1; i >= 0; i--) {
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kbit = BN_is_bit_set(k, i) ^ pbit;
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EC_POINT_CSWAP(kbit, r, s, group_top, Z_is_one);
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if (!EC_POINT_add(group, s, r, s, ctx))
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goto err;
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if (!EC_POINT_dbl(group, r, r, ctx))
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goto err;
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/*
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* pbit logic merges this cswap with that of the
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* next iteration
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*/
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pbit ^= kbit;
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}
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/* one final cswap to move the right value into r */
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EC_POINT_CSWAP(pbit, r, s, group_top, Z_is_one);
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#undef EC_POINT_CSWAP
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ret = 1;
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err:
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EC_POINT_free(s);
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BN_CTX_end(ctx);
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BN_CTX_free(new_ctx);
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return ret;
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}
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#undef EC_POINT_set_flags
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/*
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* TODO: table should be optimised for the wNAF-based implementation,
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* sometimes smaller windows will give better performance (thus the
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* boundaries should be increased)
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*/
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#define EC_window_bits_for_scalar_size(b) \
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((size_t) \
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((b) >= 2000 ? 6 : \
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(b) >= 800 ? 5 : \
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(b) >= 300 ? 4 : \
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(b) >= 70 ? 3 : \
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(b) >= 20 ? 2 : \
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1))
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/*-
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* Compute
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* \sum scalars[i]*points[i],
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* also including
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* scalar*generator
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* in the addition if scalar != NULL
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*/
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int ec_wNAF_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
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size_t num, const EC_POINT *points[], const BIGNUM *scalars[],
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BN_CTX *ctx)
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{
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if ((scalar != NULL) && (num == 0)) {
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/* In this case we want to compute scalar * GeneratorPoint:
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* this codepath is reached most prominently by (ephemeral) key
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* generation of EC cryptosystems (i.e. ECDSA keygen and sign setup,
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* ECDH keygen/first half), where the scalar is always secret.
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* This is why we ignore if BN_FLG_CONSTTIME is actually set and we
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* always call the constant time version.
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*/
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return ec_mul_consttime(group, r, scalar, NULL, ctx);
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}
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if ((scalar == NULL) && (num == 1)) {
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/* In this case we want to compute scalar * GenericPoint:
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* this codepath is reached most prominently by the second half of
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* ECDH, where the secret scalar is multiplied by the peer's public
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* point.
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* To protect the secret scalar, we ignore if BN_FLG_CONSTTIME is
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* actually set and we always call the constant time version.
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*/
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return ec_mul_consttime(group, r, scalars[0], points[0], ctx);
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}
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BN_CTX *new_ctx = NULL;
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const EC_POINT *generator = NULL;
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EC_POINT *tmp = NULL;
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size_t totalnum;
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size_t blocksize = 0, numblocks = 0; /* for wNAF splitting */
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size_t pre_points_per_block = 0;
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size_t i, j;
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int k;
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int r_is_inverted = 0;
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int r_is_at_infinity = 1;
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size_t *wsize = NULL; /* individual window sizes */
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signed char **wNAF = NULL; /* individual wNAFs */
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size_t *wNAF_len = NULL;
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size_t max_len = 0;
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size_t num_val;
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EC_POINT **val = NULL; /* precomputation */
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EC_POINT **v;
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EC_POINT ***val_sub = NULL; /* pointers to sub-arrays of 'val' or
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* 'pre_comp->points' */
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const EC_PRE_COMP *pre_comp = NULL;
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int num_scalar = 0; /* flag: will be set to 1 if 'scalar' must be
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* treated like other scalars, i.e.
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* precomputation is not available */
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int ret = 0;
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if (group->meth != r->meth) {
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ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS);
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return 0;
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}
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if ((scalar == NULL) && (num == 0)) {
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return EC_POINT_set_to_infinity(group, r);
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}
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for (i = 0; i < num; i++) {
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if (group->meth != points[i]->meth) {
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ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS);
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return 0;
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}
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}
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if (ctx == NULL) {
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ctx = new_ctx = BN_CTX_new();
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if (ctx == NULL)
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goto err;
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}
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if (scalar != NULL) {
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generator = EC_GROUP_get0_generator(group);
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if (generator == NULL) {
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ECerr(EC_F_EC_WNAF_MUL, EC_R_UNDEFINED_GENERATOR);
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goto err;
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}
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/* look if we can use precomputed multiples of generator */
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pre_comp = group->pre_comp.ec;
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if (pre_comp && pre_comp->numblocks
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&& (EC_POINT_cmp(group, generator, pre_comp->points[0], ctx) ==
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0)) {
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blocksize = pre_comp->blocksize;
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/*
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* determine maximum number of blocks that wNAF splitting may
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* yield (NB: maximum wNAF length is bit length plus one)
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*/
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numblocks = (BN_num_bits(scalar) / blocksize) + 1;
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/*
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* we cannot use more blocks than we have precomputation for
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*/
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if (numblocks > pre_comp->numblocks)
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numblocks = pre_comp->numblocks;
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pre_points_per_block = (size_t)1 << (pre_comp->w - 1);
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/* check that pre_comp looks sane */
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if (pre_comp->num != (pre_comp->numblocks * pre_points_per_block)) {
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ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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} else {
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/* can't use precomputation */
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pre_comp = NULL;
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numblocks = 1;
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num_scalar = 1; /* treat 'scalar' like 'num'-th element of
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* 'scalars' */
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}
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}
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totalnum = num + numblocks;
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wsize = OPENSSL_malloc(totalnum * sizeof(wsize[0]));
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wNAF_len = OPENSSL_malloc(totalnum * sizeof(wNAF_len[0]));
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/* include space for pivot */
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wNAF = OPENSSL_malloc((totalnum + 1) * sizeof(wNAF[0]));
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val_sub = OPENSSL_malloc(totalnum * sizeof(val_sub[0]));
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/* Ensure wNAF is initialised in case we end up going to err */
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if (wNAF != NULL)
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wNAF[0] = NULL; /* preliminary pivot */
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if (wsize == NULL || wNAF_len == NULL || wNAF == NULL || val_sub == NULL) {
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ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
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goto err;
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}
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/*
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* num_val will be the total number of temporarily precomputed points
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*/
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num_val = 0;
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for (i = 0; i < num + num_scalar; i++) {
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size_t bits;
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bits = i < num ? BN_num_bits(scalars[i]) : BN_num_bits(scalar);
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wsize[i] = EC_window_bits_for_scalar_size(bits);
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num_val += (size_t)1 << (wsize[i] - 1);
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wNAF[i + 1] = NULL; /* make sure we always have a pivot */
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wNAF[i] =
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bn_compute_wNAF((i < num ? scalars[i] : scalar), wsize[i],
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&wNAF_len[i]);
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if (wNAF[i] == NULL)
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goto err;
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if (wNAF_len[i] > max_len)
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max_len = wNAF_len[i];
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}
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if (numblocks) {
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/* we go here iff scalar != NULL */
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if (pre_comp == NULL) {
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if (num_scalar != 1) {
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ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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/* we have already generated a wNAF for 'scalar' */
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} else {
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signed char *tmp_wNAF = NULL;
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size_t tmp_len = 0;
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if (num_scalar != 0) {
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ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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/*
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* use the window size for which we have precomputation
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*/
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wsize[num] = pre_comp->w;
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tmp_wNAF = bn_compute_wNAF(scalar, wsize[num], &tmp_len);
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if (!tmp_wNAF)
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goto err;
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if (tmp_len <= max_len) {
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/*
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* One of the other wNAFs is at least as long as the wNAF
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* belonging to the generator, so wNAF splitting will not buy
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* us anything.
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*/
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numblocks = 1;
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totalnum = num + 1; /* don't use wNAF splitting */
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wNAF[num] = tmp_wNAF;
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wNAF[num + 1] = NULL;
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wNAF_len[num] = tmp_len;
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/*
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* pre_comp->points starts with the points that we need here:
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*/
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val_sub[num] = pre_comp->points;
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} else {
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/*
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* don't include tmp_wNAF directly into wNAF array - use wNAF
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* splitting and include the blocks
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*/
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signed char *pp;
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EC_POINT **tmp_points;
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if (tmp_len < numblocks * blocksize) {
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/*
|
|
* possibly we can do with fewer blocks than estimated
|
|
*/
|
|
numblocks = (tmp_len + blocksize - 1) / blocksize;
|
|
if (numblocks > pre_comp->numblocks) {
|
|
ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
|
|
OPENSSL_free(tmp_wNAF);
|
|
goto err;
|
|
}
|
|
totalnum = num + numblocks;
|
|
}
|
|
|
|
/* split wNAF in 'numblocks' parts */
|
|
pp = tmp_wNAF;
|
|
tmp_points = pre_comp->points;
|
|
|
|
for (i = num; i < totalnum; i++) {
|
|
if (i < totalnum - 1) {
|
|
wNAF_len[i] = blocksize;
|
|
if (tmp_len < blocksize) {
|
|
ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
|
|
OPENSSL_free(tmp_wNAF);
|
|
goto err;
|
|
}
|
|
tmp_len -= blocksize;
|
|
} else
|
|
/*
|
|
* last block gets whatever is left (this could be
|
|
* more or less than 'blocksize'!)
|
|
*/
|
|
wNAF_len[i] = tmp_len;
|
|
|
|
wNAF[i + 1] = NULL;
|
|
wNAF[i] = OPENSSL_malloc(wNAF_len[i]);
|
|
if (wNAF[i] == NULL) {
|
|
ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
|
|
OPENSSL_free(tmp_wNAF);
|
|
goto err;
|
|
}
|
|
memcpy(wNAF[i], pp, wNAF_len[i]);
|
|
if (wNAF_len[i] > max_len)
|
|
max_len = wNAF_len[i];
|
|
|
|
if (*tmp_points == NULL) {
|
|
ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
|
|
OPENSSL_free(tmp_wNAF);
|
|
goto err;
|
|
}
|
|
val_sub[i] = tmp_points;
|
|
tmp_points += pre_points_per_block;
|
|
pp += blocksize;
|
|
}
|
|
OPENSSL_free(tmp_wNAF);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* All points we precompute now go into a single array 'val'.
|
|
* 'val_sub[i]' is a pointer to the subarray for the i-th point, or to a
|
|
* subarray of 'pre_comp->points' if we already have precomputation.
|
|
*/
|
|
val = OPENSSL_malloc((num_val + 1) * sizeof(val[0]));
|
|
if (val == NULL) {
|
|
ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
val[num_val] = NULL; /* pivot element */
|
|
|
|
/* allocate points for precomputation */
|
|
v = val;
|
|
for (i = 0; i < num + num_scalar; i++) {
|
|
val_sub[i] = v;
|
|
for (j = 0; j < ((size_t)1 << (wsize[i] - 1)); j++) {
|
|
*v = EC_POINT_new(group);
|
|
if (*v == NULL)
|
|
goto err;
|
|
v++;
|
|
}
|
|
}
|
|
if (!(v == val + num_val)) {
|
|
ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR);
|
|
goto err;
|
|
}
|
|
|
|
if ((tmp = EC_POINT_new(group)) == NULL)
|
|
goto err;
|
|
|
|
/*-
|
|
* prepare precomputed values:
|
|
* val_sub[i][0] := points[i]
|
|
* val_sub[i][1] := 3 * points[i]
|
|
* val_sub[i][2] := 5 * points[i]
|
|
* ...
|
|
*/
|
|
for (i = 0; i < num + num_scalar; i++) {
|
|
if (i < num) {
|
|
if (!EC_POINT_copy(val_sub[i][0], points[i]))
|
|
goto err;
|
|
} else {
|
|
if (!EC_POINT_copy(val_sub[i][0], generator))
|
|
goto err;
|
|
}
|
|
|
|
if (wsize[i] > 1) {
|
|
if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx))
|
|
goto err;
|
|
for (j = 1; j < ((size_t)1 << (wsize[i] - 1)); j++) {
|
|
if (!EC_POINT_add
|
|
(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx))
|
|
goto err;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!EC_POINTs_make_affine(group, num_val, val, ctx))
|
|
goto err;
|
|
|
|
r_is_at_infinity = 1;
|
|
|
|
for (k = max_len - 1; k >= 0; k--) {
|
|
if (!r_is_at_infinity) {
|
|
if (!EC_POINT_dbl(group, r, r, ctx))
|
|
goto err;
|
|
}
|
|
|
|
for (i = 0; i < totalnum; i++) {
|
|
if (wNAF_len[i] > (size_t)k) {
|
|
int digit = wNAF[i][k];
|
|
int is_neg;
|
|
|
|
if (digit) {
|
|
is_neg = digit < 0;
|
|
|
|
if (is_neg)
|
|
digit = -digit;
|
|
|
|
if (is_neg != r_is_inverted) {
|
|
if (!r_is_at_infinity) {
|
|
if (!EC_POINT_invert(group, r, ctx))
|
|
goto err;
|
|
}
|
|
r_is_inverted = !r_is_inverted;
|
|
}
|
|
|
|
/* digit > 0 */
|
|
|
|
if (r_is_at_infinity) {
|
|
if (!EC_POINT_copy(r, val_sub[i][digit >> 1]))
|
|
goto err;
|
|
r_is_at_infinity = 0;
|
|
} else {
|
|
if (!EC_POINT_add
|
|
(group, r, r, val_sub[i][digit >> 1], ctx))
|
|
goto err;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (r_is_at_infinity) {
|
|
if (!EC_POINT_set_to_infinity(group, r))
|
|
goto err;
|
|
} else {
|
|
if (r_is_inverted)
|
|
if (!EC_POINT_invert(group, r, ctx))
|
|
goto err;
|
|
}
|
|
|
|
ret = 1;
|
|
|
|
err:
|
|
BN_CTX_free(new_ctx);
|
|
EC_POINT_free(tmp);
|
|
OPENSSL_free(wsize);
|
|
OPENSSL_free(wNAF_len);
|
|
if (wNAF != NULL) {
|
|
signed char **w;
|
|
|
|
for (w = wNAF; *w != NULL; w++)
|
|
OPENSSL_free(*w);
|
|
|
|
OPENSSL_free(wNAF);
|
|
}
|
|
if (val != NULL) {
|
|
for (v = val; *v != NULL; v++)
|
|
EC_POINT_clear_free(*v);
|
|
|
|
OPENSSL_free(val);
|
|
}
|
|
OPENSSL_free(val_sub);
|
|
return ret;
|
|
}
|
|
|
|
/*-
|
|
* ec_wNAF_precompute_mult()
|
|
* creates an EC_PRE_COMP object with preprecomputed multiples of the generator
|
|
* for use with wNAF splitting as implemented in ec_wNAF_mul().
|
|
*
|
|
* 'pre_comp->points' is an array of multiples of the generator
|
|
* of the following form:
|
|
* points[0] = generator;
|
|
* points[1] = 3 * generator;
|
|
* ...
|
|
* points[2^(w-1)-1] = (2^(w-1)-1) * generator;
|
|
* points[2^(w-1)] = 2^blocksize * generator;
|
|
* points[2^(w-1)+1] = 3 * 2^blocksize * generator;
|
|
* ...
|
|
* points[2^(w-1)*(numblocks-1)-1] = (2^(w-1)) * 2^(blocksize*(numblocks-2)) * generator
|
|
* points[2^(w-1)*(numblocks-1)] = 2^(blocksize*(numblocks-1)) * generator
|
|
* ...
|
|
* points[2^(w-1)*numblocks-1] = (2^(w-1)) * 2^(blocksize*(numblocks-1)) * generator
|
|
* points[2^(w-1)*numblocks] = NULL
|
|
*/
|
|
int ec_wNAF_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
|
|
{
|
|
const EC_POINT *generator;
|
|
EC_POINT *tmp_point = NULL, *base = NULL, **var;
|
|
BN_CTX *new_ctx = NULL;
|
|
const BIGNUM *order;
|
|
size_t i, bits, w, pre_points_per_block, blocksize, numblocks, num;
|
|
EC_POINT **points = NULL;
|
|
EC_PRE_COMP *pre_comp;
|
|
int ret = 0;
|
|
|
|
/* if there is an old EC_PRE_COMP object, throw it away */
|
|
EC_pre_comp_free(group);
|
|
if ((pre_comp = ec_pre_comp_new(group)) == NULL)
|
|
return 0;
|
|
|
|
generator = EC_GROUP_get0_generator(group);
|
|
if (generator == NULL) {
|
|
ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNDEFINED_GENERATOR);
|
|
goto err;
|
|
}
|
|
|
|
if (ctx == NULL) {
|
|
ctx = new_ctx = BN_CTX_new();
|
|
if (ctx == NULL)
|
|
goto err;
|
|
}
|
|
|
|
BN_CTX_start(ctx);
|
|
|
|
order = EC_GROUP_get0_order(group);
|
|
if (order == NULL)
|
|
goto err;
|
|
if (BN_is_zero(order)) {
|
|
ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNKNOWN_ORDER);
|
|
goto err;
|
|
}
|
|
|
|
bits = BN_num_bits(order);
|
|
/*
|
|
* The following parameters mean we precompute (approximately) one point
|
|
* per bit. TBD: The combination 8, 4 is perfect for 160 bits; for other
|
|
* bit lengths, other parameter combinations might provide better
|
|
* efficiency.
|
|
*/
|
|
blocksize = 8;
|
|
w = 4;
|
|
if (EC_window_bits_for_scalar_size(bits) > w) {
|
|
/* let's not make the window too small ... */
|
|
w = EC_window_bits_for_scalar_size(bits);
|
|
}
|
|
|
|
numblocks = (bits + blocksize - 1) / blocksize; /* max. number of blocks
|
|
* to use for wNAF
|
|
* splitting */
|
|
|
|
pre_points_per_block = (size_t)1 << (w - 1);
|
|
num = pre_points_per_block * numblocks; /* number of points to compute
|
|
* and store */
|
|
|
|
points = OPENSSL_malloc(sizeof(*points) * (num + 1));
|
|
if (points == NULL) {
|
|
ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
|
|
var = points;
|
|
var[num] = NULL; /* pivot */
|
|
for (i = 0; i < num; i++) {
|
|
if ((var[i] = EC_POINT_new(group)) == NULL) {
|
|
ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
}
|
|
|
|
if ((tmp_point = EC_POINT_new(group)) == NULL
|
|
|| (base = EC_POINT_new(group)) == NULL) {
|
|
ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
|
|
if (!EC_POINT_copy(base, generator))
|
|
goto err;
|
|
|
|
/* do the precomputation */
|
|
for (i = 0; i < numblocks; i++) {
|
|
size_t j;
|
|
|
|
if (!EC_POINT_dbl(group, tmp_point, base, ctx))
|
|
goto err;
|
|
|
|
if (!EC_POINT_copy(*var++, base))
|
|
goto err;
|
|
|
|
for (j = 1; j < pre_points_per_block; j++, var++) {
|
|
/*
|
|
* calculate odd multiples of the current base point
|
|
*/
|
|
if (!EC_POINT_add(group, *var, tmp_point, *(var - 1), ctx))
|
|
goto err;
|
|
}
|
|
|
|
if (i < numblocks - 1) {
|
|
/*
|
|
* get the next base (multiply current one by 2^blocksize)
|
|
*/
|
|
size_t k;
|
|
|
|
if (blocksize <= 2) {
|
|
ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_INTERNAL_ERROR);
|
|
goto err;
|
|
}
|
|
|
|
if (!EC_POINT_dbl(group, base, tmp_point, ctx))
|
|
goto err;
|
|
for (k = 2; k < blocksize; k++) {
|
|
if (!EC_POINT_dbl(group, base, base, ctx))
|
|
goto err;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!EC_POINTs_make_affine(group, num, points, ctx))
|
|
goto err;
|
|
|
|
pre_comp->group = group;
|
|
pre_comp->blocksize = blocksize;
|
|
pre_comp->numblocks = numblocks;
|
|
pre_comp->w = w;
|
|
pre_comp->points = points;
|
|
points = NULL;
|
|
pre_comp->num = num;
|
|
SETPRECOMP(group, ec, pre_comp);
|
|
pre_comp = NULL;
|
|
ret = 1;
|
|
|
|
err:
|
|
if (ctx != NULL)
|
|
BN_CTX_end(ctx);
|
|
BN_CTX_free(new_ctx);
|
|
EC_ec_pre_comp_free(pre_comp);
|
|
if (points) {
|
|
EC_POINT **p;
|
|
|
|
for (p = points; *p != NULL; p++)
|
|
EC_POINT_free(*p);
|
|
OPENSSL_free(points);
|
|
}
|
|
EC_POINT_free(tmp_point);
|
|
EC_POINT_free(base);
|
|
return ret;
|
|
}
|
|
|
|
int ec_wNAF_have_precompute_mult(const EC_GROUP *group)
|
|
{
|
|
return HAVEPRECOMP(group, ec);
|
|
}
|