58d6fc48cc
Change-Id: Ib2ce220e31a4f808999934197a7f43b8723131e8 Reviewed-on: https://boringssl-review.googlesource.com/27884 Reviewed-by: David Benjamin <davidben@google.com> Commit-Queue: David Benjamin <davidben@google.com> CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
83 lines
2.9 KiB
C
83 lines
2.9 KiB
C
/* Copyright (c) 2018, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#include <openssl/ec.h>
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#include <openssl/err.h>
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#include <assert.h>
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#include "internal.h"
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#include "../bn/internal.h"
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#include "../../internal.h"
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int ec_bignum_to_felem(const EC_GROUP *group, EC_FELEM *out, const BIGNUM *in) {
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if (BN_is_negative(in) || BN_cmp(in, &group->field) >= 0) {
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OPENSSL_PUT_ERROR(EC, EC_R_COORDINATES_OUT_OF_RANGE);
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return 0;
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}
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return group->meth->bignum_to_felem(group, out, in);
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}
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int ec_felem_to_bignum(const EC_GROUP *group, BIGNUM *out, const EC_FELEM *in) {
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return group->meth->felem_to_bignum(group, out, in);
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}
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void ec_felem_neg(const EC_GROUP *group, EC_FELEM *out, const EC_FELEM *a) {
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// -a is zero if a is zero and p-a otherwise.
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BN_ULONG mask = ec_felem_non_zero_mask(group, a);
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BN_ULONG borrow =
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bn_sub_words(out->words, group->field.d, a->words, group->field.width);
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assert(borrow == 0);
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(void)borrow;
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for (int i = 0; i < group->field.width; i++) {
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out->words[i] &= mask;
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}
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}
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void ec_felem_add(const EC_GROUP *group, EC_FELEM *out, const EC_FELEM *a,
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const EC_FELEM *b) {
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EC_FELEM tmp;
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bn_mod_add_words(out->words, a->words, b->words, group->field.d, tmp.words,
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group->field.width);
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}
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void ec_felem_sub(const EC_GROUP *group, EC_FELEM *out, const EC_FELEM *a,
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const EC_FELEM *b) {
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EC_FELEM tmp;
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bn_mod_sub_words(out->words, a->words, b->words, group->field.d, tmp.words,
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group->field.width);
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}
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BN_ULONG ec_felem_non_zero_mask(const EC_GROUP *group, const EC_FELEM *a) {
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BN_ULONG mask = 0;
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for (int i = 0; i < group->field.width; i++) {
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mask |= a->words[i];
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}
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return ~constant_time_is_zero_w(mask);
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}
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void ec_felem_select(const EC_GROUP *group, EC_FELEM *out, BN_ULONG mask,
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const EC_FELEM *a, const EC_FELEM *b) {
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bn_select_words(out->words, mask, a->words, b->words, group->field.width);
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}
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int ec_felem_equal(const EC_GROUP *group, const EC_FELEM *a,
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const EC_FELEM *b) {
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// Note this function is variable-time. Constant-time operations should use
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// |ec_felem_non_zero_mask|.
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return OPENSSL_memcmp(a->words, b->words,
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group->field.width * sizeof(BN_ULONG)) == 0;
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}
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