94 lines
2.9 KiB
C
94 lines
2.9 KiB
C
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// Copyright (c) 2018, Google Inc.
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// SPDX-License-Identifier: ISC
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#include <openssl/ec.h>
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#include <openssl/err.h>
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#include <openssl/mem.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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const EC_FELEM *ec_felem_one(const EC_GROUP *group) {
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// We reuse generator.Z as a cache for 1 in the field.
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return &group->generator.raw.Z;
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}
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int ec_bignum_to_felem(const EC_GROUP *group, EC_FELEM *out, const BIGNUM *in) {
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uint8_t bytes[EC_MAX_BYTES];
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size_t len = BN_num_bytes(&group->field.N);
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assert(sizeof(bytes) >= len);
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if (BN_is_negative(in) || BN_cmp(in, &group->field.N) >= 0 ||
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!BN_bn2bin_padded(bytes, len, in)) {
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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 ec_felem_from_bytes(group, out, bytes, len);
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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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uint8_t bytes[EC_MAX_BYTES];
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size_t len;
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ec_felem_to_bytes(group, bytes, &len, in);
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return BN_bin2bn(bytes, len, out) != NULL;
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}
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void ec_felem_to_bytes(const EC_GROUP *group, uint8_t *out, size_t *out_len,
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const EC_FELEM *in) {
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group->meth->felem_to_bytes(group, out, out_len, in);
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}
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int ec_felem_from_bytes(const EC_GROUP *group, EC_FELEM *out, const uint8_t *in,
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size_t len) {
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return group->meth->felem_from_bytes(group, out, in, len);
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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 = bn_sub_words(out->words, group->field.N.d, a->words,
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group->field.N.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.N.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.N.d, tmp.words,
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group->field.N.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.N.d, tmp.words,
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group->field.N.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.N.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.N.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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return CRYPTO_memcmp(a->words, b->words,
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group->field.N.width * sizeof(BN_ULONG)) == 0;
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}
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