354 lines
10 KiB
C
354 lines
10 KiB
C
/*
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* Copyright 2011-2016 The OpenSSL Project Authors. 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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/* ====================================================================
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* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
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*
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* The Elliptic Curve Public-Key Crypto Library (ECC Code) included
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* herein is developed by SUN MICROSYSTEMS, INC., and is contributed
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* to the OpenSSL project.
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*
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* The ECC Code is licensed pursuant to the OpenSSL open source
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* license provided below.
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*
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* The software is originally written by Sheueling Chang Shantz and
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* Douglas Stebila of Sun Microsystems Laboratories.
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*
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*/
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#include <openssl/err.h>
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#include "ec_lcl.h"
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#ifndef OPENSSL_NO_EC2M
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/*-
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* Calculates and sets the affine coordinates of an EC_POINT from the given
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* compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
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* Note that the simple implementation only uses affine coordinates.
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*
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* The method is from the following publication:
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*
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* Harper, Menezes, Vanstone:
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* "Public-Key Cryptosystems with Very Small Key Lengths",
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* EUROCRYPT '92, Springer-Verlag LNCS 658,
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* published February 1993
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*
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* US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
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* the same method, but claim no priority date earlier than July 29, 1994
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* (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
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*/
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int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group,
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EC_POINT *point,
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const BIGNUM *x_, int y_bit,
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BN_CTX *ctx)
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{
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BN_CTX *new_ctx = NULL;
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BIGNUM *tmp, *x, *y, *z;
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int ret = 0, z0;
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/* clear error queue */
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ERR_clear_error();
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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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return 0;
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}
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y_bit = (y_bit != 0) ? 1 : 0;
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BN_CTX_start(ctx);
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tmp = BN_CTX_get(ctx);
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x = BN_CTX_get(ctx);
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y = BN_CTX_get(ctx);
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z = BN_CTX_get(ctx);
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if (z == NULL)
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goto err;
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if (!BN_GF2m_mod_arr(x, x_, group->poly))
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goto err;
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if (BN_is_zero(x)) {
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if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx))
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goto err;
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} else {
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if (!group->meth->field_sqr(group, tmp, x, ctx))
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goto err;
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if (!group->meth->field_div(group, tmp, group->b, tmp, ctx))
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goto err;
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if (!BN_GF2m_add(tmp, group->a, tmp))
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goto err;
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if (!BN_GF2m_add(tmp, x, tmp))
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goto err;
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if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
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unsigned long err = ERR_peek_last_error();
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if (ERR_GET_LIB(err) == ERR_LIB_BN
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&& ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
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ERR_clear_error();
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ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
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EC_R_INVALID_COMPRESSED_POINT);
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} else
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ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
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ERR_R_BN_LIB);
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goto err;
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}
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z0 = (BN_is_odd(z)) ? 1 : 0;
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if (!group->meth->field_mul(group, y, x, z, ctx))
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goto err;
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if (z0 != y_bit) {
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if (!BN_GF2m_add(y, y, x))
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goto err;
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}
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}
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if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
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goto err;
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ret = 1;
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err:
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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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/*
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* Converts an EC_POINT to an octet string. If buf is NULL, the encoded
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* length will be returned. If the length len of buf is smaller than required
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* an error will be returned.
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*/
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size_t ec_GF2m_simple_point2oct(const EC_GROUP *group, const EC_POINT *point,
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point_conversion_form_t form,
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unsigned char *buf, size_t len, BN_CTX *ctx)
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{
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size_t ret;
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BN_CTX *new_ctx = NULL;
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int used_ctx = 0;
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BIGNUM *x, *y, *yxi;
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size_t field_len, i, skip;
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if ((form != POINT_CONVERSION_COMPRESSED)
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&& (form != POINT_CONVERSION_UNCOMPRESSED)
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&& (form != POINT_CONVERSION_HYBRID)) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
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goto err;
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}
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if (EC_POINT_is_at_infinity(group, point)) {
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/* encodes to a single 0 octet */
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if (buf != NULL) {
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if (len < 1) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
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return 0;
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}
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buf[0] = 0;
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}
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return 1;
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}
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/* ret := required output buffer length */
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field_len = (EC_GROUP_get_degree(group) + 7) / 8;
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ret =
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(form ==
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POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
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/* if 'buf' is NULL, just return required length */
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if (buf != NULL) {
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if (len < ret) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
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goto err;
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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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return 0;
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}
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BN_CTX_start(ctx);
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used_ctx = 1;
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x = BN_CTX_get(ctx);
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y = BN_CTX_get(ctx);
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yxi = BN_CTX_get(ctx);
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if (yxi == NULL)
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goto err;
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if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))
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goto err;
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buf[0] = form;
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if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
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if (!group->meth->field_div(group, yxi, y, x, ctx))
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goto err;
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if (BN_is_odd(yxi))
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buf[0]++;
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}
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i = 1;
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skip = field_len - BN_num_bytes(x);
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if (skip > field_len) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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while (skip > 0) {
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buf[i++] = 0;
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skip--;
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}
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skip = BN_bn2bin(x, buf + i);
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i += skip;
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if (i != 1 + field_len) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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if (form == POINT_CONVERSION_UNCOMPRESSED
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|| form == POINT_CONVERSION_HYBRID) {
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skip = field_len - BN_num_bytes(y);
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if (skip > field_len) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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while (skip > 0) {
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buf[i++] = 0;
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skip--;
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}
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skip = BN_bn2bin(y, buf + i);
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i += skip;
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}
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if (i != ret) {
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ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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goto err;
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}
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}
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if (used_ctx)
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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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err:
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if (used_ctx)
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BN_CTX_end(ctx);
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BN_CTX_free(new_ctx);
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return 0;
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}
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/*
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* Converts an octet string representation to an EC_POINT. Note that the
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* simple implementation only uses affine coordinates.
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*/
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int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
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const unsigned char *buf, size_t len,
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BN_CTX *ctx)
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{
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point_conversion_form_t form;
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int y_bit;
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BN_CTX *new_ctx = NULL;
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BIGNUM *x, *y, *yxi;
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size_t field_len, enc_len;
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int ret = 0;
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if (len == 0) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
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return 0;
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}
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form = buf[0];
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y_bit = form & 1;
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form = form & ~1U;
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if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
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&& (form != POINT_CONVERSION_UNCOMPRESSED)
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&& (form != POINT_CONVERSION_HYBRID)) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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return 0;
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}
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if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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return 0;
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}
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if (form == 0) {
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if (len != 1) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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return 0;
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}
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return EC_POINT_set_to_infinity(group, point);
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}
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field_len = (EC_GROUP_get_degree(group) + 7) / 8;
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enc_len =
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(form ==
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POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
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if (len != enc_len) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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return 0;
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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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return 0;
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}
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BN_CTX_start(ctx);
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x = BN_CTX_get(ctx);
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y = BN_CTX_get(ctx);
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yxi = BN_CTX_get(ctx);
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if (yxi == NULL)
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goto err;
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if (!BN_bin2bn(buf + 1, field_len, x))
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goto err;
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if (BN_ucmp(x, group->field) >= 0) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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goto err;
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}
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if (form == POINT_CONVERSION_COMPRESSED) {
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if (!EC_POINT_set_compressed_coordinates_GF2m
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(group, point, x, y_bit, ctx))
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goto err;
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} else {
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if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
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goto err;
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if (BN_ucmp(y, group->field) >= 0) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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goto err;
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}
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if (form == POINT_CONVERSION_HYBRID) {
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if (!group->meth->field_div(group, yxi, y, x, ctx))
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goto err;
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if (y_bit != BN_is_odd(yxi)) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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goto err;
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}
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}
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if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
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goto err;
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}
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/* test required by X9.62 */
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if (EC_POINT_is_on_curve(group, point, ctx) <= 0) {
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ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
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goto err;
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}
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ret = 1;
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err:
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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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#endif
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