/* $OpenBSD: ec2_oct.c,v 1.11 2018/07/15 16:27:39 tb Exp $ */
/* ====================================================================
* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
*
* The Elliptic Curve Public-Key Crypto Library (ECC Code) included
* herein is developed by SUN MICROSYSTEMS, INC., and is contributed
* to the OpenSSL project.
*
* The ECC Code is licensed pursuant to the OpenSSL open source
* license provided below.
*
* The software is originally written by Sheueling Chang Shantz and
* Douglas Stebila of Sun Microsystems Laboratories.
*
*/
/* ====================================================================
* 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).
*
*/
#include <openssl/opensslconf.h>
#include <openssl/err.h>
#include "ec_lcl.h"
#ifndef OPENSSL_NO_EC2M
/* Calculates and sets the affine coordinates of an EC_POINT from the given
* compressed coordinates. Uses algorithm 2.3.4 of SEC 1.
* Note that the simple implementation only uses affine coordinates.
*
* The method is from the following publication:
*
* Harper, Menezes, Vanstone:
* "Public-Key Cryptosystems with Very Small Key Lengths",
* EUROCRYPT '92, Springer-Verlag LNCS 658,
* published February 1993
*
* US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
* the same method, but claim no priority date earlier than July 29, 1994
* (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
*/
int
ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group, EC_POINT *point,
const BIGNUM *x_, int y_bit, BN_CTX *ctx)
{
BN_CTX *new_ctx = NULL;
BIGNUM *tmp, *x, *y, *z;
int ret = 0, z0;
/* clear error queue */
ERR_clear_error();
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
y_bit = (y_bit != 0) ? 1 : 0;
BN_CTX_start(ctx);
if ((tmp = BN_CTX_get(ctx)) == NULL)
goto err;
if ((x = BN_CTX_get(ctx)) == NULL)
goto err;
if ((y = BN_CTX_get(ctx)) == NULL)
goto err;
if ((z = BN_CTX_get(ctx)) == NULL)
goto err;
if (!BN_GF2m_mod_arr(x, x_, group->poly))
goto err;
if (BN_is_zero(x)) {
if (!BN_GF2m_mod_sqrt_arr(y, &group->b, group->poly, ctx))
goto err;
} else {
if (!group->meth->field_sqr(group, tmp, x, ctx))
goto err;
if (!group->meth->field_div(group, tmp, &group->b, tmp, ctx))
goto err;
if (!BN_GF2m_add(tmp, &group->a, tmp))
goto err;
if (!BN_GF2m_add(tmp, x, tmp))
goto err;
if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
unsigned long err = ERR_peek_last_error();
if (ERR_GET_LIB(err) == ERR_LIB_BN &&
ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
ERR_clear_error();
ECerror(EC_R_INVALID_COMPRESSED_POINT);
} else
ECerror(ERR_R_BN_LIB);
goto err;
}
z0 = (BN_is_odd(z)) ? 1 : 0;
if (!group->meth->field_mul(group, y, x, z, ctx))
goto err;
if (z0 != y_bit) {
if (!BN_GF2m_add(y, y, x))
goto err;
}
}
if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
goto err;
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
/* Converts an EC_POINT to an octet string.
* If buf is NULL, the encoded length will be returned.
* If the length len of buf is smaller than required an error will be returned.
*/
size_t
ec_GF2m_simple_point2oct(const EC_GROUP *group, const EC_POINT *point,
point_conversion_form_t form,
unsigned char *buf, size_t len, BN_CTX * ctx)
{
size_t ret;
BN_CTX *new_ctx = NULL;
int used_ctx = 0;
BIGNUM *x, *y, *yxi;
size_t field_len, i, skip;
if ((form != POINT_CONVERSION_COMPRESSED)
&& (form != POINT_CONVERSION_UNCOMPRESSED)
&& (form != POINT_CONVERSION_HYBRID)) {
ECerror(EC_R_INVALID_FORM);
goto err;
}
if (EC_POINT_is_at_infinity(group, point) > 0) {
/* encodes to a single 0 octet */
if (buf != NULL) {
if (len < 1) {
ECerror(EC_R_BUFFER_TOO_SMALL);
return 0;
}
buf[0] = 0;
}
return 1;
}
/* ret := required output buffer length */
field_len = (EC_GROUP_get_degree(group) + 7) / 8;
ret = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len :
1 + 2 * field_len;
/* if 'buf' is NULL, just return required length */
if (buf != NULL) {
if (len < ret) {
ECerror(EC_R_BUFFER_TOO_SMALL);
goto err;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
used_ctx = 1;
if ((x = BN_CTX_get(ctx)) == NULL)
goto err;
if ((y = BN_CTX_get(ctx)) == NULL)
goto err;
if ((yxi = BN_CTX_get(ctx)) == NULL)
goto err;
if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))
goto err;
buf[0] = form;
if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
if (!group->meth->field_div(group, yxi, y, x, ctx))
goto err;
if (BN_is_odd(yxi))
buf[0]++;
}
i = 1;
skip = field_len - BN_num_bytes(x);
if (skip > field_len) {
ECerror(ERR_R_INTERNAL_ERROR);
goto err;
}
while (skip > 0) {
buf[i++] = 0;
skip--;
}
skip = BN_bn2bin(x, buf + i);
i += skip;
if (i != 1 + field_len) {
ECerror(ERR_R_INTERNAL_ERROR);
goto err;
}
if (form == POINT_CONVERSION_UNCOMPRESSED ||
form == POINT_CONVERSION_HYBRID) {
skip = field_len - BN_num_bytes(y);
if (skip > field_len) {
ECerror(ERR_R_INTERNAL_ERROR);
goto err;
}
while (skip > 0) {
buf[i++] = 0;
skip--;
}
skip = BN_bn2bin(y, buf + i);
i += skip;
}
if (i != ret) {
ECerror(ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (used_ctx)
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
err:
if (used_ctx)
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return 0;
}
/* Converts an octet string representation to an EC_POINT.
* Note that the simple implementation only uses affine coordinates.
*/
int
ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
const unsigned char *buf, size_t len, BN_CTX *ctx)
{
point_conversion_form_t form;
int y_bit;
BN_CTX *new_ctx = NULL;
BIGNUM *x, *y, *yxi;
size_t field_len, enc_len;
int ret = 0;
if (len == 0) {
ECerror(EC_R_BUFFER_TOO_SMALL);
return 0;
}
form = buf[0];
y_bit = form & 1;
form = form & ~1U;
if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED) &&
(form != POINT_CONVERSION_UNCOMPRESSED) &&
(form != POINT_CONVERSION_HYBRID)) {
ECerror(EC_R_INVALID_ENCODING);
return 0;
}
if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
ECerror(EC_R_INVALID_ENCODING);
return 0;
}
if (form == 0) {
if (len != 1) {
ECerror(EC_R_INVALID_ENCODING);
return 0;
}
return EC_POINT_set_to_infinity(group, point);
}
field_len = (EC_GROUP_get_degree(group) + 7) / 8;
enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len :
1 + 2 * field_len;
if (len != enc_len) {
ECerror(EC_R_INVALID_ENCODING);
return 0;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((x = BN_CTX_get(ctx)) == NULL)
goto err;
if ((y = BN_CTX_get(ctx)) == NULL)
goto err;
if ((yxi = BN_CTX_get(ctx)) == NULL)
goto err;
if (!BN_bin2bn(buf + 1, field_len, x))
goto err;
if (BN_ucmp(x, &group->field) >= 0) {
ECerror(EC_R_INVALID_ENCODING);
goto err;
}
if (form == POINT_CONVERSION_COMPRESSED) {
if (!EC_POINT_set_compressed_coordinates_GF2m(group, point, x, y_bit, ctx))
goto err;
} else {
if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
goto err;
if (BN_ucmp(y, &group->field) >= 0) {
ECerror(EC_R_INVALID_ENCODING);
goto err;
}
if (form == POINT_CONVERSION_HYBRID) {
if (!group->meth->field_div(group, yxi, y, x, ctx))
goto err;
if (y_bit != BN_is_odd(yxi)) {
ECerror(EC_R_INVALID_ENCODING);
goto err;
}
}
if (!EC_POINT_set_affine_coordinates_GF2m(group, point, x, y, ctx))
goto err;
}
/* test required by X9.62 */
if (EC_POINT_is_on_curve(group, point, ctx) <= 0) {
ECerror(EC_R_POINT_IS_NOT_ON_CURVE);
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
#endif