crypto/ec/ecp_oct.c

/* crypto/ec/ecp_oct.c */
/* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
 * for the OpenSSL project. 
 * Includes code written by Bodo Moeller for the OpenSSL project.
*/
/* ====================================================================
 * Copyright (c) 1998-2002 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).
 *
 */
/* ====================================================================
 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
 * Portions of this software developed by SUN MICROSYSTEMS, INC.,
 * and contributed to the OpenSSL project.
 */

#include <openssl/err.h>
#include <openssl/symhacks.h>

#include "ec_lcl.h"

int ec_GFp_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 *tmp1, *tmp2, *x, *y;
	int ret = 0;

	/* 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);

	BN_CTX_start(ctx);
	tmp1 = BN_CTX_get(ctx);
	tmp2 = BN_CTX_get(ctx);
	x = BN_CTX_get(ctx);
	y = BN_CTX_get(ctx);
	if (y == NULL) goto err;

	/* Recover y.  We have a Weierstrass equation
	 *     y^2 = x^3 + a*x + b,
	 * so  y  is one of the square roots of  x^3 + a*x + b.
	 */

	/* tmp1 := x^3 */
	if (!BN_nnmod(x, x_, &group->field,ctx)) goto err;
	if (group->meth->field_decode == 0)
		{
		/* field_{sqr,mul} work on standard representation */
		if (!group->meth->field_sqr(group, tmp2, x_, ctx)) goto err;
		if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx)) goto err;
		}
	else
		{
		if (!BN_mod_sqr(tmp2, x_, &group->field, ctx)) goto err;
		if (!BN_mod_mul(tmp1, tmp2, x_, &group->field, ctx)) goto err;
		}
	
	/* tmp1 := tmp1 + a*x */
	if (group->a_is_minus3)
		{
		if (!BN_mod_lshift1_quick(tmp2, x, &group->field)) goto err;
		if (!BN_mod_add_quick(tmp2, tmp2, x, &group->field)) goto err;
		if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, &group->field)) goto err;
		}
	else
		{
		if (group->meth->field_decode)
			{
			if (!group->meth->field_decode(group, tmp2, &group->a, ctx)) goto err;
			if (!BN_mod_mul(tmp2, tmp2, x, &group->field, ctx)) goto err;
			}
		else
			{
			/* field_mul works on standard representation */
			if (!group->meth->field_mul(group, tmp2, &group->a, x, ctx)) goto err;
			}
		
		if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) goto err;
		}
	
	/* tmp1 := tmp1 + b */
	if (group->meth->field_decode)
		{
		if (!group->meth->field_decode(group, tmp2, &group->b, ctx)) goto err;
		if (!BN_mod_add_quick(tmp1, tmp1, tmp2, &group->field)) goto err;
		}
	else
		{
		if (!BN_mod_add_quick(tmp1, tmp1, &group->b, &group->field)) goto err;
		}
	
	if (!BN_mod_sqrt(y, tmp1, &group->field, ctx))
		{
		unsigned long err = ERR_peek_last_error();
		
		if (ERR_GET_LIB(err) == ERR_LIB_BN && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE)
			{
			ERR_clear_error();
			ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT);
			}
		else
			ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_BN_LIB);
		goto err;
		}

	if (y_bit != BN_is_odd(y))
		{
		if (BN_is_zero(y))
			{
			int kron;

			kron = BN_kronecker(x, &group->field, ctx);
			if (kron == -2) goto err;

			if (kron == 1)
				ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSION_BIT);
			else
				/* BN_mod_sqrt() should have cought this error (not a square) */
				ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, EC_R_INVALID_COMPRESSED_POINT);
			goto err;
			}
		if (!BN_usub(y, &group->field, y)) goto err;
		}
	if (y_bit != BN_is_odd(y))
		{
		ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES, ERR_R_INTERNAL_ERROR);
		goto err;
		}

	if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err;

	ret = 1;

 err:
	BN_CTX_end(ctx);
	if (new_ctx != NULL)
		BN_CTX_free(new_ctx);
	return ret;
	}


size_t ec_GFp_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;
	size_t field_len, i, skip;

	if ((form != POINT_CONVERSION_COMPRESSED)
		&& (form != POINT_CONVERSION_UNCOMPRESSED)
		&& (form != POINT_CONVERSION_HYBRID))
		{
		ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
		goto err;
		}

	if (EC_POINT_is_at_infinity(group, point))
		{
		/* encodes to a single 0 octet */
		if (buf != NULL)
			{
			if (len < 1)
				{
				ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
				return 0;
				}
			buf[0] = 0;
			}
		return 1;
		}


	/* ret := required output buffer length */
	field_len = BN_num_bytes(&group->field);
	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)
			{
			ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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;
		x = BN_CTX_get(ctx);
		y = BN_CTX_get(ctx);
		if (y == NULL) goto err;

		if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx)) goto err;

		if ((form == POINT_CONVERSION_COMPRESSED || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y))
			buf[0] = form + 1;
		else
			buf[0] = form;
	
		i = 1;
		
		skip = field_len - BN_num_bytes(x);
		if (skip > field_len)
			{
			ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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)
			{
			ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, 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)
				{
				ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
				goto err;
				}
			while (skip > 0)
				{
				buf[i++] = 0;
				skip--;
				}
			skip = BN_bn2bin(y, buf + i);
			i += skip;
			}

		if (i != ret)
			{
			ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
			goto err;
			}
		}
	
	if (used_ctx)
		BN_CTX_end(ctx);
	if (new_ctx != NULL)
		BN_CTX_free(new_ctx);
	return ret;

 err:
	if (used_ctx)
		BN_CTX_end(ctx);
	if (new_ctx != NULL)
		BN_CTX_free(new_ctx);
	return 0;
	}


int ec_GFp_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;
	size_t field_len, enc_len;
	int ret = 0;

	if (len == 0)
		{
		ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, 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))
		{
		ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
		return 0;
		}
	if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit)
		{
		ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
		return 0;
		}

	if (form == 0)
		{
		if (len != 1)
			{
			ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
			return 0;
			}

		return EC_POINT_set_to_infinity(group, point);
		}
	
	field_len = BN_num_bytes(&group->field);
	enc_len = (form == POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2*field_len;

	if (len != enc_len)
		{
		ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
		return 0;
		}

	if (ctx == NULL)
		{
		ctx = new_ctx = BN_CTX_new();
		if (ctx == NULL)
			return 0;
		}

	BN_CTX_start(ctx);
	x = BN_CTX_get(ctx);
	y = BN_CTX_get(ctx);
	if (y == NULL) goto err;

	if (!BN_bin2bn(buf + 1, field_len, x)) goto err;
	if (BN_ucmp(x, &group->field) >= 0)
		{
		ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
		goto err;
		}

	if (form == POINT_CONVERSION_COMPRESSED)
		{
		if (!EC_POINT_set_compressed_coordinates_GFp(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)
			{
			ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
			goto err;
			}
		if (form == POINT_CONVERSION_HYBRID)
			{
			if (y_bit != BN_is_odd(y))
				{
				ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
				goto err;
				}
			}

		if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) goto err;
		}
	
	if (!EC_POINT_is_on_curve(group, point, ctx)) /* test required by X9.62 */
		{
		ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
		goto err;
		}

	ret = 1;
	
 err:
	BN_CTX_end(ctx);
	if (new_ctx != NULL)
		BN_CTX_free(new_ctx);
	return ret;
	}