ec_check.c

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/* crypto/ec/ec_check.c */
/* ====================================================================
 * 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
 *    [email protected].
 *
 * 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
 * ([email protected]).  This product includes software written by Tim
 * Hudson ([email protected]).
 *
 */

#include "ec_lcl.h"
#include <openssl/err.h>

int EC_GROUP_check(const EC_GROUP *group, BN_CTX *ctx)
    {
    int ret = 0;
    BIGNUM *order;
    BN_CTX *new_ctx = NULL;
    EC_POINT *point = NULL;

    if (ctx == NULL)
        {
        ctx = new_ctx = BN_CTX_new();
        if (ctx == NULL)
            {
            ECerr(EC_F_EC_GROUP_CHECK, ERR_R_MALLOC_FAILURE);
            goto err;
            }
        }
    BN_CTX_start(ctx);
    if ((order = BN_CTX_get(ctx)) == NULL) goto err;

    /* check the discriminant */
    if (!EC_GROUP_check_discriminant(group, ctx))
        {
        ECerr(EC_F_EC_GROUP_CHECK, EC_R_DISCRIMINANT_IS_ZERO);
        goto err;
        }

    /* check the generator */
    if (group->generator == NULL)
        {
        ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_GENERATOR);
        goto err;
        }
    if (!EC_POINT_is_on_curve(group, group->generator, ctx))
        {
        ECerr(EC_F_EC_GROUP_CHECK, EC_R_POINT_IS_NOT_ON_CURVE);
        goto err;
        }

    /* check the order of the generator */
    if ((point = EC_POINT_new(group)) == NULL) goto err;
    if (!EC_GROUP_get_order(group, order, ctx)) goto err; 
    if (BN_is_zero(order))
        {
        ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_ORDER);
        goto err;
        }
    
    if (!EC_POINT_mul(group, point, order, NULL, NULL, ctx)) goto err;
    if (!EC_POINT_is_at_infinity(group, point))
        {
        ECerr(EC_F_EC_GROUP_CHECK, EC_R_INVALID_GROUP_ORDER);
        goto err;
        }

    ret = 1;

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