crypto/ec/ec_check.c

   1 /* ====================================================================
   2  * Copyright (c) 1998-2002 The OpenSSL Project.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  *
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in
  13  *    the documentation and/or other materials provided with the
  14  *    distribution.
  15  *
  16  * 3. All advertising materials mentioning features or use of this
  17  *    software must display the following acknowledgment:
  18  *    "This product includes software developed by the OpenSSL Project
  19  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  20  *
  21  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  22  *    endorse or promote products derived from this software without
  23  *    prior written permission. For written permission, please contact
  24  *    openssl-core@openssl.org.
  25  *
  26  * 5. Products derived from this software may not be called "OpenSSL"
  27  *    nor may "OpenSSL" appear in their names without prior written
  28  *    permission of the OpenSSL Project.
  29  *
  30  * 6. Redistributions of any form whatsoever must retain the following
  31  *    acknowledgment:
  32  *    "This product includes software developed by the OpenSSL Project
  33  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  36  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  38  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  39  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  40  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  41  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  42  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  43  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  44  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  45  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  46  * OF THE POSSIBILITY OF SUCH DAMAGE.
  47  * ====================================================================
  48  *
  49  * This product includes cryptographic software written by Eric Young
  50  * (eay@cryptsoft.com).  This product includes software written by Tim
  51  * Hudson (tjh@cryptsoft.com).
  52  *
  53  */
  54
  55 #include "ec_lcl.h"
  56 #include <openssl/err.h>
  57
  58 int EC_GROUP_check(const EC_GROUP *group, BN_CTX *ctx)
  59 {
  60     int ret = 0;
  61     BIGNUM *order;
  62     BN_CTX *new_ctx = NULL;
  63     EC_POINT *point = NULL;
  64
  65     if (ctx == NULL) {
  66         ctx = new_ctx = BN_CTX_new();
  67         if (ctx == NULL) {
  68             ECerr(EC_F_EC_GROUP_CHECK, ERR_R_MALLOC_FAILURE);
  69             goto err;
  70         }
  71     }
  72     BN_CTX_start(ctx);
  73     if ((order = BN_CTX_get(ctx)) == NULL)
  74         goto err;
  75
  76     /* check the discriminant */
  77     if (!EC_GROUP_check_discriminant(group, ctx)) {
  78         ECerr(EC_F_EC_GROUP_CHECK, EC_R_DISCRIMINANT_IS_ZERO);
  79         goto err;
  80     }
  81
  82     /* check the generator */
  83     if (group->generator == NULL) {
  84         ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_GENERATOR);
  85         goto err;
  86     }
  87     if (EC_POINT_is_on_curve(group, group->generator, ctx) <= 0) {
  88         ECerr(EC_F_EC_GROUP_CHECK, EC_R_POINT_IS_NOT_ON_CURVE);
  89         goto err;
  90     }
  91
  92     /* check the order of the generator */
  93     if ((point = EC_POINT_new(group)) == NULL)
  94         goto err;
  95     if (!EC_GROUP_get_order(group, order, ctx))
  96         goto err;
  97     if (BN_is_zero(order)) {
  98         ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_ORDER);
  99         goto err;
 100     }
 101
 102     if (!EC_POINT_mul(group, point, order, NULL, NULL, ctx))
 103         goto err;
 104     if (!EC_POINT_is_at_infinity(group, point)) {
 105         ECerr(EC_F_EC_GROUP_CHECK, EC_R_INVALID_GROUP_ORDER);
 106         goto err;
 107     }
 108
 109     ret = 1;
 110
 111  err:
 112     if (ctx != NULL)
 113         BN_CTX_end(ctx);
 114     BN_CTX_free(new_ctx);
 115     EC_POINT_free(point);
 116     return ret;
 117 }