crypto/ec/ec_check.c

   1 /*
   2  * Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include "ec_local.h"
  11 #include <openssl/err.h>
  12
  13 int EC_GROUP_check(const EC_GROUP *group, BN_CTX *ctx)
  14 {
  15     int ret = 0;
  16     const BIGNUM *order;
  17     BN_CTX *new_ctx = NULL;
  18     EC_POINT *point = NULL;
  19
  20     /* Custom curves assumed to be correct */
  21     if ((group->meth->flags & EC_FLAGS_CUSTOM_CURVE) != 0)
  22         return 1;
  23
  24     if (ctx == NULL) {
  25         ctx = new_ctx = BN_CTX_new();
  26         if (ctx == NULL) {
  27             ECerr(EC_F_EC_GROUP_CHECK, ERR_R_MALLOC_FAILURE);
  28             goto err;
  29         }
  30     }
  31
  32     /* check the discriminant */
  33     if (!EC_GROUP_check_discriminant(group, ctx)) {
  34         ECerr(EC_F_EC_GROUP_CHECK, EC_R_DISCRIMINANT_IS_ZERO);
  35         goto err;
  36     }
  37
  38     /* check the generator */
  39     if (group->generator == NULL) {
  40         ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_GENERATOR);
  41         goto err;
  42     }
  43     if (EC_POINT_is_on_curve(group, group->generator, ctx) <= 0) {
  44         ECerr(EC_F_EC_GROUP_CHECK, EC_R_POINT_IS_NOT_ON_CURVE);
  45         goto err;
  46     }
  47
  48     /* check the order of the generator */
  49     if ((point = EC_POINT_new(group)) == NULL)
  50         goto err;
  51     order = EC_GROUP_get0_order(group);
  52     if (order == NULL)
  53         goto err;
  54     if (BN_is_zero(order)) {
  55         ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_ORDER);
  56         goto err;
  57     }
  58
  59     if (!EC_POINT_mul(group, point, order, NULL, NULL, ctx))
  60         goto err;
  61     if (!EC_POINT_is_at_infinity(group, point)) {
  62         ECerr(EC_F_EC_GROUP_CHECK, EC_R_INVALID_GROUP_ORDER);
  63         goto err;
  64     }
  65
  66     ret = 1;
  67
  68  err:
  69     BN_CTX_free(new_ctx);
  70     EC_POINT_free(point);
  71     return ret;
  72 }