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 
EC_GROUP_check(const EC_GROUP * group,BN_CTX * ctx)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 }
73