1 /* $OpenBSD: ssl_kex.c,v 1.2 2020/04/18 14:07:56 jsing Exp $ */
2 /*
3 * Copyright (c) 2020 Joel Sing <jsing@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <stdlib.h>
19
20 #include <openssl/ec.h>
21 #include <openssl/ecdh.h>
22 #include <openssl/evp.h>
23 #include <openssl/objects.h>
24
25 #include "bytestring.h"
26
27 int
ssl_kex_dummy_ecdhe_x25519(EVP_PKEY * pkey)28 ssl_kex_dummy_ecdhe_x25519(EVP_PKEY *pkey)
29 {
30 EC_GROUP *group = NULL;
31 EC_POINT *point = NULL;
32 EC_KEY *ec_key = NULL;
33 BIGNUM *order = NULL;
34 int ret = 0;
35
36 /* Fudge up an EC_KEY that looks like X25519... */
37 if ((group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1)) == NULL)
38 goto err;
39 if ((point = EC_POINT_new(group)) == NULL)
40 goto err;
41 if ((order = BN_new()) == NULL)
42 goto err;
43 if (!BN_set_bit(order, 252))
44 goto err;
45 if (!EC_GROUP_set_generator(group, point, order, NULL))
46 goto err;
47 EC_GROUP_set_curve_name(group, NID_X25519);
48 if ((ec_key = EC_KEY_new()) == NULL)
49 goto err;
50 if (!EC_KEY_set_group(ec_key, group))
51 goto err;
52 if (!EVP_PKEY_set1_EC_KEY(pkey, ec_key))
53 goto err;
54
55 ret = 1;
56
57 err:
58 EC_GROUP_free(group);
59 EC_POINT_free(point);
60 EC_KEY_free(ec_key);
61 BN_free(order);
62
63 return ret;
64 }
65
66 int
ssl_kex_generate_ecdhe_ecp(EC_KEY * ecdh,int nid)67 ssl_kex_generate_ecdhe_ecp(EC_KEY *ecdh, int nid)
68 {
69 EC_GROUP *group;
70 int ret = 0;
71
72 if ((group = EC_GROUP_new_by_curve_name(nid)) == NULL)
73 goto err;
74
75 if (!EC_KEY_set_group(ecdh, group))
76 goto err;
77 if (!EC_KEY_generate_key(ecdh))
78 goto err;
79
80 ret = 1;
81
82 err:
83 EC_GROUP_free(group);
84
85 return ret;
86 }
87
88 int
ssl_kex_public_ecdhe_ecp(EC_KEY * ecdh,CBB * cbb)89 ssl_kex_public_ecdhe_ecp(EC_KEY *ecdh, CBB *cbb)
90 {
91 const EC_GROUP *group;
92 const EC_POINT *point;
93 uint8_t *ecp;
94 size_t ecp_len;
95 int ret = 0;
96
97 if ((group = EC_KEY_get0_group(ecdh)) == NULL)
98 goto err;
99 if ((point = EC_KEY_get0_public_key(ecdh)) == NULL)
100 goto err;
101
102 if ((ecp_len = EC_POINT_point2oct(group, point,
103 POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL)) == 0)
104 goto err;
105 if (!CBB_add_space(cbb, &ecp, ecp_len))
106 goto err;
107 if ((EC_POINT_point2oct(group, point, POINT_CONVERSION_UNCOMPRESSED,
108 ecp, ecp_len, NULL)) == 0)
109 goto err;
110
111 ret = 1;
112
113 err:
114 return ret;
115 }
116
117 int
ssl_kex_peer_public_ecdhe_ecp(EC_KEY * ecdh,int nid,CBS * cbs)118 ssl_kex_peer_public_ecdhe_ecp(EC_KEY *ecdh, int nid, CBS *cbs)
119 {
120 EC_GROUP *group = NULL;
121 EC_POINT *point = NULL;
122 int ret = 0;
123
124 if ((group = EC_GROUP_new_by_curve_name(nid)) == NULL)
125 goto err;
126
127 if (!EC_KEY_set_group(ecdh, group))
128 goto err;
129
130 if ((point = EC_POINT_new(group)) == NULL)
131 goto err;
132 if (EC_POINT_oct2point(group, point, CBS_data(cbs), CBS_len(cbs),
133 NULL) == 0)
134 goto err;
135 if (!EC_KEY_set_public_key(ecdh, point))
136 goto err;
137
138 ret = 1;
139
140 err:
141 EC_GROUP_free(group);
142 EC_POINT_free(point);
143
144 return ret;
145 }
146
147 int
ssl_kex_derive_ecdhe_ecp(EC_KEY * ecdh,EC_KEY * ecdh_peer,uint8_t ** shared_key,size_t * shared_key_len)148 ssl_kex_derive_ecdhe_ecp(EC_KEY *ecdh, EC_KEY *ecdh_peer,
149 uint8_t **shared_key, size_t *shared_key_len)
150 {
151 const EC_POINT *point;
152 uint8_t *sk = NULL;
153 int sk_len = 0;
154 int ret = 0;
155
156 if (!EC_GROUP_check(EC_KEY_get0_group(ecdh), NULL))
157 goto err;
158 if (!EC_GROUP_check(EC_KEY_get0_group(ecdh_peer), NULL))
159 goto err;
160
161 if ((point = EC_KEY_get0_public_key(ecdh_peer)) == NULL)
162 goto err;
163
164 if ((sk_len = ECDH_size(ecdh)) <= 0)
165 goto err;
166 if ((sk = calloc(1, sk_len)) == NULL)
167 goto err;
168
169 if (ECDH_compute_key(sk, sk_len, point, ecdh, NULL) <= 0)
170 goto err;
171
172 *shared_key = sk;
173 *shared_key_len = sk_len;
174 sk = NULL;
175
176 ret = 1;
177
178 err:
179 freezero(sk, sk_len);
180
181 return ret;
182 }
183