1 /*
2 * Example ECDHE with Curve25519 program
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 #include "mbedtls/build_info.h"
21
22 #include "mbedtls/platform.h"
23
24 #if !defined(MBEDTLS_ECDH_C) || \
25 !defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED) || \
26 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C)
main(void)27 int main(void)
28 {
29 mbedtls_printf("MBEDTLS_ECDH_C and/or "
30 "MBEDTLS_ECP_DP_CURVE25519_ENABLED and/or "
31 "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C "
32 "not defined\n");
33 mbedtls_exit(0);
34 }
35 #else
36
37 #include "mbedtls/entropy.h"
38 #include "mbedtls/ctr_drbg.h"
39 #include "mbedtls/ecdh.h"
40
41 #include <string.h>
42
43
main(int argc,char * argv[])44 int main(int argc, char *argv[])
45 {
46 int ret = 1;
47 int exit_code = MBEDTLS_EXIT_FAILURE;
48 mbedtls_ecdh_context ctx_cli, ctx_srv;
49 mbedtls_entropy_context entropy;
50 mbedtls_ctr_drbg_context ctr_drbg;
51 unsigned char cli_to_srv[36], srv_to_cli[33];
52 const char pers[] = "ecdh";
53
54 size_t srv_olen;
55 size_t cli_olen;
56 unsigned char secret_cli[32] = { 0 };
57 unsigned char secret_srv[32] = { 0 };
58 const unsigned char *p_cli_to_srv = cli_to_srv;
59
60 ((void) argc);
61 ((void) argv);
62
63 mbedtls_ecdh_init(&ctx_cli);
64 mbedtls_ecdh_init(&ctx_srv);
65 mbedtls_ctr_drbg_init(&ctr_drbg);
66
67 /*
68 * Initialize random number generation
69 */
70 mbedtls_printf(" . Seed the random number generator...");
71 fflush(stdout);
72
73 mbedtls_entropy_init(&entropy);
74 if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func,
75 &entropy,
76 (const unsigned char *) pers,
77 sizeof(pers))) != 0) {
78 mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n",
79 ret);
80 goto exit;
81 }
82
83 mbedtls_printf(" ok\n");
84
85 /*
86 * Client: initialize context and generate keypair
87 */
88 mbedtls_printf(" . Set up client context, generate EC key pair...");
89 fflush(stdout);
90
91 ret = mbedtls_ecdh_setup(&ctx_cli, MBEDTLS_ECP_DP_CURVE25519);
92 if (ret != 0) {
93 mbedtls_printf(" failed\n ! mbedtls_ecdh_setup returned %d\n", ret);
94 goto exit;
95 }
96
97 ret = mbedtls_ecdh_make_params(&ctx_cli, &cli_olen, cli_to_srv,
98 sizeof(cli_to_srv),
99 mbedtls_ctr_drbg_random, &ctr_drbg);
100 if (ret != 0) {
101 mbedtls_printf(" failed\n ! mbedtls_ecdh_make_params returned %d\n",
102 ret);
103 goto exit;
104 }
105
106 mbedtls_printf(" ok\n");
107
108 /*
109 * Server: initialize context and generate keypair
110 */
111 mbedtls_printf(" . Server: read params, generate public key...");
112 fflush(stdout);
113
114 ret = mbedtls_ecdh_read_params(&ctx_srv, &p_cli_to_srv,
115 p_cli_to_srv + sizeof(cli_to_srv));
116 if (ret != 0) {
117 mbedtls_printf(" failed\n ! mbedtls_ecdh_read_params returned %d\n",
118 ret);
119 goto exit;
120 }
121
122 ret = mbedtls_ecdh_make_public(&ctx_srv, &srv_olen, srv_to_cli,
123 sizeof(srv_to_cli),
124 mbedtls_ctr_drbg_random, &ctr_drbg);
125 if (ret != 0) {
126 mbedtls_printf(" failed\n ! mbedtls_ecdh_make_public returned %d\n",
127 ret);
128 goto exit;
129 }
130
131 mbedtls_printf(" ok\n");
132
133 /*
134 * Client: read public key
135 */
136 mbedtls_printf(" . Client: read public key...");
137 fflush(stdout);
138
139 ret = mbedtls_ecdh_read_public(&ctx_cli, srv_to_cli,
140 sizeof(srv_to_cli));
141 if (ret != 0) {
142 mbedtls_printf(" failed\n ! mbedtls_ecdh_read_public returned %d\n",
143 ret);
144 goto exit;
145 }
146
147 mbedtls_printf(" ok\n");
148
149 /*
150 * Calculate secrets
151 */
152 mbedtls_printf(" . Calculate secrets...");
153 fflush(stdout);
154
155 ret = mbedtls_ecdh_calc_secret(&ctx_cli, &cli_olen, secret_cli,
156 sizeof(secret_cli),
157 mbedtls_ctr_drbg_random, &ctr_drbg);
158 if (ret != 0) {
159 mbedtls_printf(" failed\n ! mbedtls_ecdh_calc_secret returned %d\n",
160 ret);
161 goto exit;
162 }
163
164 ret = mbedtls_ecdh_calc_secret(&ctx_srv, &srv_olen, secret_srv,
165 sizeof(secret_srv),
166 mbedtls_ctr_drbg_random, &ctr_drbg);
167 if (ret != 0) {
168 mbedtls_printf(" failed\n ! mbedtls_ecdh_calc_secret returned %d\n",
169 ret);
170 goto exit;
171 }
172
173 mbedtls_printf(" ok\n");
174
175 /*
176 * Verification: are the computed secrets equal?
177 */
178 mbedtls_printf(" . Check if both calculated secrets are equal...");
179 fflush(stdout);
180
181 ret = memcmp(secret_srv, secret_cli, srv_olen);
182 if (ret != 0 || (cli_olen != srv_olen)) {
183 mbedtls_printf(" failed\n ! Shared secrets not equal.\n");
184 goto exit;
185 }
186
187 mbedtls_printf(" ok\n");
188
189 exit_code = MBEDTLS_EXIT_SUCCESS;
190
191 exit:
192
193 mbedtls_ecdh_free(&ctx_srv);
194 mbedtls_ecdh_free(&ctx_cli);
195 mbedtls_ctr_drbg_free(&ctr_drbg);
196 mbedtls_entropy_free(&entropy);
197
198 mbedtls_exit(exit_code);
199 }
200 #endif /* MBEDTLS_ECDH_C && MBEDTLS_ECP_DP_CURVE25519_ENABLED &&
201 MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C */
202