1 /*
2 * Example ECDHE with Curve25519 program
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 */
7
8 #include "mbedtls/build_info.h"
9
10 #include "mbedtls/platform.h"
11
12 #if !defined(MBEDTLS_ECDH_C) || \
13 !defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED) || \
14 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C)
main(void)15 int main(void)
16 {
17 mbedtls_printf("MBEDTLS_ECDH_C and/or "
18 "MBEDTLS_ECP_DP_CURVE25519_ENABLED and/or "
19 "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C "
20 "not defined\n");
21 mbedtls_exit(0);
22 }
23 #else
24
25 #include "mbedtls/entropy.h"
26 #include "mbedtls/ctr_drbg.h"
27 #include "mbedtls/ecdh.h"
28
29 #include <string.h>
30
31
main(int argc,char * argv[])32 int main(int argc, char *argv[])
33 {
34 int ret = 1;
35 int exit_code = MBEDTLS_EXIT_FAILURE;
36 mbedtls_ecdh_context ctx_cli, ctx_srv;
37 mbedtls_entropy_context entropy;
38 mbedtls_ctr_drbg_context ctr_drbg;
39 unsigned char cli_to_srv[36], srv_to_cli[33];
40 const char pers[] = "ecdh";
41
42 size_t srv_olen;
43 size_t cli_olen;
44 unsigned char secret_cli[32] = { 0 };
45 unsigned char secret_srv[32] = { 0 };
46 const unsigned char *p_cli_to_srv = cli_to_srv;
47
48 ((void) argc);
49 ((void) argv);
50
51 mbedtls_ecdh_init(&ctx_cli);
52 mbedtls_ecdh_init(&ctx_srv);
53 mbedtls_ctr_drbg_init(&ctr_drbg);
54
55 /*
56 * Initialize random number generation
57 */
58 mbedtls_printf(" . Seed the random number generator...");
59 fflush(stdout);
60
61 mbedtls_entropy_init(&entropy);
62 if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func,
63 &entropy,
64 (const unsigned char *) pers,
65 sizeof(pers))) != 0) {
66 mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n",
67 ret);
68 goto exit;
69 }
70
71 mbedtls_printf(" ok\n");
72
73 /*
74 * Client: initialize context and generate keypair
75 */
76 mbedtls_printf(" . Set up client context, generate EC key pair...");
77 fflush(stdout);
78
79 ret = mbedtls_ecdh_setup(&ctx_cli, MBEDTLS_ECP_DP_CURVE25519);
80 if (ret != 0) {
81 mbedtls_printf(" failed\n ! mbedtls_ecdh_setup returned %d\n", ret);
82 goto exit;
83 }
84
85 ret = mbedtls_ecdh_make_params(&ctx_cli, &cli_olen, cli_to_srv,
86 sizeof(cli_to_srv),
87 mbedtls_ctr_drbg_random, &ctr_drbg);
88 if (ret != 0) {
89 mbedtls_printf(" failed\n ! mbedtls_ecdh_make_params returned %d\n",
90 ret);
91 goto exit;
92 }
93
94 mbedtls_printf(" ok\n");
95
96 /*
97 * Server: initialize context and generate keypair
98 */
99 mbedtls_printf(" . Server: read params, generate public key...");
100 fflush(stdout);
101
102 ret = mbedtls_ecdh_read_params(&ctx_srv, &p_cli_to_srv,
103 p_cli_to_srv + sizeof(cli_to_srv));
104 if (ret != 0) {
105 mbedtls_printf(" failed\n ! mbedtls_ecdh_read_params returned %d\n",
106 ret);
107 goto exit;
108 }
109
110 ret = mbedtls_ecdh_make_public(&ctx_srv, &srv_olen, srv_to_cli,
111 sizeof(srv_to_cli),
112 mbedtls_ctr_drbg_random, &ctr_drbg);
113 if (ret != 0) {
114 mbedtls_printf(" failed\n ! mbedtls_ecdh_make_public returned %d\n",
115 ret);
116 goto exit;
117 }
118
119 mbedtls_printf(" ok\n");
120
121 /*
122 * Client: read public key
123 */
124 mbedtls_printf(" . Client: read public key...");
125 fflush(stdout);
126
127 ret = mbedtls_ecdh_read_public(&ctx_cli, srv_to_cli,
128 sizeof(srv_to_cli));
129 if (ret != 0) {
130 mbedtls_printf(" failed\n ! mbedtls_ecdh_read_public returned %d\n",
131 ret);
132 goto exit;
133 }
134
135 mbedtls_printf(" ok\n");
136
137 /*
138 * Calculate secrets
139 */
140 mbedtls_printf(" . Calculate secrets...");
141 fflush(stdout);
142
143 ret = mbedtls_ecdh_calc_secret(&ctx_cli, &cli_olen, secret_cli,
144 sizeof(secret_cli),
145 mbedtls_ctr_drbg_random, &ctr_drbg);
146 if (ret != 0) {
147 mbedtls_printf(" failed\n ! mbedtls_ecdh_calc_secret returned %d\n",
148 ret);
149 goto exit;
150 }
151
152 ret = mbedtls_ecdh_calc_secret(&ctx_srv, &srv_olen, secret_srv,
153 sizeof(secret_srv),
154 mbedtls_ctr_drbg_random, &ctr_drbg);
155 if (ret != 0) {
156 mbedtls_printf(" failed\n ! mbedtls_ecdh_calc_secret returned %d\n",
157 ret);
158 goto exit;
159 }
160
161 mbedtls_printf(" ok\n");
162
163 /*
164 * Verification: are the computed secrets equal?
165 */
166 mbedtls_printf(" . Check if both calculated secrets are equal...");
167 fflush(stdout);
168
169 ret = memcmp(secret_srv, secret_cli, srv_olen);
170 if (ret != 0 || (cli_olen != srv_olen)) {
171 mbedtls_printf(" failed\n ! Shared secrets not equal.\n");
172 goto exit;
173 }
174
175 mbedtls_printf(" ok\n");
176
177 exit_code = MBEDTLS_EXIT_SUCCESS;
178
179 exit:
180
181 mbedtls_ecdh_free(&ctx_srv);
182 mbedtls_ecdh_free(&ctx_cli);
183 mbedtls_ctr_drbg_free(&ctr_drbg);
184 mbedtls_entropy_free(&entropy);
185
186 mbedtls_exit(exit_code);
187 }
188 #endif /* MBEDTLS_ECDH_C && MBEDTLS_ECP_DP_CURVE25519_ENABLED &&
189 MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C */
190
