1 /*
2 * Example ECDHE with Curve25519 program
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21
22 #if !defined(MBEDTLS_CONFIG_FILE)
23 #include "mbedtls/config.h"
24 #else
25 #include MBEDTLS_CONFIG_FILE
26 #endif
27
28 #if defined(MBEDTLS_PLATFORM_C)
29 #include "mbedtls/platform.h"
30 #else
31 #include <stdio.h>
32 #define mbedtls_printf printf
33 #endif
34
35 #if !defined(MBEDTLS_ECDH_C) || \
36 !defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED) || \
37 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C)
main(void)38 int main( void )
39 {
40 mbedtls_printf( "MBEDTLS_ECDH_C and/or "
41 "MBEDTLS_ECP_DP_CURVE25519_ENABLED and/or "
42 "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C "
43 "not defined\n" );
44 return( 0 );
45 }
46 #else
47
48 #include "mbedtls/entropy.h"
49 #include "mbedtls/ctr_drbg.h"
50 #include "mbedtls/ecdh.h"
51
main(int argc,char * argv[])52 int main( int argc, char *argv[] )
53 {
54 int ret;
55 mbedtls_ecdh_context ctx_cli, ctx_srv;
56 mbedtls_entropy_context entropy;
57 mbedtls_ctr_drbg_context ctr_drbg;
58 unsigned char cli_to_srv[32], srv_to_cli[32];
59 const char pers[] = "ecdh";
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( " . Seeding 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, &entropy,
75 (const unsigned char *) pers,
76 sizeof pers ) ) != 0 )
77 {
78 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
79 goto exit;
80 }
81
82 mbedtls_printf( " ok\n" );
83
84 /*
85 * Client: inialize context and generate keypair
86 */
87 mbedtls_printf( " . Setting up client context..." );
88 fflush( stdout );
89
90 ret = mbedtls_ecp_group_load( &ctx_cli.grp, MBEDTLS_ECP_DP_CURVE25519 );
91 if( ret != 0 )
92 {
93 mbedtls_printf( " failed\n ! mbedtls_ecp_group_load returned %d\n", ret );
94 goto exit;
95 }
96
97 ret = mbedtls_ecdh_gen_public( &ctx_cli.grp, &ctx_cli.d, &ctx_cli.Q,
98 mbedtls_ctr_drbg_random, &ctr_drbg );
99 if( ret != 0 )
100 {
101 mbedtls_printf( " failed\n ! mbedtls_ecdh_gen_public returned %d\n", ret );
102 goto exit;
103 }
104
105 ret = mbedtls_mpi_write_binary( &ctx_cli.Q.X, cli_to_srv, 32 );
106 if( ret != 0 )
107 {
108 mbedtls_printf( " failed\n ! mbedtls_mpi_write_binary returned %d\n", ret );
109 goto exit;
110 }
111
112 mbedtls_printf( " ok\n" );
113
114 /*
115 * Server: initialize context and generate keypair
116 */
117 mbedtls_printf( " . Setting up server context..." );
118 fflush( stdout );
119
120 ret = mbedtls_ecp_group_load( &ctx_srv.grp, MBEDTLS_ECP_DP_CURVE25519 );
121 if( ret != 0 )
122 {
123 mbedtls_printf( " failed\n ! mbedtls_ecp_group_load returned %d\n", ret );
124 goto exit;
125 }
126
127 ret = mbedtls_ecdh_gen_public( &ctx_srv.grp, &ctx_srv.d, &ctx_srv.Q,
128 mbedtls_ctr_drbg_random, &ctr_drbg );
129 if( ret != 0 )
130 {
131 mbedtls_printf( " failed\n ! mbedtls_ecdh_gen_public returned %d\n", ret );
132 goto exit;
133 }
134
135 ret = mbedtls_mpi_write_binary( &ctx_srv.Q.X, srv_to_cli, 32 );
136 if( ret != 0 )
137 {
138 mbedtls_printf( " failed\n ! mbedtls_mpi_write_binary returned %d\n", ret );
139 goto exit;
140 }
141
142 mbedtls_printf( " ok\n" );
143
144 /*
145 * Server: read peer's key and generate shared secret
146 */
147 mbedtls_printf( " . Server reading client key and computing secret..." );
148 fflush( stdout );
149
150 ret = mbedtls_mpi_lset( &ctx_srv.Qp.Z, 1 );
151 if( ret != 0 )
152 {
153 mbedtls_printf( " failed\n ! mbedtls_mpi_lset returned %d\n", ret );
154 goto exit;
155 }
156
157 ret = mbedtls_mpi_read_binary( &ctx_srv.Qp.X, cli_to_srv, 32 );
158 if( ret != 0 )
159 {
160 mbedtls_printf( " failed\n ! mbedtls_mpi_read_binary returned %d\n", ret );
161 goto exit;
162 }
163
164 ret = mbedtls_ecdh_compute_shared( &ctx_srv.grp, &ctx_srv.z,
165 &ctx_srv.Qp, &ctx_srv.d,
166 mbedtls_ctr_drbg_random, &ctr_drbg );
167 if( ret != 0 )
168 {
169 mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret );
170 goto exit;
171 }
172
173 mbedtls_printf( " ok\n" );
174
175 /*
176 * Client: read peer's key and generate shared secret
177 */
178 mbedtls_printf( " . Client reading server key and computing secret..." );
179 fflush( stdout );
180
181 ret = mbedtls_mpi_lset( &ctx_cli.Qp.Z, 1 );
182 if( ret != 0 )
183 {
184 mbedtls_printf( " failed\n ! mbedtls_mpi_lset returned %d\n", ret );
185 goto exit;
186 }
187
188 ret = mbedtls_mpi_read_binary( &ctx_cli.Qp.X, srv_to_cli, 32 );
189 if( ret != 0 )
190 {
191 mbedtls_printf( " failed\n ! mbedtls_mpi_read_binary returned %d\n", ret );
192 goto exit;
193 }
194
195 ret = mbedtls_ecdh_compute_shared( &ctx_cli.grp, &ctx_cli.z,
196 &ctx_cli.Qp, &ctx_cli.d,
197 mbedtls_ctr_drbg_random, &ctr_drbg );
198 if( ret != 0 )
199 {
200 mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret );
201 goto exit;
202 }
203
204 mbedtls_printf( " ok\n" );
205
206 /*
207 * Verification: are the computed secret equal?
208 */
209 mbedtls_printf( " . Checking if both computed secrets are equal..." );
210 fflush( stdout );
211
212 ret = mbedtls_mpi_cmp_mpi( &ctx_cli.z, &ctx_srv.z );
213 if( ret != 0 )
214 {
215 mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret );
216 goto exit;
217 }
218
219 mbedtls_printf( " ok\n" );
220
221
222 exit:
223
224 #if defined(_WIN32)
225 mbedtls_printf( " + Press Enter to exit this program.\n" );
226 fflush( stdout ); getchar();
227 #endif
228
229 mbedtls_ecdh_free( &ctx_srv );
230 mbedtls_ecdh_free( &ctx_cli );
231 mbedtls_ctr_drbg_free( &ctr_drbg );
232 mbedtls_entropy_free( &entropy );
233
234 return( ret != 0 );
235 }
236 #endif /* MBEDTLS_ECDH_C && MBEDTLS_ECP_DP_CURVE25519_ENABLED &&
237 MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C */
238
