1 /*
2 * Diffie-Hellman-Merkle key exchange (server side)
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 #if !defined(MBEDTLS_CONFIG_FILE)
21 #include "mbedtls/config.h"
22 #else
23 #include MBEDTLS_CONFIG_FILE
24 #endif
25
26 #if defined(MBEDTLS_PLATFORM_C)
27 #include "mbedtls/platform.h"
28 #else
29 #include <stdio.h>
30 #include <stdlib.h>
31 #define mbedtls_printf printf
32 #define mbedtls_time_t time_t
33 #define mbedtls_exit exit
34 #define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
35 #define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
36 #endif /* MBEDTLS_PLATFORM_C */
37
38 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
39 defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
40 defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
41 defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
42 defined(MBEDTLS_SHA1_C)
43 #include "mbedtls/net_sockets.h"
44 #include "mbedtls/aes.h"
45 #include "mbedtls/dhm.h"
46 #include "mbedtls/rsa.h"
47 #include "mbedtls/sha1.h"
48 #include "mbedtls/entropy.h"
49 #include "mbedtls/ctr_drbg.h"
50
51 #include <stdio.h>
52 #include <string.h>
53 #endif
54
55 #define SERVER_PORT "11999"
56 #define PLAINTEXT "==Hello there!=="
57
58 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
59 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
60 !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) || \
61 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
62 !defined(MBEDTLS_SHA1_C)
main(void)63 int main( void )
64 {
65 mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
66 "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
67 "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
68 "MBEDTLS_CTR_DRBG_C not defined.\n");
69 mbedtls_exit( 0 );
70 }
71 #else
72
73
main(void)74 int main( void )
75 {
76 FILE *f;
77
78 int ret = 1;
79 int exit_code = MBEDTLS_EXIT_FAILURE;
80 size_t n, buflen;
81 mbedtls_net_context listen_fd, client_fd;
82
83 unsigned char buf[2048];
84 unsigned char hash[32];
85 unsigned char buf2[2];
86 const char *pers = "dh_server";
87
88 mbedtls_entropy_context entropy;
89 mbedtls_ctr_drbg_context ctr_drbg;
90 mbedtls_rsa_context rsa;
91 mbedtls_dhm_context dhm;
92 mbedtls_aes_context aes;
93
94 mbedtls_mpi N, P, Q, D, E;
95
96 mbedtls_net_init( &listen_fd );
97 mbedtls_net_init( &client_fd );
98 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
99 mbedtls_dhm_init( &dhm );
100 mbedtls_aes_init( &aes );
101 mbedtls_ctr_drbg_init( &ctr_drbg );
102
103 mbedtls_mpi_init( &N ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
104 mbedtls_mpi_init( &D ); mbedtls_mpi_init( &E );
105
106 /*
107 * 1. Setup the RNG
108 */
109 mbedtls_printf( "\n . Seeding the random number generator" );
110 fflush( stdout );
111
112 mbedtls_entropy_init( &entropy );
113 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
114 (const unsigned char *) pers,
115 strlen( pers ) ) ) != 0 )
116 {
117 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
118 goto exit;
119 }
120
121 /*
122 * 2a. Read the server's private RSA key
123 */
124 mbedtls_printf( "\n . Reading private key from rsa_priv.txt" );
125 fflush( stdout );
126
127 if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
128 {
129 mbedtls_printf( " failed\n ! Could not open rsa_priv.txt\n" \
130 " ! Please run rsa_genkey first\n\n" );
131 goto exit;
132 }
133
134 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
135
136 if( ( ret = mbedtls_mpi_read_file( &N , 16, f ) ) != 0 ||
137 ( ret = mbedtls_mpi_read_file( &E , 16, f ) ) != 0 ||
138 ( ret = mbedtls_mpi_read_file( &D , 16, f ) ) != 0 ||
139 ( ret = mbedtls_mpi_read_file( &P , 16, f ) ) != 0 ||
140 ( ret = mbedtls_mpi_read_file( &Q , 16, f ) ) != 0 )
141 {
142 mbedtls_printf( " failed\n ! mbedtls_mpi_read_file returned %d\n\n",
143 ret );
144 fclose( f );
145 goto exit;
146 }
147 fclose( f );
148
149 if( ( ret = mbedtls_rsa_import( &rsa, &N, &P, &Q, &D, &E ) ) != 0 )
150 {
151 mbedtls_printf( " failed\n ! mbedtls_rsa_import returned %d\n\n",
152 ret );
153 goto exit;
154 }
155
156 if( ( ret = mbedtls_rsa_complete( &rsa ) ) != 0 )
157 {
158 mbedtls_printf( " failed\n ! mbedtls_rsa_complete returned %d\n\n",
159 ret );
160 goto exit;
161 }
162
163 /*
164 * 2b. Get the DHM modulus and generator
165 */
166 mbedtls_printf( "\n . Reading DH parameters from dh_prime.txt" );
167 fflush( stdout );
168
169 if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
170 {
171 mbedtls_printf( " failed\n ! Could not open dh_prime.txt\n" \
172 " ! Please run dh_genprime first\n\n" );
173 goto exit;
174 }
175
176 if( mbedtls_mpi_read_file( &dhm.P, 16, f ) != 0 ||
177 mbedtls_mpi_read_file( &dhm.G, 16, f ) != 0 )
178 {
179 mbedtls_printf( " failed\n ! Invalid DH parameter file\n\n" );
180 fclose( f );
181 goto exit;
182 }
183
184 fclose( f );
185
186 /*
187 * 3. Wait for a client to connect
188 */
189 mbedtls_printf( "\n . Waiting for a remote connection" );
190 fflush( stdout );
191
192 if( ( ret = mbedtls_net_bind( &listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
193 {
194 mbedtls_printf( " failed\n ! mbedtls_net_bind returned %d\n\n", ret );
195 goto exit;
196 }
197
198 if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
199 NULL, 0, NULL ) ) != 0 )
200 {
201 mbedtls_printf( " failed\n ! mbedtls_net_accept returned %d\n\n", ret );
202 goto exit;
203 }
204
205 /*
206 * 4. Setup the DH parameters (P,G,Ys)
207 */
208 mbedtls_printf( "\n . Sending the server's DH parameters" );
209 fflush( stdout );
210
211 memset( buf, 0, sizeof( buf ) );
212
213 if( ( ret = mbedtls_dhm_make_params( &dhm, (int) mbedtls_mpi_size( &dhm.P ), buf, &n,
214 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
215 {
216 mbedtls_printf( " failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret );
217 goto exit;
218 }
219
220 /*
221 * 5. Sign the parameters and send them
222 */
223 if( ( ret = mbedtls_sha1_ret( buf, n, hash ) ) != 0 )
224 {
225 mbedtls_printf( " failed\n ! mbedtls_sha1_ret returned %d\n\n", ret );
226 goto exit;
227 }
228
229 buf[n ] = (unsigned char)( rsa.len >> 8 );
230 buf[n + 1] = (unsigned char)( rsa.len );
231
232 if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE, MBEDTLS_MD_SHA256,
233 0, hash, buf + n + 2 ) ) != 0 )
234 {
235 mbedtls_printf( " failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret );
236 goto exit;
237 }
238
239 buflen = n + 2 + rsa.len;
240 buf2[0] = (unsigned char)( buflen >> 8 );
241 buf2[1] = (unsigned char)( buflen );
242
243 if( ( ret = mbedtls_net_send( &client_fd, buf2, 2 ) ) != 2 ||
244 ( ret = mbedtls_net_send( &client_fd, buf, buflen ) ) != (int) buflen )
245 {
246 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
247 goto exit;
248 }
249
250 /*
251 * 6. Get the client's public value: Yc = G ^ Xc mod P
252 */
253 mbedtls_printf( "\n . Receiving the client's public value" );
254 fflush( stdout );
255
256 memset( buf, 0, sizeof( buf ) );
257
258 n = dhm.len;
259 if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
260 {
261 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
262 goto exit;
263 }
264
265 if( ( ret = mbedtls_dhm_read_public( &dhm, buf, dhm.len ) ) != 0 )
266 {
267 mbedtls_printf( " failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret );
268 goto exit;
269 }
270
271 /*
272 * 7. Derive the shared secret: K = Ys ^ Xc mod P
273 */
274 mbedtls_printf( "\n . Shared secret: " );
275 fflush( stdout );
276
277 if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
278 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
279 {
280 mbedtls_printf( " failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
281 goto exit;
282 }
283
284 for( n = 0; n < 16; n++ )
285 mbedtls_printf( "%02x", buf[n] );
286
287 /*
288 * 8. Setup the AES-256 encryption key
289 *
290 * This is an overly simplified example; best practice is
291 * to hash the shared secret with a random value to derive
292 * the keying material for the encryption/decryption keys
293 * and MACs.
294 */
295 mbedtls_printf( "...\n . Encrypting and sending the ciphertext" );
296 fflush( stdout );
297
298 ret = mbedtls_aes_setkey_enc( &aes, buf, 256 );
299 if( ret != 0 )
300 goto exit;
301 memcpy( buf, PLAINTEXT, 16 );
302 ret = mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_ENCRYPT, buf, buf );
303 if( ret != 0 )
304 goto exit;
305
306 if( ( ret = mbedtls_net_send( &client_fd, buf, 16 ) ) != 16 )
307 {
308 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
309 goto exit;
310 }
311
312 mbedtls_printf( "\n\n" );
313
314 exit_code = MBEDTLS_EXIT_SUCCESS;
315
316 exit:
317
318 mbedtls_mpi_free( &N ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
319 mbedtls_mpi_free( &D ); mbedtls_mpi_free( &E );
320
321 mbedtls_net_free( &client_fd );
322 mbedtls_net_free( &listen_fd );
323
324 mbedtls_aes_free( &aes );
325 mbedtls_rsa_free( &rsa );
326 mbedtls_dhm_free( &dhm );
327 mbedtls_ctr_drbg_free( &ctr_drbg );
328 mbedtls_entropy_free( &entropy );
329
330 #if defined(_WIN32)
331 mbedtls_printf( " + Press Enter to exit this program.\n" );
332 fflush( stdout ); getchar();
333 #endif
334
335 mbedtls_exit( exit_code );
336 }
337 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
338 MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
339 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
340
