1 /*
2 * Diffie-Hellman-Merkle key exchange (server side)
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 *
7 * This file is provided under the Apache License 2.0, or the
8 * GNU General Public License v2.0 or later.
9 *
10 * **********
11 * Apache License 2.0:
12 *
13 * Licensed under the Apache License, Version 2.0 (the "License"); you may
14 * not use this file except in compliance with the License.
15 * You may obtain a copy of the License at
16 *
17 * http://www.apache.org/licenses/LICENSE-2.0
18 *
19 * Unless required by applicable law or agreed to in writing, software
20 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
21 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
22 * See the License for the specific language governing permissions and
23 * limitations under the License.
24 *
25 * **********
26 *
27 * **********
28 * GNU General Public License v2.0 or later:
29 *
30 * This program is free software; you can redistribute it and/or modify
31 * it under the terms of the GNU General Public License as published by
32 * the Free Software Foundation; either version 2 of the License, or
33 * (at your option) any later version.
34 *
35 * This program is distributed in the hope that it will be useful,
36 * but WITHOUT ANY WARRANTY; without even the implied warranty of
37 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
38 * GNU General Public License for more details.
39 *
40 * You should have received a copy of the GNU General Public License along
41 * with this program; if not, write to the Free Software Foundation, Inc.,
42 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
43 *
44 * **********
45 */
46
47 #if !defined(MBEDTLS_CONFIG_FILE)
48 #include "mbedtls/config.h"
49 #else
50 #include MBEDTLS_CONFIG_FILE
51 #endif
52
53 #if defined(MBEDTLS_PLATFORM_C)
54 #include "mbedtls/platform.h"
55 #else
56 #include <stdio.h>
57 #include <stdlib.h>
58 #define mbedtls_printf printf
59 #define mbedtls_time_t time_t
60 #define mbedtls_exit exit
61 #define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
62 #define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
63 #endif /* MBEDTLS_PLATFORM_C */
64
65 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
66 defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
67 defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
68 defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
69 defined(MBEDTLS_SHA1_C)
70 #include "mbedtls/net_sockets.h"
71 #include "mbedtls/aes.h"
72 #include "mbedtls/dhm.h"
73 #include "mbedtls/rsa.h"
74 #include "mbedtls/sha1.h"
75 #include "mbedtls/entropy.h"
76 #include "mbedtls/ctr_drbg.h"
77
78 #include <stdio.h>
79 #include <string.h>
80 #endif
81
82 #define SERVER_PORT "11999"
83 #define PLAINTEXT "==Hello there!=="
84
85 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
86 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
87 !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) || \
88 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
89 !defined(MBEDTLS_SHA1_C)
main(void)90 int main( void )
91 {
92 mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
93 "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
94 "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
95 "MBEDTLS_CTR_DRBG_C not defined.\n");
96 mbedtls_exit( 0 );
97 }
98 #else
99
100
main(void)101 int main( void )
102 {
103 FILE *f;
104
105 int ret = 1;
106 int exit_code = MBEDTLS_EXIT_FAILURE;
107 size_t n, buflen;
108 mbedtls_net_context listen_fd, client_fd;
109
110 unsigned char buf[2048];
111 unsigned char hash[32];
112 unsigned char buf2[2];
113 const char *pers = "dh_server";
114
115 mbedtls_entropy_context entropy;
116 mbedtls_ctr_drbg_context ctr_drbg;
117 mbedtls_rsa_context rsa;
118 mbedtls_dhm_context dhm;
119 mbedtls_aes_context aes;
120
121 mbedtls_mpi N, P, Q, D, E;
122
123 mbedtls_net_init( &listen_fd );
124 mbedtls_net_init( &client_fd );
125 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
126 mbedtls_dhm_init( &dhm );
127 mbedtls_aes_init( &aes );
128 mbedtls_ctr_drbg_init( &ctr_drbg );
129
130 mbedtls_mpi_init( &N ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
131 mbedtls_mpi_init( &D ); mbedtls_mpi_init( &E );
132
133 /*
134 * 1. Setup the RNG
135 */
136 mbedtls_printf( "\n . Seeding the random number generator" );
137 fflush( stdout );
138
139 mbedtls_entropy_init( &entropy );
140 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
141 (const unsigned char *) pers,
142 strlen( pers ) ) ) != 0 )
143 {
144 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
145 goto exit;
146 }
147
148 /*
149 * 2a. Read the server's private RSA key
150 */
151 mbedtls_printf( "\n . Reading private key from rsa_priv.txt" );
152 fflush( stdout );
153
154 if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
155 {
156 mbedtls_printf( " failed\n ! Could not open rsa_priv.txt\n" \
157 " ! Please run rsa_genkey first\n\n" );
158 goto exit;
159 }
160
161 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
162
163 if( ( ret = mbedtls_mpi_read_file( &N , 16, f ) ) != 0 ||
164 ( ret = mbedtls_mpi_read_file( &E , 16, f ) ) != 0 ||
165 ( ret = mbedtls_mpi_read_file( &D , 16, f ) ) != 0 ||
166 ( ret = mbedtls_mpi_read_file( &P , 16, f ) ) != 0 ||
167 ( ret = mbedtls_mpi_read_file( &Q , 16, f ) ) != 0 )
168 {
169 mbedtls_printf( " failed\n ! mbedtls_mpi_read_file returned %d\n\n",
170 ret );
171 fclose( f );
172 goto exit;
173 }
174 fclose( f );
175
176 if( ( ret = mbedtls_rsa_import( &rsa, &N, &P, &Q, &D, &E ) ) != 0 )
177 {
178 mbedtls_printf( " failed\n ! mbedtls_rsa_import returned %d\n\n",
179 ret );
180 goto exit;
181 }
182
183 if( ( ret = mbedtls_rsa_complete( &rsa ) ) != 0 )
184 {
185 mbedtls_printf( " failed\n ! mbedtls_rsa_complete returned %d\n\n",
186 ret );
187 goto exit;
188 }
189
190 /*
191 * 2b. Get the DHM modulus and generator
192 */
193 mbedtls_printf( "\n . Reading DH parameters from dh_prime.txt" );
194 fflush( stdout );
195
196 if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
197 {
198 mbedtls_printf( " failed\n ! Could not open dh_prime.txt\n" \
199 " ! Please run dh_genprime first\n\n" );
200 goto exit;
201 }
202
203 if( mbedtls_mpi_read_file( &dhm.P, 16, f ) != 0 ||
204 mbedtls_mpi_read_file( &dhm.G, 16, f ) != 0 )
205 {
206 mbedtls_printf( " failed\n ! Invalid DH parameter file\n\n" );
207 fclose( f );
208 goto exit;
209 }
210
211 fclose( f );
212
213 /*
214 * 3. Wait for a client to connect
215 */
216 mbedtls_printf( "\n . Waiting for a remote connection" );
217 fflush( stdout );
218
219 if( ( ret = mbedtls_net_bind( &listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
220 {
221 mbedtls_printf( " failed\n ! mbedtls_net_bind returned %d\n\n", ret );
222 goto exit;
223 }
224
225 if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
226 NULL, 0, NULL ) ) != 0 )
227 {
228 mbedtls_printf( " failed\n ! mbedtls_net_accept returned %d\n\n", ret );
229 goto exit;
230 }
231
232 /*
233 * 4. Setup the DH parameters (P,G,Ys)
234 */
235 mbedtls_printf( "\n . Sending the server's DH parameters" );
236 fflush( stdout );
237
238 memset( buf, 0, sizeof( buf ) );
239
240 if( ( ret = mbedtls_dhm_make_params( &dhm, (int) mbedtls_mpi_size( &dhm.P ), buf, &n,
241 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
242 {
243 mbedtls_printf( " failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret );
244 goto exit;
245 }
246
247 /*
248 * 5. Sign the parameters and send them
249 */
250 if( ( ret = mbedtls_sha1_ret( buf, n, hash ) ) != 0 )
251 {
252 mbedtls_printf( " failed\n ! mbedtls_sha1_ret returned %d\n\n", ret );
253 goto exit;
254 }
255
256 buf[n ] = (unsigned char)( rsa.len >> 8 );
257 buf[n + 1] = (unsigned char)( rsa.len );
258
259 if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE, MBEDTLS_MD_SHA256,
260 0, hash, buf + n + 2 ) ) != 0 )
261 {
262 mbedtls_printf( " failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret );
263 goto exit;
264 }
265
266 buflen = n + 2 + rsa.len;
267 buf2[0] = (unsigned char)( buflen >> 8 );
268 buf2[1] = (unsigned char)( buflen );
269
270 if( ( ret = mbedtls_net_send( &client_fd, buf2, 2 ) ) != 2 ||
271 ( ret = mbedtls_net_send( &client_fd, buf, buflen ) ) != (int) buflen )
272 {
273 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
274 goto exit;
275 }
276
277 /*
278 * 6. Get the client's public value: Yc = G ^ Xc mod P
279 */
280 mbedtls_printf( "\n . Receiving the client's public value" );
281 fflush( stdout );
282
283 memset( buf, 0, sizeof( buf ) );
284
285 n = dhm.len;
286 if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
287 {
288 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
289 goto exit;
290 }
291
292 if( ( ret = mbedtls_dhm_read_public( &dhm, buf, dhm.len ) ) != 0 )
293 {
294 mbedtls_printf( " failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret );
295 goto exit;
296 }
297
298 /*
299 * 7. Derive the shared secret: K = Ys ^ Xc mod P
300 */
301 mbedtls_printf( "\n . Shared secret: " );
302 fflush( stdout );
303
304 if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
305 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
306 {
307 mbedtls_printf( " failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
308 goto exit;
309 }
310
311 for( n = 0; n < 16; n++ )
312 mbedtls_printf( "%02x", buf[n] );
313
314 /*
315 * 8. Setup the AES-256 encryption key
316 *
317 * This is an overly simplified example; best practice is
318 * to hash the shared secret with a random value to derive
319 * the keying material for the encryption/decryption keys
320 * and MACs.
321 */
322 mbedtls_printf( "...\n . Encrypting and sending the ciphertext" );
323 fflush( stdout );
324
325 mbedtls_aes_setkey_enc( &aes, buf, 256 );
326 memcpy( buf, PLAINTEXT, 16 );
327 mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_ENCRYPT, buf, buf );
328
329 if( ( ret = mbedtls_net_send( &client_fd, buf, 16 ) ) != 16 )
330 {
331 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
332 goto exit;
333 }
334
335 mbedtls_printf( "\n\n" );
336
337 exit_code = MBEDTLS_EXIT_SUCCESS;
338
339 exit:
340
341 mbedtls_mpi_free( &N ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
342 mbedtls_mpi_free( &D ); mbedtls_mpi_free( &E );
343
344 mbedtls_net_free( &client_fd );
345 mbedtls_net_free( &listen_fd );
346
347 mbedtls_aes_free( &aes );
348 mbedtls_rsa_free( &rsa );
349 mbedtls_dhm_free( &dhm );
350 mbedtls_ctr_drbg_free( &ctr_drbg );
351 mbedtls_entropy_free( &entropy );
352
353 #if defined(_WIN32)
354 mbedtls_printf( " + Press Enter to exit this program.\n" );
355 fflush( stdout ); getchar();
356 #endif
357
358 mbedtls_exit( exit_code );
359 }
360 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
361 MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
362 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
363