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 #include "mbedtls/build_info.h"
21
22 #include "mbedtls/platform.h"
23
24 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
25 defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
26 defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
27 defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
28 defined(MBEDTLS_SHA1_C)
29 #include "mbedtls/net_sockets.h"
30 #include "mbedtls/aes.h"
31 #include "mbedtls/dhm.h"
32 #include "mbedtls/rsa.h"
33 #include "mbedtls/sha1.h"
34 #include "mbedtls/entropy.h"
35 #include "mbedtls/ctr_drbg.h"
36
37 #include <stdio.h>
38 #include <string.h>
39 #endif
40
41 #define SERVER_PORT "11999"
42 #define PLAINTEXT "==Hello there!=="
43
44 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
45 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
46 !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) || \
47 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
48 !defined(MBEDTLS_SHA1_C)
main(void)49 int main( void )
50 {
51 mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
52 "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
53 "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
54 "MBEDTLS_CTR_DRBG_C not defined.\n");
55 mbedtls_exit( 0 );
56 }
57 #else
58
59
main(void)60 int main( void )
61 {
62 FILE *f;
63
64 int ret = 1;
65 int exit_code = MBEDTLS_EXIT_FAILURE;
66 size_t n, buflen;
67 mbedtls_net_context listen_fd, client_fd;
68
69 unsigned char buf[2048];
70 unsigned char hash[32];
71 unsigned char buf2[2];
72 const char *pers = "dh_server";
73
74 mbedtls_entropy_context entropy;
75 mbedtls_ctr_drbg_context ctr_drbg;
76 mbedtls_rsa_context rsa;
77 mbedtls_dhm_context dhm;
78 mbedtls_aes_context aes;
79
80 mbedtls_mpi N, P, Q, D, E;
81
82 mbedtls_net_init( &listen_fd );
83 mbedtls_net_init( &client_fd );
84 mbedtls_dhm_init( &dhm );
85 mbedtls_aes_init( &aes );
86 mbedtls_ctr_drbg_init( &ctr_drbg );
87
88 mbedtls_mpi_init( &N ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
89 mbedtls_mpi_init( &D ); mbedtls_mpi_init( &E );
90
91 /*
92 * 1. Setup the RNG
93 */
94 mbedtls_printf( "\n . Seeding the random number generator" );
95 fflush( stdout );
96
97 mbedtls_entropy_init( &entropy );
98 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
99 (const unsigned char *) pers,
100 strlen( pers ) ) ) != 0 )
101 {
102 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
103 goto exit;
104 }
105
106 /*
107 * 2a. Read the server's private RSA key
108 */
109 mbedtls_printf( "\n . Reading private key from rsa_priv.txt" );
110 fflush( stdout );
111
112 if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
113 {
114 mbedtls_printf( " failed\n ! Could not open rsa_priv.txt\n" \
115 " ! Please run rsa_genkey first\n\n" );
116 goto exit;
117 }
118
119 mbedtls_rsa_init( &rsa );
120
121 if( ( ret = mbedtls_mpi_read_file( &N , 16, f ) ) != 0 ||
122 ( ret = mbedtls_mpi_read_file( &E , 16, f ) ) != 0 ||
123 ( ret = mbedtls_mpi_read_file( &D , 16, f ) ) != 0 ||
124 ( ret = mbedtls_mpi_read_file( &P , 16, f ) ) != 0 ||
125 ( ret = mbedtls_mpi_read_file( &Q , 16, f ) ) != 0 )
126 {
127 mbedtls_printf( " failed\n ! mbedtls_mpi_read_file returned %d\n\n",
128 ret );
129 fclose( f );
130 goto exit;
131 }
132 fclose( f );
133
134 if( ( ret = mbedtls_rsa_import( &rsa, &N, &P, &Q, &D, &E ) ) != 0 )
135 {
136 mbedtls_printf( " failed\n ! mbedtls_rsa_import returned %d\n\n",
137 ret );
138 goto exit;
139 }
140
141 if( ( ret = mbedtls_rsa_complete( &rsa ) ) != 0 )
142 {
143 mbedtls_printf( " failed\n ! mbedtls_rsa_complete returned %d\n\n",
144 ret );
145 goto exit;
146 }
147
148 /*
149 * 2b. Get the DHM modulus and generator
150 */
151 mbedtls_printf( "\n . Reading DH parameters from dh_prime.txt" );
152 fflush( stdout );
153
154 if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
155 {
156 mbedtls_printf( " failed\n ! Could not open dh_prime.txt\n" \
157 " ! Please run dh_genprime first\n\n" );
158 goto exit;
159 }
160
161 if( mbedtls_mpi_read_file( &dhm.MBEDTLS_PRIVATE(P), 16, f ) != 0 ||
162 mbedtls_mpi_read_file( &dhm.MBEDTLS_PRIVATE(G), 16, f ) != 0 )
163 {
164 mbedtls_printf( " failed\n ! Invalid DH parameter file\n\n" );
165 fclose( f );
166 goto exit;
167 }
168
169 fclose( f );
170
171 /*
172 * 3. Wait for a client to connect
173 */
174 mbedtls_printf( "\n . Waiting for a remote connection" );
175 fflush( stdout );
176
177 if( ( ret = mbedtls_net_bind( &listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
178 {
179 mbedtls_printf( " failed\n ! mbedtls_net_bind returned %d\n\n", ret );
180 goto exit;
181 }
182
183 if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
184 NULL, 0, NULL ) ) != 0 )
185 {
186 mbedtls_printf( " failed\n ! mbedtls_net_accept returned %d\n\n", ret );
187 goto exit;
188 }
189
190 /*
191 * 4. Setup the DH parameters (P,G,Ys)
192 */
193 mbedtls_printf( "\n . Sending the server's DH parameters" );
194 fflush( stdout );
195
196 memset( buf, 0, sizeof( buf ) );
197
198 if( ( ret = mbedtls_dhm_make_params( &dhm, (int) mbedtls_mpi_size( &dhm.MBEDTLS_PRIVATE(P) ), buf, &n,
199 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
200 {
201 mbedtls_printf( " failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret );
202 goto exit;
203 }
204
205 /*
206 * 5. Sign the parameters and send them
207 */
208 if( ( ret = mbedtls_sha1( buf, n, hash ) ) != 0 )
209 {
210 mbedtls_printf( " failed\n ! mbedtls_sha1 returned %d\n\n", ret );
211 goto exit;
212 }
213
214 buf[n ] = (unsigned char)( rsa.MBEDTLS_PRIVATE(len) >> 8 );
215 buf[n + 1] = (unsigned char)( rsa.MBEDTLS_PRIVATE(len) );
216
217 if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_MD_SHA256,
218 32, hash, buf + n + 2 ) ) != 0 )
219 {
220 mbedtls_printf( " failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret );
221 goto exit;
222 }
223
224 buflen = n + 2 + rsa.MBEDTLS_PRIVATE(len);
225 buf2[0] = (unsigned char)( buflen >> 8 );
226 buf2[1] = (unsigned char)( buflen );
227
228 if( ( ret = mbedtls_net_send( &client_fd, buf2, 2 ) ) != 2 ||
229 ( ret = mbedtls_net_send( &client_fd, buf, buflen ) ) != (int) buflen )
230 {
231 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
232 goto exit;
233 }
234
235 /*
236 * 6. Get the client's public value: Yc = G ^ Xc mod P
237 */
238 mbedtls_printf( "\n . Receiving the client's public value" );
239 fflush( stdout );
240
241 memset( buf, 0, sizeof( buf ) );
242
243 n = mbedtls_dhm_get_len( &dhm );
244 if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
245 {
246 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
247 goto exit;
248 }
249
250 if( ( ret = mbedtls_dhm_read_public( &dhm, buf, n ) ) != 0 )
251 {
252 mbedtls_printf( " failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret );
253 goto exit;
254 }
255
256 /*
257 * 7. Derive the shared secret: K = Ys ^ Xc mod P
258 */
259 mbedtls_printf( "\n . Shared secret: " );
260 fflush( stdout );
261
262 if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
263 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
264 {
265 mbedtls_printf( " failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
266 goto exit;
267 }
268
269 for( n = 0; n < 16; n++ )
270 mbedtls_printf( "%02x", buf[n] );
271
272 /*
273 * 8. Setup the AES-256 encryption key
274 *
275 * This is an overly simplified example; best practice is
276 * to hash the shared secret with a random value to derive
277 * the keying material for the encryption/decryption keys
278 * and MACs.
279 */
280 mbedtls_printf( "...\n . Encrypting and sending the ciphertext" );
281 fflush( stdout );
282
283 ret = mbedtls_aes_setkey_enc( &aes, buf, 256 );
284 if( ret != 0 )
285 goto exit;
286 memcpy( buf, PLAINTEXT, 16 );
287 ret = mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_ENCRYPT, buf, buf );
288 if( ret != 0 )
289 goto exit;
290
291 if( ( ret = mbedtls_net_send( &client_fd, buf, 16 ) ) != 16 )
292 {
293 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
294 goto exit;
295 }
296
297 mbedtls_printf( "\n\n" );
298
299 exit_code = MBEDTLS_EXIT_SUCCESS;
300
301 exit:
302
303 mbedtls_mpi_free( &N ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
304 mbedtls_mpi_free( &D ); mbedtls_mpi_free( &E );
305
306 mbedtls_net_free( &client_fd );
307 mbedtls_net_free( &listen_fd );
308
309 mbedtls_aes_free( &aes );
310 mbedtls_rsa_free( &rsa );
311 mbedtls_dhm_free( &dhm );
312 mbedtls_ctr_drbg_free( &ctr_drbg );
313 mbedtls_entropy_free( &entropy );
314
315 mbedtls_exit( exit_code );
316 }
317 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
318 MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
319 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
320