1 /*
2 * Diffie-Hellman-Merkle key exchange (client 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_NAME "localhost"
83 #define SERVER_PORT "11999"
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 server_fd;
109
110 unsigned char *p, *end;
111 unsigned char buf[2048];
112 unsigned char hash[32];
113 const char *pers = "dh_client";
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_net_init( &server_fd );
122 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
123 mbedtls_dhm_init( &dhm );
124 mbedtls_aes_init( &aes );
125 mbedtls_ctr_drbg_init( &ctr_drbg );
126
127 /*
128 * 1. Setup the RNG
129 */
130 mbedtls_printf( "\n . Seeding the random number generator" );
131 fflush( stdout );
132
133 mbedtls_entropy_init( &entropy );
134 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
135 (const unsigned char *) pers,
136 strlen( pers ) ) ) != 0 )
137 {
138 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
139 goto exit;
140 }
141
142 /*
143 * 2. Read the server's public RSA key
144 */
145 mbedtls_printf( "\n . Reading public key from rsa_pub.txt" );
146 fflush( stdout );
147
148 if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL )
149 {
150 mbedtls_printf( " failed\n ! Could not open rsa_pub.txt\n" \
151 " ! Please run rsa_genkey first\n\n" );
152 goto exit;
153 }
154
155 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
156
157 if( ( ret = mbedtls_mpi_read_file( &rsa.N, 16, f ) ) != 0 ||
158 ( ret = mbedtls_mpi_read_file( &rsa.E, 16, f ) ) != 0 )
159 {
160 mbedtls_printf( " failed\n ! mbedtls_mpi_read_file returned %d\n\n", ret );
161 fclose( f );
162 goto exit;
163 }
164
165 rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
166
167 fclose( f );
168
169 /*
170 * 3. Initiate the connection
171 */
172 mbedtls_printf( "\n . Connecting to tcp/%s/%s", SERVER_NAME,
173 SERVER_PORT );
174 fflush( stdout );
175
176 if( ( ret = mbedtls_net_connect( &server_fd, SERVER_NAME,
177 SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
178 {
179 mbedtls_printf( " failed\n ! mbedtls_net_connect returned %d\n\n", ret );
180 goto exit;
181 }
182
183 /*
184 * 4a. First get the buffer length
185 */
186 mbedtls_printf( "\n . Receiving the server's DH parameters" );
187 fflush( stdout );
188
189 memset( buf, 0, sizeof( buf ) );
190
191 if( ( ret = mbedtls_net_recv( &server_fd, buf, 2 ) ) != 2 )
192 {
193 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
194 goto exit;
195 }
196
197 n = buflen = ( buf[0] << 8 ) | buf[1];
198 if( buflen < 1 || buflen > sizeof( buf ) )
199 {
200 mbedtls_printf( " failed\n ! Got an invalid buffer length\n\n" );
201 goto exit;
202 }
203
204 /*
205 * 4b. Get the DHM parameters: P, G and Ys = G^Xs mod P
206 */
207 memset( buf, 0, sizeof( buf ) );
208
209 if( ( ret = mbedtls_net_recv( &server_fd, buf, n ) ) != (int) n )
210 {
211 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
212 goto exit;
213 }
214
215 p = buf, end = buf + buflen;
216
217 if( ( ret = mbedtls_dhm_read_params( &dhm, &p, end ) ) != 0 )
218 {
219 mbedtls_printf( " failed\n ! mbedtls_dhm_read_params returned %d\n\n", ret );
220 goto exit;
221 }
222
223 if( dhm.len < 64 || dhm.len > 512 )
224 {
225 mbedtls_printf( " failed\n ! Invalid DHM modulus size\n\n" );
226 goto exit;
227 }
228
229 /*
230 * 5. Check that the server's RSA signature matches
231 * the SHA-256 hash of (P,G,Ys)
232 */
233 mbedtls_printf( "\n . Verifying the server's RSA signature" );
234 fflush( stdout );
235
236 p += 2;
237
238 if( ( n = (size_t) ( end - p ) ) != rsa.len )
239 {
240 mbedtls_printf( " failed\n ! Invalid RSA signature size\n\n" );
241 goto exit;
242 }
243
244 if( ( ret = mbedtls_sha1_ret( buf, (int)( p - 2 - buf ), hash ) ) != 0 )
245 {
246 mbedtls_printf( " failed\n ! mbedtls_sha1_ret returned %d\n\n", ret );
247 goto exit;
248 }
249
250 if( ( ret = mbedtls_rsa_pkcs1_verify( &rsa, NULL, NULL, MBEDTLS_RSA_PUBLIC,
251 MBEDTLS_MD_SHA256, 0, hash, p ) ) != 0 )
252 {
253 mbedtls_printf( " failed\n ! mbedtls_rsa_pkcs1_verify returned %d\n\n", ret );
254 goto exit;
255 }
256
257 /*
258 * 6. Send our public value: Yc = G ^ Xc mod P
259 */
260 mbedtls_printf( "\n . Sending own public value to server" );
261 fflush( stdout );
262
263 n = dhm.len;
264 if( ( ret = mbedtls_dhm_make_public( &dhm, (int) dhm.len, buf, n,
265 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
266 {
267 mbedtls_printf( " failed\n ! mbedtls_dhm_make_public returned %d\n\n", ret );
268 goto exit;
269 }
270
271 if( ( ret = mbedtls_net_send( &server_fd, buf, n ) ) != (int) n )
272 {
273 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
274 goto exit;
275 }
276
277 /*
278 * 7. Derive the shared secret: K = Ys ^ Xc mod P
279 */
280 mbedtls_printf( "\n . Shared secret: " );
281 fflush( stdout );
282
283 if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
284 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
285 {
286 mbedtls_printf( " failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
287 goto exit;
288 }
289
290 for( n = 0; n < 16; n++ )
291 mbedtls_printf( "%02x", buf[n] );
292
293 /*
294 * 8. Setup the AES-256 decryption key
295 *
296 * This is an overly simplified example; best practice is
297 * to hash the shared secret with a random value to derive
298 * the keying material for the encryption/decryption keys,
299 * IVs and MACs.
300 */
301 mbedtls_printf( "...\n . Receiving and decrypting the ciphertext" );
302 fflush( stdout );
303
304 mbedtls_aes_setkey_dec( &aes, buf, 256 );
305
306 memset( buf, 0, sizeof( buf ) );
307
308 if( ( ret = mbedtls_net_recv( &server_fd, buf, 16 ) ) != 16 )
309 {
310 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
311 goto exit;
312 }
313
314 mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_DECRYPT, buf, buf );
315 buf[16] = '\0';
316 mbedtls_printf( "\n . Plaintext is \"%s\"\n\n", (char *) buf );
317
318 exit_code = MBEDTLS_EXIT_SUCCESS;
319
320 exit:
321
322 mbedtls_net_free( &server_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