1 /*
2 * Diffie-Hellman-Merkle key exchange (client 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_NAME "localhost"
56 #define SERVER_PORT "11999"
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 server_fd;
82
83 unsigned char *p, *end;
84 unsigned char buf[2048];
85 unsigned char hash[32];
86 const char *pers = "dh_client";
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_net_init( &server_fd );
95 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
96 mbedtls_dhm_init( &dhm );
97 mbedtls_aes_init( &aes );
98 mbedtls_ctr_drbg_init( &ctr_drbg );
99
100 /*
101 * 1. Setup the RNG
102 */
103 mbedtls_printf( "\n . Seeding the random number generator" );
104 fflush( stdout );
105
106 mbedtls_entropy_init( &entropy );
107 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
108 (const unsigned char *) pers,
109 strlen( pers ) ) ) != 0 )
110 {
111 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
112 goto exit;
113 }
114
115 /*
116 * 2. Read the server's public RSA key
117 */
118 mbedtls_printf( "\n . Reading public key from rsa_pub.txt" );
119 fflush( stdout );
120
121 if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL )
122 {
123 mbedtls_printf( " failed\n ! Could not open rsa_pub.txt\n" \
124 " ! Please run rsa_genkey first\n\n" );
125 goto exit;
126 }
127
128 mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
129
130 if( ( ret = mbedtls_mpi_read_file( &rsa.N, 16, f ) ) != 0 ||
131 ( ret = mbedtls_mpi_read_file( &rsa.E, 16, f ) ) != 0 )
132 {
133 mbedtls_printf( " failed\n ! mbedtls_mpi_read_file returned %d\n\n", ret );
134 fclose( f );
135 goto exit;
136 }
137
138 rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
139
140 fclose( f );
141
142 /*
143 * 3. Initiate the connection
144 */
145 mbedtls_printf( "\n . Connecting to tcp/%s/%s", SERVER_NAME,
146 SERVER_PORT );
147 fflush( stdout );
148
149 if( ( ret = mbedtls_net_connect( &server_fd, SERVER_NAME,
150 SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
151 {
152 mbedtls_printf( " failed\n ! mbedtls_net_connect returned %d\n\n", ret );
153 goto exit;
154 }
155
156 /*
157 * 4a. First get the buffer length
158 */
159 mbedtls_printf( "\n . Receiving the server's DH parameters" );
160 fflush( stdout );
161
162 memset( buf, 0, sizeof( buf ) );
163
164 if( ( ret = mbedtls_net_recv( &server_fd, buf, 2 ) ) != 2 )
165 {
166 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
167 goto exit;
168 }
169
170 n = buflen = ( buf[0] << 8 ) | buf[1];
171 if( buflen < 1 || buflen > sizeof( buf ) )
172 {
173 mbedtls_printf( " failed\n ! Got an invalid buffer length\n\n" );
174 goto exit;
175 }
176
177 /*
178 * 4b. Get the DHM parameters: P, G and Ys = G^Xs mod P
179 */
180 memset( buf, 0, sizeof( buf ) );
181
182 if( ( ret = mbedtls_net_recv( &server_fd, buf, n ) ) != (int) n )
183 {
184 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
185 goto exit;
186 }
187
188 p = buf, end = buf + buflen;
189
190 if( ( ret = mbedtls_dhm_read_params( &dhm, &p, end ) ) != 0 )
191 {
192 mbedtls_printf( " failed\n ! mbedtls_dhm_read_params returned %d\n\n", ret );
193 goto exit;
194 }
195
196 if( dhm.len < 64 || dhm.len > 512 )
197 {
198 mbedtls_printf( " failed\n ! Invalid DHM modulus size\n\n" );
199 goto exit;
200 }
201
202 /*
203 * 5. Check that the server's RSA signature matches
204 * the SHA-256 hash of (P,G,Ys)
205 */
206 mbedtls_printf( "\n . Verifying the server's RSA signature" );
207 fflush( stdout );
208
209 p += 2;
210
211 if( ( n = (size_t) ( end - p ) ) != rsa.len )
212 {
213 mbedtls_printf( " failed\n ! Invalid RSA signature size\n\n" );
214 goto exit;
215 }
216
217 if( ( ret = mbedtls_sha1_ret( buf, (int)( p - 2 - buf ), hash ) ) != 0 )
218 {
219 mbedtls_printf( " failed\n ! mbedtls_sha1_ret returned %d\n\n", ret );
220 goto exit;
221 }
222
223 if( ( ret = mbedtls_rsa_pkcs1_verify( &rsa, NULL, NULL, MBEDTLS_RSA_PUBLIC,
224 MBEDTLS_MD_SHA256, 0, hash, p ) ) != 0 )
225 {
226 mbedtls_printf( " failed\n ! mbedtls_rsa_pkcs1_verify returned %d\n\n", ret );
227 goto exit;
228 }
229
230 /*
231 * 6. Send our public value: Yc = G ^ Xc mod P
232 */
233 mbedtls_printf( "\n . Sending own public value to server" );
234 fflush( stdout );
235
236 n = dhm.len;
237 if( ( ret = mbedtls_dhm_make_public( &dhm, (int) dhm.len, buf, n,
238 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
239 {
240 mbedtls_printf( " failed\n ! mbedtls_dhm_make_public returned %d\n\n", ret );
241 goto exit;
242 }
243
244 if( ( ret = mbedtls_net_send( &server_fd, buf, n ) ) != (int) n )
245 {
246 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
247 goto exit;
248 }
249
250 /*
251 * 7. Derive the shared secret: K = Ys ^ Xc mod P
252 */
253 mbedtls_printf( "\n . Shared secret: " );
254 fflush( stdout );
255
256 if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
257 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
258 {
259 mbedtls_printf( " failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
260 goto exit;
261 }
262
263 for( n = 0; n < 16; n++ )
264 mbedtls_printf( "%02x", buf[n] );
265
266 /*
267 * 8. Setup the AES-256 decryption key
268 *
269 * This is an overly simplified example; best practice is
270 * to hash the shared secret with a random value to derive
271 * the keying material for the encryption/decryption keys,
272 * IVs and MACs.
273 */
274 mbedtls_printf( "...\n . Receiving and decrypting the ciphertext" );
275 fflush( stdout );
276
277 ret = mbedtls_aes_setkey_dec( &aes, buf, 256 );
278 if( ret != 0 )
279 goto exit;
280
281 memset( buf, 0, sizeof( buf ) );
282
283 if( ( ret = mbedtls_net_recv( &server_fd, buf, 16 ) ) != 16 )
284 {
285 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
286 goto exit;
287 }
288
289 ret = mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_DECRYPT, buf, buf );
290 if( ret != 0 )
291 goto exit;
292 buf[16] = '\0';
293 mbedtls_printf( "\n . Plaintext is \"%s\"\n\n", (char *) buf );
294
295 exit_code = MBEDTLS_EXIT_SUCCESS;
296
297 exit:
298
299 mbedtls_net_free( &server_fd );
300
301 mbedtls_aes_free( &aes );
302 mbedtls_rsa_free( &rsa );
303 mbedtls_dhm_free( &dhm );
304 mbedtls_ctr_drbg_free( &ctr_drbg );
305 mbedtls_entropy_free( &entropy );
306
307 #if defined(_WIN32)
308 mbedtls_printf( " + Press Enter to exit this program.\n" );
309 fflush( stdout ); getchar();
310 #endif
311
312 mbedtls_exit( exit_code );
313 }
314 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
315 MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
316 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
317
