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 mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
102 goto exit;
103 }
104
105 /*
106 * 2a. Read the server's private RSA key
107 */
108 mbedtls_printf("\n . Reading private key from rsa_priv.txt");
109 fflush(stdout);
110
111 if ((f = fopen("rsa_priv.txt", "rb")) == NULL) {
112 mbedtls_printf(" failed\n ! Could not open rsa_priv.txt\n" \
113 " ! Please run rsa_genkey first\n\n");
114 goto exit;
115 }
116
117 mbedtls_rsa_init(&rsa);
118
119 if ((ret = mbedtls_mpi_read_file(&N, 16, f)) != 0 ||
120 (ret = mbedtls_mpi_read_file(&E, 16, f)) != 0 ||
121 (ret = mbedtls_mpi_read_file(&D, 16, f)) != 0 ||
122 (ret = mbedtls_mpi_read_file(&P, 16, f)) != 0 ||
123 (ret = mbedtls_mpi_read_file(&Q, 16, f)) != 0) {
124 mbedtls_printf(" failed\n ! mbedtls_mpi_read_file returned %d\n\n",
125 ret);
126 fclose(f);
127 goto exit;
128 }
129 fclose(f);
130
131 if ((ret = mbedtls_rsa_import(&rsa, &N, &P, &Q, &D, &E)) != 0) {
132 mbedtls_printf(" failed\n ! mbedtls_rsa_import returned %d\n\n",
133 ret);
134 goto exit;
135 }
136
137 if ((ret = mbedtls_rsa_complete(&rsa)) != 0) {
138 mbedtls_printf(" failed\n ! mbedtls_rsa_complete returned %d\n\n",
139 ret);
140 goto exit;
141 }
142
143 /*
144 * 2b. Get the DHM modulus and generator
145 */
146 mbedtls_printf("\n . Reading DH parameters from dh_prime.txt");
147 fflush(stdout);
148
149 if ((f = fopen("dh_prime.txt", "rb")) == NULL) {
150 mbedtls_printf(" failed\n ! Could not open dh_prime.txt\n" \
151 " ! Please run dh_genprime first\n\n");
152 goto exit;
153 }
154
155 if (mbedtls_mpi_read_file(&dhm.MBEDTLS_PRIVATE(P), 16, f) != 0 ||
156 mbedtls_mpi_read_file(&dhm.MBEDTLS_PRIVATE(G), 16, f) != 0) {
157 mbedtls_printf(" failed\n ! Invalid DH parameter file\n\n");
158 fclose(f);
159 goto exit;
160 }
161
162 fclose(f);
163
164 /*
165 * 3. Wait for a client to connect
166 */
167 mbedtls_printf("\n . Waiting for a remote connection");
168 fflush(stdout);
169
170 if ((ret = mbedtls_net_bind(&listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP)) != 0) {
171 mbedtls_printf(" failed\n ! mbedtls_net_bind returned %d\n\n", ret);
172 goto exit;
173 }
174
175 if ((ret = mbedtls_net_accept(&listen_fd, &client_fd,
176 NULL, 0, NULL)) != 0) {
177 mbedtls_printf(" failed\n ! mbedtls_net_accept returned %d\n\n", ret);
178 goto exit;
179 }
180
181 /*
182 * 4. Setup the DH parameters (P,G,Ys)
183 */
184 mbedtls_printf("\n . Sending the server's DH parameters");
185 fflush(stdout);
186
187 memset(buf, 0, sizeof(buf));
188
189 if ((ret =
190 mbedtls_dhm_make_params(&dhm, (int) mbedtls_mpi_size(&dhm.MBEDTLS_PRIVATE(P)), buf, &n,
191 mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
192 mbedtls_printf(" failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret);
193 goto exit;
194 }
195
196 /*
197 * 5. Sign the parameters and send them
198 */
199 if ((ret = mbedtls_sha1(buf, n, hash)) != 0) {
200 mbedtls_printf(" failed\n ! mbedtls_sha1 returned %d\n\n", ret);
201 goto exit;
202 }
203
204 buf[n] = (unsigned char) (rsa.MBEDTLS_PRIVATE(len) >> 8);
205 buf[n + 1] = (unsigned char) (rsa.MBEDTLS_PRIVATE(len));
206
207 if ((ret = mbedtls_rsa_pkcs1_sign(&rsa, NULL, NULL, MBEDTLS_MD_SHA256,
208 32, hash, buf + n + 2)) != 0) {
209 mbedtls_printf(" failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret);
210 goto exit;
211 }
212
213 buflen = n + 2 + rsa.MBEDTLS_PRIVATE(len);
214 buf2[0] = (unsigned char) (buflen >> 8);
215 buf2[1] = (unsigned char) (buflen);
216
217 if ((ret = mbedtls_net_send(&client_fd, buf2, 2)) != 2 ||
218 (ret = mbedtls_net_send(&client_fd, buf, buflen)) != (int) buflen) {
219 mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
220 goto exit;
221 }
222
223 /*
224 * 6. Get the client's public value: Yc = G ^ Xc mod P
225 */
226 mbedtls_printf("\n . Receiving the client's public value");
227 fflush(stdout);
228
229 memset(buf, 0, sizeof(buf));
230
231 n = mbedtls_dhm_get_len(&dhm);
232 if ((ret = mbedtls_net_recv(&client_fd, buf, n)) != (int) n) {
233 mbedtls_printf(" failed\n ! mbedtls_net_recv returned %d\n\n", ret);
234 goto exit;
235 }
236
237 if ((ret = mbedtls_dhm_read_public(&dhm, buf, n)) != 0) {
238 mbedtls_printf(" failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret);
239 goto exit;
240 }
241
242 /*
243 * 7. Derive the shared secret: K = Ys ^ Xc mod P
244 */
245 mbedtls_printf("\n . Shared secret: ");
246 fflush(stdout);
247
248 if ((ret = mbedtls_dhm_calc_secret(&dhm, buf, sizeof(buf), &n,
249 mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
250 mbedtls_printf(" failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret);
251 goto exit;
252 }
253
254 for (n = 0; n < 16; n++) {
255 mbedtls_printf("%02x", buf[n]);
256 }
257
258 /*
259 * 8. Setup the AES-256 encryption key
260 *
261 * This is an overly simplified example; best practice is
262 * to hash the shared secret with a random value to derive
263 * the keying material for the encryption/decryption keys
264 * and MACs.
265 */
266 mbedtls_printf("...\n . Encrypting and sending the ciphertext");
267 fflush(stdout);
268
269 ret = mbedtls_aes_setkey_enc(&aes, buf, 256);
270 if (ret != 0) {
271 goto exit;
272 }
273 memcpy(buf, PLAINTEXT, 16);
274 ret = mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_ENCRYPT, buf, buf);
275 if (ret != 0) {
276 goto exit;
277 }
278
279 if ((ret = mbedtls_net_send(&client_fd, buf, 16)) != 16) {
280 mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
281 goto exit;
282 }
283
284 mbedtls_printf("\n\n");
285
286 exit_code = MBEDTLS_EXIT_SUCCESS;
287
288 exit:
289
290 mbedtls_mpi_free(&N); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
291 mbedtls_mpi_free(&D); mbedtls_mpi_free(&E);
292
293 mbedtls_net_free(&client_fd);
294 mbedtls_net_free(&listen_fd);
295
296 mbedtls_aes_free(&aes);
297 mbedtls_rsa_free(&rsa);
298 mbedtls_dhm_free(&dhm);
299 mbedtls_ctr_drbg_free(&ctr_drbg);
300 mbedtls_entropy_free(&entropy);
301
302 mbedtls_exit(exit_code);
303 }
304 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
305 MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
306 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
307