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
8 #include "mbedtls/build_info.h"
9
10 #include "mbedtls/platform.h"
11 /* md.h is included this early since MD_CAN_XXX macros are defined there. */
12 #include "mbedtls/md.h"
13
14 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
15 defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
16 defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
17 defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C)
18 #include "mbedtls/net_sockets.h"
19 #include "mbedtls/aes.h"
20 #include "mbedtls/dhm.h"
21 #include "mbedtls/rsa.h"
22 #include "mbedtls/sha256.h"
23 #include "mbedtls/entropy.h"
24 #include "mbedtls/ctr_drbg.h"
25
26 #include <stdio.h>
27 #include <string.h>
28 #endif
29
30 #define SERVER_PORT "11999"
31 #define PLAINTEXT "==Hello there!=="
32
33 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
34 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
35 !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) || \
36 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C)
main(void)37 int main(void)
38 {
39 mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
40 "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
41 "MBEDTLS_MD_CAN_SHA256 and/or MBEDTLS_FS_IO and/or "
42 "MBEDTLS_CTR_DRBG_C and/or MBEDTLS_SHA1_C not defined.\n");
43 mbedtls_exit(0);
44 }
45 #else
46
47
main(void)48 int main(void)
49 {
50 FILE *f;
51
52 int ret = 1;
53 int exit_code = MBEDTLS_EXIT_FAILURE;
54 unsigned int mdlen;
55 size_t n, buflen;
56 mbedtls_net_context listen_fd, client_fd;
57
58 unsigned char buf[2048];
59 unsigned char hash[MBEDTLS_MD_MAX_SIZE];
60 unsigned char buf2[2];
61 const char *pers = "dh_server";
62
63 mbedtls_entropy_context entropy;
64 mbedtls_ctr_drbg_context ctr_drbg;
65 mbedtls_rsa_context rsa;
66 mbedtls_dhm_context dhm;
67 mbedtls_aes_context aes;
68
69 mbedtls_mpi N, P, Q, D, E, dhm_P, dhm_G;
70
71 mbedtls_net_init(&listen_fd);
72 mbedtls_net_init(&client_fd);
73 mbedtls_dhm_init(&dhm);
74 mbedtls_aes_init(&aes);
75 mbedtls_ctr_drbg_init(&ctr_drbg);
76
77 mbedtls_mpi_init(&N); mbedtls_mpi_init(&P); mbedtls_mpi_init(&Q);
78 mbedtls_mpi_init(&D); mbedtls_mpi_init(&E); mbedtls_mpi_init(&dhm_P);
79 mbedtls_mpi_init(&dhm_G);
80 /*
81 * 1. Setup the RNG
82 */
83 mbedtls_printf("\n . Seeding the random number generator");
84 fflush(stdout);
85
86 mbedtls_entropy_init(&entropy);
87 if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
88 (const unsigned char *) pers,
89 strlen(pers))) != 0) {
90 mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
91 goto exit;
92 }
93
94 /*
95 * 2a. Read the server's private RSA key
96 */
97 mbedtls_printf("\n . Reading private key from rsa_priv.txt");
98 fflush(stdout);
99
100 if ((f = fopen("rsa_priv.txt", "rb")) == NULL) {
101 mbedtls_printf(" failed\n ! Could not open rsa_priv.txt\n" \
102 " ! Please run rsa_genkey first\n\n");
103 goto exit;
104 }
105
106 mbedtls_rsa_init(&rsa);
107
108 if ((ret = mbedtls_mpi_read_file(&N, 16, f)) != 0 ||
109 (ret = mbedtls_mpi_read_file(&E, 16, f)) != 0 ||
110 (ret = mbedtls_mpi_read_file(&D, 16, f)) != 0 ||
111 (ret = mbedtls_mpi_read_file(&P, 16, f)) != 0 ||
112 (ret = mbedtls_mpi_read_file(&Q, 16, f)) != 0) {
113 mbedtls_printf(" failed\n ! mbedtls_mpi_read_file returned %d\n\n",
114 ret);
115 fclose(f);
116 goto exit;
117 }
118 fclose(f);
119
120 if ((ret = mbedtls_rsa_import(&rsa, &N, &P, &Q, &D, &E)) != 0) {
121 mbedtls_printf(" failed\n ! mbedtls_rsa_import returned %d\n\n",
122 ret);
123 goto exit;
124 }
125
126 if ((ret = mbedtls_rsa_complete(&rsa)) != 0) {
127 mbedtls_printf(" failed\n ! mbedtls_rsa_complete returned %d\n\n",
128 ret);
129 goto exit;
130 }
131
132 /*
133 * 2b. Get the DHM modulus and generator
134 */
135 mbedtls_printf("\n . Reading DH parameters from dh_prime.txt");
136 fflush(stdout);
137
138 if ((f = fopen("dh_prime.txt", "rb")) == NULL) {
139 mbedtls_printf(" failed\n ! Could not open dh_prime.txt\n" \
140 " ! Please run dh_genprime first\n\n");
141 goto exit;
142 }
143
144 if ((ret = mbedtls_mpi_read_file(&dhm_P, 16, f)) != 0 ||
145 (ret = mbedtls_mpi_read_file(&dhm_G, 16, f)) != 0 ||
146 (ret = mbedtls_dhm_set_group(&dhm, &dhm_P, &dhm_G) != 0)) {
147 mbedtls_printf(" failed\n ! Invalid DH parameter file\n\n");
148 fclose(f);
149 goto exit;
150 }
151
152 fclose(f);
153
154 /*
155 * 3. Wait for a client to connect
156 */
157 mbedtls_printf("\n . Waiting for a remote connection");
158 fflush(stdout);
159
160 if ((ret = mbedtls_net_bind(&listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP)) != 0) {
161 mbedtls_printf(" failed\n ! mbedtls_net_bind returned %d\n\n", ret);
162 goto exit;
163 }
164
165 if ((ret = mbedtls_net_accept(&listen_fd, &client_fd,
166 NULL, 0, NULL)) != 0) {
167 mbedtls_printf(" failed\n ! mbedtls_net_accept returned %d\n\n", ret);
168 goto exit;
169 }
170
171 /*
172 * 4. Setup the DH parameters (P,G,Ys)
173 */
174 mbedtls_printf("\n . Sending the server's DH parameters");
175 fflush(stdout);
176
177 memset(buf, 0, sizeof(buf));
178
179 if ((ret =
180 mbedtls_dhm_make_params(&dhm, (int) mbedtls_dhm_get_len(&dhm), buf, &n,
181 mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
182 mbedtls_printf(" failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret);
183 goto exit;
184 }
185
186 /*
187 * 5. Sign the parameters and send them
188 */
189
190 mdlen = (unsigned int) mbedtls_md_get_size(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256));
191 if (mdlen == 0) {
192 mbedtls_printf(" failed\n ! Invalid digest type\n\n");
193 goto exit;
194 }
195
196 if ((ret = mbedtls_sha256(buf, n, hash, 0)) != 0) {
197 mbedtls_printf(" failed\n ! mbedtls_sha256 returned %d\n\n", ret);
198 goto exit;
199 }
200
201 const size_t rsa_key_len = mbedtls_rsa_get_len(&rsa);
202 buf[n] = (unsigned char) (rsa_key_len >> 8);
203 buf[n + 1] = (unsigned char) (rsa_key_len);
204
205 if ((ret = mbedtls_rsa_pkcs1_sign(&rsa, mbedtls_ctr_drbg_random, &ctr_drbg,
206 MBEDTLS_MD_SHA256, mdlen,
207 hash, buf + n + 2)) != 0) {
208 mbedtls_printf(" failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret);
209 goto exit;
210 }
211
212 buflen = n + 2 + rsa_key_len;
213 buf2[0] = (unsigned char) (buflen >> 8);
214 buf2[1] = (unsigned char) (buflen);
215
216 if ((ret = mbedtls_net_send(&client_fd, buf2, 2)) != 2 ||
217 (ret = mbedtls_net_send(&client_fd, buf, buflen)) != (int) buflen) {
218 mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
219 goto exit;
220 }
221
222 /*
223 * 6. Get the client's public value: Yc = G ^ Xc mod P
224 */
225 mbedtls_printf("\n . Receiving the client's public value");
226 fflush(stdout);
227
228 memset(buf, 0, sizeof(buf));
229
230 n = mbedtls_dhm_get_len(&dhm);
231 if ((ret = mbedtls_net_recv(&client_fd, buf, n)) != (int) n) {
232 mbedtls_printf(" failed\n ! mbedtls_net_recv returned %d\n\n", ret);
233 goto exit;
234 }
235
236 if ((ret = mbedtls_dhm_read_public(&dhm, buf, n)) != 0) {
237 mbedtls_printf(" failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret);
238 goto exit;
239 }
240
241 /*
242 * 7. Derive the shared secret: K = Ys ^ Xc mod P
243 */
244 mbedtls_printf("\n . Shared secret: ");
245 fflush(stdout);
246
247 if ((ret = mbedtls_dhm_calc_secret(&dhm, buf, sizeof(buf), &n,
248 mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
249 mbedtls_printf(" failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret);
250 goto exit;
251 }
252
253 for (n = 0; n < 16; n++) {
254 mbedtls_printf("%02x", buf[n]);
255 }
256
257 /*
258 * 8. Setup the AES-256 encryption key
259 *
260 * This is an overly simplified example; best practice is
261 * to hash the shared secret with a random value to derive
262 * the keying material for the encryption/decryption keys
263 * and MACs.
264 */
265 mbedtls_printf("...\n . Encrypting and sending the ciphertext");
266 fflush(stdout);
267
268 ret = mbedtls_aes_setkey_enc(&aes, buf, 256);
269 if (ret != 0) {
270 goto exit;
271 }
272 memcpy(buf, PLAINTEXT, 16);
273 ret = mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_ENCRYPT, buf, buf);
274 if (ret != 0) {
275 goto exit;
276 }
277
278 if ((ret = mbedtls_net_send(&client_fd, buf, 16)) != 16) {
279 mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
280 goto exit;
281 }
282
283 mbedtls_printf("\n\n");
284
285 exit_code = MBEDTLS_EXIT_SUCCESS;
286
287 exit:
288
289 mbedtls_mpi_free(&N); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
290 mbedtls_mpi_free(&D); mbedtls_mpi_free(&E); mbedtls_mpi_free(&dhm_P);
291 mbedtls_mpi_free(&dhm_G);
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_MD_CAN_SHA256 &&
306 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
307
