dh_server.c (9531B)
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) 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 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 */