/*
* Diffie-Hellman-Merkle key exchange (server side)
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#include "mbedtls/build_info.h"
#include "mbedtls/platform.h"
/* md.h is included this early since MD_CAN_XXX macros are defined there. */
#include "mbedtls/md.h"
#if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C)
#include "mbedtls/net_sockets.h"
#include "mbedtls/aes.h"
#include "mbedtls/dhm.h"
#include "mbedtls/rsa.h"
#include "mbedtls/sha256.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include <stdio.h>
#include <string.h>
#endif
#define SERVER_PORT "11999"
#define PLAINTEXT "==Hello there!=="
#if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
!defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
!defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) || \
!defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C)
int main(void)
{
mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
"and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
"PSA_WANT_ALG_SHA_256 and/or MBEDTLS_FS_IO and/or "
"MBEDTLS_CTR_DRBG_C and/or MBEDTLS_SHA1_C not defined.\n");
mbedtls_exit(0);
}
#else
int main(void)
{
FILE *f;
int ret = 1;
int exit_code = MBEDTLS_EXIT_FAILURE;
unsigned int mdlen;
size_t n, buflen;
mbedtls_net_context listen_fd, client_fd;
unsigned char buf[2048];
unsigned char hash[MBEDTLS_MD_MAX_SIZE];
unsigned char buf2[2];
const char *pers = "dh_server";
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_rsa_context rsa;
mbedtls_dhm_context dhm;
mbedtls_aes_context aes;
mbedtls_mpi N, P, Q, D, E, dhm_P, dhm_G;
mbedtls_net_init(&listen_fd);
mbedtls_net_init(&client_fd);
mbedtls_dhm_init(&dhm);
mbedtls_aes_init(&aes);
mbedtls_ctr_drbg_init(&ctr_drbg);
mbedtls_mpi_init(&N); mbedtls_mpi_init(&P); mbedtls_mpi_init(&Q);
mbedtls_mpi_init(&D); mbedtls_mpi_init(&E); mbedtls_mpi_init(&dhm_P);
mbedtls_mpi_init(&dhm_G);
/*
* 1. Setup the RNG
*/
mbedtls_printf("\n . Seeding the random number generator");
fflush(stdout);
mbedtls_entropy_init(&entropy);
if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
(const unsigned char *) pers,
strlen(pers))) != 0) {
mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
goto exit;
}
/*
* 2a. Read the server's private RSA key
*/
mbedtls_printf("\n . Reading private key from rsa_priv.txt");
fflush(stdout);
if ((f = fopen("rsa_priv.txt", "rb")) == NULL) {
mbedtls_printf(" failed\n ! Could not open rsa_priv.txt\n" \
" ! Please run rsa_genkey first\n\n");
goto exit;
}
mbedtls_rsa_init(&rsa);
if ((ret = mbedtls_mpi_read_file(&N, 16, f)) != 0 ||
(ret = mbedtls_mpi_read_file(&E, 16, f)) != 0 ||
(ret = mbedtls_mpi_read_file(&D, 16, f)) != 0 ||
(ret = mbedtls_mpi_read_file(&P, 16, f)) != 0 ||
(ret = mbedtls_mpi_read_file(&Q, 16, f)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_mpi_read_file returned %d\n\n",
ret);
fclose(f);
goto exit;
}
fclose(f);
if ((ret = mbedtls_rsa_import(&rsa, &N, &P, &Q, &D, &E)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_rsa_import returned %d\n\n",
ret);
goto exit;
}
if ((ret = mbedtls_rsa_complete(&rsa)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_rsa_complete returned %d\n\n",
ret);
goto exit;
}
/*
* 2b. Get the DHM modulus and generator
*/
mbedtls_printf("\n . Reading DH parameters from dh_prime.txt");
fflush(stdout);
if ((f = fopen("dh_prime.txt", "rb")) == NULL) {
mbedtls_printf(" failed\n ! Could not open dh_prime.txt\n" \
" ! Please run dh_genprime first\n\n");
goto exit;
}
if ((ret = mbedtls_mpi_read_file(&dhm_P, 16, f)) != 0 ||
(ret = mbedtls_mpi_read_file(&dhm_G, 16, f)) != 0 ||
(ret = mbedtls_dhm_set_group(&dhm, &dhm_P, &dhm_G) != 0)) {
mbedtls_printf(" failed\n ! Invalid DH parameter file\n\n");
fclose(f);
goto exit;
}
fclose(f);
/*
* 3. Wait for a client to connect
*/
mbedtls_printf("\n . Waiting for a remote connection");
fflush(stdout);
if ((ret = mbedtls_net_bind(&listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_net_bind returned %d\n\n", ret);
goto exit;
}
if ((ret = mbedtls_net_accept(&listen_fd, &client_fd,
NULL, 0, NULL)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_net_accept returned %d\n\n", ret);
goto exit;
}
/*
* 4. Setup the DH parameters (P,G,Ys)
*/
mbedtls_printf("\n . Sending the server's DH parameters");
fflush(stdout);
memset(buf, 0, sizeof(buf));
if ((ret =
mbedtls_dhm_make_params(&dhm, (int) mbedtls_dhm_get_len(&dhm), buf, &n,
mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret);
goto exit;
}
/*
* 5. Sign the parameters and send them
*/
mdlen = (unsigned int) mbedtls_md_get_size(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256));
if (mdlen == 0) {
mbedtls_printf(" failed\n ! Invalid digest type\n\n");
goto exit;
}
if ((ret = mbedtls_sha256(buf, n, hash, 0)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_sha256 returned %d\n\n", ret);
goto exit;
}
const size_t rsa_key_len = mbedtls_rsa_get_len(&rsa);
buf[n] = (unsigned char) (rsa_key_len >> 8);
buf[n + 1] = (unsigned char) (rsa_key_len);
if ((ret = mbedtls_rsa_pkcs1_sign(&rsa, mbedtls_ctr_drbg_random, &ctr_drbg,
MBEDTLS_MD_SHA256, mdlen,
hash, buf + n + 2)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret);
goto exit;
}
buflen = n + 2 + rsa_key_len;
buf2[0] = (unsigned char) (buflen >> 8);
buf2[1] = (unsigned char) (buflen);
if ((ret = mbedtls_net_send(&client_fd, buf2, 2)) != 2 ||
(ret = mbedtls_net_send(&client_fd, buf, buflen)) != (int) buflen) {
mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
goto exit;
}
/*
* 6. Get the client's public value: Yc = G ^ Xc mod P
*/
mbedtls_printf("\n . Receiving the client's public value");
fflush(stdout);
memset(buf, 0, sizeof(buf));
n = mbedtls_dhm_get_len(&dhm);
if ((ret = mbedtls_net_recv(&client_fd, buf, n)) != (int) n) {
mbedtls_printf(" failed\n ! mbedtls_net_recv returned %d\n\n", ret);
goto exit;
}
if ((ret = mbedtls_dhm_read_public(&dhm, buf, n)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret);
goto exit;
}
/*
* 7. Derive the shared secret: K = Ys ^ Xc mod P
*/
mbedtls_printf("\n . Shared secret: ");
fflush(stdout);
if ((ret = mbedtls_dhm_calc_secret(&dhm, buf, sizeof(buf), &n,
mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret);
goto exit;
}
for (n = 0; n < 16; n++) {
mbedtls_printf("%02x", buf[n]);
}
/*
* 8. Setup the AES-256 encryption key
*
* This is an overly simplified example; best practice is
* to hash the shared secret with a random value to derive
* the keying material for the encryption/decryption keys
* and MACs.
*/
mbedtls_printf("...\n . Encrypting and sending the ciphertext");
fflush(stdout);
ret = mbedtls_aes_setkey_enc(&aes, buf, 256);
if (ret != 0) {
goto exit;
}
memcpy(buf, PLAINTEXT, 16);
ret = mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_ENCRYPT, buf, buf);
if (ret != 0) {
goto exit;
}
if ((ret = mbedtls_net_send(&client_fd, buf, 16)) != 16) {
mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
goto exit;
}
mbedtls_printf("\n\n");
exit_code = MBEDTLS_EXIT_SUCCESS;
exit:
mbedtls_mpi_free(&N); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
mbedtls_mpi_free(&D); mbedtls_mpi_free(&E); mbedtls_mpi_free(&dhm_P);
mbedtls_mpi_free(&dhm_G);
mbedtls_net_free(&client_fd);
mbedtls_net_free(&listen_fd);
mbedtls_aes_free(&aes);
mbedtls_rsa_free(&rsa);
mbedtls_dhm_free(&dhm);
mbedtls_ctr_drbg_free(&ctr_drbg);
mbedtls_entropy_free(&entropy);
mbedtls_exit(exit_code);
}
#endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
MBEDTLS_NET_C && MBEDTLS_RSA_C && PSA_WANT_ALG_SHA_256 &&
MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */