283 lines
8.2 KiB
C
283 lines
8.2 KiB
C
/*
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* Diffie-Hellman-Merkle key exchange (client side)
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#include "mbedtls/build_info.h"
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#include "mbedtls/platform.h"
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/* md.h is included this early since MD_CAN_XXX macros are defined there. */
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#include "mbedtls/md.h"
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#if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
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defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
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defined(MBEDTLS_RSA_C) && defined(MBEDTLS_MD_CAN_SHA256) && \
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defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C)
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#include "mbedtls/net_sockets.h"
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#include "mbedtls/aes.h"
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#include "mbedtls/dhm.h"
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#include "mbedtls/rsa.h"
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#include "mbedtls/sha1.h"
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#include "mbedtls/entropy.h"
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#include "mbedtls/ctr_drbg.h"
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#include <stdio.h>
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#include <string.h>
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#endif
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#define SERVER_NAME "localhost"
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#define SERVER_PORT "11999"
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#define MBEDTLS_MD_CAN_SHA256_MAX_SIZE 32
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#if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
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!defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
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!defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_MD_CAN_SHA256) || \
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!defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C)
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int main(void)
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{
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mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
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"and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
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"MBEDTLS_MD_CAN_SHA256 and/or MBEDTLS_FS_IO and/or "
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"MBEDTLS_CTR_DRBG_C not defined.\n");
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mbedtls_exit(0);
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}
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#elif defined(MBEDTLS_BLOCK_CIPHER_NO_DECRYPT)
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int main(void)
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{
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mbedtls_printf("MBEDTLS_BLOCK_CIPHER_NO_DECRYPT defined.\n");
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mbedtls_exit(0);
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}
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#else
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int main(void)
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{
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FILE *f;
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int ret = 1;
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int exit_code = MBEDTLS_EXIT_FAILURE;
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size_t n, buflen;
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mbedtls_net_context server_fd;
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unsigned char *p, *end;
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unsigned char buf[2048];
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unsigned char hash[MBEDTLS_MD_CAN_SHA256_MAX_SIZE];
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mbedtls_mpi N, E;
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const char *pers = "dh_client";
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mbedtls_entropy_context entropy;
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mbedtls_ctr_drbg_context ctr_drbg;
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mbedtls_rsa_context rsa;
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mbedtls_dhm_context dhm;
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mbedtls_aes_context aes;
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mbedtls_net_init(&server_fd);
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mbedtls_dhm_init(&dhm);
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mbedtls_aes_init(&aes);
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mbedtls_ctr_drbg_init(&ctr_drbg);
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mbedtls_mpi_init(&N);
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mbedtls_mpi_init(&E);
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/*
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* 1. Setup the RNG
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*/
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mbedtls_printf("\n . Seeding the random number generator");
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fflush(stdout);
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mbedtls_entropy_init(&entropy);
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if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
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(const unsigned char *) pers,
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strlen(pers))) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret);
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goto exit;
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}
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/*
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* 2. Read the server's public RSA key
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*/
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mbedtls_printf("\n . Reading public key from rsa_pub.txt");
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fflush(stdout);
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if ((f = fopen("rsa_pub.txt", "rb")) == NULL) {
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mbedtls_printf(" failed\n ! Could not open rsa_pub.txt\n" \
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" ! Please run rsa_genkey first\n\n");
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goto exit;
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}
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mbedtls_rsa_init(&rsa);
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if ((ret = mbedtls_mpi_read_file(&N, 16, f)) != 0 ||
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(ret = mbedtls_mpi_read_file(&E, 16, f)) != 0 ||
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(ret = mbedtls_rsa_import(&rsa, &N, NULL, NULL, NULL, &E) != 0)) {
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mbedtls_printf(" failed\n ! mbedtls_mpi_read_file returned %d\n\n", ret);
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fclose(f);
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goto exit;
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}
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fclose(f);
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/*
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* 3. Initiate the connection
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*/
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mbedtls_printf("\n . Connecting to tcp/%s/%s", SERVER_NAME,
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SERVER_PORT);
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fflush(stdout);
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if ((ret = mbedtls_net_connect(&server_fd, SERVER_NAME,
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SERVER_PORT, MBEDTLS_NET_PROTO_TCP)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_net_connect returned %d\n\n", ret);
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goto exit;
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}
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/*
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* 4a. First get the buffer length
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*/
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mbedtls_printf("\n . Receiving the server's DH parameters");
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fflush(stdout);
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memset(buf, 0, sizeof(buf));
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if ((ret = mbedtls_net_recv(&server_fd, buf, 2)) != 2) {
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mbedtls_printf(" failed\n ! mbedtls_net_recv returned %d\n\n", ret);
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goto exit;
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}
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n = buflen = (buf[0] << 8) | buf[1];
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if (buflen < 1 || buflen > sizeof(buf)) {
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mbedtls_printf(" failed\n ! Got an invalid buffer length\n\n");
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goto exit;
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}
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/*
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* 4b. Get the DHM parameters: P, G and Ys = G^Xs mod P
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*/
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memset(buf, 0, sizeof(buf));
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if ((ret = mbedtls_net_recv(&server_fd, buf, n)) != (int) n) {
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mbedtls_printf(" failed\n ! mbedtls_net_recv returned %d\n\n", ret);
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goto exit;
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}
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p = buf, end = buf + buflen;
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if ((ret = mbedtls_dhm_read_params(&dhm, &p, end)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_dhm_read_params returned %d\n\n", ret);
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goto exit;
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}
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n = mbedtls_dhm_get_len(&dhm);
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if (n < 64 || n > 512) {
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mbedtls_printf(" failed\n ! Invalid DHM modulus size\n\n");
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goto exit;
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}
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/*
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* 5. Check that the server's RSA signature matches
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* the SHA-256 hash of (P,G,Ys)
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*/
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mbedtls_printf("\n . Verifying the server's RSA signature");
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fflush(stdout);
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p += 2;
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if ((n = (size_t) (end - p)) != mbedtls_rsa_get_len(&rsa)) {
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mbedtls_printf(" failed\n ! Invalid RSA signature size\n\n");
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goto exit;
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}
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if ((ret = mbedtls_sha256(buf, (int) (p - 2 - buf), hash, 0)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_sha1 returned %d\n\n", ret);
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goto exit;
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}
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if ((ret = mbedtls_rsa_pkcs1_verify(&rsa, MBEDTLS_MD_SHA256,
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MBEDTLS_MD_CAN_SHA256_MAX_SIZE, hash, p)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_rsa_pkcs1_verify returned %d\n\n", ret);
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goto exit;
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}
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/*
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* 6. Send our public value: Yc = G ^ Xc mod P
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*/
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mbedtls_printf("\n . Sending own public value to server");
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fflush(stdout);
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n = mbedtls_dhm_get_len(&dhm);
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if ((ret = mbedtls_dhm_make_public(&dhm, (int) n, buf, n,
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mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_dhm_make_public returned %d\n\n", ret);
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goto exit;
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}
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if ((ret = mbedtls_net_send(&server_fd, buf, n)) != (int) n) {
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mbedtls_printf(" failed\n ! mbedtls_net_send returned %d\n\n", ret);
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goto exit;
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}
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/*
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* 7. Derive the shared secret: K = Ys ^ Xc mod P
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*/
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mbedtls_printf("\n . Shared secret: ");
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fflush(stdout);
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if ((ret = mbedtls_dhm_calc_secret(&dhm, buf, sizeof(buf), &n,
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mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
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mbedtls_printf(" failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret);
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goto exit;
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}
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for (n = 0; n < 16; n++) {
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mbedtls_printf("%02x", buf[n]);
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}
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/*
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* 8. Setup the AES-256 decryption key
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*
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* This is an overly simplified example; best practice is
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* to hash the shared secret with a random value to derive
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* the keying material for the encryption/decryption keys,
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* IVs and MACs.
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*/
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mbedtls_printf("...\n . Receiving and decrypting the ciphertext");
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fflush(stdout);
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ret = mbedtls_aes_setkey_dec(&aes, buf, 256);
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if (ret != 0) {
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goto exit;
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}
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memset(buf, 0, sizeof(buf));
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if ((ret = mbedtls_net_recv(&server_fd, buf, 16)) != 16) {
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mbedtls_printf(" failed\n ! mbedtls_net_recv returned %d\n\n", ret);
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goto exit;
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}
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ret = mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_DECRYPT, buf, buf);
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if (ret != 0) {
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goto exit;
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}
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buf[16] = '\0';
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mbedtls_printf("\n . Plaintext is \"%s\"\n\n", (char *) buf);
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exit_code = MBEDTLS_EXIT_SUCCESS;
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exit:
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mbedtls_net_free(&server_fd);
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mbedtls_aes_free(&aes);
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mbedtls_rsa_free(&rsa);
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mbedtls_dhm_free(&dhm);
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mbedtls_ctr_drbg_free(&ctr_drbg);
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mbedtls_entropy_free(&entropy);
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mbedtls_mpi_free(&N);
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mbedtls_mpi_free(&E);
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mbedtls_exit(exit_code);
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}
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#endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
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MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_MD_CAN_SHA256 &&
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MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
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