mirror of
https://github.com/yuzu-emu/mbedtls.git
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198 lines
6.4 KiB
C++
198 lines
6.4 KiB
C++
/*
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* Hello world example of using the authenticated encryption with mbed TLS
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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#include "mbedtls/cipher.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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static void print_hex(const char *title, const unsigned char buf[], size_t len)
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{
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printf("%s: ", title);
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for (size_t i = 0; i < len; i++)
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printf("%02x", buf[i]);
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printf("\r\n");
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}
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/*
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* The pre-shared key. Should be generated randomly and be unique to the
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* device/channel/etc. Just used a fixed on here for simplicity.
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*/
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static const unsigned char secret_key[16] = {
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0xf4, 0x82, 0xc6, 0x70, 0x3c, 0xc7, 0x61, 0x0a,
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0xb9, 0xa0, 0xb8, 0xe9, 0x87, 0xb8, 0xc1, 0x72,
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};
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static int example(void)
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{
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/* message that should be protected */
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const char message[] = "Some things are better left unread";
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/* metadata transmitted in the clear but authenticated */
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const char metadata[] = "eg sequence number, routing info";
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/* ciphertext buffer large enough to hold message + nonce + tag */
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unsigned char ciphertext[128] = { 0 };
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int ret;
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printf("\r\n\r\n");
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print_hex("plaintext message", (unsigned char *) message, sizeof message);
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/*
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* Setup random number generator
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* (Note: later this might be done automatically.)
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*/
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mbedtls_entropy_context entropy; /* entropy pool for seeding PRNG */
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mbedtls_ctr_drbg_context drbg; /* pseudo-random generator */
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mbedtls_entropy_init(&entropy);
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mbedtls_ctr_drbg_init(&drbg);
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/* Seed the PRNG using the entropy pool, and throw in our secret key as an
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* additional source of randomness. */
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ret = mbedtls_ctr_drbg_seed(&drbg, mbedtls_entropy_func, &entropy,
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secret_key, sizeof (secret_key));
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if (ret != 0) {
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printf("mbedtls_ctr_drbg_init() returned -0x%04X\r\n", -ret);
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return 1;
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}
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/*
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* Setup AES-CCM contex
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*/
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mbedtls_cipher_context_t ctx;
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mbedtls_cipher_init(&ctx);
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ret = mbedtls_cipher_setup(&ctx, mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_128_CCM));
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if (ret != 0) {
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printf("mbedtls_cipher_setup() returned -0x%04X\r\n", -ret);
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return 1;
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}
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ret = mbedtls_cipher_setkey(&ctx, secret_key, 8 * sizeof secret_key, MBEDTLS_ENCRYPT);
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if (ret != 0) {
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printf("mbedtls_cipher_setkey() returned -0x%04X\r\n", -ret);
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return 1;
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}
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/*
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* Encrypt-authenticate the message and authenticate additional data
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*
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* First generate a random 8-byte nonce.
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* Put it directly in the output buffer as the recipient will need it.
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*
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* Warning: you must never re-use the same (key, nonce) pair. One of the
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* best ways to ensure this to use a counter for the nonce. However this
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* means you should save the counter accross rebots, if the key is a
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* long-term one. The alternative we choose here is to generate the nonce
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* randomly. However it only works if you have a good source of
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* randomness.
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*/
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const size_t nonce_len = 8;
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mbedtls_ctr_drbg_random(&drbg, ciphertext, nonce_len);
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size_t ciphertext_len = 0;
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/* Go for a conservative 16-byte (128-bit) tag
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* and append it to the ciphertext */
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const size_t tag_len = 16;
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ret = mbedtls_cipher_auth_encrypt(&ctx, ciphertext, nonce_len,
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(const unsigned char *) metadata, sizeof metadata,
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(const unsigned char *) message, sizeof message,
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ciphertext + nonce_len, &ciphertext_len,
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ciphertext + nonce_len + sizeof message, tag_len );
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if (ret != 0) {
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printf("mbedtls_cipher_auth_encrypt() returned -0x%04X\r\n", -ret);
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return 1;
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}
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ciphertext_len += nonce_len + tag_len;
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/*
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* The following information should now be transmitted:
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* - first ciphertext_len bytes of ciphertext buffer
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* - metadata if not already transmitted elsewhere
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*/
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print_hex("ciphertext", ciphertext, ciphertext_len);
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/*
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* Decrypt-authenticate
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*/
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unsigned char decrypted[128] = { 0 };
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size_t decrypted_len = 0;
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ret = mbedtls_cipher_setkey(&ctx, secret_key, 8 * sizeof secret_key, MBEDTLS_DECRYPT);
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if (ret != 0) {
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printf("mbedtls_cipher_setkey() returned -0x%04X\r\n", -ret);
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return 1;
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}
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ret = mbedtls_cipher_auth_decrypt(&ctx,
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ciphertext, nonce_len,
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(const unsigned char *) metadata, sizeof metadata,
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ciphertext + nonce_len, ciphertext_len - nonce_len - tag_len,
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decrypted, &decrypted_len,
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ciphertext + ciphertext_len - tag_len, tag_len );
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/* Checking the return code is CRITICAL for security here */
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if (ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED) {
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printf("Something bad is happening! Data is not authentic!\r\n");
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return 1;
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}
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if (ret != 0) {
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printf("mbedtls_cipher_authdecrypt() returned -0x%04X\r\n", -ret);
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return 1;
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}
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print_hex("decrypted", decrypted, decrypted_len);
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printf("\r\nDONE\r\n");
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return 0;
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}
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#if defined(TARGET_LIKE_MBED)
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#include "mbed-drivers/test_env.h"
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#include "minar/minar.h"
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static void run() {
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MBED_HOSTTEST_TIMEOUT(10);
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MBED_HOSTTEST_SELECT(default);
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MBED_HOSTTEST_DESCRIPTION(mbed TLS example authcrypt);
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MBED_HOSTTEST_START("MBEDTLS_EX_AUTHCRYPT");
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MBED_HOSTTEST_RESULT(example() == 0);
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}
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void app_start(int, char*[]) {
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/* Use 115200 bps for consistency with other examples */
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get_stdio_serial().baud(115200);
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minar::Scheduler::postCallback(mbed::util::FunctionPointer0<void>(run).bind());
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}
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#else
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int main() {
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return example();
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}
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#endif
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