esp-idf/examples/bluetooth/blufi/main/blufi_security.c

// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event_loop.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "bt.h"

#include "esp_blufi_api.h"
#include "esp_bt_defs.h"
#include "esp_gap_ble_api.h"
#include "esp_bt_main.h"
#include "blufi_example.h"

#include "mbedtls/aes.h"
#include "mbedtls/dhm.h"
#include "mbedtls/md5.h"
#include "rom/crc.h"

/*
   The SEC_TYPE_xxx is for self-defined packet data type in the procedure of "BLUFI negotiate key"
   If user use other negotiation procedure to exchange(or generate) key, should redefine the type by yourself.
 */
#define SEC_TYPE_DH_PARAM_LEN   0x00
#define SEC_TYPE_DH_PARAM_DATA  0x01
#define SEC_TYPE_DH_P           0x02
#define SEC_TYPE_DH_G           0x03
#define SEC_TYPE_DH_PUBLIC      0x04


struct blufi_security {
#define DH_SELF_PUB_KEY_LEN     128
#define DH_SELF_PUB_KEY_BIT_LEN (DH_SELF_PUB_KEY_LEN * 8)
    uint8_t  self_public_key[DH_SELF_PUB_KEY_LEN];
#define SHARE_KEY_LEN           128
#define SHARE_KEY_BIT_LEN       (SHARE_KEY_LEN * 8)
    uint8_t  share_key[SHARE_KEY_LEN];
    size_t   share_len;
#define PSK_LEN                 16
    uint8_t  psk[PSK_LEN];
    uint8_t  *dh_param;
    int      dh_param_len;
    uint8_t  iv[16];
    mbedtls_dhm_context dhm;
    mbedtls_aes_context aes;
};
static struct blufi_security *blufi_sec;

static int myrand( void *rng_state, unsigned char *output, size_t len )
{
    size_t i;

    for( i = 0; i < len; ++i )
        output[i] = esp_random();

    return( 0 );
}

void blufi_dh_negotiate_data_handler(uint8_t *data, int len, uint8_t **output_data, int *output_len, bool *need_free)
{
    int ret;
    uint8_t type = data[0];

    if (blufi_sec == NULL) {
        BLUFI_ERROR("BLUFI Security is not initialized");
        return;
    }

    switch (type) {
    case SEC_TYPE_DH_PARAM_LEN:
        blufi_sec->dh_param_len = ((data[1]<<8)|data[2]);
        if (blufi_sec->dh_param) {
            free(blufi_sec->dh_param);
        }
        blufi_sec->dh_param = (uint8_t *)malloc(blufi_sec->dh_param_len);
        if (blufi_sec->dh_param == NULL) {
            return;
        }
        break;
    case SEC_TYPE_DH_PARAM_DATA:

        memcpy(blufi_sec->dh_param, &data[1], blufi_sec->dh_param_len);

        ret = mbedtls_dhm_read_params(&blufi_sec->dhm, &blufi_sec->dh_param, &blufi_sec->dh_param[blufi_sec->dh_param_len]);
        if (ret) {
            BLUFI_ERROR("%s read param failed %d\n", __func__, ret);
            return;
        }

        ret = mbedtls_dhm_make_public(&blufi_sec->dhm, (int) mbedtls_mpi_size( &blufi_sec->dhm.P ), blufi_sec->self_public_key, blufi_sec->dhm.len, myrand, NULL);
        if (ret) {
            BLUFI_ERROR("%s make public failed %d\n", __func__, ret);
            return;
        }

        mbedtls_dhm_calc_secret( &blufi_sec->dhm,
                blufi_sec->share_key,
                SHARE_KEY_BIT_LEN,
                &blufi_sec->share_len,
                NULL, NULL);

        mbedtls_md5(blufi_sec->share_key, blufi_sec->share_len, blufi_sec->psk);

        mbedtls_aes_setkey_enc(&blufi_sec->aes, blufi_sec->psk, 128);
        mbedtls_aes_setkey_dec(&blufi_sec->aes, blufi_sec->psk, 128);
        
        /* alloc output data */
        *output_data = &blufi_sec->self_public_key[0];
        *output_len = blufi_sec->dhm.len;
        *need_free = false;
        break;
    case SEC_TYPE_DH_P:
        break;
    case SEC_TYPE_DH_G:
        break;
    case SEC_TYPE_DH_PUBLIC:
        break;
    }
}

int blufi_aes_encrypt(uint8_t iv8, uint8_t *crypt_data, int crypt_len)
{
    int ret;
    size_t iv_offset = 0;
    uint8_t iv0[16];

    memcpy(iv0, blufi_sec->iv, sizeof(blufi_sec->iv));
    iv0[0] = iv8;   /* set iv8 as the iv0[0] */

    ret = mbedtls_aes_crypt_cfb128(&blufi_sec->aes, MBEDTLS_AES_ENCRYPT, crypt_len, &iv_offset, iv0, crypt_data, crypt_data);
    if (ret) {
        return -1;
    }

    return crypt_len;
}

int blufi_aes_decrypt(uint8_t iv8, uint8_t *crypt_data, int crypt_len)
{
    int ret;
    size_t iv_offset = 0;
    uint8_t iv0[16];

    memcpy(iv0, blufi_sec->iv, sizeof(blufi_sec->iv));
    iv0[0] = iv8;   /* set iv8 as the iv0[0] */

    ret = mbedtls_aes_crypt_cfb128(&blufi_sec->aes, MBEDTLS_AES_DECRYPT, crypt_len, &iv_offset, iv0, crypt_data, crypt_data);
    if (ret) {
        return -1;
    }

    return crypt_len;
}

uint16_t blufi_crc_checksum(uint8_t iv8, uint8_t *data, int len)
{
    /* This iv8 ignore, not used */
    return crc16_be(0, data, len);
}

esp_err_t blufi_security_init(void)
{
    blufi_sec = (struct blufi_security *)malloc(sizeof(struct blufi_security));
    if (blufi_sec == NULL) {
        return ESP_FAIL;
    }

    memset(blufi_sec, 0x0, sizeof(struct blufi_security));

    mbedtls_dhm_init(&blufi_sec->dhm);
    mbedtls_aes_init(&blufi_sec->aes);

    memset(blufi_sec->iv, 0x0, 16);
    return 0;
}

void blufi_security_deinit(void)
{
    mbedtls_dhm_free(&blufi_sec->dhm);
    mbedtls_aes_free(&blufi_sec->aes);

    memset(blufi_sec, 0x0, sizeof(struct blufi_security));

    free(blufi_sec);
    blufi_sec =  NULL;
}