/******************************************************************************
*
* Copyright 2008-2012 Broadcom Corporation
*
* 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.
*
******************************************************************************/
/******************************************************************************
*
* This file contains the implementation of the AES128 CMAC algorithm.
*
******************************************************************************/
#include "bt_target.h"
#include <stdio.h>
#include <string.h>
#include "btm_ble_api.h"
#include "hcimsgs.h"
#include "smp_int.h"
typedef struct {
uint8_t* text;
uint16_t len;
uint16_t round;
} tCMAC_CB;
tCMAC_CB cmac_cb;
/* Rb for AES-128 as block cipher, LSB as [0] */
BT_OCTET16 const_Rb = {0x87, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
void print128(BT_OCTET16 x, const uint8_t* key_name) {
#if (SMP_DEBUG == TRUE && SMP_DEBUG_VERBOSE == TRUE)
uint8_t* p = (uint8_t*)x;
uint8_t i;
SMP_TRACE_WARNING("%s(MSB ~ LSB) = ", key_name);
for (i = 0; i < 4; i++) {
SMP_TRACE_WARNING("%02x %02x %02x %02x", p[BT_OCTET16_LEN - i * 4 - 1],
p[BT_OCTET16_LEN - i * 4 - 2],
p[BT_OCTET16_LEN - i * 4 - 3],
p[BT_OCTET16_LEN - i * 4 - 4]);
}
#endif
}
/*******************************************************************************
*
* Function padding
*
* Description utility function to padding the given text to be a 128 bits
* data. The parameter dest is input and output parameter, it
* must point to a BT_OCTET16_LEN memory space; where include
* length bytes valid data.
*
* Returns void
*
******************************************************************************/
static void padding(BT_OCTET16 dest, uint8_t length) {
uint8_t i, *p = dest;
/* original last block */
for (i = length; i < BT_OCTET16_LEN; i++)
p[BT_OCTET16_LEN - i - 1] = (i == length) ? 0x80 : 0;
}
/*******************************************************************************
*
* Function leftshift_onebit
*
* Description utility function to left shift one bit for a 128 bits value.
*
* Returns void
*
******************************************************************************/
static void leftshift_onebit(uint8_t* input, uint8_t* output) {
uint8_t i, overflow = 0, next_overflow = 0;
SMP_TRACE_EVENT("leftshift_onebit ");
/* input[0] is LSB */
for (i = 0; i < BT_OCTET16_LEN; i++) {
next_overflow = (input[i] & 0x80) ? 1 : 0;
output[i] = (input[i] << 1) | overflow;
overflow = next_overflow;
}
return;
}
/*******************************************************************************
*
* Function cmac_aes_cleanup
*
* Description clean up function for AES_CMAC algorithm.
*
* Returns void
*
******************************************************************************/
static void cmac_aes_cleanup(void) {
osi_free(cmac_cb.text);
memset(&cmac_cb, 0, sizeof(tCMAC_CB));
}
/*******************************************************************************
*
* Function cmac_aes_k_calculate
*
* Description This function is the calculation of block cipher using
* AES-128.
*
* Returns void
*
******************************************************************************/
static bool cmac_aes_k_calculate(BT_OCTET16 key, uint8_t* p_signature,
uint16_t tlen) {
tSMP_ENC output;
uint8_t i = 1, err = 0;
uint8_t x[16] = {0};
uint8_t* p_mac;
SMP_TRACE_EVENT("cmac_aes_k_calculate ");
while (i <= cmac_cb.round) {
smp_xor_128(&cmac_cb.text[(cmac_cb.round - i) * BT_OCTET16_LEN],
x); /* Mi' := Mi (+) X */
if (!SMP_Encrypt(key, BT_OCTET16_LEN,
&cmac_cb.text[(cmac_cb.round - i) * BT_OCTET16_LEN],
BT_OCTET16_LEN, &output)) {
err = 1;
break;
}
memcpy(x, output.param_buf, BT_OCTET16_LEN);
i++;
}
if (!err) {
p_mac = output.param_buf + (BT_OCTET16_LEN - tlen);
memcpy(p_signature, p_mac, tlen);
SMP_TRACE_DEBUG("tlen = %d p_mac = %d", tlen, p_mac);
SMP_TRACE_DEBUG(
"p_mac[0] = 0x%02x p_mac[1] = 0x%02x p_mac[2] = 0x%02x p_mac[3] = "
"0x%02x",
*p_mac, *(p_mac + 1), *(p_mac + 2), *(p_mac + 3));
SMP_TRACE_DEBUG(
"p_mac[4] = 0x%02x p_mac[5] = 0x%02x p_mac[6] = 0x%02x p_mac[7] = "
"0x%02x",
*(p_mac + 4), *(p_mac + 5), *(p_mac + 6), *(p_mac + 7));
return true;
} else
return false;
}
/*******************************************************************************
*
* Function cmac_prepare_last_block
*
* Description This function proceeed to prepare the last block of message
* Mn depending on the size of the message.
*
* Returns void
*
******************************************************************************/
static void cmac_prepare_last_block(BT_OCTET16 k1, BT_OCTET16 k2) {
// uint8_t x[16] = {0};
bool flag;
SMP_TRACE_EVENT("cmac_prepare_last_block ");
/* last block is a complete block set flag to 1 */
flag =
((cmac_cb.len % BT_OCTET16_LEN) == 0 && cmac_cb.len != 0) ? true : false;
SMP_TRACE_WARNING("flag = %d round = %d", flag, cmac_cb.round);
if (flag) { /* last block is complete block */
smp_xor_128(&cmac_cb.text[0], k1);
} else /* padding then xor with k2 */
{
padding(&cmac_cb.text[0], (uint8_t)(cmac_cb.len % 16));
smp_xor_128(&cmac_cb.text[0], k2);
}
}
/*******************************************************************************
*
* Function cmac_subkey_cont
*
* Description This is the callback function when CIPHk(0[128]) is
* completed.
*
* Returns void
*
******************************************************************************/
static void cmac_subkey_cont(tSMP_ENC* p) {
uint8_t k1[BT_OCTET16_LEN], k2[BT_OCTET16_LEN];
uint8_t* pp = p->param_buf;
SMP_TRACE_EVENT("cmac_subkey_cont ");
print128(pp, (const uint8_t*)"K1 before shift");
/* If MSB(L) = 0, then K1 = L << 1 */
if ((pp[BT_OCTET16_LEN - 1] & 0x80) != 0) {
/* Else K1 = ( L << 1 ) (+) Rb */
leftshift_onebit(pp, k1);
smp_xor_128(k1, const_Rb);
} else {
leftshift_onebit(pp, k1);
}
if ((k1[BT_OCTET16_LEN - 1] & 0x80) != 0) {
/* K2 = (K1 << 1) (+) Rb */
leftshift_onebit(k1, k2);
smp_xor_128(k2, const_Rb);
} else {
/* If MSB(K1) = 0, then K2 = K1 << 1 */
leftshift_onebit(k1, k2);
}
print128(k1, (const uint8_t*)"K1");
print128(k2, (const uint8_t*)"K2");
cmac_prepare_last_block(k1, k2);
}
/*******************************************************************************
*
* Function cmac_generate_subkey
*
* Description This is the function to generate the two subkeys.
*
* Parameters key - CMAC key, expect SRK when used by SMP.
*
* Returns void
*
******************************************************************************/
static bool cmac_generate_subkey(BT_OCTET16 key) {
BT_OCTET16 z = {0};
bool ret = true;
tSMP_ENC output;
SMP_TRACE_EVENT(" cmac_generate_subkey");
if (SMP_Encrypt(key, BT_OCTET16_LEN, z, BT_OCTET16_LEN, &output)) {
cmac_subkey_cont(&output);
;
} else
ret = false;
return ret;
}
/*******************************************************************************
*
* Function aes_cipher_msg_auth_code
*
* Description This is the AES-CMAC Generation Function with tlen
* implemented.
*
* Parameters key - CMAC key in little endian order, expect SRK when used
* by SMP.
* input - text to be signed in little endian byte order.
* length - length of the input in byte.
* tlen - lenth of mac desired
* p_signature - data pointer to where signed data to be
* stored, tlen long.
*
* Returns false if out of resources, true in other cases.
*
******************************************************************************/
bool aes_cipher_msg_auth_code(BT_OCTET16 key, uint8_t* input, uint16_t length,
uint16_t tlen, uint8_t* p_signature) {
uint16_t len, diff;
uint16_t n = (length + BT_OCTET16_LEN - 1) /
BT_OCTET16_LEN; /* n is number of rounds */
bool ret = false;
SMP_TRACE_EVENT("%s", __func__);
if (n == 0) n = 1;
len = n * BT_OCTET16_LEN;
SMP_TRACE_WARNING("AES128_CMAC started, allocate buffer size = %d", len);
/* allocate a memory space of multiple of 16 bytes to hold text */
cmac_cb.text = (uint8_t*)osi_calloc(len);
cmac_cb.round = n;
diff = len - length;
if (input != NULL && length > 0) {
memcpy(&cmac_cb.text[diff], input, (int)length);
cmac_cb.len = length;
} else {
cmac_cb.len = 0;
}
/* prepare calculation for subkey s and last block of data */
if (cmac_generate_subkey(key)) {
/* start calculation */
ret = cmac_aes_k_calculate(key, p_signature, tlen);
}
/* clean up */
cmac_aes_cleanup();
return ret;
}