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#include "btct.h"
#include <Arduino.h>
#include "HCI.h"
#include "STM32duinoBLE.h"
BluetoothCryptoToolbox::BluetoothCryptoToolbox(){}
// In step 1, AES-128 with key K is applied to an all-zero input block.
// In step 2, K1 is derived through the following operation:
// If the most significant bit of L is equal to 0, K1 is the left-shift
// of L by 1 bit.
// Otherwise, K1 is the exclusive-OR of const_Rb and the left-shift of L
// by 1 bit.
// In step 3, K2 is derived through the following operation:
// If the most significant bit of K1 is equal to 0, K2 is the left-shift
// of K1 by 1 bit.
// Otherwise, K2 is the exclusive-OR of const_Rb and the left-shift of
// K1 by 1 bit.
// In step 4, (K1,K2) := Generate_Subkey(K) is returned.
unsigned char const_Rb[16] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87
};
#define DHKEY_LENGTH 32
#define N_LEN 16
#define ADDR_LEN 6
#define LEN_LTK 16
#define LEN_MAC_KEY 16
void BluetoothCryptoToolbox::printBytes(uint8_t bytes[], uint8_t length){
#ifdef _BLE_TRACE_
for(int i=0; i<length; i++){
if(i>0){
Serial.print(", 0x");
}else{
Serial.print("0x");
}
Serial.print(bytes[i],HEX);
}
Serial.print('\n');
#else
(void)bytes;
(void)length;
#endif
}
int BluetoothCryptoToolbox::f5(uint8_t DHKey[],uint8_t N_master[], uint8_t N_slave[],
uint8_t BD_ADDR_master[], uint8_t BD_ADDR_slave[], uint8_t MacKey[], uint8_t LTK[])
{
uint8_t SALT[16] = {0x6C, 0x88, 0x83, 0x91, 0xAA, 0xF5, 0xA5, 0x38, 0x60, 0x37, 0x0B, 0xDB, 0x5A, 0x60, 0x83, 0xBE};
uint8_t keyID[4] = {0x62, 0x74, 0x6c, 0x65};
uint8_t length[2];
length[0] = 0x01;
length[1] = 0x00;
#ifdef _BLE_TRACE_
Serial.print("Starting f5 calculation");
Serial.print("Using DHKey: ");
printBytes(DHKey, DHKEY_LENGTH);
Serial.print("Using N_Master: ");
printBytes(N_master, N_LEN);
Serial.print("Using N_Slave: ");
printBytes(N_slave, N_LEN);
Serial.println("Using BD_ADDR_MASTER: ");
printBytes(BD_ADDR_master, ADDR_LEN);
Serial.println("Using BD_ADDR_SLAVE: ");
printBytes(BD_ADDR_slave, ADDR_LEN);
#endif
uint8_t T[16];
struct __attribute__ ((packed)) CmacInput
{
uint8_t counter;
uint8_t keyID[4];
uint8_t N1[16];
uint8_t N2[16];
uint8_t A1[7];
uint8_t A2[7];
uint8_t length[2];
} cmacInput = {0,{0},{0},{0},{0},{0},{0}};
cmacInput.counter = 0;
memcpy(cmacInput.keyID, keyID, 4);
memcpy(cmacInput.N1,N_master,16);
memcpy(cmacInput.N2,N_slave,16);
memcpy(cmacInput.A1,BD_ADDR_master,7);
memcpy(cmacInput.A2,BD_ADDR_slave,7);
memcpy(cmacInput.length,length,2);
AES_CMAC(SALT, DHKey, 32, T);
AES_CMAC(T, (uint8_t*)&cmacInput,sizeof(cmacInput), MacKey);
cmacInput.counter=1;
AES_CMAC(T, (uint8_t*)&cmacInput, sizeof(cmacInput), LTK);
return 1;
}
int BluetoothCryptoToolbox::f6(uint8_t W[], uint8_t N1[],uint8_t N2[],uint8_t R[], uint8_t IOCap[], uint8_t A1[], uint8_t A2[], uint8_t Ex[])
{
struct __attribute__ ((packed)) F6Input
{
uint8_t N1[16];
uint8_t N2[16];
uint8_t R[16];
uint8_t IOCap[3];
uint8_t A1[7];
uint8_t A2[7];
} f6Input = {{0},{0},{0},{0},{0},{0}};
memcpy(f6Input.N1, N1, 16);
memcpy(f6Input.N2, N2, 16);
memcpy(f6Input.R, R, 16);
memcpy(f6Input.IOCap, IOCap, 3);
memcpy(f6Input.A1, A1, 7);
memcpy(f6Input.A2, A2, 7);
AES_CMAC(W, (uint8_t*)&f6Input, sizeof(f6Input),Ex);
return 1;
}
// AES_CMAC from RFC
int BluetoothCryptoToolbox::ah(uint8_t k[16], uint8_t r[3], uint8_t* result)
{
uint8_t r_[16];
int i=0;
for(i=0; i<16; i++) r_[i] = 0;
for(i=0; i<3; i++) r_[i+13] = r[i];
uint8_t intermediate[16];
AES_128(k,r_,intermediate);
for(i=0; i<3; i++){
result[i] = intermediate[i+13];
}
return 1;
}
void BluetoothCryptoToolbox::testAh()
{
uint8_t irk[16] = {0xec,0x02,0x34,0xa3,0x57,0xc8,0xad,0x05,0x34,0x10,0x10,0xa6,0x0a,0x39,0x7d,0x9b};
uint8_t expected_final[3] = {0x0d,0xfb,0xaa};
uint8_t ourResult[3];
ah(irk, expected_final, ourResult);
#ifdef _BLE_TRACE_
Serial.print("Expected : ");
printBytes(&expected_final[3], 3);
Serial.print("Actual : ");
printBytes(ourResult, 3);
#endif
}
int BluetoothCryptoToolbox::g2(uint8_t U[], uint8_t V[], uint8_t X[], uint8_t Y[], uint8_t out[4])
{
struct __attribute__ ((packed)) CmacInput {
uint8_t U[32];
uint8_t V[32];
uint8_t Y[16];
} cmacInput= {{0},{0},{0}};
memcpy(cmacInput.U,U,32);
memcpy(cmacInput.V,V,32);
memcpy(cmacInput.Y,Y,16);
uint8_t intermediate[16];
AES_CMAC(X,(uint8_t*)&cmacInput,sizeof(CmacInput),intermediate);
memcpy(out,&intermediate[12],4);
return 1;
}
void BluetoothCryptoToolbox::testg2(){
uint8_t U[32] = {0x20,0xb0,0x03,0xd2,0xf2,0x97,0xbe,0x2c,0x5e,0x2c,0x83,0xa7,0xe9,0xf9,0xa5,0xb9,0xef,0xf4,0x91,0x11,0xac,0xf4,0xfd,0xdb,0xcc,0x03,0x01,0x48,0x0e,0x35,0x9d,0xe6};
uint8_t V[32] = {0x55,0x18,0x8b,0x3d,0x32,0xf6,0xbb,0x9a,0x90,0x0a,0xfc,0xfb,0xee,0xd4,0xe7,0x2a,0x59,0xcb,0x9a,0xc2,0xf1,0x9d,0x7c,0xfb,0x6b,0x4f,0xdd,0x49,0xf4,0x7f,0xc5,0xfd};
uint8_t X[16] = {0xd5,0xcb,0x84,0x54,0xd1,0x77,0x73,0x3e,0xff,0xff,0xb2,0xec,0x71,0x2b,0xae,0xab};
uint8_t Y[16] = {0xa6,0xe8,0xe7,0xcc,0x25,0xa7,0x5f,0x6e,0x21,0x65,0x83,0xf7,0xff,0x3d,0xc4,0xcf};
uint8_t out[4];
g2(U,V,X,Y,out);
uint32_t result = 0;
for(int i=0; i<4; i++) result += out[i] << 8*i;
#ifdef _BLE_TRACE_
Serial.println("Expected : 0");
Serial.print("Result : ");
Serial.println(result);
Serial.println();
#endif
}
void BluetoothCryptoToolbox::AES_CMAC ( unsigned char *key, unsigned char *input, int length,
unsigned char *mac )
{
unsigned char X[16],Y[16], M_last[16], padded[16];
unsigned char K1[16], K2[16];
int n, i, flag;
generateSubkey(key,K1,K2);
n = (length+15) / 16; /* n is number of rounds */
if ( n == 0 ) {
n = 1;
flag = 0;
} else {
if ( (length%16) == 0 ) { /* last block is a complete block */
flag = 1;
} else { /* last block is not complete block */
flag = 0;
}
}
if ( flag ) { /* last block is complete block */
xor_128(&input[16*(n-1)],K1,M_last);
} else {
padding(&input[16*(n-1)],padded,length%16);
xor_128(padded,K2,M_last);
}
for ( i=0; i<16; i++ ) X[i] = 0;
for ( i=0; i<n-1; i++ ) {
xor_128(X,&input[16*i],Y); /* Y := Mi (+) X */
AES_128(key,Y,X); /* X := AES-128(KEY, Y); */
}
xor_128(X,M_last,Y);
AES_128(key,Y,X);
for ( i=0; i<16; i++ ) {
mac[i] = X[i];
}
}
// Paddinng function from RFC
void BluetoothCryptoToolbox::padding( unsigned char *lastb, unsigned char *pad, int length )
{
int j;
/* original last block */
for ( j=0; j<16; j++ ) {
if ( j < length ) {
pad[j] = lastb[j];
} else if ( j == length ) {
pad[j] = 0x80;
} else {
pad[j] = 0x00;
}
}
}
// Generate subkey from RFC
void BluetoothCryptoToolbox::generateSubkey(uint8_t* key, uint8_t* K1, uint8_t* K2){
unsigned char L[16];
unsigned char Z[16];
unsigned char tmp[16];
int i;
for ( i=0; i<16; i++ ) Z[i] = 0;
AES_128(key,Z,L);
if ( (L[0] & 0x80) == 0 ) { /* If MSB(L) = 0, then K1 = L << 1 */
leftshift_onebit(L,K1);
} else { /* Else K1 = ( L << 1 ) (+) Rb */
leftshift_onebit(L,tmp);
xor_128(tmp,const_Rb,K1);
}
if ( (K1[0] & 0x80) == 0 ) {
leftshift_onebit(K1,K2);
} else {
leftshift_onebit(K1,tmp);
xor_128(tmp,const_Rb,K2);
}
return;
}
// Use BLE AES function - restart bluetooth if crash
int BluetoothCryptoToolbox::AES_128(uint8_t* key, uint8_t* data_in, uint8_t* data_out){
uint8_t status = 0;
int n = 0;
int tries = 30;
while(HCI.leEncrypt(key,data_in, &status, data_out)!=1&&n<tries){
#ifdef _BLE_TRACE_
Serial.print("AES failed... retrying: ");
Serial.println(n);
#endif
BLE.end();
delay(200);
BLE.begin();
n++;
delay(100*n);
}
if(n==tries){
#ifdef _BLE_TRACE_
Serial.println("something went wrong with AES.");
#endif
return 0;
}
return 1;
}
// Tests AES CMAC
#ifdef _BLE_TRACE_
void BluetoothCryptoToolbox::test(){
unsigned char L[16];
unsigned char Z[16];
unsigned char tmp[16];
int i;
for ( i=0; i<16; i++ ) Z[i] = 0x00;
uint8_t k[16] = {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c};
Serial.println("AES Plaintext:");
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(Z[i],HEX);
}
Serial.println(".");
uint8_t expected_aes[16] = {0x7d, 0xf7, 0x6b, 0x0c, 0x1a, 0xb8, 0x99, 0xb3, 0x3e, 0x42, 0xf0, 0x47, 0xb9, 0x1b, 0x54, 0x6f};
AES_128(k, Z, L);
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(L[i],HEX);
}
Serial.println(".");
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(expected_aes[i],HEX);
}
Serial.println(".");
uint8_t k1[16];
uint8_t k2[16];
generateSubkey(k,k1,k2);
uint8_t expected_k1[16] = {0xfb, 0xee, 0xd6, 0x18, 0x35, 0x71, 0x33, 0x66, 0x7c, 0x85, 0xe0, 0x8f, 0x72, 0x36, 0xa8, 0xde};
uint8_t expected_k2[16] = {0xf7, 0xdd, 0xac, 0x30, 0x6a, 0xe2, 0x66, 0xcc, 0xf9, 0x0b, 0xc1, 0x1e, 0xe4, 0x6d, 0x51, 0x3b};
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(k2[i],HEX);
}
Serial.println(".");
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(expected_k2[i],HEX);
}
Serial.println(".");
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(k1[i],HEX);
}
Serial.println(".");
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(expected_k1[i],HEX);
}
Serial.println(".");
uint8_t m[40] = {0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a, 0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51, 0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11};
uint8_t mac[16];
uint8_t expected_mac[16] = {0xdf, 0xa6, 0x67, 0x47, 0xde, 0x9a, 0xe6, 0x30, 0x30, 0xca, 0x32, 0x61, 0x14, 0x97, 0xc8, 0x27};
AES_CMAC(k,m,40,mac);
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(mac[i],HEX);
}
Serial.println(".");
for(int i=0; i<16; i++){
Serial.print(" 0x");
Serial.print(expected_mac[i],HEX);
}
Serial.println(".");
}
#endif //_BLE_TRACE_
// From RFC
void BluetoothCryptoToolbox::leftshift_onebit(unsigned char *input,unsigned char *output)
{
int i;
unsigned char overflow = 0;
for ( i=15; i>=0; i-- ) {
output[i] = input[i] << 1;
output[i] |= overflow;
overflow = (input[i] & 0x80)?1:0;
}
return;
}
// From RFC
void BluetoothCryptoToolbox::xor_128(unsigned char *a, unsigned char *b, unsigned char *out)
{
int i;
for (i=0;i<16; i++)
{
out[i] = a[i] ^ b[i];
}
}
BluetoothCryptoToolbox btct;
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