proxmark3/client/loclass/cipher.c

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/*****************************************************************************
* WARNING
*
* THIS CODE IS CREATED FOR EXPERIMENTATION AND EDUCATIONAL USE ONLY.
*
* USAGE OF THIS CODE IN OTHER WAYS MAY INFRINGE UPON THE INTELLECTUAL
* PROPERTY OF OTHER PARTIES, SUCH AS INSIDE SECURE AND HID GLOBAL,
* AND MAY EXPOSE YOU TO AN INFRINGEMENT ACTION FROM THOSE PARTIES.
*
* THIS CODE SHOULD NEVER BE USED TO INFRINGE PATENTS OR INTELLECTUAL PROPERTY RIGHTS.
*
*****************************************************************************
*
* This file is part of loclass. It is a reconstructon of the cipher engine
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* used in iClass, and RFID techology.
*
* The implementation is based on the work performed by
* Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
* Milosch Meriac in the paper "Dismantling IClass".
*
* Copyright (C) 2014 Martin Holst Swende
*
* This is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as published
* by the Free Software Foundation, or, at your option, any later version.
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*
* This file is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with loclass. If not, see <http://www.gnu.org/licenses/>.
*
*
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****************************************************************************/
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#include "cipher.h"
#include "cipherutils.h"
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <stdint.h>
#ifndef ON_DEVICE
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#include "fileutils.h"
#endif
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/**
* Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
* consisting of the following four components:
* 1. the left register l = (l 0 . . . l 7 ) F 8/2 ;
* 2. the right register r = (r 0 . . . r 7 ) F 8/2 ;
* 3. the top register t = (t 0 . . . t 15 ) F 16/2 .
* 4. the bottom register b = (b 0 . . . b 7 ) F 8/2 .
**/
typedef struct {
uint8_t l;
uint8_t r;
uint8_t b;
uint16_t t;
} State;
/**
* Definition 2. The feedback function for the top register T : F 16/2 F 2
* is defined as
* T (x 0 x 1 . . . . . . x 15 ) = x 0 x 1 x 5 x 7 x 10 x 11 x 14 x 15 .
**/
bool T(State state)
{
bool x0 = state.t & 0x8000;
bool x1 = state.t & 0x4000;
bool x5 = state.t & 0x0400;
bool x7 = state.t & 0x0100;
bool x10 = state.t & 0x0020;
bool x11 = state.t & 0x0010;
bool x14 = state.t & 0x0002;
bool x15 = state.t & 0x0001;
return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
}
/**
* Similarly, the feedback function for the bottom register B : F 8/2 F 2 is defined as
* B(x 0 x 1 . . . x 7 ) = x 1 x 2 x 3 x 7 .
**/
bool B(State state)
{
bool x1 = state.b & 0x40;
bool x2 = state.b & 0x20;
bool x3 = state.b & 0x10;
bool x7 = state.b & 0x01;
return x1 ^ x2 ^ x3 ^ x7;
}
/**
* Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
* F 8/2 F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
* z 0 = (r 0 r 2 ) (r 1 r 3 ) (r 2 r 4 )
* z 1 = (r 0 r 2 ) (r 5 r 7 ) r 1 r 6 x y
* z 2 = (r 3 r 5 ) (r 4 r 6 ) r 7 x
**/
uint8_t _select(bool x, bool y, uint8_t r)
{
bool r0 = r >> 7 & 0x1;
bool r1 = r >> 6 & 0x1;
bool r2 = r >> 5 & 0x1;
bool r3 = r >> 4 & 0x1;
bool r4 = r >> 3 & 0x1;
bool r5 = r >> 2 & 0x1;
bool r6 = r >> 1 & 0x1;
bool r7 = r & 0x1;
bool z0 = (r0 & r2) ^ (r1 & !r3) ^ (r2 | r4);
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bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
bool z2 = (r3 & !r5) ^ (r4 & r6 ) ^ r7 ^ x;
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// The three bitz z0.. z1 are packed into a uint8_t:
// 00000ZZZ
//Return value is a uint8_t
uint8_t retval = 0;
retval |= (z0 << 2) & 4;
retval |= (z1 << 1) & 2;
retval |= z2 & 1;
// Return value 0 <= retval <= 7
return retval;
}
/**
* Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k (F 82 ) 8
* be a key and y F 2 be the input bit. Then, the successor cipher state s =
* l , r , t , b is defined as
* t := (T (t) r 0 r 4 )t 0 . . . t 14 l := (k [select(T (t),y,r)] b ) l r
* b := (B(b) r 7 )b 0 . . . b 6 r := (k [select(T (t),y,r)] b ) l
*
* @param s - state
* @param k - array containing 8 bytes
**/
State successor(uint8_t* k, State s, bool y)
{
bool r0 = s.r >> 7 & 0x1;
bool r4 = s.r >> 3 & 0x1;
bool r7 = s.r & 0x1;
State successor = {0,0,0,0};
successor.t = s.t >> 1;
successor.t |= (T(s) ^ r0 ^ r4) << 15;
successor.b = s.b >> 1;
successor.b |= (B(s) ^ r7) << 7;
bool Tt = T(s);
successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
return successor;
}
/**
* We define the successor function suc which takes a key k (F 82 ) 8 , a state s and
* an input y F 2 and outputs the successor state s . We overload the function suc
* to multiple bit input x F n 2 which we define as
* @param k - array containing 8 bytes
**/
State suc(uint8_t* k,State s, BitstreamIn *bitstream)
{
if(bitsLeft(bitstream) == 0)
{
return s;
}
bool lastbit = tailBit(bitstream);
return successor(k,suc(k,s,bitstream), lastbit);
}
/**
* Definition 5 (Output). Define the function output which takes an internal
* state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
* on multiple bits input which takes a key k, a state s and an input x F n 2 as
* output(k, s, ǫ) = ǫ
* output(k, s, x 0 . . . x n ) = output(s) · output(k, s , x 1 . . . x n )
* where s = suc(k, s, x 0 ).
**/
void output(uint8_t* k,State s, BitstreamIn* in, BitstreamOut* out)
{
if(bitsLeft(in) == 0)
{
return;
}
pushBit(out,(s.r >> 2) & 1);
//Remove first bit
uint8_t x0 = headBit(in);
State ss = successor(k,s,x0);
output(k,ss,in, out);
}
/**
* Definition 6 (Initial state). Define the function init which takes as input a
* key k (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
**/
State init(uint8_t* k)
{
State s = {
((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
0x4c, // b
0xE012 // t
};
return s;
}
void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
{
uint8_t zeroes_32[] = {0,0,0,0};
BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
State initState = suc(k,init(k),&input);
output(k,initState,&input_32_zeroes,&out);
}
void doMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
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{
uint8_t cc_nr[13] = { 0 };
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uint8_t div_key[8];
//cc_nr=(uint8_t*)malloc(length+1);
memcpy(cc_nr, cc_nr_p, 12);
memcpy(div_key, div_key_p, 8);
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reverse_arraybytes(cc_nr, 12);
BitstreamIn bitstream = {cc_nr, 12 * 8, 0};
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uint8_t dest []= {0,0,0,0,0,0,0,0};
BitstreamOut out = { dest, sizeof(dest)*8, 0 };
MAC(div_key,bitstream, out);
//The output MAC must also be reversed
reverse_arraybytes(dest, sizeof(dest));
memcpy(mac, dest, 4);
//free(cc_nr);
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return;
}
void doMAC_N(uint8_t *address_data_p, uint8_t address_data_size, uint8_t *div_key_p, uint8_t mac[4])
{
uint8_t *address_data;
uint8_t div_key[8];
address_data = (uint8_t*) malloc(address_data_size);
memcpy(address_data, address_data_p, address_data_size);
memcpy(div_key, div_key_p, 8);
reverse_arraybytes(address_data, address_data_size);
BitstreamIn bitstream = {address_data, address_data_size * 8, 0};
uint8_t dest []= {0,0,0,0,0,0,0,0};
BitstreamOut out = { dest, sizeof(dest)*8, 0 };
MAC(div_key, bitstream, out);
//The output MAC must also be reversed
reverse_arraybytes(dest, sizeof(dest));
memcpy(mac, dest, 4);
free(address_data);
return;
}
#ifndef ON_DEVICE
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int testMAC()
{
PrintAndLogDevice(SUCCESS, "Testing MAC calculation...");
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//From the "dismantling.IClass" paper:
uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
//From the paper
uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA};
uint8_t calculated_mac[4] = {0};
doMAC(cc_nr,div_key, calculated_mac);
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if(memcmp(calculated_mac, correct_MAC,4) == 0)
{
PrintAndLogDevice(SUCCESS, "MAC calculation OK!");
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}else
{
PrintAndLogDevice(FAILED, "FAILED: MAC calculation failed:");
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printarr(" Calculated_MAC", calculated_mac, 4);
printarr(" Correct_MAC ", correct_MAC, 4);
return 1;
}
return 0;
}
#endif