git.zerfleddert.de Git - proxmark3-svn/blob - client/loclass/cipher.c

   1 /*****************************************************************************
   2  * This file is part of iClassCipher. It is a reconstructon of the cipher engine
   3  * used in iClass, and RFID techology.
   4  *
   5  * The implementation is based on the work performed by
   6  * Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
   7  * Milosch Meriac in the paper "Dismantling IClass".
   8  *
   9  * Copyright (C) 2014 Martin Holst Swende
  10  *
  11  * This is free software: you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as published
  13  * by the Free Software Foundation.
  14  *
  15  * This file is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with IClassCipher.  If not, see <http://www.gnu.org/licenses/>.
  22  ****************************************************************************/
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <stdbool.h>
  28 #include <stdint.h>
  29 #include "loclass/cipher.h"
  30 #include "loclass/cipherutils.h"
  31 #include "loclass/ikeys.h"
  32
  33 uint8_t keytable[] = { 0,0,0,0,0,0,0,0};
  34
  35 /**
  36 *       Definition 2. The feedback function for the top register T : F 16/2 → F 2
  37 *       is defined as
  38 *       T (x 0 x 1 . . . . . . x 15 ) = x 0 ⊕ x 1 ⊕ x 5 ⊕ x 7 ⊕ x 10 ⊕ x 11 ⊕ x 14 ⊕ x 15 .
  39 **/
  40 bool T(State state)
  41 {
  42         bool x0 = state.t & 0x8000;
  43         bool x1 = state.t & 0x4000;
  44         bool x5 = state.t & 0x0400;
  45         bool x7 = state.t & 0x0100;
  46         bool x10 = state.t & 0x0020;
  47         bool x11 = state.t & 0x0010;
  48         bool x14 = state.t & 0x0002;
  49         bool x15 = state.t & 0x0001;
  50         return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
  51 }
  52 /**
  53 *       Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
  54 *       B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
  55 **/
  56 bool B(State state)
  57 {
  58         bool x1 = state.b & 0x40;
  59         bool x2 = state.b & 0x20;
  60         bool x3 = state.b & 0x10;
  61         bool x7 = state.b & 0x01;
  62
  63         return x1 ^ x2 ^ x3 ^ x7;
  64
  65 }
  66
  67
  68 /**
  69 *       Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
  70 *       F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
  71 *       z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
  72 *       z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
  73 *       z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
  74 **/
  75 uint8_t _select(bool x, bool y, uint8_t r)
  76 {
  77         bool r0 = r >> 7 & 0x1;
  78         bool r1 = r >> 6 & 0x1;
  79         bool r2 = r >> 5 & 0x1;
  80         bool r3 = r >> 4 & 0x1;
  81         bool r4 = r >> 3 & 0x1;
  82         bool r5 = r >> 2 & 0x1;
  83         bool r6 = r >> 1 & 0x1;
  84         bool r7 = r & 0x1;
  85
  86         bool z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4);
  87         bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
  88         bool z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x;
  89
  90         // The three bitz z0.. z1 are packed into a uint8_t:
  91         // 00000ZZZ
  92         //Return value is a uint8_t
  93         uint8_t retval = 0;
  94         retval |= (z0 << 2) & 4;
  95         retval |= (z1 << 1) & 2;
  96         retval |= z2 & 1;
  97
  98         // Return value 0 <= retval <= 7
  99         return retval;
 100 }
 101
 102 /**
 103 *       Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
 104 *       be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
 105 *       l ′ , r ′ , t ′ , b ′ is defined as
 106 *       t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
 107 *       b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
 108 *
 109 * @param s - state
 110 * @param k - array containing 8 bytes
 111 **/
 112 State successor(uint8_t* k, State s, bool y)
 113 {
 114         bool r0 = s.r >> 7 & 0x1;
 115         bool r4 = s.r >> 3 & 0x1;
 116         bool r7 = s.r & 0x1;
 117
 118         State successor = {0,0,0,0};
 119
 120         successor.t = s.t >> 1;
 121         successor.t |= (T(s) ^ r0 ^ r4) << 15;
 122
 123         successor.b = s.b >> 1;
 124         successor.b |= (B(s) ^ r7) << 7;
 125
 126         bool Tt = T(s);
 127
 128         successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
 129         successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
 130
 131         return successor;
 132 }
 133 /**
 134 *       We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
 135 *       an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
 136 *       to multiple bit input x ∈ F n 2 which we define as
 137 * @param k - array containing 8 bytes
 138 **/
 139 State suc(uint8_t* k,State s, BitstreamIn *bitstream)
 140 {
 141         if(bitsLeft(bitstream) == 0)
 142         {
 143                 return s;
 144         }
 145         bool lastbit = tailBit(bitstream);
 146         return successor(k,suc(k,s,bitstream), lastbit);
 147 }
 148
 149 /**
 150 *       Definition 5 (Output). Define the function output which takes an internal
 151 *       state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
 152 *       on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
 153 *       output(k, s, ǫ) = ǫ
 154 *       output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
 155 *       where s ′ = suc(k, s, x 0 ).
 156 **/
 157 void output(uint8_t* k,State s, BitstreamIn* in,  BitstreamOut* out)
 158 {
 159         if(bitsLeft(in) == 0)
 160         {
 161                 return;
 162         }
 163         //printf("bitsleft %d" , bitsLeft(in));
 164         //printf(" %0d", s.r >> 2 & 1);
 165         pushBit(out,(s.r >> 2) & 1);
 166         //Remove first bit
 167         uint8_t x0 = headBit(in);
 168         State ss = successor(k,s,x0);
 169         output(k,ss,in, out);
 170 }
 171
 172 /**
 173 * Definition 6 (Initial state). Define the function init which takes as input a
 174 * key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
 175 **/
 176
 177 State init(uint8_t* k)
 178 {
 179         State s = {
 180         ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
 181         ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
 182         0x4c, // b
 183         0xE012 // t
 184         };
 185         return s;
 186 }
 187 void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
 188 {
 189         uint8_t zeroes_32[] = {0,0,0,0};
 190         BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
 191         State initState = suc(k,init(k),&input);
 192         output(k,initState,&input_32_zeroes,&out);
 193
 194 }
 195
 196
 197 void printarr(char * name, uint8_t* arr, int len)
 198 {
 199         int i ;
 200         printf("uint8_t %s[] = {", name);
 201         for(i =0 ;  i< len ; i++)
 202         {
 203                 printf("0x%02x,",*(arr+i));
 204         }
 205         printf("};\n");
 206 }
 207
 208 int testMAC()
 209 {
 210
 211         //From the "dismantling.IClass" paper:
 212         uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
 213         // But actually, that must be reversed, it's "on-the-wire" data
 214         reverse_arraybytes(cc_nr,sizeof(cc_nr));
 215
 216         //From the paper
 217         uint8_t div_key[] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
 218         uint8_t correct_MAC[] = {0x1d,0x49,0xC9,0xDA};
 219
 220         BitstreamIn bitstream = {cc_nr,sizeof(cc_nr) * 8,0};
 221         uint8_t dest []= {0,0,0,0,0,0,0,0};
 222         BitstreamOut out = { dest, sizeof(dest)*8, 0 };
 223         MAC(div_key,bitstream, out);
 224         //The output MAC must also be reversed
 225         reverse_arraybytes(dest, sizeof(dest));
 226
 227         if(false && memcmp(dest, correct_MAC,4) == 0)
 228         {
 229                 printf("MAC calculation OK!\n");
 230
 231         }else
 232         {
 233                 printf("MAC calculation failed\n");
 234                 printarr("Calculated_MAC", dest, 4);
 235                 printarr("Correct_MAC   ", correct_MAC, 4);
 236                 return 1;
 237         }
 238         return 0;
 239 }
 240
 241 int calc_iclass_mac(uint8_t *cc_nr_p, int length, uint8_t *div_key_p, uint8_t *mac)
 242 {
 243     uint8_t *cc_nr;
 244     uint8_t div_key[8];
 245     cc_nr=(uint8_t*)malloc(length+1);
 246     memcpy(cc_nr,cc_nr_p,length);
 247     memcpy(div_key,div_key_p,8);
 248
 249         reverse_arraybytes(cc_nr,length);
 250         BitstreamIn bitstream = {cc_nr,length * 8,0};
 251         uint8_t dest []= {0,0,0,0,0,0,0,0};
 252         BitstreamOut out = { dest, sizeof(dest)*8, 0 };
 253         MAC(div_key,bitstream, out);
 254         //The output MAC must also be reversed
 255         reverse_arraybytes(dest, sizeof(dest));
 256
 257         printf("Calculated_MAC\t%02x%02x%02x%02x\n", dest[0],dest[1],dest[2],dest[3]);
 258         memcpy(mac,dest,4);
 259         free(cc_nr);
 260         return 1;
 261 }