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 "cipher.h"
  25 #include "cipherutils.h"
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <stdbool.h>
  30 #include <stdint.h>
  31 #include <time.h>
  32 #include "fileutils.h"
  33 uint8_t keytable[] = { 0,0,0,0,0,0,0,0};
  34
  35 /**
  36 * Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
  37 * consisting of the following four components:
  38 *       1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
  39 *       2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
  40 *       3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
  41 *       4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
  42 **/
  43 typedef struct {
  44         uint8_t l;
  45         uint8_t r;
  46         uint8_t b;
  47         uint16_t t;
  48 } State;
  49
  50 /**
  51 *       Definition 2. The feedback function for the top register T : F 16/2 → F 2
  52 *       is defined as
  53 *       T (x 0 x 1 . . . . . . x 15 ) = x 0 ⊕ x 1 ⊕ x 5 ⊕ x 7 ⊕ x 10 ⊕ x 11 ⊕ x 14 ⊕ x 15 .
  54 **/
  55 bool T(State state)
  56 {
  57         bool x0 = state.t & 0x8000;
  58         bool x1 = state.t & 0x4000;
  59         bool x5 = state.t & 0x0400;
  60         bool x7 = state.t & 0x0100;
  61         bool x10 = state.t & 0x0020;
  62         bool x11 = state.t & 0x0010;
  63         bool x14 = state.t & 0x0002;
  64         bool x15 = state.t & 0x0001;
  65         return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
  66 }
  67 /**
  68 *       Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
  69 *       B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
  70 **/
  71 bool B(State state)
  72 {
  73         bool x1 = state.b & 0x40;
  74         bool x2 = state.b & 0x20;
  75         bool x3 = state.b & 0x10;
  76         bool x7 = state.b & 0x01;
  77
  78         return x1 ^ x2 ^ x3 ^ x7;
  79
  80 }
  81
  82
  83 /**
  84 *       Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
  85 *       F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
  86 *       z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
  87 *       z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
  88 *       z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
  89 **/
  90 uint8_t _select(bool x, bool y, uint8_t r)
  91 {
  92         bool r0 = r >> 7 & 0x1;
  93         bool r1 = r >> 6 & 0x1;
  94         bool r2 = r >> 5 & 0x1;
  95         bool r3 = r >> 4 & 0x1;
  96         bool r4 = r >> 3 & 0x1;
  97         bool r5 = r >> 2 & 0x1;
  98         bool r6 = r >> 1 & 0x1;
  99         bool r7 = r & 0x1;
 100
 101         bool z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4);
 102         bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
 103         bool z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x;
 104
 105         // The three bitz z0.. z1 are packed into a uint8_t:
 106         // 00000ZZZ
 107         //Return value is a uint8_t
 108         uint8_t retval = 0;
 109         retval |= (z0 << 2) & 4;
 110         retval |= (z1 << 1) & 2;
 111         retval |= z2 & 1;
 112
 113         // Return value 0 <= retval <= 7
 114         return retval;
 115 }
 116
 117 /**
 118 *       Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
 119 *       be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
 120 *       l ′ , r ′ , t ′ , b ′ is defined as
 121 *       t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
 122 *       b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
 123 *
 124 * @param s - state
 125 * @param k - array containing 8 bytes
 126 **/
 127 State successor(uint8_t* k, State s, bool y)
 128 {
 129         bool r0 = s.r >> 7 & 0x1;
 130         bool r4 = s.r >> 3 & 0x1;
 131         bool r7 = s.r & 0x1;
 132
 133         State successor = {0,0,0,0};
 134
 135         successor.t = s.t >> 1;
 136         successor.t |= (T(s) ^ r0 ^ r4) << 15;
 137
 138         successor.b = s.b >> 1;
 139         successor.b |= (B(s) ^ r7) << 7;
 140
 141         bool Tt = T(s);
 142
 143         successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
 144         successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
 145
 146         return successor;
 147 }
 148 /**
 149 *       We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
 150 *       an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
 151 *       to multiple bit input x ∈ F n 2 which we define as
 152 * @param k - array containing 8 bytes
 153 **/
 154 State suc(uint8_t* k,State s, BitstreamIn *bitstream)
 155 {
 156         if(bitsLeft(bitstream) == 0)
 157         {
 158                 return s;
 159         }
 160         bool lastbit = tailBit(bitstream);
 161         return successor(k,suc(k,s,bitstream), lastbit);
 162 }
 163
 164 /**
 165 *       Definition 5 (Output). Define the function output which takes an internal
 166 *       state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
 167 *       on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
 168 *       output(k, s, ǫ) = ǫ
 169 *       output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
 170 *       where s ′ = suc(k, s, x 0 ).
 171 **/
 172 void output(uint8_t* k,State s, BitstreamIn* in,  BitstreamOut* out)
 173 {
 174         if(bitsLeft(in) == 0)
 175         {
 176                 return;
 177         }
 178         pushBit(out,(s.r >> 2) & 1);
 179         //Remove first bit
 180         uint8_t x0 = headBit(in);
 181         State ss = successor(k,s,x0);
 182         output(k,ss,in, out);
 183 }
 184
 185 /**
 186 * Definition 6 (Initial state). Define the function init which takes as input a
 187 * key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
 188 **/
 189
 190 State init(uint8_t* k)
 191 {
 192         State s = {
 193         ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
 194         ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
 195         0x4c, // b
 196         0xE012 // t
 197         };
 198         return s;
 199 }
 200 void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
 201 {
 202         uint8_t zeroes_32[] = {0,0,0,0};
 203         BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
 204         State initState = suc(k,init(k),&input);
 205         output(k,initState,&input_32_zeroes,&out);
 206 }
 207
 208 void doMAC(uint8_t *cc_nr_p, int length, uint8_t *div_key_p, uint8_t mac[4])
 209 {
 210     uint8_t *cc_nr;
 211     uint8_t div_key[8];
 212     cc_nr=(uint8_t*)malloc(length+1);
 213     memcpy(cc_nr,cc_nr_p,length);
 214     memcpy(div_key,div_key_p,8);
 215
 216     reverse_arraybytes(cc_nr,length);
 217     BitstreamIn bitstream = {cc_nr,length * 8,0};
 218     uint8_t dest []= {0,0,0,0,0,0,0,0};
 219     BitstreamOut out = { dest, sizeof(dest)*8, 0 };
 220     MAC(div_key,bitstream, out);
 221     //The output MAC must also be reversed
 222     reverse_arraybytes(dest, sizeof(dest));
 223     memcpy(mac, dest, 4);
 224     //printf("Calculated_MAC\t%02x%02x%02x%02x\n", dest[0],dest[1],dest[2],dest[3]);
 225     free(cc_nr);
 226     return;
 227 }
 228
 229 int testMAC()
 230 {
 231         prnlog("[+] Testing MAC calculation...");
 232
 233         //From the "dismantling.IClass" paper:
 234         uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
 235         //From the paper
 236         uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
 237         uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA};
 238
 239         uint8_t calculated_mac[4] = {0};
 240     doMAC(cc_nr, 12,div_key, calculated_mac);
 241
 242         if(memcmp(calculated_mac, correct_MAC,4) == 0)
 243         {
 244                 prnlog("[+] MAC calculation OK!");
 245
 246         }else
 247         {
 248                 prnlog("[+] FAILED: MAC calculation failed:");
 249                 printarr("    Calculated_MAC", calculated_mac, 4);
 250                 printarr("    Correct_MAC   ", correct_MAC, 4);
 251                 return 1;
 252         }
 253
 254         return 0;
 255 }