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

   1 /*****************************************************************************
   2  * WARNING
   3  *
   4  * THIS CODE IS CREATED FOR EXPERIMENTATION AND EDUCATIONAL USE ONLY.
   5  *
   6  * USAGE OF THIS CODE IN OTHER WAYS MAY INFRINGE UPON THE INTELLECTUAL
   7  * PROPERTY OF OTHER PARTIES, SUCH AS INSIDE SECURE AND HID GLOBAL,
   8  * AND MAY EXPOSE YOU TO AN INFRINGEMENT ACTION FROM THOSE PARTIES.
   9  *
  10  * THIS CODE SHOULD NEVER BE USED TO INFRINGE PATENTS OR INTELLECTUAL PROPERTY RIGHTS.
  11  *
  12  *****************************************************************************
  13  *
  14  * This file is part of loclass. It is a reconstructon of the cipher engine
  15  * used in iClass, and RFID techology.
  16  *
  17  * The implementation is based on the work performed by
  18  * Flavio D. Garcia, Gerhard de Koning Gans, Roel Verdult and
  19  * Milosch Meriac in the paper "Dismantling IClass".
  20  *
  21  * Copyright (C) 2014 Martin Holst Swende
  22  *
  23  * This is free software: you can redistribute it and/or modify
  24  * it under the terms of the GNU General Public License version 2 as published
  25  * by the Free Software Foundation.
  26  *
  27  * This file is distributed in the hope that it will be useful,
  28  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  29  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  30  * GNU General Public License for more details.
  31  *
  32  * You should have received a copy of the GNU General Public License
  33  * along with IClassCipher.  If not, see <http://www.gnu.org/licenses/>.
  34  ****************************************************************************/
  35
  36 #include "cipher.h"
  37 #include "cipherutils.h"
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41 #include <stdbool.h>
  42 #include <stdint.h>
  43 #include <time.h>
  44 #include "fileutils.h"
  45 uint8_t keytable[] = { 0,0,0,0,0,0,0,0};
  46
  47 /**
  48 * Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
  49 * consisting of the following four components:
  50 *       1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
  51 *       2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
  52 *       3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
  53 *       4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
  54 **/
  55 typedef struct {
  56         uint8_t l;
  57         uint8_t r;
  58         uint8_t b;
  59         uint16_t t;
  60 } State;
  61
  62 /**
  63 *       Definition 2. The feedback function for the top register T : F 16/2 → F 2
  64 *       is defined as
  65 *       T (x 0 x 1 . . . . . . x 15 ) = x 0 ⊕ x 1 ⊕ x 5 ⊕ x 7 ⊕ x 10 ⊕ x 11 ⊕ x 14 ⊕ x 15 .
  66 **/
  67 bool T(State state)
  68 {
  69         bool x0 = state.t & 0x8000;
  70         bool x1 = state.t & 0x4000;
  71         bool x5 = state.t & 0x0400;
  72         bool x7 = state.t & 0x0100;
  73         bool x10 = state.t & 0x0020;
  74         bool x11 = state.t & 0x0010;
  75         bool x14 = state.t & 0x0002;
  76         bool x15 = state.t & 0x0001;
  77         return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
  78 }
  79 /**
  80 *       Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
  81 *       B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
  82 **/
  83 bool B(State state)
  84 {
  85         bool x1 = state.b & 0x40;
  86         bool x2 = state.b & 0x20;
  87         bool x3 = state.b & 0x10;
  88         bool x7 = state.b & 0x01;
  89
  90         return x1 ^ x2 ^ x3 ^ x7;
  91
  92 }
  93
  94
  95 /**
  96 *       Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
  97 *       F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
  98 *       z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
  99 *       z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
 100 *       z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
 101 **/
 102 uint8_t _select(bool x, bool y, uint8_t r)
 103 {
 104         bool r0 = r >> 7 & 0x1;
 105         bool r1 = r >> 6 & 0x1;
 106         bool r2 = r >> 5 & 0x1;
 107         bool r3 = r >> 4 & 0x1;
 108         bool r4 = r >> 3 & 0x1;
 109         bool r5 = r >> 2 & 0x1;
 110         bool r6 = r >> 1 & 0x1;
 111         bool r7 = r & 0x1;
 112
 113         bool z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4);
 114         bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
 115         bool z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x;
 116
 117         // The three bitz z0.. z1 are packed into a uint8_t:
 118         // 00000ZZZ
 119         //Return value is a uint8_t
 120         uint8_t retval = 0;
 121         retval |= (z0 << 2) & 4;
 122         retval |= (z1 << 1) & 2;
 123         retval |= z2 & 1;
 124
 125         // Return value 0 <= retval <= 7
 126         return retval;
 127 }
 128
 129 /**
 130 *       Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
 131 *       be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
 132 *       l ′ , r ′ , t ′ , b ′ is defined as
 133 *       t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
 134 *       b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
 135 *
 136 * @param s - state
 137 * @param k - array containing 8 bytes
 138 **/
 139 State successor(uint8_t* k, State s, bool y)
 140 {
 141         bool r0 = s.r >> 7 & 0x1;
 142         bool r4 = s.r >> 3 & 0x1;
 143         bool r7 = s.r & 0x1;
 144
 145         State successor = {0,0,0,0};
 146
 147         successor.t = s.t >> 1;
 148         successor.t |= (T(s) ^ r0 ^ r4) << 15;
 149
 150         successor.b = s.b >> 1;
 151         successor.b |= (B(s) ^ r7) << 7;
 152
 153         bool Tt = T(s);
 154
 155         successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
 156         successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
 157
 158         return successor;
 159 }
 160 /**
 161 *       We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
 162 *       an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
 163 *       to multiple bit input x ∈ F n 2 which we define as
 164 * @param k - array containing 8 bytes
 165 **/
 166 State suc(uint8_t* k,State s, BitstreamIn *bitstream)
 167 {
 168         if(bitsLeft(bitstream) == 0)
 169         {
 170                 return s;
 171         }
 172         bool lastbit = tailBit(bitstream);
 173         return successor(k,suc(k,s,bitstream), lastbit);
 174 }
 175
 176 /**
 177 *       Definition 5 (Output). Define the function output which takes an internal
 178 *       state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
 179 *       on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
 180 *       output(k, s, ǫ) = ǫ
 181 *       output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
 182 *       where s ′ = suc(k, s, x 0 ).
 183 **/
 184 void output(uint8_t* k,State s, BitstreamIn* in,  BitstreamOut* out)
 185 {
 186         if(bitsLeft(in) == 0)
 187         {
 188                 return;
 189         }
 190         pushBit(out,(s.r >> 2) & 1);
 191         //Remove first bit
 192         uint8_t x0 = headBit(in);
 193         State ss = successor(k,s,x0);
 194         output(k,ss,in, out);
 195 }
 196
 197 /**
 198 * Definition 6 (Initial state). Define the function init which takes as input a
 199 * key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
 200 **/
 201
 202 State init(uint8_t* k)
 203 {
 204         State s = {
 205         ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
 206         ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
 207         0x4c, // b
 208         0xE012 // t
 209         };
 210         return s;
 211 }
 212 void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
 213 {
 214         uint8_t zeroes_32[] = {0,0,0,0};
 215         BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
 216         State initState = suc(k,init(k),&input);
 217         output(k,initState,&input_32_zeroes,&out);
 218 }
 219
 220 void doMAC(uint8_t *cc_nr_p, int length, uint8_t *div_key_p, uint8_t mac[4])
 221 {
 222     uint8_t *cc_nr;
 223     uint8_t div_key[8];
 224     cc_nr=(uint8_t*)malloc(length+1);
 225     memcpy(cc_nr,cc_nr_p,length);
 226     memcpy(div_key,div_key_p,8);
 227
 228         reverse_arraybytes(cc_nr,length);
 229         BitstreamIn bitstream = {cc_nr,length * 8,0};
 230         uint8_t dest []= {0,0,0,0,0,0,0,0};
 231         BitstreamOut out = { dest, sizeof(dest)*8, 0 };
 232         MAC(div_key,bitstream, out);
 233         //The output MAC must also be reversed
 234         reverse_arraybytes(dest, sizeof(dest));
 235         memcpy(mac,dest,4);
 236     //printf("Calculated_MAC\t%02x%02x%02x%02x\n", dest[0],dest[1],dest[2],dest[3]);
 237         free(cc_nr);
 238     return;
 239 }
 240
 241 int testMAC()
 242 {
 243         prnlog("[+] Testing MAC calculation...");
 244
 245         //From the "dismantling.IClass" paper:
 246         uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
 247         //From the paper
 248         uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
 249         uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA};
 250
 251         uint8_t calculated_mac[4] = {0};
 252     doMAC(cc_nr, 12,div_key, calculated_mac);
 253
 254         if(memcmp(calculated_mac, correct_MAC,4) == 0)
 255         {
 256                 prnlog("[+] MAC calculation OK!");
 257
 258         }else
 259         {
 260                 prnlog("[+] FAILED: MAC calculation failed:");
 261                 printarr("    Calculated_MAC", calculated_mac, 4);
 262                 printarr("    Correct_MAC   ", correct_MAC, 4);
 263         return 1;
 264 }
 265
 266         return 0;
 267 }