git.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 loclass.  If not, see <http://www.gnu.org/licenses/>.
  34  *
  35  *
  36  *
  37  ****************************************************************************/
  38
  39
  40 #include "cipher.h"
  41 #include "cipherutils.h"
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <stdbool.h>
  45 #include <stdint.h>
  46 #ifndef ON_DEVICE
  47 #include "fileutils.h"
  48 #endif
  49
  50
  51 /**
  52 * Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
  53 * consisting of the following four components:
  54 *       1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
  55 *       2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
  56 *       3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
  57 *       4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
  58 **/
  59 typedef struct {
  60         uint8_t l;
  61         uint8_t r;
  62         uint8_t b;
  63         uint16_t t;
  64 } State;
  65
  66 /**
  67 *       Definition 2. The feedback function for the top register T : F 16/2 → F 2
  68 *       is defined as
  69 *       T (x 0 x 1 . . . . . . x 15 ) = x 0 ⊕ x 1 ⊕ x 5 ⊕ x 7 ⊕ x 10 ⊕ x 11 ⊕ x 14 ⊕ x 15 .
  70 **/
  71 bool T(State state)
  72 {
  73         bool x0 = state.t & 0x8000;
  74         bool x1 = state.t & 0x4000;
  75         bool x5 = state.t & 0x0400;
  76         bool x7 = state.t & 0x0100;
  77         bool x10 = state.t & 0x0020;
  78         bool x11 = state.t & 0x0010;
  79         bool x14 = state.t & 0x0002;
  80         bool x15 = state.t & 0x0001;
  81         return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
  82 }
  83 /**
  84 *       Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
  85 *       B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
  86 **/
  87 bool B(State state)
  88 {
  89         bool x1 = state.b & 0x40;
  90         bool x2 = state.b & 0x20;
  91         bool x3 = state.b & 0x10;
  92         bool x7 = state.b & 0x01;
  93
  94         return x1 ^ x2 ^ x3 ^ x7;
  95
  96 }
  97
  98
  99 /**
 100 *       Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
 101 *       F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
 102 *       z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
 103 *       z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
 104 *       z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
 105 **/
 106 uint8_t _select(bool x, bool y, uint8_t r)
 107 {
 108         bool r0 = r >> 7 & 0x1;
 109         bool r1 = r >> 6 & 0x1;
 110         bool r2 = r >> 5 & 0x1;
 111         bool r3 = r >> 4 & 0x1;
 112         bool r4 = r >> 3 & 0x1;
 113         bool r5 = r >> 2 & 0x1;
 114         bool r6 = r >> 1 & 0x1;
 115         bool r7 = r & 0x1;
 116
 117         bool z0 = (r0 & r2) ^ (r1 & ~r3) ^ (r2 | r4);
 118         bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
 119         bool z2 = (r3 & ~r5) ^ (r4 & r6 ) ^ r7 ^ x;
 120
 121         // The three bitz z0.. z1 are packed into a uint8_t:
 122         // 00000ZZZ
 123         //Return value is a uint8_t
 124         uint8_t retval = 0;
 125         retval |= (z0 << 2) & 4;
 126         retval |= (z1 << 1) & 2;
 127         retval |= z2 & 1;
 128
 129         // Return value 0 <= retval <= 7
 130         return retval;
 131 }
 132
 133 /**
 134 *       Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
 135 *       be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
 136 *       l ′ , r ′ , t ′ , b ′ is defined as
 137 *       t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
 138 *       b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
 139 *
 140 * @param s - state
 141 * @param k - array containing 8 bytes
 142 **/
 143 State successor(uint8_t* k, State s, bool y)
 144 {
 145         bool r0 = s.r >> 7 & 0x1;
 146         bool r4 = s.r >> 3 & 0x1;
 147         bool r7 = s.r & 0x1;
 148
 149         State successor = {0,0,0,0};
 150
 151         successor.t = s.t >> 1;
 152         successor.t |= (T(s) ^ r0 ^ r4) << 15;
 153
 154         successor.b = s.b >> 1;
 155         successor.b |= (B(s) ^ r7) << 7;
 156
 157         bool Tt = T(s);
 158
 159         successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
 160         successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
 161
 162         return successor;
 163 }
 164 /**
 165 *       We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
 166 *       an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
 167 *       to multiple bit input x ∈ F n 2 which we define as
 168 * @param k - array containing 8 bytes
 169 **/
 170 State suc(uint8_t* k,State s, BitstreamIn *bitstream)
 171 {
 172         if(bitsLeft(bitstream) == 0)
 173         {
 174                 return s;
 175         }
 176         bool lastbit = tailBit(bitstream);
 177         return successor(k,suc(k,s,bitstream), lastbit);
 178 }
 179
 180 /**
 181 *       Definition 5 (Output). Define the function output which takes an internal
 182 *       state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
 183 *       on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
 184 *       output(k, s, ǫ) = ǫ
 185 *       output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
 186 *       where s ′ = suc(k, s, x 0 ).
 187 **/
 188 void output(uint8_t* k,State s, BitstreamIn* in,  BitstreamOut* out)
 189 {
 190         if(bitsLeft(in) == 0)
 191         {
 192                 return;
 193         }
 194         pushBit(out,(s.r >> 2) & 1);
 195         //Remove first bit
 196         uint8_t x0 = headBit(in);
 197         State ss = successor(k,s,x0);
 198         output(k,ss,in, out);
 199 }
 200
 201 /**
 202 * Definition 6 (Initial state). Define the function init which takes as input a
 203 * key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
 204 **/
 205
 206 State init(uint8_t* k)
 207 {
 208         State s = {
 209         ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
 210         ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
 211         0x4c, // b
 212         0xE012 // t
 213         };
 214         return s;
 215 }
 216 void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
 217 {
 218         uint8_t zeroes_32[] = {0,0,0,0};
 219         BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
 220         State initState = suc(k,init(k),&input);
 221         output(k,initState,&input_32_zeroes,&out);
 222 }
 223
 224 void doMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
 225 {
 226         uint8_t cc_nr[13] = { 0 };
 227     uint8_t div_key[8];
 228         //cc_nr=(uint8_t*)malloc(length+1);
 229
 230         memcpy(cc_nr,cc_nr_p,12);
 231     memcpy(div_key,div_key_p,8);
 232
 233         reverse_arraybytes(cc_nr,12);
 234         BitstreamIn bitstream = {cc_nr,12 * 8,0};
 235     uint8_t dest []= {0,0,0,0,0,0,0,0};
 236     BitstreamOut out = { dest, sizeof(dest)*8, 0 };
 237     MAC(div_key,bitstream, out);
 238     //The output MAC must also be reversed
 239     reverse_arraybytes(dest, sizeof(dest));
 240     memcpy(mac, dest, 4);
 241         //free(cc_nr);
 242     return;
 243 }
 244 #ifndef ON_DEVICE
 245 int testMAC()
 246 {
 247         prnlog("[+] Testing MAC calculation...");
 248
 249         //From the "dismantling.IClass" paper:
 250         uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
 251         //From the paper
 252         uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
 253         uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA};
 254
 255         uint8_t calculated_mac[4] = {0};
 256         doMAC(cc_nr,div_key, calculated_mac);
 257
 258         if(memcmp(calculated_mac, correct_MAC,4) == 0)
 259         {
 260                 prnlog("[+] MAC calculation OK!");
 261
 262         }else
 263         {
 264                 prnlog("[+] FAILED: MAC calculation failed:");
 265                 printarr("    Calculated_MAC", calculated_mac, 4);
 266                 printarr("    Correct_MAC   ", correct_MAC, 4);
 267                 return 1;
 268         }
 269
 270         return 0;
 271 }
 272 #endif