client/src/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, or, at your option, any later version.
  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 #include "cipher.h"
  40 #include "cipherutils.h"
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <stdbool.h>
  44 #include <stdint.h>
  45 #ifndef ON_DEVICE
  46 #include "fileutils.h"
  47 #endif
  48
  49
  50 /**
  51 * Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
  52 * consisting of the following four components:
  53 *   1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
  54 *   2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
  55 *   3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
  56 *   4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
  57 **/
  58 typedef struct {
  59     uint8_t l;
  60     uint8_t r;
  61     uint8_t b;
  62     uint16_t t;
  63 } State;
  64
  65 /**
  66 *  Definition 2. The feedback function for the top register T : F 16/2 → F 2
  67 *  is defined as
  68 *  T (x 0 x 1 . . . . . . x 15 ) = x 0 ⊕ x 1 ⊕ x 5 ⊕ x 7 ⊕ x 10 ⊕ x 11 ⊕ x 14 ⊕ x 15 .
  69 **/
  70 static bool T(State state) {
  71     /*
  72         bool x0 = state.t & 0x8000;
  73         bool x1 = state.t & 0x4000;
  74         bool x5 = state.t & 0x0400;
  75         bool x7 = state.t & 0x0100;
  76         bool x10 = state.t & 0x0020;
  77         bool x11 = state.t & 0x0010;
  78         bool x14 = state.t & 0x0002;
  79         bool x15 = state.t & 0x0001;
  80         return x0 ^ x1 ^ x5 ^ x7 ^ x10 ^ x11 ^ x14 ^ x15;
  81     */
  82 #define  _x0  ((state.t & 0x8000) >> 15 )
  83 #define  _x1  ((state.t & 0x4000) >> 14 )
  84 #define  _x5  ((state.t & 0x0400) >> 10 )
  85 #define  _x7  ((state.t & 0x0100) >> 8 )
  86 #define  _x10 ((state.t & 0x0020) >> 5 )
  87 #define  _x11 ((state.t & 0x0010) >> 4 )
  88 #define  _x14 ((state.t & 0x0002) >> 1 )
  89 #define  _x15 (state.t & 0x0001)
  90     return (_x0) ^ (_x1) ^ (_x5) ^ (_x7) ^ (_x10) ^ (_x11) ^ (_x14) ^ (_x15);
  91 }
  92 /**
  93 *  Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
  94 *  B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
  95 **/
  96 /*static bool B(State state) {
  97     bool x1 = state.b & 0x40;
  98     bool x2 = state.b & 0x20;
  99     bool x3 = state.b & 0x10;
 100     bool x7 = state.b & 0x01;
 101     return x1 ^ x2 ^ x3 ^ x7;
 102 }
 103 */
 104 #define B(x) (((x.b & 0x40) >> 6)  ^ ((x.b & 0x20) >> 5) ^ ((x.b & 0x10) >> 4) ^ (x.b & 0x01))
 105
 106 //   12 3456
 107 // 0100 0000
 108
 109 /**
 110 *  Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
 111 *  F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
 112 *  z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
 113 *  z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
 114 *  z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
 115 **/
 116 static uint8_t _select(bool x, bool y, uint8_t r) {
 117 #define _r0 ((r >> 7) & 0x01)
 118 #define _r1 ((r >> 6) & 0x01)
 119 #define _r2 ((r >> 5) & 0x01)
 120 #define _r3 ((r >> 4) & 0x01)
 121 #define _r4 ((r >> 3) & 0x01)
 122 #define _r5 ((r >> 2) & 0x01)
 123 #define _r6 ((r >> 1) & 0x01)
 124 #define _r7 (r & 0x01)
 125
 126 #define _z0  ( (_r0 & _r2) ^ ( _r1 & (!_r3)) ^ (_r2 | _r4) )
 127 #define _z1  ( (_r0 | _r2) ^ ( _r5 | _r7) ^_r1 ^ _r6 ^ (x) ^ (y) )
 128 #define _z2  ( (_r3 & (!_r5)) ^ (_r4 & _r6) ^ _r7 ^ (x) )
 129
 130     /*
 131         uint8_t r0 = r >> 7 & 0x1;
 132         uint8_t r1 = r >> 6 & 0x1;
 133         uint8_t r2 = r >> 5 & 0x1;
 134         uint8_t r3 = r >> 4 & 0x1;
 135         uint8_t r4 = r >> 3 & 0x1;
 136         uint8_t r5 = r >> 2 & 0x1;
 137         uint8_t r6 = r >> 1 & 0x1;
 138         uint8_t r7 = r & 0x1;
 139
 140         bool z0 = (r0 & r2) ^ (r1 & (!r3)) ^ (r2 | r4);
 141         bool z1 = (r0 | r2) ^ (r5 | r7) ^ r1 ^ r6 ^ x ^ y;
 142         bool z2 = (r3 & (!r5)) ^ (r4 & r6) ^ r7 ^ x;
 143
 144         // The three bitz z0.. z1 are packed into a uint8_t:
 145         // 00000ZZZ
 146         //Return value is a uint8_t
 147         return ((z0 << 2) & 4) | ((z1 << 1) & 2) | (z2 & 1);
 148     */
 149     return ((_z0 << 2) & 4) | ((_z1 << 1) & 2) | (_z2 & 1);
 150
 151     /*
 152         uint8_t retval = 0;
 153         retval |= (z0 << 2) & 4;
 154         retval |= (z1 << 1) & 2;
 155         retval |= (z2) & 1;
 156
 157         // Return value 0 <= retval <= 7
 158         return retval;
 159     */
 160 }
 161
 162 /**
 163 *  Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
 164 *  be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
 165 *  l ′ , r ′ , t ′ , b ′ is defined as
 166 *  t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
 167 *  b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
 168 *
 169 * @param s - state
 170 * @param k - array containing 8 bytes
 171 **/
 172 static State successor(uint8_t *k, State s, bool y) {
 173     bool r0 = s.r >> 7 & 0x1;
 174     bool r4 = s.r >> 3 & 0x1;
 175     bool r7 = s.r & 0x1;
 176
 177     State successor = {0, 0, 0, 0};
 178
 179     successor.t = s.t >> 1;
 180     successor.t |= ((T(s)) ^ (r0) ^ (r4)) << 15;
 181
 182     successor.b = s.b >> 1;
 183     successor.b |= ((B(s)) ^ (r7)) << 7;
 184
 185     bool Tt = T(s);
 186
 187     successor.l = ((k[_select(Tt, y, s.r)] ^ successor.b) + s.l + s.r) & 0xFF;
 188     successor.r = ((k[_select(Tt, y, s.r)] ^ successor.b) + s.l) & 0xFF;
 189
 190     return successor;
 191 }
 192 /**
 193 *  We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
 194 *  an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
 195 *  to multiple bit input x ∈ F n 2 which we define as
 196 * @param k - array containing 8 bytes
 197 **/
 198 static State suc(uint8_t *k, State s, BitstreamIn *bitstream) {
 199     if (bitsLeft(bitstream) == 0) {
 200         return s;
 201     }
 202     bool lastbit = tailBit(bitstream);
 203     return successor(k, suc(k, s, bitstream), lastbit);
 204 }
 205
 206 /**
 207 *  Definition 5 (Output). Define the function output which takes an internal
 208 *  state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
 209 *  on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
 210 *  output(k, s, ǫ) = ǫ
 211 *  output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
 212 *  where s ′ = suc(k, s, x 0 ).
 213 **/
 214 static void output(uint8_t *k, State s, BitstreamIn *in,  BitstreamOut *out) {
 215     if (bitsLeft(in) == 0) {
 216         return;
 217     }
 218     pushBit(out, (s.r >> 2) & 1);
 219     //Remove first bit
 220     uint8_t x0 = headBit(in);
 221     State ss = successor(k, s, x0);
 222     output(k, ss, in, out);
 223 }
 224
 225 /**
 226 * Definition 6 (Initial state). Define the function init which takes as input a
 227 * key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
 228 **/
 229
 230 static State init(uint8_t *k) {
 231     State s = {
 232         ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
 233         ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
 234         0x4c, // b
 235         0xE012 // t
 236     };
 237     return s;
 238 }
 239
 240 static void MAC(uint8_t *k, BitstreamIn input, BitstreamOut out) {
 241     uint8_t zeroes_32[] = {0, 0, 0, 0};
 242     BitstreamIn input_32_zeroes = {zeroes_32, sizeof(zeroes_32) * 8, 0};
 243     State initState = suc(k, init(k), &input);
 244     output(k, initState, &input_32_zeroes, &out);
 245 }
 246
 247 void doMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4]) {
 248     uint8_t cc_nr[13] = { 0 };
 249     uint8_t div_key[8];
 250
 251     memcpy(cc_nr, cc_nr_p, 12);
 252     memcpy(div_key, div_key_p, 8);
 253
 254     reverse_arraybytes(cc_nr, 12);
 255     BitstreamIn bitstream = {cc_nr, 12 * 8, 0};
 256     uint8_t dest [] = {0, 0, 0, 0, 0, 0, 0, 0};
 257     BitstreamOut out = { dest, sizeof(dest) * 8, 0 };
 258     MAC(div_key, bitstream, out);
 259     //The output MAC must also be reversed
 260     reverse_arraybytes(dest, sizeof(dest));
 261     memcpy(mac, dest, 4);
 262 }
 263
 264 void doMAC_N(uint8_t *address_data_p, uint8_t address_data_size, uint8_t *div_key_p, uint8_t mac[4]) {
 265     uint8_t *address_data;
 266     uint8_t div_key[8];
 267     address_data = (uint8_t *) calloc(address_data_size, sizeof(uint8_t));
 268
 269     memcpy(address_data, address_data_p, address_data_size);
 270     memcpy(div_key, div_key_p, 8);
 271
 272     reverse_arraybytes(address_data, address_data_size);
 273     BitstreamIn bitstream = {address_data, address_data_size * 8, 0};
 274     uint8_t dest [] = {0, 0, 0, 0, 0, 0, 0, 0};
 275     BitstreamOut out = { dest, sizeof(dest) * 8, 0 };
 276     MAC(div_key, bitstream, out);
 277     //The output MAC must also be reversed
 278     reverse_arraybytes(dest, sizeof(dest));
 279     memcpy(mac, dest, 4);
 280     free(address_data);
 281 }
 282
 283 #ifndef ON_DEVICE
 284 int testMAC(void) {
 285     PrintAndLogEx(SUCCESS, "Testing MAC calculation...");
 286
 287     //From the "dismantling.IClass" paper:
 288     uint8_t cc_nr[] = {0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0, 0, 0, 0};
 289     //From the paper
 290     uint8_t div_key[8] = {0xE0, 0x33, 0xCA, 0x41, 0x9A, 0xEE, 0x43, 0xF9};
 291     uint8_t correct_MAC[4] = {0x1d, 0x49, 0xC9, 0xDA};
 292
 293     uint8_t calculated_mac[4] = {0};
 294     doMAC(cc_nr, div_key, calculated_mac);
 295
 296     if (memcmp(calculated_mac, correct_MAC, 4) == 0) {
 297         PrintAndLogEx(SUCCESS, "    MAC calculation (%s)", _GREEN_("ok"));
 298     } else {
 299         PrintAndLogEx(FAILED, "    MAC calculation (%s)", _RED_("failed"));
 300         printarr("    Calculated_MAC", calculated_mac, 4);
 301         printarr("    Correct_MAC   ", correct_MAC, 4);
 302         return PM3_ESOFT;
 303     }
 304     return PM3_SUCCESS;
 305 }
 306 #endif