| 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 | void doMAC_N(uint8_t *address_data_p, uint8_t address_data_size, uint8_t *div_key_p, uint8_t mac[4]) |
| 245 | { |
| 246 | uint8_t *address_data; |
| 247 | uint8_t div_key[8]; |
| 248 | address_data = (uint8_t*) malloc(address_data_size); |
| 249 | |
| 250 | memcpy(address_data, address_data_p, address_data_size); |
| 251 | memcpy(div_key, div_key_p, 8); |
| 252 | |
| 253 | reverse_arraybytes(address_data, address_data_size); |
| 254 | BitstreamIn bitstream = {address_data, address_data_size * 8, 0}; |
| 255 | uint8_t dest []= {0,0,0,0,0,0,0,0}; |
| 256 | BitstreamOut out = { dest, sizeof(dest)*8, 0 }; |
| 257 | MAC(div_key, bitstream, out); |
| 258 | //The output MAC must also be reversed |
| 259 | reverse_arraybytes(dest, sizeof(dest)); |
| 260 | memcpy(mac, dest, 4); |
| 261 | free(address_data); |
| 262 | return; |
| 263 | } |
| 264 | |
| 265 | #ifndef ON_DEVICE |
| 266 | int testMAC() |
| 267 | { |
| 268 | prnlog("[+] Testing MAC calculation..."); |
| 269 | |
| 270 | //From the "dismantling.IClass" paper: |
| 271 | uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0}; |
| 272 | //From the paper |
| 273 | uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9}; |
| 274 | uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA}; |
| 275 | |
| 276 | uint8_t calculated_mac[4] = {0}; |
| 277 | doMAC(cc_nr,div_key, calculated_mac); |
| 278 | |
| 279 | if(memcmp(calculated_mac, correct_MAC,4) == 0) |
| 280 | { |
| 281 | prnlog("[+] MAC calculation OK!"); |
| 282 | |
| 283 | }else |
| 284 | { |
| 285 | prnlog("[+] FAILED: MAC calculation failed:"); |
| 286 | printarr(" Calculated_MAC", calculated_mac, 4); |
| 287 | printarr(" Correct_MAC ", correct_MAC, 4); |
| 288 | return 1; |
| 289 | } |
| 290 | |
| 291 | return 0; |
| 292 | } |
| 293 | #endif |