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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 |