3b146b109b520fc05eec44c4d06aaffdfdee2205
[proxmark3-svn] / 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, 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 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 /**
83 * Similarly, the feedback function for the bottom register B : F 8/2 → F 2 is defined as
84 * B(x 0 x 1 . . . x 7 ) = x 1 ⊕ x 2 ⊕ x 3 ⊕ x 7 .
85 **/
86 bool B(State state)
87 {
88 bool x1 = state.b & 0x40;
89 bool x2 = state.b & 0x20;
90 bool x3 = state.b & 0x10;
91 bool x7 = state.b & 0x01;
92
93 return x1 ^ x2 ^ x3 ^ x7;
94
95 }
96
97
98 /**
99 * Definition 3 (Selection function). The selection function select : F 2 × F 2 ×
100 * F 8/2 → F 3/2 is defined as select(x, y, r) = z 0 z 1 z 2 where
101 * z 0 = (r 0 ∧ r 2 ) ⊕ (r 1 ∧ r 3 ) ⊕ (r 2 ∨ r 4 )
102 * z 1 = (r 0 ∨ r 2 ) ⊕ (r 5 ∨ r 7 ) ⊕ r 1 ⊕ r 6 ⊕ x ⊕ y
103 * z 2 = (r 3 ∧ r 5 ) ⊕ (r 4 ∧ r 6 ) ⊕ r 7 ⊕ x
104 **/
105 uint8_t _select(bool x, bool y, uint8_t r)
106 {
107 bool r0 = r >> 7 & 0x1;
108 bool r1 = r >> 6 & 0x1;
109 bool r2 = r >> 5 & 0x1;
110 bool r3 = r >> 4 & 0x1;
111 bool r4 = r >> 3 & 0x1;
112 bool r5 = r >> 2 & 0x1;
113 bool r6 = r >> 1 & 0x1;
114 bool r7 = r & 0x1;
115
116 bool z0 = (r0 & r2) ^ (r1 & !r3) ^ (r2 | r4);
117 bool z1 = (r0 | r2) ^ ( r5 | r7) ^ r1 ^ r6 ^ x ^ y;
118 bool z2 = (r3 & !r5) ^ (r4 & r6 ) ^ r7 ^ x;
119
120 // The three bitz z0.. z1 are packed into a uint8_t:
121 // 00000ZZZ
122 //Return value is a uint8_t
123 uint8_t retval = 0;
124 retval |= (z0 << 2) & 4;
125 retval |= (z1 << 1) & 2;
126 retval |= z2 & 1;
127
128 // Return value 0 <= retval <= 7
129 return retval;
130 }
131
132 /**
133 * Definition 4 (Successor state). Let s = l, r, t, b be a cipher state, k ∈ (F 82 ) 8
134 * be a key and y ∈ F 2 be the input bit. Then, the successor cipher state s ′ =
135 * l ′ , r ′ , t ′ , b ′ is defined as
136 * t ′ := (T (t) ⊕ r 0 ⊕ r 4 )t 0 . . . t 14 l ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l ⊞ r
137 * b ′ := (B(b) ⊕ r 7 )b 0 . . . b 6 r ′ := (k [select(T (t),y,r)] ⊕ b ′ ) ⊞ l
138 *
139 * @param s - state
140 * @param k - array containing 8 bytes
141 **/
142 State successor(uint8_t* k, State s, bool y)
143 {
144 bool r0 = s.r >> 7 & 0x1;
145 bool r4 = s.r >> 3 & 0x1;
146 bool r7 = s.r & 0x1;
147
148 State successor = {0,0,0,0};
149
150 successor.t = s.t >> 1;
151 successor.t |= (T(s) ^ r0 ^ r4) << 15;
152
153 successor.b = s.b >> 1;
154 successor.b |= (B(s) ^ r7) << 7;
155
156 bool Tt = T(s);
157
158 successor.l = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l+s.r ) & 0xFF;
159 successor.r = ((k[_select(Tt,y,s.r)] ^ successor.b) + s.l ) & 0xFF;
160
161 return successor;
162 }
163 /**
164 * We define the successor function suc which takes a key k ∈ (F 82 ) 8 , a state s and
165 * an input y ∈ F 2 and outputs the successor state s ′ . We overload the function suc
166 * to multiple bit input x ∈ F n 2 which we define as
167 * @param k - array containing 8 bytes
168 **/
169 State suc(uint8_t* k,State s, BitstreamIn *bitstream)
170 {
171 if(bitsLeft(bitstream) == 0)
172 {
173 return s;
174 }
175 bool lastbit = tailBit(bitstream);
176 return successor(k,suc(k,s,bitstream), lastbit);
177 }
178
179 /**
180 * Definition 5 (Output). Define the function output which takes an internal
181 * state s =< l, r, t, b > and returns the bit r 5 . We also define the function output
182 * on multiple bits input which takes a key k, a state s and an input x ∈ F n 2 as
183 * output(k, s, ǫ) = ǫ
184 * output(k, s, x 0 . . . x n ) = output(s) · output(k, s ′ , x 1 . . . x n )
185 * where s ′ = suc(k, s, x 0 ).
186 **/
187 void output(uint8_t* k,State s, BitstreamIn* in, BitstreamOut* out)
188 {
189 if(bitsLeft(in) == 0)
190 {
191 return;
192 }
193 pushBit(out,(s.r >> 2) & 1);
194 //Remove first bit
195 uint8_t x0 = headBit(in);
196 State ss = successor(k,s,x0);
197 output(k,ss,in, out);
198 }
199
200 /**
201 * Definition 6 (Initial state). Define the function init which takes as input a
202 * key k ∈ (F 82 ) 8 and outputs the initial cipher state s =< l, r, t, b >
203 **/
204
205 State init(uint8_t* k)
206 {
207 State s = {
208 ((k[0] ^ 0x4c) + 0xEC) & 0xFF,// l
209 ((k[0] ^ 0x4c) + 0x21) & 0xFF,// r
210 0x4c, // b
211 0xE012 // t
212 };
213 return s;
214 }
215 void MAC(uint8_t* k, BitstreamIn input, BitstreamOut out)
216 {
217 uint8_t zeroes_32[] = {0,0,0,0};
218 BitstreamIn input_32_zeroes = {zeroes_32,sizeof(zeroes_32)*8,0};
219 State initState = suc(k,init(k),&input);
220 output(k,initState,&input_32_zeroes,&out);
221 }
222
223 void doMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
224 {
225 uint8_t cc_nr[13] = { 0 };
226 uint8_t div_key[8];
227 //cc_nr=(uint8_t*)malloc(length+1);
228
229 memcpy(cc_nr, cc_nr_p, 12);
230 memcpy(div_key, div_key_p, 8);
231
232 reverse_arraybytes(cc_nr,12);
233 BitstreamIn bitstream = {cc_nr, 12 * 8, 0};
234 uint8_t dest []= {0,0,0,0,0,0,0,0};
235 BitstreamOut out = { dest, sizeof(dest)*8, 0 };
236 MAC(div_key,bitstream, out);
237 //The output MAC must also be reversed
238 reverse_arraybytes(dest, sizeof(dest));
239 memcpy(mac, dest, 4);
240 //free(cc_nr);
241 return;
242 }
243 void doMAC_N(uint8_t *address_data_p, uint8_t address_data_size, uint8_t *div_key_p, uint8_t mac[4])
244 {
245 uint8_t *address_data;
246 uint8_t div_key[8];
247 address_data = (uint8_t*) malloc(address_data_size);
248
249 memcpy(address_data, address_data_p, address_data_size);
250 memcpy(div_key, div_key_p, 8);
251
252 reverse_arraybytes(address_data, address_data_size);
253 BitstreamIn bitstream = {address_data, address_data_size * 8, 0};
254 uint8_t dest []= {0,0,0,0,0,0,0,0};
255 BitstreamOut out = { dest, sizeof(dest)*8, 0 };
256 MAC(div_key, bitstream, out);
257 //The output MAC must also be reversed
258 reverse_arraybytes(dest, sizeof(dest));
259 memcpy(mac, dest, 4);
260 free(address_data);
261 return;
262 }
263
264 #ifndef ON_DEVICE
265 int testMAC()
266 {
267 prnlog("[+] Testing MAC calculation...");
268
269 //From the "dismantling.IClass" paper:
270 uint8_t cc_nr[] = {0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0,0,0,0};
271 //From the paper
272 uint8_t div_key[8] = {0xE0,0x33,0xCA,0x41,0x9A,0xEE,0x43,0xF9};
273 uint8_t correct_MAC[4] = {0x1d,0x49,0xC9,0xDA};
274
275 uint8_t calculated_mac[4] = {0};
276 doMAC(cc_nr,div_key, calculated_mac);
277
278 if(memcmp(calculated_mac, correct_MAC,4) == 0)
279 {
280 prnlog("[+] MAC calculation OK!");
281
282 }else
283 {
284 prnlog("[+] FAILED: MAC calculation failed:");
285 printarr(" Calculated_MAC", calculated_mac, 4);
286 printarr(" Correct_MAC ", correct_MAC, 4);
287 return 1;
288 }
289
290 return 0;
291 }
292 #endif
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